Higher Concentrations In Winter Research Articles

Characteristics of PM2.5 in Hachinohe, the priority pollution control city in Japan

In the urban area of Hachinohe, Japan, PM2.5 sampling was carried out from May 2015 to February 2021. The average concentration of PM2.5 during the entire sampling period was approximately 11.7 μg m−3, with 4.4 μg m−3 for water soluble ions, 3.3 μg m−3 for carbonaceous species, 0.5 μg m−3 for trace metals, and 3.5 μg m−3 for other species. Based on this comprehensive component information, eight sources were quantitatively explored, among which ship emissions (29%), traffic emissions (19%), and secondary organic aerosols (15%) had relatively high contributions for PM2.5 concentration level. The health risk assessment indicated that the children in Hachinohe City faced serious non-carcinogenic and carcinogenic risks, with corresponding values of 8.0 for HI and 1.2 × 10−4 for CR. The pollutants from ship emissions, secondary nitrates plus coal combustion, and industrial emissions should be of concern. High risk metals included Pb, As, Sb, V, and Cr(VI). Specifically, ship emissions exhibited the highest concentration (5.5 μg m−3) and health risks (HI = 2.2 and CR = 3.0 × 10−5) in summer; priority should be given to controlling pollution in the Port of Hachinohe. The other two sources had the highest concentration in winter (2.0 and 0.5 μg m−3) and were mainly influenced by the polluted air masses from Akita Prefecture, with HI values of 2.4 and 2.5 and CR values of 4.9 × 10−5 and 3.2 × 10−5, respectively. Overall, our study comprehensively revealed the characteristics of PM2.5 in Hachinohe City and conducted an in-depth investigated into its causes of pollution. This information could serve as a scientific basis for developing specific strategies to improve air quality.

Ammonia distribution and ecological risk assessment in nine fresh lakes in China.

With the development of industry and economy, ammonia nitrogen pollutions in surface water are of great concern worldwide. This study investigated the historical contents of total ammonia nitrogen (TAN) and unionized ammonia molecules (NH3) in nine fresh lakes in China during 2014-2022. Three different classification methods (flood season, season, and geographical distribution) were used to analyze the concentration variation of TAN and NH3. The concentration of TAN first decreased and then increased in the flood season, showing a lower concentration in summer and a higher concentration in winter. The variation trend of NH3 was in an opposite way with TAN. Correlation analysis between ammonia and 10 water quality parameters and 4 pollution emission and treatment parameters showed that the correlation coefficient between TAN and total phosphorus (total nitrogen) was 0.44 (0.43), respectively. The correlation coefficients between average annual TAN concentration and total emissions (waste water treatment input) were 0.35 (0.53), respectively. Combined with ecotoxicity data from a series of aquatic species, the ecological risks of TAN and NH3 in lakes were evaluated using hazard quotient and joint probability curve methods. From 2014 to 2022, the probability of 5% species affected in the acute ecological risk of TAN and NH3 is lower than 0.01, but for the chronic ecological risk of TAN and NH3, the probabilities of 5% species affected are 0.003-0.030 and 0.04-0.14, respectively. The chronic ecological risks were higher than the acute ecological risks, and high risks in plateau lakes like Dianchi Lake should be paid more attention to.

Into the wild: coupling otolith and archival tag records to test assumptions underpinning otolith chemistry applications in wild fish

