Order Of Winter Research Articles

Spatiotemporal Distribution Characteristics of Co-pollution of PM2.5 and Ozone over BTH with Surrounding Area from 2015 to 2021

PM2.5 and ozone co-pollution, which are harmful to not only human health but also the social economy, has become the pivotal issue in air pollution prevention and synergistic control, especially in Beijing-Tianjin-Hebei and its surrounding areas and "2+26" cities. It is necessary to analyze the correlation between PM2.5 and ozone concentration and explore the mechanism of PM2.5 and ozone co-pollution. In order to study the characteristics of PM2.5 and ozone co-pollution in Beijing-Tianjin-Hebei with its surrounding area, ArcGIS and SPSS software were used to analyze the correlation between air quality data and meteorological data of the "2+26" cities in Beijing-Tianjin-Hebei and its surrounding areas from 2015 to 2021. The results indicated:① PM2.5 pollution constantly decreased from 2015 to 2021, and the pollution was concentrated in the central and southern parts of the region; ozone pollution showed a trend of fluctuation and presented a pattern of "low in the southwest and high in the northeast" spatially. In terms of seasonal variation, PM2.5concentration was mainly in the order of winter>spring ≈ autumn>summer, and O3-8h concentration was in the order of summer>spring>autumn>winter. ② In the research area, days with PM2.5 exceeding the standard continued to decline, whereas days with ozone exceeding the standard fluctuated, and days with co-pollution decreased significantly; there was a strong positive correlation between PM2.5 and ozone concentration in summer, with the highest correlation coefficient of 0.52, and a strong negative correlation in winter. ③ Comparing the meteorological conditions of typical cities during the ozone pollution period with that of the co-pollution period, the co-pollution occurred under the temperature range of 23.7-26.5℃, humidity of 48%-65%, and S-SE wind direction.

Secondary formation and source analysis of carbonaceous components in PM1 in a typical city, Southwest of China

Carbonaceous components are major components of PM1, which have a significant impact on climate change, air quality and human health. However, the secondary formation and source analysis of carbonaceous components in PM1 are still unclear. Therefore, in order to study the secondary formation and sources of carbonaceous components in PM1, PM1 samples were collected in Chengdu, a typical city located in southwest of China, from 2018 to 2019. The concentrations of organic carbon (OC), elemental carbon (EC) and isotopic compositions of carbon (δ13C) in PM1 were determined using a thermal/optical carbon analyzer and elemental analyzer-isotope ratio mass spectrometer. In addition, the δ13C values from relevant potential sources (C3 plants, C4 plants, vehicle exhaust and coal) were also determined. The results showed that the annual average concentrations of OC and EC in PM1 in Chengdu were 6.43 ± 3.30 μg·m−3 and 1.99 ± 0.98 μg·m−3, accounting for 13.83% and 4.28% of the PM1 mass concentration, respectively. The concentrations of OC in PM1 ranked in the order of winter > summer > spring > autumn, while the concentrations of EC varied in the order of winter > spring > autumn > summer. The concentrations of OC and EC in PM1 reached the maximum in winter, mainly due to the special meteorological conditions and significantly higher pollutant emissions. The correlations of OC and EC were higher in spring, autumn and winter, and lower in summer. It showed that OC and EC might have the same sources in spring, autumn and winter, while the sources of OC and EC were relatively complex in summer. The annual average concentration of secondary organic carbon (SOC) in PM1 was 2.23 ± 1.22 μg·m−3. The concentrations of SOC were higher in autumn and winter and lower in spring and summer. The special meteorological conditions and significantly higher pollutant emissions are important reasons for the higher SOC concentrations in winter. On the other hand, the low temperature in winter can also promote the formation of SOC. The results of carbon isotopic compositions indicated that the carbonaceous components in PM1 were mainly derived from vehicle exhaust (52.4%), C3 plants combustion (26.2%), coal burning (16.2%) and C4 plants combustion (5.2%). The findings help to deepen the understanding of the secondary formation and sources of carbonaceous components in PM1 and provide theoretical guidance for environmental management.

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.

