Large contributions of emission reductions and meteorological conditions to the abatement of PM2.5 in Beijing during the 24th Winter Olympic Games in 2022

To guarantee the blue skies for the 2022 Winter Olympics held in Beijing and Zhangjiakou from February 4 to 20, Beijing and its surrounding areas adopted a series of emission control measures. This provides an opportunity to determine the impacts of large-scale temporary control measures on the air quality in Beijing during this special period. Here, we applied the WRF-CMAQ model to quantify the contributions of emission reduction measures and meteorological conditions. Results show that meteorological conditions in 2022 decreased PM2.5 in Beijing by 6.9 and 11.8 µg/m3 relative to 2021 under the scenarios with and without emission reductions, respectively. Strict emission reduction measures implemented in Beijing and seven neighboring provinces resulted in an average decrease of 13.0 µg/m3 (-41.2%) in PM2.5 in Beijing. Over the entire period, local emission reductions contributed more to good air quality in Beijing than nonlocal emission reductions. Under the emission reduction scenario, local, controlled regions, other regions, and boundary conditions contributed 47.7%, 42.0%, 5.3%, and 5.0% to the PM2.5 concentrations in Beijing, respectively. The results indicate that during the cleaning period with the air masses from the northwest, the abatements of PM2.5 were mainly caused by local emission reductions. However, during the potential pollution period with the air masses from the east-northeast and west-southwest, the abatements of PM2.5 were caused by both local and nonlocal emission reductions almost equally. This implies that regional coordinated prevention and control strategies need to be arranged scientifically and rationally when heavy pollution events are forecasted.

Drivers of ammonia volatilization in Mediterranean climate cropping systems

Ammonia (NH3) volatilization is the major source of nitrogen (N) loss resulting from the application of synthetic and organic N fertilizers to croplands. It is well known that in Mediterranean cropping systems, there is a relationship between the intrinsic characteristics of the climate and nitrous oxide (N2O) emissions, but whether the same relation exists for NH3 emissions remains uncertain. Here, we estimated the impact of edaphoclimatic conditions (including meteorological conditions after N fertilization), crop management factors, and the measurement technique on both the cumulative emissions and the NH3 emission factor (EF) in Mediterranean climate zones, drawing on a database of 234 field treatments. We used a machine learning method, random forest (RF), to predict volatilization and ranked variables based on their importance in the prediction. Random forest had a good predictive power for the NH3 EF and cumulative emissions, with an R2 of 0.69 and 0.76, respectively. Nitrogen fertilization rate (N rate) was the top-ranked predictor variable, increasing NH3 emissions substantially when N rate was higher than 170 kg N ha-1. Soil pH was the most important edaphoclimatic variable, showing greater emissions (36.7 kg NH3 ha-1, EF = 19.3%) when pH was above 8.2. Crop type, fertilizer type, and N application method also affected NH3 emission patterns, while water management, mean precipitation, and soil texture were ranked low by the model. Our results show that intrinsic Mediterranean characteristics had only an indirect effect on NH3 emissions. For instance, relatively low N fertilization rates result in small NH3 emissions in rainfed areas, which occupy a very significant surface of Mediterranean agricultural land. Overall, N fertilization management is a key driver in reducing NH3 emissions, but additional field factors should be studied in future research to establish more robust abatement strategies.

Effects of meteorological conditions on brood care in cooperatively breeding carrion crow and consequences on reproductive success

Meteorological stressors (e.g., temperature and rain shortage) constrain brood provisioning in some bird species, but the consequences on reproductive success have been rarely quantified. Here we show, in a cooperatively breeding population of carrion crow Corvus corone in Spain, that individual feeding rates decreased significantly with rising air temperatures both in breeders and helpers, while lack of rain was associated with a significant reduction in the effort of the male helpers as compared to the other social categories. Group coordination, measured as the degree of alternation of nest visits by carers, was also negatively affected by rising temperature. Furthermore, we found that the body condition of the nestlings worsened when temperatures were high during the rearing period. Interestingly, the analysis of a long-term data set on crow reproduction showed that nestling body condition steadily deteriorated over the last 26-years. Although many factors may concur in causing population changes, our data suggest a possible causal link between global warming, brood caring behaviour and the decline of carrion crow population in the Mediterranean climatic region of Spain.

A multifaceted approach to explain short- and long-term PM2.5 concentration changes in Northeast Asia in the month of January during 2016-2021

Changes in PM_2.5 concentrations are influenced by interwoven impacts of key drivers (e.g., meteorology, local emissions, and regional emissions). However, it is challenging to quantitatively disentangle their impacts individually at once. Therefore, we introduced a multifaceted approach (i.e., meteorology vs. emissions and self-contribution vs. long-range transport) to analyze the effects of major drivers for long- and short-term PM_2.5 concentration changes based on observation and simulation in the month of January during 2016-2021 in Northeast Asia. For the simulations, we conducted modeling with the WRF-CMAQ system. The observed PM_2.5 concentrations in China and South Korea in January 2021 decreased by 13.7 and 9.8 μg/m³, respectively, compared to those in January 2016. Emission change was the dominant factor to reduce PM_2.5 concentrations in China (-115%) and South Korea (-74%) for the 6 years. However, the short-term changes in PM_2.5 concentrations between January of 2020-2021 were mainly driven by meteorological conditions in China (-73%) and South Korea (-68%). At the same time, in South Korea located in downwind area, the impact of long-range transport from upwind area (LTI) decreased by 55% (9.6 μg/m³) over the 6 years whereas the impact of local emissions increased (+2.9 μg/m³/year) during 2016-2019 but decreased (-4.5 μg/m³/year) during 2019-2021. Additionally, PM_2.5 concentrations in the upwind area showed a positive relationship with LTIs. However, for the days when westerly winds became weak in the downwind area, high PM_2.5 concentrations in upwind area did not lead to high LTIs. These results imply that the decline of PM_2.5 concentrations in South Korea was significantly affected by a combination of emission reduction in upwind area and meteorological conditions that hinder long-range transport. The proposed multifaceted approach can identify the main drivers of PM_2.5 concentration change in a region by considering the regional characteristics.

Background concentrations of airborne, culturable fungi and dust particles in urban, rural and mountain regions

Geographic location and meteorological factors can affect the content of bioaerosol concentrations. This study was conducted to determine the natural background concentrations of culturable fungal spores and dust particles in three different geographical areas. Focus was given to the dominant airborne genera Cladosporium, Penicillium, Aspergillus and the species Aspergillus fumigatus. The influence of weather conditions on the microorganism concentrations in urban, rural and mountain regions were examined. Possible correlations between particle counts and culturable fungal spore concentrations were investigated. 125 measurements of the air were conducted using the air sampler MAS-100NT® and the particle counter Alphasense OPC-N3. The analyses of the collected samples were based on culture methods using different media. The highest median of fungal spore concentrations was detected in the urban region and was of 2.0 × 10³ CFU/m³ for xerophilic fungi and 1.7 × 10³ CFU/m³ for the genus Cladosporium. The concentrations of fine and coarse particles in rural and urban regions were the highest of 1.9 × 10⁷ pa/m³ and 1.3 × 10⁷ pa/m³, respectively. Little cloud cover and slight wind had a positive influence on the concentration of fungal spores. Furthermore, correlations were observed between air temperature and the concentrations of xerophilic fungi as well as the genera Cladosporium. In contrast, relative humidity correlated negatively with total fungi and Cladosporium and no correlation was found with the other fungi. For the region of Styria in summer and early autumn, the natural background concentration for xerophilic fungi ranged between 3.5 × 10² and 4.7 × 10³ CFU/m³ air. No significant differences were detected between the fungal spore concentrations in urban, rural and mountainous regions. The data of this study could be used as a reference to compare the natural background concentrations of airborne culturable fungi in further studies concerning air quality assessment.

Characteristics and sources of carbonaceous aerosols in a semi-arid city: Quantifying anthropogenic and meteorological impacts

Carbonaceous aerosols have great adverse impacts on air quality, human health, and climate. However, there is a limited understanding of carbonaceous aerosols in semi-arid areas. The correlation between carbonaceous aerosols and control measures is still unclear owing to the insufficient information regarding meteorological contribution. To reveal the complex relationship between control measures and carbonaceous aerosols, offline and online observations of carbonaceous aerosols were conducted from October 8, 2019 to October 7, 2020 in Hohhot, a semi-arid city. The characteristics and sources of carbonaceous aerosols and impacts of anthropogenic emissions and meteorological conditions were studied. The annual mean concentrations (± standard deviation) of fine particulate matter (PM_2.5), organic carbon (OC), and elemental carbon (EC) were 42.81 (±40.13), 7.57 (±6.43), and 2.25 (±1.39) μg m^-3, respectively. The highest PM_2.5 and carbonaceous aerosol concentrations were observed in winter, whereas the lowest was observed in summer. The result indicated that coal combustion for heating had a critical role in air quality degradation in Hohhot. A boost regression tree model was applied to quantify the impacts of anthropogenic emissions and meteorological conditions on carbonaceous aerosols. The results suggested that the anthropogenic contributions of PM_2.5, OC, and EC during the COVID-19 lockdown period were 53.0, 15.0, and 2.36 μg m^-3, respectively, while the meteorological contributions were 5.38, 2.49, and -0.62 μg m^-3, respectively. Secondary formation caused by unfavorable meteorological conditions offset the emission reduction during the COVID-19 lockdown period. Coal combustion (46.4% for OC and 35.4% for EC) and vehicular emissions (32.0% for OC and 50.4% for EC) were the predominant contributors of carbonaceous aerosols. The result indicated that Hohhot must regulate coal use and vehicle emissions to reduce carbonaceous aerosol pollution. This study provides new insights and a comprehensive understanding of the complex relationships between control strategies, meteorological conditions, and air quality.

