A comparative assessment of air pollutants of smog in wagah border and other sites in Lahore, Pakistan / Uma avaliação comparativa de poluentes do ar do smog na fronteira de wagah e outros sites em Lahore, Paquistão

Abstract Smog has become the fifth season of Pakistan especially in Lahore city. Increased level of air pollutants (primary and secondary) are thought to be responsible for the formation of smog in Lahore. Therefore, the current study was carried out for the evaluation of air pollutants (primary and secondary) of smog in Wagah border particularly and other sites (Jail road, Gulburg) Lahore. For this purpose, baseline data on winter smog from March to December on primary and secondary air pollutants and meteorological parameters was collected from Environmental Protection Department and Pakistan Meteorological Department respectively. Devices being used in both departments for analysis of parameters were also studied. Collected data was further statistically analyzed to determine the correlation of parameters with meteorological conditions and was subjected to air quality index. According to results, PM 10 and PM 2.5 were found very high above the NEQS. NOx concentrations were also high above the permissible limits whereas SO2 and O3 were found below the NEQS thus have no roles in smog formation. Air Quality Index (AQI) of pollutants was PM 2.5(86-227), PM 10 (46-332), NOx (26-110), O3 (19-84) and SO2 (10-95). AQI of PM 2.5 remained between moderate to very unhealthy levels. AQI of PM 10 remained between good to hazardous levels. AQI of NOx remained between good to unhealthy for sensitive groups' levels. AQI of O3 and SO2 remained between good to moderate levels. Pearson correlation showed that every pollutant has a different relation with different or same parameters in different areas. It is concluded from the present study that particulate matter was much more responsible for smog formation. Although NOx also played role in smog formation. So there is need to reduce sources of particulate matter and NOx specifically in order to reduce smog formation in Lahore.

Resumo Smog tornou-se a quinta estação do Paquistão, especialmente na cidade de Lahore. Acredita-se que o aumento do nível de poluentes atmosféricos (primários e secundários) seja responsável pela formação de poluição atmosférica em Lahore. Portanto, o presente estudo foi realizado para a avaliação dos poluentes atmosféricos (primários e secundários) do smog na fronteira de Wagah em particular e em outros locais (Jail road, Gulburg) Lahore. Para este propósito, os dados de referência sobre a poluição atmosférica de inverno de março a dezembro sobre poluentes atmosféricos primários e secundários e parâmetros meteorológicos foram coletados do Departamento de Proteção Ambiental e do Departamento Meteorológico do Paquistão, respectivamente. Dispositivos sendo usados ​​em ambos os departamentos para análise de parâmetros também foram estudados. Os dados coletados foram posteriormente analisados ​​estatisticamente para determinar a correlação dos parâmetros com as condições meteorológicas e foram submetidos ao índice de qualidade do ar. De acordo com os resultados, PM 10 e PM 2,5 foram encontrados muito acima do NEQS. As concentrações de NOx também estavam muito acima dos limites permitidos, enquanto SO2 e O3 foram encontrados abaixo do NEQS, portanto, não têm papéis na formação de smog. O índice de qualidade do ar (AQI) de poluentes foi PM 2,5 (86-227), PM 10 (46-332), NOx (26-110), O3 (19-84) e SO2 (10-95). O AQI de PM 2,5 permaneceu entre níveis moderados a muito prejudiciais à saúde. O AQI de PM 10 permaneceu entre níveis bons e perigosos. AQI de NOx permaneceu entre bom e não saudável para os níveis de grupos sensíveis. O AQI de O3 e SO2 permaneceu entre níveis bons a moderados. A correlação de Pearson mostrou que cada poluente tem uma relação diferente com parâmetros diferentes ou iguais em áreas diferentes. Conclui-se do presente estudo que o material particulado foi muito mais responsável pela formação de smog. Embora o NOx também tenha desempenhado um papel na formação do smog. Portanto, é necessário reduzir as fontes de partículas e NOx, especificamente para reduzir a formação de smog em Lahore.

