This research apportioned size-resolved particulate matter (PM) contributions in a megacity in northern China based on a full year of measurements of both inorganic and organic markers. Ions, elements, carbon fractions, n-alkanes, polycyclic aromatic hydrocarbons (PAHs), hopanes and steranes in 9 p.m. size fractions were analyzed. High molecular weight PAHs concentrated in fine PM, while most other organic compounds showed two peaks. Both two-way and three-way receptor models were used for source apportionment of PM in different size ranges. The three-way receptor model gave a clearer separation of factors than the two-way model, because it uses a combination of chemical composition and size distributions, so that factors with similar composition but distinct size distributions (like more mature and less mature coal combustion) can be resolved. The three-way model resolved six primary and three secondary factors. Gasoline vehicles and coal and biomass combustion, nitrate and high relative humidity related secondary aerosol, and resuspended dust and diesel vehicles (exhaust and non-exhaust) are the top two contributors to pseudo-ultrafine (<0.43 μm), fine (0.43–2.1 μm) and coarse mode (>2.1 μm) PM, respectively. Mass concentration of PM from coal and biomass combustion, industrial emissions, and diesel vehicle sources showed a bimodal size distribution, but gasoline vehicles and resuspended dust exhibited a peak in the fine and coarse mode, separately. Mass concentration of sulphate, nitrate and secondary organic aerosol exhibited a bimodal distribution and were correlated with temperature, indicating strong photochemical processing and repartitioning. High relative humidity related secondary aerosol was strongly associated with size shifts of PM, NO₃⁻ and SO₄²⁻ from the usual 0.43–0.65 μm to 1.1–2.1 μm. Our results demonstrated the dominance of primary combustion sources in the <0.43 μm particle mass, in contrast to that of secondary aerosol in fine particle mass, and dust in coarse particle mass in the Northern China megacity.

Little is known about the fate of oil spills in rivers. Hyporheic flows of water through river sediments exchange surface and groundwater and create upwelling and downwelling zones that are important for fish spawning and embryo development. Risk assessments of oil spills to rivers do not consider the potential for hyporheic flows to carry oil droplets into sediments and the potential for prolonged exposure of fish to trapped oil. This project assessed whether oil droplets in water flowing through gravel will be trapped and whether hydrocarbons partitioning from trapped oil droplets are bioavailable to fish. Columns packed with gravel were injected with oil-in-water dispersions prepared with light crude, medium crude, diluted bitumens, and heavy fuel oil to generate a series of oil droplet loadings. The concentrations of oil trapped in the gravel increased with oil loading and viscosity. When the columns were perfused with clean water, oil concentrations in column effluents decreased to the detection limit within the first week of water flow, with sporadically higher concentrations associated with oil droplet release. Despite the low concentrations of hydrocarbons measured in column effluent, hydrocarbons were bioavailable to juvenile rainbow trout (Oncorhynchus mykiss) for more than three weeks of water flow, as indicated by strong induction of liver ethoxyresorufin-o-deethylase activity. These findings indicate that ecological risk assessments and spill response should identify and protect areas in rivers sensitive to contaminant trapping.

Thermal desorption is widely adopted for the remediation of organic compounds, yet is generally considered a non-green-sustainable manner owing to its energy-intensive nature and potential to deteriorate soil reuse. Here, lube oil-contaminated soils were remediated at 200–500 °C in nitrogen atmosphere, upon which removal behaviors of lube oil and physicochemical properties of soils were explored. Illumina 16S ribosomal RNA (rRNA) and 18S rRNA amplicon sequencing were employed to determine the relative abundances and diversities of bacteria and fungi in soils, respectively. The results indicated that, after heating at 350 °C for 60 min, 93% of the lube oil was reduced, with the residual lube oil concentration lower than the Chinese risk intervention values (GB 36600–2018). The weakly-alkaline, multi-phosphorus and char-rich soils after indirect thermal desorption could provide a nutrient source and favorable habitat space for living organisms, and the decomposition of minerals in soils is more conducive to the survival of organisms. Microbial species in soils after heating at 350 °C became extinct, however, microbial species after 3 days of recolonization were enough to carry out DNA extraction when these soils were exposed to natural grass land. Though the microbial richness and diversity in heated soils after 3 days of recolonization were still little lower than those in contaminated soils, Firmicutes (29.41%) and Basidiomycota (9.33%) became dominant at phyla level, while Planomicrobium (16.37%), Massilia (10.09%), Jeotgalibaca (7.91%) and Psychrobacter (6.84%) were dominant at general level, whose ecological function was more conducive to nutrient cycling and ecological resiliency. Overall, this innovative research provides a new perspective: low temperature indirect thermal desorption may also achieve a sustainable remediation, due to its energy-saving (low temperature), favorable physicochemical properties and the rapid recolonization capacity of microbial communities in heated soils.