A new strategy for risk assessment of PM2.5-bound elements by considering the influence of wind regimes

For regulatory purposes, air pollution has been reduced to management of air quality control regions (AQCR), by inventorying pollution sources and identifying the receptors significantly affected. However, beyond being source-dependent, particulate matter can be physically and chemically altered by factors and elements of climate during transport, as they act as local environmental constraints, indirectly modulating the adverse effects of particles on the environment and human health. This case study, at an industrial site in a Brazilian coastal city - Joinville, combines different methodologies to integrate atmospheric dynamics in a strategic risk assessment approach whereby the influence of different wind regimes on environmental and health risks of exposure to PM_2.5-bound elements, are analysed. Although Joinville AQCR has been prone to stagnation/recirculation events, distinctly different horizontal wind circulation patterns indicate two airsheds within the region. The two sampling sites mirrored these two conditions and as a result we report different PM_2.5 mass concentrations, chemical profiles, geo-accumulation, and ecological and human health risks. In addition, feedback mechanisms between the airsheds seem to aggravate the air quality and its effects even under good ventilation conditions. Recognizably, the risks associated with Co, Pb, Cu, Ni, Mn, and Zn loadings were extremely high for the environment as well as being the main contributors to elevated non-carcinogenic risks. Meanwhile, higher carcinogenic risks occurred during stagnation/recirculation conditions, with Cr as the major threat. These results highlight the importance of integrating local airshed characteristics into the risk assessment of PM_2.5-bound elements since they can aggravate air pollution leading to different risks at a granular scale. This new approach to risk assessment can be employed in any city's longer-term development plan since it provides public authorities with a strategic perspective on incorporating environmental constraints into urban growth planning and development zoning regulations.

7Be, 210Pb, airborne particulate matter and PM10 concentrations in relation to meteorological conditions in southern Poland in 1998-2016

An analysis of the concentration of ⁷Be in aerosol samples collected in one of the most polluted areas in Europe (Katowice and Krakow in southern Poland) indicated seasonal variability, with a maximum in the summer months. The average concentrations of ⁷Be were 4616.1 μBq m^-3 in Katowice and 3259.4 μBq m^-3 in Krakow, respectively, and they are among the highest values recorded in Poland in the studied period (1998-2016). These cities are also characterised by Poland's highest concentrations of ²¹⁰Pb (547.8 μBq m^-3 and 513.2 μBq m^-3). The highest radioactive concentrations of ²¹⁰Pb were observed in the winter and autumn, since in the case of these industrial areas, the combustion processes related to heating in the cold season of the year are an additional source of this isotope, next to its natural origin. The airborne particulate matter concentrations at both locations correlate with the concentrations of ²¹⁰Pb. The average values of PM10 concentrations (71.1 μg m^-3 in Krakow to 45.0 μg m^-3 in Katowice), were 2-3 times higher than the average ones recorded in northern Poland. It has been proven that air temperature is the key parameter affecting the transport of isotopes, especially in the warm season of the year, when its increase causes increased thermal convection, leading to intense vertical mixing and exchange in the troposphere. Analyses using the machine learning method allowed for an indication of the correlation between relative humidity and atmospheric precipitation, as well as higher wind speed and concentrations of ⁷Be which is inversely proportional. Geographical factors (the latitude of the station and the land elevation) have no impact on near-surface concentrations of ⁷Be in Poland.

Impacts of meteorology and precursor emission change on O3 variation in Tianjin, China from 2015 to 2021

Deterioration of surface ozone (O₃) pollution in Northern China over the past few years received much attention. For many cities, it is still under debate whether the trend of surface O₃ variation is driven by meteorology or the change in precursors emissions. In this work, a time series decomposition method (Seasonal-Trend decomposition procedure based on Loess (STL)) and random forest (RF) algorithm were utilized to quantify the meteorological impacts on the recorded O₃ trend and identify the key meteorological factors affecting O₃ pollution in Tianjin, the biggest coastal port city in Northern China. After "removing" the meteorological fluctuations from the observed O₃ time series, we found that variation of O₃ in Tianjin was largely driven by the changes in precursors emissions. The meteorology was unfavorable for O₃ pollution in period of 2015-2016, and turned out to be favorable during 2017-2021. Specifically, meteorology contributed 9.3 µg/m³ O₃ (13%) in 2019, together with the increase in precursors emissions, making 2019 to be the worst year of O₃ pollution since 2015. Since then, the favorable effects of meteorology on O₃ pollution tended to be weaker. Temperature was the most important factor affecting O₃ level, followed by air humidity in O₃ pollution season. In the midday of summer days, O₃ pollution frequently exceeded the standard level (>160 µg/m³) at a combined condition with relative humidity in 40%-50% and temperature > 31°C. Both the temperature and the dryness of the atmosphere need to be subtly considered for summer O₃ forecasting.

Air pollution in heavy industrial cities along the northern slope of the Tianshan Mountains, Xinjiang: characteristics, meteorological influence, and sources

The spatiotemporal characteristics, relationship with meteorological factors, and source distribution of air pollutants (January 2017-December 2021) were analyzed to better understand the air pollutants on the northern slope of the Tianshan Mountains (NSTM) in Xinjiang, a heavily polluted urban agglomeration of heavy industries. The results showed that the annual mean concentrations of SO₂, NO₂, CO, O₃, PM_2.5, and PM₁₀ were 8.61-13.76 μg m^-3, 26.53-36.06 μg m^-3, 0.79-1.31 mg m^-3, 82.24-87.62 μg m^-3, 37.98-51.10 μg m^-3, and 84.15-97.47 μg m^-3. The concentrations of air pollutants (except O₃) showed a decreasing trend. The highest concentrations were in winter, and in Wujiaqu, Shihezi, Changji, Urumqi, and Turpan, the concentrations of particulate matter exceeded the NAAQS Grade II during winter. The west wind and the spread of local pollutants both substantially impacted the high concentrations. According to the analysis of the backward trajectory in winter, the air masses were mainly from eastern Kazakhstan and local emission sources, and PM₁₀ in the airflow had a more significant impact on Turpan; the rest of the cities were more affected by PM_2.5. Potential sources included Urumqi-Changj-Shihezi, Turpan, the northern Bayingol Mongolian Autonomous Prefecture, and eastern Kazakhstan. Consequently, the emphasis on improving air quality should be on reducing local emissions, strengthening regional cooperation, and researching transboundary transport of air pollutants.

Exploring the driving factors of haze events in Beijing during Chinese New Year holidays in 2020 and 2021 under the influence of COVID-19 pandemic

Unexpected outbreak of the 2019 novel coronavirus (COVID-19) has profoundly altered the way of human life and production activity, which posed visible impacts on PM_2.5 and its chemical species. The abruptly emergency reduction in human activities provided an opportunity to explore the synergetic impacts of multi-factors on shaping PM_2.5 pollution. Here, we conducted two comprehensive observation measurements of PM_2.5 and its chemical species from 1 January to 16 February in Beijing 2020 and the same lunar date in 2021, to investigate temporal variations and reveal the driving factors of haze before and after Chinese New Year (CNY). Results show that mean PM_2.5 concentrations during the whole observation were 63.83 and 66.86 μg/m³ in 2020 and 2021, respectively. Higher secondary inorganic species were observed after CNY, and K⁺, Cl^- showed three prominent peaks which associated closely with fireworks burnings from suburb Beijing and surroundings, verifying that they could be used as two representative tracers of fireworks. Further, we explored the impacts of meteorological conditions, regional transportation as well as chemical reactions on PM_2.5. We found that unfavorable meteorological conditions accounted for 11.0 % and 16.9 % of PM_2.5 during CNY holidays in 2020 and 2021, respectively. Regional transport from southwest and southeast (south) played an important role on PM_2.5 during the two observation periods. Higher ratio of NO₃^-/SO₄^2- were observed under high O_X and low RH conditions, suggesting the major pathway of NO₃^- and SO₄^2- formation could be photochemical process and aqueous-phase reaction. Additionally, nocturnal chemistry facilitated the formation of secondary components of both inorganic and organic. This study promotes understandings of PM_2.5 pollution in winter under the influence of COVID-19 pandemic and provides a well reference for haze and PM_2.5 control in future.

Does the meteorological origin of heat waves influence their impact on health? A 6-year morbidity and mortality study in Madrid (Spain)

BACKGROUND

In Spain, two synoptic-scale conditions influence heat wave formation. The first involves advection of warm and dry air masses carrying dust of Saharan origin (North African Dust (NAF) = 1). The second entails anticyclonic stagnation with high insolation and stability (NAF) = 0). Some studies show that the meteorological origin of these heat waves may affect their impact on morbidity and mortality.

OBJECTIVE

To determine whether the impact of heat waves on health outcomes in Madrid (Spain) during 2013-2018 varied by synoptic-scale condition.

