Comparing molecular signatures of dissolved organic matter (DOM) in four large freshwater lakes differing in hydrological connectivity to the Changjiang River.

Freshwater lakes serve as active conduits for processing terrestrial dissolved organic matter (DOM), playing a crucial role in global carbon cycle. Little attention has been paid to how hydrological connectivity to a large river would affect the molecular signatures of DOM in lakes. Here, we systematically characterized and compared the molecular signatures of DOM in surface waters of four large freshwater lakes in the middle and lower Changjiang River basin that are directly connected to the river (Lake Dongting and Lake Poyang, referred to as Lakeconnected) or indirectly connected to the river (Lake Chao and Lake Tai, referred to as Lakenonconnected). The DOM in Lakeconnected was found to have similar total organic carbon (TOC)-normalized contents and characteristics of lignin phenols to the DOM in surface waters from the upstream Changjiang river, indicating allochthonous/terrestrial sources from riverine inputs. As indicated by the UV-vis and fluorescence analyses, the DOM in Lakeconnected overall had higher aromaticity and larger average molecular weight as well as stronger allochthonous feature compared to the DOM in Lakenonconnected. Consistently, the FT-ICR MS analysis revealed that the DOM in Lakeconnected had higher molecular diversity, higher unsaturation degree, and larger proportions of highly aromatic compounds. In contrast, the DOM in Lakenonconnected had larger proportions of lipids and peptide-like structures, but lower proportions of aromatic compounds, which could be ascribed to the enhanced autochthonous production and photodegradation due to pollution and eutrophication as well as longer water residence time. The results highlight the strong impacts of the hydrological connectivity to a large river on the molecular signatures of lake DOM. CAPSULE: The hydrological connectivity of the lakes to the Changjiang River has strong impacts on the molecular signatures of lake DOM.

The continuous increased stability of sediment dissolved organic matter implies ecosystem degradation of lakes in the cold and arid regions.

The characteristics of lake dissolved organic matter (DOM) pool and lake ecosystem interact, and studying the responses between sediment DOM characteristics and lake ecosystem changes may shed light on the inherent connection between ecosystem evolution and carbon biogeochemical cycles. Lakes in cold and arid regions are sensitive to changes and accumulate large amounts of carbon as DOM, which may provide a window into more explicit relationships between ecosystem evolution and changes in sediment DOM characteristics in time dimension. However, considerable blind spots exist in the responses between the sediment DOM and ecosystem evolution on time scale and the underlying mechanisms. In this study, multiple approaches were combined to investigate the relationship between the variation trend of sediment DOM characteristics and the evolution of fragile lake ecosystems across three different lake ecosystems in cold and arid regions of China. A strong positive relationship between sediment DOM stabilities, especially humification, and ecosystem degradation was found, consistent for the three lakes. Ultra-high-resolution mass spectrometry and structural equation modeling revealed that the changes of ecosystems affected sediment DOM stability through direct pathways (0.24), such as the contents of terrestrial DOM in lake DOM pool, and indirect pathways, including algae-mediated (0.43) and salinity-mediated pathways (0.22), which all increased the contents of refractory DOM in the lake DOM pool and sediments. Based on the fact that DOM stability changes could act on the ecosystem in turn, a possible positive feedback mechanism between ecosystem degradation and increased DOM stability was further inferred. These results suggested that the continuous increased stability of sediment DOM in may implies ecosystem degradation of lakes in the cold and arid regions. This study provides a new perspective for recognizing ecosystem evolution through sediment DOM and improves the understanding of the interaction of lake ecosystem evolution and the biogeochemical cycle of DOM.

Preferential Partitioning of Per- and Polyfluoroalkyl Substances (PFAS) and Dissolved Organic Matter in Freshwater Surface Microlayer and Natural Foam.