Deposition, dissipation, metabolism and dietary risk assessment of chlorothalonil in open field-planted cabbage

Chlorothalonil is a fungicide commonly used to prevent and control leafy vegetable diseases. The residual distribution of chlorothalonil on cabbage is unclear and rarely reported. The spatiotemporal distribution of chlorothalonil was used to understand its environmental behavior in cabbage. The results of open-field experiments demonstrated that chlorothalonil was distributed primarily on the second and third layers of rosette leaves and the first layer of bulb leaves. The chlorothalonil residues on cabbage followed the order of winter > fall > summer, and heading stage > rosette stage > seedling stage. Chlorothalonil on cabbage underwent −OH substitution forming 4-hydroxychlorothalonil, and reductive dechlorination forming 2,4,5-trichloro-1,3-isophthalonitrile, 2,5-dichloro-1,3-isophthalonitrile, and 5-chloro-1,3-isophthalonitrile. The residues of chlorothalonil in the outermost leaves of cabbage bulb pose an unacceptable risk to human health via dietary exposure. This study contributes to better understanding on the fate and transformation chlorothalonil in cabbage and potential risks to human health via dietary consumption.

Characteristics, evolution, and potential source regions of submicron aerosol in Beijing, China

Atmospheric fine particulate pollution has been a dramatically environmental concern in all seasons in the megacity Beijing in recent years. A long-term real-time monitoring campaign of non-refractory submicron aerosol (NR-PM1) at a southeastern urban site in Beijing from July 13, 2017 to May 26, 2018 using an Aerodyne Aerosol Chemical Speciation Monitor (ACSM) was carried out to investigate the characteristics and evolution processes of NR-PM1 and its potential source effects. The annual average concentration of NR-PM1 during the entire study period was 40.8 μg/m3, lower than that of NR-PM1 from July 2011 to June 2012, and its seasonal variation presented the order of autumn and spring > winter > summer. The average concentration of organic species Org in the entire study was 15.1 μg/m3 and accounted for 37% of NR-PM1, being consistently a significant component of NR-PM1 in the four seasons. The average concentrations of SO42− and NO3− were 8.6 and 11.1 μg/m3, respectively, accounting for 21% and 27% of NR-PM1, and NO3− and its contribution to NR-PM1 exceeded those of SO42−, suggesting that secondary nitrate became a more dramatic pollutant. Note that SO42− in summer accounted for 27% of NR-PM1, higher than those in the other seasons, indicating that secondary sulfate formation was greatly important in summer, however, NO3− in summer accounted for 22% of NR-PM1, lower than those in the other seasons, more likely due to relatively high temperature in summer being favorable for dissociation of nitrate. NH4+ and Cl− species presented lower mass concentrations and mass fractions, and the seasonal variation of NH4+ was similar to NO3−, yet Cl− presented a typical seasonal change related to intense fossil fuel combustion during the heating period in winter and biomass burning in autumn with an order of winter > autumn > spring > summer. All aerosol species exhibited different diurnal cycles, of which Org presented a bimodal mode, SO42− and Cl− showed a flatter diurnal pattern, however, NO3− and NH4+ displayed more similar single-peak patterns. The conversion of SO2 to SO42− presented an obvious seasonal variation with summer > autumn > spring > winter driven by different factors. The conversion of NO2 to NO3− also showed a significant seasonal change characterized by autumn > summer and spring > winter controlled by different factors. Relative humidity, temperature and wind speed during the study period were significant meteorological elements influencing NR-PM1 and its species, and heavy haze pollution episodes largely occurred under high relative humidity and low wind speed. High potential source regions influencing NR-PM1 pollution in Beijing in all seasons presented dramatically distributions related to wind directions.

Seasonal Chemical Composition Characteristics and Source Apportionment of PM2.5 in Zhengzhou

The aim of this study was to fully understand the pollution characteristics and sources of PM2.5 in Zhengzhou, and to investigate the differences in four seasons and between urban and suburban areas. At the Zhengzhou environmental monitoring center (urban areas) and Zhengzhou University (suburban areas), 1284 environmental PM2.5 samples were collected in the four seasons of 2018. The concentrations of nine kinds of inorganic water-soluble ions, organic carbon, elemental carbon and 27 kinds of elements, were measured by ion chromatography, carbon analyzer, and X-ray fluorescence spectrometry, respectively. Enrichment factors (EF), index of geoaccumulation (Igeo), potential ecological risk index (RI), chemical mass balance model (CMB), backward trajectory, and potential source contribution function were the methods used to study the chemical component characteristics and source differences of PM2.5 in different seasons in the urban and suburban areas of Zhengzhou. The results showed that the annual average PM2.5 concentration at the Zhengzhou environmental monitoring center and Zhengzhou University sites reached (59.7±24.0) μg·m-3 and (74.7±13.5) μg·m-3, respectively. The PM2.5 concentration at the suburban point was higher than at the urban point with the exception of winter, and the seasonal mean concentration decreased in the order of winter > autumn > spring > summer. Compared with the urban areas, the suburban areas were more affected by crustal substances in spring, and the concentrations of all components were higher in summer and autumn than the urban areas. Nevertheless, urban areas were more affected by coal burning sources and motor vehicle sources in winter. The component analysis results showed that the influences of soil dust and building dust were greater in the suburbs in spring than in the urban areas. In autumn, the suburbs were more affected by biomass sources than the urban areas, while the urban areas were more affected by building dust than were the suburbs. The concentrations of Cu, As, Zn, Pb, and Sb were strongly influenced by anthropogenic sources, and the enrichments of Zn, Cu, As, and Pb in urban areas were greater than in the suburbs. In addition, Zn, Cu, As, and Pb exhibited potential ecological risks. The outcomes of the CMB model showed that dust sources, secondary sulfate, secondary nitrate, and coal burning sources contributed significantly to PM2.5 concentrations in spring, summer, autumn and winter, respectively. The contributions of secondary pollution sources (secondary organic aerosol, secondary sulfate, and secondary nitrate) and motor vehicle sources to urban areas were higher than to suburban areas, and the influences of biomass sources in autumn and winter were significantly higher than in spring and summer and urban areas. The backward trajectory results indicated that the local PM2.5 concentration was affected by distant transmission from the northwest except in summer, was affected by neighboring provinces in the east in four seasons, and was affected by transmission from the south, with the exception of winter. Furthermore, the consequences of potential sources demonstrated that the local PM2.5 concentration was mainly affected by the potential areas in Henan province and its boundary with neighboring provinces.

