The concentrations, congener profiles and spatial distribution of 13 phthalate esters (PAEs) in the freshwater fish ponds in the Pearl River Delta (PRD) region were investigated in water and sediment samples collect from 22 sites during Jul. 2016–Sept. 2017. The di-2-ethylhexyl phthalate (DEHP) was the predominant compounds in both water and sediment samples, accounting for 70.1% and 66.1% of ∑PAEs, respectively. The DEHP concentrations in the water samples collected from the sites of Zhongshan (35.7 μg/L), Jingmen (17.3 μg/L) and Nanhai (14.2 μg/L) were higher than that collected from other sampling sites (p <0.05), and exceed the Chinese environmental quality standards for surface water (DEHP, 8.00 μg/L). The concentrations of ΣPAEs (mean and median were 11.8 mg/kg dw and 7.95 mg/kg dw) in sediment was higher than that in sediment of river and estuary in the PRD region (p <0.05). The median concentrations of DEHP and di-n-butyl phthalate (DBP) exceeded recommend environmental risk limit (ERL) that posed a potential risk to the aquaculture fish pond environment in the PRD.

An accurate estimation of population exposure to particulate matter with an aerodynamic diameter <2.5 μm (PM₂.₅) is crucial to hazard assessment and epidemiology. This study integrated annual data from 1146 in-home air monitors, air quality monitoring network, public applications, and traffic smart cards to determine the pattern of PM₂.₅ concentrations and activities in different microenvironments (including outdoors, indoors, subways, buses, and cars). By combining massive amounts of signaling data from cell phones, this study applied a spatio-temporally weighted model to improve the estimation of PM₂.₅ exposure. Using Shanghai as a case study, the annual average indoor PM₂.₅ concentration was estimated to be 29.3 ± 27.1 μg/m³ (n = 365), with an average infiltration factor of 0.63. The spatio-temporally weighted PM₂.₅ exposure was estimated to be 32.1 ± 13.9 μg/m³ (n = 365), with indoor PM₂.₅ contributing the most (85.1%), followed by outdoor (7.6%), bus (3.7%), subway (3.1%), and car (0.5%). However, considering that outdoor PM₂.₅ makes a significant contribution to indoor PM₂.₅, outdoor PM₂.₅ was responsible for most of the exposure in Shanghai. A heatmap of PM₂.₅ exposure indicated that the inner-city exposure index was significantly higher than that of the outskirts city, which demonstrated that the importance of spatial differences in population exposure estimation.

Coastal wetlands are widely recognized as atmospheric methane sources. However, recent field studies suggest that some coastal wetlands could also act as methane sinks, but the mechanism is not yet clear. Here, we investigated methane oxidation with different electron acceptors (i.e., oxygen, nitrate/nitrite, sulfate, Fe(III) and Mn(IV)) in four coastal wetlands in China using a combination of molecular biology methods and isotopic tracing technologies. The geochemical profiles and in situ Gibbs free energies suggest that there was significant nitrite-dependent anaerobic oxidation of methane (nitrite-AOM) in the sub-surface sediments; this was subsequently experimentally verified by both the microbial abundance and activity. Remarkably, the methanotrophic communities seemed to exist in the sediments as layered structures, and the surface aerobic methane-oxidizing bacteria were able to take up atmospheric methane at a rate of 0.10–0.18 nmol CH₄ day⁻¹ cm⁻², while most, if not all, sedimentary methane was being completely consumed by anaerobic methanotrophs (23–58% by methane oxidizers in phylum NC10). These results suggest that coastal methane sinks might be governed by diverse microbial communities where NC10 methane oxidizers contributed significantly. This finding helps to better understand and predict the coastal methane cycle and reduce uncertainties in the estimations of the global methane flux.

