Grain transportation and consumption reshapes the α-HCH exposure picture of China.

Socio-economic activities like food trade can increase the uncertainty of human risk of persistent organic pollutants (POPs). We compared the change in model predicted α-hexachlorocyclohexane (α-HCH) cancer risk (CR) with and without grain trade in mainland China. In scenario without grain logistics, α-HCH moved fast away from southern and southeastern China via northward atmospheric transport. However, the grain logistics from northeastern China delivers the α-HCH previously accumulated in northeastern sink back to densely populated areas in recent years, which enhance CR by >50 % in the southern seaboard of China. The northward movement of grain production center and recent grain deficiency in southern provinces induced by dietary pattern changes is identified as the major driving factors of the reversed transport of α-HCH. The finding highlights the potential of socio-economic activities that can otherwise offset the risk reduction effect of the geochemical cycle of POPs.

Increase in Agricultural-Derived NHx and Decrease in Coal Combustion-Derived NOx Result in Atmospheric Particulate N-NH4+ Surpassing N-NO3- in the South China Sea.

The atmospheric deposition of anthropogenic active nitrogen significantly influences marine primary productivity and contributes to eutrophication. The form of nitrogen deposition has been evolving annually, alongside changes in human activities. A disparity arises between observation results and simulation conclusions due to the limited field observation and research in the ocean. To address this gap, our study undertook three field cruises in the South China Sea in 2021, the largest marginal sea of China. The objective was to investigate the latest atmospheric particulate inorganic nitrogen deposition pattern and changes in nitrogen sources, employing nitrogen-stable isotopes of nitrate (δ15N-NO3-) and ammonia (δ15N-NH4+) linked to a mixing model. The findings reveal that the N-NH4+ deposition generally surpasses N-NO3- deposition, attributed to a decline in the level of NOx emission from coal combustion and an upswing in the level of NHx emission from agricultural sources. The disparity in deposition between N-NH4+ and N-NO3- intensifies from the coast to the offshore, establishing N-NH4+ as the primary contributor to oceanic nitrogen deposition, particularly in ocean background regions. Fertilizer (33 ± 21%) and livestock (20 ± 6%) emerge as the primary sources of N-NH4+. While coal combustion continues to be a significant contributor to marine atmospheric N-NO3-, its proportion has diminished to 22 (Northern Coast)-35% (background area) due to effective NOx emission controls by the countries surrounding the South China Sea, especially the Chinese Government. As coal combustion's contribution dwindles, the significance of vessel and marine biogenic emissions grows. The daytime higher atmospheric N-NO3- concentration and lower δ15N-NO3- compared with nighttime further underscore the substantial role of marine biogenic emissions.

Molecular signatures and formation mechanisms of water-soluble chromophores in particulate matter from Karachi in Pakistan.

Excitation-emission matrix (EEM) fluorescence spectroscopy is a widely-used method for characterizing the chemical components of brown carbon (BrC). However, the molecular basics and formation mechanisms of chromophores, which are decomposed by parallel factor (PARAFAC) analysis, are not yet fully understood. In this study, we characterized the water-soluble organic carbon (WSOC) in aerosols collected from Karachi, Pakistan, using EEM spectroscopy and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). We identified three PARAFAC components, including two humic-like components (C1 and C2) and one phenolic-like species (C3). We determined the molecular families associated with each component by performing Spearman correlation analysis between FT-ICR MS peaks and PARAFAC component intensities. We found that the C1 and C2 components were associated with nitrogen-enriched compounds, where C2 with the longest emission wavelength exhibited a higher level of aromaticity, N content, and oxygenation than C1. The C3 associated formulas have fewer nitrogen-containing species, a lower unsaturation degree, and a lower oxidation state. An oxidation pathway was identified as an important process in the formation of C1 and C2 components at the molecular level, particularly for the assigned CHON compounds associated with the gas-phase oxidation process, despite their diverse precursor types. Numerous C2 formulas were found in the "potential BrC" region and overlapped with the BrC-associated formulas. It can be inferred that the compounds that fluoresce C2 contributed considerably to the light absorption of BrC. These findings are essential for future studies utilizing the EEM-PARAFAC method to explore the sources, processes, and compositions of atmospheric BrC.