Assessment of particulate matter (PM) in ambient air of different settings and its associated health risk in Haripur city, Pakistan / Avaliação de material particulado (MP) no ar ambiente de diferentes configurações e sua associação com o risco à saúde na cidade de Haripur, Paquistão

Particulate matter (PM) is a major air pollutant causing serious health problems. The aim of the present study was to find out concentration of PM in ambient air and its associated health risk in Haripur city, Pakistan. Twenty-three samples were taken at various educational institutes, hospitals, recreational areas and industries in Haripur city. Concentration of PM2.5 (µg/m3) and PM10 (µg/m3) was measured with Youngteng YT-HPC 3000A portable PM counter. The results revealed that values of both PM2.5 and PM10 were above the permissible limits (35 µg/m3 for PM2.5 and 150 µg/m3 for PM10) set by Environmental Protection Agency Pakistan (Pak-EPA) in all the educational institutes, hospitals, recreational areas and industries investigated. Furthermore, significant (p<0.05) variation was found in the concentration of both PM2.5 and PM10 in all the educational institutes, hospitals, recreational areas, and industries studied. The concentration of PM2.5 was positively correlated with the concentration of PM10 in all the sampling sites. Therefore, from 1-14 scale standard of health index, the values of PM2.5 and PM10 exhibited that the ambient air quality of Haripur city Pakistan is under high risk. If the regulatory authorities such as Environmental Protection Agency, Health Department and Local Government monitor PM pollution in different settings of Haripur city, then a decrease can be possible in the pollution level. The remedies that can be taken to overcome the problem of ambient air pollution such as PM are plantation of trees at the sites where there are higher levels of air pollutants and use of masks on personal protection basis along with implementation of pollution control system in industries of Hattar Industrial Estate Haripur city, Pakistan.

O material particulado (MP) é um importante poluente do ar que causa sérios problemas de saúde. O objetivo do presente estudo foi descobrir a concentração de MP no ar ambiente e sua associação com o risco à saúde na cidade de Haripur, Paquistão. Vinte e três amostras foram coletadas em várias instituições de ensino, hospitais, áreas recreativas e indústrias na cidade de Haripur. A concentração de MP2,5 (µg/m3) e MP10 (µg/m3) foi medida por meio do contador de MP portátil Youngteng YT-HPC 3000A. Os resultados revelaram que os valores de MP2,5 e MP10 estavam acima dos limites permitidos (35 µg/m3 para MP2,5 e 150 µg/m3 para MP10) estabelecidos pela Agência de Proteção Ambiental do Paquistão (Pak-EPA) em todas as instituições de ensino, hospitais, áreas recreativas e indústrias investigadas. Além disso, foi encontrada variação significativa (p < 0,05) na concentração de MP2,5 e MP10 em todos os locais estudados. A concentração de MP2,5 correlacionou-se positivamente com a concentração de MP10 em todos os locais de amostragem. Portanto, a partir da escala padrão 1-14 do índice de saúde, os valores de MP2,5 e MP10 mostraram que a qualidade do ar ambiente na cidade de Haripur, Paquistão, está sob alto risco. Se as autoridades reguladoras, como a Pak-EPA, o Departamento de Saúde e o governo local, monitorarem a poluição por MP em diferentes configurações da cidade de Haripur, pode ser que haja uma diminuição no nível de poluição. As medidas que podem ser tomadas para superar o problema da poluição do ar ambiente, como o MP, são o plantio de árvores nos locais onde há maiores níveis de poluentes atmosféricos, o uso de máscaras e a implantação de sistema de controle de poluição nas propriedades industriais de Hattar, na cidade Haripur, Paquistão.

Characterization of Fe-containing particles in Chengdu, southwest China, using single-particle aerosol mass spectrometry.

