Environmental Science: Processes & Impacts最新文献

Silicon-containing materials have been widely used in Cd-contaminated soil remediation. However, the immobilization effects of sodium silicate on Cd migration and transformation in an acidic soil-vegetable system have not been thoroughly studied. Herein, a pot experiment was performed to investigate the effects of sodium silicate application on pak choi growth, oxidative status, Cd uptake and accumulation in pak choi, soil Cd bioavailability and fractions, and soil bacterial communities. The results showed that sodium silicate application significantly increased soil pH (0.29-1.61 units) and induced the transformation of the Cd fraction from an exchangeable fraction (Exc-Cd) into an iron and manganese oxide-bound fraction (OX-Cd) and organic matter-bound fraction (OM-Cd), decreasing Cd bioavailability by 13.7-20.8% in Cd-contaminated acidic soil. As a result, sodium silicate application significantly alleviated Cd toxicity, enhanced pak choi growth, and reduced Cd concentration in roots by 23.5-89.0% and in shoots by 58.5-81.0%, with Cd concentration in the edible part at a Si application rate equal to or greater than 0.4 g Si per kg soil falling below the safety limits for Cd as defined in China's food safety standard (GB 2762-2022). In addition, sodium silicate application significantly increased soil bacterial richness (Ace index and Chao1) and diversity (Shannon and Simpson index) and altered the soil microbial structure. These findings suggested that sodium silicate has great potential as an environmentally friendly amendment to immobilize Cd-contaminated acidic soil and reduce Cd accumulation in vegetables.

Graphene has garnered significant attention due to its unique and remarkable properties. The widespread application of graphene materials in numerous fields inevitably leads to their release into the environment. This study examines the long-term impacts of graphene on anaerobic sequencing batch reactors. The low-concentration graphene (5 mg L^-1) exhibited a significant inhibitory effect on the removal of chemical oxygen demand, while the high-concentration group (100 mg L^-1) was less affected. The transmission electron microscopy and Raman spectroscopy results demonstrated that the anaerobic sludge could attack graphene materials, and cell viability tests showed that high concentrations of graphene were more conducive to microbial attachment. High-throughput sequencing revealed significant alterations in the microbial community structure under graphene pressure. Methanobacterium and Actinomyces gradually became the dominant genera in the high-concentration group. Network analysis showed that graphene increased the complexity and interaction of microbial communities. Additionally, high-throughput qPCR analysis demonstrated that graphene influenced the dynamics of antibiotic resistance genes, with most exhibiting increased abundance over time, especially in the low-concentration group. Consequently, when considering the application of graphene in wastewater treatment, it is crucial to evaluate potential risks, including its effects on system performance and the likelihood of antibiotic resistance gene enrichment.

Anionic surfactants are widely used in commercial and industrial applications. For assessment of their environmental fate and effects, it is highly desirable to quantify the membrane-water partition/distribution coefficient (K_mw/D_mw). Here, we further develop a computational route to D_mw for anionic surfactants based on coarse-grained molecular dynamics simulations, validating it against new and existing experimental measurements. Having parameterised molecular fragments for the coarse-grained models, the simulations are used to predict D_mw for molecules where no experimental values are available. This expanded set of simulated D_mw values is then used to derive QSARs for acute toxicity of mono-constituent anionic surfactants in daphnids and fish, allowing for extrapolation to similar compounds without experimental D_mw values. For this study, we have selected hydrocarbon-based (HC) surfactants because of their widespread use, and perfluorinated (FC) surfactants as a challenging case study. Separate daphnid and fish QSARs demonstrate good fits, robustness and predictivity, and highlight differing toxicity relationships for HC and FC surfactants in daphnids. Overall, the combined use of simulated D_mw and derived QSARs is a promising approach for ecotoxicity screening of surfactants.

Fine-grained dust from tailing storage facilities in abandoned sulfide-ore mining areas represents an important source of environmental contamination. Fine fractions (<48 μm and <10 μm) of tailings from three old mining sites situated along a climatic gradient from hot semiarid to cold desert conditions in Namibia were studied: Kombat (Cu-Pb-Zn; rainfall ∼500 mm), Oamites (Cu; ∼120 mm), Namib Lead & Zinc (Pb-Zn; ∼0 mm). Multi-method mineralogical and geochemical investigations were adopted to assess the binding and gastric bioaccessibility of the metal(loid)s and to evaluate the associated human health risks. The total concentrations of contaminants in the tailings generally increased with the decreasing particle size (up to 134 mg As kg^-1, 14 900 mg Cu kg^-1, 8880 mg Pb kg^-1, 13 300 mg Zn kg^-1). The mean bioaccessible fractions varied substantially between the sites and were significantly higher for the tailings from the sites with a higher rainfall (73-82% versus 22%). The mineralogical composition of the tailings, reflecting the original mineralogy and the degree of the weathering process, is the main driver controlling the bioaccessibility of the metal(loid)s. In desert environments, metal(loid)s in tailings are bound in sulfides or sequestered in secondary Fe oxyhydroxides and/or Fe hydroxysulfates, all of which are insoluble in simulated gastric fluid. In contrast, tailings from areas with higher precipitation contain metal(loid)s hosted in carbonate phases (malachite, cerussite), which are highly soluble under gastric conditions. Based on the higher contaminant bioaccessibility, the vicinity of the settlement and farmlands, and a higher percentage of wind-erodible fine particles, a higher risk for human health has thus been identified for the Kombat site, where further remediation of the existing tailings storage facility is highly recommended.