Chemical characteristics, distribution patterns, and source apportionment of particulate elements and inorganic ions in snowpack in Harbin, China.

Snowpack, which serves as a natural archive of atmospheric deposition of multiple pollutants, is a practical environmental media that can be used for assessing atmospheric records and input of the pollutants to the surface environments and ecosystems. A total of 29 snowpack samples were collected at 20 sampling sites covering three different functional areas of a major city (Harbin) in Northeast China. Two samples at the "snow layer" and one or two samples at the "particulate layer" were collected at each sampling site in the industrial areas characterized by multi-layer snowpack, and only one sample at the "snow layer" was collected at each sampling site in the cultural and recreational as well as agricultural areas. The snow contents of 31 elements (Na, Mg, Al, K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Y, Cd, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Pb) and six major water-soluble inorganic ions (WSIIs, NH4+, K+, Ca2+, NO2-, NO3-, and SO42-) were analyzed. The total mass of the measured elements is dominated (95.8%-99.2%) by crustal elements. Heavy metals only account for 0.77%-4.07% of the total mass of the elements, but are occasionally close to or even above the standard limit in the "Environmental Quality Standards for Surface Water" of China (GB3838-2002). SO42- and Ca2+ are the main anion and cation, accounting for 34.9%-81.1% and 1.43%-29.9%, respectively, of the measured total ions. Total atmospheric deposition of crustal elements and heavy metals is dominated by wet deposition in areas near the petrochemical plant and by dry deposition in areas near the cement plant. Coal combustion, industrial emissions, and traffic-related activities lead to the enrichment of heavy metals in the snowpacks of urban and suburban areas, while coal combustion and biomass burning contribute to pollution in rural areas. The cities and regions situated in the western, northwestern, northern, and northeastern directions from Harbin are potential source regions of these pollutant species.

Quantifying the Nitrogen Sources and Secondary Formation of Ambient HONO with a Stable Isotopic Method.

Nitrous acid (HONO) is a reactive gas that plays an important role in atmospheric chemistry. However, accurately quantifying its direct emissions and secondary formation in the atmosphere as well as attributing it to specific nitrogen sources remains a significant challenge. In this study, we developed a novel method using stable nitrogen and oxygen isotopes (δ15N; δ18O) for apportioning ambient HONO in an urban area in North China. The results show that secondary formation was the dominant HONO formation processes during both day and night, with the NO2 heterogeneous reaction contributing 59.0 ± 14.6% in daytime and 64.4 ± 10.8% at nighttime. A Bayesian simulation demonstrated that the average contributions of coal combustion, biomass burning, vehicle exhaust, and soil emissions to HONO were 22.2 ± 13.1, 26.0 ± 5.7, 28.6 ± 6.7, and 23.2 ± 8.1%, respectively. We propose that the isotopic method presents a promising approach for identifying nitrogen sources and the secondary formation of HONO, which could contribute to mitigating HONO and its adverse effects on air quality.

[Changes in Health Risks and Pollution Sources of Atmospheric PM2.5-bound Metals in a Background Site in North China].

To explore the change features of PM2.5-bound metals in a background site of North China in the past ten years, 71 and 160 samples were collected from December 2011 to January 2013 (period Ⅰ) and from September 2019 to November 2021 (period Ⅱ) in Tuoji Island National Atmospheric Monitoring Station, respectively.The concentration of metals sampled was determined using ICP-MS, and the concentrations, sources, and health risks of heavy metals were compared. The results revealed that the average concentration of PM2.5 was (54.06±39.71) µg·m-3during period Ⅱ, which was 3.53 ng·m-3 lower than that during period Ⅰ. The concentrations of Zn, Mn, As, Pb, and V in stage Ⅱ decreased by 54.53, 172.63, 0.8, 79.06, and 3.81 ng·m-3, respectively, whereas the concentrations of Cr, Cu, Cd, and Ni increased by 2.01, 5.42, 3.03, and 3.55 ng·m-3, respectively. The PMF model results indicated that the biggest contributor to PM2.5-bound metal was industrial emissions (32.32%), followed by coal combustion (27.47%), vehicle emissions (23.70%), ship emissions (9.69%), and dust sources (6.83%) during period Ⅱ. The contribution ratio of dust sources and ship emissions decreased by 20.73% and 8.83%, respectively, whereas for coal combustion and industrial emissions it increased by 2.50% and 13.52%, respectively, when compared with that during period Ⅰ. The total carcinogenic risk induced by PM2.5-bound heavy metals of period Ⅱ increased, with the highest contributions by Cr and Cd. The total non-carcinogenic risk decreased, with Mn contributing the most. Therefore, in the process of air pollution control, the control of pollution sources of heavy metals such as Cr and Mn should be reinforced.