Stringent mitigation measures have reduced wintertime fine particulate matter (PM₂.₅) concentrations by 42.2% from 2013 to 2018 in the Beijing-Tianjin-Hebei (BTH) region, but severe PM pollution still frequently engulfs the region. The observed nitrate aerosols have not exhibited a significant decreasing trend and constituted a major fraction (about 20%) of the total PM₂.₅, although the surface-measured NO₂ concentration has decreased by over 20%. The contributions of nitrogen oxides (NOX) emissions mitigation to the nitrate and PM₂.₅ concentrations and how to alleviate nitrate aerosols efficiently under the current situation still remains elusive. The WRF-Chem model simulations of a persistent and heavy PM pollution episode in January 2019 in the BTH reveal that NOX emissions mitigation does not help lower wintertime nitrate and PM₂.₅ concentrations under current conditions in the BTH. A 50% reduction in NOX emissions only decreases nitrate mass by 10.3% but increases PM₂.₅ concentrations by 3.2%, because the substantial O₃ increase induced by NOX mitigation offsets the HNO₃ loss and enhances sulfate and secondary organic aerosols formation. Our results are further consolidated by the occurrence of severe PM pollution in the BTH during the COVID-19 outbreak, with a significant reduction in NO₂ concentration. Mitigation of NH₃ emissions constitutes the priority measure to effectively lower the nitrate and PM₂.₅ concentrations in the BTH under current conditions, with 35.5% and 12.7% decrease, respectively, when NH₃ emissions are reduced by 50%.

In this study, we examined the change rates of PM₂.₅ concentrations, aerosol optical depth (AOD), and the concentrations of PM₂.₅ precursors, such as SO₂ and NO₂, in China and South Korea using surface and satellite observations from 2015 to 2018. To quantify the impacts of the emissions and meteorology on the concentration changes, we performed a series of air quality simulations with year-specific meteorology and a fixed anthropogenic emissions inventory. The surface PM₂.₅ observations in China and South Korea decreased at rates of 9.1 and 4.3%/yr during the study period, respectively. The AODs from Moderate Resolution Imaging Spectroradiometer (MODIS) and Geostationary Ocean Color Imager (GOCI) also decreased faster over China than the AODs over South Korea. For the PM₂.₅ decrease in China, the emission impact was more significant (73%) than the meteorology impact (27%). On the contrary, in South Korea, the emissions and meteorology impacts on PM₂.₅ reductions were similar (51% vs 49%). The SO₂ concentration over China in 2018 significantly reduced to approximately half of the level in 2015. In turn, the sulfate concentration in Baengnyeong (BN), located in a downwind pathway from China to South Korea, decreased at a rate of 0.79%/month. However, the nitrate concentration in BN showed an increasing trend due to the non-linear chemical reactions among sulfate-nitrate-ammonium. The increased nitrate compensated for the reduced PM₂.₅ concentration from the sulfate decrease at BN. Additionally, the number of high (>50 μg/m³) PM₂.₅ concentration days continuously decreased in China, but the number in South Korea increased. It is noted that emission reductions in an upwind area do not guarantee corresponding air quality improvement in the downwind area when complex secondary aerosol formation processes, as well as spatiotemporal changes in meteorology, are involved in the transboundary transport of air pollutants.