Hydrogeochemistry and isotope hydrology were carried out to investigate the spatial distribution of fluoride (F−) and the mechanisms responsible for its enrichment in the western region of the Ordos basin, northwestern China. Sixty-two groundwater samples from the unconfined aquifer and fifty-six from confined aquifer were collected during the pre-monsoon (June 2016). Over 77% of groundwater samples from the unconfined aquifer (F− concentration up to 13.30 mg/L) and approximately 66% from confined aquifer (with a maximum F− concentration of 3.90 mg/L) exhibit F− concentrations higher than the Chinese safe drinking limit (1.0 mg/L). High-F− groundwater presents a distinctive hydrochemical characteristic: a high pH value and HCO3− concentration with Ca-poor and Na-rich. Mineral dissolution (e.g., feldspar, calcite, dolomite, fluorite), cation exchange and evaporation in the aquifers predominate the formation of groundwater chemistry, which are also important for F− enrichment in groundwater. Mixing with unconfined groundwater is a significant mechanism resulting in the occurrence of high-F− groundwater in confined aquifer. These findings indicate that physicochemical processes play crucial roles in driving F− enrichment and that may be useful for studying F− occurrence in groundwater in arid and semi-arid areas.

This study investigated the spatial and temporal distributions of particulate and gaseous air pollutants in a primary school in Beijing and assessed their health impact on the children. The results show that air quality inside the classroom was greatly affected by the input of outdoor pollutants; high levels of pollution were observed during both the heating and nonheating periods and indicate that indoor and outdoor air pollution posed a threat to the children's health. Traffic sources near the primary school were the main contributors to indoor and outdoor pollutants during both periods. Moreover, air quality in this primary school was affected by coal combustion and atmospheric reactions during the heating and nonheating periods, respectively. Based on the estimation by exposure-response functions and the weighting of indoor and outdoor pollutants during different periods, the levels of PM2.5, PM 10 and O3 at school had adverse respiratory health effects on children. Longer exposures during the nonheating period contributed to higher health risks. These results emphasized that emission sources nearby had a direct impact on air quality in school and children's respiratory health. Therefore, measures should be taken for double control on air pollution inside and outside the classroom to protect children from it.

A nationwide survey, including 75 sludge samples and 18 wastewater samples taken from different wastewater treatment plants (WWTPs) from 23 cities, was carried out to investigate the occurrence and composition profiles of polycyclic aromatic hydrocarbons (PAHs) in China. In total, the concentrations of ∑16PAHs in sludge ranged from 565 to 280,000 ng/g (mean: 9340 ng/g) which was at a moderate level in the world. The composition profiles of PAHs were characterized by 3- and 4-ring PAHs in textile dyeing sludge and 4- and 5-ring PAHs in domestic sludge. Significant variations in regional distribution of PAHs were observed. Both the principal components analysis and diagnostic ratios revealed that vehicle exhaust, coal and natural gas combustion were the main sources of PAHs in China. The estimated concentrations of PAHs were 3820 ng/L and 1120 ng/L in influents and effluents of the WWTPs, respectively. The high toxic equivalent quantity (TEQ) values of PAHs are ascribed to the high PAH levels. Risk quotient values (RQs) in sludge indicated that there was low potential risk to soil ecosystem after sludge had been applied one year except for indeno [1,2,3-cd]pyrene (IcdP) detected in Huaibei, Anhui province.

Forest ecosystem has long been suggested as a vital component in the global mercury (Hg) biogeochemical cycling. However, there remains large uncertainties in understanding total Hg (THg) and methylmercury (MeHg) variations and their controlling factors during the whole hydrological processes in forest ecosystems. Here, we quantified Hg mass flow along hydrological processes of wet deposition, throughfall, stemflow, litter leachate, soil leachate, surface runoff, and stream, and litterfall Hg deposition, and air-forest floor elemental Hg (Hg⁰) exchange flux to set up a Hg mass balance in a subtropical forest of China. Results showed that THg concentration in stream was lower than that in wet deposition, while an opposite characteristic for MeHg concentration, and both THg and MeHg fluxes of stream were lower than those of wet deposition. Variations of THg and MeHg in throughfall and litter leachate had strong direct and indirect effects on controlling variations of THg and MeHg in surface runoff, soil leachate and stream, respectively. Especially, the net Hg methylation was suggested in the forest canopy and forest floor layers, and significant particulate bound Hg (PBM) filtration was observed in soil layers. The Hg mass balance showed that the litterfall Hg deposition was the main Hg input for forest floor Hg, and the elemental Hg vapor (Hg⁰) re-emission from forest floor was the dominant Hg output. Overall, we estimated the net THg input flux of 13.8 μg m⁻² yr⁻¹ and net MeHg input flux of 0.6 μg m⁻² yr⁻¹ within the forest ecosystem. Our results highlighted the important roles of forest canopy and forest floor to shape Hg in output flow, and the forest floor is a distinct sink of MeHg.

