Understanding the fate and transport of contaminants of emerging concern (CEC) in natural and engineered systems is important to improve treatment. Adsorbents can retain and remove CEC; however, the widespread presence of natural organic matter (NOM) complicates such adsorption processes. The functional groups present in ionizable CEC, NOM, and adsorbent influence charge characteristics and adsorption affinity, with their effects varying according to pH conditions. Hydrophobic and electrostatic interactions are considered main driving forces. However, these two interactions cannot fully explain 1) the binding of ionizable CEC to adsorbents at specific environmental pHs and 2) the self-aggregation of NOM molecules to supramolecular aggregates. Charge-assisted hydrogen bond (CAHB) is a three-center-four-electron, low-barrier hydrogen bond with considerable covalent nature. Pignatello J.J., his contemporaries, and his colleagues demonstrated that the formation of CAHBs 1) facilitates adsorption characteristics at CAHB-favorable pHs, 2) increases pH by taking up protons from water, 3) shifts pKa upward, 4) contributes to homoconjugation of carboxylates, 5) affects surface charge of dissolved organic matter aggregates, and 6) holds NOM molecules together. This review article serves as a summary of CAHB papers with significant environmental implications, and as a critical evaluation of how CAHB influences the fate and transport of representative, ionizable CEC, such as (aged) microplastics and nanoplastics, per- and polyfluoroalkyl substances (PFAS), pharmaceuticals, pesticides, etc. This article also discusses how CAHB plays a role in the structure of NOM. Discussions herein will inform the community about the activity, reactivity, and treatability of ionizable CEC.

Verticillium wilt, caused by Verticillium dahliae, is a devastating disease that severely threatens cotton production worldwide. The long-term survival of the pathogen in soil and the limited availability of resistant cultivars make effective control strategies challenging. Although the fungal cross-kingdom RNA VdsR-1 has been reported to delay floral transition and prolong vegetative growth, the underlying plant regulatory mechanisms remain largely unclear. Here, we show that the transcription factor AtTOE1, a target of ath-miR172b-3p, displays altered expression in response to changes in ath-miR172b-3p levels during V. dahliae inoculation, coinciding with coordinated changes in plant immune-related and developmental responses. Increased AtTOE1 expression is correlated with enhanced disease resistance, reduced pathogen colonization, and delayed floral transition. Furthermore, our results indicate that the VdsR-1/AtSPL13A module is associated with modulation of AtTOE1 expression via ath-miR172b-3p, suggesting the involvement of a cross-kingdom RNA-related regulatory framework linking plant immunity and development. Notably, this regulatory relationship is also observed in cotton, indicating evolutionary conservation across plant species. Together, our findings highlight TOE1 as a potential integrator of defense and growth-related processes during pathogen challenge and provide insights that may inform strategies to improve resistance to V. dahliae in cotton and other crops.

Pyrolysis of tea waste to produce biochar (BC) for soil modification offers a promising reuse strategy. However, the short-term application of BC can enhance soil organic carbon (SOC) mineralization, and the economic viability of this BC across its lifecycle (from production to field application) remains unclear. In this study, Fe-modified tea waste BC (FBC) was produced at 300-900 °C to enhance SOC sequestration over 180 days, alongside an evaluation of their economic benefits. Compared with unmodified BC, FBC produced at 600 °C (FBC600) and 900 °C (FBC900) significantly increased SOC content, with increments of 1770-1800 mg/kg at 15-60 days and 660-830 mg/kg at 60-180 days. This enhancement was attributed to two factors: first, the highly aromatic structures of FBC600 and FBC900 were associated with the abundance of putative autotrophic taxa, with Fe potentially facilitating fresh SOC synthesis by these bacteria; second, dissolved organic C (DOC) decreased by 417-436 mg/kg in FBC-amended soils, which was approximately twice the cumulative mineralized C, indicating that enhanced DOC adsorption further contributed to SOC sequestration. Spectral analysis suggested preferential adsorption of small aromatic protein-like molecules in FBC600- and FBC900-amended soils. Life cycle assessment revealed significant economic benefits for both FBC600 and FBC900, with overall revenues of 674.63 USD/ton and 721.04 USD/ton, respectively, alongside net CO2 emission reductions of 1432.12 kg/ton and 1098.16 kg/ton. This study highlights a valuable approach for tea waste reuse that offers both economic advantages and mitigation of the short-term SOC mineralization commonly induced by BC application.

