Spatio-temporal analysis of urban air pollutants throughout China during 2014-2019

Changes in factor profiles deriving from photochemical losses of volatile organic compounds: Insight from daytime and nighttime positive matrix factorization analyses

Substantial effects of photochemical reaction losses of volatile organic compounds (VOCs) on factor profiles can be investigated by comparing the differences between daytime and nighttime dispersion-normalized VOC data resolved profiles. Hourly speciated VOC data measured in Shijiazhuang, China from May to September 2021 were used to conduct study. The mean VOC concentration in the daytime and at nighttime were 32.8 and 36.0 ppbv, respectively. Alkanes and aromatics concentrations in the daytime (12.9 and 3.08 ppbv) were lower than nighttime (15.5 and 3.63 ppbv), whereas that of alkenes showed the opposite tendency. The concentration differences between daytime and nighttime for alkynes and halogenated hydrocarbons were uniformly small. The reactivities of the dominant species in factor profiles for gasoline emissions, natural gas and diesel vehicles, and liquefied petroleum gas were relatively low and their profiles were less affected by photochemical losses. Photochemical losses produced a substantial impact on the profiles of solvent use, petrochemical industry emissions, combustion sources, and biogenic emissions where the dominant species in these factor profiles had high reactivities. Although the profile of biogenic emissions was substantially affected by photochemical loss of isoprene, the low emissions at nighttime also had an important impact on its profile. Chemical losses of highly active VOC species substantially reduced their concentrations in apportioned factor profiles. This study results were consistent with the analytical results obtained through initial concentration estimation, suggesting that the initial concentration estimation could be the most effective currently available method for the source analyses of active VOCs although with uncertainty.

Short-term exposure to sulfur dioxide and the occurrence of chronic obstructive pulmonary disease: An updated systematic review and meta-analysis based on risk of bias and certainty of evidence

Several studies have documented a relationship between short-term exposure to atmospheric sulfur dioxide (SO2) and chronic obstructive pulmonary disease (COPD). However, findings vary across different regions. This meta-analysis employed a random-effects model to calculate the combined risk estimate for each 10-μg/m3 increase in ambient SO2 concentration. Subgroup analysis aimed to identify sources of heterogeneity. To assess potential bias, studies were evaluated using a domain-based assessment tool developed by the World Health Organization. Sensitivity analyses, based on bias risk, explored how model assumptions influenced associations. An evidence certainty framework was used to evaluate overall evidence quality. The study protocol was registered with PROSPERO (CRD42023446823). We thoroughly reviewed 191 full-text articles, ultimately including 15 in the meta-analysis. The pooled relative risk for COPD was 1.26 (95 % CI 0.94-1.70) per 10-μg/m3 increase in ambient SO2. Eleven studies were deemed high risk due to inadequate handling of missing data. Overall evidence certainty was rated as medium. Given SO2's significant public health implications, continuous monitoring is crucial. Future research should include countries in Africa and Oceania to enhance global understanding of atmospheric SO2-related health issues.

Unexpected changes in source apportioned results derived from different ambient VOC metrics

Although most source apportionments of VOCs use mixing ratios, about 23 % of published studies use mass concentrations. Thus, systematically exploring the changes in VOC source apportioned results caused by metric differences is important to assess the differences in key precursor apportionment results given the observed increases in O3 pollution situation. Different monitoring instruments measured hourly VOC volumetric concentrations in three typical Chinese cities (i.e., Qingdao, Shijiazhuang, and Zhumadian). Converting volumetric to mass concentrations under standard and/or actual temperature-pressure conditions, VOC values with different metrics were obtained. The impacts of different metrics on the source apportionments were then investigated. Compared to the positive matrix factorization of the volumetric data (VC-PMF), the VOC species concentrations with low relative molecular mass (RMM) in the factor profiles substantially decreased in mass data analyses (MC-PMF). However, those species with high RMM substantially increased. There were no substantial differences in the apportioned source contributions based on standard and actual condition mass concentrations. However, the high-low rankings of percent contributions apportioned using the volumetric and mass data produced substantial differences. Compared with the VC-PMF results, the percent contributions of sources dominated by species with low RMM (e.g., natural gas usage and mixed sources containing natural gas usage) apportioned by MC-PMF decreased, while those of sources that emitted high RMM species (e.g., solvent usage and mixed sources containing solvent usage) increased. Source apportionments based on the volumetric concentration data had more practical significance compared to the mass concentration data results for control strategy development since the mass data analyses created issues.

