Environmental Science: Processes & Impacts最新文献

The Yangtze River ranks second globally in salt flux and plays a pivotal role in material transport to the oceans. As a key constituent of salt flux, sulfate (SO₄^2-) requires clear source apportionment and process characterization. This study integrates hydrochemistry, stable isotopes, and a Bayesian isotope mixing model (MixSIAR) to resolve the spatial distribution, sources, transformation pathways, and drivers of SO₄^2- across the basin. Observed SO₄^2- concentrations range from 8.44 to 277.59 mg L^-1, with region-averaged means of upstream (80.83 mg L^-1) > downstream (41.00 mg L^-1) > midstream (30.59 mg L^-1). Basin hydrochemistry reflects the combined control of rock weathering and anthropogenic activities. Isotopic signatures identify five potential SO₄^2- sources: atmospheric deposition, evaporite dissolution, sulfide oxidation, fertilizers, and sewage. MixSIAR estimates indicate that sulfide oxidation was the dominant SO₄^2- source in the dry-season samples, with the highest contribution in the upstream region (90.1 ± 4.9%). Toward the midstream and downstream, the relative contribution of sewage increased, indicating a dry-season longitudinal shift from predominantly natural processes toward stronger anthropogenic inputs. These results provide dry-season constraints on SO₄^2- sources and transformation processes in the Yangtze River and improve understanding of sulfur migration in large river systems.

Correction for 'Hydrophobic model systems for oil film photooxidation: part II: direct and indirect pathways controlled by oxygen and molecular structure' by Bin Wu et al., Environ. Sci.: Processes Impacts, 2026, https://doi.org/10.1039/d6em00173d.

Aerosol constituents transform as they travel through the air handling unit (AHU) due to the air being filtered, heated, and cooled. Though the strength of these processes has direct indoor air quality implications, comprehensive model descriptions of how commercial heating, ventilating, and air conditioning (HVAC) systems affect indoor aerosol composition are lacking. Herein, an AHU module was designed to augment the Indoor Model of Aerosols, Gases, Emissions, and Surfaces (IMAGES) framework, which is a modeling platform that simulates indoor aerosols by incorporating the two-dimensional volatility basis set (2D-VBS) for organic aerosol and ISORROPIA for inorganic aerosol. This AHU module simulates the organic and inorganic concentrations as air travels from the mixing box, through the filter, through the heating and cooling coils, and into the supply duct. It accounts for essential processes inside the AHU, such as particle deposition to the filter and heat exchangers, gas loss to the water condensed on the cooling coil during operation, and temperature-driven repartitioning of organic and inorganic species by using thermodynamic frameworks in the 2D-VBS and ISORROPIA. The module's performance was assessed with measurements taken at various stages of an HVAC system at Johns Hopkins University when periodic cooling occurred. Modeled concentrations post filter and heating coil were slightly over-predicted, which caused over-predictions in the supply duct. However, the module performed well when the processes of aerosols flowing over the cooling coil were isolated. Still, consistent with our previous work that applied ISORROPIA to an indoor setting, a missing condensation sink within ISORROPIA must be accounted for to obtain more accurate inorganic partitioning. Thus, HVAC system impacts on aerosol composition may now be better considered in detailed indoor aerosol models, such as IMAGES.

The aging of pollutants determines their bioavailability and the corresponding toxicity thresholds in soil environments. However, existing ecotoxicological assessments of heavy metals, antibiotics, and pesticides in facility agricultural soils rarely incorporate the confounding influences of contaminant aging and soil physicochemical properties. This study selected six facility agricultural soils with differing properties and assessed their toxic effects on Chinese cabbage (Brassica rapa subsp. chinensis) biomass following exogenous addition of cadmium (Cd), tetracycline (TC), and imidacloprid (IM), administered both individually and in combination. Under single Cd contamination, the EC₅₀ for biomass inhibition increased from the 14-day value to 30.0 mg kg^-1 after 360 days of aging. For combined contamination, the EC₅₀ reached 18.3 mg kg^-1 for Cd-TC and 24.5 mg kg^-1 for Cd-IM over the same aging period. In the acidic soils, a low-dose tetracycline inducing hormetic response was observed, with biomass stimulation exceeding 110% of the control. As aging progressed from 14 to 360 days, pollutant toxicity declined. During early aging, no significant difference in aging factors was observed between composite and single pollutants. However, in the later stages, the aging factors for composite pollutants were significantly higher than those of single pollutants. Among these, the Cd-TC aging factor was lowest in Guangxi red soil (AF_360d = 3.21), and highest in Henan alluvial soil (AF_360d = 3.82). Furthermore, the aging factor increment was more pronounced for Cd-TC mixtures than for Cd-IM. In different types of facility agricultural soils, soil organic matter and clay content can effectively predict the soil aging process as the aging period increases. All predictive models for aging factors were derived, for single Cd contamination as: (AF_180d) = -0.256 + 0.455 lg pH + 0.511 lg CEC + 0.593 lg OM (R² = 0.884, p < 0.01). These findings provide data and theoretical support for the development of aging factor prediction models and the establishment of environmental quality standards for combined contamination involving heavy metals and emerging pollutants in facility agricultural soils.

