Detailed chemical characterization of fine aerosols (PM2.5) is important for reducing air pollution in densely populated areas, such as the Yangtze River Delta region in China. This study systematically analyzed PM2.5 samples collected during November 2015 to April 2016 in urban Yangzhou using a suite of techniques, in particular, an Aerodyne soot particle aerosol mass spectrometry (SP-AMS). The techniques used here reconstructed the majority of total PM2.5 measured where extracted species comprised on average 91.2%. Source analyses of inorganic components showed that secondary nitrate, sulfate and chloride were the major species, while primary sources including biomass burning, coal combustion, traffic, industry and re-suspended dust due to nearby demolition activities, could contribute to other species. EC-tracer method estimated that the organic matter (OM) was composed of 65.4% secondary OM (SOM) and 34.6% primary OM (POM), while the SP-AMS analyses showed that the OM was comprised of 60.3% water-soluble OM (WSOM) and 39.7% water-insoluble OM (WIOM). Correlation analyses suggested that WSOM might be rich in secondary organic species, while WIOM was likely mainly comprised of primary organic species. We further conducted positive matrix factorization (PMF) analyses on the WSOM, and identified three primary factors including traffic, cooking and biomass burning, and two secondary factors. We found the secondary factors dominated WSOM mass (68.1%), and their mass contributions increased with the increase of WSOM concentrations. Relatively small contribution of primary sources to WSOM was probably due to their low water solubility, which should be investigated further in future. Overall, our findings improve understanding of the complex aerosol sources and chemistry in this region.

A main challenge in ecological risk assessment is to account for the impact of multiple stressors. Nuclear facilities can release both radiological and chemical stressors in the environment. This study is the first to apply species sensitivity distribution (SSD) combined with mixture models (concentration addition (CA) and independent action (IA)) to derive an integrated proxy of the ecological impact of combined radiological and chemical stressors: msPAF (multisubstance potentially affected fraction of species). The approach was tested on the routine liquid effluents from nuclear power plants that contain both radioactive and stable chemicals. The SSD of ionising radiation was significantly flatter than the SSD of 8 stable chemicals (namely Cr, Cu, Ni, Pb, Zn, B, chlorides and sulphates). This difference in shape had strong implications for the selection of the appropriate mixture model: contrarily to the general expectations the IA model gave more conservative (higher msPAF) results than the CA model. The msPAF approach was further used to rank the relative potential impact of radiological versus chemical stressors.

This manuscript evaluates spatial and temporal variations of source contributions to ambient fine particulate matter (PM2.5) in Israeli, Jordanian, and Palestinian cities. Twenty-four hour integrated PM2.5 samples were collected every six days over a 1-year period (January to December 2007) in four cities in Israel (West Jerusalem, Eilat, Tel Aviv, and Haifa), four cities in Jordan (Amman, Aqaba, Rahma, and Zarka), and three cities in Palestine (Nablus, East Jerusalem, and Hebron). The PM2.5 samples were analyzed for major chemical components, including organic carbon and elemental carbon, ions, and metals, and the results were used in a positive matrix factorization (PMF) model to estimate source contributions to PM2.5 mass. Nine sources, including secondary sulfate, secondary nitrate, mobile, industrial lead sources, dust, construction dust, biomass burning, fuel oil combustion and sea salt, were identified across the sampling sites. Secondary sulfate was the dominant source, contributing 35% of the total PM2.5 mass, and it showed relatively homogeneous temporal trends of daily source contribution in the study area. Mobile sources were found to be the second greatest contributor to PM2.5 mass in the large metropolitan cities, such as Tel Aviv, Hebron, and West and East Jerusalem. Other sources (i.e. industrial lead sources, construction dust, and fuel oil combustion) were closely related to local emissions within individual cities. This study demonstrates how international cooperation can facilitate air pollution studies that address regional air pollution issues and the incremental differences across cities in a common airshed. It also provides a model to study air pollution in regions with limited air quality monitoring capacity that have persistent and emerging air quality problems, such as Africa, South Asia and Central America.

