Impact of winter droughts on air pollution over Southwest China

Short-term association between air pollution and daily genitourinary disorder admissions in Lanzhou, China

The aim of this study was to determine the relationship between short-term exposure to ambient air pollution and the number of daily hospital admissions for genitourinary disorders in Lanzhou. Hospital admission data and air pollutants, including PM2.5, PM10, SO2, NO2, O38h and CO, were obtained from the period 2013 to 2020. A generalized additive model (GAM) combined with distribution lag nonlinear model (DLNM) based on quasi-Poisson distribution was used by the controlling for trends, weather, weekdays and holidays. Short-term exposure to PM2.5, NO2 and CO increased the risk of genitourinary disorder admissions with RR of 1.0096 (95% CI 1.0002-1.0190), 1.0255 (95% CI 1.0123-1.0389) and 1.0686 (95% CI 1.0083-1.1326), respectively. PM10, O38h and SO2 have no significant effect on genitourinary disorders. PM2.5 and NO2 are more strongly correlated in female and ≥ 65 years patients. CO is more strongly correlated in male and < 65 years patients. PM2.5, NO2 and CO are risk factors for genitourinary morbidity, and public health interventions should be strengthened to protect vulnerable populations.

Long-Term Air Pollution Characteristics and Multi-scale Meteorological Factor Variability Analysis of Mega-mountain Cities in the Chengdu-Chongqing Economic Circle

Currently, air quality has become central to global environmental policymaking. As a typical mountain megacity in the Cheng-Yu region, the air pollution in Chongqing is unique and sensitive. This study aims to comprehensively investigate the long-term annual, seasonal, and monthly variation characteristics of six major pollutants and seven meteorological parameters. The emission distribution of major pollutants is also discussed. The relationship between pollutants and the multi-scale meteorological conditions was explored. The results indicate that particulate matter (PM), SO2 and NO2 showed a "U-shaped" variation, while O3 showed an "inverted U-shaped" seasonal variation. Industrial emissions accounted for 81.84%, 58% and 80.10% of the total SO2, NOx and dust pollution emissions, respectively. The correlation between PM2.5 and PM10 was strong (R = 0.98). In addition, PM only showed a significant negative correlation with O3. On the contrary, PM showed a significant positive correlation with other gaseous pollutants (SO2, NO2, CO). O3 is only negatively correlated with relative humidity and atmospheric pressure. These findings provide an accurate and effective countermeasure for the coordinated management of air pollution in Cheng-Yu region and the formulation of the regional carbon peaking roadmap. Furthermore, it can improve the prediction accuracy of air pollution under multi-scale meteorological factors, promote effective emission reduction paths and policies in the region, and provide references for related epidemiological research.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s11270-023-06279-8.

The Interactive Effects between Drought and Air Pollutants on Children's Upper Respiratory Tract Infection: A Time-Series Analysis in Gansu, China

As a destructive and economic disaster in the world, drought shows an increasing trend under the continuous global climate change and adverse health effects have been reported. The interactive effects between drought and air pollutants, which may also be harmful to respiratory systems, remain to be discussed. We built the generalized additive model (GAM) and distributed lag nonlinear model (DLNM) to estimate the effects of drought and air pollutants on daily upper respiratory infections (URTI) outpatient visits among children under 6 in three cities of Gansu province. The Standardized Precipitation Index (SPI) based on monthly precipitation (SPI-1) was used as an indicator of drought. A non-stratified model was established to explore the interaction effect of SPI-1 and air pollutants. We illustrated the number of daily pediatric URTI outpatient visits increased with the decrease in SPI-1. The interactive effects between air pollutants and the number of daily pediatric URTIs were significant. According to the non-stratified model, we revealed highly polluted and drought environments had the most significant impact on URTI in children. The occurrence of drought and air pollutants increased URTI in children and exhibited a significant interactive effect.

Exploring the detailed spatiotemporal characteristics of PM2.5: Generating a full-coverage and hourly PM2.5 dataset in the Sichuan Basin, China

Fine particulate matter (PM_2.5) has received worldwide attention due to its threat to public health. In the Sichuan Basin (SCB), PM_2.5 is causing heavy health burdens due to its high concentrations and population density. Compared with other heavily polluted areas, less effort has been made to generate a full-coverage PM_2.5 dataset of the SCB, in which the detailed PM_2.5 spatiotemporal characteristics remain unclear. Considering commonly existing spatiotemporal autocorrelations, the top-of-atmosphere reflectance (TOAR) with a high coverage rate and other auxiliary data were employed to build commonly used random forest (RF) models to generate accurate hourly PM_2.5 concentration predictions with a 0.05° × 0.05° spatial resolution in the SCB in 2016. Specifically, with historical concentrations predicted from a spatial RF (S-RF) and observed at stations, an alternative spatiotemporal RF (AST-RF) and spatiotemporal RF (ST-RF) were built in grids with stations (type 1). The predictions from the AST-RF in grids without stations (type 2) and observations in type 1 formed the PM_2.5 dataset. The LOOCV R², RMSE and MAE were 0.94/0.94, 8.71/8.62 μg∕m³ and 5.58/5.57 μg∕m³ in the AST-RF/ST-RF, respectively. Using the produced dataset, spatiotemporal analysis was conducted for a detailed understanding of the spatiotemporal characteristics of PM_2.5 in the SCB. The PM_2.5 concentrations gradually increased from the edge to the center of the SCB in spatial distribution. Two high-concentration areas centered on Chengdu and Zigong were observed throughout the year, while another high-concentration area centered on Dazhou was only observed in winter. The diurnal variation had double peaks and double valleys in the SCB. The concentrations were high at night and low in daytime, which suggests that characterizing the relationship between PM_2.5 and adverse health outcomes by daily means might be inaccurate with most human activities conducted in daytime.

