Environmental Science & Technology Letters Environ.最新文献

Arsenic is a global pollutant. Recent studies found that Fe(II) can oxidize As(III), but the extent of oxidation with mixed-valent iron minerals and the mechanisms involved are unknown. In this study, we investigated whether As(III) can be oxidized under reducing conditions using green rust sulfate (GR-SO₄), an Fe mineral containing both Fe(II) and Fe(III). Batch sorption experiments showed that GR-SO₄ (1 g L^-1) effectively sorbs environmentally relevant concentrations of As(III) (50-500 μg L^-1) under anoxic, neutral pH conditions with and without citrate (50 μM). X-ray absorption near-edge structure spectroscopy analysis at the As K-edge demonstrated that approximately 76% of As(III) was oxidized to As(V) by GR-SO₄. Complete oxidation of As(III) was observed in the presence of citrate. As(III) oxidation can be linked to the phase transformation of GR-SO₄ to goethite, resulting in new reactive Fe(III) species that plausibly drive oxidation. Citrate enhanced this process by stabilizing Fe on the mixed GR-SO₄/goethite surface, preventing its reduction back to Fe(II) and facilitating further As(III) oxidation without significant Fe loss to the solution. This study highlights the cryptic As(III) oxidation that occurs under reducing conditions, providing new insights into the cycling of arsenic in mixed phases of iron-rich, anoxic environments.

Increasing pressures on traditional sources of water have accelerated the adoption of water reuse throughout the world. A key consideration for communities pursuing water reuse is understanding the amount of treatment that is needed to ensure adequate human health protection. Several U.S. EPA documents describe the importance of managing acute microbial risks and highlight the utility of quantitative microbial risk assessment for developing "fit-for-purpose" treatment targets based on the source of water and end-use. However, there are no U.S. federal water reuse regulations and states are currently considering microbial treatment targets for various applications. Previous publications have yet to address this need by using an updated and consistent set of input parameters to present risk-based microbial treatment targets across a wide range of sources of water, end-use applications, and health benchmarks. This work combines the most current modeling inputs and dose-response parameter values to provide probability of infection and disease burden-based microbial treatment targets for untreated municipal wastewater, untreated onsite wastewater, graywater, stormwater, and roof runoff water used for potable reuse, indoor nonpotable use, and landscape irrigation applications.

Soil system properties control the fate of essential Zn and toxic Cd, which can have pervasive influences on ecosystem health. However, direct evidence of the spatial distribution of trace metals within the organo-mineral soil architecture is lacking, though this knowledge is important to better predict the fate of trace metals in ecosystems. Here, we present a spectromicroscopic approach to map the distribution of Zn and Cd between mineral phases and organic matter at a resolution of approximately 150 nm. This was achieved using nanoscale secondary ion mass spectrometry (NanoSIMS) applied to a spiked gradient of Zn and Cd concentrations in an arable soil. We observed patchy-distributed Zn and Cd hotspots in all soils, including at a native concentration in the nonspiked soil. With increasing Zn and Cd spikes, these metals preferentially colocated with Fe-dominated mineral phases, whereas with the highest spike, Zn and Cd increasingly colocated with clay minerals and soil organic matter. Soil extracts suggested that large proportions of spiked Zn and Cd were tightly bound to the colocated phases. Our direct measurements of patchy-distributed Zn and Cd hotspots indicate that distinct soil surfaces preferentially allocate and govern the fate of trace metals in soils.

Rapid growth in the emissions of nitrogen trifluoride (NF₃), a potent greenhouse gas, poses a threat to the environment and the climate system. This study estimated NF₃ emissions and their spatial distribution in China from 2017 to 2021 based on atmospheric observations from nine background stations in China, by employing a Lagrangian-dispersion-model-based Bayesian inversion technique. We found that NF₃ emissions in China increased from 0.95 (0.82–1.07) Gg yr^–1 in 2017 to 1.41 (1.28–1.55) Gg yr^–1 in 2021, representing a substantial growth of 48% over this period. The absolute increase in NF₃ emissions in China over 2017–2020, 0.65 (0.57–0.74) Gg yr^–1is comparable to the increase in global emissions (0.63 (0.50–0.75) Gg yr^–1) over the same period. We identified substantial NF₃ emissions in the Pearl and Yangtze River Delta regions and Hubei Province, where well-established semiconductor industries could have contributed to NF₃ emissions. Moreover, large NF₃ emissions were identified in northern China, including Hebei, Henan, and Shandong Provinces. If control measures are not implemented, increasing NF₃ emissions may delay China’s progress toward achieving its carbon neutrality target by 2060.

Methanol is commonly used as a carrier solvent in environmental chemistry experiments; however, the possible influence of methanol on the kinetics of chemical transformations is often overlooked. The effects of methanol and other frequently used carrier solvents on the chlorination rates of aromatic precursors of disinfection byproducts during water chlorination were investigated. At concentrations as low as 0.50 vol %, methanol increased chlorination rates of ethylparaben, phenol, 4-hydroxybenzoic acid, ethyl 3-hydroxybenzoate, and ethyl 2-hydroxybenzoate. Methanol did not increase the chlorination rates of salicylic acid, dimethenamid, or 1,2-dimethoxybenzene. Ethylparaben and phenol chlorination were especially sensitive to methanol, with pseudo-first-order rate constants (k_obs) increasing by a factor of >2 in water containing 2.0 vol % methanol compared to those in methanol-free controls. Rate enhancements persisted across differing reaction conditions (pH 6–10 and in buffers containing borate or phosphate). The rate enhancements of unsubstituted and para-substituted phenols were larger than those of meta- and ortho-substituted phenols. The carrier solvents acetone, acetonitrile, and tert-butanol had no appreciable impact on the chlorination rates of ethylparaben. Overall, our findings suggest that methanol as a carrier solvent can cause systematic errors in lab-scale chlorination experiments. To avoid experimental artifacts, researchers should prepare stock solutions in water (when feasible) or minimize carrier solvent concentrations present in reaction solutions.