METHODOLOGY

Outcome data consist of daily mortality and daily hospital emergency admissions (morbidity) for natural, circulatory, and respiratory causes. Predictors include daily maximum and minimum temperatures and daily mean concentrations of NO₂, PM₁₀, PM_2.5, NO₂, and O₃. Analyses adjust for insolation, relative humidity, and wind speed. Generalized linear models were performed with Poisson link between the variables controlling for trend, seasonality, and auto-regression in the series. Relative Risks (RR) and Attributable Risks (AR) were determined. The RRs for mortality attributable to high temperatures were similar regardless of NAF status. For hospital admissions, however, the RRs for hot days with NAF = 0 are higher than for days with NAF = 1. We also found that atmospheric pollutants worsen morbidity and mortality, especially PM₁₀ concentrations when NAF = 1 and O₃ concentrations when NAF = 0.

RESULTS

The effect of heat waves on morbidity and mortality depends on the synoptic situation. The impact is greater under anticyclonic stagnation conditions than under Saharan dust advection. Further, the health impact of pollutants such as PM₁₀ and O₃ varies according to the synoptic situation.

CONCLUSIONS

Based on these findings, we strongly recommend prevention plans to include data on the meteorological situation originating the heat wave, on a synoptic-scale, as well as comprehensive preventive measures against the compounding effect of high temperatures and pollution.

Interpretable machine learning approach to analyze the effects of landscape and meteorological factors on mosquito occurrences in Seoul, South Korea

Mosquitoes are the underlying cause of various public health and economic problems. In this study, patterns of mosquito occurrence were analyzed based on landscape and meteorological factors in the metropolitan city of Seoul. We evaluated the influence of environmental factors on mosquito occurrence through the interpretation of prediction models with a machine learning algorithm. Through hierarchical cluster analysis, the study areas were classified into waterside and non-waterside areas, according to the landscape patterns. The mosquito occurrence was higher in the waterside area, and mosquito abundance was negatively affected by rainfall at the waterside. The mosquito occurrence was predicted in each cluster area based on the landscape and cumulative meteorological variables using a random forest algorithm. Both models exhibited good performance (both accuracy and AUROC > 0.8) in predicting the level of mosquito occurrence. The embedded relationship between the mosquito occurrence and the environmental factors in the models was explained using the Shapley additive explanation method. According to the variable importance and the partial dependence plots for each model, the waterside area was more influenced by the meteorological and land cover variables than the non-waterside area. Therefore, mosquito control strategies should consider the effects of landscape and meteorological conditions, including the temperature, rainfall, and the landscape heterogeneity. The present findings can contribute to the development of mosquito forecasting systems in metropolitan cities for the promotion of public health.

Spatial patterns and temporal variations of pollutants at 56 air quality monitoring stations in the state of São Paulo, Brazil

This study applied two data mining tasks: clustering and association rules to a dataset of pollutants in the state of São Paulo. The clustering task was applied to temporal patterns and geospatial distributions of pollutants, and the association rules were used to identify prevailing meteorological conditions when there were high concentrations of pollutants from 2017 to 2019. The results indicated good adequacy of the cluster, indicating different pollution levels per group, with a silhouette coefficient from 0.26 to 0.72. In the spatial evaluation, the groups severely polluted were located in the metropolitan region, on the coast and, some inland cities, by industrial, vehicular, burning, agriculture, and other emissions. The cluster identified a strong presence of O₃ and PM_2.5 in 65% and 72% of the monitored stations in several areas of the state. As for the distance between the sources of pollution, the groups of PM₁₀ and NO₂ were geographically distant, while PM_2.5, CO, SO₂, and O₃ were closer, suggesting a spatial relationship of exposure. Seasonality was similar between groups, with significantly higher concentrations in winter, except for O₃, for which higher concentrations occurred in summer. Meteorological conditions contributed to critical episodes of pollution (support and confidence greater than 80%), with low temperature and humidity, low rainfall, and milder wind associated with increased pollutants. In conclusion, investigating spatial representativeness allows revealing spatial and temporal patterns of pollutants and unfavorable meteorological conditions to diffusion. Thus, ideal and effective measures can be taken to avoid critical periods of exposure based on the behavior of pollutants in different regions and related climate changes.

Spatiotemporal variations of PM2.5 pollution and its dynamic relationships with meteorological conditions in Beijing-Tianjin-Hebei region

Identifying the effects of meteorological conditions on PM_2.5 pollution is of great significance to explore methods to reduce atmospheric pollution. This study attempts to analyze the spatiotemporal variations of PM_2.5 pollution and its dynamic nexus with meteorological factors in the Beijing-Tianjin-Hebei (BTH) region from 2015 to 2020 using standard deviation ellipse (SDE) and panel vector autoregressive (PVAR) model. The results indicate that: (1) In 2015-2020, PM_2.5 pollution decreased significantly, indicating air pollution control policies in China have taken effect; Also, it showed a cumulative effect, or there was the path dependence of air pollution. (2) PM_2.5 pollution presented a distribution pattern from northeast to southwest, while the directionality of air pollution has weakened. Based on SDE, PM_2.5 pollution in Cangzhou can reflect the average level in the BTH; (3) Meteorological conditions exhibited a lagged and sustained effect on PM_2.5 pollution. Specifically, the effects of meteorological factors on PM_2.5 presented disequilibrium over time. In the long run, precipitation and temperature mainly showed negative impacts on PM_2.5 pollution, while wind speed, relative humidity and sunshine duration aggravated PM_2.5 pollution in the BTH. This study contributes to extending the study on the spatiotemporal evolution of PM_2.5 pollution and its links with meteorological conditions.

Be-7 and Pb-210 in fallout and aerosols in 2000-2016 in central Europe - Deposition velocity and dependence on meteorological parameters

The main aim of this research was to determine the transport and deposition velocities of ⁷Be and ²¹⁰Pb based on a vast database containing the results of measurements of ⁷Be and ²¹⁰Pb in fallout and aerosol samples carried out at several stations located throughout Poland in the period from 2000 to 2016. The monthly deposition flux of ⁷Be and ²¹⁰Pb showed an unequivocal downward trend but was also subject to seasonal changes, with maximum values in the summer period. The same patterns were found in the case of the deposition rate, the average values of which were 0.7 cm s^-1 for ⁷Be and 0.5 cm s^-1 for ²¹⁰Pb. A strong, statistically significant dependence of the deposition rate on the amount of dust was demonstrated, whereby a 10 μg m^-3 decrease in dust increases the ⁷Be deposition rate by 0.1 cm s^-1. Reduction of the concentration of carrier particles reduces the share of dry deposition in favour of precipitation convection, which is much more significant for the transport of both isotopes to the surface. Study of the effect of meteorological parameters showed that the concentrations of ⁷Be in fallout and aerosol samples and ²¹⁰Pb in fallout increase with increasing temperature, indicating a significant share of convection processes in isotope transport. The concentrations of ²¹⁰Pb in aerosols did not show any significant statistical changes over time. Their maximum values were observed in the winter period, indicating an additional source of this isotope related to combustion processes in the heating season. The studies confirmed the dominant role of convective precipitation and large-scale precipitation processes in the elution of ⁷Be from the atmosphere by showing the monthly deposition of this isotope to be strongly dependent on the total precipitation (r = 0.618).

Particle number size distribution and new particle formation in Xiamen, the coastal city of Southeast China in wintertime

New particle formation (NPF) has a great impact on regional and global climate, air quality and human health. This study uses a Scanning Mobility Particle Sizer (SMPS) for simultaneous measurement of particle number size distribution (PNSD) in wintertime to investigate NPF in the coastal city of Xiamen. The mean particle number concentration, surface area concentration and volume concentration were 7.25 × 10³ cm^-3, 152.54 μm² cm^-3, and 4.03 μm³ cm^-3, respectively. Particle number concentration was mainly influenced by the nucleation mode and the Aitken mode, whereas the main contributor to particle surface area concentration and volume concentration was accumulation mode particles. The frequency of NPF events occurred was around 41.4% in December 2019. The typical growth rates of new formed particles were 1.41-2.54 nm h^-1, and the observed formation rates were 0.49-1.43 cm^-3 s^-1. A comparative analysis of conditions between event and non-event days was performed. The results emphasized that air temperature, UV radiation and relative humidity were the most decisive meteorological factors, and NPF events usually occurred under clean atmospheric conditions with low PM concentrations. Although condensation sink was high when NPF event occurred, the level of SO₂ and O₃ concentration was also high.

Effect of meteorological conditions on leisure walking: a time series analysis and the application of outdoor thermal comfort indexes

Leisure walking is affected by meteorological conditions. However, it is still not clear what scales of meteorological conditions and thermal status affect the number of people who choose to leisure walk. Using a time series regression, this study examines the heat-leisure walking relationship by analyzing the effect of the seasons, weather, microclimate, and outdoor thermal comfort on walking count. Eight thermal indexes were selected to estimate the pedestrians' thermal comfort, and their predictive capacities in walking count were evaluated. Particular consideration was given to identifying heat thresholds of walking that determined the tolerance range of pedestrian heat stress. Four years of hourly daytime walking counts and publicly available ASOS meteorological data at Seoul-lo 7017, a pedestrian bridge in Seoul, were used for the analysis. Our findings indicate that walking count is correlated with seasonal climatic variations, with the highest number of pedestrians observed in fall and the lowest in summer. Moreover, air temperature played a vital role, showing that a 5.0 °C rise in temperature was associated with a 1.34% rise in the square root of the walking count. Its impact becomes greater when combined with intense solar radiation and higher absolute humidity. The heat threshold for walking was between 23.8 °C and 26.2 °C. Empirical model indexes showed the highest predictive capacity in walking count at approximately 30.0%, which was followed by rational model indexes at 28.0%.