The purpose of this study is to investigate the potential associations between air pollution and dry eye disease (DED). Data of outdoor air pollutants and meteorology as well as outpatient visits for DED were collected. A time-stratified case-crossover approach was used to analyze the associations between ambient air pollutants and outpatient visits for DED. Among the 5062 DED patients studied, 65.45% were female and 34.55% were male. In the single-pollutant model, significant associations were observed between an increase of 10 μg/m³ in the concentrations of fine-particulate matter with a median aerometric diameter of less than 10 μm (PM₁₀), fine-particulate matter with a median aerometric diameter of less than 2.5 μm (PM₂.₅), sulfur dioxide (SO₂), nitrogen dioxide (NO₂), and carbon monoxide (CO) and outpatient visits for DED. These results were consistent with those of the multipollutant model. The strongest associations between air pollutants and patient visits were observed during the cold season and in patients aged 21–40. The significant association between air pollutants (PM₁₀, PM₂.₅, SO₂, NO₂, and CO) and DED outpatient visits indicates the importance of increased environmental protection.

Fine particulate matter (PM₂.₅) pollution in Eastern China (EC) has raised concerns due to its adverse effects on air quality, climate, and human health. This study investigated the long-term variation trend in satellite-derived PM₂.₅ concentrations and how it was related to pollutant emissions and meteorological parameters over EC and seven regions of interest (ROIs) during 1998–2016. Over EC, the annual mean PM₂.₅ increased before 2006 due to the enhanced emissions of primary PM₂.₅, NOₓ and SO₂, but decreased with the reduced SO₂ emissions after 2006 evidently in response to China's clean air policies. In addition, results from statistical analyses indicated that in the North China Plain (NCP), Northeast China (NEC), Sichuan Basin (SCB) and Central China (CC) planetary boundary layer height (PBLH) was the dominant meteorological driver for the PM₂.₅ decadal changes, and in the Pearl River Delta (PRD) wind speed is the leading factor. Overall, the variation in meteorological parameters accounted for 48% of the variances in PM₂.₅ concentrations over EC. The population-weighted PM₂.₅ over EC increased from 36.4 μg/m³ in 1998–2004 (P1) to 49.4 μg/m³ in 2005–2010 (P2) then decreased to 46.5 μg/m³ in 2011–2016 (P3). In the NCP and NEC, the percentages of the population living above the World Health Organization (WHO) Interim Target-1 (IT-1, 35 μg/m³) have risen steadily over the past 20 yr, reaching maxima of 97.3% and 78.8% in P3, respectively, but decreases of ∼30% from P2 to P3 were found for the SCB and PRD.

Nitrogen (N) addition can change physicochemical properties and biogeochemical processes in soil, but whether or not these changes further affect the transport and transformation of heavy metal speciation is unknown. Here, a long-term (2004–2016) field experiment was conducted to assess the responses of different heavy metal speciation in three soil aggregate fractions to N additions in a temperate agroecosystem of North China. The organic matter turnover time was quantified based on changes in δ13C following the conversion from C3 (wheat) to C4 crop (corn). Averagely, N addition decreases and increases the heavy metal contents in bioavailable and organic bound fractions by 27.5% and 16.6%, respectively, suggesting N addition promotes the transformation of heavy metal speciation from bioavailable to organic bound, and such a promotion in a small aggregate fraction is more remarkable than that in a large aggregate fraction. The transformations of heavy metal speciation from bioavailable to organic bound in all soil aggregate fractions are largely dependent on the increments in the turnover time of organic matter. The increase in organic matter turnover time induced by N addition may inhibit the desorption of heavy metals from organic matter by prolonging the interaction time between heavy metals and organic matter and enhance the capacity of organic matter to adsorb heavy metals by increasing the humification degree and functional group. Our work can provide insights into the accumulation, migration, and transformation of heavy metals in soils in the context of increasing global soil N input from a microenvironmental perspective.