Correction for 'Artificial turf fields act as recurring point sources of metals and emerging tire-derived contaminants in stormwater' by Kate J. Moloney et al., Environ. Sci.: Processes Impacts, 2026, 28, 935-948, https://doi.org/10.1039/D5EM01016K.

Legacy phosphorus (P) accumulated in agricultural soils can be remobilized under changing environmental conditions, increasing the risk of diffuse nutrient losses and eutrophication. However, how multiple environmental disturbances jointly regulate P mobilization across contrasting mineralogical soil systems remains insufficiently understood. Here, four representative soils from the Xiangxi River watershed (Three Gorges Reservoir region, China) were subjected to controlled flooding, simulated acidification, and organic ligand treatments. Mineralogical characterization was integrated with dissolved reactive P release, operational P fractionation, adsorption-desorption experiments, and apparent thermodynamic analyses to identify the mineralogical controls on phosphorus mobilization. Phosphorus mobilization differed consistently among soils with contrasting mineralogical characteristics. Flooding, decreasing pH, and organic ligand inputs all enhanced dissolved reactive P release, although the magnitude and dominant pathways varied with soil mineral composition. Fe/Al-rich soils exhibited greater susceptibility to flooding- and ligand-induced desorption, whereas Ca-rich calcareous soils responded more strongly to acidification through redistribution of Ca-associated phosphorus pools. Low-molecular-weight organic acids promoted substantially greater phosphorus mobilization than humic substances, highlighting the importance of ligand chemistry in regulating phosphorus availability. Apparent thermodynamic analyses further indicated that phosphorus sorption in these heterogeneous soils behaved as an overall endothermic process and that the derived thermodynamic parameters are most appropriately interpreted as comparative descriptors of adsorption affinity. Overall, the results demonstrate that soil mineralogy governs phosphorus mobilization by mediating the response of mineral-phosphate interactions to coupled environmental disturbances. Overall, the findings provide an evidence-based framework for understanding mineralogy-dependent phosphorus mobilization under multiple environmental disturbances and support mineralogy-informed assessment and management of phosphorus loss risk in reservoir-influenced agroecosystems.

Palsas and lithalsas are permafrost landforms that are ubiquitous parts of the subarctic landscape, commonly found in areas of discontinuous permafrost. Their degradation can lead to the formation of thermokarst lakes, releasing contaminants previously stored in permafrost, such as mercury (Hg). In this study, two thermokarst lakes (KANG1 and KANG2) were sampled in the winter and summer of 2023 in the Canadian subarctic (Kangiqsualujjuaq, Nunavik). The thermokarst lakes differ in origin, with KANG1 formed through lithalsa degradation and KANG2 through palsa degradation. Water column analyses included total Hg (THg) and monomethylmercury (MMHg). Bottom lake sediments were also analyzed, and incubation assays conducted to evaluate methylation and demethylation potential, as well as the contributions of key microbial methylators. Winter conditions appeared to favor Hg methylation and accumulation in the water column. In KANG1, the fraction of Hg that is present in the form of MMHg (%MMHg) ranged from 56.8 ± 2.9% to 100% (measured as 102.7 ± 1.8%) in winter, with lower summer values averaged 19.8 ± 1.0%, suggesting potential transport to adjacent freshwater systems during spring thaw. Sediment THg concentrations were similar across seasons, but the %MMHg and methylation rates were higher in winter exhibiting the same pattern observed in the water column. Conversely, KANG2 exhibited higher THg, %MMHg and methylation rates, reaching 0.42 ± 0.02 day^-1 during summer. Incubation results highlighted the important role of sulfate-reducing bacteria (SRB) and methanogens in MMHg production in these systems and revealed distinct seasonal patterns in methylation and demethylation rates that may be linked to shifts in microbial guilds responsible for these processes.