The isotopic patterns and source apportionment of nitrate and ammonium in atmospheric aerosol

Nitrate (NO₃^-) and ammonium (NH₄⁺) are the major components in inorganic aerosol. However, their sources and formation processes remain unclear. This study conducted a year-round field measurement of TSP, PM_2.5 and PM_1.0 in five different sites in the Beijing-Tianjin-Hebei (BTH) region to determine the concentrations of water-soluble inorganic ions (WSIIs) and the isotopic compositions of inorganic nitrogen (δ¹⁵N-NH₄⁺, δ¹⁵N-NO₃^-, and δ¹⁸O-NO₃^-). The results showed the highest concentration of WSIIs in winter and lowest in summer. δ¹⁵N-NO₃^-, δ¹⁸O-NO₃^-, and δ¹⁵N-NH₄⁺ were in the range of -6.1-18.2, 52.2-103.8, and -28.7-36.2‰, respectively. The seasonal variations of δ¹⁵N-NO₃^- and δ¹⁵N-NH₄⁺ were an indication of relative contributions of the main sources and effects of meteorological conditions. The source apportionment identified fossil fuel combustion (38.2-50.6%), agricultural emissions (18-24.7%), biomass burning (16.3-22.7%), and road dust/soil (8.7-23.4%) were the main sources of inorganic aerosols. The local sources and regional migration contributed to the level of inorganic aerosol pollution. In winter, the aerosol in the BTH region was affected by the air mass from the northwest. While in spring and summer, the air mass was mainly from the South China. The low temperature and high relative humidity favored to the formation of inorganic nitrogen aerosol, and solar radiation affected the formation processes of inorganic aerosols by changing the oxidation pathway of NO₃^- and accelerating the volatilization and dissociation of ammonium nitrate (NH₄NO₃). This study discovered the main source contributions of inorganic nitrogen aerosol using N and O isotopes composition, and the obtained information has a great importance in understanding the effects of meteorological conditions on formation and the contribution of regional transport.

Exploring the impact of new particle formation events on PM2.5 pollution during winter in the Yangtze River Delta, China

New particle formation (NPF) events are an increasingly interesting topic in air quality and climate science. In this study, the particle number size distributions, and the frequency of NPF events over Hefei were investigated from November 2018 to February 2019. The proportions of the nucleation mode, Aitken mode, and accumulation mode were 24.59%, 53.10%, and 22.30%, respectively, which indicates the presence of abundant ultrafine particles in Hefei. Forty-six NPF events occurred during the observation days, accounting for 41.82% of the entire observation period. Moreover, the favorable meteorological conditions, potential precursor gases, and PM_2.5 range of the NPF events were analyzed. Compared to non-NPF days, the NPF events preferentially occurred on days with lower relative humidity, higher wind speeds, and higher temperatures. When the PM_2.5 was 15-20, 70-80, and 105-115 μg/m³, the frequency of the NPF events was higher. Nucleation mode particles were positively related to atmospheric oxidation indicated by ozone when PM_2.5 ranged from 15 to 20 μg/m³, and related to gaseous precursors like SO₂ and NO₂ when PM_2.5 was located at 70-80 and 105-115 μg/m³. On pollution days, NPF events did not directly contribute to the increase in the PM_2.5 in the daytime, however, NPF events would occur during the night and the growth of particulate matter contributes to the nighttime PM_2.5 contents. This could lead to pollution that lasted into the next day. These findings are significant to the improvement of our understanding of the effects of aerosols on air quality.

The influence of stagnant and transport types weather on heavy pollution in the Yangtze-Huaihe valley, China

The ambient atmospheric PM_2.5 concentrations in Anhui Province, China, which links the Yangtze River Delta region, China's fastest growing economy area, with the Beijing-Tianjin-Hebei (BTH) region, China's most polluted region, are influenced not only by local emissions, but also by changes in regional circulation. During the period 2013-2017, when China adopted a series of pollution abatement measures, there were still occasional pollution episodes with significant increases in PM_2.5 concentrations. PM_2.5 rise instead during the period 2013-2017 in Anhui (the Center of the Yangtze-Huaihe, YH), when pollution emissions continued to decrease? What is the controlling mechanism behind these? By analyzing elements such as ground-based PM_2.5 concentration and the planetary boundary layer (PBL) structure affecting it as well as larger scale circulation, combined with the analysis of a parameterized index, one can find that aerosol pollution in the YH region can usually be classified into three types. (1) There is a short-term transport stage (TS) in the initial stage of pollution, then as the pollutant concentrations increase, the PBL height decreases, the temperature inversion is gradually formed or strengthened, the wind speed decreases and the relative humidity of the lower layer increases, forming a two-way feedback mechanism in the cumulative stage (CS). (2) Pollutant concentrations will not drop rapidly in the later stage of CS, while a short-term TS will occur again. (3) The explosive rise (ER) events are mainly affected by transportation in the YH. The first of these types tends to be accompanied by the emergence and maintenance of heavy pollution periods (HPEs), and some phases is accompanied by explosive rises (ERs) in PM_2.5 that at least double in a short period of time. To sum up, deterioration of meteorological conditions explaining approximately 68% to the increase in PM_2.5 in the ER.

Model analysis of meteorology and emission impacts on springtime surface ozone in Shandong

Air quality observations showed that surface ozone (O₃) concentrations over Shandong increased significantly in springtime in recent years, especially 2017. The observed 90th percentile of hourly O₃ concentrations (O₃-h_90) in May increased from 148.4 μg/m³ in 2016 to 176.2 μg/m³ in 2017. To investigate the reasons of significant increase of O₃ in spring of 2017, seven sensitivity cases were performed with the RAMS-CMAQ modeling system to identify the impacts of meteorological conditions (M) and emissions (E) on O₃ concentrations in May of Shandong during the time period 2016-2018. The regional O₃-h_90 in May of Shandong were 103.0, 120.3 and 86.3 μg/m³ in 2016, 2017 and 2018, respectively. It was found that the positive effects from favorable meteorology were the dominant reasons that resulted in the high O₃ concentration in May 2017. When compared to 2017 standard simulation (17E17M), the differences of meteorological conditions led to the decrease of 17.5 and 33.8 μg/m³ in regional O₃-h_90 of May in 2016 (17E16M) and 2018(17E18M), while small changes (0.6 and - 0.3 μg/m³) appeared in that of May 2016 (16E17M) and 2018(18E17M) due to emission differences. Since there were few differences in the wind speeds of May between three years, the higher temperature and lower relative humidity significantly contributed to O₃ formation in May 2017 compared to May of 2016 and 2018. Besides, the amount of cloud fraction (CF), which has an indirect influence on the surface temperature and photochemical production of ozone by its impacts on the insolation, was the least in May 2017 compared to that in May 2016 and 2018 over Shandong. The distributions of changes in CF had obvious negative correlations with that of O₃ vertical column concentrations and temperature. Thus, the fewer cloud fraction may play a key role in O₃ formation of May 2017.

The role of emissions and meteorology in driving CO2 concentrations in urban areas

A multi-year dataset of measurements of CO₂ concentrations, eddy covariance fluxes, and meteorological parameters over the city centre of Florence (Italy) has been analysed to assess the role of anthropogenic emissions and meteorology in controlling urban CO₂ concentrations. The latter exhibited a negative correlation with air temperature, wind speed, solar radiation, and sensible heat flux and a positive one with relative humidity and emissions. A linear and an artificial neural network (ANN) model have been developed and validated for short-term modelling of 3-h CO₂ concentrations. The ANN model performed better, with mean bias of 0.58 ppm, root mean square error within 30 ppm, and r²=0.49. Data clustering through the self-organized maps allowed to disentangle the role played by emissions and meteorological parameters in influencing CO₂ concentrations. Sensitivity analysis of CO₂ concentrations revealed a primary role played by the meteorological parameters, particularly wind speed. These results highlighted that (i) emission reduction actions at local urban scale should be better tied to actual and expected meteorological conditions and (ii) those actions alone have limited effects (e.g. a 20% emission reduction would result in a 3% CO₂ concentrations reduction). For all these reasons, large-scale policies would be needed.

The effect of meteorological variables on spontaneous pneumothorax in two regions with different altitudes

Spontaneous pneumothorax (SP) is defined as the presence of free air inside the pleural space. Many studies have reported that meteorological variables may trigger SP, but the mechanism is unknown. The aim of this study was to compare the effects of meteorological variables on the development of SP in two regions with different altitudes. The study was conducted in the Çanakkale (2 m above sea level) and the Erzurum region (1758 m). A total of 494 patients with SP who presented to the hospitals of the two regions between January 2011 and December 2016 were included in the study. The meteorological variables used included ambient temperature, atmospheric pressure, relative humidity, precipitation amount, wind speed, and wind direction (as north and south). The total 2192 days were divided into two as days with and without an SP case presentation. A 4-day period prior to the day a case presented was compared with the other days without any cases to investigate the presence of any lagged effect. Statistical significance was accepted at p < 0.05. Comparison of these two regions showed a significant difference between them. The meteorological variables of the regions that affect SP development were found to be low mean minimum temperature, high daily temperature change, low precipitation, low wind speed and north winds for Erzurum, and only rainy days for Çanakkale. The results have demonstrated that cold weather, sudden temperature changes, north winds, and low wind speed are risk factors for the development of SP at high altitudes.