Chronological records of elemental concentrations in fish otoliths are a widely used tool to infer the environmental conditions experienced by individual fish. To interpret elemental signals within the otolith, it is important to understand how both external and internal factors impact ion uptake, transport and incorporation. In this study, we have combined chronological records from otoliths and archival data storage tags to quantify the influence of internal (sex, size, age, growth) and external (temperature, depth, salinity) conditions on otolith elemental chemistry of cod (Gadus morhua) in natural settings of the Baltic Sea. This study focused on elements primarily under physiological control: Phosphorus (P), magnesium (Mg) and zinc (Zn); and elements under environmental control: Strontium (Sr), barium (Ba) and manganese (Mn). Based on known spatial and temporal patterns in environmental conditions and fish size, growth, and maturity, we posed a series of hypotheses of expected otolith element patterns. Partial effects of internal and external drivers on element concentration were analyzed using a Linear Mixed Model approach with random variables (fish and year). Predicted effects of otolith concentrations of all elements under physiological control (P, Mg, Zn) showed similar trends, with distinct seasonal patterns (lowest concentration in late spring, highest concentrations in winter), and a positive correlation with water temperature, in addition to higher Zn and lower P in spawning individuals. Predicted effects of otolith concentrations of elements expected to be predominantly under environmental control showed the predicted geographic and depth-related trends based on ambient salinity (Ba) and coastal hypoxia (Mn). However, contrary to expectation, Sr was unrelated to salinity. Predicted otolith Ba, Sr and Mn concentrations also exhibited pronounced seasonal patterns that were out of phase with each other but appeared to be partly explained by spawning/feeding migrations. While performing laboratory validation studies for adult fish is typically not possible, these results highlight the importance of assessing local water chemistry and freshwater endmembers in one’s study system before otolith elemental chemistry can be reliably used to reconstruct fish habitat use and environmental histories.

Health assessment of emerging persistent organic pollutants (POPs) in PM2.5 in northern and central Taiwan

Over the last two decades, Taiwan has effectively diminished atmospheric concentrations of polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) through the adept utilization of advanced technologies and the implementation of air pollution control devices. Despite this success, there exists a dearth of data regarding the levels of other PM2.5-bound organic pollutants and their associated health risks. To address this gap, our study comprehensively investigates the spatial and seasonal variations, potential sources, and health risks of PCDD/Fs, Polychlorinated biphenyls (PCBs), and Polychlorinated naphthalene (PCNs) in Northern and Central Taiwan. Sampling collections were conducted at three specific locations, including six municipal waste incinerators in Northern Taiwan, as well as a traffic and an industrial site in Central Taiwan. As a result, the highest mean values of PM2.5 (20.3–39.6 μg/m3) were observed at traffic sites, followed by industrial sites (14.4–39.3 μg/m3), and the vicinity of the municipal waste incinerator (12.4–29.4 μg/m3). Additionally, PCDD/Fs and PCBs exhibited discernible seasonal fluctuations, displaying higher concentrations in winter (7.53–11.9 and 0.09–0.12 fg I-TEQWHO/m3) and spring (7.02–13.7 and 0.11-0.16 fg I-TEQWHO/m3) compared to summer and autumn. Conversely, PCNs displayed no significant seasonal variations, with peak values observed in winter (0.05–0.10 fg I-TEQWHO/m3) and spring (0.03–0.08 fg I-TEQWHO/m3). Utilizing a Positive Matrix Factorization (PMF) model, sintering plants emerged as the predominant contributors to PCDD/Fs, constituting 77.9% of emissions. Woodchip boilers (68.3%) and municipal waste incinerators (21.0%) were identified as primary contributors to PCBs, while municipal waste incinerators (64.6%) along with a secondary copper and a copper sludge smelter (22.1%) were the principal sources of PCNs. Moreover, the study specified that individuals aged 19–70 in Northern Taiwan and those under the age of 12 years in Central Taiwan were found to have a significantly higher cancer risk, with values ranging from 9.26 x 10−9-1.12 x 10−7 and from 2.50 x 10−8-2.08 x 10−7respectively.

Pollution Characteristics，Sources，and Secondary Generation of Organic Acids in PM2.5 in Zhengzhou

Organic acids in atmospheric particulate matter are widely involved in various physical and chemical reactions in the atmosphere and contribute greatly to the formation of secondary organic aerosols and haze pollutions. Therefore， the concentration distribution characteristics， sources， and secondary formation of organic acids in particulate matter are of great significance for further investigation of organic aerosols and their secondary transformation. Fine particulate matter （PM2.5） samples were collected in Zhengzhou， and three types of organic acids， including dicarboxylic acids， fatty acids， and resin acids， were analyzed to explore their species distribution， seasonal variations， source contribution， and secondary generation. Malonic acid （di-C3） and succinate acid （di-C4） were the most abundant in the identified dicarboxylic acids， which showed obvious seasonal variations in the order of summer > autumn > winter > spring. Fatty acids had the highest concentration in winter and the lowest concentration in spring， showing obvious bimodal advantages， with the most abundant compounds being palmitic acid and stearic acid （C18）. Principal component analysis and multiple linear regression （MLR） were used to analyze the source of organic acids in PM2.5 in Zhengzhou； the results showed that 35% of the organic acids came from combustion and traffic sources， 24% from cooking sources， 23% from secondary formation， and 17% from natural sources. The ratios of the selected marker species （i.e.， di-C3 / di-C4， F/M， and C18：1 / C18） were used as tracers for the secondary formation of the organic aerosol and its aging process. The results showed that the photochemical reaction was intense in summer， and the proportion of organic aerosol aging or secondary production was high， whereas the photochemical reaction was weak in winter， and the aging degree of organic aerosol was low. Correlation analysis and MLR were used in combination to quantify the relative contribution of gas-phase oxidation and liquid-phase oxidation to dicarboxylic acid formation， and the results showed that gas-phase oxidation played a dominant role in the sampling period （accounting for 58%）， especially in summer （61%）.

