ACS Environmental Au最新文献

The back diffusion of trichloroethylene (TCE) between low permeability zones (LPZ) and transmissive zones in the subsurface presents remediation challenges. This study investigates in situ chemical oxidation (ISCO) using a sodium persulfate sustained release rod (SPS SR-rod) for potential TCE remediation in the LPZ within a two-dimensional sand tank. The tank simulates a dual permeability porous medium with hydraulic gradients of 0.01 and 0.05. The SPS SR-rod placed within the LPZ released an average PS concentration of ∼625 mg/L laterally, with initial peak concentrations of 7000-10,000 mg/L. When the rod was placed atop the LPZ, lower PS concentrations were observed compared to placement within the LPZ. A separate evaluation of both SPS SR-rod placements in a 2D sand tank injected with pure TCE tested the oxidant's ability to address soil-sorbed TCE. The rod atop the LPZ can mitigate dual permeability layers and creates a depletion zone at the high permeability zone to reduce contaminant transport from the LPZ. The rod within the LPZ reduces TCE lateral dispersion. The persistence and slow release of SPS in the LPZ suggest that the SPS SR-rod could effectively extend the time period of ISCO remediation of low-concentration TCE in the LPZ and the surrounding environment.

Technologies using liquid-transfer membranes, such as microfiltration, ultrafiltration, and reverse osmosis, have been widely applied in water and wastewater treatment. In the last few decades, gas-transfer membranes have been introduced in various fields to facilitate mass transfer, in which gaseous compounds permeate through membrane pores driven by gradients in chemical concentration or potential. A notable knowledge gap exists among researchers working on these emerging gas-transfer membranes as they approach this subject from different angles and areas of expertise (e.g., material science versus microbiology). This review explores the versatile applications of gas-transfer membranes in water and wastewater treatment, categorizing them into three primary types according to the function of membranes: water vapor transferring, gaseous reactant supplying, and gaseous compound extraction. For each type, the principles, evolution, and potential for further development were elaborated. Moreover, this review highlights the potential knowledge transfer between different fields, as insights from one type of gas-transfer membrane could potentially benefit another. Despite their technical innovations, these processes still face challenges in practical operation, such as membrane fouling and wetting. We advocate for research focusing on more practical and sustainable membranes and careful consideration of these emerging membrane technologies in specific scenarios. The current practicality and maturity of these emerging processes in water and wastewater treatment are described by the Technology Readiness Level (TRL) framework. Particularly, ongoing fundamental progress in membranes and engineering is expected to continue fueling the future development of these technologies.

Oxygen isotope ratios of O₂ are important tracers for assessing biological activity in biogeochemical processes in aquatic environments. In fact, changes in the ¹⁸O/¹⁶O and ¹⁷O/¹⁶O ratios of O₂ have been successfully implemented as measures for quantifying photosynthetic O₂ production and biological O₂ respiration. Despite evidence for light-dependent O₂ consumption in sunlit surface waters, however, photochemical O₂ loss processes have so far been neglected in the stable isotope-based evaluation of oxygen cycling. Here, we established the magnitude of the O isotope fractionation for abiotic photochemical O₂ elimination through formation of singlet O₂, ¹O₂, and the ensuing oxygenation and oxidation reactions with organic compounds through experiments with rose bengal as the ¹O₂ sensitizer and three different amino acids and furfuryl alcohol as chemical quenchers. Based on the kinetic analysis of light-dependent O₂ removal in the presence of different quenchers, we rationalize the observable O isotope fractionation of O₂ and the corresponding, apparent ¹⁸O kinetic isotope effects (¹⁸O-AKIE) with a pre-equilibrium model for the reversible formation of ¹O₂ and its irreversible oxygenation reactions with organic compounds. While ¹⁸O-AKIEs of oxygenation reactions amount to 1.03, the O isotope fractionation of O₂ decreased to unity with increasing ratio of the rates of oxygenation reaction of ¹O₂ vs ¹O₂ decay to ground state oxygen, ³O₂. Our findings imply that O isotope fractionation through photochemical O₂ consumption with isotope enrichment factors, ¹⁸O-ϵ, of up to -30‰ can match contributions from biological respiration at typical dissolved organic matter concentrations of lakes, rivers, and oceans and should, therefore, be included in future evaluations of biogeochemical O₂ cycling.

Many polycyclic aromatic hydrocarbons (PAHs) in the environment resulting from crude oil spills and the incomplete combustion of organic matter are highly toxic, mutagenic, or carcinogenic to microorganisms and humans. Bioremediation of PAHs using microorganisms that encode biodegradative genes is a promising approach for environmental PAH cleanup. However, the viability of exogenous microorganisms is often limited due to competition with the native microbial community. Instead of relying on the survival of one or a few species of bacteria, genetic bioaugmentation harnesses conjugative plasmids that spread functional genes to native microbes. In this study, two plasmid backbones that differ in copy number regulation, replication, and mobilization genes were engineered to contain a PAH dioxygenase gene (bphC) and conjugated to soil bacteria including Bacillus subtilis, Pseudomonas putida, and Acinetobacter sp., as well as a synthetic community assembled from these bacteria. Fitness effects of the plasmids in transconjugants significantly impacted the rates of conjugative transfer and biotransformation rates of a model PAH (2,3-dihydroxybiphenyl). A synergistic effect was observed in which synthetic communities bioaugmented with bphC had significantly higher PAH degradation rates than bacteria grown in monocultures. Finally, conjugation rates were significantly associated with the relative abundances of bacteria in synthetic communities, underscoring how fitness impacts of plasmids can shape the microbial community structure and function.

Human-impacted rivers often contain a complex mixture of organic micropollutants, including pesticides, pharmaceuticals and industrial compounds, along with their transformation products. Combining chemical target analysis for exposure with in vitro bioassays for effect assessment offers a holistic view of water quality. This study targeted the River Elbe in Central Europe, known for its anthropogenic pollution exposure, to obtain an inventory of micropollutant contamination during base flow and to identify hotspots of contamination. We identified tributaries as sources of chemicals activating the aryl hydrocarbon receptor quantified with the AhR-CALUX assay, including historically contaminated tributaries and a newly identified Czech tributary. Increased neurotoxicity, detected by differentiated SH-SY5Y neurons’ cytotoxicity and shortened neurite length, was noted in some Czech tributaries. A hotspot for chemicals activating the oxidative stress response in the AREc32 assay was found in the middle Elbe in Germany. An increase in oxidative stress inducing chemicals was observed in the lower Elbe. While effect-based trigger values (EBT) for oxidative stress response, xenobiotic metabolism and neurotoxicity were not exceeded, estrogenicity levels surpassed the EBT in 14% of surface water samples, posing a potential threat to fish reproduction. Target analysis of 713 chemicals resulted in the quantification of 487 micropollutants, of which 133 were active in at least one bioassay. Despite this large number of bioactive quantified chemicals, the mixture effects predicted by the concentrations of the quantified bioactive chemicals and their relative effect potency explained only 0.002–1.2% of the effects observed in the surface water extracts, highlighting a significant unknown fraction in the chemical mixtures. This case study established a baseline for understanding pollution dynamics and spatial variations in the Elbe River, offering a comprehensive view of potential chemical effects in the water and guiding further water quality monitoring in European rivers.