Maternal Exposure to Environmental Air Pollution and Premature Rupture of Membranes: Evidence from Southern China

BACKGROUND Exposure to air pollution (AP) during pregnancy is associated with pre-labor rupture of membranes (PROM). However, there is limited research on this topic, and the sensitive exposure windows remain unclear. The present study assessed the association between AP exposure and the risk of PROM, as well as seeking to identify the sensitive time windows. MATERIAL AND METHODS This retrospective study analyzed 4276 pregnant women's data from Tongling Maternal and Child Health Hospital from 2020 to 2022. We obtained air pollution data, including particulate matter (PM) with an aerodynamic diameter of ≤2.5 μm (PM₂․₅), particulate matter with an aerodynamic diameter of ≤10 μm (PM₁₀), nitrogen dioxide (NO₂), and ozone (O₃), from the Tongling Ecology and Environment Bureau. Demographic information was extracted from medical records. We employed a distributed lag model to identify the sensitive exposure windows of prenatal AP affecting the risk of PROM. We conducted a sensitivity analysis based on pre-pregnancy BMI. RESULTS We found a significant association between prenatal exposure to AP and increased PROM risk after adjusting for confounders, and the critical exposure windows of AP were the 6th to 7th months of pregnancy. In the underweight group, an increase of 10 µg/m³ in PM₂․₅ was associated with a risk of PROM, with an odds ratio (OR) of 1.48 (95% CI: 1.16, 1.89). Similarly, a 10 µg/m³ increase in PM₁₀ was associated with a risk of PROM, with an OR of 1.45 (95% CI: 1.05, 1.77). CONCLUSIONS Prenatal exposure to AP, particularly during months 6-7 of pregnancy, is associated with an increased risk of PROM. This study extends and strengthens the evidence on the association between prenatal exposure to AP and the risk of PROM, specifically identifying the critical exposure windows.

Atmospheric elemental carbon pollution and its regional health disparities in China

Previous studies have reported that atmospheric elemental carbon (EC) may pose potentially elevated toxicity when compared to total ambient fine particulate matter (PM2.5). However, most research on EC has been conducted in the US and Europe, whereas China experiences significantly higher EC pollution levels. Investigating the health impact of EC exposure in China presents considerable challenges due to the absence of a monitoring network to document long-term EC levels. Despite extensive studies on total PM2.5 in China over the past decade and a significant decrease in its concentration, changes in EC levels and the associated mortality burden remain largely unknown. In our study, we employed a combination of satellite remote sensing, available ground observations, machine learning techniques, and atmospheric big data to predict ground EC concentrations across China for the period 2005-2018, achieving a spatial resolution of 10 km. Our findings reveal that the national average annual mean EC concentration has remained relatively stable since 2005, even as total PM2.5 levels have substantially decreased. Furthermore, we calculated the all-cause non-accidental deaths attributed to long-term EC exposure in China using baseline mortality data and pooled mortality risk from a cohort study. This analysis unveiled significant regional disparities in the mortality burden resulting from long-term EC exposure in China. These variations can be attributed to varying levels of effectiveness in EC regulations across different regions. Specifically, our study highlights that these regulations have been effective in mitigating EC-related health risks in first-tier cities. However, in regions characterized by a high concentration of coal-power plants and industrial facilities, additional efforts are necessary to control emissions. This observation underscores the importance of tailoring environmental policies and interventions to address the specific challenges posed by varying emission sources and regional contexts.

Trend and heterogeneity in forced vital capacity among Chinese students during 1985-2019: results from Chinese National Survey on Students' Constitution and Health

BACKGROUND

Forced vital capacity (FVC) reflects respiratory health, but the long-term trend and heterogeneity in FVC of Chinese students were understudied.

METHODS

Data were from Chinese National Survey on Students' Constitution and Health 1985-2019. Super Imposition by Translation and Rotation model was used to draw FVC growth curves. Sex-, region-, and nationality-heterogeneity in FVC was evaluated. Spearman correlation and generalized additive model was used to reveal influencing factors for FVC.

RESULTS

Compared to 1985, age at peak FVC velocity was 1.09, 3.17, 0.74, and 1.87 years earlier for urban male, urban female, rural male, and rural female in 2019, respectively. Peak FVC velocity first decreased and then increased during 1985-2019, only male rebounded to larger than 1985 level. FVC declined from 1985 to 2005 and then raised. Males consistently had higher FVC than females, with disparities increasing in the 13-15 age group. Urban students also had higher FVC than rural students. In 2019, FVC difference between 30 Chinese provinces and the national average showed four scenarios: consistently above national average; less than national average until age 18, then above; greater than national average until age 18, then this advantage reversed; less than national average in almost all the age. Most Chinese ethnic minority students had lower FVC levels compared to Han students. Spearman correlation and generalized additive model showed that age, sex, and height were the leading influencing factors of FVC, followed by socioeconomic and environmental factors.

