Environmental Science: Processes & Impacts最新文献

Livestock farms are important reservoirs of antibiotic resistance genes (ARGs). However, how wastewater irrigation from swine farms affects the surrounding environments, especially water bodies, is not fully understood. In this study, the occurrence pattern and potential risk of ARGs and mobile gene elements (MGEs) in a biogas slurry from a large-scale swine farm and its surrounding environments were investigated. Genes conferring resistance to tetracycline, sulfonamide, and multidrugs were found to be predominant in the biogas slurry, while sulfonamide and multidrug resistance genes exhibited the highest abundance in the surrounding environments. Overall, the total relative abundance of ARGs in the biogas slurry was 1.4–7 fold higher than that in the surrounding environments. PCA revealed the cluster pattern of samples based on sample types and a better correlation between swine farm wastewater and groundwater. A higher abundance of ARGs was found in groundwater farther away from the swine farm than that in nearby groundwater and surface water. Correlation analysis indicated that ARGs had a significant positive correlation with MGEs at each sampling site. The most abundant MGE IS6100 may mediate the horizontal transfer of lnuA from the swine farm to nearby groundwater. Considering the abundance, mobility, host pathogenicity, and the co-occurrence patterns with MGEs of ARGs, nine high-risk ARGs, namely, aadA2, aadA17, aac (6′)-Ib, tetX, tetG, tetM, oprJ, sul1, and ermF, were screened in the environment. Our results indicated that the swine farm wastewater had long-term effects on the surrounding surface water and groundwater and that MGEs can serve as a medium that contributes to the widespread distribution of various ARGs. This study provides a theoretical basis for the risk assessment of ARGs in farms and the reuse of farm wastewater.

Global climate change has increased temperatures and elevated atmospheric CO₂ concentrations in many forests, which can impact plant productivity. This changes both the quantity and quality of litterfall and root inputs to soil organic matter (SOM) and alters soil carbon (C). This study examined how litter exclusions (No Litter, No Roots, and No Inputs) and additions (Double Litter and Double Wood) altered soil C dynamics and SOM composition. Soil samples were collected from a temperate forest in Hungary (the Síkfőkút Experimental Forest) after 20 years of experimental litter manipulation. Elemental analysis, targeted SOM compound techniques, nuclear magnetic resonance (NMR) spectroscopy and microbial biomass and community composition measurements were used to characterize alterations to SOM stabilization and destabilization processes. Our results contrast other similar long-term detrital manipulation experiments of the same timeframe, with increases in soil C for both Double Litter and Double Wood, and evidence for enhanced microbial decomposition still occurring. In North America, aboveground inputs are more influential for soil C stabilization in coniferous forests, while belowground inputs are more important in temperate forests. However, this temperate forest in Central Europe is unique in that the specific ecological properties (such as litter quality, mean annual temperature and precipitation) dictated these processes instead. This highlights the differing responses detrital manipulation to forest soils across varying climatic and edaphic gradients and the sensitivity of SOM composition to changes in detrital inputs in different ecosystems.

Groundwater quality is strongly compromised by polluted surface water recharge in rapidly developing urban regions. However, gaps still remain in the understanding of the critical contaminants controlling water quality and the health risks associated with groundwater consumption, particularly considering seasonal and climate changes in rainfall. This work focused on changes in groundwater quality and critical contaminants in domestic wells in the fast-developing Pearl River Delta (PRD) from the wet season to the dry season. The stable isotope δD and δ¹⁸O values indicated that groundwater was largely impacted by precipitation and has experienced strong evaporation. The groundwater generally exhibited oxidizing and slightly alkaline properties and was predominantly of the Ca-HCO₃ type. Owing to the dominant water type of Ca-HCO₃ and the high concentrations of Ca, concerns related to hard water arose, particularly during the wet season, which promotes the need for water softening before groundwater use. Although the heavy metal pollution index (HPI) and water quality index (WQI) indicated excellent or good water quality, 34% and 47% of the groundwater samples presented elevated concentrations of arsenic and nitrate, respectively, compared with the WHO recommended levels, and the contamination level was elevated during the dry season. To our knowledge, this study is the first to report the fluoride concentrations in the PRD groundwater, with median values below 0.5 mg L⁻¹, underscoring the need for dietary fluoride supplementation. Health risk assessment confirmed the presence of both noncarcinogenic risks from arsenic and nitrate and cancer risk from arsenic in local populations resulting from groundwater consumption in the PRD region. This research emphasizes the importance of critical contaminants that constrain groundwater quality from different seasons with large variations in rainfall. Our work highlights the urgent need for the construction of adequate sanitation systems and for the control of agricultural nonpoint source pollution in rapidly urbanizing areas to safeguard both surface water and groundwater resources.