Per- and polyfluoroalkyl substances (PFAS) are surfactants that can accumulate in the surface microlayer (SML) and in natural foams, with potential elevated exposure for organisms at the water surface. However, the impact of water chemistry on PFAS accumulation in these matrices in freshwater systems is unknown. We quantified 36 PFAS in water, the SML, and natural foams from 43 rivers and lakes in Wisconsin, USA, alongside measurements of pH, cations, and dissolved organic carbon (DOC). PFAS partition to foams with concentration ranging 2300-328,200 ng/L in waters with 6-139 ng/L PFAS (sum of 36 analytes), corresponding to sodium-normalized enrichment factors ranging <50 to >7000. Similar enrichment is observed for DOC (∼70). PFAS partitioning to foams increases with increasing chain length and is positively correlated with [DOC]. Modest SML enrichment is observed for PFOS (1.4) and FOSA (2.4), while negligible enrichment is observed for other PFAS and DOC due to low specific surface area and turbulent conditions that inhibit surfactant accumulation. However, DOC composition in the SML is distinct from bulk water, as assessed using high-resolution mass spectrometry. This study demonstrates that natural foams in unimpacted and impacted waters can have elevated PFAS concentrations, whereas SML accumulation in surface waters is limited.

Machine learning for high-precision simulation of dissolved organic matter in sewer: Overcoming data restrictions with generative adversarial networks.

Understanding the transformation process of dissolved organic matter (DOM) in the sewer is imperative for comprehending material circulation and energy flow within the sewer. The machine learning (ML) model provides a feasible way to comprehend and simulate the DOM transformation process in the sewer. In contrast, the model accuracy is limited by data restriction. In this study, a novel framework by integrating generative adversarial network algorithm-machine learning models (GAN-ML) was established to overcome the drawbacks caused by the data restriction in the simulation of the DOM transformation process, and humification index (HIX) was selected as the output variable to evaluate the model performance. Results indicate that the GAN algorithm's virtual dataset could generally enhance the simulation performance of regression models, deep learning models, and ensemble models for the DOM transformation process. The highest prediction accuracy on HIX (R2 of 0.5389 and RMSE of 0.0273) was achieved by the adaptive boosting model which belongs to ensemble models trained by the virtual dataset of 1000 samples. Interpretability analysis revealed that dissolved oxygen (DO) and pH emerge as critical factors warranting attention for the future development of management strategies to regulate the DOM transformation process in sewers. The integrated framework proposed a potential approach for the comprehensive understanding and high-precision simulation of the DOM transformation process, paving the way for advancing sewer management strategy under data restriction.

Nanoscale Sequential Reactor Design Achieves Effective Removal of Disinfection Byproduct Precursors in Catalytic Ozonation.

Transforming dissolved organic matter (DOM) is a crucial approach to alleviating the formation of disinfection byproducts (DBPs) in water treatment. Although catalytic ozonation effectively transforms DOM, increases in DBP formation potential are often observed due to the accumulation of aldehydes, ketones, and nitro compound intermediates during DOM transformation. In this study, we propose a novel strategy for the sequential oxidation of DOM, effectively reducing the levels of accumulation of these intermediates. This is achieved through the development of a catalyst with a tailored surface and nanoconfined active sites for catalytic ozonation. The catalyst features a unique confinement structure, wherein Mn-N4 moieties are uniformly anchored on the catalyst surface and within nanopores (5-20 Å). This design enables the degradation of the large molecular weight fraction of DOM on the catalyst surface, while the transformed smaller molecular weight fraction enters the nanopores and undergoes rapid degradation due to the confinement effect. The generation of *Oad as the dominant reactive species is essential for effectively reducing these ozone refractory intermediates. This resulted in over 70% removal of carbonaceous and nitrogenous DBP precursors as well as brominated DBP precursors. This study highlights the importance of the nanoscale sequential reactor design and provides new insights into eliminating DBP precursors by the catalytic ozonation process.

Internal transformation and damming regulate the longitudinal variation of DOM bioavailability in a large river.

Understanding the spatial patterns of dissolved organic matter (DOM) and factors that influence them is crucial for maintaining river ecosystem functions and riverine health, considering the significant role of DOM in water quality and aquatic ecosystems. Nevertheless, there is limited knowledge regarding the spatial variation of DOM bioavailability and the factors driving them in large river systems. This study involved 39 sampling locations along the main stem of the Changjiang River, spanning its entire length (> 5000 km) during a dry season. Spatial patterns of DOM were assessed by measurements of DOC concentrations and eight fluorescence DOM indices, namely fluorescence index (FI-A and FI-B), Trytophan/Tyrosine, Humic A, Humic C, humification indices (HIX-A and HIX-B), and Freshness index (ß/α). The results revealed that the water DOM in the main stem of the Changjiang River primarily originated from terrestrial sources. A decline in DOM bioavailability was observed from the upper to the lower basin, aligning with the carbon processing prediction rather than the river continuum concept (RCC). The pure effect of physicochemical factors (25.30%) was greater than that of geographic factors (9.40%). The internal transformation processes determined the significant longitudinal decreases of DOM bioavailability. While no significant difference in DOM bioavailability was observed between reaches before and after the dams, the construction of dams was found to improve DOM bioavailability at the subsection scale and reduce the spatial autocorrelation of DOM bioavailability across the entire basin.

