Environmental Science: Processes & Impacts最新文献

Biosolids have been identified as a major source of microplastics (MP) to the environment. While they have been heavily studied, the impacts biosolids have following their amendment to agricultural soils on the MP content of these soils is poorly understood. Eleven biosolid-amended and nine non-amended agricultural fields in Southern Ontario were sampled to compare the MP content between them. Biosolid-amended fields averaged 2441.82 ± 268.03 MP kg⁻¹, while non-amended fields averaged 775 ± 50.97 MP kg⁻¹. Additionally, MP abundance was correlated with the type of biosolid applied, with fields that received a single application of dewatered biosolids averaging 2412.14 ± 174.81 MP kg⁻¹, whereas fields that received a single application of liquid biosolids averaged 1689.83 ± 225.81 MP kg⁻¹. However, differences in MP abundance were primarily dictated by differences in application rate between dewatered and liquid biosolids. In addition to increasing overall MP content, biosolid amendments influenced MP composition. Biosolid amendment increased soil fibre content, as biosolids are rich in textile fibres derived from the laundering process. As a result, biosolid-amended soils primarily contained polyester, while unamended soils primarily contained polypropylene. Quantifying and characterizing MP content in biosolid-amended fields, and understanding how it differs from unamended fields, is crucial for accurately assessing the risks microplastics pose to terrestrial ecosystems.

Brewing is an understudied but influential source of VOC emissions in the food manufacturing industry. In this study, we conducted a first comprehensive analysis of process-based VOC concentration characteristics, ozone formation potential (OFP), secondary organic aerosol formation potential (SOAFP) and health risks in two typical breweries in Beijing that use malted barley, hops, water, and yeast. In Brewery A, 35 to 53 distinct VOC species were detected, with total mass concentrations ranging from 148.17 ± 18.64 µg m⁻³ to 15 225.91 ± 1912.51 µg m⁻³. Brewery B demonstrated comparable patterns, with 28 to 49 species detected at concentrations between 104.49 ± 8.48 µg m⁻³ and 10 368.87 ± 879.47 µg m⁻³. Process-stage analysis identified boiling and fermentation stages as the key stages with the highest VOC concentrations, dominated by oxygenated VOCs (OVOCs) such as acetaldehyde, acetone, ethyl acetate, and 2-butanone, as well as the alkane isobutane. Atmospheric dispersion modeling (AERMOD) indicated negligible public health risks from organized stack emissions. In contrast, occupational health assessment revealed significant risks for workers from fugitive emissions, with the cumulative hazard index (HI) far exceeding the threshold. The OFP and SOAFP results, representing the secondary pollutant formation potential of the source mixtures, highlighted OVOCs and aromatics as priority control species for mitigating the secondary pollution potential. The findings demonstrate that VOC control strategies must be differentiated, with large-scale breweries prioritizing organized emissions, while small breweries urgently need to control fugitive emissions. This study aims to promote the implementation of VOC regulations and occupational health protection strategies within the brewing industry.

Assessing airborne fiber length and number in air samples is crucial for evaluating workplace exposure to asbestos and elongate mineral particles (EMPs). Growing concerns about noncommercial EMPs highlight the need for efficient monitoring methods. Phase Contrast Microscopy (PCM), used in the National Institute for Occupational Safety and Health (NIOSH) Method 7400, is a standard technique but is labor-intensive and time-consuming, examining only about 0.2% of the filter area and yielding 100–200 fiber counts. This study evaluates flow imaging microscopy (FIM) as a rapid, high-throughput alternative for measuring fiber number and length distribution. To validate its accuracy, monodisperse polystyrene latex standards (5–50 µm) were analyzed using 4X and 10X objective lenses. Test glass fibers were prepared as (i) suspensions in deionized water and (ii) aerosols collected on cascade mesh micro-screens to produce fibers of varying lengths. FIM demonstrated accurate sizing for spherical particles (5–50 µm), with biases under 13% for 4X and 3% for 10X. Counting accuracy biases were below 22% for 4X and 10% for 10X, with relative standard deviations (RSDs) of 4.7% and 9.0%, respectively. Fiber length distributions at 10X showed geometric mean lengths of 8.0–26 µm, closely agreeing with PCM (average bias ∼16.6%). Comparisons of fiber density showed that discrepancies between the two methods decreased as fiber counts increased, highlighting the significance of high-throughput measurement with FIM. The results indicate that FIM's high-throughput ability shows potential for analyzing workplace air samples more quickly and cost-effectively, while still providing superior counting statistics.