To evaluate the migration, transformation, and fate of tetrabromobisphenol A (TBBPA) in the environment, the transformation/degradation (T/D) products of TBBPA and byproducts of industrial production should be distinguished. Herein, 7 reported T/D products (R1–R7) and 7 novel byproducts (N1–N7) of TBBPA were identified in industrial-grade TBBPA chemicals by using high-performance liquid chromatography coupled ion trap mass spectrometry and high-resolution mass spectrometry with a suspect screening strategy. The possible formation pathways of these byproducts were attributed to the bromination, debromination, methylation, demethylation, hydroxylation, substitution, and radical coupling reactions of bisphenol A (BPA), BPA impurities, and TBBPA. The detection frequencies of R1–R7 and N3 (80–100%) were higher than those of N1, N2, and N4–N7 (20–60%) in industrial-grade TBBPA chemicals, with contents extended to 2.29% and 0.0989%, respectively. In the soils and sediments near the TBBPA plants, R1–R4 and N1 were detected with the highest concentration of 1.56 × 10² ng g⁻¹ dry weight, while in the river waters, only R1–R4 were detected with the highest concentration of 4.57 × 10² ng L⁻¹. An in silico analysis indicated the potential toxicity of these compounds, including their hepatotoxicity and carcinogenicity. To accurately estimate the environmental effects of the T/D products of TBBPA, the contributions of byproducts in industrial-grade TBBPA chemicals should be considered separately.

Septic tanks (STs) are an important pathway for chiral pharmaceuticals entering rivers. Therefore, the enantiospecific compositions of 25 chiral human pharmaceuticals and metabolites were investigated in five community STs over 12 months in Scotland. Large variability in pharmaceutical concentrations and enantiomeric fractions (EFs) were observed in wastewater owing to the small contributing populations. Pharmaceuticals prescribed in enantiopure and racemic forms had the greatest EF variability. For example, citalopram generally had EFs < 0.5 through consumption of the racemate and preferential metabolism of S(+)-citalopram. However, several samples had EFs > 0.7 from comparatively greater use of enantiopure escitalopram. Direct down-the-drain disposal was indicated for citalopram and venlafaxine, where elevated concentrations and pharmaceutical–metabolite-ratios were observed (at least 19-fold). Overall, EF differences between influent and effluent were small, suggesting no enantioselectivity occurred in anaerobic environments of STs. Therefore, EFs in ST effluent were notably different to those from aerobic wastewater treatment works (WWTWs). For instance, naproxen EFs (≥0.990 when both enantiomers detected) were like those of untreated wastewater but outside the range for aerobic WWTWs effluent caused by a lack of inversion from S(+)- to R(−)-naproxen in STs. This suggests naproxen can be used to identify its pathway into the environment, which was strengthened by river water microcosm studies. At the study locations the environmental risk of enantiomers was low due to sufficient dilution of effluents. Nevertheless, greater impact of individual practices towards medicine use and disposal on ST wastewater and receiving water composition demands enantioselective analysis to better appreciate the sources, fate and impact of pharmaceuticals.

Straw application is widely used to reclaim saline soils. However, the characteristics of straw mineralization and its induced priming effects (PE) in saline soil are largely unknown. Thus, we conducted a 180-day saline soil incubation experiment to observe the characteristics of straw mineralization and CO₂ emissions. Four salinity levels, i.e., 3.0 g kg⁻¹ (BS), 5.0 g kg⁻¹ (LS), 10.0 g kg⁻¹ (MS), and 15.0 g kg⁻¹ (HS), were established, to which ¹³C-labeled maize straw was added at a rate of 5.0%. Results showed that the straw mineralization rate and the amount of potentially mineralized straw significantly decreased with increasing salinity (p < 0.05). Compared with BS, the cumulative CO₂ emissions, PE, and the amount of mineralized straw in LS, MS, and HS decreased by 3.6%–26.8%, 3.4%–26.5%, and 2.7%–15.6%, respectively. Simultaneously, increasing soil salinity prompted the earlier occurrence of the peak straw mineralization and PE. The contribution of straw mineralization to CO₂ emissions on the 1st day significantly decreased with rising salinity levels (p < 0.05), while the opposite change was observed from 5 days to 120 days. Although PE significantly decreased with increasing salinity, the duration of the effect of straw input on soil organic matter mineralization increased substantially in high-salinity soils. These findings reveal the influence of soil salinity levels on the straw mineralization process and CO₂ emission, which will help us assess and boost carbon sequestration in saline soils under straw input conditions.

The Norfolk Southern train derailment on February 3, 2023, in East Palestine, Ohio, prompted concerns about the health impacts from the chemical spills and open-air combustion. We hypothesize that the combustion of chemicals, including vinyl chloride, in the presence of transition-metal oxides from the train, tracks, and soil minerals were conducive to the formation of hazardous byproducts including environmentally persistent free radicals (EPFRs), dioxins, and furans. We also hypothesize that these harmful byproducts of combustion have a shared origin and thus will have elevated concentrations in soil samples collected close to the derailment site when compared to concentrations in background soils. This study examined the co-occurrence of these soil contaminants from samples collected August 14–17, 2023, within a two-mile radius of the incident site to assess the concentration of EPFRs, dioxins, and furans. We measured elevated levels of EPFRs (average: 3.00 × 10¹⁷ spins per g) and dioxin/furan toxic equivalence (TEQ) (average: 32.8 pg g⁻¹) near the derailment area compared to background levels (EPFRs: 1.33 × 10¹⁷ spins per g; TEQ: 10.7 pg g⁻¹). Significant positive correlations (p < 0.002) between EPFRs and specific dioxin/furan congener concentrations (0.63–0.74) indicated robust associations between EPFRs and dioxin/furan congeners, the first such observations in field-collected soil samples. These results highlight the environmental health impact of the derailment and associated combustion, underscoring the need for comprehensive longitudinal monitoring and remediation efforts in the affected area and similar industrial accident sites. This study also offers insights into the formation mechanisms and persistence of EPFRs, dioxins, and furans.