This study evaluates sediments from the mangrove estuary to examine the premise that geogenic and fluvial dynamics act as the dominant controls on elemental (primordial radionuclides and REEs) partitioning, with secondary regulation by the trivial influence of anthropogenic activities. A total of 31 benthic sediments were collected across the upstream to downstream transect and analysed using ICP-MS. Activity concentrations (Bq kg^-1) of ⁴⁰K, ²²⁶Ra, and ²³²Th were calculated based on elemental abundance of Th, U, and K, respectively, and multivariate statistical approaches were applied to identify elemental sources with a quantitative approach. The average activities (in Bq kg^-1) of ⁴⁰K (819 ± 86), ²²⁶Ra (46.6 ± 7.6), and ²³²Th (78.7 ± 12.4) exceeded global baselines, while total REEs ranged from 188 to 390 µg g^-1, strongly enriched in light-REEs (∑LREE/∑HREE = 8.4 ± 0.2) with a notable europium anomaly (Eu/Eu* = 0.56 ± 0.03). High field strength elements (Hf: 5.5 ± 1.9; Zr: 224 ± 80; Ta: 1.3 ± 0.2 µg g^-1) and actinides (Th: 19.4 ± 3.1; U: 3.8 ± 0.6 µg g^-1) exhibited localized enrichment in mid-estuarine zones, reflecting hydrodynamic sorting of heavy minerals. Geo-environmental indices revealed "unpolluted to moderately polluted" conditions, consistent with a primarily geogenic signal. The mean absorbed dose rate was 103 ± 8.6 nGy h^-1, which was slightly higher than the global average value but at or below internationally accepted safe limits for all other radiological hazard indices. The potential ecological risks were generally mild to moderate (PERI:100-212), with one site exhibiting the highest localized risk (RI = 212) due to elevated REEs (Lu, Tm, and Tb), indicating potential ecological toxicity. Thus, the findings suggest a felsic provenance with minimal anthropogenic influence primarily shapes the geochemistry of the mangrove sediments. While current risks are within acceptable limits, localized anomalies suggest potential ecological vulnerability and magnify the importance of mangrove estuaries as dynamic reservoirs of primordial radionuclides and REEs in the context of global warming-driven sediment redistribution and sea-level variations.

Calcium (Ca) isotopes are increasingly recognized as sensitive tracers of chemical weathering and carbonate formation, yet the controls on riverine δ^44/40Ca remain poorly constrained in large mountainous catchments. Here, we investigated dissolved Ca sources and isotopic behavior in the upper Yangtze River by comparing high-altitude and low-altitude sub-basins during the low-flow season. The δ^44/40Ca values ranged from 0.74‰ to 0.98‰ in high-altitude regions (mean = 0.86‰) and from 0.77‰ to 0.87‰ in low-altitude regions (mean = 0.83‰), both within the global riverine range and showing only a small, statistically insignificant difference between altitude groups. Inversion modeling showed that carbonate weathering dominated dissolved Ca in low-altitude regions (20-89%, mean 60%), whereas high-altitude waters displayed more variable source contributions, with carbonate weathering contributing 15-80%, evaporite dissolution 6-53%, and silicate weathering 7-47%. Although source proportions were correlated with δ^44/40Ca, conservative mixing remains an important control and cannot be fully excluded for all samples; secondary carbonate formation is therefore interpreted as a possible additional influence superimposed on source mixing. In high-altitude regions, δ^44/40Ca was positively correlated with both Sr/Ca and Mg/Ca, consistent with possible preferential removal of light Ca isotopes during carbonate precipitation. In low-altitude regions, δ^44/40Ca remained positively correlated with Sr/Ca, whereas the relationship with Mg/Ca was weak, suggesting stronger fractionation under longer water-rock interaction and slower flow conditions. Monte Carlo uncertainty propagation shows that the apparent α values for the high- and low-altitude groups are not statistically distinguishable within uncertainty. These results suggest that altitude-related hydrogeochemical settings modulate riverine Ca isotope behavior through combined effects of source mixing and possible secondary carbonate formation. This study demonstrates that altitude-driven hydrogeochemical variations govern riverine Ca isotope dynamics in the upper Yangtze, offering a robust tool for tracing secondary carbonate precipitation and quantifying carbonate weathering-related carbon fluxes in large river basins.