环境科学与技术最新文献

Biocontainment strategies, such as kill switches, have been developed to avoid the unintended proliferation of genetically engineered microbes (GEMs) intended for open-release environmental applications. However, the presence of GEM DNA after successful biocontainment presents new environmental risks and challenges for monitoring. In this study, we investigated whether biocontainment using a CRISPR-Cas9 kill switch, which causes double-strand breaks in target genes essential for GEM growth, could resolve this challenge in a model Escherichia coli GEM. Surprisingly, the escape rates of the GEM as determined by CRISPR-targeted gene abundances were as high as 10^-1.6 to 10^-1.0 in LB media, despite the escape rates measured by colony forming units (cfu) being only 10^-6.2 under the same condition. This discrepancy suggested that the CRISPR-Cas9 kill switch prevents colony growth while still leaving a large fraction of target genes intact for detection by molecular methods. Within 1 h after biocontainment, these target genes remained predominantly inside an intact cell membrane and were resistant to degradation by DNase, though degradation was observed in river water over multiple days. Overall, a detailed understanding of the impact of the biocontainment mechanism on both the GEM and its DNA is needed to minimize unintended environmental risks.

Gas-particle partitioning is critical for the evolution of secondary organic aerosols (SOA) in the atmosphere. SOA particles evaporate more slowly than expected at nearly size-independent rates, but the underlying mechanism remains controversial. Here, we apply kinetic multilayer modeling to simulate evaporation of α-pinene SOA, demonstrating that surface crust formation, emerging from accumulation of low-volatility compounds at the particle surface, leads to slow evaporation and reduced size dependence of the evaporation rate. While evaporation induced by decomposition of oligomers would naturally lead to size-independent evaporation rates, we observe and simulate nearly size-independent slow evaporation of polyethylene glycol mixture particles containing polymeric species that do not decompose, confirming the relevance of composition-dependent diffusivity for size-independent, slow evaporation. Slow evaporation of limonene SOA was also observed in environmental chamber experiments, and model simulations demonstrate strong surface crust formation with bulk diffusivity being depressed by up to 5 orders of magnitude compared to the inner bulk. We present experimental evidence using a surface-based mass spectrometry technique that shows that the particle surface becomes enriched in high molecular weight compounds upon evaporation of monomers. Our findings imply that viscous surface crusts may also limit the growth and chemical transformation of SOA particles, influencing their impacts on air quality and climate.

Biochar is increasingly promoted as a climate-smart amendment, yet its long-term effects on nutrient retention and greenhouse gas emissions in flooded rice systems remain poorly resolved. Here, we combine a 13 year field trial with graded straw biochar applications (0-22.5 t ha^-1 season^-1) and a 60 day anaerobic incubation of year-13 soils to investigate how mineral and microbial processes regulate soil organic carbon (SOC), phosphorus (P), and methane (CH₄) dynamics. Long-term biochar progressively depleted Fe oxides and enriched Ca phases, promoting the formation of Ca-bridged OC-mineral-P complexes that costabilize OC and P. Under prolonged anoxia, soils amended with high rates of biochar exhibited 2.5-3.2-fold slower Fe(III) reduction and delayed sulfate reduction, resulting in 53-80% lower CH₄ emissions and 60-71% P release relative to the no-biochar control. Nanoscale imaging and microbial profiling corroborated this mineral transition, showing a shift toward redox-resilient organo-mineral complexes and microbial communities associated with suppressed methanogenesis and enhanced nutrient retention. These findings provide long-term field-based evidence that biochar can simultaneously sustain crop productivity, enhance C and P retention, and mitigate CH₄ emissions in flooded rice agroecosystems. Our findings highlight biochar's potential as a scalable nature-based strategy for integrating nutrient management with climate mitigation in global rice production.

