Winter Concentrations Research Articles

Short-term association between outdoor temperature and the hydration-marker copeptin: a pooled analysis in five cohorts

Whereas outdoor temperature is linked to both mortality and hydration status, the hormone vasopressin, measured through the surrogate copeptin, is a marker of cardiometabolic risk and hydration. We recently showed that copeptin has a seasonal pattern with higher plasma concentration in winter. Here, we aimed to investigate the association between outdoor temperature and copeptin. Copeptin was analysed in fasting plasma from five cohorts in Malmö, Sweden (n=26,753, 49.7% men, age 18-86 years). We utilized a multivariable adjusted non-linear spline model with four knots to investigate the association between short-term temperature (24h mean apparent) and log copeptin z-score. We found a distinct non-linear association between temperature and log copeptin z-score, with both moderately low and high temperatures linked to higher copeptin concentration (p<0.0001). Between 0°C and nadir at the 75th temperature percentile (corresponding to 14.3°C), log copeptin decreased 0.13 z-scores (95% CI 0.096; 0.16), which also inversely corresponded to the increase in z-score log copeptin between the nadir and 21.3°C. The J-shaped association between short-term temperature and copeptin resembles the J-shaped association between temperature and mortality. Whereas the untangling of temperature from other seasonal effects on hydration warrants further study, moderately increased water intake constitutes a feasible intervention to lower vasopressin and might mitigate adverse health effects of both moderately cold and hot outdoor temperatures. Swedish Research Council, Å Wiberg, M Stephen, A Påhlsson, Crafoord and Swedish Heart-Lung Foundations, Swedish Society for Medical Research and Swedish Society of Medicine.

Epiphytic algae communities and their relationship with environmental factors in the “One River and Two Streams” Basin in Xizang

Due to the uniqueness of natural environment and ecosystem on the Qinghai-Tibet Plateau, the plateau algal community structure and its relationship with environmental factors have received unprecedented attention. In order to explore the epiphytic algae communities and their relationship with environmental factors in the “One River and Two Streams” Basin in Xizang, a total of 7 sampling sites were investigated in four quarters. Water quality evaluation of the study area was based on both hydrochemistry and epiphytic algae. The results showed that a total of 97 species from 60 genera belonging to five phyla were detected. The community was dominated by Bacillariophyta (48 species from 25 genera), Chlorophyta (17 species from 13 genera), and Cyanophyta (26 species from 18 genera), with average annual relative abundances of 88.5%, 6.7%, and 3.6%, respectively. Nitzschia sp. of Bacillariophyta was the dominant species. Significantly higher water temperature (WT) but lower pH was seen in summer than in other seasons. Water turbidity in autumn and ammonia nitrogen (NH3-N) concentration in winter were significantly higher than in other seasons. Total phosphorus (TP) did not change much across seasons. A water quality evaluation based on both hydrochemical parameters (single-factor analysis and comprehensive pollution index, CPI) and the biological index of epiphytic algae (diversity index, pollution indicator species, and index of biotic integrity, IBI) indicated that water quality was mostly at good or medium status. Redundancy analysis (RDA) indicated that the measured environmental factors had no significant effect on the relative abundance and the dominance of pollution indicator species. Dominant species were positively correlated with photosynthetically active radiation (PAR) and ultraviolet A (UVA), and turbidity had a significant negative effect on the number of species. By combining a hydrochemical and biological index, this study emphasizes the importance of water quality monitoring from both a short-term transient as well as a long-term comprehensive perspective. This approach can provide comprehensive and systematic reflections on the health status of waterbodies.

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.

Air pollution prevention in central China: Effects on particulate-bound PAHs from 2010 to 2018