Widespread adoption of cover crops has profoundly altered soil physical properties and crop production systems. Soil aggregates are key indicators of soil physical quality, yet it remains unclear how cover crops regulate soil aggregate properties and whether these changes can predict cover crop-induced variations in crop productivity. By synthesizing 230 field studies worldwide, we showed that cover crops significantly improved soil water-stable aggregates (WSA) by 20.8%, mean weight diameter (MWD) by 15.1%, and large macro-aggregates (>2 mm) by 23.2%, while significantly reducing small macro-aggregates (0.25-2 mm) by -10.5% and micro-aggregates (<0.25 mm) by -16.0%. Cover crops also increased crop productivity by 32.6%. Model selection analyses revealed that soil texture were the top predictors for WSA. In addition, experimental duration (optimal at 15 yr) was the sole key predictor for MWD, and large macro-aggregates in the topsoil increased with cover crops. Notably, there was no clear relationship between changes in soil aggregate properties and crop productivity. Instead, cover crop type was the dominant predictor of crop productivity responses, with leguminous cover crops enhancing productivity by 53.4%-a greater effect than non-leguminous cover crops (15.3% increase). Altogether, these findings highlight the need for considering the roles of key regulatory factors in regulating soil-crop interactions under cover crop cultivation to better understand the linkages between soil physical properties and sustainable crop production.

IntroductionStraw return exerts a profound impact on soil fertility, with particularly critical implications for soil carbon (C) pools. Soil hydrolytic C-degrading extracellular enzyme activities (Hy-EEAs) play a central role in soil C cycling. However, the effects of straw return on Hy-EEAs, below-ground C dynamics, and the underlying regulatory mechanisms have not been fully elucidated.MethodsIn this study, we evaluated the effects of straw incorporation on Hy-EEAs and below-ground C, as well as their potential relationships, by synthesizing 211 observations from 68 published field studies worldwide.ResultsOn average, straw return significantly enhanced Hy-EEAs by 25% but had no effect on β-xylosidase. Straw return significantly increased dissolved organic carbon, easily oxidizable carbon, light fraction organic carbon, particulate organic carbon, microbial biomass carbon, and soil organic carbon by 27, 24, 51, 34, 31, and 20%, respectively, compared to the no-straw-return treatment. The effect of straw return on Hy-EEAs decreased with increasing experiment duration (≥ 10 years). Straw return effects on Hy-EEAs increased with the incorporation of straw. The response ratios (lnR) of microbial biomass C content and soil organic carbon (SOC) storage to straw return were positively correlated with the lnR of Hy-EEAs; however, no clear relationships were found between the lnR of soil dissolved organic C (DOC), easily oxidizable C (EOC), light fraction organic C (LFOC), and particulate organic C (POC) and the lnR of Hy-EEAs.DiscussionThese results suggest that straw return stimulation of Hy-EEAs exhibited a key role in regulating below-ground C dynamics. Future biogeochemistry models could incorporate the observed relationships in this study between the soil C pool and Hy-EEAs, which can improve model predictions of C in soils under straw return in agricultural systems.

Iron (Fe) (oxyhydr)oxides are crucial for the storage and persistence of soil organic carbon (SOC). Although secondary metabolites such as flavonoids can alter Fe transformation and cycling, the mechanism by which these compounds influence the ability of Fe (oxyhydr)oxides to mediate SOC preservation remains unclear. Here, we combined a well-controlled field trial under different fertilization regimes with targeted incubation experiments to study how flavonoids drive the formation of organo-Fe (oxyhydr)oxide complexes in paddy soils. Compared with the control treatment, manure-amended soils exhibited a 26% higher SOC content, which correlated strongly and positively with short-range-ordered minerals (SROs) levels. These soils also contained higher concentrations of flavonoids and SROs, both of which were positively correlated with phenoloxidase activity. The incubation experiments showed that quercetin (a key representative flavonoid) promoted the formation of 2-line ferrihydrite (Fh) particles (~0.27 nm lattice spacing) and suppressed Fh crystallinity by co-precipitation, thereby enhancing SROs-Fh accumulation. By enlarging the specific surface area of pre-existing Fh by 40%, quercetin further amplified its sorption capacity. Results of Fourier-transform infrared spectroscopy (FTIR) revealed that v(C-O-C)/v(C-O) groups preferentially coordinated with Fe-O moieties, reorganizing organic-Fe associations that accounted for 58% of Fe-bound C in the quercetin-treated adsorption system. Collectively, our results uncover a new mechanism by which such as quercetin could enhance SOC sequestration by modulating Fe-oxides transformation, and underscore the pivotal role of ternary interactions among the flavonoids, iron oxides, and organic carbon during this process. This finding provides a new insight for explaining how the flavonoid-mediated Fe (oxyhydr)oxides enhance soil carbon storage in paddy soils, and highlights the potential of applying different agricultural strategies to increase soil carbon stocks.