The discharge of treated wastewater effluents into river-fed irrigation canals results in a de facto form of water reuse. Waterborne fungal populations in such environments pose a unique human health concern given that opportunistic fungal pathogens can be proliferated during spray irrigation of crops. In the present study, we consider two different routes (effluent discharge versus bioaerosols) through which wastewater treatment plants (WWTPs) can impact the presence and abundance of fungal communities in irrigation canals of the Rio Grande river basin in New Mexico. Site A was selected to investigate the influence of effluent discharge from a WWTP on waterborne fungal communities in a receiving irrigation canal. Site B represented an irrigation canal that was directly adjacent to a WWTP but that receives no effluent discharge (to exemplify bioaerosolization exclusively). Sampling dates were chosen to capture variations in weather and stream flow conditions at each of the two sites. Results indicated that treated wastewater discharged into the canal had a distinct impact on fungal community composition, especially under low wind and flow conditions. When stream flow was highest, variations along the canal at Site A were minimal. The highest occurrence of pathogen-associated genera was observed at Site B under high wind conditions with an average relative abundance of 20.9 ± 13.1% (peak of 39.3%) and was attributable to bioaerosol emissions from the WWTP and a nearby livestock facility. Such genera included Alternaria, Cladosporium, and Cryptococcus. These findings suggest that although treated effluent discharge can directly impact irrigation canal fungal community composition, bioaerosols likely have a larger overall effect on the spread of potential fungal pathogens.

The impact of organophosphate pesticide (OPP) exposure on osteoporosis in adult population remains unclear. Thus, it is necessary to explore the association between the exposure to a mixture of OPPs and the prevalence of osteoporosis as well as to identify the major contributor of OPPs in this association. Participants were selected from the 2005-2008 cycle of the NHANES cross-sectional study. OPP exposure was estimated using six different metabolites found in urine. Dual-energy X-ray absorptiometry (DXA) was used to measure bone mineral density (BMD). Survey-weighted generalized linear regression models (SWGLMs) were used to estimate the association between individual OPP exposure and osteoporosis/BMD. Weighted quantile sum (WQS) regression and quantile g-computation (Qgcomp) models were used to assess the mixture of OPPs and identify the key pollutants. SWGLMs indicated that higher concentrations of dimethyl dithiophosphate (DMDTP) and diethyl dithiophosphate (DEDTP) were associated with increased osteoporosis risk in the upper quartiles. WQS models revealed a significant combined effect of six OPP metabolites on osteoporosis (OR = 1.35, 95% CI: 1.06-1.73, P = 0.015), femoral neck BMD (β = -0.012, 95% CI: -0.020, -0.004, P = 0.003) and lumbar spine BMD (β = -0.015, 95% CI: -0.025, -0.006, P = 0.001), with DMDTP and DEDTP identified as key pollutants. Results from the Qgcomp models showed no substantial changes. This study indicated that exposure to both individual OPPs and their mixtures were associated with decreased BMD and increased osteoporosis risk, with DMDTP and DEDTP identified as major contributors to these associations. This underscores the need to prioritize control of these two pollutants to limit their exposure for osteoporosis prevention.

Many historic landfill sites have groundwater plumes that discharge to nearby surface waters. Recent research indicates that leachate of historic landfills can contain elevated concentrations of per- and polyfluoroalkylated substances (PFAS), but there is limited data on resulting PFAS inputs to aquatic ecosystems as might inform on this potential environmental threat. The objective of this study was to evaluate PFAS exposure in three ecological zones and PFAS mass loading downstream, over 1 year, at two historic landfill sites where landfill plumes discharge to nearby surface waters (1 pond with outlet stream, called HB site; 1 urban stream, called DC site). The three zones experienced different magnitudes and patterns of PFAS concentration exposure (i.e., contaminant presence in the zone). The endobenthic zone of the sediments receiving the landfill plumes experienced the highest concentrations (∑PFAS >4000 ng L^-1 (HB) and >20 000 ng L^-1 (DC)), often year-round and over a substantial area at each site. Dilution of landfill PFAS in surface waters was observed though concentrations were still elevated (∑PFAS: >120 ng L^-1 (HB) and >60 ng L^-1 (DC)), with evidence of year-round pelagic zone exposure. PFAS concentrations in the epibenthic zones could vary between that of the endobenthic and pelagic zones, sometimes with daily, event-based, and longer-term patterns. Together these findings suggest historic landfill plumes can lead to substantial PFAS exposure to a variety of aquatic life. Downstream PFAS mass loadings during base flows were relatively small individually (15 (HB) and 36 (DC) g per year (∑PFAS)); however, collective loadings from the numerous historic landfills in a watershed could contribute to increasing PFAS concentrations of connected water bodies, with implications for ecological health, drinking water sources, and fisheries.