Single-particle aerosol mass spectrometry was used to study the characteristics of Fe-containing particles during winter in Chengdu, southwest China. The mass concentrations of PM2.5 and PM10 during the study period were 64 ± 38 and 89 ± 49 µg/m3, respectively, and NO2 and particulate matter were high compared with most other regions of China. The Fe-containing particles were divided into seven categories with different mass spectra, sources and aging characteristics. The highest contribution was from Fe mixed with carbonaceous components (Fe-C, 23.1%) particles. Fe was more mixed with sulfate than nitrate and therefore the contribution of Fe mixed with sulfate (Fe-S, 20.7%) particles was higher than that of Fe mixed with nitrate (Fe-N, 12.5%) particles. The contributions from Fe-containing particles related to primary combustion were high in the small particle size range, whereas aged Fe-containing particles and dust-related particles were mostly found in the coarse particle size range. The air masses mainly originated from the west and east of Chengdu, and the corresponding PM2.5 concentrations were 79 ± 36 and 55 ± 36 µg/m3, respectively. The west and east air masses showed stronger contributions of Fe-containing particles related to biomass burning (Fe-B) and fossil fuel combustion (Fe-C and Fe-S) particles, respectively. The southwest area contributed the most Fe-containing particles. Future assessments of the effects of Fe-containing particles during heavy pollution period should pay more attention to Fe-C and Fe-S particles. Emission-reduction of Fe-containing particles should consider both local emissions and short-distance transmission from the surrounding areas.

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.

Quantification of perfluorinated compounds in atmospheric particulate shows potential connection with environmental event.

A method of quantification of perfluorinated compounds (PFCs) from atmospheric particulate matter (APM) is described. A single step pretreatment method, selective pressurized liquid extraction (SPLE), was developed to reduce the high matrix background and avoid contamination from commonly used multiple sample pretreatment steps. An effective sorbent was selected to purify the PFCs during SPLE, followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS), for quantification of PFCs. Conditions affecting the SPLE efficiency, including temperature, static extraction time, and number of extraction cycles used, were studied. The optimum conditions were found to be 120°C, 10 min, and 3 cycles, respectively. LC-MS/MS method was developed to obtain the optimal sensitivity specific to PFCs. The method detection limits (MDLs) were 0.006 to 0.48 ng/g for the PFCs studied and the linear response range was from 0.1 to 100 ng/g. To ensure accurate values were obtained, each step of the experiment was evaluated and controlled to prevent contamination. The optimized method was tested by performing spiking experiments in natural particulate matter matrices and good rates of recovery and reproducibility were obtained for all target compounds. Finally, the method was successfully used to measure 16 PFCs in the APM samples collected in Beijing over five years from 2015 to 2019. It is observed that some PFCs follow the trend of total PFC changes, and can be attributed to the environment influencing events and policy enforcement, while others don't seem to change as much with time of the year or from year to year.

Control of fine particulate nitrate during severe winter haze in "2+26" cities.

The "2+26" cities, suffering the most severe winter haze pollution, have been the key region for air quality improvement in China. Increasing prominent nitrate pollution is one of the most challenging environmental issues in this region, necessitating development of an effective control strategy. Herein, we use observations, and state-of-the-art model simulations with scenario analysis and process analysis to quantify the effectiveness of the future SO2-NOX-VOC-NH3 emission control on nitrate pollution mitigation in "2+26" cities. Focusing on a serious winter haze episode, we find that limited NOX emission reduction alone in the short-term period is a less effective choice than VOC or NH3 emission reduction alone to decrease nitrate concentrations, due to the accelerated NOX-HNO3 conversion by atmospheric oxidants and the enhanced HNO3 to NO3- partition by ammonia, although deep NOX emission reduction is essential in the long-term period. The synergistic NH3 and VOC emission control is strongly recommended, which can counteract the adverse effects of nonlinear photochemistry and aerosol chemical feedback to decrease nitrate more. Such extra benefits will be reduced if the synergistic NH3 and VOC reduction is delayed, and thus reducing emission of multiple precursors is urgently required for the effective control of increasingly severe winter nitrate pollution in "2+26" cities.

Effect of catalyst diesel particulate filter aging and catalyst loadings on particulate emission characteristics from a diesel vehicle.

