Comparison of PM10 emission flux of two fugitive area sources based on the real-time flux monitoring results

Due to a high concentration of particulate matter (PM10), the Korean Peninsula experienced its first poor air quality event of the year between November 19 and November 26, 2021. This study analyzes the reasons behind the occurrence of high-concentration PM10, using the real-time PM10 fugitive emission fluxes and meteorological data measured at two landfills for fly ash of coal-fired power plants located on the west coast. The real-time fugitive emission fluxes of PM10 were estimated at two different locations by a flux-gradient technique based on the eddy covariance method. The measurement results show a weak correlation between PM10 and various meteorological factors in the two places when PM10 levels are low. However, high PM10 concentrations were found to be strongly associated with the relative humidity of site A and the friction velocity of site B, respectively. High emission fluxes were observed at both sites under elevated temperature, high humidity, low wind speed, low frictional velocity, and atmospheric instability. The variation in weather patterns witnessed during periods of high PM10 concentrations in the two locations indicates that the causes of PM10 accumulation are different. The study demonstrates that the gradient-flux method's real-time measurement of fugitive emissions can explain the origin of high PM10 levels and provide essential data to efficiently regulate PM10.

Vertical distribution and transport of microplastics in the urban atmosphere: New insights from field observations

The distribution and transport of atmospheric microplastics (AMPs) have raised concerns regarding their potential effects on the environment and human health. Although previous studies have reported the presence of AMPs at ground level, there is a lack of comprehensive understanding of their vertical distribution in urban environments. To gain insight into the vertical profile of AMPs, field observations were conducted at four different heights (ground level, 118 m, 168 m and 488 m) of the Canton Tower in Guangzhou, China. Results showed that the profiles of AMPs and other air pollutants had similar layer distribution patterns, although their concentrations differed. The majority of AMPs were composed of polyethylene terephthalate and rayon fibers ranging from 30 to 50 μm. As a result of atmospheric thermodynamics, AMPs generated at ground level were only partially transported upward, leading to a decrease in their abundance with increasing altitude. The study found that the stable atmospheric stability and lower wind speed between 118 m and 168 m resulted in the formation of a fine layer where AMPs tended to accumulate instead of being transported upward. This study for the first time delineated the vertical profile of AMPs within the atmospheric boundary layer, providing valuable data for understanding the environmental fate of AMPs.

A strong short-duration convection near Poyang Lake in daytime of warm season

Poyang Lake (PL), the biggest freshwater lake in China, is situated in the East Asian Monsoon region, and has an important impact on local convection. In general, PL can result in convection in local region when it is a heat source in nighttime of warm season. However, at around noon on 4 May 2020 (PL is a cold source), a convection was triggered about 20 km west of PL, and rapidly enhanced and resulted in lightning when approaching PL, and then quickly weakened and disappeared after entering the main body of PL. In order to explore the convection formation, several observational data and the Weather Research and Forecasting model were applied in this study. Results show that when the convection approaches PL, its rapid enhancement is induced by PL, and after entering the main body of PL, its quick weakening is also resulted from PL. However, the initiation of the convection is mainly induced by the local topography west of PL under a favorable large-scale background. Mechanism analysis indicates that the strong low-level convergence near the west shore of PL associated with lake-land breeze is responsible for the rapid enhancement of the convection, and the low-level divergence over the main body of PL associated with the lake-land breeze and the increase of the low-level stability induced by cooling of PL jointly result in the quick weakening of the convection. The prevailing southerly wind in low level passes through the local topography (Meling Mountain) west of PL, and is divided into southwesterly wind (flow around Meiling) and southerly wind (flow over Meiling), and they converge in the north of Meling, triggering the convection. This study is not only important to deepen the understanding of PL affecting regional weather, but also helpful for improving the refined forecasting of convection near PL.