Phytoremediation is an effective technology for removing heavy metal cadmium (Cd) from soil without harming the soil; however, it is limited by its long remediation time and low efficiency. In this study, a plant growth regulator (PGR), triacontanol, was sprayed on the leaves of the hyperaccumulator Tagetes patula L. at different growth stages to enhance the accumulation of soil Cd, thereby ultimately enhancing the efficiency of phytoremediation. Results showed that leaves were the main site of Cd accumulation in T. patula, and foliar application of triacontanol increased the leaf biomass and Cd content, with maximum values of 14.69% and 15.44%, respectively. Furthermore, the Cd removal rate in the soil increased to 11.53%. The effect of a single application of triacontanol on Cd accumulation was better than that of two applications, and the bloom period was found to be the best application stage. The proportion of Cd in the cell walls increased, enhancing Cd fixation ability. The photosynthetic efficiency and antioxidant capacity of T. patula improved significantly. In the roots, metabolomic and transcriptomic analyses indicated that triacontanol promoted the metabolism of low-molecular-weight organic acids, leading to an increase in the available and exchangeable Cd in soil, with maximum values of 14.72% and 2.29%, respectively. The upregulation of Cd transport-related genes and pathways in the roots strengthened their ability to absorb Cd and resist Cd stress. These findings systematically elucidated the molecular mechanism of triacontanol-enhanced Cd accumulation in T. patula and provide technical support for its wide application.

The agricultural sector plays a pivotal role in Hainan Province, China; therefore, the utilization of pesticides is indispensable. The current ban on traditional pesticides and ongoing replacement of current-use pesticides (CUPs) have not been accompanied by extensive research on the presence of CUPs in reservoirs, which are vital centralized sources of drinking water. In this study, 26 CUPs was investigated in a drinking water source reservoir, the surrounding watershed, and the surrounding agricultural and domestic discharge water in Hainan Province. The predominant detected CUPs in the study area were clothianidin (CLO), thiamethoxam (THM), acetamiprid (ACE), imidacloprid (IMI), and dichlorvos (DCH). Neonicotinoids (NNIs) were the primary type of pesticide contamination in the study area, with a concentration ranging from not detected (n.d.) to 755 ng L^-1 (median of 71.0 ng L^-1). The upstream watersheds of the reservoir were primarily contaminated due to agricultural activities, and the highest concentration of individual CUPs, ranging from 102 to 821 ng L^-1 (median of 468 ng L^-1), was found in agricultural source water. Source identification analysis revealed that the presence of CUPs in the reservoir primarily stemmed from three types of activities: the cultivation of fruit trees around the reservoir, the daily activities of residents, and the agricultural practices in the upstream watershed basin. Risk assessment indicated that DCH, IMI, and THM posed moderate or high risks to aquatic organisms, with an emphasis on the effects of NNIs. The chronic cumulative risk assessment of NNIs was conducted by the relative potency factor approach, and it indicated that infants and young children were the most vulnerable groups and exhibited heightened susceptibility. The potential exposure to NNIs through drinking water was below the recommended relative chronic reference dose, thereby posing no discernible health risks. The results of this study will support the regulation of CUPs in drinking water sources.

Textiles play an important role in the accumulation of harmful chemicals and can serve as a secondary source of chemical pollutants in indoor environments, releasing these chemicals back into indoor air, as well as a vector from which indoor pollution can be released by laundering to wastewater systems. Among harmful indoor pollutants, aromatic amines (AAs) are particularly concerning due to their mutagenic and carcinogenic properties, but have received limited attention in non-occupational indoor environments. We have characterized the distribution of 19 AAs between cotton, wool, and polyester textiles and air. Chamber exposure experiments were conducted under controlled laboratory conditions to quantify textile-air distributions of AAs and identify key parameters impacting the distribution. The mass-normalized textile/air distribution coefficients (K_TA) of AAs for polyester, cotton, and wool range from 5.28 to 9.52 log units (L kg^-1). The findings suggest that cotton generally exhibits higher distribution coefficients than polyester and wool for most analytes. Overall, the results show a strong positive relationship between octanol-air distribution coefficients (K_OA) and K_TA values. The consistent uptake capacity of all tested textiles for AAs highlights the potential for textiles to play a key role in AA indoor distributions.