In this study, the effect of new and used catalyzed diesel particulate filter (CDPF) with different catalyst loadings on the particulate emissions including the particle mass (PM), particle number (PN), particle size distribution (PSD) and geometric mean diameter (GMD) from a diesel vehicle were investigated based on a heavy chassis dynamometer. Results showed that more than 97.9% of the PN and 95.4% of the PM were reduced by the CDPF, and the reduction efficiency was enhanced by the catalyst loading. After using the CDPF, the PSD transformed from bimodal to trimodal with the peak shifting towards smaller particle size, more nucleation mode particles were reduced compared with accumulation mode ones, but the reduction effect on the accumulation mode particles was more significantly influenced by the catalyst loading. Notably, the CDPF increased the accumulation mode particles proportion, producing a larger GMD. For the used CDPF, its reduction effect on the particulate emissions enhanced, especially for the PM in accumulation mode. The PSD returned to bimodal, but the peak at accumulation mode began to be higher than that at nucleation mode, illustrating that more nucleation mode particles was removed. The aging of the CDPF resulted in greater effect on the PN-based PSD than that of PM-based PSD, but the effect of catalyst loading on the PN and PM emission factors was weakened. The used CDPF further increased the GMD, and the effect of catalyst loading on the GMD was strengthened, a higher catalyst loading led to a reduction in the GMD.

A short climatology of black and brown carbon and their sources at a suburban site impacted by smoke in Brazil.

Emissions from biomass burning challenge efforts to curb air pollution in cities downwind of fire-prone regions, as they contribute large amounts of brown carbon (BrC) and black carbon (BC) particles. We investigated the patterns of BrC and BC concentrations using Aethalometer data (at λ = 370 and 880 nm, respectively) spanning four years at a site impacted by the outflow of smoke. The data required to be post processed for the shadowing effect since, without correction, concentrations would be between 29% and 35% underestimated. The BrC concentrations were consistently higher than the BC concentrations, indicating the prevalence of aerosols from biomass burning. The results were supported by the Ångström coefficient (Å370/880), with values predominantly larger than 1 (mean ± standard deviation: 1.25 ± 0.31). Å370/880 values below 1 were more prevalent during the wet season, which suggests a contribution from fossil fuel combustion. We observed sharp BrC and BC seasonal signals, with mean minimum concentrations of 0.40 µg/m3 and 0.36 µg/m3, respectively, in the wet season, and mean maximum concentrations of 2.05 µg/m3 and 1.53 µg/m3 in the dry season. The largest concentrations were observed when northerly air masses moved over regions with a high density of fire spots. Local burning of residential solid waste and industrial combustion caused extreme BrC and BC concentrations under favourable wind directions. Although neither pollutant is included in any ambient air quality standards, our results suggest that transboundary smoke may hamper efforts to meet the World Health Organization guidelines for fine particles.

Geochemical elements in suspended particulate matter of Ensenada de La Paz Lagoon, Baja California Peninsula, Mexico: Sources, distribution, mass balance and ecotoxicological risks.

The present study aimed to evaluate multi-element concentrations (Al, As, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Pb, Sr) in suspended particulate material (SPM) collected from Ensenada de La Paz (ELP) lagoon, Baja California Sur, Mexico in two different periods (September and May) to comprehend their origin, geochemical behavior, mass transfer and associated ecotoxicological risks. The 24 hr variation coefficient of volumetric SPM levels were found to be 51.7% in September and 40.5% in May, signifying the effects of oceanic waters. The calculated enrichment factor (EF) values for all the studied elements were of higher magnitude because of the high surface area and oxide nature of SPM, and in this study, Mo had the highest EF of 46.77 probably due to its origin from continental weathering. From the ecotoxicological perspective, the integrated toxic risk index revealed low toxic risk to the benthic community. However, the mean-ERM-Quotient calculated using the particulate concentrations of As, Cd, Cr, Cu, Ni, Pb indicated 9% probability of toxicity to biota. The comprehensive geochemical and ecotoxicological assessment of particulate metal concentrations in the ELP lagoon signify low to moderate contamination.

Nonlinear proinflammatory effect of short-term PM2.5 exposure: A potential role of lipopolysaccharide.