Post-wildfire erosion to downstream surface waters can deteriorate water quality to levels that can create challenges for aquatic life and drinking water treatment. Polymeric additives, xanthan gum (XG) and polyacrylamide (PAM), have been demonstrated to be effective for controlling erosion in the presence of hydrophilic ash. However, with repeated rainfall applications, some of the applied XG and PAM may mobilize with the runoff and enter surface waters, which may pose water quality concerns. In this study, indoor rainfall simulation experiments were performed on plots containing wildfire-burned soil overlaid by hydrophilic ash collected after the 2021 Green Ridge Wildfire near Walla Walla, WA. The plots were treated with three concentrations (11, 33, and 60 kg ha⁻¹) of XG or PAM and subjected to three wet–dry cycles. Runoff water samples were collected at 5 min intervals during each wetting event. The pH, electrical conductivity, dissolved organic carbon (DOC), total dissolved nitrogen (TDN), and settled water turbidity (SWT) were measured for runoff water samples. The presence of XG in runoff from XG-treated plots increased SWT by up to 247% and DOC to as high as 16.6 mg_C L⁻¹. PAM treatment also increased DOC (up to 24.5 mg_C L⁻¹) and TDN (up to 5.8 mg_N L⁻¹) in runoff. DOC and TDN concentrations in runoff from treated plots increased with an increase in treatment concentrations and were generally greatest in the first wetting event. The results suggest that benefits of using polymeric additives for erosion reduction should be evaluated together with an assessment of dilution of downstream water bodies to alleviate the negative impacts of the additives on downstream water quality.

Plastics are widely used for their excellent properties, and the primary disposal method is sanitary landfilling. Waste plastics, persisting in landfills for long periods, change their surface physicochemical properties. However, research on the physicochemical changes of plastics after landfilling is scarce. This study analyzes the physicochemical characteristics of discarded plastics in landfills, focusing on depths (2–8 meters) and ages (0–30 years). The spatiotemporal distribution of waste plastics was studied using the 3D-Smoothe model. The results revealed that polypropylene (PP) and polyethylene (PE) were the predominant constituents of landfilled plastics. The carbonyl index (CI) and hydroxyl index (HI) accelerated with landfill age but increased and then decreased with landfill depth. Furthermore, the hydrophilicity of waste plastics increases with the landfill age, which is realized as 2 m > 5 m < 8 m in depth. The 3D model analysis indicates that PP displays a wavy downward trend in its spatiotemporal distribution, whereas PE exhibits a vortex-like downward trend. The toughness and strength of waste plastics rapidly decline in the early stages of landfilling and then stabilize. However, variations are noted at a depth of 5 m. The influence of landfill age on the mechanical properties of waste plastics is more significant than that of landfill depth by 3D model analysis. As the age and depth of landfills increase, there is a corresponding rise in the number of surface cracks and defects, a rise in surface roughness, and an increase in the abundance of surface elements. This study provides a scientific basis for understanding the environmental risks of landfilled waste plastics.

Multiple factors in the river–lake connected system can affect the transport and transformation of arsenic (As) in sediments. In this study, As source and sink characteristics under phosphorus (P) competition in sediments from river (R), lake (L) and lake-centre (LC) of river–lake connected system were analyzed, and the As release regionality and continuity were also discussed. The study showed that the ORP of the sediments at each site was negative with a mean value of −151 mV. The sediments in the R region were weakly acidic and those in the LC region were weakly alkaline. The R region had relatively high EAsC₀ concentrations, while the LC region had the largest EPC₀ value of 0.17 mg L⁻¹. As in the sediments competed very strongly with P for sources and sinks, with the sediments in the R region as a source of strong As and weak P, in the L region as a source of weak As and weak P, and in the LC region as an As sink and P source. Regions of high risk of As release from sediments were the R and L regions. Sediments in the L and LC regions had a high value of DAsS (the degree of As saturation), 8.9–13.1% and 8–13%, respectively, and the P release risk and saturation were inversely proportional to this result. The contribution analysis showed that surface sediments provided the largest contribution of As release, and the release contribution of As(V) was greater than that of As(III). In addition, the microbial community analysis identified Proteobacteria as the most abundant species in the sediments, with a relative abundance ranging from 42.4% to 53.2%. This bacterium, known for its As-metabolizing capabilities, was found to be positively correlated with the risk of As release. The analysis of As content in sediments revealed a gradient of R region < L region < LC region, confirming that rivers are significant contributors of As contamination to the lake.