Since the Eocene, oviparous deep-sea sharks and rays have used deep-sea hydrocarbon seeps and hydrothermal vents as nurseries, where they lay eggs en masse. Benthic fluxes in these extreme habitats may enrich seawater with toxic metals such as mercury (Hg). We asked whether this phenomenon may lead to Hg accumulation in elasmobranchs. We thus analyzed total Hg (THg) in muscle, liver, and kidney tissues of oviparous Galeus melastomus catsharks and their embryos, which aggregate in vast numbers near deep-sea brine pools in the southeastern Mediterranean Sea. These Hg-rich brines (≤238 ng L^–1) are a likely liable geogenic Hg source in this nursery. Shark tissues carried substantial THg [2.7 μg (g of wet weight)⁻¹, median], and extreme values were found in kidneys [≤26.7 μg (g of wet weight)⁻¹], likely due to environmental uptake. Increased THg in embryos [0.64 ± 0.31 μg (g of wet weight)⁻¹] implies substantial maternal offloading (∼20%). Our results hint at the potential adaptation of elasmobranchs to Hg-enriched environments via accumulation and elimination of Hg in kidneys.

Brown carbon (BrC) is a crucial light-absorption component in the atmosphere, playing a profound role in the radiation budget. Variations in the light-absorption properties and molecular composition of BrC due to atmospheric photochemical aging process have not been well constrained, leading to high uncertainty in evaluating its global radiative effect. The molecular composition of atmospheric BrC were investigated to stress the BrC photobleaching in this work. In total, 896 organic compounds were identified, which accounted for 2.5%–26.1% of organic aerosol in mass concentration. We found that solar radiation led to the declined mass absorption coefficient at 375 nm (MAC₃₇₅), indicating BrC photobleaching, coinciding with an elevated mass fraction of carboxylic acids (CAs). This phenomenon was more pronounced under higher-energy solar radiation. Specifically, the mass fraction of nitrocarboxylic acids (NCAs) in CAs increased during BrC photobleaching, which was potentially caused by the oxidation of nitrophenols, resulting in an ∼83.3% decrease in MAC₃₇₅. Our findings provide direct observational evidence of BrC photobleaching from a molecular-level perspective and elucidate a potential BrC photobleaching pathway in the urban atmosphere.

A limited understanding of urban methane (CH₄) emissions in China challenges the evaluation of the coal-to-gas switch toward carbon neutrality by 2060. CH₄ flux was measured in urban Beijing using the eddy covariance method during a summer campaign. With a mean of 152.6 ± 107.9 nmol/m²/s, the CH₄ flux was estimated to depend little on the intensity of human activities, with minimal influence from biogenic sources. Emission hotspots with large temporal variability were identified in the study fetch area, which increased the mean CH₄ flux by 12.5%. Based on the lack of large, known biogenic sources in nonhotspot (background) areas, we attributed the CH₄ flux in these areas (135.6 ± 70.56 nmol/m²/s) mainly to natural gas. Thus, we estimate as an upper limit that natural gas contributes 88.9% to the total CH₄ flux in urban Beijing. However, poor alignment between the dominant sources in the inventories and the characteristics of the measured CH₄ flux were observed, suggesting substantial underestimation of emissions from natural gas sources in the inventories. A leakage ratio of 1.4% (0.7–2.1%) of consumed natural gas was determined in Beijing. Pinpointing emissions with more granular methods could improve our understanding of the urban CH₄ source profile in Beijing.

p-Phenylenediamines (PPDs) are emerging pollutants in the environment due to their extensive application in rubber-related products, yet their potential indoor exposure has been largely overlooked. This study investigated the occurrence characteristics of PPDs and their oxidative products (PPD-Qs) in dust from indoor, i.e., auto repair workshops, hardware malls, and home furnishings markets, as well as outdoor environments, i.e., highway and motorway intersections, revealed the influencing factors for transformation, and assessed associated exposure risks. The presence of PPDs and PPD-Qs in specific indoor environments has been documented. Particularly high levels of these compounds were observed in dust from auto repair workshops (median: 1.68 × 10³ ng/g (PPDs) and 421 ng/g (PPD-Qs). The indicator monomers for PPDs and PPD-Qs emitted from different sources were identified. Furthermore, through concentration analysis and theoretical calculations, the transformation from PPDs to PPD-Qs was revealed to be influenced by the total organic carbon and transition metals present in the dust with Fe³⁺ and Cu²⁺ acting as the most effective catalysts. Finally, occupational populations in environments such as auto repair workshops were found to face extremely high exposure levels. This study emphasizes the need to recognize and address the risks associated with these compounds indoors.