Characterization of black carbon aerosol in the Yangtze River Delta, China: Seasonal variation and source apportionment

As a crucial absorptive component of aerosols, black carbon (BC) plays a key role in modifying the planetary boundary layer (PBL) meteorology and hence aggravating the haze pollution. In this study, using the seven-channel Aethalometer model AE-33, the equivalent BC aerosols were continuously observed for one year in a typical city of Nanjing in the Yangtze River Delta (YRD). Together with the pollutant data of PM2.5 and trace gases (NO2, SO2, CO and O3), and the methods of potential source contribution function (PSCF) and concentration weighted trajectory (CWT) models, the spatiotemporal distribution and source apportionment of BC mass concentrations in Nanjing are discussed. It had large discrepancies in monthly and seasonal variations of BC concentrations, which were found to be the highest in December (3109.4 ± 1875.0 ng m−3) and the lowest in September (1300.8 ± 1031.6 ng m−3). Meanwhile, the BC concentrations ranked in the order of winter (2619.5 ± 1576.8 ng m−3) > spring (2142.4 ± 1219.3 ng m−3) > summer (1645.6 ± 1229.7 ng m−3) > autumn (1583.1 ± 1333.1 ng m−3). The diurnal variation of BC exhibited bimodal distributions in four seasons, peaking at 07:00–09:00 and 20:00–23:00, respectively. Fossil fuel BC (BCff) was calculated to contribute 71–77% to BC concentration. Long-range transport of BC was noticed mainly across inland China of North China Plain (NCP) and Twain-Hu regions in winter, and from the eastern YRD and southern PRD regions in summer. Overall, BC in Nanjing mainly originated from the surrounding cities in YRD, which had a maximum contribution more than 2000 ng m−3. The potential sources of BC varied significantly in the four seasons.

Analysis of Characteristics of Water-soluble Ions in PM2.5 in Chengdu Based on the MARGA

Water-soluble ions in PM2.5 were serially on-line monitored using the MARGA sampling and measurement system in Chengdu in 2019. Pollution characteristics of water-soluble ions were analyzed using the meteorological monitoring data. The results show that variations in the concentrations of eight water-soluble ions were consistent with the variations in PM2.5 in Chengdu. The annual average mass concentration of the total water-soluble ions was (20.2±12.7) μg ·m-3, accounting for 48.6% of the PM2.5 mass, which indicates that water-soluble ions were the major components of PM2.5. The mass concentrations of all the ions were in the order of NO3- > SO42- > NH4+ > Cl- > Ca2+ > K+ > Mg2+ > Na+. The annual average mass concentration of secondary ions was (20.2±12.7) μg ·m-3, accounting for 87.2% of total water-soluble ions. The concentrations of total water-soluble ions in different seasons were in the order of winter > spring ≈ autumn > summer. Monthly variations in total water-soluble ion concentrations followed a U-shaped curve; mass concentrations were the highest in January and December and lowest from June to August. Monthly variations in the concentrations of NO3-, SO42-, NH4+, Cl-, Na+, and K+ were consistent with the total water-soluble ion concentrations, while the concentrations of Ca2+ and Mg2+ were the highest in June. Visibility declined with the increase in the concentration of water-soluble ions, especially secondary water-soluble ions regardless of the rainfall. Light rain (accumulated rainfall in 24 h <10 mm) had no scavenging effect on water-soluble ions, while moderate and heavy rainfall had a significant effect. There was a significant positive correlation between NO3-, SO42-, and NH4+ (all the correlation coefficients were over 0.7), indicating that the mechanisms of evolution of secondary water-soluble ions in the atmosphere are highly similar to each other. The annual mean values of SOR and NOR were 0.42 and 0.12, respectively, which were negatively correlated with temperature and O3 and positively correlated with humidity, indicating that the main source of SO42- was heterogeneous oxidation reactions in the liquid phase and the main source of NO3- was heterogeneous oxidation reactions at night. The annual mean values of CE/AE and NR were 1.2 and 1.1, respectively, indicating that most aerosols in the study area were relatively alkaline. The atmospheric environment of Chengdu is rich in ammonia; thus, (NH4)2 SO4 and NH4NO3 were the main forms of secondary ions.