Correlations between 7Be, 210Pb, dust and PM10 concentrations in relation to meteorological conditions in northern Poland in 1998-2018

Analysis of a twenty-year (1998-2018) data series on ⁷Be concentrations in weekly collected aerosol samples in northern Poland showed a clear pattern of seasonal changes in ⁷Be with a maximum in the summer period associated with the most intensive thermal convection and vertical mixing. Activity concentrations of ⁷Be ranged from 480 μBq m^-3 to 9370 μBq m^-3. A strong relationship has been shown between ⁷Be concentrations observed in years and the activity of the Sun related to the sunspot number. Activity concentrations of ²¹⁰Pb in aerosol ranged from 17 μBq m^-3 to 1490 μBq m-3 with maximum occurring in the winter. The difference in the seasonal pattern in ⁷Be and ²¹⁰Pb concentrations were directly related to the different sources of both isotopes, as an additional source of ²¹⁰Pb was the products of combustion during the heating season. Similar pattern with maximum concentrations in winter was observed for PM10, as the main source is the same as in the case ²¹⁰Pb. A content of PM10 was in the range from 6.5 to 81.7 μg m^-3. A statistically significant correlation between both isotopes occurs. At the same time, ⁷Be, ²¹⁰Pb and PM10 are visibly related to the dust concentrations ranged from 7.3 μg m^-3 in winter to 134.8 μg m^-3 in spring. Statistical analysis carried out with simple regression model, stepwise multiple regression, and Random Forest models showed that the sunspots number, air temperature and sunshine duration have the most substantial impact on transport, and hence the concentration of ⁷Be in the surface layer of the atmosphere. The increase in relative humidity and precipitation and higher wind speed have a statistically significant effect on the reduction of ⁷Be concentrations in surface air.

Stable and transport indices applied to winter air pollution over the Yangtze River Delta, China

Previous studies have developed a stable weather index (SWI) based on meteorological elements that adequately represent PM_2.5 pollution over the North China Plain (NCP). However, the SWI performs poorly over the Yangtze River Delta (YRD) region because air pollution over this region is affected not only by stagnant weather (STAG) but also by transport (TRANS). For example, air pollutants can be transported from the NCP to the YRD by cold fronts. In this study, an obliquely rotated principal component analysis in the T-model is applied to classify the synoptic patterns of winter weather over the YRD region from 2013 to 2018. Among the four identified synoptic patterns, two of which cause TRANS, one pattern is most likely to cause STAG, and one pattern can lead to either STAG or TRANS depending on the location of high pressure around Shandong province. Due to the large contribution (63%) of TRANS to the total PM_2.5 pollution events, a transport pollution index (TPI) is constructed to describe the transport features of PM_2.5 pollution over the YRD region. Our results show that, when considering the SWI alone, the correlation coefficients between the SWI and ln(PM_2.5) range from 0.50 to 0.57 in the main cities of the YRD. Excitingly, when considering both the TPI and SWI (TPI+SWI), the correlation coefficients increase significantly to 0.63-0.78, suggesting that TPI+SWI better reflects the wintertime PM_2.5 pollution level over the YRD region. In addition, satisfactory performance in validation also suggests that TPI+SWI can increase the accuracy of evaluating and forecasting of PM_2.5 pollution episodes over regions downstream of source emissions.

Temporal characteristics of carbon dioxide and ozone over a rural-cropland area in the Yangtze River Delta of eastern China

In this study, rural atmospheric carbon dioxide (CO₂) and ozone (O₃) were measured from January 2015 to December 2018 to investigate characteristics of greenhouse gases in eastern China. Results showed that the annual average CO₂ (O₃) concentration in 2018 decreased by 2% (increased by 19%) when compared with that in 2015. CO₂ concentrations exhibited monthly variability, peaking in February (443.7 ppm) and reaching their lowest levels in July (363.0 ppm); whereas, monthly O₃ showed a bimodal pattern with peaks in June (51.3 ppb) and September (34.5 ppb). Regarding the diurnal variation, the maximum CO₂ (O₃) concentration occurred at nighttime (in the daytime) and a minimum CO₂ (O₃) in the daytime (at nighttime). As demonstrated by correlation analysis, CO₂ and O₃ variations were partly modulated by NOx and PM_2.5. Furthermore, CO₂ showed significant positive correlations with relative humidity in winter, while O₃ showed strong positive correlations with temperature in spring. CO₂ was accumulated from local sources under calm conditions (< 2 m s^-1) and derived from remote sources at high wind speeds (> 4 m s^-1), while O₃ concentrations were peaking at medium wind speeds of 2-4 m s^-1. CO₂ was found to derive from long-distance (short-distance transport) transport in spring (the other three seasons), whereas O₃ is mainly from long-distance (short-distance) transport in winter (the other three seasons). This work sheds light on the temporal characteristics of CO₂ and O₃, which has important implications for implementing practices to mitigate source emissions over cropland areas.

Examining geographical disparities in the incubation period of the COVID-19 infected cases in Shenzhen and Hefei, China

BACKGROUND

Current studies on the COVID-19 depicted a general incubation period distribution and did not examine whether the incubation period distribution varies across patients living in different geographical locations with varying environmental attributes. Profiling the incubation distributions geographically help to determine the appropriate quarantine duration for different regions.

METHODS

This retrospective study mainly applied big data analytics and methodology, using the publicly accessible clinical report for patients (n = 543) confirmed as infected in Shenzhen and Hefei, China. Based on 217 patients on whom the incubation period could be identified by the epidemiological method. Statistical and econometric methods were employed to investigate how the incubation distributions varied between infected cases reported in Shenzhen and Hefei.

RESULTS

The median incubation period of the COVID-19 for all the 217 infected patients was 8 days (95% CI 7 to 9), while median values were 9 days in Shenzhen and 4 days in Hefei. The incubation period probably has an inverse U-shaped association with the meteorological temperature. The warmer condition in the winter of Shenzhen, average environmental temperature between 10 °C to 15 °C, may decrease viral virulence and result in more extended incubation periods.

CONCLUSION

Case studies of the COVID-19 outbreak in Shenzhen and Hefei indicated that the incubation period of COVID-19 had exhibited evident geographical disparities, although the pathological causality between meteorological conditions and incubation period deserves further investigation. Methodologies based on big data released by local public health authorities are applicable for identifying incubation period and relevant epidemiological research.

The association between COVID-19 deaths and short-term ambient air pollution/meteorological condition exposure: a retrospective study from Wuhan, China

The emergence of coronavirus disease 2019 (COVID-19) has become a worldwide pandemic after its first outbreak in Wuhan, China. However, it remains unclear whether COVID-19 death is linked to ambient air pollutants or meteorological conditions. We collected the daily COVID-19 death number, air quality index (AQI), ambient air pollutant concentrations, and meteorological variables data of Wuhan between Jan 25 and April 7, 2020. The Pearson and Poisson regression models were used accordingly to understand the association between COVID-19 deaths and each risk factor. The daily COVID-19 deaths were positively correlated with AQI (slope = 0.4 ± 0.09, R ² = 0.24, p < 0.01). Detailedly, PM_2.5 was the only pollutant exhibiting a positive association (relative risk (RR) = 1.079, 95%CI 1.071-1.086, p < 0.01) with COVID-19 deaths. The PM₁₀, SO₂, and CO were all also significantly associated with COVID-19 deaths, but in negative pattern (p < 0.01). Among them, PM₁₀ and CO had the highest and lowest RR, which equaled to 0.952 (95%CI 0.945-0.959) and 0.177 (95%CI 0.131-0.24), respectively. Additionally, temperature was inversely associated with COVID-19 deaths (RR = 0.861, 95%CI 0.851-0.872, p < 0.01). Contrarily, diurnal temperature range was positively associated with COVID-19 deaths (RR = 1.014, 95%CI 1.003-1.025, p < 0.05). The data suggested that PM_2.5 and diurnal temperature range are tightly associated with increased COVID-19 deaths.

Measurements of sky brightness at Bosscha Observatory, Indonesia

To determine the level of light pollution due to human activities, we performed sky-brightness measurements at Bosscha Observatory, Indonesia (107°36′E; 6°49′S, 1300 m above sea level) for seven years from 2011 to 2018, using a portable photometer pointed at the zenith. From 1692 nightly records, we found that the average brightness on moonless nights reached the 19.70 ± 0.84 and 19.01 ± 0.88 astronomical magnitudes per square arcsecond (mpass), with median values of 19.73 mpass and 19.03 mpass for the AM and PM periods, respectively. The darkest skies occurred in the peak of the summer season during the month of July, which corresponds to the lowest annual temperature, precipitation, and relative humidity. The internal temperature of our Sky Quality Meter is adequately stable, and our results correlate well with other measurements. The sky brightness depends on the age of the Moon (days past new Moon) and on seasonal monthly variations, but it is not related to the lunar distance. The night-SB quality can be modified by the coupled climate system as a diurnal cycle to an 11-year solar cycle. The cities around the Observatory, Bandung and Lembang, clearly make strong contributions to light pollution in the area due to unshielded light sources.