CONCLUSIONS

Chinese students experienced advanced FVC spurt, and there was sex-, region- and nationality-heterogeneity in FVC. Routine measurement of FVC is necessary in less developed areas of China.

Changes in source apportioned VOCs during high O3 periods using initial VOC-concentration-dispersion normalized PMF

Ambient volatile organic compounds (VOCs) concentrations are affected by emissions, dispersion, and chemistry. This work developed an initial concentration-dispersion normalized PMF (ICDN-PMF) to reflect the changes in source emissions. The effects of photochemical losses for VOC species were corrected by estimating the initial data, and then applying dispersion normalization to reduce the impacts of atmospheric dispersion. Hourly speciated VOC data measured in Qingdao from March to May 2020 were utilized to test the method and had assessed its effectiveness. Underestimated solvent use and biogenic emissions contributions due to photochemical losses during the O3 pollution (OP) period reached 4.4 and 3.8 times the non-O3 pollution (NOP) period values, respectively. Increased solvent use contribution due to air dispersion during the OP period was 4.6 times the change in the NOP period. The influence of chemical conversion and air dispersion on the gasoline and diesel vehicle emissions was not apparent during either period. The ICDN-PMF results suggested that biogenic emissions (23.1 %), solvent use (23.0 %), motor-vehicle emissions (17.1 %), and natural gas and diesel evaporation (15.8 %) contributed most to ambient VOCs during the OP period. Biogenic emissions and solvent use contributions during the OP period increased by 187 % and 135 % compared with the NOP period, respectively, whereas that of liquefied petroleum gas substantially decreased during the OP period. Controlling solvent use and motor-vehicles could be effective in controlling VOCs in the OP period.

Spatiotemporal characteristics of air pollutants and their associated health risks in '2+26' cities in China during 2016-2020 heating seasons

To understand characteristics of air pollutants and their associated health risks in recent heating seasons in China, ambient monitoring data of six air pollutants in '2 + 26' cities in Beijing-Tianjin-Hebei and its surrounding areas (known as the BTH2+26 cities) during 2016-2020 heating seasons was analyzed. Results show that daily average concentrations of PM2.5, PM10, SO2, NO2, and CO dropped significantly in BTH2+26 cities from the 2016-2017 heating season to 2019-2020 heating season, while 8h O3 increased markedly. During 2016-2020 heating seasons, annual average values of total excess risks (ERtotal) were 2.3% mainly contributed by PM2.5 (54.4%) and PM10 (36.1%). With PM2.5 pollution worsening, PM10 and NO2 were the important contribution factors of the enhanced ERtotal. Higher health-risk based air quality index (HAQI) values were mainly concentrated in the western Hebei and northern Henan. HAQI showed spatial agglomeration effect in four heating seasons. Impact factors of HAQI varied in different heating seasons. These findings can provide useful insights for China to further propose effective control strategies to alleviate air pollution in the future.

Effect of photochemical losses of ambient volatile organic compounds on their source apportionment

Photochemical losses of ambient volatile organic compounds (VOCs) substantially affect source apportionment analysis. Hourly speciated VOC data measured from April to August 2020 in Tianjin, China were used to analyze the photochemical losses of VOC species and assess the impacts of photochemical losses on source apportionment by comparing the positive matrix factorization (PMF) results based on observed and initial concentration data (OC-PMF and IC-PMF). The initial concentrations of the VOC species were estimated using a photochemical age-based parameterization method. The results suggest that the average photochemical loss of total VOCs (TVOCs) during the ozone pollution period was 2.4 times higher than that during the non-ozone pollution period. The photochemical loss of alkenes was more significant than that of the other VOC species. Temperature has an important effect on photochemical losses, and different VOC species have different sensitivities to temperature; high photochemical losses mainly occurred at temperatures between 25 °C and 35 °C. Photochemical losses reduced the concentrations of highly reactive species in the OC-PMF factor profile. Compared with the IC-PMF results, the OC-PMF contributions of biogenic emissions and polymer production-related industrial sources were underestimated by 73 % and 50 %, respectively, likely due to the oxidation of isoprene and propene, respectively. The contribution of diesel and gasoline evaporation was underestimated by 39 %, which was likely due to the loss of m,p-xylene. Additionally, the contributions of liquefied petroleum gas, vehicle emissions, natural gas, and oil refinery were underestimated by 31 %, 29 %, 23 %, and 13 %, respectively. When the O₃ concentrations were higher than 140 μg m^-3 or the temperatures were higher than 30 °C, the photochemical losses from most sources increased substantially. Additionally, solar radiation produced different photochemical losses for different source types.