Long-term characteristics of criteria air pollutants in megacities of Harbin-Changchun megalopolis, Northeast China: Spatiotemporal variations, source analysis, and meteorological effects

The hourly concentration of six criteria air pollutants in the Harbin-Changchun region were used to investigate the status and spatiotemporal variation of target air pollutants and their relationships with meteorological factors. The annual concentrations of particulate matters during 2013–2017 were two times higher than the Chinese Ambient Air Quality Standards (CAAQS) Grade Ⅱ. The annual O3 concentration increased by two times during 2013–2018 in Harbin. The concentration of PM, SO2, NO2, and CO depicted a similar seasonal trend with an order of winter > autumn > spring > summer. The consistent interannual variation trends of PM2.5/CO, NO2 and SO2 indicated that the formation of secondary inorganic aerosols in the annual scale was dominated by the concentrations of NO2 and SO2. The interannual variations of the individual meteorological factors causing on PM2.5 and O3 during 2013–2018 varied significantly in seasonal scale. The interannual variations were stable in annual scale indicating that the continuous decline of PM2.5 during 2014–2018 can be attributed to the comprehensive and strict prohibition of small coal-fired boilers and straw burning in the study area. Meanwhile, the increase in O3 during 2013–2018 in the study area were mainly attributed to the rapid growth of the emission of its precursor (VOCs and NOx). The influence of meteorology on PM2.5 and ozone were the most stable and strongest in winter than that in the other three seasons.

Biological denitrification in a macrophytic lake: implications for macrophytes-dominated lake management in the north of China

Denitrification plays an important role in nitrogen (N) removal in freshwater ecosystems. Aquatic plants might have an impact on the sediment denitrification of water body, especially in macrophytes-dominated lake; however, there were different opinions about it. Our hypothesis was that the sediment denitrification rates differ significantly in different vegetation zones and seasons because of direct and indirect effect of the aquatic plants. Therefore, we studied sediment denitrification in Dongping Lake, a typical macrophytes-dominated lake located in the north of China. The acetylene inhibition technique was used to quantify the sediment denitrification rates (DRs) in the Phragmites communis (P. communis) zone, aquaculture zone, Potamogeton crispus (P. crispus) zone and mixed vegetation zone in July (summer), October (autumn), December (winter) of 2015 and March (spring) of 2016. The results showed that the average DRs were significantly higher in the P. communis zone (69.0 ± 91.6μmolNm-2h-1) than the mixed vegetation zone (8.70 ± 5.44μmolNm-2h-1), and the average DRs represented significant seasonal difference as in the order of winter (74.5 ± 88.3μmolNm-2h-1) > autumn (15.7 ± 18.6μmolNm-2h-1) ≈ summer (10.7 ± 5.90μmolNm-2h-1) > spring (3.85 ± 1.29μmolNm-2h-1). The DRs generally decreased with the increasing of depth; however, significant increase of DRs with depth were found in certain seasons at the vegetated zones except the non-vegetated zone (the aquaculture zone) indicating the possible rhizosphere effect of aquatic plants on denitrification. The higher DRs and cycling rates of nitrate in the P. communis zone might be related to the larger biomass and oxygen transporting capacity of P. communis than those of the other aquatic plants. Winter peaks of DRs might be attributed to the higher NO3- load and the absence of the plant uptake. The high cycling rates of nitrate in Dongping Lake indicated an enhanced internal N cycling by aquatic plants. Sediment denitrification could remove about 537.7tN every year, which was about 26.5% of annual TN loading in Dongping Lake.