Atmospheric acid deposition is a global environmental issue. China has been experiencing serious acid deposition, which is anticipated to become more severe with the country's economic development and increasing consumption of fossil fuels in recent decades. We explored the spatiotemporal variations of acid deposition (wet acid deposition) and its influencing factors by collecting nationwide data on pH and concentrations of sulfate (SO4²⁻) and nitrate (NO3⁻) in precipitation between 1980 and 2014 in China. Our results showed that average precipitation pH values were 4.59 and 4.70 in the 1990s and 2010s, respectively, suggesting that precipitation acid deposition in China has not seriously worsened. Average SO4²⁻ deposition declined from 40.54 to 34.87 kg S ha⁻¹ yr⁻¹ but average NO3⁻ deposition increased from 4.44 to 7.73 kg N ha⁻¹ yr⁻¹. Specifically, the area of severe precipitation acid deposition in southern China has shrunk to some extent as a result of controlling the pollutant emissions; but the area of moderate precipitation acid deposition has expanded in northern China, associated with rapid industrial and transportation development. Furthermore, we found significant positive correlations between precipitation acid deposition, energy consumption, and rainfall. Our findings provide a relatively comprehensive evaluation of the spatiotemporal dynamics of precipitation acid deposition in China over past three decades, and confirm the idea that strategies implemented to save energy and control pollutant emissions in China have been effective in alleviating precipitation acid deposition. These findings might be used to demonstrate how developing countries could achieve economic development and environmental protection through the implementation of advanced technologies to reduce pollutant emissions.

An Aerodyne quadrupole aerosol mass spectrometry (Q-AMS) was utilized to measure the size-resolved chemical composition of non-refractory submicron particles (NR-PM1) from October 27 to December 3, 2014 at an urban site in Lanzhou, northwest China. The average NR-PM1 mass concentration was 37.3 μg m−3 (ranging from 2.9 to 128.2 μg m−3) under an AMS collection efficiency of unity and was composed of organics (48.4%), sulfate (17.8%), nitrate (14.6%), ammonium (13.7%), and chloride (5.7%). Positive matrix factorization (PMF) with the multi-linear engine (ME-2) solver identified six organic aerosol (OA) factors, including hydrocarbon-like OA (HOA), coal combustion OA (CCOA), cooking-related OA (COA), biomass burning OA (BBOA) and two oxygenated OA (OOA1 and OOA2), which accounted for 8.5%, 20.2%, 18.6%, 12.4%, 17.8% and 22.5% of the total organics mass on average, respectively. Primary emissions were the major sources of fine particulate matter (PM) and played an important role in causing high chemically resolved PM pollution during wintertime in Lanzhou. Back trajectory analysis indicated that the long-range regional transport air mass from the westerly was the key factor that led to severe submicron aerosol pollution during wintertime in Lanzhou.

In the study, the capability of Paecilomyces lilacinus XLA (CCTCC: M2012135) to reduce Cr6+ and its main antagonistic mechanisms to Cr6+ were experimentally evaluated. Activated growing fungus XLA efficiently reduced over 90% Cr6+ in the media with Cr6+ concentration below 100 mg L−1 at pH 6 after 14 days. After 1-day exposure to 100 mg L−1 Cr6+, nearly 50% of Cr6+ was reduced. Moreover, SO42− stimulated Cr6+ reduction, whereas other interferential ions inhibited Cr6+ reduction. The interaction mechanisms between XLA and Cr6+ mainly involve biotransformation, biosorption, and bioaccumulation, as detected by electron microscopy and chemical methods. The lower concentrations of Cr6+ (5 and 50 mg L−1) stimulated the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione (GSH) level in XLA, respectively, but the higher concentration of Cr6+ (150 mg L−1) decreased the enzymatic activities and GSH concentration. The results implied that SOD, CAT and GSH were defensive guards to the oxidant stress produced by Cr6+. All these extracellular/intracellular defense systems endowed XLA with the ability to resist and detoxify Cr6+ by transforming its valent species. The fungus XLA could efficiently reduce Cr6+ under different environmental conditions (pH, interferential ions, and concentration). Moreover, XLA could endure the high concentration of Cr6+ probably due to its high biotransformation capability of Cr6+ and intracellular antioxidant systems for the detoxification of ROS generated by external Cr6+. All these results suggested that the fungus XLA can be applied to remediation of Cr6+-contaminated environments.

Pharmaceutical and personal care products (PPCPs) are continuously introduced into the soil-plant system, through practices such as agronomic use of reclaimed water and biosolids containing these trace contaminants. Plants may accumulate PPCPs from soil, serving as a conduit for human exposure. Metabolism likely controls the final accumulation of PPCPs in plants, but is in general poorly understood for emerging contaminants. In this study, we used diclofenac as a model compound, and employed 14C tracing, and time-of-flight (TOF) and triple quadruple (QqQ) mass spectrometers to unravel its metabolism pathways in Arabidopsis thaliana cells. We further validated the primary metabolites in Arabidopsis seedlings. Diclofenac was quickly taken up into A. thaliana cells. Phase I metabolism involved hydroxylation and successive oxidation and cyclization reactions. However, Phase I metabolites did not accumulate appreciably; they were instead rapidly conjugated with sulfate, glucose, and glutamic acid through Phase II metabolism. In particular, diclofenac parent was directly conjugated with glutamic acid, with acyl-glutamatyl-diclofenac accounting for >70% of the extractable metabolites after 120-h incubation. In addition, at the end of incubation, >40% of the spiked diclofenac was in the non-extractable form, suggesting extensive sequestration into cell matter. The rapid formation of non-extractable residue and dominance of diclofenac-glutamate conjugate uncover previously unknown metabolism pathways for diclofenac. In particular, the rapid conjugation of parent highlights the need to consider conjugates of emerging contaminants in higher plants, and their biological activity and human health implications.