Unravelling structure evolution of dissolved organic matter during oxidation by persulfate: Insights from aromaticity and fluorescence analysis.

Persulfate advanced oxidation technology is widely utilized for remediating organic-contaminated groundwater. Post-remediation by persulfate oxidation, the aromaticity of dissolved organic matter (DOM) in groundwater is significantly reduced. Nevertheless, the evolution trends of aromaticity and related structural changes in DOM remained unclear. Here, we selected eight types of DOM to analyze the variation in aromaticity, molecular weight, and fluorescence characteristics during oxidation by persulfate using optical spectroscopy and parallel faction analysis combined with two-dimensional correlation spectroscopy analysis (2D PARAFAC COS). The results showed diverse trends in the changes of aromaticity and maximum fluorescence intensity (Fmax) among different types of DOM as the reaction time increases. Four types of DOM (humic acid 1S104H, fulvic acid, and natural organic matters) exhibited an initially noteworthy increase in aromaticity followed by a decrease, while others demonstrated a continuous decreasing trend (14.3%-69.4%). The overall decreasing magnitude of DOM aromaticity follows the order of natural organic matters ≈ commercial humic acid > fulvic acid > extracted humic acid. The Fmax of humic acid increased, exception of commercial humic acid. The Fmax of fulvic acid initially decreased and then increased, while that of natural organic matters exhibited a decreasing trend (86.4%). The fulvic acid-like substance is the main controlling factor for the aromaticity and molecular weight of DOM during persulfate oxidation process. The oxidation sequence of fluorophores in DOM is as follows: fulvic-like substance, microbial-derived humic-like substance, humic-like substance, and aquatic humic-like substance. The fulvic-like and microbial-derived humic-like substances at longer excitation wavelengths were more sensitive to the response of persulfate oxidation than that of shorter excitation wavelengths. This result reveals the structure evolution of DOM during persulfate oxidation process and provides further support for predicting its environmental behavior.

Mixing Performance of a Passive Micromixer Based on Split-to-Circulate (STC) Flow Characteristics.

We propose a novel passive micromixer leveraging STC (split-to-circulate) flow characteristics and analyze its mixing performance comprehensively. Three distinct designs incorporating submerged circular walls were explored to achieve STC flow characteristics, facilitating flow along a convex surface and flow impingement on a concave surface. Across a broad Reynolds number range (0.1 to 80), the present micromixer substantially enhances mixing, with a degree of mixing (DOM) consistently exceeding 0.84. Particularly, the mixing enhancement is prominent within the low and intermediate range of Reynolds numbers (0.1

Comparison of Coagulation-Integrated Sand Filtration and Ultrafiltration for Seawater Reverse Osmosis Pretreatment.

The removal of dissolved organic matter (DOM) from seawater before the reverse osmosis (RO) processes is crucial for alleviating organic fouling of RO membranes. However, research is still insufficiently developed in the comparison of the effectiveness of integrating coagulation with ultrafiltration (UF) or sand filtration (SF) in the pretreatment stage of seawater reverse osmosis (SWRO) for the removal of DOM. In this study, we investigated the effect of pretreatment technologies on RO fouling caused by DOM in seawater, including the integration of coagulation and sand filtration (C-S pretreatment) and the integration of coagulation and ultrafiltration (C-U pretreatment). Both integrated pretreatments achieved comparable DOM removal rates (70.2% for C-U and 69.6% for C-S), and C-S exhibited enhanced removal of UV-absorbing compounds. Although C-U was more proficient in reducing the silt density index (below 2) compared to C-S (above 3) and improved the elimination of humic acid-like organics, it left a higher proportion of tyrosine-protein-like organics, soluble microbial by-product-like organics, and finer organics in the effluent, leading to the formation of a dense cake layer on RO membrane and a higher flux decline. Therefore, suitable technologies should be selected according to specific water conditions to efficiently mitigate RO membrane fouling.