Global Trends of Acidity in Rainfall and Its Impact on Plants and Soil

Due to its deleterious and large-scale effects on the ecosystem and long-range transboundary nature, acid rain has attracted the attention of scientists and policymakers. Acid rain (AR) is a prominent environmental issue that has emerged in the last hundred years. AR refers to any form of precipitation leading to a reduction in pH to less than 5.6. The prime reasons for AR formation encompass the occurrence of sulfur dioxide (SO2), nitrogen oxides (NOx), ozone (O3), and organic acids in air produced by natural as well as anthropogenic activities. India, the top SO2 emitter, also shows a continuous increase in NO2 level responsible for AR formation. The plants being immobile unavoidably get exposed to AR which impacts the natural surrounding negatively. Plants get affected directly by AR due to reductions in growth, productivity, and yield by damaging photosynthetic mechanisms and reproductive organs or indirectly by affecting underground components such as soil and root system. Genes that play important role in plant defense under abiotic stress gets also modulated in response to acid rain. AR induces soil acidification, and disturbs the balance of carbon and nitrogen metabolism, litter properties, and microbial and enzymatic activities. This article overviews the factors contributing to AR, and outlines the past and present trends of rainwater pH across the world, and its effects on plants and soil systems.

Global review of source apportionment of volatile organic compounds based on highly time-resolved data from 2015 to 2021

Highly time-resolved data for volatile organic compounds (VOCs) can now be monitored. Source analyses of such high time-resolved concentrations provides key information for controlling VOC emissions. This work reviewed the literature on VOCs source analyses published from 2015 to 2021, and assesses the state-of-the-art and the existing issues with these studies. Gas chromatography system and direct-inlet mass spectrometry are the main monitoring tools. Quality control (QC) of the monitoring process is critical prior to analysis. QC includes inspection and replacement of instrument consumables, calibration curve corrections, and reviewing the data. Approximately 54% published papers lacked details on the quantitative evaluation of the effectiveness of QC measures. Among the reviewed works, the number of monitored species varied from 5 to 119, and fraction of papers with more than 90 monitored species increased yearly. US EPA PMF v5.0 was the most commonly used (∼86%) for VOC source analyses. However, conventional source apportionment directly uses the measured VOCs and may be problematic given the impacts of dispersion and photochemical losses, uncertainty setting of VOCs data, factor resolution, and factor identification. Excluding species with high-reactivity or estimation of corrected concentrations were often applied to reduce the influence of photochemical reactions on the results. However, most reports did not specify the selection criteria or the specific error fraction values in the uncertainty estimation. Model diagnostic indexes were used in 99% of the reports for PMF analysis to determine the factor resolution. Due to lack of known local source profiles, factor identification was mainly achieved using marker species and characteristic species ratios. However, multiple sources had high-collinearity and the same species were often used to identify different sources. Vehicle emissions and fuel evaporation were the primary contributors to VOCs around the world. Contribution of coal combustion in China was substantially higher than in other countries.

Interference of Urban Morphological Parameters in the Spatiotemporal Distribution of PM10 and NO2, Taking Dalian as an Example

Recently, air quality has become a hot topic due to its profound impact on the quality of the human living environment. This paper selects the tourist city of Dalian as the research object. The concentration and spatial distribution of PM10 and NO2 in the main urban area were analyzed during the peak tourist seasons in summer and winter. Simulations were used to explore the spatial and temporal variation patterns of PM10 and NO2, combining building and road density at different scales to reveal the coupling relationship between individual pollutant components and urban parameters. The results show that the PM10 concentration is high in the center and NO2 is concentrated in the northern district of Dalian City. In an area with a radius of 100 m, the dilution ratio of building density and road density to the concentration of the PM10 pollutants is at least 43%. Still, the concentration of NO2 is only coupled with road density. This study reveals the spatial and temporal variation patterns of PM10 and NO2 in Dalian, and finds the coupling relationship between the two pollutants and building density and road density. This study provides a reference for preventing and controlling air pollution in urban planning.