Owing to the extensive use of solid fuels (e.g., coal, charcoal, and biomass), massive smoke dissolved organic matters (SDOMs) are produced. They are not only deteriorate atmosphere, but eventually deposit into water and soil environments, and interact with pollutants (e.g., heavy metals (HMs)), further altering the environmental fate and risks of HMs. However, the distinct molecular complexing mechanisms of SDOMs from various solid fuels combustion toward HMs still remains unknown. This study investigated the distinct molecular complexing mechanisms with Cu(II) and Cd(II)) (0-100 mu mol/L) for SDOMs (10 mg-C/L) from coal, charcoal, and biomass based on Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS), two dimensional fluorescence excitation-emission matrix (EEM) and Fourier transform infrared spectroscopy (FTIR). Notably, various SDOMs exhibited evidently different molecular complexing characteristics with HMs. Fluorescence quenching/enhancing ratio showed that humic-like matters in biomass SDOMs (28.7-51 %) were significantly combined with HMs, and polyphenols in coal and charcoal SDOMs (7.3-38.4 %) were significantly combined with HMs. Coal-derived SDOM was rich in CHOS compounds (-SO3H group) which played a dominant role in the binding capacity toward HMs, with the binding sequence preceded CHON and CHONP compounds. Charcoal-derived SDOM featured N-containing compounds (-NH2 group), which formed H-bonds with S-/P-containing compounds and competed against HMs binding, leading highly aromatic CHO compounds to preferentially interact with HMs via cation-pi effect. Biomass-derived SDOMs possessing the maximum CHO compounds which provided more multi-oxygen coordination sites for HMs complexing, but CHON, CHOS and CHOP compounds interacting with HMs preceded CHO compounds. The complexing order of functional groups followed phenol-O->S=O/P-O/-NH > aromatic C=C > -OH. This study elucidated distinct molecular mechanisms of various SDOMs binding with HMs according to their molecular compositions and functional group types. The results are essential to understanding and controlling the geochemistry process and environmental fate of various solid fuels-derived SDOM-HMs complexes in surface environments.

Owing to the worldwide wildfire, the environmental process of polycyclic aromatic hydrocarbons (PAHs) in soil is inevitably affected by the co-deposition of biomass-burning-smoke dissolved organic matters (BBS-DOMs), which have significantly different molecular characteristics from soil-DOMs. However, to date, the molecular-level interactions among PAHs, BBS-DOMs, and soil remain a significant knowledge gap. Hence, this study used FT-ICR-MS and multi-spectrometers to comprehensively investigate their molecular-level interactions. This study revealed that the binding coefficient, Kd, of PAHs on BBS-DOMs (2.36 × 104∼7.40 × 104 L/kg) was about 100 times that for PAHs binding onto soils (2.07 × 102∼8.39 × 102 L/kg), owing to the abundant aromatic CHO, CHON, and CHONP molecules of BBS-DOMs, which were responsible for this stronger interaction. Additionally, the spectral index (SUVA254) of BBS-DOMs could be effectively used to predict the sorption capacities of PAHs onto DOMs, with the prediction models of log10Kd = 0.0946SUVA254+3.969 and log10Kd = 0.0991SUVA254+4.006 (r > 0.95, p < 0.01) for phenanthrene and pyrene, respectively. Interestingly, though BBS-DOMs input (0.1 wt%) significantly increased the dissolved organic carbon content of soil, their input significantly increased rather than decreased the sorption of PAHs onto soils, with Kd increased by 10∼35%. The FT-ICR-MS and other spectral results revealed that the small phenolic structure-containing molecules (e.g., polyphenols, lignin, and tannin) in BBS-DOMs were preferentially bound to soil. These preferentially binding molecules enhanced the interaction between PAHs and soils by the additional molecular bridging effect of π-π electron donor-acceptor interaction. These results give crucial evidence to understand the environmental fate and risk of BBS-DOMs and PAHs co-deposition into soils after a wildfire.