Source Characteristics of Atmospheric CO2 and CH4 in a Northeastern Highland Area of South Korea

This study aims to present the atmospheric CO2 and CH4 levels and analyze their source characteristics at an observation station in a northeastern highland area of Korea for the 2012–2014 period. We summarized the measured CO2 and CH4 concentrations for the 2012–2014 period. In addition, we characterized the major source of the rise of CO2 and CH4 in Ganseong (GS) by employing bivariate polar plots (BPP) and the concentration weighted trajectory (CWT) method together with currently available information on emission sources. For the three years, CO2 was generally high in the order of winter, spring, autumn and summer and CH4 high in the order of winter, autumn, spring and summer. The observed positive correlations between the hourly CO2 and CH4 in every season suggested the possibility of shared common emission sources, but there is a necessity for elucidation on this in the future. The BPP analysis indicated the local sources that are likely to be associated with the rise of greenhouse gases (GHGs) observed at GS (combustion in the village, plant respirations nearby GS, and mobile emissions on the nearby road for CO2 and leakages from the gas stations along the road and agricultural activities for CH4). Synthesizing the CWT results together with emission source information from national and global emission inventories, we identified likely major source areas and characterized major emission sources. For example, the identified major sources for the winter CO2 are coal combustion, coal washing and industrial activities in Inner Mongolia, northern and the northeastern China, fuel burning for the energy for the infrastructure of a northwestern city in South Korea, and the manufacturing industry and fuel combustion in the northern parts of North Korea. Hopefully, these kinds of results will aid environmental researchers and decision-makers in performing more in-depth studies for GHG sources in order to derive effective mitigation strategies.

Two years measurement of speciated atmospheric mercury in a typical area of the north coast of China: Sources, temporal variations, and influence of regional and long-range transport

Abstract Measurements of speciated atmospheric mercury (Hg) were conducted at the Changdao Island from October 2013 to July 2015 to characterize their seasonal and diurnal patterns, to identify the relationships between atmospheric Hg and meteorological parameters as well as trace gases, and furthermore to verify the potential sources of atmospheric Hg. There was a seasonal variation of gaseous elemental Hg (GEM) with the order of winter (2.87 ± 1.16 ng m−3), spring (2.58 ± 0.84 ng m−3), summer (2.25 ± 0.51 ng m−3), and fall (2.15 ± 0.39 ng m−3). The mean GEM value (2.52 ± 0.82 ng m−3) in the Changdao Island was about 1.7 times higher than that in the Northern Hemisphere, indicating that the Changdao and peripheral regions were polluted to some extent. Gaseous oxidized Hg (GOM) shows a clear seasonal variation with the highest value in summer (12.2 ± 9.4 pg m−3) and the lowest value in winter (4.6 ± 4.2 pg m−3). Moreover, the mean GOM concentration was significantly higher in daytime (11.9 ± 9.4 pg m−3) than in nighttime (6.3 ± 4.8 pg m−3) mainly due to the influence of solar radiation. In contrast, fine particulate Hg (HgP2.5) exhibited a distinct seasonal trend opposite to that of GOM. There was no significant difference between daytime HgP2.5 concentration (25.6 ± 23.9 pg m−3) and nighttime concentration (30.4 ± 31.2 pg m−3). The size distribution of HgP in PM10 was observed to be one-modal with the peak around the range of 1.1–2.1 μm in the winter, while it was bi-modal with a higher peak in the range of 1.1–2.1 μm and a lower peak in the range of 4.8–5.9 μm in other seasons. Generally, more than half of HgP was concentrated on fine particles (PM2.1). The temporal variation pattern of PM2.5/PM10 ratio was similar to those of HgP2.1/HgP10 or HgP3.3/HgP10. This further supports that HgP is mainly concentrated in fine particles. Correlation analysis shows that the GEM was positively correlated with SO2 and NO2. The average dry deposition flux of HgP10 was calculated to be 4.76 ng m−2 d−1 with a range of 0.86–13.46 ng m−2 d−1 based on all the size-fractionated HgP over the Changdao Island. This indicates that the dry deposition of HgP is an important part of atmospheric Hg deposition in coastal region because it happens all the time.

Characteristics, toxicity, source identification and seasonal variation of atmospheric polycyclic aromatic hydrocarbons over East India.