The association between PM2.5 (particulate matter ≤ 2.5 µm) short-term exposure and its health effect is non-linear from the epidemiological studies. And this nonlinearity is suggested to be related with the PM2.5 heterogeneity, however, the underlying biological mechanism is still unclear. Here, a total of 38 PM2.5 filters were collected continuously for three weeks in winter Beijing, with the ambient PM2.5 varying between 10 and 270 µg/m3. Human monocytes-derived macrophages (THP-1) were treated with PM2.5 water-soluble elutes at 10 µg/mL to investigate the PM2.5 short-term exposure effect from a proinflammatory perspective. The proinflammatory cytokine tumor necrosis factor (TNF) induced by the PM2.5 elutes at equal concentrations were unequal, showing the heterogeneity of PM2.5 proinflammatory potentials. Of the various chemical and biological components, lipopolysaccharide (LPS) showed a strong positive association with the TNF heterogeneity. However, some outliers were observed among the TNF-LPS association. Specifically, for PM2.5 from relatively clean air episodes, the higher LPS amount corresponded to relatively low TNF levels. And this phenomenon was also observed in the promotion tests by treating macrophages with PM2.5 elutes dosed with additional trace LPS. Gene expression analysis indicated the involvement of oxidative-stress related genes in the LPS signaling pathway. Therefore, a potential oxidative-stress-mediated suppression on the PM2.5-borne LPS proinflammatory effect was proposed to be accounted for the outliers. Overall, the results showed the differential role of LPS in the heterogeneity of PM2.5 proinflammatory effects from a component-based perspective. Future experimental studies are needed to elucidate the signaling pathway of LPS attached on PM2.5 from different air quality episodes.

Electrostatic removal of ultrafine carbon black with square-grooved collecting plates: Insights for capturing black carbon emitted from ships.

Ships and other mobile pollution sources emitted massive ultrafine and low-resistivity particles containing black carbon (BC), which were harmful to human health and were difficult to capture by conventional electrostatic precipitators (ESPs). In this study, nanoscale carbon black was adopted as simulated particles (SP) with similar physicochemical properties for black carbon emitted from ships (SP-BC) to investigate the feasibility of using an ESP with square-grooved collecting plates for the removal of SP-BC at low backpressures. The increased applied voltage significantly improved the total collection of SP-BC whereas may also promote the conversion of relatively larger particle size SP-BC into nano-size below 20 nm. The outlet number concentration of SP-BC under 27 kV at 130°C was three times that of the inlet. While the reduction of the flow rate could strengthen the capture of SP-BC below 20 nm, and under the combined action of low flow rate and maximum applied voltage, the collection efficiency of 20-100 nm SP-BC could exceed 90%. In addition, the escape and capture characteristics of SP-BC under long-term rapping were revealed. The square-grooved collecting plate could effectively restrain the re-entrainment of collected SP-BC generated by rapping, and the nanoscale SP-BC was trapped in the grooves after rapping. The results could provide insights into the profound removal of massive nanoscale black carbon emissions from mobile sources.

Aerosol-radiation interaction and its variation in North China within 2015-2019 period under continuous PM2.5 improvements.

A study was conducted on aerosol-radiation interactions over six cities in this region within the 2015-2019 period. WRF-Chem simulations on 2017 showed that based on the six-city average, the aerosol load (PM2.5 concentrations) of 121.9, 49.6, 43.3, and 66.3 µg/m3 in January, April, July, and October, mainly lowered the level of downward shortwave radiation by 38.9, 24.0, 59.1, and 24.4 W/m2 and reduced the boundary layer height by 79.9, 40.8, 87.4, and 31.0 m, via scattering and absorbing solar radiation. The sensitivity of meteorological changes to identical aerosol loads varied in the order July > January > October and April. Then, the cooling and stabilizing effects of aerosols further led to increases in PM2.5, by 23.0, 3.4, 4.6, and 7.3 µg/m3 respectively in the four months. The sensitivity of the effect of aerosols on PM2.5 was greatest in January rather than in July, contrary to the effect on meteorology. Moreover, a negative linear relation was observed between daily BLH reductions and aerosol loads in fall and winter, and between PM2.5 increases and aerosol loads in all seasons. With the PM2.5 pollution improvements in this region, the aerosol radiative forcing was effectively reduced. This should result in daily BLH increases of 10-24 m in fall and winter, and the estimates in Beijing agreed well with the corresponding results based on AMDAR data. Additionally, the reduction in aerosol radiation effects brought about daily PM2.5 decreases of 1.6-2.8 µg/m3, accounting for 7.0%-17.7% in PM2.5 improvements.

When and where to exercise: An assessment of personal exposure to urban tropical ambient airborne pollutants in Singapore.