Vertical evolution of the concentrations and sources of volatile organic compounds in the lower boundary layer in urban Beijing in summer

Exploring the vertical variations in volatile organic compounds (VOCs) in the atmosphere and quantifying the sources of VOCs at different heights can help control atmospheric photochemical pollution in summer. Here, VOCs were vertically detected at three heights (47 m, 200 m and 320 m) along a 325 m tower of the Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, in the mornings (8:00) and afternoons (15:00) from May 19 to June 18, 2021. The VOC concentrations in Beijing in summer were 16.2 ± 5.6 ppbv, 14.7 ± 2.5 ppbv and 14.9 ± 3.8 ppbv at 47 m, 200 m and 320 m, respectively, and alkanes accounted for the largest proportion at all heights (>56%). The vertical gradients of the VOC concentrations and components did not significantly change, which was consistent with the summer observations of other stations in North China in recent years, but these results significantly differed from observations from more than a decade ago. To determine the reason for this, a classification based on atmospheric stability was performed, revealing that the vertical distribution of VOCs was uniform in convective and stable conditions and decreased with increasing height in neutral condition. With the transition of atmospheric stability from neutral to convective to stable, the contributions of fuel combustion sources and solvent use sources gradually increased, while those of biogenic sources and background sources gradually decreased. With increasing height, the contributions of background sources increased, those of biogenic sources, solvent use and gasoline vehicular emissions decreased, and those of fuel combustion and industrial emissions remained basically unchanged. The above results indicated that with air pollution treatment, the potential for reducing emissions of VOCs in Beijing has decreased. Therefore, regional joint prevention and control are the main ways to control VOC pollution in Beijing.

Investigating detection probability of mobile survey solutions for natural gas pipeline leaks under different atmospheric conditions

The 2015 Paris agreement aims to cut greenhouse gas emissions and keep global temperature rise below 2 °C above pre-industrial levels. Reducing CH₄ emissions from leaking pipelines presents a relatively achievable objective. While walking and driving surveys are commonly used to detect leaks, the detection probability (DP) is poorly characterized. This study aims to investigate how leak rates, survey distance and speed, and atmospheric conditions affect the DP in controlled belowground conditions with release rates of 0.5-8.5 g min^-1. Results show that DP is highly influenced by survey speed, atmospheric stability, and wind speed. The average DP in Pasquill-Gifford stability (PG) class A is 85% at a low survey speed (2-11 mph) and decreases to 68%, 63%, 65%, and 60% in PGSC B/C, D, E/F, and G respectively. It is generally less than 25% at a high survey speed (22-34 mph), regardless of stability conditions and leak rates. Using the measurement data, a validated DP model was further constructed and showed good performance (R²: 0.76). The options of modeled favorable weather conditions (i.e., PG stability class and wind speed) to have a high DP (e.g., >50%) are rapidly decreased with the increase in survey speed. Walking survey is applicable over a wider range of weather conditions, including PG stability class A to E/F and calm to medium winds (0-5 m s^-1). A driving survey at a low speed (11 mph) can only be conducted under calm to low wind speed conditions (0-3 m s^-1) to have an equivalent DP to a walking survey. Only calm wind conditions in PG A (0-1 m s^-1) are appropriate for a high driving speed (34 mph). These findings showed that driving survey providers need to optimize the survey schemes to achieve a DP equivalence to the traditional walking survey.

Emissions vs. turbulence and atmospheric stability: A study of their relative importance in determining air pollutant concentrations