Isotopic comparison of ammonium between two summertime field campaigns in 2013 and 2021 at a background site of North China.

Ammonia (NH3) is the primary atmospheric alkaline gas, playing a crucial role in the atmospheric chemistry. Recently, non-agricultural emissions have been identified as the dominant sources of NH3 in urban areas. However, few studies have quantified the contributions of different sources to regional NH3. This study conducted two summertime field observations in 2013 and 2021 at a background site of North China to comprehensively explore the regional variations in concentration, nitrogen isotope composition (δ15N), and sources of ammonium (NH4+). The results indicate that NHx (NHx = NH3 + NH4+) concentration has increased in 2021, but the fNH4+ (NH4+/ NHx) has decreased significantly. The δ15N-NH4+ values show a significant increase, ranging from -4.7 ± 8.1 ‰ to +12.0 ± 2.4 ‰. The increase can be attributed to two primary factors: changes in fNH4+ resulting from the reduction of atmospheric acid gases and alterations in the sources of NH3. Bayesian simulation analysis reveals substantial variations in NH3 sources between 2013 and 2021 observations. Non-agricultural sources have significantly increased their contribution to NHx concentration, with vehicle exhaust and NH3 slip experiencing growth rates of 187 % and 104 %, respectively. Our results confirm the dominate contribution of non-agricultural sources to regional NH3 at the present stage and propose relevant mitigation strategies, which would provide essential insights for reducing NH3 emissions in North China.

Provenance of Aerosol Black Carbon over Northeast Indian Ocean and South China Sea and Implications for Oceanic Black Carbon Cycling.

Aerosol black carbon (BC) is a short-lived climate pollutant. The poorly constrained provenance of tropical marine aerosol BC hinders the mechanistic understanding of extreme climate events and oceanic carbon cycling. Here, we collected PM2.5 samples during research cruise NORC2016-10 through South China Sea (SCS) and Northeast Indian Ocean (NEIO) and measured the dual-carbon isotope compositions (δ13C-Δ14C) of BC using hydrogen pyrolysis technique. Aerosol BC exhibits six different δ13C-Δ14C isotopic spaces (i.e., isotope provinces). Liquid fossil fuel combustion, from shipping emissions and adjacent land, is the predominant source of BC over isotope provinces "SCS close to Chinese Mainland" (53.5%), "Malacca Strait" (53.4%), and "Open NEIO" (40.7%). C3 biomass burning is the major contributor to BC over isotope provinces "NEIO close to Southeast Asia" (55.8%), "Open NEIO" (41.3%), and "Open SCS" (40.0%). Coal combustion and C4 biomass burning show higher contributions to BC over "Sunda Strait" and "Open SCS" than the others. Overall, NEIO near the Bay of Bengal, Malacca Strait, and north SCS are three hot spots of fossil fuel-derived BC; the first two areas are also hot spots of biomass-derived BC. The comparable δ13C-Δ14C between BC in aerosol and dissolved BC in surface seawater may suggest atmospheric BC deposition as a potential source of oceanic dissolved BC.

Quantitative evaluation for the sources and aging processes of organic aerosols in urban Guangzhou: Insights from a comprehensive method of dual­carbon isotopes and macro tracers.