Effects of periodic drought with severe exhaust exposure on particle retention capacity and physiological responses of Photinia × fraseri Dress

Urban plants are regarded as an effective agent to control particulate matter (PM) pollution by absorbing PM. Repeated PM and drought stress in urban areas often cause morphological and physiological damage to plants, resulting in lower ecological benefits. Nevertheless, knowledge in PM retention capability, morphology and physiology of plants under repeated stress and cross stress has been barely available. In order to investigate changes in these aspects under repeated stress, we applied periodic drought with severe exhaust exposure on Photinia × fraseri Dress (a common urban tree species with strong PM retention ability). The study was carried out in a six-period scenario, with a duration of 10 days for each period: initial value (R0), initial stress period (S1), initial recovery period (R1) second stress period (S2), second recovery period (R2) and final stress period (S3). The results are as follows: In terms of periodic factor, PM retention of tail gas stress group (P) and cross stress group (PD) in S2 decreased by 10.00 μg/cm² and 12.60 μg/cm² respectively compared with those during S1 (p > 0.05). During S3, the total amount of PM on leaf surface in both P and PD demonstrated a significant decrease (p < 0.05). The retention capacity of P. fraseri may be dramatically limited under multi-period stress. In this experiment, we attribute the decrease of PM retention to the morphological changes (shedding of mature leaves, smaller leaf area and thinner wax layer) and physiological responses (an increase in gas exchange) under multi-period stress. In terms of cross-stress factor, the total retained PM on leaf surface in PD was higher than that in P, especially during S3, and the interaction between drought and PM reached a significant level (p < 0.01, η² = 0.808), which indicated that drought reduced the loss of dust under PM stress. Changes in morphology and gas exchange indicated that the mechanisms for the high dust retention rate on the leaf surface of PD group varied in the three stress periods. In addition, except the chlorophyll relative value, the alleviated accumulation of MDA and intense production of soluble sugar with PD showed favorable responses to disturbance compared with those in P under the repeated stress. Therefore, we infer that, under multi-period stress of drought and tail gas, P. fraseri may better maintain PM retention ability and resistance than under single stress.

Air pollution and hospital admissions for critical illness in emergency department: a tertiary-center research in Changsha, China, 2016-2020

We aimed to comprehensively investigate the associations of air pollutants with hospital admissions for critical illness in ED. Patients with critical illness including level 1 and level 2 of the Emergency Severity Index admitted in ED of Changsha Central Hospital from January 2016 to December 2020 were enrolled. Meteorological and air pollutants data source were collected from the National Meteorological Science Data Center. A Poisson generalized linear regression combined with a polynomial distributed lag model (PDLM) was utilized to explore the effect of air pollution on hospital admissions for critical illness in ED. Benchmarks as references (25th) were conducted for comparisons with high levels of pollutant concentrations (75th). At first, lagged effects of all different air pollutants were analyzed. Then, based on the most significant factor, analyses in subgroups were performed by gender (male and female), age (< 45, 45-65, and > 65), disorders (cardiovascular, neurological, respiratory), and seasons (spring, summer, autumn, and winter). A total of 47,290 patients with critical illness admitted in ED were included. The effects of air pollutants (PM_2.5, PM₁₀, SO₂, NO₂, O₃ and CO) on critical illness ED visits were statistically significant. Strong collinearity between PM_2.5 and PM₁₀ (r = 0.862) was found. Both single-day lag and cumulative-day lag day models showed that PM_2.5 had the strongest effects (lag 0, RR = 1.025, 95% CI 1.008-1.043, and lag 0-14, RR = 1.067, 95% CI 1.017-1.120, respectively). In both PM_2.5 and PM₁₀, the risks of critical illness in male, > 65 ages, respiratory diseases, and winter increased the most significant. Air pollutants, especially PM_2.5 and PM₁₀ exposure, could increase the risk of critical illness admission.