Polycyclic aromatic hydrocarbons (PAHs) are pollutants of global concern in coastal environments. They have a wide range of biological toxicity and due to their inherent properties, can easily bioaccumulate in organisms and concentrate in the environment. This work evaluated, in an integrated way, the seasonal PAH distribution patterns in sediments and four bioindicators fish species in a highly impacted estuary of Argentina; besides, their bioaccumulation patterns were assessed for the first time as indicator of ecological risk. The highest PAH levels in fish were found for Ramnogaster arcuata with an average of 64 ng g⁻¹ w.w., followed by Micropogonias furnieri (45 ng g⁻¹ w.w.), Cynoscion guatucupa (28 ng g⁻¹ w.w.), and Mustelus schmitti (16 ng g⁻¹ w.w.). Fish presented the highest PAH levels in fall with a predominance of petrogenic PAHs in colder seasons and pyrolytic PAHs in warmer seasons. Sediments presented an average of 233 ng g⁻¹ d.w. with the same seasonal composition pattern of the fish tissues. Additionally, the data suggested that the main source of PAHs are wastewater discharges. The bioaccumulation factor (BAF) of PAHs in the tested fishes were found to range from 0.3 to 8. The highest values were observed during fall and winter, while bioaccumulation did not occur in moist spring and summer samples, which would suggest a high biotransformation process during these seasons. Results suggested that class III of juvenile C. guatucupa and M. furnieri, and adults R. arcuata are more sensitive bioindicators of chronic PAH contamination and that their bioaccumulation is independent of the compound hydrophobicity; this could have a positively influence on the criteria used for biological monitoring programs along the Atlantic coast. In addition, the presented BAF data on the target species will serve as a useful pollution indicator for South Atlantic coastal fish.

POCIS is the most widely applied passive sampler of polar organic substances, because it was one of the first commercially available samplers for that purpose on the market, but also for its applicability for a wide range of substances and conditions. Its main weakness is the variability of sampling performance with exposure conditions. In our study we took a pragmatic approach and performed in situ calibration for a set of 76 pharmaceuticals and their metabolites in five sampling campaigns in surface water, covering various temperature and flow conditions. In individual campaigns, RS were calculated for up to 47 compounds ranging from 0.01 to 0.63 L d⁻¹, with the overall median value of 0.10 L d⁻¹. No clear changes of RS with water temperature or discharge could be found for any of the investigated substances. The absence of correlation of experimental RS with physical-chemical properties in combination with the lack of mechanistic understanding of compound uptake to POCIS implies that practical estimation of aqueous concentrations from uptake in POCIS depends on compound-specific experimental calibration data. Performance of POCIS was compared with grab sampling of water in seven field campaigns comprising multiple sampling sites, where sampling by both methods was done in parallel. The comparison showed that for 25 of 36 tested compounds more than 50% of POCIS-derived aqueous concentrations did not differ from median of grab sampling values more than by a factor of 2. Further, for 30 of 36 compounds, more than 80% of POCIS data did not differ from grab sampling data more than by a factor of 5. When accepting this level of accuracy, in situ derived sampling rates are sufficiently robust for application of POCIS for identification of spatial and temporal contamination trends in surface waters.

The deposition of light absorbing impurities (LAIs) (e.g., black carbon (BC), organic carbon (OC), mineral dust (MD)) on snow is an important attribution to accelerate snowmelt across the northern Xinjiang, China. At present, there is still a lack of understanding of the LAIs concentration, elution and enrichment process in snow cover over Xinjiang. Based on these, continuously sampling during two years carried out to investigate the concentrations, impacts and potential sources of LAIs in snow at Kuwei Station in the southern Altai Mountains. The average concentrations of BC, OC and MD in the surface snow were 2787 ± 2334 ng g⁻¹, 6130 ± 6127 ng g⁻¹, and 70.03 ± 62.59 μg g⁻¹, respectively, which dramatically increased along with snowmelt intensified, reflecting a significant enrichment process of LAIs at the snow surface. Besides, high LAIs concentrations also found in the subsurface and melting layers of the snowpit, reflecting the elution and redistribution of LAIs. With the simulation of the SNow ICe Aerosol Radiative model, BC was the main dominant factor in reducing snow albedo and radiative forcing (RF), its impact was more remarkable in the snowmelt period. The average contribution rates of BC, MD and BC + MD to snow albedo reduction increased by 20.0 ± 1.9%, 13.0 ± 0.2%, and 20.5 ± 2.3% in spring compared with that in winter; meanwhile, the corresponding average RFs increased by 15.8 ± 3.4 W m⁻², 4.7 ± 0.3 W m⁻² and 16.4 ± 3.2 W m⁻², respectively. Changes in the number of snowmelt days caused by BC and MD decreased by 3.0 ± 0.4 d to 8.3 ± 1.3 d. It indicated that surface enrichment of LAIs during snow melting might accelerate snowmelt further. Weather Research and Forecasting Chemistry model showed that the resident emission was the main potential source of BC and OC in snow. This implied that the mitigation of intensive snowmelt needs to mainly reduce resident emission of LAIs in the future.