Quantification of ambient PM2.5 concentrations adjacent to informal brick kilns in the Vhembe District using low-cost sensors

The widespread exposure to ambient PM2.5 poses a substantial health risk globally, with a more pronounced impact on low- to medium-income nations. This study investigates the spatiotemporal distribution of PM2.5 in the communities hosting informal brickmaking industries in Vhembe District. Utilizing Dylos DC1700, continuous monitoring of PM2.5 was conducted at nine stations adjacent to informal brick kilns from March 2021 to February 2022. The study determined the correction factor for PM2.5 measurements obtained from the Dylos DC1700 when it was collocated with the GRIMM Environmental Dust Monitor 180. Additionally, the diurnal and seasonal variations across monitoring stations were assessed, and potential PM2.5 sources were identified. The study also evaluated the compliance of ambient PM2.5 concentrations across the stations with the South African National Ambient Air Quality Standard (NAAQS) limits. Annual PM2.5 concentrations for the stations ranged from 22.6 to 36.2 μgm−3. Diurnal patterns exhibited peak concentrations in the morning and evening, while seasonal variations showed higher concentrations in winter and lower concentrations in summer and spring. All monitoring stations reported the highest daily exceedance with respect to the daily NAAQS limit in the winter. Major PM2.5 sources included domestic biomass combustion, vehicular emissions, industrial emissions, and construction sites. Well-calibrated low-cost sensors could be employed in suburb regions with scarce air quality data. Findings from the study could be used for developing mitigation strategies to reduce health risks associated with PM2.5 exposure in the area.

Investigation of NOx and related secondary pollutants at Anand Vihar, one of the most polluted area of Delhi

This research investigates the influence of meteorological parameters on NOx concentrations, particularly NO2, and related secondary & primary pollutants at the Anand Vihar interstate bus terminal in Delhi. Statistical analysis of long-term data (2016–2021) examines seasonal, weekly, and daily variations in NOx and other pollutants. Temperature and relative humidity show a significant impact on NO2 levels. Seasonal patterns reveal lower concentrations during the monsoon season and higher concentrations in winter and post-monsoon periods, except for ozone. The year 2018 stands out as the most polluted for NO2. Vehicular activities directly influence pollution, evident through reduced NO2 and benzene levels during the COVID-19 lockdown. The Planetary Boundary Layer (PBL) height plays a critical role, with lower PBL heights associated with increased NO2 concentrations. Electric Vehicles (EVs) have a positive effect on reducing NO2 pollution. Comparison with a less transportation-impacted site highlights higher NO2 concentrations in areas with heavy vehicular traffic, emphasizing the need for pollution control measures and sustainable transportation. Correlation and regression analyses confirm the interdependence between PM and NO emissions, underscoring the significance of addressing vehicular emissions for effective pollution mitigation. This study provides valuable insights into the intricate relationship between meteorological parameters, vehicular emissions, and NOx concentrations.