Long-term trends in particulate-bound polycyclic aromatic hydrocarbon (PAH) concentrations in air in Zhengzhou (a severely polluted city in central China) between 2010 and 2018 were studied to assess the effectiveness of an air pollution prevention and control action plan (APPCAP) implemented in 2013. The PM2.5, sum of 16 PAHs (Σ16 PAHs), benzo[a]pyrene (BaP), and BaP toxic equivalent concentrations were high before 2013 but 41%, 77%, 77%, and 78% lower, respectively, after the APPCAP. The maximum daily Σ16 PAHs concentration between 2014 and 2018 was 338 ng/m3, 65% lower than the maximum of 961 ng/m3 between 2010 and 2013. The ratio between the Σ16 PAHs concentrations in winter and summer decreased over time and was 8.0 in 2011 and 1.5 in 2017. The most abundant PAH was benzo[b]fluoranthene, for which the 9-year mean concentration was 14 ± 21 ng/m3 (15% of the Σ16 PAHs concentration). The mean benzo[b]fluoranthene concentration decreased from 28 ± 27 ng/m3 before to 5 ± 4 ng/m3 after the APPCAP (an 83% decrease). The mean daily BaP concentrations were 0.1–62.8 ng/m3, and >56% exceeded the daily standard limit of 2.5 ng/m3 for air. The BaP concentration decreased from 10 ± 8 ng/m3 before to 2 ± 2 ng/m3 after the APPCAP (a 77% decrease). Diagnostic ratios and positive matrix factorization model results indicated that coal combustion and vehicle exhausts were important sources of PAHs throughout the study period, contributing >70% of the Σ16 PAHs concentrations. The APPCAP increased the relative contribution of vehicle exhausts from 29% to 35% but decreased the Σ16 PAHs concentration attributed to vehicle exhausts from 48 to 12 ng/m3. The PAH concentration attributed to vehicle exhausts decreased by 79% even though vehicle numbers strongly increased, indicating that pollution caused by vehicles was controlled well. The relative contribution of coal combustion remained stable but the PAH concentration attributed to coal combustion decreased from 68 ng/m3 before to 13 ng/m3 after the APPCAP. Vehicles made dominant contributions to the incremental lifetime cancer risk (ILCRs) before and after the APPCAP even though the APPCAP decreased the ILCRs by 78%. Coal combustion was the dominant source of PAHs but contributed only 12–15% of the ILCRs. The APPCAP decreased PAH emissions and changed the contributions of different sources of PAHs, and thus strongly affected the overall toxicity of PAHs to humans.

The variability of mass concentrations and source apportionment analysis of equivalent black carbon across urban Europe

This study analyzed the variability of equivalent black carbon (eBC) mass concentrations and their sources in urban Europe to provide insights into the use of eBC as an advanced air quality (AQ) parameter for AQ standards. This study compiled eBC mass concentration datasets covering the period between 2006 and 2022 from 50 measurement stations, including 23 urban background (UB), 18 traffic (TR), 7 suburban (SUB), and 2 regional background (RB) sites. The results highlighted the need for the harmonization of eBC measurements to allow for direct comparisons between eBC mass concentrations measured across urban Europe. The eBC mass concentrations exhibited a decreasing trend as follows: TR > UB > SUB > RB. Furthermore, a clear decreasing trend in eBC concentrations was observed in the UB sites moving from Southern to Northern Europe. The eBC mass concentrations exhibited significant spatiotemporal heterogeneity, including marked differences in eBC mass concentration and variable contributions of pollution sources to bulk eBC between different cities. Seasonal patterns in eBC concentrations were also evident, with higher winter concentrations observed in a large proportion of cities, especially at UB and SUB sites. The contribution of eBC from fossil fuel combustion, mostly traffic (eBCT) was higher than that of residential and commercial sources (eBCRC) in all European sites studied. Nevertheless, eBCRC still had a substantial contribution to total eBC mass concentrations at a majority of the sites. eBC trend analysis revealed decreasing trends for eBCT over the last decade, while eBCRC remained relatively constant or even increased slightly in some cities.

Summer and winter variations of BTEX concentrations in an oil refinery complex and health risk assessment based on Monte-Carlo simulations

The summer and winter concentrations of BTEX pollutants were investigated in various workplaces of an oil Refinery, Iran. In total 252 air samples from the breathing zones of the following employees were collected: supervisors, safetymen, repairmen, site men, and all workers. Carcinogenic and non-carcinogenic risk values were calculated based on the USEPA methodology using Monte Carlo simulations. BTEX concentrations were higher in the summer than in the winter season for all workstations, especially for toluene and ethylbenzene. The mean values of exposure to benzene for repairmen and site men were higher than threshold limit value of 1.60 mg/m3 for both seasons. Non-carcinogenic risk (HQ) values calculated for summer season for benzene, ethylbenzene, and xylene in all workstations, as well as for toluene for repairmen and site men exceeded acceptable level of 1. In winter season the mean HQ values for benzene and xylene in all workstations, for toluene for repairmen and site men, and for ethylbenzene for supervisors, repairmen, and site men were also > 1. For all workstations definite carcinogenic risk was indicated as calculated LCR values for benzene and ethylbenzene exposure were higher than 1 × 10–4 in both summer and winter seasons.

