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To investigate the air‐sea gas exchange and its potential influence on the regional fate of polycyclic aromatic hydrocarbons (PAHs) in the East China Marginal Seas (ECMS), which consist of the East China Sea (ECS) and Yellow Sea (YS), we collected air and surface seawater samples of this area in the summer 2018 and winter 2019, respectively. Generally, PAHs underwent a strong volatilization process in the ECMS in both summer and winter. Good correlations between wind speed and the magnitude of air‐sea gas exchange were found for low molecular weight PAHs, suggesting the rate of their air‐sea gas exchange was influenced by the static stability of overlying atmosphere. However, such an influence for high molecular weight PAHs was constrained by their low Henry's law constant. Dissolved concentration of PAHs in surface seawater was another key factor regulating their air‐sea gas exchange, which not only influenced the rate of air‐sea gas exchange but also was involved in the exchange direction. Higher air‐sea gas exchange fluxes of PAHs in winter were attributed to their increasing dissolved concentrations in seawater during this season. A mass conservation analysis revealed a huge volatilization loss of PAHs from seawater to atmosphere, suggesting air‐sea gas exchange might be a key process to modulate the distribution and occurrence of PAHs in the ECS and YS. Such a loss of PAHs in seawater might be compensated by the sediment resuspension, which implied that the sedimentary deposit could serve as a secondary source of PAHs in seawater and overlying atmosphere. Plain Language Summary: Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous semi‐volatile organic compounds that pose a substantial threat to human health and ecological safety due to their carcinogenicity, teratogenicity, and bioaccumulation. Air‐sea gas exchange is a critical mass transfer process influencing the occurrence and distribution of polycyclic aromatic hydrocarbons (PAHs) in marginal seas. We found that the air‐sea gas exchange of PAHs was mainly controlled by their dissolved concentrations in seawater and the wind speed in the East China Marginal Seas (ECMS). Seasonal variation of air‐sea gas exchange of PAHs was observed, especially in the Yellow Sea (YS). Influenced by a greater PAH input from Northern China and the ECMS cross‐shelf circulation system, the volatilization fluxes of PAHs in the YS were higher in winter, despite of lower temperature. Besides, resuspension of PAHs from sediments contributed to the dissolved PAHs in seawater, which compensated the massive loss of PAHs from seawater triggered by air‐sea gas exchange. Our study highlights the significant influence of air‐sea gas exchange and the role of sediment resuspension on the regional fate of PAHs in this area. Key Points: Air‐sea gas exchange of PAHs is mainly controlled by dissolved concentrations in seawater and wind speedAir‐sea gas exchange triggers a massive loss of PAHs from seawater in the East China Marginal SeasDissolved PAHs from sediment resuspension are a potential source of PAH volatilization at air‐sea interface [ABSTRACT FROM AUTHOR]

According to the characteristics of the LEO space particles radiation environment of China's Fengyun No. 3 (FY-3) polar-orbiting meteorological satellites, in order to monitor the characteristics, and space–time distribution of charged particle radiation in the orbit space, it is proposed to install a three-directional high-energy particle detector (HEPD) in the three vertical orthogonal directions of FY-3E, so as to carry out the energy spectrum and flux observation of high-energy protons and electrons in the three directions of the satellite, namely, −X, +Y, and −Z. The on-orbit detection data acquired by these payloads can be used for space environment modeling and solar-terrestrial physics research, and provide data sources for operational space environment weather warning and forecasting. Through the ground accelerator calibration experiment and simulation analysis of the three-directional HEPDs developed in the flight model phase, the experimental results show that all the HEPDs' measured values meet the requirements for technical indexes, such as the detection energy range (high-energy protons: 3–300 MeV; high-energy electrons: 0.15–5.7 MeV), energy span accuracy (<15%), flux accuracy (<15%), and sensitivity (<5% (ΔN/N)). [ABSTRACT FROM AUTHOR]

Rapid urbanization has threatened sustainable urban development in many cities across the globe, causing green space loss and vegetation cover degradation which reduce carbon sequestration. Optimal land management practices (LMPs) in an urban context are known as ways capable of promoting urban vegetation growth and contributing to carbon sequestration. Due to variations of physical, biological, and social structures in urban areas, policymakers often lack relevant information to decide and implement site-specific LMPs. Here we try to extract the areas in need of the optimal LMPs, identify location-dependent optimal LMPs, and assess how much more carbon can be captured by applying a combination of segmenting homogeneous urban environments and neighborhood-based analysis. As one of the most developed cities in China, the greater Guangzhou area (GGA) was selected as a case study. We found that the carbon uptake from the urban vegetation in GGA could be improved on average by 185 gC m−2 yr−1 in flux (or 1.3 TgC yr−1 in total) with optimal LMPs, equivalent to a ~30% increase considering the current level of 662 gC m−2 yr−1 in flux (4.4 TgC yr−1 in total). The carbon uptake potential was found to differ considerably across locations and among different ecosystem types, highlighting spatially varied priorities for implementing optimal LMPs over the space. This study reveals the usefulness of the model in assessing carbon uptake potential from optimal LMPs and emphasizes that future urban planning may consider the importance of optimal LMPs in enhancing vegetation carbon uptake in urban planning. [ABSTRACT FROM AUTHOR]

Anthropogenic activities have had a great impact on the characteristics of watershed pollution. The Pearl River basin is the third largest river in China, but it has been affected by eutrophication impact for a long time. This study comprehensively evaluated the nutrient pollution characteristics of the Pearl River basin from 2016 to 2018. The result shows that the ratio of total nitrogen (TN) and total phosphorus (TP), TN/TP was 24.7 of the Pearl River basin, which indicated that phosphorus was the restrictive factor for eutrophication problems. The limitation of TP maybe caused that TN is difficult to decrease through denitrification and nitrification. The fluxes of TN and TP remained stable in recent 20 years, and the flux of TN and TP transferred from the Pearl River basin to the ocean was 6.86×105 and 2.84×104 t in 2017, respectively. The Pearl River estuary had the largest discharge, accounting for more than 40% of the Pearl River basin. The TN in the West River and North River had a high pollution load, while TP pollution in the East River was very serious. It is necessary to establish an effective mechanism to control nitrogen and phosphorus. A large amount of nitrogen and phosphorus caused the decrease of dissolved oxygen (DO) and the increase of chemical oxygen demand (COD), which aggravated eutrophication. This study of nutrient elements fluxes and distribution in the Pearl River Basin are one of the important prerequisites for clarifying the causes of eutrophication, providing data and theoretical support for further water pollution control and water environmental protection in the future, and also providing a basis for pollution control decisions. [ABSTRACT FROM AUTHOR]

Neonicotinoid insecticides (NNIs) have attracted global concern due to its extensive use in agricultural activities and their potential risks to the animal and human health, however, there is limited knowledge on the regional traits and ecological risks of NNIs in the aquatic environments. We herein investigated the occurrence of NNIs within the midsection of Yangtze River in China, offering the inaugural comprehensive report on NNIs within this region. In this study, eleven NNIs were analyzed in 108 river water and sediment samples from three seasons (normal, dry and wet season). We detected a minimum of seven NNIs in the water and four NNIs in the sediment, with total concentrations ranging from 12.33 to 100.5 ng/L in water and 0.08–5.68 ng/g in sediment. The levels of NNIs in both river water and sediment were primarily influenced by the extent of agricultural activities. The estimated annual load of NNIs within the midsection of Yangtze River totaled 40.27 tons, April was a critical contamination period. Relative potency factor (RPF) analysis of the human exposure risk revealed that infants faced the greatest exposure risk, with an estimated daily intake of 11.27 ng kg−1∙bw∙d−1. We established the acute and chronic thresholds for aquatic organisms by employing the Species Sensitive Distribution (SSD) method (acute: 384.1 ng/L; chronic: 168.9 ng/L). Based on the findings from this study, 33% of the river water samples exceeded the chronic ecological risks thresholds, indicating the urgent need for intervention programs to guarantee the safety of the river for aquatic life in the Yangtze River Basin. [Display omitted] • The annual flux of NNIs was estimated to be 40.27 tons in the studied river. • The concentration of NNIs showed the trend of wet > normal > dry season. • Seasonal agricultural application was important source of NNIs in the area. • NNIs posed chronic risk to the aquatic organisms. [ABSTRACT FROM AUTHOR]