Atmospheric PM2.5-bound polycyclic aromatic hydrocarbons (PAHs) were analyzed over urban and rural sites during January to December 2018. Total annual average concentration of PM2.5 was 74.41 ± 24.96 μg/m3 over urban and 52.03 ± 13.11 μg/m3 over rural site during study time. The annual average concentration of PM2.5 over urban and rural atmospheres were found approximately twice in urban and found also higher over rural site, with respect to National Ambient Air Quality (NAAQ) standard of 40 μg/m3 for PM2.5 concentration. The annual concentration of PAHs was 750.80 ± 19.49 ng/m3 over urban, and, over rural, it was 559.59 ± 17.56 ng/m3. The seasonal variation of concentration of PAHs was in order of winter > post-monsoon > summer > monsoon. The most predominant PAHs were IcP (17.21%), B(ghi) P(15.22%), BkF (11.60%), DBahA (11.34%) and BbF (10.91%) to the total PAH concentration over urban site; over rural site, most predominant PAHs were IcP (16.02%), B(ghi)P, (15.63%), BkF (11.46%), DBahA (11.12%) and BbF (8.99%) of total PAHs. DBahA concentration was contributed approximately 46% carcinogenicity over both urban and rural sites, and BaP contributes 33.56% carcinogenicity over urban site and 34.62% carcinogenicity over rural site of total PAH samples. The Excess Life Time Cancer Risk (ELCR) values over urban were found at acceptable limit 10-6-10-4 given by the United States Environmental Protection Agency. Over rural site, the ELCR value was found near about acceptable limit. Diagnostic ratio analysis demonstrated that major sources of PAHs were pyrogenic sources and vehicular emission over study. Air parcel through trajectories over study site also contributed in PAH concentration.

Estimation of baseflow nitrate loads by a recursive tracing source algorithm in a rainy agricultural watershed

AbstractBaseflow has become an important source of nitrate nonpoint source pollution in many intensive agricultural watersheds. Uncertainties in baseflow nutrient load separation are caused by the effects of hydrometeorological factors on both baseflow recession and baseflow nutrient load recession. These uncertainties have not been addressed well in the existing separating algorithms, which are based on simple baseflow rate–load relationships. In the present study, a recursive tracing source algorithm (RTSA) was developed based on a nonlinear reservoir algorithm and hydrometeorology‐corrected baseflow nutrient load recession parameter. This approach was used to reduce the uncertainty of baseflow nitrate load estimation caused by variations in different load recessions under varying climate conditions. RTSA validation in a typical rainy agricultural watershed yielded Nash–Sutcliffe efficiency, root mean square error‐observation standard deviation ratio, and R2 values of 0.91, 0.30, and 0.91, respectively. The baseflow nitrate–nitrogen (N─NO3–) loads from 2003 to 2012 in the Changle River watershed of eastern China were estimated with the RTSA. The results indicated that baseflow nitrate export accounted for 62.0% of the mean total annual N─NO3– loads (18.0 kg/ha). The total baseflow N─NO3– export was highest in spring (3.6 kg/ha), followed by summer (3.2 kg/ha), winter (2.3 kg/ha), and autumn (2.1 kg/ha). The contribution of baseflow to total nitrate in the stream decreased in the order of winter (69.88%) &gt;spring (66.59%) &gt;autumn (60.36%) &gt;summer (54.04%). The monthly baseflow N─NO3– loads and flow‐weighted concentrations greatly increased during the research period (Mann–Kendall test, Zs &gt; 2.56, p &lt; .01). Without proper countermeasures, baseflow nitrate may represent a serious long‐term risk for water surfaces in the future.

Wet deposition of inorganic ions in 320 cities across China: spatio-temporal variation, source apportionment, and dominant factors

Abstract. The acid deposition has been considered to be a severe environmental issue in China. The pH, electrical conductivity (EC), and concentrations of water soluble ions (NO3-, Cl−, Ca2+, K+, F−, NH4+, Mg2+, SO42-, and Na+) in the precipitation samples collected from 320 cities during 2011–2016 across China were measured. The mean concentrations of F−, NO3-, and SO42- were in the order of winter (6.10, 19.44, and 45.74 µeq L−1) &gt; spring (3.45, 13.83, and 42.61 µeq L−1) &gt; autumn (2.67, 9.73, and 28.85 µeq L−1) &gt; summer (2.04, 7.66, and 19.26 µeq L−1). Secondary ions (SO42-, NO3-, and NH4+) and F− peaked in the Yangtze River Delta (YRD) and Sichuan basin (SB). Crustal ions (i.e. Ca2+, Mg2+), Na+, and Cl− showed the highest concentrations in the semi-arid regions and the coastal cities. The statistical methods confirmed that the mean anthropogenic contribution ratios to SO42-, F−, NO3-, and NH4+ at a national scale were 46.12 %, 71.02 %, 79.10 %, and 82.40 %, respectively. However, Mg2+ (70.51 %), K+ (77.44 %), and Ca2+ (82.17 %) mostly originated from the crustal source. Both Na+ (70.54 %) and Cl− (60.42 %) were closely linked to sea salt aerosols. On the basis of the stepwise regression (SR) analysis, it was proposed that most of the secondary ions and F− were closely related to gross industrial production (GIP), total energy consumption (TEC), vehicle ownership, and N fertilizer use, but the crustal ions (Ca2+ and K+) were mainly controlled by the dust events. The influence of dust days, air temperature, and wind speed on ions increased from southeast China (SEC) to central China, and then to northwest China (NWC), whereas the influence of socioeconomic factors on acid ions (SO42- and NO3-) displayed the higher value in east China.