Remote sensing monitoring of total suspended solids concentration in Jiaozhou Bay based on multi-source data

Total suspended solids (TSS) concentration (mg/L) is a significant indicator of coastal water environments monitoring. First, quantitative retrieval models of TSS concentrations in Jiaozhou Bay (JZB) were developed based on Landsat and Moderate Resolution Imaging Spectroradiometer (MODIS) data, and the retrieved TSS concentrations in JZB from 1984 to 2021 were obtained. Then, the reliability of the retrieved TSS from Landsat and MODIS was evaluated, and the temporal and spatial variation in TSS concentration was analyzed. Finally, the main factors influencing the variation in TSS concentration in JZB were analyzed. The results show that both Landsat and MODIS retrieval models proposed in this study have good accuracies (Landsat: R2 = 0.64, RMSE = 2.09 mg/L, MAPD = 33.96%; MODIS: R2 = 0.71, RMSE = 2.54 mg/L, MAPD = 32.81%). The TSS concentration in JZB fluctuated between 1984 and 2021, showing a downward trend. The TSS concentration in JZB exhibited an obvious seasonal variation, with a higher concentration in spring and winter owing to strong winds and a lower concentration in summer and autumn. TSS decreased gradually from northwest to southeast. The average spatial variation scale of TSS monitoring in JZB was 72 m and the optimal observation time window was 10:16–12:16. Although the retrieved TSS of Landsat and MODIS were highly consistent (R2 = 0.70, RMSE = 2.09 mg/L), differences were still observed. The exponential function in the retrieval models was the main reason for the large difference between Landsat TSS and MODIS TSS in the nearshore high-value area. The different spatial resolutions, image acquisition times, and signal-to-noise ratios of Landsat and MODIS were also important reasons for the differences. Wind speed was the main factor influencing the annual, seasonal, and monthly variation in TSS concentration in JZB, while the Jiaozhou Bay Bridge only had an effect on the TSS concentration during the construction period.

Distinct urban-rural gradients of air NO2 and SO2 concentrations in response to emission reductions during 2015–2022 in Beijing, China

Nitrogen dioxide (NO2) and sulfur dioxide (SO2) are two major air pollutants in urban environment. Emission reduction policies have thus been implemented to improve urban air quality, especially in the metropolises. However, it remains unclear whether the air concentrations of NO2 and SO2 in and around large cities follow a same spatial pattern and how their characteristics change over time in response to the emission reductions. Using ground-based monitoring datasets of air NO2 and SO2 concentrations in Beijing, China, we tested the hypothesis of urban air pollutant islands and evaluated their seasonal and inter-annual variations during 2015–2022. The results showed that air NO2 concentrations increased significantly towards the urban core, being in line with the hypothesis of urban air pollutant island, while air SO2 concentrations showed no such spatial patterns. The urban air NO2 island varied seasonally, with larger radius and higher air NO2 concentrations in spring and winter. In response to the emission reduction, the annual mean radius of the urban air NO2 island showed a rapid decrease from 45.8 km to zero km during the study period. The annual mean air NO2 concentration at the urban core showed a linear decrease at a rate of 4.5 μg m−3 yr−1. In contrast, air SO2 concentration decreased nonlinearly over time and showed a legacy in comparison to the emission reduction. Our findings suggest different urban-rural gradients of air NO2 and SO2 concentrations and highlight their distinct responses to the regional reductions of anthropogenic emissions.

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.