Persistence of dissolved organic matter in sediments influenced by environmental factors：Implication for nutrition and carbon cycle.

The persistence of dissolved organic matter (DOM) plays a crucial role in the cycling and distribution of carbon and nutrients. Nonetheless, our understanding of how environmental alterations affect the persistence of sedimentary DOM remains incomplete. Excitation Emission Fluorescence Matrix-Parallel Factor Analysis (EEM-PARAFAC) was used to examine the fluorescence and compositional characteristics of hydrophilic and hydrophobic DOM (separated using XAD-8 resin) within sediments from twelve lakes and reservoirs. Fluorescence analysis indicated that DOM persistence is dependent on the proportions of the three components derived from PARAFAC. The Mantel test showed that climatic factors had the most significant impact on DOM persistence (Mantel's r = 0.46-0.54, Mantel's p = 0.001-0.007), while anthropogenic (Mantel's r = 0.24-0.32, Mantel's p = 0.03-0.05) and hydrological factors (Mantel's r = 0.03-0.22, Mantel's p = 0.06-0.40) had a somewhat lesser influence. Environmental changes resulted in a consistent decline in DOM persistence from Northeast to Southwest China, accompanied by an increase in gross primary productivity (GPP). Reduced DOM persistence due to climate, hydrological, and anthropogenic factors may lead to elevated concentrations of total phosphorus (TP), contributing to deteriorating water quality and events such as algal blooms. The decline in water quality due to reduced DOM persistence in lakes with high GPP can exacerbate the transition from carbon sinks to carbon sources. Consequently, the persistence of sedimentary DOM significantly influences nutrient and carbon cycling in lakes. Investigating DOM persistence in lakes across diverse geographic locations offers a new perspective on lake eutrophication and carbon emissions. Furthermore, it is crucial to develop targeted recommendations for lake restoration and management.

Polystyrene microplastics facilitate formation of refractory dissolved organic matter and reduce CO2 emissions.

Microplastics, as a type of anthropogenic pollution in aquatic ecosystems, affect the carbon cycle of organic matter. Although some studies have investigated the effects of microplastics on dissolved organic matter (DOM), the impact of alterations in the chemical properties of microplastics on refractory DOM and carbon release remains unclear. Here, we observed that microplastic treatments (e.g., polystyrene, PS) altered the composition and function of microbial community, notably increasing the abundance of microbial families involved in consuming easily degradable organic matter. During the process in which microbial community decomposed organic matter into DOM, PS underwent surface oxidation. The oxidized PS aggregated with DOM and microorganisms through electrostatic interactions and chemical bonds. Moreover, these interactions between oxidized PS and microbial community affect the utilization of organic matter, resulting in a significant decrease in CO2 emissions. Specifically, total CO2 emissions decreased by approximately 23.76 % with 0.1 mg/L PS treatment and by 44.97 % with 10 mg/L PS treatment compared to those in PS-free treatments over the entire reaction. These findings underscored the significance of the chemical properties of PS in the interactions among DOM and microorganisms, emphasizing the potential impact of PS microplastics on the carbon cycle in ecosystems.

Tracing sources of dissolved organic matter along the terrestrial-aquatic continuum in the Ore Mountains, Germany.

There is growing concern about the rising levels of dissolved organic matter (DOM) in surface waters across the Northern hemisphere. However, only limited research has been conducted to unveil its precise origin. Compositional changes along terrestrial-aquatic pathways can help determine the terrestrial sources of DOM in streams. Stream water, soil water and soil horizons were sampled at four sites representing typical settings within a forested catchment in the Ore Mountains (Erzgebirge, Germany) from winter 2020 to spring 2022. The samples were analyzed using pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The resulting data were successfully subjected to semi-automatic processing of the molecular composition of DOM, reaching a percentage of identified peaks up to 98 %. Principal component analysis (PCA) and cluster analyses were carried out to identify distinct differences between DOM from the potential sources and in the streams. According to the PCA, organic soil horizons, soil water, and stream water samples could be clearly distinguished. Cluster analysis revealed that soil water DOM at all depths of Peats and deeper horizons of the Peaty Gleysols contributed the most to DOM in the stream section dominated by organic soils. In areas dominated by mineral soils, stream DOM resembled the DOM from the deeper mineral horizons of Cambisols and Podzols. Overall, our results suggested that most of the DOM exported from the catchment was derived from deeper mineral soil horizons, with little contribution of DOM derived from organic soils. Therefore, DOM fingerprint analysis of in-situ soil water proved to be a promising approach for tracing back the main sources of stream water DOM.