An integrated observation of NO x that included coastal cities and oceanic cruises covering the Qingdao coastal waters sites (QDCW) and the Yellow Sea and East China Sea sites (YECS) was conducted in spring. The average concentrations of the coastal cities, the QDCW, and the YECS were 5.4 ± 4.1, 4.2 ± 3.5, and 2.9 ± 6.8 ppb for NO while 18.5 ± 7.2, 9.4 ± 5.2, and 4.9 ± 6.4 ppb for NO 2 , depicting lowest levels in the open seas. Atmospheric NO and NO 2 showed similar spatial variations over the seas, the stations where the air masses originated from land or nearshore regions showed higher levels, but the decisive influencing factors were not the same in the different study areas. The calculated NO x flux value in the YECS (−8.7 × 10−17 mol N cm−2) indicated that the sea surface was a net sink of atmospheric NO x. The sea was an important sink of the atmospheric NO x. NO x showed a decreasing trend from the coastal cities to the open seas. Light and wind speed were decisive factors influencing atmospheric NO x distributions. [ABSTRACT FROM AUTHOR]

Xu, Y.; Liao, B.; Jiang, Z.; Xin, K.; Xiong, Y., and Guan, W., 2021. Emission of greenhouse gases (CH4 and CO2) into the atmosphere from restored mangrove soil in South China. Journal of Coastal Research, 37(1), 52–58. Coconut Creek (Florida), ISSN 0749-0208. Mangroves are a special ecosystem in tropical and subtropical coastal areas. Currently, it is not adequately understood whether soils in restored mangroves are a substantial source of greenhouse gases. The objectives of this study were to determine whether restored mangrove soils are a substantial source of carbon dioxide (CO2) and methane (CH4) and to identify environmental factors affecting soil CO2 and CH4 fluxes in mangrove sites. From August 2019 to January 2020, CO2 and CH4 flux surveys were conducted in soils at four planted mangrove sites, dominated by Excoecaria agallocha, Kandelia obovata, Bruguiera gymnorrhiza, and Hymenocallis littoralis, respectively, in a mangrove reserve in southern China. The results showed that the CO2 and CH4 flux ranges of the four mangrove sites were 0.9432–1.7892 mmol m–2 h–1 and –0.104 to 0.845 µmol m–2 h–1, respectively. Soil CO2 flux was strongly positively (p < 0.01) correlated with soil organic carbon content and positively correlated (p < 0.05) with soil total N content, temperature, and redox potential. CH4 flux was positively correlated with soil temperature. The results confirm that these restored mangrove soils are only a small greenhouse gases source to the atmosphere. [ABSTRACT FROM AUTHOR]

Antibiotics in aquatic systems of developing countries are a growing concern, particularly with the potential ecological risks and emergence of antimicrobial resistance. In Pakistan, antibiotics are widely consumed and released untreated into rivers, however, there is little information on their occurrence and potential risks. In this study, the concentrations and risk assessment of three commonly consumed antibiotics, ciprofloxacin (CIP), amoxicillin (AMX), and cefixime (CFM) belonging to different classes of fluoroquinolone, penicillin, and cephalosporin respectively were investigated in the Kabul River and its two tributaries, Bara River and Shah Alam River in the northwest region of the country. Composite samples were collected in different sampling campaigns and analyzed using the LC-ESI-MS/MS technique. All three antibiotics were found in higher concentrations ranging from 410 to 1810 ng/L, 180-850 ng/L, and 120-600 ng/L for CIP, AMX, and CFM respectively. The Friedman and Wilcoxon signed-ranked tests revealed insignificant differences in average concentrations of each antibiotic in the three rivers and the Pearson Correlation showed a significant positive correlation of CIP with both AMX and CFM indicating their similar pollution sources. Ecotoxicological risk assessment showed a higher risk to algae and bacteria (P. putida) in the rivers with CIP posing a greater risk. The potential risk of antimicrobial resistance development (ARD) was higher in all the three rivers, particularly in Kabul River where maximum risk quotients (RQ ARD ) of 28.3, 9.4 and 3.4 were noted for CIP, CFM and AMX respectively. The human health (HH) risk was insignificant, though the RQ HH was higher for the lower age groups (0-3 months). In addition, the combined flux of the antibiotics in the Kabul River was estimated as 59 tons/year with CIP having a significant flux relative to the other antibiotics., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

An integrated observation of NO x that included coastal cities and oceanic cruises covering the Qingdao coastal waters sites (QDCW) and the Yellow Sea and East China Sea sites (YECS) was conducted in spring. The average concentrations of the coastal cities, the QDCW, and the YECS were 5.4 ± 4.1, 4.2 ± 3.5, and 2.9 ± 6.8 ppb for NO while 18.5 ± 7.2, 9.4 ± 5.2, and 4.9 ± 6.4 ppb for NO 2 , depicting lowest levels in the open seas. Atmospheric NO and NO 2 showed similar spatial variations over the seas, the stations where the air masses originated from land or nearshore regions showed higher levels, but the decisive influencing factors were not the same in the different study areas. The calculated NO x flux value in the YECS (-8.7 × 10 -17  mol N cm -2 ) indicated that the sea surface was a net sink of atmospheric NO x ., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The 2015/2016 super El Niño event resulted in a positive precipitation anomaly during dry seasons in the Jiulong River watershed, southeast China. Four years (2014–2017) of high frequency, in situ humic‐like fluorescent DOM (FDOMH) data in the Jiulong Estuary were coupled with extrapolation to a freshwater end‐member FDOMH concentration and river discharge data to estimate riverine FDOMH export. The wetter El Niño dry season was followed by lower FDOMH export during the subsequent wet season. Furthermore, in the dry season after El Niño reached its strongest phase, a 90–187% increase in FDOMH export occurred. If widespread, this pattern suggests El Niño events may enhance export of FDOMH from south China rivers in dry seasons resulting in seasonal and annual shunting of the terrestrial DOM export, modulating coastal carbon cycling. This study highlights the need to incorporate climate‐driven regulation patterns on DOM transport across the land‐ocean interface. Key Points: 2015/2016 El Niño event induced a positive precipitation anomaly that increased FDOMH export during dry seasons from a subtropical watershedThe wetter El Niño dry season was followed by lower FDOMH export during the subsequent wet seasonWatershed processes buffered FDOMH export relative to the El Niño‐induced increase of precipitation/discharge [ABSTRACT FROM AUTHOR]

Water samples and sediments from Liangzi Lake were taken and used to study the vertical distribution characteristics of nitrogen (N) and phosphorus (P) in both the overlying and pore water. Fluxes of ammonia (NH4+-N) and phosphate (PO43−-P) were calculated using a one-dimensional transport-reaction model based on Fick's First Law. The results showed that the mean NH4+-N and NO3−-N concentrations in the overlying water of Liangzi Lake were 2.59 and 0.46 mg L−1, respectively. The mean PO43−-P concentrations were lower than the detection limit. Both N and P displayed peaks at the sediment-water interface. For example, the mean concentration of ammonia in pore water in the surficial layer (0–5 cm) was 4.29 ± 2.74 mg·L−1, which was twice than that of the overlying water. Two PO43−-P vertical profile regimes were identified; one had a gradually increasing trend, while the other first increased and then decreased. The mean orthophosphate concentration in the pore water of the surface layer (0–5 cm) was 0.01 ± 0.01 mg·L−1. The spatial distribution of ammonia flux values was highly heterogeneous. Using these data, the annual load contribution of autochthonous ammonia was calculated to be 481 t a−1. Studying N and P pollution and fluxes in the lakes of urban drinking water sources facilitates the provision of protection measures. [ABSTRACT FROM AUTHOR]

Organic ultraviolet filters (OUVFs) are functional ingredients used in cosmetics to protect skin from the harmful effects of ultraviolet (UV) radiation. This study presents recent findings on the distribution of OUVFs in the Pearl River Estuary (PRE), located in southern China. This investigation was conducted during the early stages of the Covid-19 pandemic when the stay-at-home policy was implemented. Analysis revealed the presence of OUVFs in both the surface and bottom water samples collected from eight major outlets of the Pearl River. The OUVFs were detected in both the dissolved phase and suspended particulate matter, with a total concentration ranging from 7.19 ± 6.54 to 20.5 ± 9.62 ng/L. Notably, OUVFs' concentrations in the study period were significantly lower compared to those reported before the pandemic. This implies that effective reduction of OUVF emissions can be achieved through usage reduction combined with the management of direct discharge and appropriate treatment by urban wastewater treatment facilities. During the study period, the annual release of OUVFs was approximately 12.6 kg/1000 people/year, with the greatest contribution from the Hu Men outlet. Consequently, it is imperative to consider the potential ecological risks associated with the release of OUVFs from the PRE into the marine environment, particularly with the potential for an accompanying rebound in risk upon the lifting of restrictions on outdoor activities in the post Covid-19 time., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