Exploring the Spatiotemporal Variation in Light-Absorbing Aerosols and Its Relationship with Meteorology over the Hindukush–Himalaya–Karakoram Region

Light-absorbing aerosols such as black carbon (BC), organic carbon (OC), and dust can cause the warming and melting of glaciers by absorbing sunlight. Further research is needed to understand the impact of light-absorbing aerosols on the Hindukush–Karakoram–Himalaya region in northern Pakistan. Therefore, spatiotemporal variation in absorbing surface mass concentration retrieved from Modern-Era Retrospective analysis for Research and Applications, optical properties such as aerosol optical depth (AOD) and absorption aerosol optical depth (AAOD) from the ozone monitoring instrument, and meteorological parameters from the European Centre for Medium-Range Weather Forecasts Reanalysis were investigated over northern Pakistan from 2001 to 2021. The BC concentration was lowest in May and highest in November, having a seasonal maximum peak in winter (0.31 ± 0.04 µg/m3) and minimum peak in spring (0.17 ± 0.01 µg/m3). In addition, OC concentration was found to be greater in November and smaller in April, with a seasonal higher peak in autumn (1.32 ± 0.32 µg/m3) and a lower peak in spring (0.73 ± 0.08 µg/m3). The monthly and seasonal variabilities in BC and OC concentrations are attributed to solid fuels, biomass burning, changes in vegetation, agricultural activities, and meteorology. In contrast, the dust concentration was high in July and low in December, with a seasonal average high concentration in summer (44 ± 9 µg/m3) and low concentration in winter (13 ± 2 µg/m3) due to drier conditions, dust activity, long-range transport, and human activities. Moreover, the seasonal variation in AOD and AAOD was identical and higher in the summer and lower in the winter due to dust aerosol loading and frequent dust activities. AOD and AAOD followed a similar pattern of spatial variation over the study area. Meteorological parameters greatly impact light-absorbing aerosols; therefore, low temperatures in winter increase BC and OC concentrations due to shallow boundary layers, while severe precipitation in spring decreases concentrations. During summer, dry conditions cause soil erosion and increase the amount of dust suspended in the atmosphere, leading to higher AOD and AAOD values. Conversely, higher precipitation rates and speedy winds disperse the dust aerosols in winter, resulting in lower AOD and AAOD values.

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.

Temporal and spatial relationships of CrAssphage and enteric viral and bacterial pathogens in wastewater in North Carolina

Enteric disease remains one of the most common concerns for public health, particularly when it results from human exposure to surface and recreational waters contaminated with wastewater. Characterizing the temporal and spatial variation of enteric pathogens prevalent in wastewater is critical to develop approaches to mitigate their distribution in the environment. In this study, we aim to characterize pathogen variability and test the applicability of the human-associated wastewater indicator crAssphage as an indicator of enteric viral and bacterial pathogens. We conducted weekly samplings for 14 months from four wastewater treatment plants in North Carolina, USA. Untreated wastewater samples were processed using hollow fiber ultrafiltration, followed by secondary concentration methods. Adenovirus, norovirus, enterovirus, Salmonella, Shiga toxin 2 (stx2), Campylobacter, and crAssphage were measured by quantitative polymerase chain reaction (qPCR) and reverse transcriptase (rt)-qPCR. Our results revealed significant correlations between crAssphage and human adenovirus, enterovirus, norovirus, Salmonella, and Campylobacter (p<0.01). Pathogens and crAssphage concentrations in untreated wastewater showed distinct seasonal patterns, with peak concentrations of crAssphage and viral pathogens in fall and winter, while bacterial pathogens showed peaked concentrations in either winter (Campylobacter), fall (Salmonella), or summer (stx2). This study enhances the understanding of crAssphage as an alternative molecular indicator for both bacterial and viral pathogens. The findings of this study can also inform microbial modeling efforts for the prediction of the impact of wastewater pathogens on surface waters due to increased flooding events and wastewater overflows associated with climate change.

Pollution characteristics and human health risks of PM2.5-bound heavy metals: a 3-year observation in Suzhou, China.

