环境科学与技术最新文献

Molybdenum (Mo) is an essential nutrient for almost all organisms. However, at high concentrations, it can be toxic to animals and plants. This study investigated the interactions of Mo(VI) with iron oxyhydroxides during ferrihydrite bioreduction in the presence of Fe(III)-reducing Geobacter sulfurreducens. Here, we showed that Mo concentration controlled ferrihydrite phase transformation, leading to Mo release. With the biotic reduction of ferrihydrite and Fe(II) production, Mo(VI) reduction and Mo(IV)O₂ formation were observed for the first time, which further immobilized Mo after surface adsorption of Mo(VI). At low Mo levels (Mo/Fe molar ratios of 1-2%), sufficient Fe(II) adsorption onto ferrihydrite resulted in its transformation into magnetite nanoparticles (>80%, ∼25 nm), which catalyzed the reduction of Mo(VI) to form Mo(IV)O₂ and immobilized Mo. Contrastingly, at high Mo concentrations (Mo/Fe molar ratios of 5-10%), Mo(VI)O₄^2- adsorption onto ferrihydrite limited Fe(II) adsorption; subsequently, less magnetite (<8-12%) formed while more goethite (∼30-50%, width and length >15 and 100 nm, respectively) and siderite (∼20-30%, width and length >100 and 200 nm, respectively) with larger particle sizes formed instead, causing Mo(VI) release due to lower Mo adsorption. This study provides a comprehensive understanding of the interaction mechanisms among Geobacter sulfurreducens, Mo(VI), and iron oxyhydroxides, enabling predictions and controls of long-term Mo mobility and Fe mineral transformation under a variety of biogeochemical scenarios.

Nitrogen oxides (NO_x), comprised of nitric oxide (NO) and nitrogen dioxide (NO₂), play a crucial role in the global nitrogen cycle, but the oceanic occurrence remained unclear. Here, we show an integrated underway observation of oceanic and atmospheric NO and NO₂ from the coastal seas to the open ocean in the northwestern Pacific Ocean (NWPO). The concentrations of NO and NO₂ showed similar distribution patterns that the coastal seas with rich nitrogen nutrients showed higher levels, like the Yellow Sea (7.6 and 19.9 pmol L^-1) and the East China Sea (11.8 and 23.3 pmol L^-1), while the oligotrophic sea and open ocean showed decreased levels, like the South China Sea (2.4 pmol L^-1 and below the detection limit, LOD) and the NWPO (3.5 pmol L^-1 and below the LOD). Apart from nitrogen nutrients, sea surface temperature might be another important influencing factor on the NO and NO₂ distribution. In the surface water (<10 m), photoproduction was a major NO source compared to the microbial process, while in the mixed layer, the microbial process played a more critical role. The saturation values showed that the sea was a net source of atmospheric NO but was a net sink of NO₂.

Polycyclic aromatic hydrocarbons (PAHs) are common environmental pollutants that originate from the incomplete combustion of organic materials. We investigated the clastogenicity and mutagenicity of benzo[b]fluoranthene (BbF), one of 16 priority PAHs, in MutaMouse males after a 28 day oral exposure. BbF causes robust dose-dependent increases in micronucleus frequency in peripheral blood, indicative of chromosome damage. Duplex sequencing (DS), an error-corrected sequencing technology, reveals that BbF induces dose-dependent increases in mutation frequencies in bone marrow (BM) and liver. Mutagenicity is increased in intergenic relative to genic regions, suggesting a role for transcription-coupled repair of BbF-induced DNA damage. At higher doses, the maximum mutagenic response to BbF is higher in liver, which has a lower mitotic index but higher metabolic capacity than BM; however, mutagenic potency is comparable between the two tissues. BbF induces primarily C:G > A:T mutations, followed by C:G > T:A and C:G > G:C, indicating that BbF metabolites mainly target guanines and cytosines. The mutation spectrum of BbF correlates with cancer mutational signatures associated with tobacco exposure, supporting its contribution to the carcinogenicity of combustion-derived PAHs in humans. Overall, BbF's mutagenic effects are similar to benzo[a]pyrene, a well-studied mutagenic PAH. Our work showcases the utility of DS for effective mutagenicity assessment of environmental pollutants.

Anaerobic ammonium oxidation (anammox) is efficient and cost-effective for treating high-strength ammonia wastewater, but the organics in wastewater will affect its stability. To address this challenge, it is crucial to gain a deep understanding of the inhibitory effects and mechanisms of organics stress on anammox bacteria. The review provided a comprehensive classification of organics and evaluated their specific effects on the anammox system according to their respective characteristics. Based on the micro to macro perspective, the "molecule-cell-ecology" inhibitory mechanism of organics on anammox bacteria was proposed. The molecular observation systematically summarized the binding process and action sites of organics with anammox bacteria. At the cellular observation, the mechanisms of organics effects on extracellular polymeric substances, membranes, and anammoxosome of anammox bacteria were also expounded. At the ecological observation, the dynamic changes in coexisting populations and their role in organics transformation were further discussed. Further revelations on response mechanisms and inhibition mitigation strategies were proposed to broaden the applicability of anammox systems for organic wastewater. This review offered a multidimensional understanding of the organics inhibitory mechanism of anammox bacteria and provided a theoretical foundation for anammox systems.

Nitrogen dioxide (NO₂) has decreased by ∼33% across over 1200 monitoring sites in China during 2015-2023, following a series of clean air policies. However, most of these sites are located in or near cities, leading to uncertainties in NO₂ trends beyond urban regions due to limited observations. Here, we used satellite measurements to examine the differences in NO₂ trends between urban and rural China. In urban areas, NO₂ columns decreased by 4.0% per annum (a^-1) during summer 2011-2023, consistent with bottom-up anthropogenic emission inventory and in situ measurements. In contrast, rural NO₂ columns showed a slower than expected reduction (-2.6 to -0.0% a^-1) during the same period. Model simulations with updates in the soil reactive oxidized nitrogen (N_r) scheme indicated that increasing soil N_r emissions can be an important factor contributing to the observed slow NO₂ decrease in rural areas. This unregulated source increased summertime pollutant levels, partially offsetting the national efforts to mitigate NO₂, ozone (O₃), and particulate nitrate (NO₃^-) levels by 20.9%, 15.4%, and 4.7%, respectively, from 2011 to 2020. In the agriculture-intensive North China Plain, the increase in soil N_r emissions offset 46.6% of the NO₂ reductions achieved by clean air policies. Our results highlight the increasing significance of soil emissions and the need to control them in future air-quality policies.