In this manuscript, we report niche differentiation among important groups of organisms involved in phosphorus and nitrogen cycling, and the interplay between relevant metabolic pathways carried out by these key organisms. We employed nanopore-based long-read and Illumina-based short-read sequencing techniques for metagenomics and metatranscriptomics, respectively, on samples collected from an integrated fixed film activated sludge (IFAS) bioreactor run in the conventional A²O mode under low dissolved oxygen (DO) conditions. Among the recovered metagenome-assembled genomes (MAGs), >90 MAGs from each community were high-quality, including 39 and 30 MAGs that were close-circularized, from the floc and biofilm communities, respectively, with no or minimal contamination. Some Candidatus Accumulibacter strains encoded for either full or partial denitrification. Ca. Accumulibacter were very efficient in aerobic and anoxic inorganic phosphorus (Pi) uptake, while the second highly enriched Ca. Accumulibacter was as competitive for denitrification metabolism. The potential of nitrous oxide (N₂O) emissions in both the floc and biofilm communities was nearly 20 times higher in the aerobic zone than in the anoxic zone. As opposed to our initial hypothesis that slow growers will mostly reside in biofilms, the expression of ammonium monooxygenase (amoABC) was higher in flocs than in biofilm communities.

Coal-derived fine particles (FPs, <1 μm) are highly reactive and compositionally heterogeneous, yet their toxicity mechanisms remain poorly understood. Using single-particle ICP-TOF-MS, we profiled metal(loid)s in FPs from ten representative coal-fired power plants across China. Quantification showed that 57 ± 9% of FPs were multimetal(loid) (mmFPs), 84 ± 9% of which were Al/Si/Fe-rich and carried most toxic metals. Toxicology assays identified that Fe-rich FPs and associated toxic metals (Cr, Mn, and Pb) could be important contributors to cellular injury, accompanied by oxidative stress and in vitro transcriptomic enrichment of ferroptosis, inflammation, and small-cell lung cancer-related signaling pathways. As an easily separable Fe-rich FP fraction, magnetic FPs comprised only 15.8% of the mass yet contributed 74.2% of oxidative stress and 88.5% of the cytotoxicity. In vitro and in vivo experiments revealed their transferrin receptor (TFRC)-mediated uptake induced ferroptosis and pulmonary injury, which could be attenuated by a TFRC inhibitor. These results suggest Fe-rich FPs (together with associated toxic metals) as the significant contributor of coal-combustion FP toxicity and provide the mechanistic evidence pinpointing Fe-rich particles as key determinants.

Singlet oxygen (¹O₂) is an important reactive intermediate in aquatic photochemical reactions, altering the fate and transformation of pollutants. Past work has primarily quantified ¹O₂ generation in aquatic systems using the chemical probe furfuryl alcohol (FFA). An alternative method to quantify ¹O₂ is to directly observe ¹O₂ through its phosphorescence emission. While this method is receiving growing interest, there has yet to be a direct comparison of measured ¹O₂ generation efficiencies (i.e., quantum yields) between the FFA and ¹O₂ phosphorescence methods. In this study, we compared the ¹O₂ quantum yields (Φ_Δ) between these two methods for a broad set of samples, including small molecule sensitizers, dissolved organic matter (DOM) isolates, and pyrogenic DOM (PyDOM). FFA and ¹O₂ phosphorescence methods yielded significantly different Φ_Δ values for many small molecule sensitizers and DOM/PyDOM samples. For DOM/PyDOM, the ¹O₂ phosphorescence method yielded 1.4 - 3.8 times higher Φ_Δ. We additionally explored potential FFA-mediated triplet excited state quenching processes using laser spectroscopy. While we observed that FFA effectively quenched and/or chemically reacted with triplets of small molecule sensitizers, we observed minimal quenching of the triplet excited state DOM/PyDOM by FFA. This suggests that for DOM/PyDOM, FFA-triplet reactions are not major side reactions in FFA-based ¹O₂ measurements at 365 nm. Results from this study illuminate the potential issues of FFA interacting with sensitizer triplet excited states and advance the understanding of ¹O₂ phosphorescence-based Φ_Δ measurements.