The aim of this study was to evaluate the relative contributions of nitrification and denitrification in rice paddy soils under various water events. A laboratory incubation study was conducted in China to quantify N2O production during alternate wetting and drying cycle (AWD) versus permanent flooding (PF). The soils were treated with long-term chemical fertilizer (CF); chemical fertilizer plus pig manure (PMCF); and chemical fertilizer plus rice straw (SRCF) for 5 years. The results showed that N2O flux during AWD was consistently higher than PF. The highest N2O flux during AWD was 1.94 mg m-2 h-1. The PMCF and SRCF soils had higher N2O emissions compared to CF and CK soils. Ammonia oxidizer community peaks were found at 60% field capacity (FC) (p < 0.0001), while, for denitrifier, this increase was maintained for a certain period of time (10d) and then started to decrease. Autotrophic nitrification appeared to be an important and dominant process of N2O emissions during AWD and PF, contributed 79.03% of N2O emissions during AWD, while 36.53% during PF. Thus, the results concluded that under AWD event the addition of pig manure and rice straw plus chemical fertilizer significantly increased the N2O flux, by stimulating the growth of microbial communities. [ABSTRACT FROM AUTHOR]

The Jiapigou gold mine area, located in the upper reaches of the Songhua River, was the first and largest artisanal gold mine once in China, and it used to be prominent in two marking years (1870 and 1974). Jiapigou area had a gold mining history of more than 190 years, which was first opened in 1820. Gold extraction with algamation was applied as the dominant method of excavation from 1940 to 2008, and a total of more than 100 t of gold were extracted from the mine using this method and it was estimated that 100-200 t Hg were released, thus causing severe mercury environmental pollution in the mining area. In the experimental campaigns of this study, in situ air and soil Hg concentrations and air-soil Hg fluxes were measured from April 2009 to December 2011. The results showed that in the study area the total gaseous mercury (TGM) concentration exhibited remarkable spatial and temporal distribution patterns, i.e. the TGM gradually decreased following the increase in distance to gold mining sites in space, and the values in spring, summer and autumn were elevated by 1-2 orders of magnitude in comparison with those in winter. Furthermore, at other sampling sites the total soil mercury (TSM) concentration in spring was higher than that in autumn, except for the contrary laws demonstrated at the Erdaogou mining site. However, in spring and winter the Hg flux between air and soil was under the control of different environmental factors, and the characteristics were clear and distinct. In spring the Hg flux between air and soil was directly under the control of solar irradiation, and the releasing process was predominant with a remarkable positive correlation to solar irradiation. Nevertheless, in winter the Hg fluxes were indirectly under the control of solar irradiation, which caused thermal inversion due to the thick snow cover. The depositing process was predominant and the correlations between Hg flux and air temperature was remarkably negative, and there was a positive correlation between Hg flux and solar irradiation. [ABSTRACT FROM AUTHOR]

Abstract The condition of Baiyangdian Lake (BYDL) will improve as the Xiongan New Area evolves and fulfills its role of easing overcrowding and supporting economic growth. Water and sediment samples from BYDL were analyzed to provide information on nitrogen (N) contamination in BYDL. The mean ammonium N (NH 4 +-N), nitrate N, and total N concentrations in the water samples were 0.36, 0.12, and 2.22 mg/L, respectively, and the ranges were 0.003–8.38, 0.06–0.30, and 1.25–10.34 mg/L, respectively. The N concentrations in water gradually increased from the north to the south of BYDL. Sediment at 90% of the sampling sites was in or above the moderately contaminated class (1000–2000 mg/kg) defined in US Environmental Protection Agency total N pollution standards. Positive NH 4 +-N fluxes were found for 28 of the 34 sediment core samples, so the potential for NH 4 +-N being released from sediment was relatively high. The NH 4 +-N fluxes were 5.35–48.76 mg/m2/day, and the mean and maximum fluxes were 8.71 and 48.76 mg/m2/day, respectively. Benthic organisms will be affected more by NH 4 +-N and NH 3 ·H 2 O in the surface sediment pore water (mean concentrations 4.93 and 0.13 mg/L, respectively) than by the other forms of N. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Dimethylsulfide (DMS) plays an important role in the sulfur biogeochemical cycle and cloud formation on Earth. In the past few decades, coastal shellfish breeding facilities have developed rapidly in shallow coastal regions. However, the effects of coastal shellfish farming on DMS production remain controversial at present. The Yantai offshore is an important shellfish farming region in northern China and the effect of shellfish farming on DMS production was explored combining field investigation and laboratory cultivation in this study. The results showed that coastal shellfish farming can promote the conversion of DMSP to DMS, especially in the shellfish rapid growth period and harvest period. However, different from the zooplankton "sloppy feeding", the shellfish "filter-feeding" first repackages the phytoplanktonic DMSP into fecal DMSP, and then degrades DMSPp into DMS by attracting attached bacteria. Throughout the entire shellfish farming period, average DMS flux in shellfish region was 1.37 μmol m−2 d−1 higher than that in non-shellfish region. Based on the investigation results Yantai coastal shellfish farming region, it can be estimated that the increment of DMS caused by Chinese coastal shellfish farming can reach 2.96 × 106 mol per year. • Coastal shellfish farming can promote the conversion of DMSP to DMS. • DMSPp play a decisive role in determining DMS concentrations in the study region. • The increment of DMS sea-to-air flux caused by Chinese coastal shellfish farming can reach 2.96 × 106 mol per year. [ABSTRACT FROM AUTHOR]

• The physicochemical properties of cinder slag in the birdnest region are characterized. • The modification effects of Ca2+, Mg2+ and Fe2+ on the cinder slag are analyzed. • The interaction modification of Ca2+ and Fe2+ is more strongly. • The injection content of alkaline flux from the tuyere is clarified. An important factor in increasing gas utilization and lowering carbon emissions is the removal of cinder from the tuyere birdnest region of the blast furnace. Based on a 2200 m3 blast furnace in China, the physicochemical characteristics of cinder are investigated in this paper. Alkaline flux's chemical modification and flux injection content are examined to alter the fluidity of cinder slag. Firstly, the basicity and aluminum content of cinder slag are 0.80 and 40.33%, respectively. The melting characteristic of cinder slag is high and the liquid phase fluidity is poor. Secondly, as the content of CaO, MgO, and FeO grow while the viscosity keeps declining, the melting temperature of the cinder first decreases and then rises, rises, and decreases. Compared to Mg2+, Ca2+ and Fe2+ have higher diffusion rates and a stronger interaction modification impact. The potential of flux modification is CaO + FeO > CaO + MgO > CaO > FeO > MgO. Finally, the optimum chemical modification occurs when the basicity of cinder slag is 1.05 and the FeO content is 0.40%. During regular blast furnace operation, 1.62 kg/tHM of limestone and 5.92 kg/tHM of basic oxygen furnace (BOF) slag are injected into the tuyere. [ABSTRACT FROM AUTHOR]

Weekly precipitation samples were collected simultaneously at the urban, suburban, and rural sites in Xiamen, China during 2016–2017 to investigate the characteristics and sources of total mercury (THg) and methyl mercury (MeHg) in precipitation. The annual volume-weight mean (VWM) concentrations of the three areas were in the ranges of 7.9–8.9 ng L −1 for THg and 0.070–0.089 ng L −1 for MeHg, and the wet deposition fluxes were 8.8–11.4 μg m −2 and 0.074–0.12 μg m −2 for the study period of 11 months, respectively. ANONA test revealed that no significant difference of THg concentration among sites, however, the seasonal characteristics of THg strongly depended on the types of locations. THg concentration was the highest in summer at the urban and suburban sites and elevated in winter at the rural site. Urban/suburban THg deposition was closely correlated to both of concentration and precipitation amount, but rural THg deposition was only correlated to precipitation amount. Principal component analysis (PCA) extracted a source factor with high loading for both of THg and MeHg along with secondary inorganic ions. The result suggested that the scavenging of GOM oxidized from GEM in the atmosphere was probably the important source of Hg in precipitation. The oxidation processes also had a positive effect on the formation of MeHg during the study period. [ABSTRACT FROM AUTHOR]