Metal release into the environment from anthropogenic activities may endanger ecosystems and human health. However, identifying and quantifying anthropogenic metal bioaccumulation in organisms remain a challenging task. In this work, we assess Cu isotopes in Pacific oysters (C. gigas) as a new tool for monitoring anthropogenic Cu bioaccumulation into marine environments. Arcachon Bay was taken as a natural laboratory due to its increasing contamination by Cu, and its relevance as a prominent shellfish production area. Here, we transplanted 18-month old oysters reared in an oceanic neighbor area into two Arcachon Bay mariculture sites under different exposure levels to continental Cu inputs. At the end of their 12-month long transplantation period, the oysters’ Cu body burdens had increased, and was shifted toward more positive δ⁶⁵Cu values. The gradient of Cu isotope compositions observed for oysters sampling stations was consistent with relative geographic distance and exposure intensities to unknown continental Cu sources. A binary isotope mixing model based on experimental data allowed to estimate the Cu continental fraction bioaccumulated in the transplanted oysters. The positive δ⁶⁵Cu values and high bioaccumulated levels of Cu in transplanted oysters support that continental emissions are dominantly anthropogenic. However, identifying specific pollutant coastal source remained unelucidated mostly due to their broader and overlapping isotope signatures and potential post-depositional Cu isotope fractionation processes. Further investigations on isotope fractionation of Cu-based compounds in an aqueous medium may improve Cu source discrimination. Thus, using Cu as an example, this work combines for the first time a well-known caged bivalve approach with metal stable isotope techniques for monitoring and quantifying the bioaccumulation of anthropogenic metal into marine environments. Also, it states the main challenges to pinpoint specific coastal anthropogenic sources utilizing this approach and provides the perspectives for further studies to overcome them.

A highly efficient, eco-friendly and relatively low-cost catalyst is necessary to tackle bottlenecks in the treatment of industrial wastewater laden with heavy metals and antibiotic such as livestock farm and biogas liquids. This study investigated co-oxidative removal of arsenite (As(III)) and tetracycline (TC) by iron nanoparticles (Fe NP)-impregnated carbons based on heterogeneous Fenton-like reactions. The composites included Fe NP@biochar (BC), Fe NP@hydrochar (HC), and Fe NP@HC-derived pyrolysis char (HDPC). The functions of N and S atoms and the loading mass of the Fe NP in the Fe NP@BC in heterogeneous Fenton-like reactions were studied. To sustain its cost-effectiveness, the spent Fe NP@BC was regenerated using NaOH. Among the composites, the Fe NP@BC achieved an almost complete removal of As(III) and TC under optimized conditions (1.0 g/L of dose; 10 mM H₂O₂; pH 6; 4 h of reaction; As(III): 50 μM; TC: 50 μM). The co-oxidative removal of As(III) and TC by the Fe NP@ BC was controlled by the synergistic interactions between the Fe NPs and the active N and S sites of the BC for generating reactive oxygen species (ROS). After four consecutive regeneration cycles, about 61 and 95% of As(III) and TC removal were attained. This implies that the spent carbocatalyst still has reasonable catalytic activities for reuse. Overall, this suggests that adding technological values to unused biochar as a carbocatalyst like Fe NP@BC was promising for co-oxidative removal of As(III) and TC from contaminated water.