Coupled redox cycling of arsenic and sulfur regulates thioarsenate enrichment in groundwater.

High­arsenic groundwater is influenced by a combination of processes: reductive dissolution of iron minerals and formation of secondary minerals, metal complexation and redox reactions of organic matter (OM), and formation of more migratory thioarsenate, which together can lead to significant increases in arsenic concentration in groundwater. This study was conducted in a typical sulfur- and arsenic-rich groundwater site within the Datong Basin to explore the conditions of thioarsenate formation and its influence on arsenic enrichment in groundwater using HPLC-ICPMS, hydrogeochemical modeling, and fluorescence spectroscopy. The shallow aquifer exhibited a highly reducing environment, marked by elevated sulfide levels, low concentrations of Fe(II), and the highest proportion of thioarsenate. In the middle aquifer, an optimal ∑S/∑As led to the presence of significant quantities of thioarsenate. In contrast, the deep aquifer exhibited low sulfide and high Fe(II) concentration, with arsenic primarily originating from dissolved iron minerals. Redox fluctuations in the sediment driven by sulfur­iron minerals generated reduced sulfur, thereby facilitating thioarsenate formation. OM played a crucial role as an electron donor for microbial activities, promoting iron and sulfate reduction processes and creating conditions conducive to thioarsenate formation in reduced and high­sulfur environments. Understanding the process of thioarsenate formation and the influencing factors is of paramount importance for comprehending the migration and redistribution of arsenic in groundwater systems.

Regional differences in lead (Pb) and tetracycline (TC) binding behavior of sediment dissolved organic matter (SDOM): Effects of DOM heterogeneity and microbial degradation.

Lake Nansi, primarily dominated by macrophytes, faces threats from heavy metals and antibiotics due to human activity. This study investigated sediment dissolved organic matter (SDOM) characteristics and complexation of lead (Pb) and tetracycline (TC) in barren zone (BZ) and submerged macrophytes zone (PZ). Additionally, a microbial degradation experiment was conducted to examine its impact on the regional variations in complexation. SDOM abundance and protein-like materials in PZ was significantly greater than in BZ, indicating a probable contribution from the metabolism and decomposition of submerged macrophytes. Both zones exhibited a higher affinity of SDOM for Pb compared to TC, with all four components participating in Pb complexation. Protein-like materials in PZ had a higher binding ability (LogKPb=4.19 ± 1.07, LogKTC=3.89 ± 0.67) than in BZ (LogKPb=3.98 ± 0.61, LogKTC=3.69 ± 0.13), suggesting a potential presence of organically bound Pb and TC due to the higher abundance of protein-like materials in PZ. Although microbial communities differed noticeably, the degradation patterns of SDOM were similar in both zones, affecting the binding ability of SDOM in each. Notably, the fulvic-like component C4 emerged as the dominant binding material for both Pb and TC in both zones. Degradation might increase the amount of organically bound TC due to the increase in the LogKTC.

Insights into the transformation of dissolved organic matter and carbon preservation on a MnO2 surface: Effect of molecular weight of dissolved organic matter.

Dissolved Organic Matter (DOM) is easily adsorbed and transformed by soil minerals and is an important redox-active component of soil and sediment. However, the effects of the molecular weight of DOM on the interface between MnO2 and DOM remain unclear. Herein, fulvic acid (FA) from peat was size-fractionated into four molecular weight fractions (FA>10kDa, FA5-10kDa, FA3-5kDa, and FA<3kDa) and then reacted with δ-MnO2 in this study. The affinity of FA for MnO2 varied significantly with different molecular weights, and large molecular weight FA was more easily adsorbed by MnO2. After 30 h of reaction, the highest mineralization rate was for FA>10kDa (42.39 %), followed by FA5-10kDa (28.65 %), FA3-5kDa (25.58 %), and FA<3kDa (20.37 %), consistent with the results of adsorption. The stronger reducing ability of the large molecular weight fraction of FA to MnO2 was mainly attributed to hydrophobic functional groups, promoting adsorption by MnO2 and the exposure of more active sites. The main active species involved in the mineralization of FA were •OH and Mn4+ through the quenching experiment. Our findings confirm that the large molecular weight fractions of FA play a crucial part in the adsorption and redox reactions of MnO2. These results may help evaluate the performance of different molecular characteristics of FA in the biogeochemical cycles of MnO2 in the soil environment.