BACKGROUND: Physical activity is associated with health benefits and has been shown to reduce mortality risk. However, exposure to high levels of ambient fine particulate matter (PM2.5) during exercise can potentially reduce the health benefits of physical activity. This study aims to assess and compare the PM2.5 concentrations of different exercise venues in Singapore by their location attributes and time of day. METHODS: Personal PM2.5 exposures (µg/m3) at 24 common outdoor exercise venues in Singapore over 49 sampling days were collected using real-time personal sensors from September 2017 to January 2020. Wilcoxon rank-sum test and Kruskal-Wallis test were used to compare PM2.5 concentrations between different timings (peak (0700-0900; 1800-2000) vs. non-peak (0600-0700; 0900-1800; 2000-2300); weekend vs. weekday), and location attributes (near major roads (<50 m) vs. away from major roads (≥50 m)). Multivariable linear regression models were used to assess the associations between location attributes, timings and ambient PM2.5 with personal PM2.5 concentration, adjusting for potential confounders. RESULTS: Compared with peak hours, exercising during non-peak hours was associated with a significantly lower PM2.5 exposure (median, 17.8 µg/m3 during peak vs. 14.5 µg/m3 during non-peak; P = 0.006). Exercise venues away from major roads have significantly lower PM2.5 concentrations as compared to those located next to major roads (median, 14.4 µg/m3 away from major roads vs. 18.5 µg/m3 next to major roads; P < 0.001). Individuals who exercised in parks experienced the highest PM2.5 exposure (median, 55.0 µg/m3) levels in the afternoon during 1400-1500. Furthermore, ambient PM2.5 concentration was significantly and positively associated with personal PM2.5 exposure (ß = 0.85, P < 0.001). CONCLUSIONS: Our findings suggest that exercising outdoors in the urban environment exposes individuals to differential levels of PM2.5 at different times of the day. Further research should investigate a wider variety of outdoor exercise venues, explore different types of air pollutants, and consider the varying activity patterns of individuals.

Synergy of different leaf traits determines the particulate matter retention capacity and its susceptibility to rain wash-off.

Rainfall plays a crucial role in the removal of particulate matter (PM) from plant leaves, influencing PM retention and the environmental behaviour of harmful substances that accumulate in PM. This study examined the PM retention capacity, particle size distributions, and wash-off rates of leaf surface PM from three common green tree species in northern China during two natural rainfall events (light rain: 8.3 mm; heavy rain: 54.2 mm), to investigate the relationship between the leaf traits, PM retention capacity, and PM wash-off process. Our results found that leaf morphometric characteristics, such as leaf size, length, width, and aspect ratio (length-to-width), had a negative and significant correlations with the PM retention capacity, but had no significant correlation with the leaf surface PM wash-off rate. Smaller leaves with low aspect ratios exhibited greater stability under external disturbances than large leaves with high aspect ratios, resulting in a higher PM retention capacity and lower wash-off rate. Ridges and grooves enhanced the PM retention capacity by increasing the leaf roughness. Rainfall could wash off all particle size ranges of leaf surface PM without altering their mechanical composition. Larger particles were more easily washed off. Euonymus japonicus, with its small leaf size and low aspect ratio, exhibited the highest PM retention capacity. Its curled leaf shape also hindered light rain from washing off leaf surface PM. Forsythia suspensa, with denser grooves and ridges compared with Prunus serrulata, exhibited a rougher leaf surface and higher PM retention capacity. However, this roughness may reduce wettability, making it easier for runoff to form on the leaf surface and dislodge leaf surface PM, resulting in F. suspensa having the highest wash-off rate. Our results highlight the synergy of different leaf traits on PM retention capacity and the PM stability after rainfall.

Impact of agricultural activity on PM2.5 and its compositions in elementary schools near corn and rice farms.