An environmental and health perspective for COVID-19 outbreak: Meteorology and air quality influence, sewage epidemiology indicator, hospitals disinfection, drug therapies and recommendations

This Opinion Paper wishes to provide a summary of recent findings and solutions for a better understanding of the environmental and health problems associated with COVID-19. The list of topics covered is large: meteorology and air quality factors with correlation number of infections, sewage waters as a way to reveal the scale of COVID-19 outbreak, current hospital disinfection procedures and new eco-friendly technologies and list of drug therapies recommend waiting for the desired vaccine to come. During the last two months we did notice an increase in the scientific literature regarding COVID-19 with a partial vision of this problem. The current Opinion Paper is one of the first attempts, to my understanding, to summarize and integrate environmental and human health aspects related to the monitoring, fate and treatment solutions for COVID-19. That being said I believe that this Opinion Paper can serve as multipurpose document, not only for scientists of different disciplines but for social media and citizens in general.

An environmental and health perspective for COVID-19 outbreak: Meteorology and air quality influence, sewage epidemiology indicator, hospitals disinfection, drug therapies and recommendations

This Opinion Paper wishes to provide a summary of recent findings and solutions for a better understanding of the environmental and health problems associated with COVID-19. The list of topics covered is large: meteorology and air quality factors with correlation number of infections, sewage waters as a way to reveal the scale of COVID-19 outbreak, current hospital disinfection procedures and new eco-friendly technologies and list of drug therapies recommend waiting for the desired vaccine to come. During the last two months we did notice an increase in the scientific literature regarding COVID-19 with a partial vision of this problem. The current Opinion Paper is one of the first attempts, to my understanding, to summarize and integrate environmental and human health aspects related to the monitoring, fate and treatment solutions for COVID-19. That being said I believe that this Opinion Paper can serve as multipurpose document, not only for scientists of different disciplines but for social media and citizens in general.

Pollution characteristics of bioaerosols in PM2.5 during the winter heating season in a coastal city of northern China

Frequent heavy air pollution occurred during the winter heating season of northern China. In this study, PM_2.5 (particles with an aerodynamic diameter less than 2.5 μm) was collected from a coastal city of China during the winter heating season from January 1 to March 31, 2018, and the soluble ions, organic carbon (OC), elemental carbon (EC), bacterial, endotoxin, and fungal concentration in PM_2.5 were analyzed. During the winter heating season, PM_2.5 and bioaerosols increased on polluted days, and the secondary inorganic ions, including NO₃^-, NH₄⁺, and SO₄^2-, increased significantly. Meteorological factors, such as wind direction and wind speed, had major impacts on the distributions of PM_2.5 and bioaerosols. Pollutant concentration was high when there was a westerly wind with the speed of 3-6 m/s from inland area. Using the air mass backward trajectories and principal component analysis, we elucidate the potential origins of bioaerosol in PM_2.5. The backward trajectory suggested that air mass for polluted samples (PM_2.5 > 75 μg/m³) commonly originated from continent (9.62%), whereas air masses for clean samples (PM_2.5 < 35 μg/m³) were mainly from marine (56.73%). The interregional transport of pollutants from continental area contributed most to PM_2.5. Principal component analysis of the water-soluble ions and bioaerosol indicated that air pollution of the coastal city was greatly affected by coal combustion, biomass burning, and regional transmission of high-intensity pollutants from continent. Among that, interregional transport, biomass burning, and dust from soil and plants were main sources of bioaerosol. Our findings provide important insights into the origins and characteristics of bioaerosol in PM_2.5 during the winter heating season of the coastal city in northern China.

Effect of aerosols on the macro- and micro-physical properties of warm clouds in the Beijing-Tianjin-Hebei region

The interaction between aerosols and clouds plays an important role in the climate system. There is still uncertainty about the influences of aerosols on the macro- and micro-physical properties of clouds in the Beijing-Tianjin-Hebei region. The relationships between aerosol optical depth (AOD) and the macro- and micro-physical properties of warm clouds in the Beijing-Tianjin-Hebei region were analyzed based on MODIS/Aqua data from 2007 to 2016. In addition, the ERA-Interim meteorological data was employed to investigate the relationship of AOD and cloud parameters under different meteorological conditions. The results showed that the variation of cloud droplet effective radius (CER) with AOD was in agreement with the Anti-Twomey effect, the main reason was that the increasing aerosol causes the water vapor competition effect among the cloud droplets, which makes the smaller cloud droplets evaporate. The multi-year average AOD was positively correlated with liquid water path (LWP). The relationship between AOD and cloud optical depth (COD) was quite different. When AOD was <0.4 or >0.8, COD increased with the increase of AOD, and when AOD was between 0.4 and 0.8, AOD and COD showed negative correlation. With the increment of AOD, cloud top pressure (CTP) also increased, which indicated that cloud top height decreased. When AOD was <0.3, cloud fraction (CF) was negatively correlated with AOD and conversely, positively correlated when AOD was >0.3. Furthermore, under most meteorological conditions, AOD was positively correlated with cloud macro- and micro-physical properties. Under the conditions of relative humidity ranged from 40% to 80%, there was a negative correlation between AOD and COD.

Meteorological mechanism for a large-scale persistent severe ozone pollution event over eastern China in 2017

An intensive and persistent regional ozone pollution event occurred over eastern China from 25 June to 5 July 2017. 73 out of 96 selected cities, most located in the Beijing-Tianjin-Hebei and the surrounding area (BTHS), suffered severe ozone pollution. A north-south contrast ozone distribution, with higher ozone (199 ± 33 μg/m³) in the BTHS and lower ozone (118 ± 25 μg/m³) in the Yangtze River Delta (YRD), was found to be dominated by the position of the West Pacific Subtropical High (WPSH) and mid-high latitude wave activities. In the BTHS, the positive anomalies of geopotential height at 500 hPa and temperature at the surface indicated favorable meteorological conditions for local ozone formation. Prevailing northwesterly winds in the mid-high troposphere and warm advection induced by weak southerly winds in the low troposphere resulted in low-moderate relative humidity (RH), less total cloud cover (TCC), strong solar radiation and high temperatures. Moreover, southerly winds prevailing over the BTHS aggravated the pollution due to regional transportation of O₃ and its precursors. On one hand, the deep sinking motion and inversion layer suppressed the dispersion of pollutants. On the other hand, O₃-rich air in the upper layer was maintained at night due to temperature inversion, which facilitated O₃ vertical transport to the surface in the next-day morning due to elevated convection. Generally, temperature, UV radiation, and RH showed good correlations with O₃ in the BTHS, with rates of 8.51 (μg/m³)/°C (within the temperature range of 20-38°C), 59.54 (μg/m³)/(MJ/m²) and -1.93 (μg/m³)/%, respectively.

Evaluating the contributions of changed meteorological conditions and emission to substantial reductions of PM2.5 concentration from winter 2016 to 2017 in Central and Eastern China

The monthly average PM_2.5 concentration decreased from 127.15 μg m^-3 in December 2016 to 85.54 μg m^-3 in December 2017 (approximately 33%) in Central and Eastern China (33°N-41°N, 113°E-118°E). This decrease is attributed to the combined impacts of meteorology and emission sources changes, though the question of which is more important has raised great concerns. Four sensitivity experiments based on the Global-Regional Assimilation and Prediction System coupled with the Chinese Unified Atmospheric Chemistry Environment (GRAPES-CUACE) model, together with comparative analysis of the observed meteorological conditions and emission inventory between 2016 and 2017, are used to evaluate the relative contributions of meteorology and emission to the substantial reductions of PM_2.5 concentration from December 2016 to December 2017. The results show that the meteorological conditions and emission in December 2017 were both beneficial to the PM_2.5 decrease in Central and Eastern China. Regarding the entire region, 21.9% of the PM_2.5 decrease was a result of the favorable meteorological conditions, and 78.1% of the decrease was a result of emission reductions, showing the distinct contributions of emission reductions on the air quality. The relative contributions of meteorology varied from 12.2% to 50.9% to the PM_2.5 decrease from December 2016 to December 2017, while the emission contributed 49.1% to 87.8%, in different cities depending on geographical location and topography. Meteorology showed the largest contributions to the PM_2.5 decrease from 2016 to 2017 in Beijing (BJ), which caused the greatest total decrease of PM_2.5 compared to that of other cities. In addition, in Central and Eastern China, the dominant factors of the decrease of PM_2.5 were favorable meteorological conditions (accounting for 98.2%) during clear periods and emission reductions (accounting for 72.5-81.2%) during pollution periods.

Meteorological phenomenon as a key factor controlling variability of labile particulate mercury in rivers and its inflow into coastal zone of the sea

Mercury (Hg) is recognized as a global pollutant, which can be transported to the sea by suspended particulate matter (SPM) via rivers constituting the main source of mercury in the southern Baltic sea. The aim of the present study was to characterize the mercury fractions in suspended particulate matter, as well as the transformations of Hg during its riverine transportation into the sea. The thermo-desorption method was used to determine the labile and stable mercury fractions in SPM of rivers (Reda, Zagórska Struga, Gizdepka, Płutnica) within the Baltic Sea basin. In this paper six "periods" were designated (heating, non-heating, drought, rains, downpour/flood and thaws), during which the river suspended particulate matter was enriched with various fractions of mercury. Meteorological and hydrological phenomena such as downpours and thaws intensified surface runoff, causing an increase in the share of Hg_abs and Hg_ads1 mercury fractions in suspended particulate matter. Whereas, droughts contributed to the formation of HgS in a large river and to an inflow of adsorbed Hg in smaller rivers decrease of air temperature leads to increase of fossil fuel combustion and then increases the share of adsorbed Hg (mainly bound with halides) in riverine particulate matter. In the non-heating season, the main fraction was the mercury absorbed inside organic matter.