Temporal profile of ionic species and n-alkanes composition of PM10 in a rural environment of Western Himalaya

The temporal profile of PM10 and its composition comprising water-soluble ionic species and n-alkanes studied over the 14 months was segregated into three seasons: winter, summer, and monsoon. The average PM10 concentration exceeds the prescribed National PM10 limits in summer and winter. The PM10 concentration was highest in summer, followed by winter, and lowest in monsoon. Water-soluble inorganic ionic species— major cations (Ca2+, Mg2+, Na+, K+, and NH4+) and anions (F−, Cl−, NO3− and SO42−) contributed an average 30.7% to PM10. The ionic species displayed significant variation, with the highest concentration in winter and the lowest in the monsoon. The secondary inorganic ions, SO42−, NO3−, and NH4+, contributed 84% to the total ionic mass. The ion balance study revealed a strong correlation between anion and cation charge equivalents, suggesting their main contribution to PM10. The neutralization of NO3− + SO42− with NH4+ suggested, NH4+ being the main neutralizing species. n-alkanes concentration in PM10 was significant and showed seasonal variation, highest in the winters and lowest in monsoon. The source profiling of PM10 components, using statistical correlation, regression, and principal component analysis (PCA), revealed solid-fuel biomass, soil dust, and brick kilns and transported materials as major sources.

Approximation of multi-year time series of XCO2 concentrations using satellite observations and statistical interpolation methods

Long-term time series of CO2 concentrations are required for studying e.g., the effects of rising CO2 concentrations on plants and ecosystems. Different methods for approximating column-averaged dry-air mole fractions of CO2 (XCO2) have been developed to substitute missing local CO2 measurements.This study presents a novel method (XCO2SAT+) for determining monthly XCO2 concentrations for selected sites, based entirely on observations from multiple satellites as well as statistical methods in the case of missing satellite data. The product currently covers a period of 16 years from 2003 to 2018. XCO2SAT+ results were validated against data of five European sites of the Total Carbon Column Observing Network (TCCON) and compared to two established XCO2 approximation methods. All three approximation methods were compared to CO2 measurements of German towers from the Integrated Carbon Observation System (ICOS).The mean absolute error (MAE) between the XCO2SAT+ method and TCCON site Karlsruhe, Germany ranges between 0.5 and 1.1 ppm (0.1–0.3%) for years 2014–2018. Mean differences between XCO2SAT+ and XCO2 approximation method CAMS-GCM shows a slightly better MAE of 0.1–0.3 ppm for CAMS-GCM at two German TCCON sites. Multi-year comparisons with ground-level ICOS measurements revealed a comparable seasonality of CO2 concentrations during the vegetation period, but underestimated high winter concentrations, a pattern also observed when comparing with CAMS-GCM. XCO2SAT+ is a suitable alternative and simple method for providing long-term time series of monthly averaged XCO2 concentrations for selected sites, expanding the methodological toolbox for in-situ CO2 research. The new method, which so far provides XCO2 concentrations, will thus serve as a first step towards providing further CO2 data sources, which could be used to further improve numerical models such as atmospheric models or crop growth models and to study CO2 impacts in agriculture and natural ecosystems.

Characteristics, sources and health risk assessment of trace metals and polycyclic aromatic hydrocarbons in PM2.5 from Hefei, China.

Trace metals (TRs) and polycyclic aromatic hydrocarbons (PAHs) are major toxic components of fine particulate matter (PM2.5) and related to various health adverse outcomes. The study aims to get a better understanding of the contents, sources and risks of PM2.5-bounded TRs and PAHs in Hefei, China, during the period of 2019-2021. We collected 504 samples and measured twelve TRs and sixteen priority PAHs by inductively coupled plasma mass spectrometry and high-performance liquid chromatography. The annual mass concentrations of PM2.5 was fluctuated in the year of 2019-2021 at 50.95, 47.48 and 59.38μg/m3, with seasonal variations in rank order of winter > spring > autumn > summer. The median concentrations of PM2.5-bounded ƩTRs and ƩPAHs were also fluctuated, 132.85, 80.93 and 120.27ng/m3 for ƩTRs, 2.57, 5.85 and 2.97ng/m3 for ƩPAHs, in the year of 2019, 2020 and 2021, respectively. Seasonal variations of ƩTRs and ƩPAHs show the highest concentration in winter. Positive matrix factorization was used for identified pollution emission sources, and TRs mainly originated from coal combustion, traffic emission and fugitive dust, while PAHs stemmed from biomass, diesel, gasoline and coal combustion. Health risk assessment indicated that adults were more vulnerable than children, the carcinogenic risk assessment of As and Cr manifested a certain degree of cancer risk (1.0 × 10-6 < CR < 1.0 × 10-4) in adults group, and health risks of TRs were higher than PAHs in Hefei. These findings suggest that PM2.5-bounded TRs and PAHs should be considered when making emission control strategies for air pollution, and winter, combustion sources and adults should achieve more policy attention to decrease exposure risks in Hefei.