Air pollution in the urban environment is a major concern. The ambient concentrations depend on the levels of transboundary imported pollution, the intensity of local sources and the prevailing atmospheric conditions. This work studies the relative impact of two atmospheric variables-atmospheric stability and regional scale turbulence-in determining the air pollution concentrations. We considered a setting (downtown Haifa, Israel) impacted by a large variety of sources, emitting pollutants with different chemical attributes and atmospheric life times. We found that traffic accounts for most of the locally produced pollution in the study location. However, the meteorological factors can overwhelm its impact and dictate the concentrations. The switch from stable to convective conditions and the more vigorous daytime wind are associated with a premature end of the morning peak concentrations that result from rush hour emissions of NO_x, Black Carbon (BC) and ultra-fine particles. It results in daytime concentration which are lower than (winter) or equal to (summer) those at night, in spite of the much lower night-time traffic volumes. Similar, albeit weaker, impact was detected in the benzene and toluene concentrations. Sources outside the study area are responsible for most of the CO, PM₁ and PM_2.5 concentrations but during winter nights, characterised by strong atmospheric stability and low turbulence, their concentrations are elevated due to the local emissions. We developed a diagnostic statistical nonlinear model for the pollutant concentrations, which points to a stronger association of the atmospheric stability with the concentrations during stable conditions but turbulence dominating during convective conditions. Our findings explain the relatively low overall concentrations of locally emitted pollutants in the study area but warn of the potential for high concentrations during night-time in locations with comparable meteorological conditions.

Effects of fireworks on particulate matter concentration in a narrow valley: the case of the Medellín metropolitan area

The extensive use of fireworks generates large amounts of pollutants, deteriorating air quality and potentially causing adverse health impacts. In Medellín and its metropolitan area, although fireworks are banned during December, their use is widespread during the Christmas season, particularly during the midnight of November 30 (La Alborada) and New Year's Eve (NYE). It is therefore essential to assess the effects of these celebrations on air quality in the region. Air-quality data from the official monitoring network and a low-cost particulate matter (PM) citizen science project, backscattering intensity (BI) retrievals from a ceilometer network, potential temperature from a microwave radiometer, and information from a radar wind profiler provide an excellent platform to study the spatio-temporal distribution of contaminants resulting from the La Alborada and NYE celebrations. Substantial increases in PM2.5 and PM10 mass concentrations due to La Alborada and NYE, ranging in some cases from 50 to 100 μgm^-3, are observed in the Aburrá Valley and particularly in the densely populated communes of Medellín, with most concentration changes corresponding to ultrafine and fine particles. The PM increments resulting from fireworks show almost no increase in the net amount of black carbon in the atmosphere. Ceilometer BI profiles show a substantial change immediately after the La Alborada and NYE midnights, confined to the atmospheric boundary layer (ABL). Strong thermal inversions lead to fairly homogeneous increments in BI within the ABL, lasting until the onset of the convective boundary layer. In contrast, weak thermal inversions lead to rapid dispersion of aerosols, allowing them to episodically escape above the ABL.

Diagnosing atmospheric stability effects on the modeling accuracy of PM2.5 /AOD relationship in eastern China using radiosonde data

Atmospheric stability significantly influences the accumulation and dispersion of air pollutants in the near-surface atmosphere, yet few stability metrics have been applied as predictors in statistical PM_2.5 concentration mapping practices. In this study, eleven stability metrics were derived from radiosonde soundings collected in eastern China for the time period of 2015-2018 and then applied as independent predictors to explore their potential in favoring the prediction of PM_2.5. The statistical results show that the in situ PM_2.5 concentration measurements correlated well with these stability metrics, especially at monthly and seasonal timescales. In contrast, correlations at the daily timescale differed markedly between stability metric and also varied with seasons. Nevertheless, the modeling results indicate that incorporating these stability metrics into the PM_2.5 modeling framework rendered small contribution to PM_2.5 prediction accuracy, yielding an increase of R² by < 5% and a reduction of RMSE by < 1 μg/m³ on average. Compared with other stability indices, the inversion depth and intensity appeared to have relative larger benefiting potential. In general, our findings indicate that including these stability metrics would not result in significant contribution to the PM_2.5 prediction accuracy in eastern China since their effects could be partially overwhelmed or offset by other predictors such as AOD and boundary layer height.