The occurrence, riverine inputs and sources of perfluoroalkyl substances (PFASs) in Taihu Lake, one of the largest lakes in China, were investigated by measuring PFASs including the isomers of perfluorooctanesulfonate (PFOS), perfluorooctanoate (PFOA) and perfluorohexanesulfonate (PFHxS) in the Lake and its main flow-in rivers. It was found that PFHxS, instead of PFOS or PFOA, was predominant both in the Lake and rivers (45.9–351 ng/L), reflecting increasing demand of PFHxS in recent years. The riverine flux of PFASs into the Lake was estimated to be 1255 kg/year. The percentage of linear ( n- ) PFOS and the ratio of 3 + 5 m -/1 m -PFOS were combined to indicate indirect source due to biodegradation of PFOS-precursors. The percentage order of n -PFOS was: the Lake (48.7%) < the flow-in rivers (59.2%) < ECF product (70.3%). While the ratio of 3 + 5 m -/1 m -PFOS was in reverse order: the Lake (11.9) > the rivers (8.99) > ECF (electrochemical fluorination) product (6.76). These suggested that degradation of PFOS-precursors made distinct contribution to PFOS load in the waters, particularly in the Lake. The Lake and river waters had a consistent proportion of n -PFHxS (89.0%), which was slightly lower than the ECF product (96.0%), indicating it was mainly due to the release from production and application of PFHxS as an active ingredient. [ABSTRACT FROM AUTHOR]

Degassing of carbon monoxide (CO), which plays a significant role in the contribution of deep carbon to the atmosphere, commonly occurs within active fault zones. CO degassing from soil to the atmosphere in the Basin and Range province, west of Beijing (BRPB), China, was investigated by in-situ field measurements in the active fault zones. The measured concentrations of CO in soil gas in the BRPB ranged from 0.29 × 10 −6 to 1.1 × 10 −6 with a mean value of 0.6 × 10 −6 , which is approximately twice as large as that in the atmosphere. Net fluxes of CO degassing ranged from −48.6 mg m −2 d −1 to 12.03 mg m −2 d −1 . The diffusion of CO from soil to the atmosphere in the BRPB was estimated to be at least 7.6 × 10 3 ton/a, which is comparable to the corresponding result of about 1.2 × 10 4 ton/a for CO 2 . CO concentrations were spatially heterogeneous with clearly higher concentrations along the NE-SW trending in the BRPB. These elevated values of CO concentrations were also coincident with the region with low-velocity and high conductivity in deep mantle, and high Poisson’s ratio in the crust, thereby suggesting that CO degassing from the soil might be linked to upwelling of the asthenospheric mantle. Other sources of CO in the soil gas are suggested to be dominated by chemical reactions between deep fluids and carbonate minerals (e.g., dolomite, limestone, and siderite) in country rocks. Biogenic processes may also contribute to the CO in soil gas. The spatial distribution patterns of CO concentrations are coincident with the stress field, suggesting that the concentrations of CO could be a potential indicator for crustal stress field and, hence is potential useful for earthquake monitoring in the BRPB. [ABSTRACT FROM AUTHOR]

Fine particle with diameter <2.5 μm (PM 2.5 ) have important direct and indirect effects on human life and activities. However, the studies of fine particle were limited by the lack of monitoring data obtained with multiple fixed site sampling strategies. Mobile monitoring has provided a means for broad measurement of fine particles. In this research, the potential use of mobile lidar to map the distribution and transport of fine particles was discussed. The spatial and temporal distributions of particle extinction, PM 2.5 mass concentration and regional transport flux of fine particle in the planetary boundary layer were investigated with the use of vehicle-based mobile lidar and wind field data from north China. Case studies under different pollution levels in Beijing were presented to evaluate the contribution of regional transport. A vehicle-based mobile lidar system was used to obtain the spatial and temporal distributions of particle extinction in the measurement route. Fixed point lidar and a particulate matter sampler were operated next to each other at the University of Chinese Academy of Science (UCAS) in Beijing to determine the relationship between the particle extinction coefficient and PM 2.5 mass concentration. The correlation coefficient (R 2 ) between the particle extinction coefficient and PM 2.5 mass concentration was found to be over 0.8 when relative humidity (RH) was less than 90%. A mesoscale meteorological model, the Weather Research and Forecasting (WRF) model, was used to obtain profiles of the horizontal wind speed, wind direction and relative humidity. A vehicle-based mobile lidar technique was applied to estimate transport flux based on the PM 2.5 profile and vertical profile of wind data. This method was applicable when hygroscopic growth can be neglected (relatively humidity<90%). Southwest was found to be the main pathway of Beijing during the experiments. [ABSTRACT FROM AUTHOR]

Rivers are recognized as an important pathway for transport of microplastics (MPs) from land to sea, but limited information is available on the spatial distribution and seasonal variation of riverine MPs from upper reaches to estuaries. Such information is critical for source apportionment and development of effective management measures for riverine MPs. To fill the knowledge gap, we investigated the occurrence of MPs in surface water along an urban river in Guangzhou, southern China in wet and dry seasons. The abundances of MPs from 16 sampling sites in the wet and dry seasons varied from 0.123 to 1.84 particles m−3 and from 0.046 to 4.21 particles m−3, respectively. The spatial distribution of MP abundances showed an increasing trend from upstream to midstream and a decreasing trend from midstream to downstream and estuaries. The abundances of MPs peaked at the midstream, which is surrounded by a highly urbanized region with high population density (∼2530 persons per km2). The large surface water runoff during the wet season elevated the MP abundance in riverine water, except for that flowing through the central urban area where the abundance of MPs collected in the dry season was higher than that in the wet season. This was mainly ascribed to the large input from extensive anthropogenic activities and slow water flow rate in urban areas. The estimated monthly riverine MP fluxes from Humen, Hongqili, and Jiaomen were 7.42, 2.38, and 2.3 billion particles, respectively, in the wet season, and 0.86, 0.71, and 0.19 billion particles, respectively, in the dry season. An increase of riverine MP fluxes from Humen, Hongqili, and Jiaomen in the past three years was evident. The results from the present study provide valuable information for source apportionment of riverine MPs and support the initialization of possible MPs controlling measures. [Display omitted] • The main polymer types of microplastics (MPs) were polypropylene and polyethylene. • The MP abundances ranged in 0.123–1.84 and 0.046–4.21 particles m−3 in wet and dry season, respectively. • The maximum abundance of MPs in the Pearl River appeared in the urban area. • The spatial variation of MPs is more obvious in dry season than that in wet season. [ABSTRACT FROM AUTHOR]

Over the past decades, rivers have delivered imbalanced nutrient loads to coastal marine ecosystems due to human activities, which leads to serious regional or global eutrophication problems. The Minjiang River is heavily influenced by human activities. To understand the changing characteristics of nutrient transport ratios in the Minjiang River waters, we measured the seasonal variations of carbon, nitrogen, phosphorus and silicon nutrients in the lower surface waters of the Minjiang River between July 2019 and July 2020. The results showed that the annual average contents of dissolved silicon (DSi), lithogenic silicon (LSi) and biogenic silicon (BSi) in the surface waters of the lower Minjiang River were 5.30, 4.58 and 2.37 mg·L -1 , respectively. There were large seasonal differences among these parameters, with higher content of DSi than LSi and BSi in summer, higher content of DSi than BSi and LSi in autumn and higher content of LSi than DSi and BSi in winter. The proportions of DSi in total silicon tended to decrease gradually from land to sea, while the proportion of BSi was on the contrary. In term of stoichiometric ratios, the Minjiang River mostly presented carbon or phosphorus limitation and was unlimited by silicon or nitrogen. About 1.03×10 10 mol DSi and 0.46 ×10 10 mol BSi were delivered via the Minjiang River to the ocean yearly, showing a decreasing trend year by year. Based on the data in recent years, the nutrient loads of carbon, nitrogen, and phosphorus transported by Minjiang River showed an increasing trend. The imbalanced nutrient loads may lead to changes in the structure and function of the river, estuary, and offshore ecosystems. The study of nutrient stoichiometric ratios can provide a theoretical basis for solving the problems in structural balance of nutrients and eutrophication in Minjiang River estuary and adjacent marine waters.