Due to their large specific surface area, variable surface charge, and abundant reactive functional groups, soil colloids are important "carriers" for the migration of HMs (heavy metals) in the soil. This study systematically investigates the migration-transformation mechanisms of colloidal As, Cd, Tl and their driving factors in paddy soils of the Karst region in southwest China. Results show that colloidal Fe and OM are the primary environmental factors influencing the formation and distribution of these three colloidal heavy metals, with significant positive correlations (correlation coefficients r2 = 0.56-0.79). TEM-EDS and XRD analyses confirm that As/Cd are closely associated with Fe oxides (e.g., magnetite, goethite) at the nanoscale. AF4-UV-ICP-MS technology reveals that colloidal HMs primarily occur in the 100-350 nm size range, and anthropogenic activities in artisanal smelting areas promote the formation of smaller-sized colloids (20-350 nm), enhancing their migration potential. Metagenomic analysis indicates that N/S metabolic genes (e.g., narA, cysN) are significantly correlated with colloidal HMs concentrations, and microbial metabolites affect the binding of HMs to soil colloids. Traditional assessments overlook the high mobility and stability of colloidal HMs (e.g., 100-350 nm), leading to underestimation of potential risks to paddy ecosystems and adjacent water bodies. Future biogeochemical research should prioritize colloid - and nanoparticle - bound HMs to improve risk assessment and remediation strategies.

Iron (Fe) is an essential micronutrient for plant growth and development. Rhizosphere microorganisms play crucial roles in plant Fe nutrition, yet the underlying mechanisms remain largely unknown. Here, we assessed the effect of the volatile organic compounds (VOCs) produced by Bacillus velezensis SQR9 on Fe uptake in Arabidopsis, elucidated the underlying mechanism using genetic and biochemical approaches, and identified the active components of SQR9 VOCs. Our results showed that plants exhibited enhanced Fe uptake, chlorophyll content, fresh weight, and root development when exposed to SQR9 VOCs under Fe-limited conditions. The reduction-based Fe uptake genes in Arabidopsis, encompassing the Fe-deficiency-induced transcription factor FIT, the ferric-chelate reductase FRO2, and the ferrous Fe transporter IRT1, were significantly upregulated by SQR9 VOCs. The deletion of these genes diminished the enhancing effect of SQR9 VOCs on plant Fe uptake. Meanwhile, this enhancement was found to be dependent on the accumulation of nitric oxide (NO) in the roots. Among the 23 VOCs in SQR9, we identified pentadecane as a key active compound that mediates NO signalling and promotes plant Fe uptake under Fe-limited conditions. The effective working concentration range for gaseous pentadecane was determined to be approximately 128.3 to 513.2 ng L-1. In conclusion, our findings illuminate the mechanism by which SQR9 VOCs promote plant Fe uptake and highlight the application potential of SQR9 as a plant growth-promoting rhizobacterium (PGPR) for Fe biofortification of crops.

The deposition of biomass-burning smoke-derived dissolved organic matters (BBS-DOMs) poses challenges to water treatment in wildfire areas. This study innovatively investigated the molecular binding between BBS-DOMs and clays (kaolinite and montmorillonite) and its interaction with tetracycline adsorption using Fourier transform-ion cyclotron resonance-mass spectrometry and various other spectral analyses. Herein, the amine-containing molecules (CHON, CHONP, and CHONSP compounds) in BBS-DOMs were the dominant adsorbed components on kaolinite with limited binding sites (specific surface area (SSA): 17.9 m(2)/g; pH(pzc): 3.8) by forming strong hydrogen-bonds and electrostatic attraction. Conversely, montmorillonite exhibits sufficient binding sites (SSA: 63.5 m(2)/g; pH(pzc): 2.7) to allow simultaneous interaction with both amine-containing and polyphenolic molecules (CHO compounds) in BBS-DOMs. Intriguingly, with increasing tetracycline concentration, the strong-enhancing effect of BBS-DOMs (<= 1.0 mg/L tetracycline) transformed to weak-enhancing/inhibiting effects (>= 10.0 mg/L tetracycline) on tetracycline adsorption. This transition is due to the shift in primary compositions of BBS-DOMs binding with clays from large aromatic molecules (humic-like molecules) (the average proportion of dissolved state increased from 13.5 % to 40.0 %) to polyphenol- and aromatic amides/(oligo)peptide-like molecules (the average proportion of dissolved state decreased from 77.5 % to 38.8 %). The results suggested that at the environment-relevant concentration of tetracycline (<1.0 mg/L), BBS-DOMs could significantly enhance its adsorption onto clays. Furthermore, within the pH range of 3.0-10.0, the enhancing-effect of BBS-DOMs was maximum at pH 4.0. These results provided a crucial data-support for elucidating the molecular mechanism of BBS-DOMs-affected adsorption of tetracycline onto clays, and contribute to optimizing the water treatment processes in wildfire areas by clays application.