Organic carbon aerosol (OC) is a pivotal component of PM2.5 in the atmospheric environment, yet its emission sources and atmospheric behaviors remain poorly constrained in many regions. In this study, a comprehensive method based on the combination of dual­carbon isotopes (13C and 14C) and macro tracers was employed in the PRDAIO campaign performed in the megacity of Guangzhou, China. The 14C analysis showed that 60 ± 9 % of OC during the sampling campaign was associated with non-fossil sources such as biomass burning activities and biogenic emissions. It should be noted that this non-fossil contribution in OC would significantly decrease when the air masses came from the eastern cities. Overall, we found that non-fossil secondary OC (SOCNF) was the largest contributor (39 ± 10 %) to OC, followed by fossil secondary OC (SOCFF: 26 ± 5 %), fossil primary OC (POCFF: 14 ± 6 %), biomass burning OC (OCbb: 13 ± 6 %) and cooking OC (OCck: 8 ± 5 %). Also, we established the dynamic variation of 13C as a function of aged OC and the volatile organic compounds (VOCs) oxidized OC to explore the impact of aging processes on OC. Our pilot results showed that atmospheric aging was highly sensitive to the emission sources of seed OC particles, with a higher aging degree (86 ± 4 %) when more non-fossil OC particles were transferred from the northern PRD.

Regional monitoring of biomass burning using passive air sampling technique reveals the importance of MODIS unresolved fires.

Field-based sampling can provide more accurate evaluation than MODIS in regional biomass burning (BB) emissions given the limitations of MODIS on unresolved fires. Polyurethane foam-based passive air samplers (PUF-PASs) are a promising tool for collecting atmospheric monosaccharides. Here, we deployed PUF-PASs to monitor monosaccharides and other BB-related biomarkers and presented a dataset of 31 atmospheric BB-related biomarkers in the Indo-China Peninsula (ICP) and Southwest China. The peak concentrations of monosaccharides in the ICP occurred before monsoon season. The highest concentrations were in the eastern Mekong plain, while the lowest were along the eastern coast. BB-related biomarkers displayed elevated concentrations after April, particularly in the monsoon season; however, fewer active fires were recorded by MODIS. This revealed the importance of MODIS unresolved fires (e.g., indoor biofuel combustion, small-scale BB incidents, and charcoal fires) to the regional atmosphere. The PAS derived levoglucosan concentrations indicated that, with the inclusion of MODIS unresolved fires, the estimated top-down emissions of PM (4194-4974 Gg/yr), OC (1234-1719 Gg/yr) and EC (52-384 Gg/yr) would be higher than previous bottom-up estimations in the ICP. Future studies on these MODIS unresolved fires and regional monitoring data of BB are vital for improving the modeling of regional BB emissions.

Non-agricultural source dominates the ammonium aerosol in the largest city of South China based on the vertical δ15N measurements.

Ammonia (NH3) is the most prevalent alkaline gas in the atmosphere and plays a critical role in air pollution and public health. However, scientific debate remains over whether agricultural emissions (e.g., livestock and fertilizer application) dominate NH3 in urban atmosphere in China, which is one of the largest NH3 emitters in the world. In this study, we first simultaneously collected the fine atmospheric particles (PM2.5) at two heights (ground and 488 m) using the atmospheric observatories in Canton Tower, Guangzhou city, China for the measurements of stable nitrogen isotope composition in ammonium (δ15N-NH4+). Our results showed that the average δ15N-NH4+ value at the ground and the 488 m observatory were 16.9 ‰ and 3.8 ‰, respectively, implying that NH4+ aerosols between the two heights probably have different sources. Moreover, we found that the δ15N-NH4+ value would sharply decrease to -16.7 ‰ when the air masses came from western Guangzhou, where the urbanization is limited compared to other surrounding areas. The Bayesian mixing model indicated that NH4+ aerosol at the ground observatory was mainly derived from non-agricultural activities (76 %, e.g., vehicular exhaust), with the rest from agricultural sources (24 %). As for the 488 m observatory, the contribution of non-agricultural sources was 53 %, which is lower than the ground observatory. This is expected as the lower air receives more impacts from the local urban emission. However, the current "bottom-up" emission inventory illustrates that only ~20 % NH3 in Guangzhou is associated with non-agricultural emissions, which is significantly lower than our δ15N-based results. Overall, our findings strongly imply that non-agricultural sources dominate the urban NH3 in Guangzhou or maybe in adjacent cities of the Pearl River Delta region as well, suggesting that the emission inventory of NH3 in this region probably is urgently needed to be revisited in future studies.

Nitrogen isotopic composition of NOx from residential biomass burning and coal combustion in North China.

