Riverbank filtration is a nature-based water treatment strategy known for its effective removal of organic micropollutants. Yet, the mechanisms governing their biodegradation, especially the role of redox transitions in mediating biotransformation, remain insufficiently understood. Here, we integrate metagenomic profiling with chemical analytics in a 10 m simulated riverbank filtration system to demonstrate how sequential oxidizing-reducing degradation enhances organic micropollutant transformation. Oxygen stratification structured distinct microbial and enzymatic pathways: oxidizing zones (>+200 mV redox potential) facilitated cytochrome P450-mediated oxidation (oxidizing condition, OXD), while subsequent redox shifts to reducing conditions (←400 mV, sequential oxidizing-reducing (SOR) conditions) activated reductive transformations (e.g., via nitronate monooxygenase and aldehyde dehydrogenase) and conjugation pathways. These SOR conditions significantly enhanced the removal of recalcitrant compounds, including irbesartan (+25.3%), benzotriazole (13.4%), and gabapentin (+9.7%). Metagenomic analysis revealed redox-driven microbial specialization, with Pseudomonadota and Nitrospirota dominating in oxidizing zones and reducing microzones enriched in pathways associated with nitrotoluene and ethylbenzene degradation, providing genomic evidence for sequential organic micropollutant breakdown. These findings establish a mechanistic framework for harnessing oxidizing-reducing microbial partnerships to amplify organic micropollutant removal in nature-based water treatment systems, which can be used for riverbank filtration site selection and well field construction and optimization.

Rivers are crucial for ecological balance and biodiversity, but human activities have disrupted them, forming natural-artificial water systems. Microorganisms are key to river ecosystems, yet most studies focus on single habitats, leaving a knowledge gap regarding how microbial community characteristics shift across habitat types under environmental heterogeneity and anthropogenic disturbances. This study investigated bacterial diversity, community structure, and co-occurrence networks in water and sediments in the Daqing River Basin across different habitats- upper Daqing River (DQHU, natural channel), Baiyangdian (BYD, wetland), Zhaowang New River (ZWXQ, artificial channel), and lower Daqing River (DQHD, natural-anthropogenic interaction zone). Planktonic communities exhibited the highest Chao richness in ZWXQ (40.35), while benthic richness peaked in BYD (Chao index=57.73). Proteobacteria dominated planktonic (20-30%) and benthic communities (20-30%), with Actinobacteriota co-dominating planktonic systems. LEfSe identified ZWXQ (artificial channel) as having the most planktonic biomarkers (n = 23) and BYD the highest benthic biomarkers (n = 11). NCM indicated stochastic planktonic assembly, while benthic communities showed increasing deterministic control along the DQHU-ZWXQ-DQHD gradient. Source tracking showed BYD planktonic/benthic communities primarily originated from DQHU (90%), while DQHD benthic microbes derived largely from ZWXQ (39%). Venn analysis highlighted habitat-specific uniqueness: BYD benthic communities contained > 50% unique species, contrasting with ZWXQ (<15%). Network analysis revealed ZWXQ had the highest planktonic/benthic network density (0.067/0.106), while BYD planktonic community hosted the most keystone species (module hubs/connectors:n = 4). These findings highlight habitat heterogeneity and anthropogenic impacts on microbial ecology in natural-artificial water systems, providing differentiated strategies for watershed management and ecological restoration.