Phosphorus (P), a non-renewable resource essential for sustaining life, faces increasing environmental losses from agricultural systems. However, the effects of flavonoid-induced iron oxide on soil P behavior remain poorly understood, particularly in paddy soils. Here, we conducted a 7-year field trial under four fertilization regimes combined with laboratory incubations to reveal how flavonoid-modified iron oxides regulate P at the molecular scale. Results showed that manure-applied (NPKM) soils increased the content of flavonoids by 48.7% and short-range-order minerals (SROs) by 8.7% compared with chemically fertilized (NPK) soils. Through interfacial reactions between Fe-P minerals and quercetin, the formation of 2-line ferrihydrite was promoted by quercetin with an interplanar distance of 0.26/0.30 nm at pH 7. It was found that 14.25% of the Fe-phosphate group was incorporated at a quercetin concentration of 1 mM, and Fe oxides acted as the "core" for retaining P in these complexes. Further, phosphate release was observed during the interfacial reaction with increasing quercetin concentrations, suggesting a potential trade-off between P fixation and release. Despite these benefits, NPKM soils exhibited the highest degree of phosphorus saturation (DPS) (18.61%) and the lowest soil phosphorus storage capacity (1.70 mg kg-1), indicating an elevated risk of P loss. A significant positive correlation was identified among SROs, flavonoids, and DPS in paddy soils. Collectively, our findings demonstrate that flavonoids can modify the morphology of Fe oxides in paddy soils, thereby enhancing P fixation. This presents a promising approach for mitigating diffuse P pollution and promoting sustainable agriculture.

Plant-beneficial microorganisms are frequently reported to enhance iron (Fe) nutrition in plants, yet the precise underlying mechanisms remain largely unknown. Although both bacterial siderophore production and biofilm formation are beneficial for microbial plant growth promotion, these two bacterial traits have been studied separately. Here, we reveal a strong coupling between these two bacterial traits in enhancing plant Fe uptake using the biofilm-forming rhizobacterium Bacillus velezensis SQR9. We demonstrate that SQR9 biofilms accumulate Fe on plant roots and serve as an Fe reservoir. Crucially, the siderophore bacillibactin enables biofilm Fe accumulation from the environment, while simultaneously stimulating Fe acquisition mechanisms in plants. Field experiments confirmed the ability of SQR9 to boost crop yields in alkaline soils, highlighting its potential for improving iron-limiting plant performance. Our findings emphasize a key role of rhizobacterial siderophores and biofilms in Fe uptake and offer mechanistic insights for microbial biofortification strategies against Fe deficiency in crops.

Antimicrobial peptides (AMPs) are promising candidates to address the global antimicrobial resistance crisis, yet their traditional design remains labor-intensive and inefficient. Here, we developed BroadAMP-GPT, an integrated computational-experimental framework that combines AI-driven generation, multi-tiered screening, and experimental validation to rapidly discover potent AMPs with broad-spectrum activity. Using this platform, 57% of AI-generated candidates exhibited potent efficacy against ESKAPE pathogens - key culprits of multidrug-resistant infections. An outstanding candidate, AMP_S13, demonstrated exceptional stability under diverse physiological conditions, including extreme pH (2-10), proteolytic exposure, and elevated temperatures, while maintaining minimal cytotoxicity and low hemolytic activity. AMP_S13 also showed robust in vivo efficacy, reducing mortality in Galleria mellonella infection model and accelerating wound healing in a murine MRSA skin infection model. These results validate BroadAMP-GPT as a transformative tool for accelerating the discovery of stable, broad-spectrum and low-toxicity AMPs, offering a scalable strategy to address the urgent threat of multidrug-resistant pathogens.