This study aimed to analyze the temporal trends, pollution levels, and health risks associated with eleven PM2.5-bound heavy metals (Sb, Al, As, Hg, Cd, Cr, Mn, Ni, Pb, Se and Tl). A total of 504 PM2.5 samples were collected in Suzhou from January 2019 to December 2021. The pollution levels were estimated based on enrichment factors (EFs) which can be used to calculate the enrichment of heavy metals in PM2.5 and determine whether the concentrations of PM2.5-bound heavy metals are influenced by the crustal or anthropogenic sources, and the health risk of PM2.5-bound heavy metals via inhalation was assessed following US EPA's Risk Assessment Guidance for Superfund (RAGS). The annual average concentration of PM2.5 was 46.76μgm-3, which was higher than the WHO recommended limit of 5μgm-3. The average of the sum of eleven PM2.5-bound heavy metals was 180.61ngm-3, dominated by Al, Mn, and Pb. The concentration of PM2.5 in 2020 was significantly lower than that in 2019 and 2021. The PM2.5 and PM2.5-bound heavy metal concentrations in winter and spring were significantly higher than those in autumn and summer. The EF of As, Cr, Cd, Hg, Ni, Pb, Sb, Mn, Se, and Tl was higher than 10, indicating they were mainly from anthropogenic sources. Exposure to a single non-carcinogenic heavy metal via inhalation was unlikely to cause non-carcinogenic effects (HQ < 1), but the integrated non-carcinogenic risks should be taken seriously (HI > 1). The cumulative carcinogenic risks from the carcinogenic elements were exceeding the lower limit (1 × 10-6) of the acceptable risk range. The carcinogenic risks of As and Cr(VI) contributed 60.98% and 26.77%, respectively, which were regarded as two key carcinogenic risk factors. Overall, the government policies and countermeasures for the PM2.5 pollution control should be performed not only based on the PM2.5 concentration but also based on the PM2.5-bound heavy metals and their health risks for the local residents.

Physical drivers of chlorophyll and nutrients variability in the Southern-Central Arabian Gulf

The southern-central Arabian Gulf demonstrates a poor understanding of nutrients and chlorophyll dynamics in physical-biogeochemical settings. Here, using data of chlorophyll, nutrients and hydrographic parameters collected in two cruises in summer 2019 and winter 2020, we examined variability in nutrients and chlorophyll concentrations, and the driving mechanisms. Summer thermal stratification enhanced by intrusion of fresher surface water plume from the Arabian Sea developed a hypoxic zone (DO < 2.0 mL/L) below the thermocline. Nitrate and ammonium summer concentrations (2.24 ± 0.36, 1.70 ± 0.17 μM) were about 3 times the winter concentrations. Nutrient stoichiometry showed a Redfield-like nitrogen/phosphorus (N:P) ratio in summer (15.9:1) and a nitrogen limitation in winter (N:P = 4:1). Chlorophyll-a content in summer (mean = 0.80 mg/m3) was about 1.4 times the winter concentration (mean = 0.58 mg/m3) (p > 0.05). Photo-protective carotenoids content in summer (0.59 mg/m3) was about 2.7 times their winter concentration. Winter cooling resulted in downwelling of dense water on the shallow coastal banks, which enhanced near bottom oxygen concentrations and swept away nutrient-rich water resulting in lower winter chlorophyll. This research features aspects of the physical and biogeochemical drivers underpinning the dynamics of nutrients and chlorophyll in the central Gulf.

Seasonal variation of physicochemical parameters and heavy metal concentration in water and bottom sediment at harboring areas of Digha coast, West Bengal, India

This investigation attempts to reveal the seasonal variations in physicochemical parameters and heavy metal concentrations in winter and summer at harboring zones in the Digha coastal region of west Bengal. The area showed higher pH, electrical conductivity (EC), total dissolved solids (TDS), biochemical oxygen demand (BOD), sodium, potassium, organic carbon (OC) in summer and higher dissolved oxygen (DO), total alkalinity (TA), total hardness (TH) in winter. The concentration of heavy metals viz., cadmium, zinc, manganese, and chromium exceeded the permissible limit in summer, while copper, lead, nickel, and arsenic exceeded the limit in winter. Principal component analysis (PCA) results revealed that the metals responded positively and negatively among various harboring sampling sites The present study establishes the grave concern about heavy metal concentrations in the Digha coastal ecosystem and human health which are closely associated and dependent on it.

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.