Agricultural activity is an important source of particulate matter <2.5 µm in size (PM2.5) in rural areas. In Taiwan, many elementary schools are surrounded by farms, and studies investigating the impact of agricultural activity on air quality in schools are required. We collected PM2.5 samples from the classrooms of elementary schools near corn and rice farms during the crop cultivation stages and analyzed their concentrations and compositions to investigate whether agricultural activity affects the schools' air quality. We found that the average ratio of PM2.5/PM10 (<10 µm in particle size) was <0.6 in the school near the corn farm, and that the indoor PM2.5/PM10 ratio was significantly associated (r = 0.93, p < 0.05) with the outdoor ratio. Moreover, the potassium (K) concentration in the school near the corn farm (189.2 ± 119 ng/m3) was higher than that near the rice farm (140.9 ± 116.0 ng/m3). There were higher concentrations of K and crustal elements, and a greater crustal elements/heavy metals ratio, in the school near the corn farm during the sowing and soil covering stages than during other cultivation stages. Positive matrix factorization (PMF) results indicate that agricultural activity was a predominant contributor of PM2.5 in the schools near corn and rice farms, however, PM2.5 from industrial and traffic emissions also affected schools' air quality. In summary, agricultural activity influenced the air quality of schools, especially near the corn farm. Governments should develop air quality management policies to reduce the risk of children suffering exposure to high particle concentrations in these schools and further suggest that the impact of industrial and traffic emissions on air quality also requires attention.

Dynamic fluctuations in plant leaf interception of airborne microplastics.

Plant leaves have been demonstrated to be a crucial sink of airborne microplastics (MPs). However, because of the particular shape of MPs and their relatively weak forces with leaves, the traditional accumulation model used for the adsorption of particulate matter and persistent organic pollutants may not be appropriate for describing the interception of MPs by leaves. Here, we performed a 7-day exploration of the interception of MPs by leaves in downtown Nanning. The abundances and characteristics of leaf-intercepted MPs showed dramatic diurnal fluctuations and interspecies differences (conifers > arbors > shrubs). The fluctuation (Coefficient of Variation (CV) = 0.459; abundances 0.003 ± 0.002 to 0.047 ± 0.005 n·cm-2) was even more drastic than that measured across species (CV = 0.353; 0.06 ± 0.01 to 0.40 ± 0.04 n·cm-2). Further analysis using partial least-squares path modeling demonstrated that stomatal variation and divergence largely dominated diurnal fluctuations and interspecies differences in microplastic interception by leaves, respectively. Our results highlight that the leaf-intercepted MPs is characterized by dynamic fluctuations rather than static equilibrium and reveal the important regulatory roles played by leaf micromorphological structures in intercepting MPs, thus enhancing our understanding of the interactions between terrestrial plants and airborne pollution.

Source apportionment of PM2.5 using PMF combined online bulk and single-particle measurements: Contribution of fireworks and biomass burning.

Fireworks (FW) could significantly worsen air quality in short term during celebrations. Due to similar tracers with biomass burning (BB), the fast and precise qualification of FW and BB is still challenging. In this study, online bulk and single-particle measurements were combined to investigate the contributions of FW and BB to the overall mass concentrations of PM2.5 and specific chemical species by positive matrix factorization (PMF) during the Chinese New Year in Hong Kong in February 2013. With combined information, fresh/aged FW (abundant 140K2NO3+ and 213K3SO4+ formed from 113K2Cl+ discharged by fresh FW) can be extracted from the fresh/aged BB sources, in addition to the Second Aerosol, Vehicles + Road Dust, and Sea Salt factors. The contributions of FW and BB were investigated during three high particle matter episodes influenced by the pollution transported from the Pearl River Delta region. The fresh BB/FW contributed 39.2% and 19.6% to PM2.5 during the Lunar Chinese New Year case. However, the contributions of aged FW/BB enhanced in the last two episodes due to the aging process, evidenced by high contributions from secondary aerosols. Generally, the fresh BB/FW showed more significant contributions to nitrate (35.1% and 15.0%, respectively) compared with sulfate (25.1% and 5.9%, respectively) and OC (14.8% and 11.1%, respectively) on average. In comparison, the aged FW contributed more to sulfate (13.4%). Overall, combining online bulk and single-particle measurement data can combine both instruments' advantages and provide a new perspective for applying source apportionment of aerosols using PMF.

Respiratory Health Effects of Air Pollutants.

Air pollution is a risk factor for asthma and respiratory infection. Avoidance of air pollution is the best approach to mitigating the impacts of pollution. Personal preventive strategies are possible, but policy interventions are the most effective ways to prevent pollution and its effect on asthma and respiratory infection.