Organic micropollutants (OMPs) in wastewater treatment plant (WWTP) effluent pose persistent risks to aquatic ecosystems and drinking water sources. Riverbank filtration (RBF) is a nature-based treatment process, yet the compartment-specific roles of riverbed sediment and downstream soil in OMP attenuation remain poorly resolved under wastewater-impacted conditions. Here, we combined targeted chemical analysis, OMP property compilation, shotgun metagenomics, EnviPath-based biotransformation annotation, and exploratory network analysis to investigate OMP attenuation in a laboratory-scale RBF system treating real WWTP effluent for 10 months. Nineteen OMPs were monitored along a sequential sediment-soil filtration pathway. Sediment preferentially attenuated hydrophilic or charged compounds, including lidocaine, amantadine, and sotalol, whereas soil contributed more strongly to the attenuation of naproxen, atenolol, and losartan. Metagenomic profiling revealed distinct microbial communities and functional gene repertoires between sediment and soil after long-term operation. Sediment harbored higher relative abundances of genes associated with oxidative xenobiotic transformation, including cytochrome P450-related enzymes, demethylases, dehydrogenases, oxidases, and aromatic compound degradation pathways. An exploratory Spearman network further identified associations among microbial genera, EnviPath-annotated candidate biotransformation genes, and OMP removal rates, including 17 KO-OMP links supported by both correlation and pathway annotation. These findings indicate that sediment and soil develop complementary microbial functional potentials that may support compound-specific OMP attenuation. This study provides a mechanistic basis for optimizing sediment-soil configurations in wastewater-impacted RBF systems and for improving nature-based barriers against diverse OMP mixtures.

This chapter explores innovative energy and environmental strategies in urban water systems to advance carbon neutrality. It highlights (i) the importance of integrating advanced water purification technologies such as riverbank filtration and reverse osmosis to remove emerging contaminants, (ii) the role of artificial intelligence and machine learning in optimizing wastewater treatment, (iii) the necessity of both engineering and non-engineering approaches to achieve greenhouse gas (GHG) emission reductions in urban water systems, (iv) the increasing relevance of circular economy principles for recovering useful resources from urban water systems, and (v) the role of life cycle assessments to ensure environmental sustainability in the pursuit of resource recovery. Case study cities illustrate the progress in decarbonizing urban water systems, with a focus on the potential and challenges of GHG emissions management. A systems thinking approach is advocated for identifying system-wide GHG mitigation opportunities in urban water systems and for leveraging GHG mitigation with environmental co-benefits and trade-offs.

Plastic pipes are increasingly used in drinking water distribution systems, yet their impact on water quality remains insufficiently understood. Here, we systematically investigate the dual outcomes posed by plastic pipes─chemical leaching and cascaded microbial exposure risks─by integrating Fourier Transform Ion Cyclotron Resonance Mass Spectrometry and metagenomic analysis. Our results reveal that plastic pipes continuously release dissolved organic matter (DOM), including organic additives such as bisphenols (BPs) and organophosphate esters (OPEs), which profoundly reshape microbial communities. Under chlorinated conditions, leached DOM alters microbial diversity, promoting chlorine-resistant bacteria and opportunistic pathogens (OPs), while under nonchlorinated conditions, it accelerates microbial growth and enriches antibiotic resistance genes (ARGs), OPs, and virulence factors (VFs). Among plastic materials, polyethylene (PE) exhibited the highest chemical risk, releasing high concentrations of TCPP (700 ng/L) and BPF (200 ng/L) along with 207-227 unique DOM molecules. In contrast, polyvinyl chloride (PVC) supported the highest OP abundance, while polypropylene random copolymer (PPR) fostered the greatest OP diversity. These findings challenge conventional drinking water safety assessments that separate chemical contamination from microbial risk, underscoring the urgent need for an integrated risk assessment framework. Furthermore, they highlight the necessity of paying greater attention to the chemical and cascading microbial issues arising from the leaching of plastic pipes into drinking water, and of conducting a more comprehensive assessment of the associated potential health risks.