Association Between Sulfur Dioxide and Daily Inpatient Visits With Respiratory Diseases in Ganzhou, China: A Time Series Study Based on Hospital Data

Background

Sulfur dioxide (SO₂) has been reported to be related to the mortality of respiratory diseases, but the relationship between SO₂ and hospital inpatient visits with respiratory diseases and the potential impact of different seasons on this relationship is still unclear.

Methods

The daily average concentrations of air pollutants, including SO₂ and meteorological data in Ganzhou, China, from 2017 to 2019 were collected. The data on daily hospitalization for respiratory diseases from the biggest hospital in the city were extracted. The generalized additive models (GAM) and the distributed lag non-linear model (DLNM) were employed to evaluate the association between ambient SO₂ and daily inpatient visits for respiratory diseases. Stratified analyses by gender, age, and season were performed to find their potential effects on this association.

Results

There is a positive exposure-response relationship between SO₂ concentration and relative risk of respiratory inpatient visits. Every 10 μg/m³ increase in SO₂ was related to a 3.2% (95% CI: 0.6–6.7%) exaltation in daily respiratory inpatient visits at lag3. In addition, SO₂ had a stronger association with respiratory inpatient visits in women, older adults (≥65 years), and warmer season (May-Oct) subgroups. The relationship between SO₂ and inpatient visits for respiratory diseases was robust after adjusting for other air pollutants, including PM₁₀, NO₂, O₃, and CO.

Conclusion

This time-series study showed that there is a positive association between short-term SO₂ exposure and daily respiratory inpatient visits. These results are important for local administrators to formulate environmental public health policies.

Development and Validation of the Haze Risk Perception Scale and Influencing Factor Scale-A Study Based on College Students in Beijing

Although Beijing's air quality has improved, there is still a long way to go for haze governance. In order to understand haze risk perception and related influencing factors among college students in Beijing, we developed and verified two scales, with college students as the survey object, and analyzed the theoretical framework and realistic level of haze risk perception and influencing factors through empirical research. We showed that the reliability and validity of the two scales are excellent, and they can be used as a powerful tool to measure college students' perception of haze. The haze risk perception scale (HRPS) is divided into four dimensions. The degrees of perception ranked from high to low are: direct consequences perception, indirect consequences perception, risk responsibility perception and risk source perception. The haze risk perception influencing factor scale (HRPIFS) is divided into three dimensions. The degrees of influence ranked from high to low are: personal emotion, media communication and government policy; the three influencing factors all have a significant positive correlation to overall haze risk perception, but personal emotions and media communication are only significantly related to the three dimensions of direct consequence perception, indirect consequence perception and risk source perception. Government policy is only significantly related to the three dimensions of direct consequence perception, indirect consequence perception and risk liability perception. This paper proves the important role of media in haze risk perception and puts forward some policy suggestions to guide the public to form a rational risk perception. These findings can help improve theoretical and practical research related to haze risk.

Spatio-Temporal Characteristics of SO2 across Weifang from 2008 to 2020

China has achieved good results in SO₂ pollution control, but SO₂ pollution still exists in some areas. Analyzing the spatio-temporal distribution of SO₂ is critical for regional SO₂ pollution prevention and control. Compared with existing air pollution studies that paid more attention to PM₂.₅, NO₂ and O₃, and focused on the macro scale, this study took the small-scale Weifang city as the research area, analyzed the temporal and spatial changes in SO₂, discussed the migration trajectory of SO₂ pollution and explored the impact of wind on SO₂ pollution. The results show that the average annual concentration of SO₂ in Weifang has exhibited a downward trend in the past 13 years, showing the basic characteristics of “highest in winter, lowest in summer and slightly higher in spring and autumn”, “highest on Sunday, lowest on Thursday and gradually decreasing from Monday to Thursday” and “highest at 9 a.m., lowest at 4 p.m. and gradually increasing from midnight to 9 a.m.”. SO₂ concentration showed obvious spatial heterogeneity: higher in the north and lower in the south. In addition, Shouguang, Changyi and Gaomi were seriously polluted. The SO₂ pollution shifted from south to northeast. The clean wind direction (southeast wind and northeast wind) of Weifang city accounted for about 41%, and the pollution wind direction (northwest wind and west wind) accounted for about 7%. Drawing from the multi-scale analysis, vegetation, precipitation, temperature, transport situation and human activity were the most relevant factors. Limited to data collection, more quantitative research is needed to gain insight into the influence mechanism in the future.