Mini-review of microplastics in the atmosphere and their risks to humans

Studies of microplastics (MPs) have highlighted their ubiquity in various environments. Recently, microplastics have been observed in atmospheric fallout collected from some cities. Although the studies are limited, some researches have shown that synthetic textiles are main source of airborne microplastics, and fibers are the dominant shape of microplastics in the atmosphere. Due to their small size, airborne microplastics can be directly inhaled posing health risks to humans, particularly to industry workers. Meteorological conditions and human activities affect the distribution and deposition of airborne microplastics. Furthermore, airborne microplastics are contributors to microplastic pollution in aquatic environments. We summarized the current knowledge and provide insights into further research to better understand airborne microplastics and their risks to human.

Paramyxoviruses respiratory syncytial virus, parainfluenza virus, and human metapneumovirus infection in pediatric hospitalized patients and climate correlation in a subtropical region of southern China: a 7-year survey

To investigate the features of paramyxovirus respiratory syncytial virus (RSV), parainfluenza virus (PIV), and human metapneumovirus (HMPV) infection and determine the effect of meteorological conditions in Guangzhou, a subtropical region of southern China. We collected 11,398 respiratory samples from hospitalized pediatric patients with acute respiratory illness between July 2009 and June 2016 in Guangzhou. The samples were tested simultaneously for 18 respiratory pathogens using real-time PCR. Local meteorological data were also collected for correlation analysis. Of 11,398 patients tested, 5606 (49.2%) patients tested positive for one or more pathogens; RSV, PIV, and HMPV were the first, sixth, and ninth most frequently detected pathogens, in 1690 (14.8%), 502 (4.4%), and 321 (2.8%) patients, respectively. A total 17.9% (4605/5606) of patients with positive results had coinfection with other pathogens. Significant differences were found in the prevalence of RSV, PIV, and HMPV among all age groups (p < 0.001). RSV and HMPV had similar seasonal patterns, with two prevalence peaks every year. PIV appeared alternatively with RSV and HMPV. Multiple linear regression models were established for RSV, PIV, and HMPV prevalence and meteorological factors (p < 0.05). RSV and PIV incidence was negatively correlated with monthly mean relative humidity; RSV and HMPV incidence was negatively correlated with sunshine duration; PIV incidence was positively correlated with mean temperature. We described the features of paramyxovirus infection in a subtropical region of China and highlighted the correlation with meteorological factors. These findings will assist public health authorities and clinicians in improving strategies for controlling paramyxovirus infection.

Temporal changes in the content of labile and stabile mercury forms in soil and their inflow to the southern Baltic Sea

Rivers represent the main source of mercury (Hg) in the Southern Baltic. Nevertheless, the concentration and proportion of individual Hg forms in rivers depend on the management of the river basin, as well as on the intensity of meteorological phenomena. Hence the aim of the present study was to determine the influence of drought and rains/intense rains on the content of labile and stable Hg forms in the soil of river catchments with various types of land management, and on the inflow of bioavailable mercury to the coastal zone of the sea. Soil and sediment samples were taken from two rivers flowing into Puck Bay (Southern Baltic): the Reda and Gizdepka. In order to determine Hg concentration and the proportions of its particular forms in the collected material, the thermo-desorption method was used. Five periods were identified during which the soil was enriched with various Hg forms. The obtained results showed that in periods of intensive development of vegetation, the soil becomes enriched with absorbed mercury (Hg_abs). On the other hand, as a result of Hg emissions during the heating of buildings, mercury associated with halides (Hg_ads1) is deposited on land, as was primarily recorded in catchments where individual household furnaces were found. Both mild and intense rainfalls intensified the surface run-off, which contributed to soil erosion, causing the transport of both Hg_abs and Hg_ads1 to the river bed. However, the soil was more enriched with labile mercury in anthropogenic catchments, as they are only slightly overgrown with vegetation, the presence of which limits soil erosion. During periods of snow melting, there was intensive leaching and transportation of Hg_ads1, which had been deposited on the land surface during the intensive combustion of fossil fuels. In each of the designated periods, stable mercury sulphide was formed in the soil. However, the highest proportion of HgS was found during a period of drought, when organic matter decomposed and there was inflow of sulphur compounds from farms. Taking into consideration the anomalous study periods, the largest load of mercury introduced along with the bed sediment of the Gizdepka into the sea was recorded during downpour/flood. Nevertheless, the most bioavailable Hg-enriched load was introduced during snow melting period.

Meteorological and chemical impacts on PM2.5 during a haze episode in a heavily polluted basin city of eastern China

Haze formation involves many interacting factors, such as secondary aerosol formation, unfavourable synoptic conditions and regional transport. The interaction between these factors complicates scientific understanding of the mechanism behind haze formation. In this study, we investigated the factors resulting in haze events in Longyou, a city located in a basin in China. Aerosol samples of PM_2.5 were collected for subsequent chemical composition analysis between 11 January and 5 February 2018. The impacts of wind on PM_2.5, SO₂ and NO₂ concentrations were analysed. Besides, the origin of air parcels and potential sources of PM_2.5 were analysed by backward trajectory, potential source contribution function (PSCF) and concentration-weighted trajectories (CWT). Among the water-soluble ions identified, NO₃^- had the highest concentration, with further analysis demonstrating the haze evolution was mainly driven by the reactions involving NO₃^- formation. The dramatic increase of nitrate is mainly due to the homogeneous reaction of nitric acid with ammonia, while sulfate is likely due to heterogeneous reactions of NO₂, SO₂ and NH₃. The average wind speed was less than 2 m/s during the aerosol sampling period, which could be considered as a stagnant state. Pollutants emitted by industrial area located in the northeast Longyou were probably brought to observation sites by continuous wind from northeast and accumulated gradually. Air parcels originating from the northeast of Zhejiang province also had large effects on haze pollution in Longyou. Together, our results showed that rapid secondary aerosol formation and unfavourable synoptic conditions are the main factors resulting in haze pollution in Longyou.

Warm Front Passage on the Previous Day Increased Ischemic Stroke Events

BACKGROUND AND PURPOSE

The influence of a weather front passage is rarely evaluated on stroke events. We hypothesized that a weather front passage on the stroke onset day or during the previous days may play an important role in the incidence of stroke.

METHODS

A multicenter retrospective study was conducted to evaluate the frequency of stroke events and their interaction with weather front passages. Consecutive acute stroke patients (n = 3935, 73.5 ± 12.4 years, 1610 females) who were admitted to 7 stroke hospitals in 3 cities from January 2012 to December 2013 were enrolled in this study. Multivariate Poisson regression models involving time lag variables were used to compare the daily rates of stroke events with the day of a weather front passage and the previous 6 days, adjusting for considerable influences of ambient temperature and atmospheric pressure.

RESULTS

There were a total of 33 cold fronts and 13 warm fronts that passed over the 3 cities during the study period. The frequency of ischemic stroke significantly increased when a warm front passed on the previous day (risk ratio 1.34, 95% confidence interval 1.07-1.69, P= .016).

CONCLUSIONS

This study indicated that a weather front passage on the previous days may be associated with the occurrence of stroke.

A study of the protective actions for a hypothetical accident of the Bushehr nuclear power plant at different meteorological conditions

In this work, protective actions have been studied assuming a hypothetical severe accident of the Bushehr nuclear power plant at different meteorological conditions. Simulations of the atmospheric dispersion of accidental airborne releases were performed using the RASCAL code. Total effective dose equivalent (TEDE) and thyroid dose received by members of the public living within a radius of 40 km around the reactor site were calculated for various atmospheric stability classes and weather conditions. According to the results of the dose assessment and by following the protective action guide of the Environmental Protection Agency (EPA), the critical zone and appropriate protective actions were determined depending on various metrological conditions. It was found that, for atmospheric stability class F and calm weather conditions, the maximum distance from the site of release for which TEDE is greater than the corresponding dose limit and for which sheltering or evacuation response actions are required, is 11 km. For the same weather conditions, the corresponding maximum distance for which iodine prophylaxis is required is 32 km. Based on the present simulations, it can be concluded that the metrological condition has a great influence on the radionuclide atmospheric dispersion and, consequently, on the critical zone where protective actions are required after the assumed accident condition.