Radon-based atmospheric stability classification in contrasting sub-Alpine and sub-Mediterranean environments

A recently-developed radon-based technique is used to investigate relative changes in summertime atmospheric stability at two sites in Slovenia with contrasting geographical settings. Although atmospheric stability for both sites (50 km apart) was shown to be governed by similar synoptic conditions, their contrasting settings caused differences in mixing conditions for each stability category. At the urban sub-Alpine site Ljubljana, situated within a topographic basin, wind speeds associated with the most stable conditions were 0.2-0.3 m s^-1. By comparison, corresponding wind speeds for the near-coastal sub-Mediterranean site Ajdovščina, located at the foothills of the Trnovski gozd barrier, were 0-0.2 m s^-1. The wind direction at Ljubljana under stable conditions (∼80°) was consistent with drainage flow into the basin along the Sava River valley. The corresponding wind direction at Ajdovščina was 20-40°, consistent with gentle katabatic drainage from the flanks of the Trnovski gozd barrier. After removing fetch effects on radon variability at each site, a large contrast in local contributions to the radon signal was noted: the diurnal amplitude of the local radon signal increased from ∼24 Bq m^-3 at Ljubljana to ∼47 Bq m^-3 at Ajdovščina. This difference was attributed to a greater nocturnal radon accumulation rate at Ajdovščina (3.5 Bq m^-3 h^-1 vs 2.1 Bq m^-3 h^-1) due to higher radon fluxes from flysch and carbonate rocks compared to the sea and lake sediments in the Ljubljana Basin. The ability of radon to consistently distinguish subtle changes in atmospheric mixing at sites with contrasting topographic settings indicates that it will be a powerful tool for characterising air quality in these complex environments. Specifically, diurnal radon cycles indicate that the capability of the atmosphere to dilute primary pollutants is considerably less in the basin environment.

Effects of atmospheric stability and urban morphology on daytime intra-urban temperature variability for Glasgow, UK

This study investigates the joint effect of atmospheric conditions and urban morphology, expressed as the Sky View Factor (SVF), on intra-urban variability. The study has been carried out in Glasgow, UK, a shrinking city with a maritime temperate climate type, and findings could guide future climate adaptation plans in terms of morphology and services provided by the municipality to overcome thermal discomfort in outdoor settings. In this case, SVF has been used as an indicator of urban morphology. The modified Pasquill-Gifford-Turner (PGT) classification system was adopted for classifying the temperature monitoring periods according to atmospheric stability conditions. Thirty two locations were selected on the basis of SVF with a wide variety of urban shapes (narrow streets, neighbourhood green spaces, urban parks, street canyons and public squares) and compared to a reference weather station during a total of twenty three transects during late spring and summer in 2013. Maximum daytime intra-urban temperature differences were found to be strongly correlated with atmospheric stability classes. Furthermore, differences in air temperature are noticeable in urban canyons, with a direct correlation to the site's SVF (or sky openness) and with an inverse trend under open-air conditions.

A proposed methodology for the assessment of arsenic, nickel, cadmium and lead levels in ambient air

Air quality assessment, required by the European Union (EU) Air Quality Directive, Directive 2008/50/EC, is part of the functions attributed to Environmental Management authorities. Based on the cost and time consumption associated with the experimental works required for the air quality assessment in relation to the EU-regulated metal and metalloids, other methods such as modelling or objective estimation arise as competitive alternatives when, in accordance with the Air Quality Directive, the levels of pollutants permit their use at a specific location. This work investigates the possibility of using statistical models based on Partial Least Squares Regression (PLSR) and Artificial Neural Networks (ANNs) to estimate the levels of arsenic (As), cadmium (Cd), nickel (Ni) and lead (Pb) in ambient air and their application for policy purposes. A methodology comprising the main steps that should be taken into consideration to prepare the input database, develop the model and evaluate their performance is proposed and applied to a case of study in Santander (Spain). It was observed that even though these approaches present some difficulties in estimating the individual sample concentrations, having an equivalent performance they can be considered valid for the estimation of the mean values - those to be compared with the limit/target values - fulfilling the uncertainty requirements in the context of the Air Quality Directive. Additionally, the influence of the consideration of input variables related to atmospheric stability on the performance of the studied statistical models has been determined. Although the consideration of these variables as additional inputs had no effect on As and Cd models, they did yield an improvement for Pb and Ni, especially with regard to ANN models.