Spatial distribution of sediment dissolved organic matter in oligotrophic lakes and its binding characteristics with Pb(II) and Cu(II).

Dissolved organic matter (DOM), the most active component in interstitial waters, determines the stability of heavy metals and secondary release in sediments. However, little is known about the composition and metal-binding patterns of DOM in interstitial water from oligotrophic lakes affected by different anthropogenic perturbations. Here, 18 interstitial water samples were prepared from sediments in agricultural, residential, tourist, and forest regions in an oligotrophic lake (Shengzhong Lake in Sichuan Province, China) watershed. Interstitial water quality and DOM composition, properties, and Cu(II)- and Pb(II)-binding characteristics were measured via physicochemical analysis, UV-vis spectroscopic, fluorescence excitation-emission matrix-parallel factor analysis (EEM-PARAFAC), and fluorescence titration methods. The DOM, which was produced mainly by microbial activities, had low molecular weights, humification degrees, and aromaticity. Based on EEM-PARAFAC results, the DOM was generally composed of tryptophan- (57.7%), terrestrial humic- (18.7%), microbial humic- (15.6%), and tyrosine-like (8.0%) substances. The DOM in the metal complexes was primarily composed of tryptophan-like substances, which accounted for ~42.6% of the DOM-Cu(II) complexes and ~72.0% of the DOM-Pb(II) complexes; however, microbial humic-like substances primarily contributed to the stability of DOM-Cu(II) (logKCu = 3.7-4.6) and DOM-Pb(II) (logKPb = 4.3-4.8). Water quality parameters did not significantly affect the stability of DOM-metal complexes. We demonstrated that the metal-binding patterns of DOM in interstitial water from oligotrophic lakes are highly dependent on microbial DOM composition and are affected by anthropogenic perturbations to a lesser extent.

Deciphering the Role of Microbial Extracellular and Intracellular Organic Matter in Antibiotic Photodissipation: Molecular and Fluorescent Profiling under Natural Radiation.

This study addresses existing gaps in understanding the specific involvement of dissolved organic matter (DOM) fractions in antibiotic photolysis, particularly under natural conditions and during DOM photobleaching. Employing fluorescent, chemical, and molecular analysis techniques, it explores the impact of extracellular and intracellular organic matter (EOM and IOM) on the photodissipation of multiclass antibiotics, coupled with DOM photobleaching under natural solar radiation. Key findings underscore the selective photobleaching of DOM fractions, propelled by distinct chemical profiles, influencing DOM-mediated antibiotic photolysis. Notably, lipid-like substances dominate in the IOM, while lignin-like substances prevail in the EOM, each uniquely responding to sunlight and exhibiting selective photobleaching. Sunlight primarily targets fulvic acid-like lignin components in EOM, contrasting the initial changes observed in tryptophan-like lipid substances in IOM. The lower photolability of EOM, attributed to its rich unsaturated compounds, contributes to an enhanced rate of indirect antibiotic photolysis (0.339-1.402 h-1) through reactive intermediates. Conversely, the abundance of aliphatic compounds in IOM, despite it being highly photolabile, exhibits a lower mediation of antibiotic photolysis (0.067-1.111 h-1). The triplet state excited 3DOM* plays a pivotal role in the phototransformation and toxicity decrease of antibiotics, highlighting microbial EOM's essential role as a natural aquatic photosensitizer for water self-purification. These findings enhance our understanding of DOM dynamics in aquatic systems, particularly in mitigating antibiotic risks, and introduce innovative strategies in environmental management and water treatment technologies.

Pb/As simultaneous removal from soil leachate of Pb/Zn smelting sites by magnetic biochar.