The spatiotemporal variations and propagation of droughts in Plateau Mountains of China

Drought incidents and the pressure on water resources have increased in recent years, which has threatened sustainable development. Recently, research has been conducted on drought propagation. However, few studies have investigated the characteristics and mechanisms of drought propagation in plateau mountainous regions with complex topography, which limits the efforts to mitigate drought. We used the Longchuan River Basin (LRB) in Southwest China as a case study to analyze the spatiotemporal variations of meteorological, hydrological, and agricultural droughts and the process of drought propagation in plateau mountainous regions. Our results demonstrated that: (1) the variation in the intensity, frequency, and coverage of droughts indicated that meteorological droughts and hydrological droughts were increasingly serious, while agricultural droughts were eased from 2000 to 2015; (2) the propagation time between different types of droughts was approximately 2 months; and (3) the propagation sequences of droughts varied by altitude; in particular, agricultural droughts propagated to hydrological droughts at higher altitudes, and the opposite occurred at lower altitudes. We concluded that elevation plays a critical role in the time-space differentiation of drought propagation in plateau mountains. More attention should be paid to the spatial differentiation of drought propagation based on land use under different topographic conditions. The results of this study can provide a new perspective for future drought propagation studies.

Overviewing the air quality models on air pollution in Sichuan Basin, China

Most developing countries in the world face the common challenges of reducing air pollution and advancing the process of sustainable development, especially in China. Air pollution research is a complex system and one of the main methods is through numerical simulation. The air quality model is an important technical method, it allows researchers to better analyze air pollutants in different regions. In addition, the SCB is a high-humidity and foggy area, and the concentration of atmospheric pollutants is always high. However, research on this region, one of the four most polluted regions in China, is still lacking. Reviewing the application of air quality models in the SCB air pollution has not been reported thoroughly. To fill these gaps, this review provides a comprehensive narration about i) The status of air pollution in SCB; ii) The application of air quality models in SCB; iii) The problems and application prospects of air quality models in the research of air pollution. This paper may provide a theoretical reference for the prevention and control of air pollution in the SCB and other heavily polluted areas in China and give some¹inspirations for air pollution forecast in other countries with complex terrain.

Contribution of Northeastern Asian stratospheric warming to subseasonal prediction of the early winter haze pollution in Sichuan Basin, China

Predicting the interannual (IA) variability of the early winter haze pollution (HP) in Sichuan Basin (SCB) and analyzing the contribution of the complex terrain are of great significance and challenge as well. For one thing, this study finds that the second mode of early winter IA variations of the HP in Central Eastern China (CEC) is dominated by the pollutant pattern of SCB, characterized by an extreme value center located over SCB. For another, the mode accounts for 15.1% of the total variance and well represents the IA variability of the areal mean HP in SCB. Furthermore, the anomalous circulations conducive to the severe HP in SCB consist of the strengthened (weakened) north (south) branch of Tibetan Plateau (TP) bypassing westerlies at 700 hPa, enhanced descents over SCB, and a strong inversion layer at 750 hPa, suppressing the precipitation and the development of the planetary boundary layer (PBL) in SCB. As a result, dispersion and wet deposition conditions are poor, favorable for the occurrence of the HP in SCB. Observed evidences show that the regional warming in the upper stratosphere over Northeastern Asia in November can be a possible subseasonal precursory signal for the SCB mode. Above all, the warming at upper stratosphere will propagate downward and arrive at the lower stratosphere in 3-4 weeks. Followed by the southward and downward propagation through the longitudinal tilted isothermal surface, the warming arrives at the tropospheric mid-low latitudes in 2-3 weeks, leading to anomalous warming and descents over TP and SCB. Consequently, SCB sees the aforementioned three-dimensional anomalous circulations. For this reason, a physical-empirical subseasonal prediction model for the IA variability of the early winter HP in SCB is established in terms of the regional stratospheric temperature in November. Apparently, the hindcast shows a promising prediction skill.

Urban drought challenge to 2030 sustainable development goals

In the first two decades of the 21st century, 79 global big cities have suffered extensively from drought disaster. Meanwhile, climate change has magnified urban drought in both frequency and severity, putting tremendous pressure on a city's water supply. Therefore, tackling the challenges of urban drought is an integral part of achieving the targets set in at least 5 different Sustainable Development Goals (SDGs). Yet, the current literatures on drought have not placed sufficient emphasis on urban drought challenge in achieving the United Nations' 2030 Agenda for Sustainable Development. This review is intended to fill this knowledge gap by identifying the key concepts behind urban drought, including the definition, occurrence, characteristics, formation, and impacts. Then, four sub-categories of urban drought are proposed, including precipitation-induced, runoff-induced, pollution-induced, and demand-induced urban droughts. These sub-categories can support city stakeholders in taking drought mitigation actions and advancing the following SDGs: SDG 6 "Clean water and sanitation", SDG 11 "Sustainable cities and communities", SDG 12 "Responsible production and consumption", SDG 13 "Climate actions", and SDG 15 "Life on land". To further support cities in taking concrete actions in reaching the listed SDGs, this perspective proposes five actions that city stakeholders can undertake in enhancing drought resilience and preparedness:1) Raising public awareness on water right and water saving; 2) Fostering flexible reliable, and integrated urban water supply; 3) Improving efficiency of urban water management; 4) Investing in sustainability science research for urban drought; and 5) Strengthening resilience efforts via international cooperation. In short, this review contains a wealth of insights on urban drought and highlights the intrinsic connections between drought resilience and the 2030 SDGs. It also proposes five action steps for policymakers and city stakeholders that would support them in taking the first step to combat and mitigate the impacts of urban droughts.