Influence of atmospheric stability and transport on CH4 concentrations in northern Spain

Continuous methane (CH4) concentrations were measured in Northern Spain over two years (2011-2012) by multi-point sampling at 1.8, 3.7 and 8.3m using a Picarro analyser. The technique is based on cavity ring-down spectroscopy. The contrast in mean concentrations was about 1.2ppb, with 95th percentiles differing by 2.2ppb and mean minimum concentrations proving similar. Temporal variations of CH4 were also analysed, with a similar seasonal variability being found for the three heights. The highest CH4 concentrations were obtained in late autumn and winter and the lowest in summer, yielding a range of 52ppb. This variation may depend on the active photochemical reaction with OH radical during a period of intense solar radiation and changes in soil conditions together with variations in emissions. Peak concentration levels were recorded at night-time, between 5:00-7:00 GMT, with mean values ranging between 1920 and 1923ppb. The lowest value, around 1884ppb, was obtained at 16:00 GMT. This diurnal variation was mainly related to vertical mixing and photochemistry. Therefore, CH4 concentrations were also examined using the bulk Richardson number (RB) as a stability indicator. Four groups were distinguished: unstable cases, situations with pure shear flow, transitional stages and drainage flows. The highest contrast in mean CH4 concentrations between lower and upper heights was obtained for the transition and drainage cases, mainly associated to high concentrations from nearby sources. The impact of long range transport was analysed by means of 3-day isobaric backward air mass trajectories, which were calculated taking into account origins from Europe, Africa, the Atlantic Ocean and Local conditions. Assessment of the results showed the influence of S and SE wind sectors, especially with Local conditions associated with low winds. Finally, an estimation of the background CH4 concentration in the study period provided an average value of about 1892ppb.

Atmospheric stability effects on potential radiological releases at a nuclear research facility in Romania: Characterising the atmospheric mixing state

A radon-based nocturnal stability classification scheme is developed for a flat inland site near Bucharest, Romania, characterised by significant local surface roughness heterogeneity, and compared with traditional meteorologically-based techniques. Eight months of hourly meteorological and atmospheric radon observations from a 60 m tower at the IFIN-HH nuclear research facility are analysed. Heterogeneous surface roughness conditions in the 1 km radius exclusion zone around the site hinder accurate characterisation of nocturnal atmospheric mixing conditions using conventional meteorological techniques, so a radon-based scheme is trialled. When the nocturnal boundary layer is very stable, the Pasquill-Gifford "radiation" scheme overestimates the atmosphere's capacity to dilute pollutants with near-surface sources (such as tritiated water vapour) by 20% compared to the radon-based scheme. Under these conditions, near-surface wind speeds drop well below 1 m s(-1) and nocturnal mixing depths vary from ∼ 25 m to less than 10 m above ground level (a.g.l.). Combining nocturnal radon with daytime ceilometer data, we were able to reconstruct the full diurnal cycle of mixing depths. Average daytime mixing depths at this flat inland site range from 1200 to 1800 m a.g.l. in summer, and 500-900 m a.g.l. in winter. Using tower observations to constrain the nocturnal radon-derived effective mixing depth, we were able to estimate the seasonal range in the Bucharest regional radon flux as: 12 mBq m(-2) s(-1) in winter to 14 mBq m(-2) s(-1) in summer.

A case study of air quality above an urban roof top vegetable farm

The effect of elevation and rooftop configuration on local air quality was investigated at the Brooklyn Grange rooftop farm during a short-term observational campaign. Using multiple particle counters and sonic anemometers deployed along vertical gradients, we found that PM2.5 concentration decayed with height above the street. Samples adjacent to the street had the highest average PM2.5 concentration and frequent stochastic spikes above background. Rooftop observations 26 m above ground showed 7-33% reductions in average PM2.5 concentration compared with the curbside and had far fewer spikes. A relationship between the vertical extinction rate of PM2.5 and atmospheric stability was found whereby less unstable atmosphere and greater wind shear led to greater PM2.5 extinction due to damped vertical motion of air.