Relationship between CO2 emissions and soil properties of differently tilled soils

Different tillage technologies have different effects on CO₂ emissions from soil. Unfortunately, little information exists about the impact of different types of tillage as compared with no-tillage, and the main controls. The aim of this research is to determine the relationship between physicomechanical, chemical and biological properties of soil and CO₂ emissions from differently tilled soils under the climatic conditions of central Lithuania before and after autumn tillage. The studies were conducted in 2009-2012 and 2014 at the Experimental Station of Aleksandras Stulginskis University in Central Lithuania. Different tillage technologies were applied: deep ploughing at 23-25 cm depth (DP); shallow ploughing at 12-15 cm depth (SP); deep cultivation with a cultivator at 25-27 cm depth (DC); shallow cultivation with a disc harrow at 12-15 cm depth (SC); and no-tillage (NT). The correlation of physicomechanical, chemical and biological soil properties with CO₂ emissions was determined. During all the experimental period total CO₂ emissions from soil in DP, SP, DC, SC and NT technologies were respectively 6.05, 4.25, 4.97, 4.42, 3.94 μmol m^-2 s^-1 before autumn soil tillage and 29.88, 22.50, 16.73, 13.72, 10.00 μmol m^-2 s^-1 after autumn tillage. Negative correlation between soil temperature and CO₂ emissions before the autumn tillage from soil was evidenced (r = -0.98). A strong negative correlation between soil respiration and total soil porosity was observed. Correlation between aeration soil porosity and CO₂ emissions was strong. After autumn tillage, the strongest correlations were found between soil penetration resistance and respiration in the upper (r = -0.75) and deeper (r = -0.71) layers. In autumn, a significant strong correlation (r = 0.78) between soil respiration and aeration porosity was obtained in the upper soil layer under ploughing or cultivation. This study revealed that CO₂ emissions were significantly higher immediately after autumn ploughing technologies compared to deep and shallow cultivation and no-tillage.

The effect of natural and anthropogenic factors on PM2.5: Empirical evidence from Chinese cities with different income levels

The aim of this paper is to estimate the effects of natural conditions and anthropogenic factors on PM_2.5 concentrations, taking into consideration differences in the income levels, and thus the development stages, of the cities studied. To achieve this goal, a balanced dataset of 287 Chinese cities was divided into different income-based panels for the period 1998-2015. The empirical estimation results indicated that meteorological conditions exerted varied effects on PM_2.5 concentrations across different income-based panels. The results show that the coefficients of temperature were positive and significant in all panels, with the exception of upper-middle-income cities. Whilst wind speed and precipitation were found to be conducive to reducing PM_2.5 concentrations, no such significant correlation was found in relation to relative humidity (except in high-income cities). In terms of the anthropogenic factors addressed in the study, we found an inverted U-shaped relationship between economic development and PM_2.5 concentrations, confirming the Environmental Kuznets Curve hypothesis. In addition, the industrial structure and road density were observed to exert significant positive impacts on PM_2.5 concentrations. The empirical analysis of the effects of FDI on PM_2.5 concentrations indicate that FDI aggravated PM_2.5 pollutions in the total cities and lower-middle-income cities panels, supporting the Pollution Haven Hypothesis. The empirical results for population density suggested that it does not significantly influence PM_2.5 concentrations. Moreover, we found that built-up area exerts mixed effects on PM_2.5 concentrations. These results cast a new light on the issue of PM_2.5 pollution for government policy makers tasked with formulating measures to mitigate the concentration of such pollutants, encouraging that consideration be given to the differences between cities with different income levels.

A random forest partition model for predicting NO2 concentrations from traffic flow and meteorological conditions

High concentrations of nitrogen dioxide in the air, particularly in heavily urbanised areas, have an adverse effect on many aspects of residents' health (short-term and long-term damage, unpleasant odour and other). A method is proposed for modelling atmospheric NO₂ concentrations in a conurbation, using a partition model M consisting of two separate models: M_L for lower concentration values and M_U for upper values. An advanced data mining technique, that of random forests, is used. This is a method based on machine learning, involving the simultaneous compilation of information from multiple random trees. Using the example of data recorded in Wrocław (Poland) in 2015-2017, an iterative method was applied to determine the boundary concentration y˜ for which the mean absolute deviation error for the partition model attained its lowest value. The resulting model had an R² value of 0.82, compared with 0.60 for a classical random forest model. The importances of the variables in the model M_L, similarly as in the classical case, indicate that the greatest influence on NO₂ concentrations comes from traffic flow, followed by meteorological factors, in particular the wind direction and speed. In the model M_U the importances of the variables are significantly different: while traffic flow still has the greatest impact, the effects of temperature and relative humidity are almost as great. This confirms the justifiability of constructing separate models for low and high pollution concentrations.

A random forest partition model for predicting NO2 concentrations from traffic flow and meteorological conditions

High concentrations of nitrogen dioxide in the air, particularly in heavily urbanised areas, have an adverse effect on many aspects of residents' health (short-term and long-term damage, unpleasant odour and other). A method is proposed for modelling atmospheric NO₂ concentrations in a conurbation, using a partition model M consisting of two separate models: M_L for lower concentration values and M_U for upper values. An advanced data mining technique, that of random forests, is used. This is a method based on machine learning, involving the simultaneous compilation of information from multiple random trees. Using the example of data recorded in Wrocław (Poland) in 2015-2017, an iterative method was applied to determine the boundary concentration y˜ for which the mean absolute deviation error for the partition model attained its lowest value. The resulting model had an R² value of 0.82, compared with 0.60 for a classical random forest model. The importances of the variables in the model M_L, similarly as in the classical case, indicate that the greatest influence on NO₂ concentrations comes from traffic flow, followed by meteorological factors, in particular the wind direction and speed. In the model M_U the importances of the variables are significantly different: while traffic flow still has the greatest impact, the effects of temperature and relative humidity are almost as great. This confirms the justifiability of constructing separate models for low and high pollution concentrations.

Aerosols in an arid environment: The role of aerosol water content, particulate acidity, precursors, and relative humidity on secondary inorganic aerosols

Meteorological conditions, gas-phase precursors, and aerosol acidity (pH) can influence the formation of secondary inorganic aerosols (SIA) in fine particulate matter (PM_2.5). Most works related to the influence of pH and gas-phase precursors on SIA have been laboratory research, but field observation research is very scarce, especially in arid environments. The relationship among SIA, pH, gas-phase precursors, and meteorological conditions are investigated in Hohhot, a major city in China with an arid environment. Secondary inorganic species, e.g., SO₄^2-, NO₃^-, were typically found at low levels, reflecting the low level of secondary aerosol. It is interesting to note that the level of SO₂ in Hohhot was higher than in other cities while SO₄^2- was relatively lower than in other cities. Multiple receptor models were used to explore the contributions to the SIA and quantify the source impacts on the SIA. Annual average aerosol pH in Hohhot was 5.6 (range 1.1-8.4) which was estimated by a thermodynamic equilibrium model. Additionally, a statistical method was used to evaluate the influence of SIA sources on ambient aerosol concentrations. Aerosol water content and particulate acidity were found to be positively associated with secondary SO₄^2-, while NO₂ and RH had a significant impact on secondary NO₃^- in an arid atmosphere. The findings explain the relationship between gaseous precursors, relative humidity, aerosol pH and temperature in the arid city of Hohhot.

Characterization and source identification of PM2.5-bound polycyclic aromatic hydrocarbons (PAHs) in different seasons from Shanghai, China

PM_2.5 samples in four representative periods were collected from a highly industrialized district in Shanghai, China. The concentrations of PM_2.5 and PM_2.5-bound PAHs were analyzed. Positive matrix factorization (PMF) model was used to identify the potential sources. Relationship between PAHs distribution and meteorological parameters was assessed meanwhile. The incremental lifetime cancer risks (ILCRs) model was applied to quantitatively evaluate the exposure risk of PAHs. Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLT) model was used to track the potential pollution area of PM_2.5 along with a Potential Source Contribution Function (PSCF) and Concentration Weighted Trajectory (CWT) methods. The results showed concentrations of PM_2.5 and PAHs ranged from 14.83 to 185.58 μg/m³, 2.58 to 123.62 ng/m³, respectively. The source apportionment model indicated that traffic emissions were the most important sources in each sampling season, which accounted for 38.44%, 34.48%, 39.04% and 45.03%, respectively. Spearman correlation coefficient showed that PAHs had negative correlation with ambient temperature and relative humidity in some periods, while had no significant correlation with atmospheric pressure and visibility. The average estimated lifetime cancer risk for total PAHs reached 4.7 × 10^-5, 4.5 × 10^-5 and 4.1 × 10^-5, 4.0 × 10^-5 to exposed children and adults in winter and autumn, respectively, meaning that PM_2.5-bound PAHs had high potential risk. HYSPLIT model suggested that monsoon greatly influenced the air quality in both winter and autumn.

A correlation study of continuously monitored gamma dose rate and meteorological conditions

In this paper, the correlations between the continuously monitored gamma dose rate (GDR) and meteorological parameters, including precipitation, air temperature, relative humidity, air pressure, wind direction, and wind speed, were analyzed by using one year of the hourly dataset from a monitoring system with ten stations. The correlation coefficients are varied by the range of each meteorological parameter. Precipitation would enhance the GDR up to 84%, which is highly related to precipitation intensity and ground type. Strong and positive correlation between the GDR and light precipitation was identified, while the correlation was reduced with increasing of precipitation. Air temperature could cause a fluctuation of the average GDR within the range 1.8-5.3 nGy h^-1, and different correlation characteristics were indicated for low and high air temperature. The GDR was positively correlated with relative humidity, though relative humidity is inversely correlated with air temperature. Correlations between the GDR and air pressure were mainly negative. Diurnal variations between the GDR and the air temperature, relative humidity, and air pressure were also analyzed. The wind played an important role also in the fluctuation of the GDR with the GDR difference up to 2.00 nGy h^-1 averaged from the sixteen wind-directions. Lower GDR can be found in the direction of prevailing wind because of the dilution effect of the radon progenies in the surface air. In this paper, some exploratory interpretation of physical influence mechanisms of meteorological parameters on the GDR was also presented, which suggests further work should be carried out to explore the variation and correlation principle.