Lead (Pb) and arsenic (As) contaminated soils, caused by Pb and zinc (Zn) smelting activities, pose an urgent environmental issue. Magnetic biochar (MB) has been regarded as an increasingly appealing candidate for the remediation of multi-metals in contaminated soils or their leachate. Finding economically feasible preparation methods for MB and demonstrating its remediation potential is desperately required for the remediation of such complex smelting sites. In this study, a modified MB was prepared using an optimized co-precipitation method, and its application potential for Pb/As simultaneous removal based on the basic properties of a typical Pb/Zn smelting site was evaluated. The surface modifications of MB facilitated the encapsulation of various ultrafine iron oxide particles, predominantly γ-Fe2O3 and Fe3O4, whilst notably enhancing the presence of oxygen-containing surface functional groups. The adsorption of Pb(II) and As(III) by MB was well-described using the pseudo-second-order adsorption and Langmuir models. The existence of SO42- and Ca2+ in the soil leachate competed with the adsorption sites for Pb(II) and As(III). Notably, within the pH range of 5-9, the adsorption efficiency of Pb(II) by MB increased with the rising solution pH, whereas alterations in pH minimally affected the removal rate of As(III), maintaining a consistent removal rate exceeding 95%. Furthermore, dissolved organic matter (DOM) abundant in organic functional groups, particularly CO and CC groups, significantly augmented the adsorption affinity for both Pb(II) and As(III). An application rate of 2 g/L could effectively reduce the concentration of Pb(II) and As(III) in soil leachate to <0.05 mg/L. The findings demonstrated the potential of the prepared MB for simultaneous removal of As(III) and Pb(II) in soil leachate, which should be beneficial to multi-metals polluted soil remediation in Pb/Zn smelting sites.

Effects of Biochar and Straw Amendment on Soil Fertility and Microbial Communities in Paddy Soils.

Straw and biochar, two commonly used soil amendments, have been shown to enhance soil fertility and the composition of microbial communities. To compare the effects of straw and biochar on soil fertility, particularly focusing on soil dissolved organic matter (DOM) components, and the physiochemical properties of soil and microbial communities, a combination of high-throughput sequencing and three-dimensional fluorescence mapping technology was employed. In our study, we set up four treatments, i.e., without biochar and straw (B0S0); biochar only (B1S0); straw returning only (B0S1); and biochar and straw (B1S1). Our results demonstrate that soil organic matter (SOM), available nitrogen (AN), and available potassium (AK) were increased by 34.71%, 22.96%, and 61.68%, respectively, under the B1S1 treatment compared to the B0S0 treatment. In addition, microbial carbon (MBC), dissolved organic carbon (DOC), and particulate organic carbon (POC) were significantly increased with the B1S1 treatment, by 55.13%, 15.59%, and 125.46%, respectively. The results also show an enhancement in microbial diversity, the composition of microbial communities, and the degree of soil humification with the application of biochar and straw. Moreover, by comparing the differences in soil fertility, DOM components, and other indicators under different treatments, the combined treatments of biochar and straw had a more significant positive impact on paddy soil fertility compared to biochar. In conclusion, our study revealed the combination of straw incorporation and biochar application has significant impacts and is considered an effective approach to improving soil fertility.

Synthesis and Characterization of Boronate Affinity Three-Dimensionally Ordered Macroporous Materials.

Sample pretreatment is a key step for qualitative and quantitative analysis of trace substances in complex samples. Cis-dihydroxyl (cis-diol) group-containing substances exist widely in biological samples and can be selectively bound by boronate affinity adsorbents. Based on this, in this article, we proposed a simple method for the preparation of novel spherical three-dimensionally ordered macropore (3DOM) materials based on a combination of the boronate affinity technique and colloidal crystal template method. The prepared 3DOM materials were characterized using Fourier transform-infrared spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and thermo-gravimetric analysis, and results showed that they possessed the characteristics of a high specific surface area, high porosity, and more boronic acid recognition sites. The adsorption performance evaluation results showed that the maximum adsorption capacity of the boron affinity 3DOMs on ovalbumin (OVA) could reach to 438.79 mg/g. Kinetic and isothermal adsorption experiments indicated that the boronate affinity 3DOM material exhibited a high affinity and selectivity towards OVA and adenosine. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of the proteins in egg whites was conducted and proved that the glycoprotein in the egg whites could be separated and enriched with a good performance. Therefore, a novel boronate affinity 3DOM material a with highly ordered and interconnected pore structure was prepared and could be applied in the separation and enrichment of molecules with cis-diol groups from complex samples with a good selectivity, efficiency, and high throughput.