Stable nitrogen isotope (δ15N) technology has often been used as a powerful tool to separate nitrogen oxides (NOx) produced by residential combustion (i.e., biomass burning and coal combustion) from other sources. However, the insufficient measurement of δ15N-NOx fingerprints of these emissions limits its application, especially in North China where residential emissions are significant. This study conducted combustion experiments to determine the δ15N-NOx of typical residential fuels in North China, including ten biomass fuels and five types of coal. The results showed that the δ15N of biomass varied between -6.9‰ and 2.3‰, which was lower than the δ15N of residential coal (-0.2‰-4.6‰). After combustion, the δ15N of biomass residues increased greatly, while that of coal residues showed no significant upward trend (p > 0.05). The δ15N-NOx produced by biomass burning ranged from -5.6‰ to 3.2‰ (-0.4‰ ± 2.4‰), showing a significant linear relation with δ15N-biomass. Comparatively, the δ15N-NOx derived from residential coal combustion was much higher (16.1‰ ± 3.3‰), ranging from 11.7‰ to 19.7‰. It was not well correlated with δ15N-coal, and only slightly lower than the estimated δ15N-NOx of industrial coal combustion (17.9‰, p > 0.05). These observations indicate that the δ15N-NOx of residential coal combustion is a result of the mixture of thermal- and fuel-released NOx. Based on the isotopic characteristics observed in this study, we analyzed the reported δ15N-NOx, and provided more statistically robust δ15N-NOx distributions for biomass burning (1.3‰ ± 4.3‰; n = 101) and coal combustion (17.9‰ ± 3.1‰; n = 26), which could provide guidance for scientific studies aiming to quantify the origin of NOx in North China and in other regions.

Exploring source footprint of Organophosphate esters in the Bohai Sea, China: Insight from temporal and spatial variabilities in the atmosphere from June 2014 to May 2019.

Organophosphate esters (OPEs) are still produced and used in large quantities in the world-wide, and the environmental burden and behavior have generated widespread concern, especially in some large-scale waterbodies. This study conducted a comprehensive assessment on the temporal and spatial variabilities and budget of OPEs to trace the source for the Bohai Sea (BS), based on a 5-year seasonal monitoring campaign (June 2014 to May 2019) of 12 atmospheric sites around the BS and our previous studies. The average concentration of Σ10OPEs in atmosphere during the sampling period was 7.65 ± 6.42 ng m-3, and chlorinated OPEs were the major compounds. The Seasonal-Trend decomposition procedure based on Loess (STL) analyzed that during the 5-year sampling period, the atmospheric concentrations of Σ10OPEs had a slightly increasing trend with a rate of + 0.092 ng m-3 yr-1, and the seasonal concentrations had a distinct seasonal distribution. The highest concentration of Σ10OPEs was observed at the sampling site of Dalian, followed by Tianjin, Yantai, and Beihuangcheng. The estimation of the fugacity ratios and air-water gas exchange fluxes established that the concentration levels of two major components of chlorinated OPEs (tris-(2-chloroethyl) phosphate (TCEP) and tris-(1-chloro-2-propyl) phosphate (TCPP)) in the atmosphere were dominated by their volatilization from BS's seawater (1.24 ± 0.46 t yr-1 for TCEP and 5.15 ± 2.15 t yr-1 for TCPP), with 73% deriving from the coastal seawater. The budget assessment suggested that the volatile fluxes of TCEP and TCPP accounted for 8% and 29% of their storages (15.6 ± 5.32 t for TCEP and 17.6 ± 6.70 t for TCPP) in the BS seawater, which were mainly contributed by continental river input (20% for TCEP and 42% for TCPP). The efforts indicated that river inputs of TCEP and TCPP needed to be paid more attention for the improvement of environmental quality of the BS.

Dual-carbon isotope constraints on source apportionment of black carbon in the megacity Guangzhou of the Pearl River Delta region, China for 2018 autumn season.