The goals of this study were to measure sorption kinetics, solid–water partitioning (log K_d values) as a function of pH, and percent desorption for a diverse set of PFASs on four highly abundant soil and aquifer minerals. We found that PFAS sorption was relatively fast on all four minerals and that overall log K_d values were higher for ferrihydrite and montmorillonite than for goethite and kaolinite, possibly driven by differences in surface area. We also found that log K_d values on ferrihydrite and goethite were dependent on pH levels and the length of the perfluoroalkyl chain. Significant differences in log K_d values between the iron oxide minerals were explained by differences in their respective point-of-zero-charge, and changes in PFAS speciation as a function of pH amplified those differences. Despite the relatively high log K_d values of the iron oxide minerals reflecting relatively high affinity for PFASs, facile desorption from the iron oxides suggests that PFAS sorption is driven by relatively weak electrostatic interactions. The log K_d values on montmorillonite and kaolinite were not significantly dependent on pH levels, but were dependent on the length of the perfluoroalkyl chain. Less facile desorption from the silica clay minerals suggests that PFAS sorption is driven by relatively strong hydrophobic and electrostatic interactions. Together, our data make practical contributions to support site characterization and remediation efforts, while also contributing key insights into the fundamental sorption processes.

Phenanthrene poses carcinogenic, teratogenic and mutagenic risks to plants and soil invertebrates. However, the absence of established soil ecological safety thresholds of phenanthrene has resulted in insufficient evidence in the current risk assessment for soil ecological security. To fill this gap, toxicity data from laboratory experiments and the existing literature, covering 16 plant species, 7 invertebrates, and 3 soil ecological processes, were applied to the species sensitivity distribution approach to determine the soil ecological safety thresholds of phenanthrene across different land types. From experimental results, we found that the effect concentration at 10% values for most plants had a positive correlation with pH, soil organic matter content, cation exchange capacity, and electrical conductivity values. The soil ecological safety thresholds of phenanthrene were estimated to be 7 mg kg⁻¹ for agricultural and forestry land with the hazardous concentration for 5% of the species affected (HC₅), 35 mg kg⁻¹ for green spaces and squares with HC₂₀, 95 mg kg⁻¹ for residential land with HC₄₀, and 122 mg kg⁻¹ for commercial and industrial land with HC₅₀, respectively. These findings will serve as a foundation for the ecological risk assessment of phenanthrene on land for different purposes, and are of great significance for ecological species protection.

Bubble bursting during oceanic breaking waves releases tiny droplets that can transport species—including sea salt, microorganisms, and microplastics—across the air–water interface. While many studies have investigated particle–bubble interactions and the role of particle wettability in particle attachment to rising bubbles, a limited number have extended this to particle aerosolization onto the ejected droplets. This study aims to experimentally investigate how wettability of microplastic (MP) particles affects their aerosolization via the two major droplet ejection pathways from a bursting bubble: film and jet drops. Controlled experiments are conducted with 1 µm diameter surface-modified polystyrene MPs of two contrasting wettabilities (i.e., hydrophilic vs. hydrophobic) in ultrapure water. Film and jet drop pathways are isolated by generating two distinct bubble populations known to primarily produce each droplet type. The results show that the aerosolization factor – defined here as the air-to-water MP concentration ratio – of hydrophobic MPs is approximately one order of magnitude higher than that of hydrophilic MPs for jet drops. In contrast, no significant difference was observed for the film drop aerosolization factor, which can be attributed to a potentially complex effect that MP particles can have on bubble film stability, bursting, and enrichment dynamics. These findings highlight that MP surface properties can significantly influence their ejection into the atmosphere at the ocean surface. Given the potential for inhalation and long-range transport, this mechanism may contribute to the global dispersion of airborne MP pollutants. The results underscore the need to consider aerosolization pathways in the environmental fate and risk assessment of plastic pollution.

Waters contaminated with toxic hexavalent chromium [Cr(VI)] can contain co-occurring metals and organic compounds, promoting simultaneous redox, complexation, and precipitation reactions. This study systematically investigates how Fe minerals, aqueous Fe(II) and Cu(II), and various low molecular weight organic compounds induce Cr(VI) adsorption, reduction, and precipitation reactions. Through batch and column experiments and microscopic and spectroscopic analyses, we determine how aqueous metals and organic compounds interact with Cr(VI) to promote sequestration or release of Cr adsorbed to iron (oxyhydr)oxides. Aqueous Cu precipitates from solution, which removes Cr(VI) from the water column, but may prevent some Cr(VI) from being reduced. With the addition of ascorbic acid, Cu can be mobilized as Cu(0) colloids with Cr also being released. Aqueous Fe(II) promotes Cr(VI) reduction, but also may mobilize Cr associated with reacted Fe (oxyhydr)oxides. The results identified in our study provide insights about overlooked reactions that can control the sequestration and release of Cr in contaminated waters containing complex mixtures of inorganic and organic chemicals which have relevant implications for remediation strategies and recovery of critical minerals.