Reservoirs typically have elevated fish mercury (Hg) levels compared to natural lakes and rivers. A unique feature of reservoirs is water-level management which can result in sediment exposure to the air. The objective of this study is to identify how reservoir water-level fluctuations impact Hg cycling, particularly the formation of the more toxic and bioaccumulative methylmercury (MeHg). Total-Hg (THg), MeHg, stable isotope methylation rates and several ancillary parameters were measured in reservoir sediments (including some in porewater and overlying water) that are seasonally and permanently inundated. The results showed that sediment and porewater MeHg concentrations were over 3-times higher in areas experiencing water-level fluctuations compared to permanently inundated sediments. Analysis of the data suggest that the enhanced breakdown of organic matter in sediments experiencing water-level fluctuations has a two-fold effect on stimulating Hg methylation: 1) it increases the partitioning of inorganic Hg from the solid phase into the porewater phase (lower log Kd values) where it is more bioavailable for methylation; and 2) it increases dissolved organic carbon (DOC) in the porewater which can stimulate the microbial community that can methylate Hg. Sulfate concentrations and cycling were enhanced in the seasonally inundated sediments and may have also contributed to increased MeHg production. Overall, our results suggest that reservoir management actions can have an impact on the sediment-porewater characteristics that affect MeHg production. Such findings are also relevant to natural water systems that experience wetting and drying cycles, such as floodplains and ombrotrophic wetlands.

The Catskill Mountains have been adversely impacted by decades of acid deposition, however, since the early 1990s, levels have decreased sharply as a result of decreases in emissions of sulfur dioxide and nitrogen oxides. This study examines trends in acid deposition, stream-water chemistry, and soil chemistry in the southeastern Catskill Mountains. We measured significant reductions in acid deposition and improvement in stream-water quality in 5 streams included in this study from 1992 to 2014. The largest, most significant trends were for sulfate (SO42−) concentrations (mean trend of −2.5 μeq L−1 yr−1); hydrogen ion (H+) and inorganic monomeric aluminum (Alim) also decreased significantly (mean trends of −0.3 μeq L−1 yr−1 for H+ and −0.1 μeq L−1 yr−1 for Alim for the 3 most acidic sites). Acid neutralizing capacity (ANC) increased by a mean of 0.65 μeq L−1 yr−1 for all 5 sites, which was 4 fold less than the decrease in SO42− concentrations. These upward trends in ANC were limited by coincident decreases in base cations (−1.3 μeq L−1 yr−1 for calcium + magnesium). No significant trends were detected in stream-water nitrate (NO3−) concentrations despite significant decreasing trends in NO3− wet deposition. We measured no recovery in soil chemistry which we attributed to an initially low soil buffering capacity that has been further depleted by decades of acid deposition. Tightly coupled decreasing trends in stream-water silicon (Si) (−0.2 μeq L−1 yr−1) and base cations suggest a decrease in the soil mineral weathering rate. We hypothesize that a decrease in the ionic strength of soil water and shallow groundwater may be the principal driver of this apparent decrease in the weathering rate. A decreasing weathering rate would help to explain the slow recovery of stream pH and ANC as well as that of soil base cations.

An on-line source-tagged model coupled with an air quality model (Nested Air Quality Prediction Model System, NAQPMS) was applied to estimate source contributions of primary and secondary sulfate, nitrate and ammonium (SNA) during a representative winter period in Shanghai. This source-tagged model system could simultaneously track spatial and temporal sources of SNA, which were apportioned to their respective primary precursors in a simulation run. The results indicate that in the study period, local emissions in Shanghai accounted for over 20% of SNA contributions and that Jiangsu and Shandong were the two major non-local sources. In particular, non-local emissions had higher contributions during recorded pollution periods. This suggests that the transportation of pollutants plays a key role in air pollution in Shanghai. The temporal contributions show that the emissions from the “current day” (emission contribution from the current day during which the model was simulating) contributed 60%–70% of the sulfate and ammonium concentrations but only 10%–20% of the nitrate concentration, while the previous days’ contributions increased during the recorded pollution periods. Emissions that were released within three days contributed over 85% averagely for SNA in January 2013. To evaluate the source-tagged model system, the results were compared by sensitivity analysis (emission perturbation of −30%) and backward trajectory analysis. The consistency of the comparison results indicated that the source-tagged model system can track sources of SNA with reasonable accuracy.