Black carbon (BC) aerosol negatively affects air quality and contributes to climate warming globally. However, little is known about the relative contributions of different source control measures to BC reduction owing to the lack of powerful source-diagnostic tools. We combine the fingerprints of dual-carbon isotope using an optimized Bayesian Markov chain Monte Carlo (MCMC) scheme and for the first time to study the key sources of BC in megacity Guangzhou of the Pearl River Delta (PRD) region, China in 2018 autumn season. The MCMC model-derived source apportionment of BC shows that the dominant contributor is petroleum combustion (39%), followed by coal combustion (34%) and biomass burning (27%). It should be noted that the BC source pattern is highly sensitive to the variations of air masses transported with an enhanced contribution of fossil source from the eastern area, suggesting the important impact of regional atmospheric transportation on the BC source profile in the PRD region. Also, we further found that fossil fuel combustion BC contributed 84% to the total BC reduction during 2013-2018. The response of PM2.5 concentration to the 14C-derived BC source apportionment is successfully fitted (r = 0.90) and the results predicted that it would take ∼6 years to reach the WHO PM2.5 guideline value (10 µg m-3) for the PRD region if the emission control measures keep same as they are at present. Taken together, our findings suggest that dual-carbon isotope is a powerful tool in constraining the source apportionment of BC for the evaluations of air pollution control and carbon emission measures.

Feasibility of source identification by DOM fingerprinting in marine pollution events.

Accurate source identification is the first step of pollution control in environmental emergency management, especially in marine pollution events. Dissolved organic matter (DOM) absorption and fluorescence (excitation-emission matrices, EEMs) analyses were applied to trace contaminant sources for a pollution event that occurred along the coast of Laizhou Bay, Bohai Sea. Parallel factor analysis (PARAFAC) of the EEMs identified four fluorescent components: terrestrial humic-like (C1), tryptophan-like (C2), and a mixture of terrestrial and marine humic-like (C3) and tyrosine-like (C4) components. The relationships among C1 to C4 and quality indices indicated that the DOM originated from terrestrial input and biological activity. The EEMs-PARAFAC results accompanied by the optical characteristics of DOM and fingerprinting demonstrated that the marine pollution event occurred was from enterprise emissions. The numerical simulation confirmed the reliability of EEMs-PARAFAC modeling for DOM fingerprinting of pollution sources in polluted regions. This study provided a feasible method for source recognition in marine pollution events.

Coastal eutrophication in China: Trend, sources, and ecological effects.

Eutrophication in coastal waters caused by excess nutrient inputs has occurred widely on a global scale. Due to the rapid economic development over the last four decades, most of the Chinese coastal waters have experienced a eutrophic process. Major observed trends of coastal eutrophication include two periods, a slow development from the 1970s to 1990s and a fast development after 2000, with major contributions of increased nitrogen (N) and phosphorus (P) from river inputs, atmospheric deposition, and submarine groundwater discharge (SGD). Nutrient composition and stoichiometry have been significantly changed, including increased ammonium, bioavailable organic N and P, and asymmetric ratios between N, P and silicate (Si). Most of these changes were related to the rapid increases in population density, fertilizer application, sewage discharge, aquaculture and fossil fuel combustion, and have resulted in distinctly increased harmful algal blooms. Coastal eutrophication combined with the effects of climate change is projected to continually grow in coming decades. Targeted research is therefore needed on nitrogen reduction and control, potential adaptation strategies and the consequences for ecosystems and economic sustainability.

Molecular Dynamics and Light Absorption Properties of Atmospheric Dissolved Organic Matter.

The light-absorbing organic aerosol referred to as brown carbon (BrC) affects the global radiative balance. The linkages between its molecular composition and light absorption properties and how environmental factors influence BrC composition are not well understood. In this study, atmospheric dissolved organic matter (ADOM) in 55 aerosol samples from Guangzhou was characterized using Fourier transform ion cyclotron resonance mass spectrometry and light absorption measurements. The abundant components in ADOM were aliphatics and peptide-likes (in structure), or nitrogen- and sulfur-containing compounds (in elemental composition). The light absorption properties of ADOM were positively correlated with the levels of unsaturated and aromatic structures. Particularly, 17 nitrogen-containing species, which are identified by a random forest, characterized the variation of BrC absorption well. Aggregated boosted tree model and nonmetric multidimensional scaling analysis show that the BrC composition was largely driven by meteorological conditions and anthropogenic activities, among which biomass burning (BB) and OH radical were the two important factors. BrC compounds often accumulate with elevated BB emissions and related secondary processes, whereas the photolysis/photooxidation of BrC usually occurs under high solar radiance/•OH concentration. This study first illuminated how environmental factors influence BrC at the molecular level and provided clues for the molecular-level research of BrC in the future.