The saturated sorption capacity of Cr(VI) in soil is determined by reduction and adsorption processes. Red soil, paddy soil, black soil, and fluvo-aquic soil were selected for repeated sorption experiments in this study to determine Cr(VI) saturated sorption capacity as well as reduction/adsorption capacities and the contributions of key factors were analyzed through regulating soil properties. The results showed that the saturated sorption capacities of the four soils were 972, 589, 551, and 76 mg kg⁻¹. Per pH unit increase, saturated sorption capacity decreased in the order: red soil (142 mg kg⁻¹) > paddy soil (134 mg kg⁻¹) > black soil (132 mg kg⁻¹) > fluvo-aquic soil (25 mg kg⁻¹). Specifically, red soil showed a significantly greater drop in adsorption capacity (50 mg kg⁻¹) than the other three soils; paddy soil and black soil had over 27% decrease in reduction capacity, while fluvo-aquic soil exhibited no significant change. Organic matter removal decreased reduction capacities by over 60% but increased adsorption capacities by over 20%. Removing Fe and Al oxides significantly reduced adsorption capacities by over 50%; Mn oxide removal had minor impact. Correlation analysis and random forest modelling identified pH as the primary factor influencing soil Cr(VI) sorption, contributing 27.8%, 45.4%, and 28.0% respectively to saturated sorption capacity, reduction capacity, and adsorption capacity. Adsorption capacity was mainly affected by Fe, Al and Mn oxides, collectively contributing 70.5%, while organic matter mainly affected reduction capacity, contributing 26.6%. This initial quantitative analysis provides new insights into the fate of Cr(VI) in soil environments.

Wetlands deliver essential ecological services but are increasingly threatened by heavy metal(loid)s (HMs) due to anthropogenic activities. The speciation of HMs, which dictates their toxicity and mobility, can be transformed by microbial redox processes like anaerobic oxidation of methane (AOM). However, the contribution of AOM to HM speciation transformation in wetland soils remains inadequately assessed. This review summarizes the current understanding of how AOM couples with the reduction of various elements to directly or indirectly affect HM speciation. These elements include arsenate, chromate, selenate/selenite, antimonate, vanadate, Fe(III), Mn(IV), and sulfate. We examine the responsible microorganisms and their electron transfer pathways, and evaluate the potential for applying these AOM processes in the remediation of HM contamination. These AOM processes can potentially influence the reduction, mobilization, or immobilization of HMs, thereby regulating their biogeochemical cycles in wetland soils. Future research priorities include determining the role of aerobic methanotrophs in these processes, clarifying the impacts of environmental conditions and HM forms, and developing targeted AOM regulation strategies for remediating contaminated wetlands. This work advances the mechanistic understanding of the interactions between HMs and AOM, and provides theoretical insights for developing remediation strategies for HM-contaminated wetland soils.

Microbial communities serve as critical bioindicators and functional drivers of soil restoration processes, particularly in mining-impacted ecosystems undergoing remediation. However, systematic insights into microbial dynamics during clean water restoration of contaminated paddy soils remain limited. This study systematically investigated, by means of column experiments, the temporo-spatial dynamics of microbial community structure and metal speciation in acid mine drainage (AMD)-contaminated paddy soil from the Dabaoshan mining area. The soil was subjected to constant flooding with clean water, including experiments with artificial AMD as a control, for 176 days. The heavy metal fractions present in the soil were determined by sequential extraction. The bacterial community was analyzed at 7 time points and 5 depths using high-throughput 16S rRNA gene amplicon sequencing of the V5–V7 region. Long-term flooding increased the dominance of Firmicutes, Acidobacteria, and Proteobacteria, with limited overlap in significantly enriched taxa during restoration, indicating specialized microbial adaptation or microbial selection. The metal mobility increased as a result of flooding, most strongly in the mobile fractions of Cd at 5 cm depth (FM increased from 62.6% to 68.7%) and Cu at 20 cm depth (FM increased from 16.2% to 21.6%). This was accompanied by a substantial reduction in the residual total reducible-phase Cu (the sum of Fe/Mn oxide-bound fraction F3 and the organic-matter-bound fraction F4) was reduced from 188.4 to 30.8 mg kg⁻¹. Likewise, residual easily migratable Cd (the sum of exchangeable fraction F1 and carbonate-bound fraction F2) was reduced from 5.8 to 0.3 mg kg⁻¹. Such increased mobility might present an increased environmental risk. Canonical correspondence analysis identified the pH, Cu/Cd concentrations, and SO₄²⁻ as primary environmental drivers (cumulative explanation: 72.3%) governing microbial community restructuring. Complementary LEfSe analysis further elucidated potential microbial interaction networks underlying the rehabilitation process. The identified microbial-metal dynamics highlight the importance of integrating biological indicators with geochemical parameters when assessing the rehabilitation efficacy in heavy metal-contaminated agricultural systems.