Microbial contamination in building plumbing systems poses significant risks to public health at the point of use. Stagnation and warm temperatures are well-known drivers of microbial regrowth, but the effects of common short-term stagnation in touchless sensor faucets—widely used for hygiene and comfort—remain poorly understood. Here we show that microbial water quality in touchless sensor faucets changes during short-term stagnation (0.25–10 h) at varying temperatures (10, 30, and 40 °C). We identify two pivotal time points—2 and 4 h—where microbial diversity decreases and Legionella pneumophila concentrations increase significantly, driven by accelerated chlorine decay and biofilm contributions. Heating to 30 °C maximizes microbial biomass (measured as ATP) but minimizes L. pneumophila proliferation, whereas 40 °C reduces biomass while promoting L. pneumophila growth. These findings reveal a temperature-dependent microbial water quality guarantee period of 2–4 h, beyond which flushing is necessary to mitigate health risks. Optimizing faucet temperatures between 30 and 40 °C could balance microbial safety, user comfort, and energy efficiency, offering practical guidance for managing water quality in modern plumbing systems.

Shower systems create conditions conducive to the growth of opportunistic pathogens, but the timing and location of associated risks are poorly understood. In this study, we constructed 48 full size shower units with six incubation periods (4, 10, 16, 22, 30, and 40 weeks) and four water heater temperature (39, 45, 51, and 58 °C) to examine the dynamics of microbial growth and pathogen distribution. Results showed that during the initial stage (4 weeks), peak biomass was observed for all biofilms, ranked as shower hose (SHE) > cold-water pipe (CWP) > hot-water pipe (HWP), followed by a sharp decline by the 10th-week. At the 4th-week, the biofilm was loose and easily detached into the water, possibly promoted by leached organic carbon from plastic material, fostering the growth of specific microorganisms. The impacts of stagnation and temperature became more pronounced in CWP and HWP over time. Legionella pneumophila appeared in biofilms at the 4th-week, disappeared, and reappeared in large numbers since the 22nd-week. Differently, Mycobacterium spp. emerged in large numbers after 30 weeks. Both pathogens were notably enriched in showerheads and shower hoses. This study highlights critical periods of higher risk in shower systems, particularly in the early stages (4 weeks) and after 22 weeks, suggesting that risks can be mitigated by pre-soaking pipes or regularly cleaning (e.g., heat shock flushing) and replacing showerheads and hoses.

Extreme rainfall and urban flooding pose escalating risks to public health by mobilizing sewage and pathogenic microorganisms. In July 2021, record-breaking rainfall in Henan Province, China, caused catastrophic flooding, yet the microbial health risks associated with such events remain poorly quantified. Here, we applied high-throughput qPCR arrays to detect 21 pathogenic bacteria in floodwater and postflood tap water, and used quantitative microbial risk assessment (QMRA) to estimate infection probabilities for exposed residents. Our results showed that in floodwater, 21 pathogenic bacteria were detected, with Cryptosporidium spp. (579.8 gc/L) and Pseudomonas aeruginosa (13,500.9 gc/L), being prominent, which were also identified in tap water. Floodwater exposure substantially increases infection risks, highlighting ingestion and inhalation as primary pathways. Simple protective measures, such as avoiding contact with contaminated water, can significantly reduce risks. This study provides the first integrated molecular and risk-based assessment of microbial hazards during an extreme flood event. The findings underscore the importance of water quality monitoring, improved sewage and drainage management, and timely public health interventions such as boil water advisories. As climate change intensifies the frequency of extreme rainfall events, proactive surveillance and international collaboration will be essential to prevent waterborne disease outbreaks and protect vulnerable populations. HIGHLIGHTS center dot Combined high-throughput qPCR with quantitative microbial risk assessment (QMRA) to evaluate floodborne pathogens. center dot Provided the first integrated molecular-risk framework for assessing urban floodwater contamination. center dot Linked microbial evidence to public health protection and emergency water management. center dot Offered data-driven guidance for climate adaptation and flood-resilient urban systems.