Decabromodiphenyl Ether versus Decabromodiphenyl Ethane: Source, Fate, and Influencing Factors in a Coastal Sea Nearing Source Region.

Both decabromodiphenyl ether (BDE 209) and decabromodiphenyl ethane (DBDPE) are still produced in large quantities in China, especially in the Shandong Province closed to the Bohai Sea (BS). This study conducted a comprehensive investigation of the distribution and budget of brominated flame retardants (BFRs) in the BS. BDE 209 was the predominant BFR in most of the investigated rivers flowing into the BS, although DBDPE exceeded BDE 209 in certain rivers as a result of the replacement of BDE 209 with DBDPE in North China. The spatial distributions of BFRs in the rivers were controlled by the proximity of the BFR manufacturing base and the extent of urbanization. BFRs' spatial distribution in the BS was influenced by a combination of land-based pollution sources, environmental parameters (e.g., suspended particulate matter, particulate organic carbon, and particulate black carbon), and hydrodynamic conditions. The spatial variation trend of BDE 209/DBDPE ratios in various environmental media provided useful information. Vertically, the BDE 209/DBDPE ratio decreased from the seawater surface layer to the sediment, indicating their differential transport in the BS. A multi-box mass balance model and analysis of BDE 209 showed that degradation was the primary sink of BFRs in seawater (∼68%) and surface sediment (∼72%) in the BS.

Assessing the emission sources and reduction potential of atmospheric ammonia at an urban site in Northeast China.

Atmospheric ammonium and ammonia have brought negative environmental impacts and adverse health effects. However, ammonia emissions are generally less regulated worldwide. This study analyzed ammonium pollution character, quantified the dominant ammonia emission sources, and assessed ammonia reduction potential in urban Harbin (China). The results showed that ammonium recorded low concentration in the non-heating season (1.34 ± 1.57 µg/m3), and recorded sharply increased concentration (6.50 ± 7.02 µg/m3) and relative abundance in the heating season. It was closely correlated with vehicle-related pollutants (CO) in non-heating season, while with biomass burning-related pollutants (K+, Cl-) in the heating season. Bayesian Mixing Model emphasized the increasing contribution of biomass burning and decreasing contribution of fertilizer as the pollution levels escalate. The results from the thermodynamic equilibrium model showed that a 50%-60% ammonium decrease could bring marketable decrements of the aerosol pH, aerosol water content, ammonium nitrate concentration, and inorganic ion mass. The results of this study would provide scientific bases for ammonia emission reduction and haze pollution control in urban Harbin.

Dual-isotope-based source apportionment of nitrate in 30 rivers draining into the Bohai Sea, north China.

Excessive nitrate (NO3-) in rivers can lead to water quality deterioration, and can also be directly input into estuaries and oceans, thus posing a serious threat to the stability of their ecosystems. In this study, the concentration, isotopes and sources of NO3- in 30 rivers discharging into the Bohai Sea were comprehensively investigated. The mean concentration of NO3--N was 2.24 ± 2.11 mg L-1, with obvious seasonal and spatial variations. In total, 104.24 kt of NO3--N was discharged into the Bohai Sea annually, to which the Yellow River Basin and Liao River Basin made the largest contributions. The range of δ15N-NO3- was -1.1‰ to +33.2‰ (mean value, +11.4 ± 5.0‰), with no significant seasonal or spatial differences; the mean value of δ18O-NO3- was +9.4 ± 7.2‰, with much higher values seen in June. Based on the MixSIAR model, manure (24.3 ± 7.5%) and sewage (19.1 ± 14.5%) were the primary sources of NO3- in the 30 rivers, followed by NO3- fertilizers (16.3 ± 12.5%), soil N (15.5 ± 11.9%), atmospheric deposition of NO3- (13.5 ± 5.7%) and NH4+ fertilizers (11.4 ± 8.9%). This finding highlights the vital roles of sewage and manure management in riverine NO3-. Using a mathematical method, the contributions of various sources to each river were simulated. The results indicated that management of the Yellow River, Daliao River, Liao River, and Xiaoqing River is more urgently needed than that of other rivers to control Bohai NO3- pollution. We believe that this finding will provide guidance for scientific management of NO3- pollution in these 30 rivers and the Bohai Sea.