Characteristics and sources of VOCs in a coastal city in eastern China and the implications in secondary organic aerosol and O3 formation

Volatile organic compounds (VOCs) play an essential role in the formation of secondary organic aerosol (SOA) and O3. However, our understanding of the characteristics and sources of VOCs in coastal cities is still limited. Here we conducted one-year measurements of VOCs during 2021–2022 in a coastal city in eastern China using Gas Chromatography-Mass Spectrometry. Our results showed strong seasonal variations in total VOCs (TVOCs) with the highest concentrations in winter (28.5 ± 15.1 ppbv) and the lowest values in autumn (14.5 ± 7.6 ppbv). Alkanes dominated the TVOCs during all seasons, on average accounting for 36.2 %–50.2 %, while the contributions of aromatics (5.5 %–9.3 %) were ubiquitously lower than those in other megacities in China. Aromatics exhibited the largest contribution to SOA formation potential (77.6 %–85.5 %) during all seasons, while alkenes (30.9 %–41.1 %) and aromatics (20.6 %–33.2 %) were the dominant contributors to ozone formation potential, and the O3 formation is “VOC-limited” in summer in the city. Particularly, we found that the estimated SOA yield only explained 9.4 %–16.3 % of the observed SOA, suggesting a significant absence of semi-volatile and intermediate-volatile organic compounds. Positive matrix factorization demonstrated that industrial production and fuel combustion were the main sources of VOCs especially in winter (24 % and 31 %), while secondary formation was dominant in summer and autumn (37 % and 28 %). Comparatively, the sources of liquefied petroleum gas and vehicular exhaust were also important, yet did not show strong seasonal variations. Potential source contribution function further highlighted a great challenge for VOCs control in autumn and winter because of the large influences of regional transport.

The impact of seasonality and meteorological conditions on PM2.5 carbonaceous fractions coupled with carbon isotope analysis: Advantages, weaknesses and interpretation pitfalls

PM2.5 samples were collected from October 2020 to September 2021 in Legnica in the Lower Silesia Voivodeship (SW Poland), where environmental guidelines are often exceeded. In order to have a better insight into the respective inputs of local and regional sources concentrations of PM2.5, carbonaceous fractions (TC/OC/EC), carbon isotope composition (δ13CTC) and FTIR spectra of PM2.5 were studied in parallel. The objectives of this study were to (i) identify the emission sources controlling the local aerosol budget and to (ii) discuss the potential limits of the approach used. We highlighted a seasonality in the concentrations of PM2.5, TC, OC, and EC, with higher concentrations in winter resulting of an increased activity of local emission sources coupled to the occurrence of specific meteorological conditions. While we identified coal burning as the main source of pollution in winter, a mix of emissions from coal and bio/organic combustion and road traffic explains the pollution levels in summer. Coupling these findings with the study of FTIR spectra, we corroborated that incomplete combustion of fossil fuels is a major source in winter whereas biogenic particles are in summer. Despite the observed seasonal variations in the OC and EC concentrations, the OC/EC ratios did not show significant variations. It suggests that this ratio, if used as a single proxy to infer sources of carbonaceous aerosols, may lead to interpretation pitfalls. Our results strongly suggest that a multi-proxy approach that couples TC/OC/EC and FTIR to carbon isotope geochemistry provides a reliable evaluation tool for air quality and brings strong constraints on the corresponding sources of PM2.5.