Variations in chlorophyll-a concentration in response to hydrodynamics in a flow-through lake: Remote sensing and modeling studies

A convolution neural network (CNN) machine learning algorithm is established for Chlorophyll-a retrieval in Poyang Lake using in-situ Chlorophyll-a concentrations and concurrent satellite image data. For comparison, other machine learning methods, e.g., deep neural network, XGBoost, random forest, gradient boost, decision tree, and linear regression, are also employed, together with two empirical models. Accuracy analysis validates the robustness of the CNN algorithm, with the R2 of 0.97 and the mean absolute errors of 1.74 μgL−1, and its performance is better than other machine learning and empirical algorithms. The Chl-a in Poyang Lake is derived from Sentinel-2 Multi-Spectral Instrument (MSI) images based on the robust CNN algorithm. As a follow-through type, Poyang Lake has abundant hydrodynamics affecting the Chl-a in the lake water. Thus, the Delft3D Flexible Mesh (FM) model is employed in Poyang Lake to simulate the active hydrodynamics with a high spatial resolution (∼80 m) under the realistic forcing in the period from 1 October 2020 to 15 March 2022. The simulation results reveal that the flow speed is a significant factor modulating the lake Chl-a with a high concentration in summer and a low concentration in winter; the flow speed and water storage exceed the temperature and solar radiance in modulating the Chl-a. The jacking effect of the Yangtze River can slow down the flow speed in the lake’s north channel, therefore, augmenting the Chl-a by ∼20%, favoring phytoplankton blooms in Poyang Lake. The active eddies may significantly affect the lake Chl-a; cyclonic eddies enhance the local Chl-a, and anticyclonic eddies weaken the Chl-a. A detailed analysis indicates that the Coriolis force plays a vital role in the momentum balance, which may cause the lift (restriction) of bottom nutrients in the cyclonic (anticyclonic) eddy area, increasing (decreasing) the surface nutrient supply. This study uses Poyang Lake as an example to show that such eddies conventionally appearing in a flow-through lake may dramatically affect the ecological environment in the lake water.

Vertical distribution of airborne microorganisms over forest environments: A potential source of ice-nucleating bioaerosols

Airborne microorganisms transported from forested areas can influence cloud formation by forming ice nuclei. However, the vertical transportation of airborne microorganisms over forested areas is not well understood. We collected aerosols at three heights, [ground (2 m), canopy top (20 m), and above canopy (500 m)] during the summer, fall and winter, to analyze the airborne microbial communities that were distributed vertically over the forest. During summer and fall, the microbial particles maintained similar concentrations in the forest zone (canopy top and ground) and decreased to 1/10th of the microbial concentration in the above canopy area. The particle concentrations in winter indicated efficient vertical mixing below 500 m. High-throughput DNA sequencing revealed that the airborne microbial communities were composed of terrestrial and phyllospheric species associated with the degradation of decaying plant litters. Regardless of the three seasons, the above canopy was dominated by atmospheric stress-resistant bacteria from the phyla Actinobacteria and Firmicutes. Unlike bacteria, the mushroom-type fungal members of Agaricomycetes grew in relative abundance above the canopy, primarily throughout the summer and winter, while mold-type fungal Dothideomycetes species were often found at all three heights during the fall. The Fusarium, Pseudomonas, and Bacillus isolates, which were obtained from air samples at three heights, indicated high activities of ice nucleation in the water-drop freezing assay. Therefore, ice-nucleating microbial taxa likely originated from fungal and bacterial communities in the soil litter and plant surfaces of the phyllospheric environments.

Distribution and Long-Term Trends of Tropospheric Ozone Concentrations in Ireland

Tropospheric ozone (O3) is highly variable over space and time reflecting local production and destruction as well as addition and loss through regional and long-range transport. In this study, O3 concentrations at 11 stations in Ireland and their long-term trends (7–9 sites) were evaluated; O3 concentrations (2015–2019) varied spatially, with the highest annual mean concentrations along the Atlantic west coast (69–75 µg/m3), and the lowest in urban centres (39–43 µg/m3). Ozone followed a seasonal pattern of spring and winter maximum and summer–autumn minimum. Significant long-term (2005–2019) increases were observed in annual O3 concentration at two rural stations, while increases were larger and more frequent during winter with increases at four out of seven stations. During the decade 2010–2019, significant annual increases were observed at four out of nine stations. Observed site- and season-specific increasing trends in O3 concentrations likely reflected changes in regional precursor gas emissions sources. Despite reported decreases in background concentrations in the marine boundary layer in northern mid-latitudes in recent decades, O3 concentrations at some sites in Ireland have increased significantly primarily driven by changes in winter concentrations. There were no significant decreasing trends at any site or in any season.