Plant functions are governed by complex regulatory mechanisms that operate across diverse cell types in various tissues. However, the challenge of dissecting plant tissues has hindered the widespread application of single-cell technologies in plant research. Recent advancements in single-cell RNA sequencing (scRNA-seq) and spatial transcriptomics (ST) have propelled the field forward. scRNA-seq enables the examination of gene expression at the single-cell level, while ST preserves the spatial context of cellular organization. While previous reviews have discussed the breakthroughs of scRNA-seq and ST in plants, none have comprehensively addressed the use of these technologies to study plant responses to environmental stress at the cellular level. This review provides an in-depth analysis of the development, advantages, and limitations of single-cell and spatial transcriptomics, highlighting their critical role in unraveling plant strategies for coping with biotic and abiotic stresses. We also explore the challenges and future prospects of integrating scRNA-seq and ST in plant research. Understanding cell-specific responses and the complex interactions between cellular entities within the plant under stress is essential for advancing our knowledge of plant biology.

Rivers reflect natural-anthropogenic interactions, yet how urbanization affects riverine bacterial communities along rural-urban gradients is poorly understood. This study examined bacterial diversity and assembly mechanisms along such a gradient of river sediments. Results showed that bacterial diversity significantly decreased with increasing urban influence. Community assembly shifted from stochastic processes dominating in rural zones to environmental selection prevailing in urban zones. The rural-urban transition caused bacterial network instability, potentially reducing resilience. The participation of prevalent taxa decreased but the rare taxa related to chitinolysis and nitrate/nitrite denitrification were selectively enriched along with rural-urban gradient, suggesting rapid functional recruitment to exploit dissolved organic nitrogen and nitrate pulses typical of urban runoff. Our findings underscore that urbanization's influence on bacterial communities is more pronounced than the river's inherent natural characteristics. These insights highlight the profound ecological consequences of urbanization on river microbiomes, informing protection and restoration strategies.

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Although simulated studies have provided valuable knowledge regarding the communities of planktonic bacteria and biofilms, the lack of systematic field studies have hampered the understanding of microbiology in real-world service lines and premise plumbing. In this study, the bacterial communities of water and biofilm were explored, with a special focus on the lifetime development of biofilm communities and their key influencing factors. The 16S rRNA gene sequencing results showed that both the planktonic bacteria and biofilm were dominated by Proteobacteria. Among the 15,084 observed amplicon sequence variants (ASVs), the 33 core ASVs covered 72.8 %, while the 12 shared core ASVs accounted for 62.2 % of the total sequences. Remarkably, it was found that the species richness and diversity of biofilm communities correlated with pipe age. The relative abundance of ASV2 (f_Sphingomonadaceae) was lower for pipe ages 40–50 years (7.9 %) than for pipe ages 10–20 years (59.3 %), while the relative abundance of ASV10 (f_Hyphomonadaceae) was higher for pipe ages 40–50 years (19.5 %) than its presence at pipe ages 20–30 years (1.9 %). The community of the premise plumbing biofilm had significantly higher species richness and diversity than that of the service line, while the steel-plastics composite pipe interior lined with polyethylene (S-PE) harbored significantly more diverse biofilm than the galvanized steel pipes (S-Zn). Interestingly, S-PE was enriched with ASV27 (g_Mycobacterium), while S-Zn pipes were enriched with ASV13 (g_Pseudomonas). Moreover, the network analysis showed that five rare ASVs, not core ASVs, were keystone members in biofilm communities, indicating the importance of rare members in the function and stability of biofilm communities. This manuscript provides novel insights into real-world service lines and premise plumbing microbiology, regarding lifetime dynamics (pipe age 10–50 years), and the influences of pipe types (premise plumbing vs. service line) and pipe materials (S-Zn vs. S-PE).