Chemical Characteristics and Source Apportionment of Biogenic Primary and Secondary Organic Aerosols in an Alpine Ecosystem of Tibetan Plateau

AbstractThe knowledge about the chemical characteristics of organic aerosols in alpines were still limited. Fifty samples were collected in an alpine site in Tibetan Plateau during May 2015 and April 2016 to measure the concentrations of sugar and biogenic secondary organic aerosol (BSOA) compounds. The annual mean concentrations of anhydrosugar, primary sugars, and sugar alcohols in Mt. Gongga were 86.6 ± 43.1, 168 ± 40.0 and 204 ± 62.9 ng/m3, respectively. All of the anhydrosugars displayed the highest concentrations in winter, followed by spring, autumn, and the lowest ones in summer, which was contributed by dense biomass burning (BB) in winter. In contrast, nearly all of the primary sugar and sugar alcohol levels peaked in summer, which might be associated with the higher rates of vegetation growth and microbial metabolic activities during the warming season. The levels of BSOA tracers also suffered from markedly seasonal variations. The sesquiterpene SOA displayed the highest level in winter (27.3 ± 16.8 ng/m3), which might be associated with the biomass burning in the surrounding regions. However, most of the species of isoprene and monoterpene SOA tracers suffered from the higher levels in summer, which was contributed by the higher biogenic volatile organic compounds (BVOC) emission and reaction rates. Based on source apportionment result, BB (26%) was the dominant contributor to sugar and BSOA species in Mt. Gongga, followed by airborne pollen (24%), plant release (19%), soil emission (13%), fungal spore (9%), and isoprene oxidation (8%). The result of this study reveals mixed contributions of BB and vegetation emission promote the formation of biogenic organic aerosols in Tibetan Plateau.

An assessment of seasonal, monthly and diurnal variations of ambient air quality in the Gurugram city (Haryana)

Gurugram is emerging as one of India's most advanced cities. The combined impact of industrial and vehicular emissions makes the environment toxic. Recently, Gurugram has experienced severe air quality. In the present work, an assessment of seasonal, monthly, and diurnal variations of ambient air quality was carried out in Gurugram during the period of March 2021 to 2022 February. Seasonal and monthly concentrations of key air pollutants like particulate matter (PM2.5), nitrogen dioxide (NO2), carbon monoxide (CO) and ozone (O3) were examined at Vikas sadan, Gwal Pahari and Teri Gram in Gurugram city to study the most polluted seasons and months. Significantly higher mean concentrations of Particulate matter PM2.5 (406.94 μgm−3) and NO2 (353.96ppb) were seen during the colder months and seasons. O3 showed a consistent trend with variations during the year, with the highest concentration in winter (106.35µg/m3). PM2.5 and NO2 concentrations during the night were greater for all seasons when compared to diurnal values. O3 concentrations displayed diurnal tendencies that were the opposite of those of NO2 concentrations. The highest concentrations of ambient PM2.5, NO2, and CO were observed at the Vikas Sadan Monitoring Station. While the NISE Gwal Pahari station showed greater O3 values. The findings highlight the necessity of efficient air pollution control in Gurugram. To prevent public exposure to air pollutants, preventive measures like green spaces, using public transport, etc. must be adopted. The study contributes to a better understanding of air pollution by seasonal, monthly and diurnal assessment in the city of Gurugram.

Concentration, source apportionment and human health risk assessment of elements in PM2.5 at Agra, India

The present study determined the concentration, seasonal variation, source identification and the human health risk of elements (V, Cr, Mn, Fe, Ni, Cu, Zn, As, Cd, Pb and Si) in fine particulate matter (PM2.5). Samples of PM2.5 were collected at the urban site (Bhagwan Talkies) of Agra, India during January to December 2021. The result showed that the average annual PM2.5 concentration at the urban site was 144.32 ± 57.18 μg m−3 which exceeded the air quality guidelines. Seasonal variation of PM2.5 shows high concentration in winter followed by post-monsoon, summer and monsoon. Among the elements analysed, Si showed the highest concentration and V had the lowest concentration. The concentration of Cr, Ni, As and Cd exceeded the WHO limit, whereas V, Mn and Pb concentrations were below the WHO limit. The significant seasonal variations of elements were observed during the study period. An enrichment factor (EF) was applied to assess the level of the contamination. The possible sources of elements were determined using principal component analysis (PCA). The non-carcinogenic risks for children and adults due to Ni and Cu were higher than the safe level (= 1). The HI values for studied metals for both children and adults were 7.02. The carcinogenic risks for both children and adults due to Pb while for children due to Cd were lower than 1 × 10−6. The carcinogenic risks for other studied metals were higher than 1 × 10−6. The total carcinogenic risks for adults and children were higher than the acceptable limit (1 × 10−6).