Estuaries are unique transition zones connecting terrestrial and coastal environments and are recognized as primary conveyors for land-derived plastics to open oceans. Riverine microplastics (MPs) have been commonly investigated using sequential sampling which might not effectively reflect the actual load. In this study, sampling at eight outlets was performed during a complete tidal cycle to estimate the MP flux to the Pearl River Estuarine (PRE) using a concurrent sampling strategy. The MP abundances ranged from 2.90 ± 0.57-5.9 ± 2.27 particles/L. A remarkable difference between tides in MP abundances suggests tidal effect should not be overlooked in assessment. The MP load through the eight outlets was estimated at 304 trillion particles or 1102 tons into the PRE annually. Additionally, similar potential ecological risk assessment among eight rivers implied that environmental threats posed by less urbanized and populated rural areas on the western side have been under-evaluating for decades., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

The concentrations and flux of CO, Radon (Rn), and gaseous elemental mercury (Hg) in soil gas were investigated based on the field measurements in June 2010 at ten sites along the seismic rupture zones produced by the May 12, 2008, Wenchuan M 8.0 earthquake in order to assess the environmental impact of degassing of CO, Rn and Hg. Soil gas concentrations of 344 sampling points were obtained. Seventy measurements of CO, Rn and Hg flux by the static accumulation chamber method were performed. The results of risk assessment of CO, Rn and Hg concentration in soil gas showed that (1) the concentration of CO in the epicenter of Wenchuan M 8.0 earthquake and north end of seismic ruptures had low risk of asphyxia; (2) the concentrations of Rn in the north segment of seismic ruptures had high levels of radon, Maximum was up to level 4, according to Chinese code (GB 50325-2001); (3) the average geoaccumulation index I of soil Hg denoted the lack of soil contamination, and maximum values classified the soil gas as moderately to strongly polluted in the epicenter. The investigation of soil gas CO, Rn and Hg degassing rate indicated that (1) the CO in soil gas was characterized by a mean $$\updelta^{13}C_{CO2}$$ of −20.4 ‰ and by a mean CO flux of 88.1 g m day, which were in the range of the typical values for biologic CO degassing. The maximum of soil CO flux reached values of 399 g m day in the epicenter; (2) the soil Rn had higher exhalation in the north segment of seismic ruptures, the maximum reached value of 1976 m Bq m s; (3) the soil Hg flux was lower, ranging from −2.5 to 18.7 n g m h and increased from south to north. The mean flux over the all profiles was 4.2 n g m h. The total output of CO and Hg degassing estimated along seismic ruptures for a survey area of 18.17 km were approximately 0.57 Mt year and 688.19 g year. It is recommended that land-use planners should incorporate soil gas and/or gas flux measurements in the environmental assessment of areas of possible risk. A survey of all houses along seismic ruptures is advised as structural measures to prevent the ingress of soil gases, including CO and Rn, were needed in some houses. [ABSTRACT FROM AUTHOR]

Riverine samples were collected at various locations in the Pearl River Delta (PRD) to determine the concentrations of heavy metals (Cr, Ni, Cu, Mn, Zn, Cd, and Pb) in time and space and to estimate the fluxes of heavy metals to the coastal waters off South China. Most of the elements exhibit clear temporal and spatial trends. Principal component analysis shows that surface erosion is the major factor affecting metal concentrations in particulates in the PRD. Natural geology is an important source of these heavy metals. The annual fluxes of Cr, Ni, Cu, Mn, Zn, Cd, and Pb in upstream and downstream were 445, 256, 241, 3293, 1279, 12, and 317 t/year and 1823, 1144, 1786, 15,634, 6183, 74, and 2017 t/year, respectively. A comparison indicated that the annual fluxes of Mn accounted for 1.3% of the global river fluxes, whereas other elements contribute < 1%. [ABSTRACT FROM AUTHOR]

This papers deals with direct measurements of dry deposition flux of total acidifying N species (gaseous HNO and particulate NO) and theoretically by parameterization method to vegetation (leaf surfaces) over a semiarid region in India. Annual average experimental dry deposition of NO to leaf of Cassia is 0.65 ± 0.61 mg m day. Ambient concentrations of HNO vapor and particulate NO are 1.53 and 1.24 μg m, respectively. Theoretically obtained dry deposition velocity of HNO and NO are 0.74 cm s for both while calculated dry deposition flux of total NO is found to be 1.3 ± 0.33 mg m day. The measured dry deposition flux of NO to Cassia leaf is in the range of theoretically obtained flux. The annual input of N as nitrate is 3.8 mmol m year which is lower than the other forest site in China which is probably because of low pollution than China. [ABSTRACT FROM AUTHOR]

Land transportation in the Yangtze River basin is an important source of microplastics in the East China Sea, so it is significant to clarify the source, fate and river-sea transition of microplastics. Taking the Yangtze River as the study area, the interpolation method was used to analyze the monthly changes of the microplastic load in the estuary, the input-output model was used to estimate the flux of microplastics into the sea, and the inflow process of microplastics was studied through correlation analysis. The results showed that: (1) The load of microplastics in the Yangtze River estuary varied with season, reaching the maximum in October, with a monthly load of 3.91 Gg; (2) The total amount of microplastics entering the sea in the Yangtze River basin was higher than the medium level, which was 7.02 Gg. Among them, tributary input was the most important source, accounting for 62.9%. Non-point and point sources were further subdivided into 11 categories, with the largest proportion of microplastics generated during vehicle trip. Spatially speaking, the microplastics transported in the midstream accounted for the largest proportion, accounting for 55.56%; (3) microplastics had a strong correlation with COD and TP, indicating that the inflow process of microplastics was similar to that of traditional pollutants, which were river retention, wastewater treatment plant removal, water consumption removal and inflow to the East China Sea. Although the proportion of the last one was only 8.05%, the ecological risk was still not negligible due to the huge amount. [Display omitted] • Microplastic flux from the Yangtze River basin to the East China Sea is 7.02 Gg. • The contributions from point sources and non-point sources are 2.9% and 34.2%. • Microplastic is strongly correlated with COD and TP in the Yangtze River basin. • Yangtze River estuary has the largest Microplastic load in October. [ABSTRACT FROM AUTHOR]

Heavy metal pollution of agricultural soil, especially Cd, has become a global threat to food safety and human health. Analysis of Cd fluxes through different input/output pathways is widely used to predict the change of Cd content in agricultural soil, identify the critical pathways, and assist in developing effective management strategies to protect the environmental quality of agricultural soils. In the present study, literature recording input/output fluxes of Cd through different pathways in agricultural soils were investigated, with study areas primarily located in China, Japan, and Europe. Fluxes of Cd at the study sites were calculated, and comparative analyses were carried out. Results indicated that the dominant input pathway of Cd was strongly associated with the intensity of local industrial activities. Atmospheric deposition was the predominant input pathway of Cd for 75% of the study cases. Irrigation and livestock manure were also major pathways of Cd input in China. The main output pathways were influenced by the planting structure, precipitation, topography, etc. Crop harvesting and leaching to groundwater played important roles among all Cd output pathways in China, and crop harvesting alone could remove a significant amount of Cd from the soil, with an estimated average flux of 6.27 g/ha/yr. Leaching was the dominant Cd output pathway in Europe, accounting for 77%–93% of total outflux. To mitigate the accumulation of Cd in agricultural soil, standards to regulate Cd in the atmospheric environment, irrigation water, and agricultural additives should be tightened, and regulated removal and disposal of crops harvested from the heavily contaminated field should be promoted. [Display omitted] • The dominant input pathway of Cd in agricultural soils was atmospheric deposition. • Crop harvesting is the dominant output pathway in China. • Leaching and runoff were also significant output fluxes of Cd. • Uncertainty is associated with different monitoring methods and prediction models. [ABSTRACT FROM AUTHOR]

This study investigated environmental influences on inorganic nitrogen exchange at the sediment-water interface and quantified the function of sediment as inorganic nitrogen sink/source in the eastern Chongming tidal flat of the Yangtze Estuary. Intact sediment cores (20-25 cm deep) were collected from the high, middle and low tidal flats of the study area every 2 months from July 2012 to May 2013, and incubated to measure the fluxes of ammonium and nitrate (plus nitrite) across the sediment-water interface via continuous-flow experiments. The incubation experimental results showed that ammonium was mainly released from the sediment into the overlying water, with a flux of −5.91 to 14.44 mmol m day. In contrast, nitrate was primarily influxed from the overlying water into the sediment, with a flux of −20.09 to 8.72 mmol m day. In this work, temperature, salinity, sedimentary ammonium and nitrate, and total organic carbon were observed to significantly affect the dynamic exchange of inorganic nitrogen across the sediment-water interface of the study area, via controlling nitrogen transformation processes in sediments. It was also estimated that ca. 2101 t N year for ammonium was totally released from the sediment to overlying water while ca. 1577 t N year for nitrate was removed from the water to sediment. The dynamic exchanges of inorganic nitrogen at the sediment-water interface implied that the sediment has important influence on adjusting the levels of ammonium and nitrate in tidal water of the study area. [ABSTRACT FROM AUTHOR]