Pipe materials appear to play an important role in the development of biofilms in drinking water distribution systems. However, there is controversy as to whether pipe materials shape the composition and diversity of bacterial communities in biofilms. To investigate the long-term effects of pipe materials on biofilms, triplicate samples of mature biofilms on unplasticized polyvinyl chloride (PVC-U), grey cast iron and asbestos cement (pipe age > 40 years) were obtained from three areas of an unchlorinated drinking water distribution system in the Netherlands. Illumina sequencing was performed and 773 OTUs (730 OTUs-814 OTUs) were detected within the biofilms on the three pipe materials, all of which were dominated by Proteobacteria (36.2%-46.1%). Both the alpha and beta diversity results showed that the bacterial communities of the biofilms formed on different pipe materials were highly similar. The neutral community model revealed that the assembly of the biofilm communities was governed by environmental selection rather than neutral processes. Among the 142 shared OTUs between the water and biofilm samples, there were 25 enriched OTUs (e.g., OTU7, assigned as Nitrospira spp.), which accounted for 62.6% of the total sequences, while 16 OTUs were disadvantaged (e.g., OTU14 and OTU40, assigned as Hyphomicrobiaceae), accounting for 2.2% of the sequences. Based on the findings, we propose and discuss a harmonisation process by which biofilms with significant differences due to the pipe material harmonize over time resulting in biofilms with similar bacterial communities. Our findings provide valuable insights into long-term biofilm development, bridging an essential gap in our current understanding of the influence of pipe materials on biofilm communities. These findings also highlight the importance of long-term studies and point to a potentially masked harmonizing process during biofilm development over years/decades.

Treated drinking water is delivered to customers through drinking water distribution systems (DWDSs). Although studies have focused on exploring the microbial ecology of DWDSs, knowledge about the effects of different water treatments on the bacterial community of biofilm and loose deposits in DWDS is limited. This study assessed the effects of additional treatments on the bacterial communities developed in 10 months' old pilot DWDSs. The results showed a similar bacterial community in the pipe-wall biofilm, which was dominated by Novosphingobium spp. (20-82 %) and Sphingomonas spp. (11-53 %), regardless of the treatment applied. The bacterial communities that were retained in the distribution systems (including pipe-wall biofilm and loose deposits) were similar to the particle-associated bacteria (PAB) in the corresponding supply water. The additional treatments showed clear effects of the removal and/or introduction of particles. The genera Aeromonas spp., Clostridium spp., Legionella spp., and Pseudomonas spp., which contain opportunistic pathogenic species, were only detected among the PAB in ion exchange system. Our study demonstrated that the biofilm community is consistent across treatments, and the contribution from bacteria in loose deposits is important but can be controlled by removing particles. These findings offer more insight into the origin and development of microbial ecology in DWDSs and suggest paths for further research on the possibility of managing the microbial ecology in distribution systems.

The upper Permian Longtan Formation is widely distributedin southwesternChina and is well known for multilayer coal and high organic shale,with significant shale gas potential that has yet to be fully exploredand developed. The Longtan coal-bearing strata are composed of complexlithological assemblages of fine-grained sedimentary rocks such assandstone, coal, shale, and limestone, which exhibit significant differencesfrom marine shale. To better understand the organic-rich lithofacies,their distribution, and their controlling factors, this study carriedout a detailed survey of the outcrop and drill cores in the westernGuizhou region and examined the fine-grained lithofacies, their assemblages,and their geochemical characteristics. The results showed that (1)the total organic carbon of the Longtan Formation shale in westernGuizhou ranged from 1.44 to 14.79%, with an average of 6.41%, andthe organic matter was mainly composed of vitrinite. The mineral compositionwas mainly clay minerals and brittle minerals; the clay minerals weremainly composed of kaolinite (average 11.13%) and illite/smectitemixed layers (average 26.69%) and the brittle minerals were mainlycomposed of quartz (average 31.63%) and feldspar (average 12.88%).(2) Eight types of lithofacies were identified, including silty mudstone,muddy siltstone, carbonaceous mudstone, carbonaceous shale, bioclastic-bearingmudstone, bioclastic-bearing sandstone, fine sandstone, and coal seam.(3) The six typical lithofacies assemblages were developed in theLongtan Formation, which represented different sedimentary environmentsof the marine-continental transitional facies in the studyarea. The lithofacies assemblages A and C represent sedimentationin the lagoon environment. The lithofacies assemblage B representspeat swamp facies. The lithofacies assemblage D represents a tidalflat facies peat flat-mixed flat-sand flat sedimentary environment.The lithofacies assemblage E and F represent the delta sedimentaryenvironment. (4) The sedimentary model of the Longtan Formation inwestern Guizhou was predominantly deltaic and tidal flat sedimentarysystems. Lithological and lithofacies studies of Longtan fine-grainedrocks were used to provide a geological framework for examining thefine grain deposition distribution and shale gas resource evaluation.This study is highly important for understanding the sedimentologyand oil and gas exploration in the region, providing a basis for identifyingand exploring coal-bearing shale gas potential and a reference forthe analysis of shale in the world's continental transitionalareas.