Polycyclic aromatic hydrocarbons in atmospheric PM2.5 and PM10 in the semi-arid city of Xi'an, Northwest China: Seasonal variations, sources, health risks, and relationships with meteorological factors

Atmospheric particulate matter (PM2.5 and PM10) samples were collected at urban and suburban sites in Xi'an City from December 2016 to November 2017. Sixteen priority polycyclic aromatic hydrocarbons (PAHs) associated with PM2.5 and PM10 were analyzed for their seasonal variations, sources, health risks, and influencing factors. The results showed that the annual average concentrations of PM2.5 and PM10 were 111 and 185 μg/m3, respectively, exceeding the National Ambient Air Quality Standard of China (35 μg/m3 for PM2.5 and 70 μg/m3 for PM10 in Grade II). The annual averages of PM2.5- and PM10-bound total PAHs were 63.1 and 66.8 ng/m3, respectively, with a PM2.5 decrease in the order of winter (115 ng/m3) > > spring (47.6 ng/m3) > summer (33.2 ng/m3) > autumn (30.8 ng/m3) and a PM10 decrease in the order of winter (127 ng/m3) > > spring (55.6 ng/m3) > autumn (32.6 ng/m3) > summer (30.2 ng/m3). The most abundant PAHs were benzo[a]anthracene, benzo[b]fluoranthene, and fluoranthene. The PM2.5- and PM10-bound PAHs were originated mainly from traffic emissions (51.0% and 43.4%), followed by combustion of biomass (20.4% and 23.6%) and coal (16.8% and 23.1%). Pressure and relative humidity were positively correlated with PM2.5 and PM10 as well as PM2.5- and PM10-bound PAHs, while temperature, visibility and wind speed had negative correlations. The annual means of TEQs (toxic equivalency quantities) for the 16 PAHs in PM2.5 and PM10 were 10.1 and 10.2 ng/m3, respectively, being attributed to 7 carcinogenic PAHs (> 95%). The ECRs (lifetime excess cancer risks) for PM2.5- and PM10-bound PAHs were 1.12 × 10−3 and 1.17 × 10−3, i.e., 1125 and 1169 lung cancer cases per million, respectively. The ILCRs (incremental lifetime cancer risks) due to PM2.5- and PM10-bound PAHs for adults (1.21 × 10−6 and 1.26 × 10−6) were larger than those for children (2.09 × 10−7 and 2.17 × 10−7), with acceptable carcinogenic risks. The ambient levels of PM and most PM-bound PAHs as well as their TEQs, ECRs and ILCRs exhibited a spatial pattern of the suburban site > the urban site and a seasonality with winter and spring > summer and autumn. The results suggest that it is important to control PM2.5 and PM10 for local air quality improvement and special attention should be paid to PM and PM-bound PAHs in suburban areas, particularly in winter and spring.

Neutral Processes Drive Seasonal Assembly of the Skin Mycobiome.

The importance of microorganisms to human skin health has led to a growing interest in the temporal stability of skin microbiota. Here we investigated the dynamics and assembly of skin fungal communities (mycobiomes) with amplicon sequencing of samples collected from multiple sites on 24 healthy Chinese individuals across four seasons (in the order of winter, spring, summer, and autumn in a calendar year). We found a significant difference in community compositions between individuals, and intrapersonal community variation increased over time at all body sites. Within each season, the frequency of occurrence of most operational taxonomic units (OTUs) was well fitted by a neutral model, highlighting the importance of stochastic forces such as passive dispersal and ecological drift in skin community assembly. Despite the significant richness contributed by neutrally distributed OTUs, skin coassociation networks were dominated by taxa well-adapted to multiple body sites (forehead, forearm, and palm), although hub species were disproportionately rare. Taken together, these results suggest that while skin mycobiome assembly is a predominantly neutral process, taxa that could be under the influence of selective forces (e.g., host selection) are potentially key to the structure of a community network. IMPORTANCE Fungi are well recognized members of the human skin microbiota and are crucial to cutaneous health. Common cutaneous diseases such as seborrheic dermatitis and dermatophytes are linked to fungal species. Most studies related to skin microbial community dynamics have focused on Western subjects, while non-Western individuals are understudied. In this study, we explore the seasonal changes of the skin mycobiome in a healthy Chinese cohort and identify ecological processes that could possibly give rise to such variations. Our work reveals the dynamic nature of host skin fungal community, highlighting the dominant roles neutral forces play in the seasonal assembly of skin mycobiome. This study provides insight into the microbial ecology of the human skin microbiome and fills a knowledge gap in the literature regarding the dynamics of skin fungal community.