The occurrence of extreme rainfall events and associated flooding has been enhanced due to climate changes, and is thought to influence the flux of total dissolved iron (TDI) in rivers considerably. Since TDI is a controlling factor in primary productivity in marine ecosystems, alteration of riverine TDI input to the ocean may lead to climate change via its effect on biological productivity. During an extreme rainfall event that arose in northeastern China in 2013, water samples were collected in the midstream of the Heilongjiang River to analyze the concentration and species of TDI as well as other basic parameters. The speciation of TDI was surveyed by filtration and ultrafiltration methods. Compared with data monitored from 2007 to 2012, the concentration of TDI increased significantly during this event, with an average concentration of 1.11 mg/L, and the estimated TDI flux reached 1.2 × 105 tons, equaling the average annual TDI flux level. Species analysis revealed that low-molecular-weight complexed iron was the dominant species, and the impulse of TDI flux could probably be attributed to the hydrological connection to riparian wetlands and iron-rich terrestrial runoff. Moreover, dissolved organic matter played a key role in the flux, species and bioavailability of TDI. In addition, there is a possibility that the rising TDI flux could further influence the transport and cycling of nutrients and related ecological processes in the river, estuary coupled with the coastal ecosystems, which merits closer attention in the future. [ABSTRACT FROM AUTHOR]

The Wujiang River is an important tributary to the Changjiang River that has been intensively impounded for hydropower exploitation. To understand the potential impact of reservoir construction on the riverine inorganic carbon transport, seasonal longitudinal sampling was conducted in four reservoirs Hongjiadu (HJD), Dongfeng (DF), Suofengying (SFY) and Wujiangdu (WJD) along the Wujiang River from April 2006 to January 2007. Results indicated that damming the river induced an obvious discontinuity of water chemistry in the warmer seasons. δC of dissolved inorganic carbon (DIC) ranged from −3 to −11.4 ‰, likely as the results of photosynthesis, respiration and carbonate weathering. During periods of thermal stratification, the addition of CO from respiration to hypolimnion and the deep water release for hydropower generation led to higher pCO downstream, as well as C depletion in DIC and undersaturated to calcite. An estimate of DIC budget indicated that only DF reservoir was the sink for DIC while reservoirs HJD, SFY and WJD were the sources for DIC. However, when the retained water was taken into account, for the reason of water storage occurring mainly in HJD and DF, all reservoirs became the sources for DIC with exporting rates of 26.68, 7.97, 6.22 and 11.80 % for HJD, DF, SFY and WJD, respectively. [ABSTRACT FROM AUTHOR]

The residual levels of organochlorine pesticides (OCPs) in the dust fall around Lake Chaohu were measured using gas chromatography mass spectrometry from April 2010 to March 2011. The fluxes, components, temporal–spatial variations, and sources of OCPs were also analyzed. Twenty-one types of OCPs were detected in the dust fall samples around Lake Chaohu, with a total concentration of 51.54 ± 36.31 ng/g and a total flux of 10.01 ± 13.69 ng/(m 2 day). Aldrin (35.3 %), endosulfan (39.1 %), dichlorodiphenyltrichloroethanes (DDTs) (49.8 %), and isodrin (37.1 %) were the major OCPs in the spring, summer, autumn, and winter, respectively. Both the residual level and the flux were higher in the spring than in other seasons and higher at the outer lake sampling sites than inner lake sampling site. The potential source of the hexachlorcyclohexanes in the dust fall may be recent lindane usage. The DDTs mainly came from historical dicofol usage, and a significant input of DDT was found during April and June. The presence of endosulfan may be due to the present use of technical endosulfan. The aldrin in the dust might be due to its occasional usage, and isodrin may be a result of long-distance transport from other countries. [ABSTRACT FROM AUTHOR]

The influence of regional transport on aerosol pollution has been explored in previous studies based on numerical simulation or surface observation. Nevertheless, owing to inhomogeneous vertical distribution of air pollutants, vertical observations should be conducted for a comprehensive understanding of regional transport. Here we obtained the vertical profiles of aerosol and its precursors using ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) at the Nancheng site in suburban Beijing on the southwest transport pathway of the Beijing-Tianjin-Hebei (BTH) region, China, and then estimated the vertical profiles of transport fluxes in the southwest-northeast direction. The maximum net transport fluxes per unit cross-sectional area, calculated as pollutant concentration multiply by wind speed, of aerosol extinction coefficient (AEC), NO 2 , SO 2 and HCHO were 0.98 km -1  m s -1 , 24, 14 and 8.0 μg m -2 s -1 from southwest to northeast, which occurred in the 200-300 m, 100-200 m, 500-600 m and 500-600 m layers, respectively, due to much higher pollutant concentrations during southwest transport than during northeast transport in these layers. The average net column transport fluxes were 1200 km -1  m 2 s -1 , 38, 26 and 15 mg m -1 s -1 from southwest to northeast for AEC, NO 2 , SO 2 and HCHO, respectively, in which the fluxes in the surface layer (0-100 m) accounted for only 2.3%-4.2%. Evaluation only based on surface observation would underestimate the influence of the transport from southwest cities to Beijing. Northeast or weak southwest transports dominated in clean conditions with PM 2.5 <75 μg m -3 and intense southwest transport dominated in polluted conditions with PM 2.5 >75 μg m -3 . Southwest transport through the middle boundary layer was a trigger factor for aerosol pollution events in urban Beijing, because it not only directly bringing air pollutants, but also induced an inverse structure of aerosols, which resulted in stronger atmospheric stability and aggravated air pollution in urban Beijing., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Although pharmaceuticals and personal care products (PPCPs) have attracted great attentions, their occurrence characteristics across different water bodies at a basin scale remain poorly understood. To grasp a more comprehensive understanding of PPCP pollution from the perspective of the whole basin, the occurrence, spatial and seasonal variation, source, and flux of thirteen PPCPs across the different environmental compartments of the northern Taihu Lake Basin (TLB) were studied. The results showed that the non-therapeutic pharmaceuticals caffeine (CFI) and n, n-diethyl-m-toluamide (DEET) were the main components across the different environmental compartments. The total concentrations of detected PPCPs ranged from 0.2 to 2437.9 ng/L. Higher concentrations of PPCPs were observed in spring and autumn, which were mainly attributed to seasonal differences in PPCP consumption. Generally, pollution level was higher in industry and agriculture area and in the inner bay and southwest of Taihu Lake. Source apportionment indicated that untreated water was the main source of PPCPs in river waters of the northern TLB. Flux estimation showed that the mean annual flux of PPCPs from northern TLB to Taihu Lake in 2021 was 1.6 t/a, which was higher in comparison with other areas. Overall, the resulting data will be useful to enrich the research of PPCPs in freshwater for environmental investigations.

We carried out a downscaling treatment over China using the CarbonTracker numerical model, which was applied using double grid nesting technology (3° × 2° over the whole globe, 1° × 1° over China), simulating and analyzing atmospheric CO 2 concentrations over 10 recent years (2000–2009). The simulation results agreed very well with observed data from four background atmospheric monitoring stations in China (The periods for which the simulation results and observed values be compared were January 2000 to December 2009 for the WLG station and June 2006 to December 2009 for the SDZ, LFS, and LAN stations), giving correlation coefficients of >0.7. The high-resolution simulation data correlated slightly better than the low resolution simulation data with the observed data for three of the regions’ atmospheric background stations. Further analysis of the annual, seasonal CO 2 concentration variations at the background stations showed that the CO 2 concentration increased each year over the study period, with an average annual increase of more than 5%, and annual increases of more than 7% at the Shangdianzi and Lin’an stations. Seasonal CO 2 variations were greater at the Longfengshan station than at the Shangdianzi or Lin’an stations. However, the CO 2 concentrations were higher at the Shangdianzi and Lin’an stations because they are greatly affected by human activities in the Jingjinji and Changjiang Delta economic zones. Spatial distribution in CO 2 concentrations and fluxes were higher in eastern than in western China. [ABSTRACT FROM AUTHOR]