The photochemical properties of dissolved organic matter (DOM) were highly related to the molecular weight (MW) and organic compositions. In this study, the bulk algae- and macrophyte-derived DOM (ADOM and MDOM, respectively) and Suwannee River humic acid (SRHA) were applied and fractionated into low MW(LMW, <1 kDa) and high MW-(HMW-, 1 kDa tilde 0.45 mu m) fractions. The formation and mechanisms of photochemically produced reactive intermediates (e.g., HO center dot, 1O2, and 3CDOM*) for these bulk and MW-fractionated samples were compared via the irradiation experiment, fluorescence and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Results showed that humic-/fulvic-like substances were mainly distributed in the LMW fraction which occupied about 44-60% of total organic carbon for ADOM and MDOM and 13% for SRHA. Photochemical experiments showed that the autochthonous DOMs (e.g., ADOM and MDOM) were characterized with comparable formation rates and quantum yields of reactive oxygens with the allochthonous SRHA, suggesting the high photochemical formation potential. Further analysis showed obvious MW-dependent heterogeneities that, irrespective of DOM types, the LMW-fraction exhibited higher formation rates and quantum yields, followed by the bulk- and then the HMW-fractions. The fluorescence and FT-ICR-MS results indicated that the unique biochemical classes, i.e., humic-/fulvic-like moieties and protein-/lipid-derived compounds in the LMW fractions may be responsible for the high apparent quantum yields. This study highlighted the importance of simultaneous characterization of MW and organic compositions for evaluating the photochemical potential and other behaviors and effects of aquatic DOMs.

The transport and fate of nanoplastics (NPs) in aquatic environments are closely associated with their colloidal stability, which is affected by aging and natural organic matter (NOM) adsorption. This study systematically investigated the combined effects of photoaging and NOM (e.g. humic acids, HA; and a model protein, bovine serum albumin, BSA) on the aggregation kinetics of NPs (polystyrene, PS) in NaCl and CaCl2 solutions. Our results showed that photoaged NPs adsorbed less HA than pristine NPs due to weaker hydrophobic and π-π interactions. In return, HA showed weaker impacts on NPs' stability after photoaging. Differently, photoaged NPs absorbed more BSA than pristine NPs due to stronger hydrogen bonding and electrostatic attraction. Thus, the inhibitory effects of BSA on the aggregation kinetics of NPs were enhanced after photoaging. Regarding the effects of NOM on the aging of NPs, our results showed that HA competed with NPs for photons and underwent photo-degradation. Subsequently, the destruction/reconstruction of adsorbed HA increased (in NaCl) or decreased (in CaCl2) the stability of NPs. Notably, light radiation-induced flocculation of BSA molecules, which wrapped and integrated NPs and lead to their destabilization. Overall, this study provided new insights into the aggregation behavior of NPs in aquatic systems, which have significant implications for predicting the transport and fate of NPs in complex real-world environments.