The use of RNA interference (RNAi) technology to control pests is explored by researchers globally. Even though RNA is a new class of pest control compound unlike conventional chemical pesticides, the evolution of pest resistance needs to be considered. Here, we first investigate RNAi-based biopesticide resistance of Fusarium asiaticum, which is responsible for devastating diseases of plants, for example, Fusarium head blight. Five resistant strains were isolated from 500 strains that treated with UV-mutagenesis. The mutation common to all of the five resistant mutants occurred in the gene encoding Dicer2 (point mutations at codon 1005 and 1007), which were under strong purifying selection pressure. To confirm whether the mutations in Dicer2 confer resistance to RNAi, we exchanged the Dicer2 locus between the sensitive strain and the resistant strain by homologous double exchange. The transformed mutants, Dicer2R1005D and Dicer2E1007H, exhibited resistance to dsRNA in vitro. Further study showed that mutations of R1005D and E1007H affected the intramolecular interactions of Dicer2, resulting in the dysfunction of RNase III domain of Dicer2. The amount of sRNAs produced by Dicer2R1005D and Dicer2E1007H was extremely reduced along with variation of sRNA length. Together, these findings revealed a new potential mechanism of RNAi resistance and provided insight into RNAi-related biopesticide deployment for fungal control.

While low molecular weight organic acids (LMWOAs) are commonly used to enhance the dissolution and bioavailability of polycyclic aromatic hydrocarbons (PAHs) in soils, a comprehensive mechanistic framework is lacking. In this study, four representative organic acids (formic, acetic, citric, and oxalic acids) were systematically evaluated to their efficacy in promoting PAH desorption from a long-term contaminated soil, with particular emphasis on elucidating the governing mechanisms and environmental implications. The results demonstrated that these organic acids increased the release of PAHs and dissolved organic carbon (DOC) by 1.17-1.90 fold and 1.12-17.39 fold, respectively, compared to the NaCl control. The ratio of desorbed PAHs per unit of DOC followed the order: acetic acid > formic acid ≫ citric acid ≥ oxalic acid. Citric and oxalic acids solubilized significantly more Fe3+ and Al3+ (bridging cations between minerals and soil organic matter, SOM) than formic and acetic acids, thereby releasing larger amounts of dissolved organic matter (DOM) with relatively high molecular weights. However, additional solubilization of Fe3+ and Al3+ had negligible effects of on PAH desorption. The dominant mechanisms governing PAH desorption included Ca2+ dissolution and the disruption of negative charge-assisted hydrogen bonds, (-)CAHB, within SOM (including both intermolecular and intramolecular linkages). From the perspective of maintaining soil fertility and mitigating global climate change, formic/acetic acids outperform citric/oxalic acids in PAH desorption. The key advantage is that they release less biodegradable DOM, which reduces the risk of increased CO2 emissions and helps preserve SOM.

Polycyclic aromatic hydrocarbons (PAHs) in polluted soil poses environmental risks and inhibits soil safe use. Although biochar (BC) and phytoremediation are frequently applied to enhance PAH dissipation in soil, their combined effect on remediation, particularly in naturally contaminated field soils, remains poorly understood. Hence, a five-month pot experiment was conducted using three distinct types of naturally field-contaminated soils—Calcareous soil, Phaeozems, and Haplic Luvisol—along with ryegrass (Lolium perenne L.) and cedar branch-derived BC. The objective was to evaluate the effect of BC on phytoremediation and bioavailability of PAHs in these soils. Results indicated that BC significantly increased ryegrass biomass in all soils (p < 0.01), but the increase was least in Phaeozems with highest organic carbon content. BC also significantly reduced total Σ15PAHs in all soils, though this effect become negligible when combined with ryegrass. BC decreased available Σ15PAHs in Calcareous soil but not in other soils. When combined with ryegrass, BC significantly decreased available Σ15PAHs in Calcareous soil and Phaeozems but increased in Haplic Luvisol. BC generally reduced PAH accumulation in ryegrass roots and leaves (p < 0.05) except for roots in Phaeozems. It decreased the translocation factor (TF) value of total Σ15PAHs in Calcareous soil and Phaeozems but increased it in Haplic Luvisol (p < 0.05). Thus, incorporating BC into soils with diverse physico-chemical properties exerts varied effects on PAH bioavailability and translocation in plants. Tailoring BC use to soil properties is crucial for effective remediation.