In this study, surface water samples from the Wenyu River and the North Canal, effluent from major wastewater treatment plants (WWTPs) in Beijing, and wastewater from open sewers that discharge directly into the river system were collected and analyzed for 16 priority USEPA polycyclic aromatic hydrocarbons (PAHs). Concentrations of these 16 PAHs ranged from 193 to 1790 ng/L in river surface waters, 245 to 404 ng/L in WWTP effluents, and 431 to 2860 ng/L in the wastewater from the small sewers. The WWTP effluent was the main contributor of dissolved PAHs to the river, while wastewater from the small sewers contributed both dissolved and suspended particulate matter-associated PAH to the river as indicated by the high dissolved organic carbon and suspended particulate matter contents in the wastewater. Although the flow from each open sewer was small, a PAH discharge as high as 44 kg/year could occur into the river from these types of sewers. This amount was equivalent to about 22 % of the PAH loads discharged into the North Canal downstream from Beijing, whereas the remainder was mainly released by the major WWTPs in Beijing. [ABSTRACT FROM AUTHOR]

We presented measurements of wet deposition of NH-N and NO-N from 1986 to 2006 in Shenzhen City, China. Over the past 20 years, NO-N concentration had significantly increased, but a reverse trend was found for NH-N. The main form of total inorganic nitrogen (TIN) was NH-N and the average NH-N/NO-N ratio was 1.57 in this area. The contribution of NO-N to TIN increased from 28-42% in the period of 1986-2000 to 50-63% during 2001-2006. The increased deposition flux of NO-N resulted in the increasing trend of TIN, although NH-N showed a decreasing trend over time. Average deposition flux of TIN during 1986-2006 was 13.24 kg/ha/year, with a minimum value of 6.03kg/ha/year in 1988 and a maximum value of 20.52 kg/ha/year in 1997. Wet deposition fluxes of N appeared to vary with season, 81% occurred in the warm season (from April to September). The wet deposition of TIN to the Shenzhen Reservoir reached 8,902 kg in 2006, which contributed 9.95% of the total nonpoint pollution to the reservoir and will be increased in the future. [ABSTRACT FROM AUTHOR]

Nitrous oxide (N 2 O) is one of the six greenhouse gases stipulated in the Kyoto Protocol. Its greenhouse potential over the past century was 298 times that of CO 2 , and the concentration of atmospheric N 2 O has been continuously and rapidly increasing during the past hundred years. Shallow lakes are an important source of atmospheric N 2 O. In order to explore the temporal and spatial changes and potential driving factors of N 2 O emissions from eutrophic water, we conducted field observations in February (winter) and August (summer) in Lake Taihu. We used the coefficient of diffusion-headspace bottle method to trace the variability in the N 2 O concentration[ c (N 2 O)] and efflux[ F (N 2 O)] from surface water bodies and explored the potential driving factors of N 2 O emissions. The optical measurements of dissolved organic matter (DOM) are an effective approach for tracing the source and composition of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON). The migration and transformation processes of DOM also release a large amount of inorganic nitrogen, which changes the redox potential of the water column and thereby affects N 2 O emissions. Our results showed that the variability in c (N 2 O) and F (N 2 O) in the surface waters of Lake Taihu were strongly affected by water temperature and nutrient levels. The average c (N 2 O) of the surface waters was (19.7±2.7) nmol·L -1 , corresponding to a mean F (N 2 O) of (41.1±1.8) μmol·(m 2 ·d) -1 , and the means of both c (N 2 O) and F (N 2 O) were higher in summer than those in winter ( t -test, P <0.01). The input and accumulation of DOM could increase the production and emission potential of N 2 O in water bodies, as supported by both c (N 2 O) and F (N 2 O) significantly increasing with increasing level of terrestrial humic-like C1. The integration ratio of peak C to peak T I C : I T of DOM and the spectral slope S 275-295 results indicated that there were high inputs of terrestrial DOM in the northwestern inflowing river mouths, concurring with the high production and emission of N 2 O found there. This suggested that the accumulation and degradation of terrestrial DOM potentially fueled the emission of N 2 O. Our results showed that water temperature, DOM composition, and nutrient level were all important factors affecting N 2 O emission from Lake Taihu. Long-term continuous observation can be applied to better evaluate the impact of various environmental factors on the production and emission of N 2 O in water bodies and to help with providing scientific emission reduction plans.

A drastic decrease in the suspended sediment of Dongting Lake (DTL) has been observed due to Three Gorges Dam (TGD) impoundment operation since 2003. However, the relationship between sediment loads and metal fluxes has not been studied. This study comprehensively analyzed the content characteristics of seven metal(loid)s (As, Cd, Cr, Cu, Hg, Pb, and Zn) in the surface sediment of DTL from 2000 to 2019. The period of 2005-2009 corresponded to a metal(loid) enrichment stage in the sediment of DTL. The metal(loid) cumulative input of DTL from 2000 to 2019 reached 153 × 10 3  t, and the increasing rate was gradually diminished because of TGD operation, while the metal(loid) cumulative output reached 132 × 10 3  t. Undergoing an input-output state transition, the metal(loid) cumulative deposition of DTL in 2019 was only 42% of its peak in 2007. Especially, the metal(loid) fluxes of DTL all became negative for the first time in 2006. It is worth noting that Cd in DTL has shifted to a net export during the study period. Finally, the assessment results of pollution, risk, and toxicity indicated that metal(loid) effects on sediment quality were weakening in recent years. This study confirmed that DTL has shifted from metal(loid) deposition to export, providing new information for future DTL management options., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Abstract: Temporal trend of polychlorinated biphenyls (PCBs) was determined in precipitation and monthly depositional fluxes were calculated in Beijing for the first time from February 2009 to March 2011. Total PCBs concentrations ranged from 7.00 to 993 ng L−1 in dissolved phase and from 1.00 to 133 ng L−1 in particulate phase, with a two orders of magnitude variation. Concentrations of PCBs were dominated by dissolved phase, which accounted for 82.5% of the total PCBs in precipitation, implying PCBs enrichment in rainwater due to efficient scavenging of highly contaminated gas phase and nonfilterable submicron particles which easily adsorbed organic contaminants in urban atmosphere. Highest concentrations of PCBs were measured in snow, which were about two times higher than those in rainwater, demonstrating more efficient scavenging of PCBs by snow. The sum of bi-, tri- and tetrachlorinated congeners accounted for 70.5% of total PCBs in precipitation, suggesting that PCBs mainly come from the historical usage of domestic PCB product, e.g., trichlorobiphenyl. PCBs concentrations in both dissolved and particulate phases showed slow rate of decline, with a half-life of 16.9 years in precipitation, suggesting that the atmospheric concentrations of PCBs were decreasing slowly in Beijing. The wet deposition flux of ∑PCBs ranged from 0.240 to 6.55 μg m−2 month−1 (mean: 1.41 μg m−2 month−1), indicating a relatively high level of PCBs contamination in Beijing atmosphere. [Copyright &y& Elsevier]

The rivers across Sanjiang Plain are an important path in transferring total dissolved iron (TDFe) into Okhotsk Sea. Distribution of TDFe in main rivers (Amur River, Ussuri River, and Songhua River) and marshy rivers (Yalv River, Bielahong River, and Naoli River) of Sanjiang Plain from 2005 to 2008 was investigated. TDFe concentrations ranged from 0.05 to 6.40 mg L−1 (mean 0.76 mg L−1) and the TDFe species are in the following order: Colloidal iron > ionic iron > complexed iron. Compared with the main rivers, the marshy rivers showed higher TDFe concentration and dissolved organic carbon concentration (DOC), and lower pH value. TDFe concentrations were influenced by several factors, whereas, the concentration of DOC, ${\rm HCO}_{3}^{- } $, and ${\rm NO}_{{\rm 3}}^{- } $ showed remarkable correlation through Spearman correlation coefficient analysis. The rivers mostly showed high TDFe concentration on May and October when the farm activities frequently occur. After 50 years' cultivation of wetlands, the free iron (Fe2+ and Fe3+) showed distinct decrease from 195 to 88.2t in Naoli River. Land use change had decreased TDFe output in rivers of Sanjiang Plain because of the changed concentration and component of DOC, which had higher affinity and selectivity with iron. [ABSTRACT FROM AUTHOR]