Persistent organic pollutants such as polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin-like polychlorinated biphenyls (DL-PCBs) consisting of non-ortho and mono-ortho PCBs are suggested to be very hazardous and have adverse effects on human health. However, their levels and congener profiles in retail foods marketed in Guangdong Province of China have not been elucidated thus far. Thus, in this study, 226 individual samples of beef, freshwater fish, and pork marketed across four regions of Guangdong Province were randomly collected during 2013-2015 to determine their levels of PCDD/Fs and DL-PCBs. The results showed that the total toxic equivalency quantities (TEQs) of most samples were below the maximum limits except for the 26 samples collected from the vicinities of pollution areas. The median total TEQs of these three categories were 0.174, 0.488, and 0.113pgTEQ/g fw, respectively, which indicated that the contamination status of the studied foods was not serious. For congener profiles, significantly different patterns were observed in three food groups, but with the same major TEQ contributors being 2,3,4,7,8-PeCDF in beef, freshwater fish, and pork. Regional differences of congener profiles in each food group were also found in this study, which might be attributed to the regionally different distributions of PCDD/Fs and DL-PCBs in environment media. The dietary exposures of four population subgroups (girls, boys, male adults, and female adults) to PCDD/Fs and DL-PCBs via three food groups were estimated to assessed the potential risks. They were all lower than the provisional tolerable monthly intake (PTMI, 70pgTEQ/kgbw/month) established by Joint FAO/WHO Expert Committee on Food Additive. In these food categories, the exposure to PCDD/Fs and DL-PCBs via freshwater fish was the highest one, which accounted for about 20% of PTMI, indicating that it was the major route to expose dioxin compounds.

Organic matter (OM), and dissolved organic matter (DOM), have a major influence upon biogeochemical processes; most significantly, the carbon cycle. To date, very few studies have examined the spatial heterogeneity of DOM in paddy soils. Thus, very little is known about the DOM molecular profiles and the key environmental factors that underpin DOM molecular chemodiversity in paddy soils. Here, Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry was applied to unambiguously resolve 11 361 molecular formulas in 16 paddy soils; thereby elucidating the molecular characteristics of paddy soil DOM. Soil pH, iron complexing index (Fep/FeR) and C/N ratio were established to be key factors controlling DOM profiles. Polycyclic aromatics (derived from combustion) and polyphenols (derived from plants) increased with increasing pH, while polyphenols molecules, pyrogenic aromatics, and carboxylic compounds decreased with increasing iron complexing index. Patterns in molecular profiles indicated DOM in paddy soils to become more recalcitrant at higher soil C/N ratio and higher pH. Furthermore, plant-derived polyphenols and pyrogenic DOM were retained favorably by iron and the chemodiversity of DOM in paddy soil increased with increasing soil C/N ratios. This study provides critical information about DOM characteristics at a molecular level and will inform better global management of soil carbon in paddy soil ecosystems.

The "4 per mil" initiative recognizes the pivotal role of soil in carbon resequestration. The need for evidence to substantiate the influence of agricultural practices on chemical nature of soil carbon and microbial biodiversity has become a priority. However, owing to the molecular complexity of soil dissolved organic matter (DOM), specific linkages to microbial biodiversity have eluded researchers. Here, we characterized the chemodiversity of soil DOM, assessed the variation of soil bacterial community composition (BCC), and identified specific linkages between DOM traits and BCC. Sustained organic carbon amendment significantly ( P < 0.05) increased total organic matter reservoirs, resulted in higher chemodiversity of DOM and emergence of recalcitrant moieties (H/C < 1.5). In the meantime, sustained organic carbon amendment shaped the BCC to a more eutrophic state while long-term chemical fertilization directed the BCC toward an oligotrophic state. Meanwhile, higher connectivity and complexity were observed in organic carbon amendment by DOM-BCC network analysis, indicating that soil microbes tended to have more interaction with DOM molecules after organic matter inputs. These results highlight the potential for organic carbon amendments to not only build soil carbon stocks and increase their resilience but also mediate the functional state of soil bacterial communities.