Chemical Composition and Source Apportionment of PM2.5 in Urban Areas of Xiangtan, Central South China.

Xiangtan, South China, is characterized by year-round high relative humidity and very low wind speeds. To assess levels of PM2.5, daily samples were collected from 2016 to 2017 at two urban sites. The mass concentrations of PM2.5 were in the range of 30–217 µg/m3, with the highest concentrations in winter and the lowest in spring. Major water-soluble ions (WSIIs) and total carbon (TC) accounted for 58–59% and 21–24% of the PM2.5 mass, respectively. Secondary inorganic ions (SO42−, NO3−, and NH4+) dominated the WSIIs and accounted for 73% and 74% at the two sites. The concentrations of K, Fe, Al, Sb, Ca, Zn, Mg, Pb, Ba, As, and Mn in the PM2.5 at the two sites were higher than 40 ng/m3, and decreased in the order of winter > autumn > spring. Enrichment factor analysis indicates that Co, Cu, Zn, As, Se, Cd, Sb, Tl, and Pb mainly originates from anthropogenic sources. Source apportionment analysis showed that secondary inorganic aerosols, vehicle exhaust, coal combustion and secondary aerosols, fugitive dust, industrial emissions, steel industry are the major sources of PM2.5, contributing 25–27%, 21–22%, 19–21%, 16–18%, 6–9%, and 8–9% to PM2.5 mass.

Indoor inhalation dose assessment for thoron-rich regions of Indian Himalayan belt.

222Rn, 220Rn, and their decay products are significant contributors to background radiation dose. Their concentration level, pertaining exposure, and consequent dose are prime concerns in indoor environments. The present study was performed in 101 dwellings of different villages of Almora district situated in Kumaun hills of Indian Himalayan belt. Measurement of gases and decay products were made in three different types of dwellings (i.e., mud, cemented, and stone with plaster) in three seasons (winter, summer, and rainy). Concentration values for 222Rn and EERC were found to be varying in the order of winter > summer > rainy while obtained least in rainy season for the case of 220Rn and EETC. Concentration values for 222Rn and EERC were found to be lesser for cemented houses. Relative standard deviation of concentration values was found to be higher for the rainy season. Yearly averaged concentration values for 222Rn, EERC, 220Rn, and EETC were noted to be higher than the global averages but comparable to some Indian studies. Annual inhalation dose due to 222Rn, 220Rn, and their progeny was found to be 0.55-4.71mSv/year with an average value of 2.36 ± 0.83mSv/year. These values were measured for the first time in the study area and provide a link for future studies in the dwellings representing higher concentration values.

Dust uplift potential in the Taklimakan Desert: an analysis based on different wind speed measurement intervals

A wind speed data set at a temporal resolution of 1 min, observed in the hinterland of the Taklimakan Desert (Tazhong) from September 1, 2008, to August 31, 2010, was used to investigate the diurnal and seasonal cycles of high wind speeds and dust uplift potential (DUP), and to investigate the effect of wind speed measurement time on the DUP in different seasons. The results suggested that high wind speeds, i.e., greater than the threshold wind velocity (TWV) for wind erosion, mainly occurred during the daytime (08:00–20:00) and the frequency of wind speeds above the TWV exhibited a large variability from season to season: spring (6.4%) > summer (5.6%) > autumn (1.7%) > winter (0.8%). The cumulative DUP was 50% on June 17 and increased to 90% on September 1, with 75.4% of the DUP generated between April 1 and July 31 over the 2-year study period. The results indicated that a different temporal resolution of wind speed affected the calculation of DUP. The DUP was 9.93 × 106 m3/s3 when wind speed was measured at 1 min, 8.96 × 106 m3/s3 at 5 min, 8.51 × 106 m3/s3 at 10 min, and 8.32 × 106 m3/s3 at 15 min. The discrepancies in the DUP when wind speed was measured at different time intervals followed the order of winter > summer > autumn > spring. From an analysis of the diurnal DUP and wind speeds measured at different time intervals, it was found that the main deviation occurred in the early morning and later at night. If the mean wind speed was measured over a time interval of 10 min or longer, there was a certain error in evaluating the damage from eolian activities.