Abstract: A coupled physical and sediment transport model was used to study the mass flux budgets of water and suspended sediments in the Pearl River Delta (PRD). The coupled model incorporates the Pearl River network, the Pearl River Estuary (PRE) and adjacent coastal waters in one overall modeling system. The results indicate that the river network and the PRE both have pronounced temporal and spatial variability in water and sediment fluxes, in hydrodynamic features and in sediment depositional patterns. In the river network, the riverine fluxes of water and suspended sediments are dominated by the West River, and those that are exported to the PRE (defined as the estuarine fluxes) are primarily contributed by Modaomen. The river outlets are highly responsive to the main tributaries in terms of water and sediment fluxes, revealing a close coupling between the upstream and the downstream boundaries. Most of the annual riverine and estuarine fluxes occur in the wet season, approximately 74% of the water flux and riverine and estuarine fluxes of suspended sediments of 94% and 87%, respectively. Although the water and sediment transport is dominated by river discharge, the tides are also an important factor, especially in regulating the structures of seasonal deposits in the river network (deposition in the wet season and erosion in the dry season). In the PRE, various types of physical forcing, including river discharge, monsoon winds, tides, coastal currents and the gravitational circulation associated with a density gradient, operate in concert to control the water and sediment transport in the estuary. Most of the oceanic fluxes of water and suspended sediments entering the South China Sea take place in the dry season and are primarily conveyed by strong western coastal currents. The PRE is a sedimentary system characterized by intricate depositional structures in space and time. Several depositional patterns and the associated driving mechanisms were identified. A fan-shaped deposition zone, the most intense deposition belt in the PRE, was found in the outer Modaomen Bay, where hypoxia has been reported. This work provides a basis for subsequent water quality applications in the PRD, including studies of hypoxia, eutrophication and maximum turbidity. [Copyright &y& Elsevier]

Abstract: Greenhouse gas emissions from hydroelectric dams have recently given rise to controversies about whether hydropower still provides clean energy. China has a large number of dams used for energy supply and irrigation, but few studies have been carried out on aquatic nitrous oxide (N2O) variation and its emissions in Chinese river-reservoir systems. In this study, N2O spatiotemporal variations were investigated monthly in two reservoirs along the Wujiang River, Southwest China, and the emission fluxes of N2O were estimated. N2O production in the reservoirs tended to be dominated by nitrification, according to the correlation between N2O and other parameters. N2O saturation in the surface water of the Wujiangdu reservoir ranged from 214% to 662%, with an average fluctuation of 388%, while in the Hongjiadu reservoir, it ranged from 201% to 484%, with an average fluctuation of 312%. The dissolved N2O in both reservoirs was over-saturated with respect to atmospheric equilibrium levels, suggesting that the reservoirs were net sources of N2O emissions to the atmosphere. The averaged N2O emission flux in the Wujiangdu reservoir was 0.64 μmol m−2 h−1, while it was 0.45 μmol m−2 h−1 in the Hongjiadu reservoir, indicating that these two reservoirs had moderate N2O emission fluxes as compared to other lakes in the world. Downstream water of the dams had quite high levels of N2O saturation, and the estimated annual N2O emissions from hydropower generation were 3.60 × 105 and 2.15 × 105 mol N2O for the Wujiangdu and the Hongjiadu reservoir, respectively. These fluxes were similar to the total N2O emissions from the reservoir surfaces, suggesting that water released from reservoirs would be another important way for N2O to diffuse into the atmosphere. It can be concluded that dam construction significantly changes the water environment, especially in terms of nutrient status and physicochemical conditions, which have obvious influences on the N2O spatiotemporal variations and emissions. [Copyright &y& Elsevier]

Abstract: The concentrations, spatial distribution and compositional patterns of extensively used hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) in urban dustfall in a metropolis-Beijing are presented in this paper. The potential sources are discussed and soil burdens are predicted based on the fluxes. The hotspots in commercial areas are identified by spatial distribution maps and the fractional value isomers indicates that dustfall in urban Beijing are affected by both current and historical usage of DDTs. It is worth noticing that there is possible application “dicofol-type of DDTs” in Beijing. The measured atmospheric deposition flux is 1.14×105 ngh−1 m−2 for HCHs and 1.47×105 ngh−1 m−2 for DDTs, respectively. However, when compared with atmospheric deposition flux, the volatilization flux estimated from concentrations in soils by fugacity model is significantly lower for HCHs (2.41ngh−1 m−2) and DDTs (0.07ngh−1 m−2). The net atmospheric flux to the soil suggests that the levels of HCHs and DDTs in soil are dominated by atmospheric deposition and the urban soil in Beijing would be a sink for HCHs and DDTs in the long term. [Copyright &y& Elsevier]

Atmospheric phosphine (PH3) fluxes from typical types of wetlands and PH3 concentrations in adjacent atmospheric air were measured. The seasonal distribution of PH3 in marsh and paddy fields were observed. Positive PH3 fluxes are significantly related to high air temperature (summer season) and increased vegetation. It is concluded that vegetation speeds up the liberation of PH3 from soils, while water coverage might function as a diffusion barrier from soils or sediments to the atmosphere. The concentrations of atmospheric PH3 (ngm−3) above different wetlands decrease in the order of paddy fields (51.8±3.1)>marsh (46.5±20.5)>lake (37.0±22.7)>coastal wetland (1.71±0.73). Highest atmospheric PH3 levels in marsh are found in summer. In paddy fields, atmospheric PH3 concentrations in flourishing stages are higher than those in slowly growing stages. [Copyright &y& Elsevier]

Field surveys were carried out from January 2007 to December 2008 to investigate seasonal variations of dissolved inorganic nitrogen (DIN) and phosphorus (DIP) transported to the Linjiang Bay of the Three Gorges Reservoir, China. The results revealed that both DIN and DIP exhibited large seasonal variability. DIN (dominated by NH-N) concentrations were drastically higher in the dry season than those in the rainy season, and the same seasonal patterns of DIP concentrations and DIN and DIP fluxes were observed but inverse to that of DIN concentrations. The interannual variation in DIN fluxes descended by 28.2% from 2007 to 2008, while DIP fluxes increased by 40.9%, which were closely constant with interannual changes in DIN and DIP concentrations, respectively. The study indicated that nutrient fluxes (DIN and DIP) were strongly correlated with both nutrient concentrations and river discharge, and the Linjiang Bay received approximately 3,416 × 10 kg DIN and 324 × 10 kg DIP every year. In addition, DIN mainly originated from point sources, but DIP originated from non-point sources. It is shown that to control point source pollution is the most effective step for water quality improvement and reducing nutrient loading inputs in the Linjiang Bay. [ABSTRACT FROM AUTHOR]

Bulk deposition samples were collected in remote, rural village and urban areas of Beijing–Tianjin region, North China in spring, summer, fall and winter from 2007 to 2008. The annually averaged PAHs concentration and deposition flux were 11.81 ± 4.61 μg/g and 5.2 ± 3.89 μg/m2/day respectively. PHE and FLA had the highest deposition flux, accounting for 35.3% and 20.7% of total deposition flux, respectively. More exposure risk from deposition existed in the fall for the local inhabitants. In addition, the PAHs deposition flux in rural villages (3.91 μg/m2/day) and urban areas (8.28 μg/m2/day) was 3.8 and 9.1 times higher than in background area (0.82 μg/m2/day), respectively. This spatial variation of deposition fluxes of PAHs was related to the PAHs emission sources, local population density and air concentration of PAHs, and the PAHs emission sources alone can explain 36%, 49%, 21% and 30% of the spatial variation in spring, summer, fall and winter, respectively. [Copyright &y& Elsevier]

Abstract: Fluxes of CO2 (FCO2) and energy (latent heat, LE; sensible heat, H) exchange between ecosystems and atmosphere, as measured by the eddy covariance technique, represent a fundamental data source for global-change research. However, little is known about the uncertainties of flux measurements at an ecosystem level in China. Here, we use data from six eddy covariance tower sites in ChinaFLUX, including two forested sites, three grassland sites, and one agricultural site, to conduct a cross-site analysis of random flux errors (RFEs) of FCO2, LE, and H. By using the daily-differencing approach, paired observations are obtained to characterize the random error in these measurements. Our results show that: (1) The RFEs of FCO2, LE, and H in different ecosystems of ChinaFLUX closely follow a double-exponential (Laplace) distribution, presumably due to a superposition of Gaussian distribution for high flux magnitude. (2) The RFEs of FCO2, LE, and H are not homogeneous and appear to be a linear function of flux magnitude. (3) Except for H, the RFEs of FCO2 and LE exhibit a distinct seasonal pattern. For FCO2, the dependence of RFEs on wind speed varies somewhat according to vegetation type, whereas for LE and H, there is no such dependence. The effect of temperature on RFEs is not statistically significant (P <0.05). Both the distribution and the relationship of RFEs with flux magnitude in ChinaFLUX are essentially in accord with those in AmeriFlux and CarboEurope. [ABSTRACT FROM AUTHOR]