Biomass-pyrogenic smoke dissolved organic matter (BPS-DOM) can co-deposit with polycyclic aromatic hydrocarbons (PAHs), thereby altering their environmental behavior and fate in surface environments. However, the heterogeneous molecular characteristics of BPS-DOM binding with PAHs remain unclear. This study systematically elucidates the binding characteristics of PAHs (phenanthrene and pyrene), with various molecular compositions in BPS-DOM, utilizing FT-ICR MS and fluorescence variation analysis. CHO compounds in BPS-DOM, characterized by high aromaticity and abundant CO bonds, significantly enhance PAHs binding by promoting π-π electron donor-acceptor interactions. In contrast, CHON compounds with higher aliphaticity inhibit pyrene binding by competing for binding sites on BPS-DOM. Furthermore, the binding sequence of different fluorescent molecules follows the order of CHO→CHOS→CHON for phenanthrene and CHO→CHON→CHOS for pyrene. This was primarily due to the larger conjugated aromatic structures of CHO compounds, which provide stronger π-π interaction sites for PAHs binding. The difference in binding sequences between phenanthrene and pyrene is primarily attributed to phenanthrene's reliance on π-π electron donor-acceptor interactions induced by -SO and -N = O, while pyrene binding depended on π-π interactions driven by larger conjugated aromatic structures. These results provide an important theoretical foundation for further understanding the molecular-level interactions between BPS-DOM and PAHs.

Polycyclic aromatic hydrocarbons (PAHs) can form nonextractable residues in soil, significantly impacting their environmental behavior and fate. Although considerable research has been conducted on the formation of nonextractable residues of PAHs in soil through spiked experiments using representative PAH compounds, limited research has been given to the nonextractable residues of 16 priority PAHs in historically polluted soils. This study aimed to investigate the concentrations and compositions of the nonextractable residues for parent PAHs in five historically polluted soils and their biodegradation in three soils. The results indicated that the average contents of total nonextractable residues ranged from 183–2922 μg∙kg−1 in the five soils, with 4-ring PAHs (42.1 ± 4.2

The environmental effects of biochar-derived organic carbon (BDOC) have attracted increasing attention. Nevertheless, it is unknown how BDOC might affect the natural attenuation of widely distributed chloroalkanes (e.g., 1,1,2,2-tetrachloroethane (TeCA)) in aqueous environments. We firstly observed that the kinetic constants (ke) of TeCA dehydrochlorination in the presence of BDOC samples or their different molecular size fractions (<1 kDa, 1∼10 kDa, and >10 kDa) ranged from 9.16×103 to 26.63×103 M−1h−1, which was significantly greater than the ke (3.53×103 M−1h−1) of TeCA dehydrochlorination in the aqueous solution at pH 8.0, indicating that BDOC samples and their different molecular size fractions all could promote TeCA dehydrochlorination. For a given BDOC sample, the kinetic constants (ke) of TeCA dehydrochlorination in the initial pH 9.0 solution was 2∼3 times greater than that in the initial pH 8.0 solution due to more formation of conjugate bases. Interestingly, their DOC concentration normalized kinetic constants (ke/[DOC]) were negatively correlated with SUVA254, and positively correlated with A220/A254 and the abundance of aromatic protein-like/polyphenol-like matters. A novel mechanism was proposed that the C-H dipole of BDOC aliphatic structure first bound with the C-Cl dipole of TeCA to capture the TeCA molecule, then the conjugate bases (-NH-/-NH2 and deprotonated phenol-OH of BDOC) could attack the H atom attached to the β-C atom of bound TeCA, causing a C-Cl bond breaking and the trichloroethylene formation. Furthermore, a fraction of >1 kDa had significantly greater ke/[DOC] values of TeCA dehydrochlorination than the fraction of <1 kDa because >1 kDa fraction had higher aliphiticity (more dipole-dipole sites) as well as more N-containing species and aromatic protein-like/polyphenol-like matters (more conjugate bases). The results are helpful for profoundly understanding the BDOC-mediated natural attenuation and fate change of chloroalkanes in the environment.