Association of exposure to ozone and fine particulate matter with ovarian reserve among women with infertility.

Evidence linking diminished ovarian reserve, a significant cause of female infertility, and exposure to particulate matter with aerodynamic diameters ≤2.5 µm (PM2.5) or O3 exposure remains a critical knowledge gap in female fertility. This study investigated the association between ambient PM2.5, O3 pollution, and anti-Müllerian hormone (AMH), a sensitive marker of ovarian reserve, in reproductive-aged Chinese women. We enrolled 2212 women with spontaneous menstrual cycles who underwent AMH measurements at a reproductive medicine center between 2018 and 2021. The daily mean concentrations of outdoor PM2.5 and O3 were estimated using a validated spatiotemporal model, followed by matching the participants' residential addresses. Three exposure periods were designed according to AMH expression patterns during follicle development. A generalized linear model was used to investigate changes in AMH associated with air pollution. The results showed a mean AMH level of 3.47 ± 2.61 ng/mL. During the six months from primary to early antral follicle stage (Period 1), each 10 µg/m3 increase in PM2.5 and O3 exposure was associated with AMH changes of -0.21 (95% confidence interval [CI]: -0.48, 0.06) ng/mL and -0.31 (95% CI: -0.50, -0.12) ng/mL, respectively. Further analyses indicated that the reduced ovarian reserve measured by AMH level was only significantly associated with PM2.5 exposure during follicle development from the primary to preantral follicle stage (Period 2) but was significantly associated with O3 exposure during Periods 1, 2, and 3. These observations were robust in the dual-pollutant model considering co-exposure to PM2.5 and O3. The results indicated an inverse association between ovarian reserve and ambient O3 exposure and suggested distinct susceptibility windows for O3 and PM2.5 for reduced ovarian reserve. These findings highlight the need to control ambient air pollution to reduce invisible risks to women's fertility, especially at high O3 concentrations.

Weekly prenatal PM2.5 and NO2 exposures in preterm, early term, and full term infants: Decrements in birth weight and critical windows of susceptibility.

BACKGROUND: Previous studies have observed associations between birth weight and prenatal air pollution exposure, but there is not consensus on timing of critical windows of susceptibility. OBJECTIVE: We estimated the difference in birth weight among preterm, early term and full term births associated with weekly exposure to PM2.5 and NO2 throughout gestation. METHODS: We included all singleton live births in the Lower Peninsula of Michigan (United States) between 2007 and 2012 occurring at or after 32 weeks gestational age (n = 497,897). Weekly ambient PM2.5 and NO2 concentrations were estimated at maternal residences using 1-km gridded data from ensemble-based models. We utilized a distributed lag nonlinear model to estimate the difference in birth weight associated with weekly exposures from the last menstrual period (week 0) through 31 weeks gestation for preterm births; through 36 weeks gestation for early term births; and through 38 weeks gestation for full term births. RESULTS: In single-pollutant models, a 5 µg/m3 increase in PM2.5 exposure was associated with a reduction in birth weight among preterm births (-37.1 g [95% confidence interval [CI]: 60.8 g, -13.5 g]); early term births (-13.5 g [95% CI: 26.2 g, -0.67 g]); and full term births (-8.23 g [95% CI: 15.8 g, -0.68 g])]. In single-pollutant models, a 10 ppb increase in NO2 exposure was associated with a -11.7 g (95% CI: 14.46 g, -8.92 g) decrement in birth weight among full term births only. In models co-adjusted for PM2.5 and NO2, PM2.5 exposure was associated with reduced birth weight among preterm births (-36.9 g [95% CI: 61.9 g, -11.8 g]) and NO2 exposure was associated with reduced birth weight among full term births (-11.8 g [95% CI: 14.7 g, -8.94 g]). The largest decrements in birth weight were associated with PM2.5 exposure between approximately 10 and 26 weeks of pregnancy; for NO2 exposure, the largest decrements in birth weight in full term births were associated with exposure between weeks 6-18. CONCLUSION: We observed the largest and most persistent adverse associations between PM2.5 exposure and birth weight in preterm infants, and between NO2 exposure and birth weight in full term infants. Exposure during the first half of pregnancy had a greater impact on birthweight.