Heavy metal fraction, pollution, and source-oriented risk assessment in biofilms on a river system polluted by mining activities

The Lanping Pb–Zn mine is the largest source of Pb and Zn ores in China, thus posing a great threat to local ecosystems and human health. A total of seven heavy metals (Zn, Pb, Ni, Cu, Cr, Cd, and As) in the Bijiang River near the Pb–Zn mine were measured in winter and summer to assess their spatial–temporal enrichment, ecological risk, and source-oriented health risk in periphytic biofilms. Positive matrix factorization (PMF) receptor model and clustering analysis were used to quantitatively identify pollution sources. The results of PMF were then imported into the health risk assessment to further determine the carcinogenic and noncarcinogenic risks of various pollution sources. The results indicated distinct seasonal patterns in metal concentrations, with much higher concentrations in winter. Sites near the Pb–Zn mine tailing reservoir exhibited higher metal contamination levels than other sites. A strong correlation between the enrichment factor and the levels of nonresidual fraction suggested that anthropogenic inputs were the main source of these metals. Mining industries (Cd, Zn, and Pb), natural sources (As, Ni, and Cu), and agricultural activities (Cr) were the primary sources of heavy metal pollution in biofilms, accounting for 44.43%, 33.32%, and 22.26% of the total metal accumulation, respectively. Moreover, the carcinogenic and noncarcinogenic risks via dermal contact of the studied elements in biofilms were typically acceptable. Notably, as concentration was the main factor influencing these risks in children and adults. This study provides evidence that natural epilithic periphyton may be a potential metal biomonitor in aquatic systems and provide supporting information for effective source regulation.

Fine particulate matter and its chemical constituents' levels: A troubling environmental and human health situation in Karachi, Pakistan

Like many urban centers in developing countries, the effect of air pollution in Karachi is understudied. The goal of this study was to determine the chemical characterization, temporal and seasonal variability, sources, and health impacts of fine particulate matter (PM2.5) in Karachi, Pakistan. Daily samples of PM2.5 were collected using a low-volume air sampler at two different sites (Makro and Karachi University) over the four seasons between October 2009 and August 2010. Samples were analyzed for black carbon (BC), trace metals, and water-soluble ions. Results showed that the annual average concentrations of PM2.5 at Makro and Karachi University were 114 ± 115 and 71.7 ± 56.4 μg m−3, respectively, about 22.8 and 14.3-fold higher than the World Health Organization annual guideline of 5 μg m−3. BC concentrations were 3.39 ± 1.97 and 2.70 ± 2.06 μg m−3, respectively. The concentrations of PM2.5, BC, trace metals, and ions at the two sites showed clear seasonal trends, with higher concentrations in winter and lower concentrations in summer. The trace metals and ionic species with the highest concentrations were Pb, S, Zn, Ca, Si, Cl, Fe, and SO42−. The air quality index in the fall and winter at both sites was about 68 %, which is “unhealthy” for the general population. Positive Matrix Factorization revealed the overall contribution to PM2.5 at the Makro site came from three major sources – industrial emissions (13.3 %), vehicular emissions (59.1 %), and oil combustion (23.3 %). The estimates of expected number of deaths due to short-term exposure to PM2.5 were high in the fall and winter at both sites, with an annual mean estimate of 3592 expected number of deaths at the Makro site. Attention should be paid to the reduction of inorganic pollutants from industrial facilities, vehicular traffic, and fossil fuel combustion, due to their extremely high contribution to PM2.5 mass and health risks.

Characterization of nitrated aromatic compounds in fine particles from Nanjing, China: Optical properties, source allocation, and secondary processes

Recently, nitrated aromatic compounds (NACs) have received much attention due to their role as key chromophores of brown carbon (BrC) and their impact on human health and the climate. In this study, a method for detection of 12 NACs in the atmosphere was developed and applied to the detection of 191 atmospheric samples in the northern suburbs of Nanjing in 2017. The average concentration of total NACs in Nanjing was 26.48 ng m−3, which was lower than that in North China. The total NACs also showed obvious seasonal variation, with the highest concentration in winter (51.99 ng m−3) and the lowest concentration in summer (11.26 ng m−3). Moreover, the contribution of subcomponents of NACs also changed with the seasons. Nitrophenols (NPs) and nitrocatechols (NCs) were most abundant in winter, while nitrosalicylic acids (NSAs) were more abundant in summer, accounting for 30%, 27%, and 85%, respectively. The reason for this result may be due to the different sources of dominance of NACs in different seasons. The light absorption of NACs to water-soluble BrC was mainly concentrated in the 300–400 nm range, and its contribution reached the maximum at 310 nm. NPs and NCs had the highest contribution to BrC among all NACs in winter, with a range of 25–54% and 3–59%, respectively. The Positive Matrix Factorization (PMF) was used to analyze the main sources of NACs in different seasons. Secondary generation was the largest source in summer, accounting for 43.5%, and biomass combustion contributed the most in autumn, accounting for 36.7%. NACs are affected by temperature, especially in summer, and the subcomponents vary in temperature dependence. The secondary generation process of NACs is affected by NO2 and O3, especially when NO2 is greater than 40 μg m−3 and O3 is less than 220 μg m−3.

Assessment of traffic-related chemical components in ultrafine and fine particles in urban areas in Vietnam

Ultrafine particles (UFPs or PM0.1; aerodynamic diameter ≤ 0.1 μm) were monitored at a roadside site (RS) in a populated area of Hanoi, Vietnam. Meanwhile, UFPs and fine particles (FPs or PM2.5, aerodynamic diameter ≤ 2.5 μm) were monitored at an ambient site (AS), located at an on-campus a university, approximately 200 m away from the RS. Sampling was conducted in different seasons–summer, winter, and the transitional periods of summer-to-winter and winter-to-summer (STP and WTP, respectively). Carbonaceous and ionic species in UFPs and FPs–rarely investigated in the study area–were analyzed to observe the seasonal variations, characteristics of UFPs near the roadway, and spatial differences between the sites. The UFPs concentration at the AS was in the order of winter > STP > WTP > summer, whereas that of the FPs was winter > WTP > STP > summer. This seasonal variation of particle concentration was possibly affected by the meteorological conditions, which contribute to the highest concentration in winter. The higher FPs concentration in WTP than in STP resulted from the substantial increase in ionic concentrations, particularly sulfate, nitrate, and ammonium. This result indicates the effect of secondary formation processes under drizzle-like weather, which is typical during WTP in northern Vietnam. Compared with UFPs at the AS, traffic-related emissions were more noticeable in UFPs at the RS, including a higher EC concentration and lower OC/EC ratio. The possibility of particle growth under favorable conditions, including the presence of gas-phase pollutants and the availability of surface areas owing to high UFPs concentration in Hanoi, may explain the low correlation of the chemical components between UFPs and FPs in the sites. This study serves as a reference for further investigation of the relationship between UFPs and FPs under highly polluted conditions in big cities in Vietnam in future studies.

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

This study applied two data mining tasks: clustering and association rules to a dataset of pollutants in the state of São Paulo. The clustering task was applied to temporal patterns and geospatial distributions of pollutants, and the association rules were used to identify prevailing meteorological conditions when there were high concentrations of pollutants from 2017 to 2019. The results indicated good adequacy of the cluster, indicating different pollution levels per group, with a silhouette coefficient from 0.26 to 0.72. In the spatial evaluation, the groups severely polluted were located in the metropolitan region, on the coast and, some inland cities, by industrial, vehicular, burning, agriculture, and other emissions. The cluster identified a strong presence of O3 and PM2.5 in 65% and 72% of the monitored stations in several areas of the state. As for the distance between the sources of pollution, the groups of PM10 and NO2 were geographically distant, while PM2.5, CO, SO2, and O3 were closer, suggesting a spatial relationship of exposure. Seasonality was similar between groups, with significantly higher concentrations in winter, except for O3, for which higher concentrations occurred in summer. Meteorological conditions contributed to critical episodes of pollution (support and confidence greater than 80%), with low temperature and humidity, low rainfall, and milder wind associated with increased pollutants. In conclusion, investigating spatial representativeness allows revealing spatial and temporal patterns of pollutants and unfavorable meteorological conditions to diffusion. Thus, ideal and effective measures can be taken to avoid critical periods of exposure based on the behavior of pollutants in different regions and related climate changes.