Water temperature governs organophosphate ester dynamics in the aquatic food chain of Poyang Lake.

Organophosphate esters (OPEs) are increasingly recognized as pervasive environmental contaminants, primarily from their extensive application in flame retardants and plasticizers. Despite their widespread presence, the intricacies of OPE bioaccumulation within aquatic ecosystems remain poorly understood, particularly the environmental determinants influencing their distribution and the bioaccumulation dynamics across aquatic food chains. Here we show that water temperature plays a crucial role in modulating the dispersion of OPE in the aquatic environment of Poyang Lake. We quantified OPE concentrations across various matrices, uncovering levels ranging from 0.198 to 912.622 ng L-1 in water, 0.013-493.36 ng per g dry weight (dw) in sediment, 0.026-41.92 ng per g wet weight (ww) in plankton, 0.13-2100.72 ng per g dw in benthic invertebrates, and 0.31-3956.49 ng per g dw in wild fish, highlighting a pronounced bioaccumulation gradient. Notably, the intestines emerged as the principal site for OPE absorption, displaying the highest concentrations among the seven tissues examined. Among the various OPEs, tris(chloroethyl) phosphate was distinguished by its significant bioaccumulation potential within the aquatic food web, suggesting a need for heightened scrutiny. The propensity for OPE accumulation was markedly higher in benthic invertebrates than wild fish, indicating a differential vulnerability within aquatic biota. This study lays a foundational basis for the risk assessment of OPEs as emerging contaminants and underscores the imperative to prioritize the examination of bioaccumulation effects, particularly in benthic invertebrates, to inform future environmental safeguarding strategies.

Concentration levels and ecological risk assessment of typical organophosphate esters in representative surface waters of a megacity.

Organophosphate esters (OPEs) have been widely used as flame retardants and plasticizers in consumer and industrial products. They have been found to have numerous exposure hazards. Recently, several OPEs have been detected in surface waters around the world, which may pose potential ecological risks to freshwater organisms. In this study, the concentration, spatial variation, and ecological risk of 15 OPEs in the Beiyun and Yongding rivers were unprecedentedly investigated by the ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) and risk quotient (RQ) method. The result showed that triethyl phosphate (TEP), tri (2-chloroisopropyl) phosphate (TCPP) were the most abundant OPEs with average concentrations of 55.53 ng/L and 42.29 ng/L, respectively. The concentrations of OPEs in the Beiyun River are higher than in the Yongding River, and their levels were higher in densely populated and industrial areas. The risk assessment showed that there was insignificant from OPEs to freshwater organisms in these rivers (RQs <0.1). The risk was higher downstream than upstream, which was related to human-intensive industrial activities downstream in the Yongding River. The ecological risk of OPEs in surface waters worldwide was estimated by joint probability curves (JPCs), and the result showed that there was a moderate risk for tri (2-chloroethyl) phosphate (TCEP), a low risk for trimethyl phosphate (TMP), and insignificant for other OPEs. In addition, the QSAR-ICE-SSD model was used to calculate the hazardous concentration for 5% (HC5). This result validated the feasibility and accuracy of this model in predicting acute data of OPEs and reducing biological experiments on the toxicity of OPEs. These results revealed the ecological risk of OPEs and provided the scientific basis for environmental managers.

Leaching behaviors of dissolved organic matter from face masks revealed by fluorescence EEM combined with FRI and PARAFAC.

Despite numerous studies investigating the occurrence and fate of microplastics, no effort has been devoted toward exploring the characteristics of dissolved organic matter (DOM) leached from face masks mainly made of plastics and additives used in large quantities during the COVID-19 pandemic. By using FTIR, UV-vis, fluorescence EEM coupling with FRI and PARAFAC, and kinetic models of leaching experiments, we explored the leaching behaviors of face mask-derived DOM (FM-DOM) from commonly used face masks including N95, KN95, medical surgical masks, etc. The concentration of FM-DOM increased quickly at early 0-48 h and reached equilibrium at about 48 h measured in terms of dissolved organic carbon and fluorescence intensity. The protein-like materials ranged from 80.32 % to 89.40 % of percentage fluorescence response (Pi,n) were dominant in four types of FM-DOM analyzed by fluorescence EEM-FRI during the leaching experiments from 1 to 360 h. Four fluorescent components were identified, which included tryptophan-like components, tyrosine-like components, microbial protein-like components, and fulvic-like components with fluorescence EEM-PARAFAC models. The multi-order kinetic model (Radj2 0.975-0.999) fitted better than the zero-order and first-order kinetic model (Radj2 0.936-0.982) for all PARAFAC components of FM-DOM based on equations derived by pseudo kinetic models. The leaching rate constants (kn) ranged from 0.058 to 30.938 and the half-life times (T1/2) ranged from 2.73 to 24.87 h for four FM-DOM samples, following the solubility order of fulvic-like components (C4) > microbial protein-like components (C3) > tryptophan-like components (C1) > tyrosine-like components (C2) for FM-DOM from four types of face masks during the leaching experiment from 0 to 360 h. These novel findings will contribute to the understanding of the underappreciated environment impact of face masks in aquatic ecosystems.

Molecular-level insights into the temperature-dependent formation dynamics and mechanism of water-soluble dissolved organic carbon derived from biomass pyrolysis smoke.

Water soluble organic carbon (WSOC) derived from biomass pyrolytic smoke is deposited through atmospheric aerosols, negatively affecting aquatic ecological quality and safety. However, the temperature-dependent molecular diversity and dynamic formation of smoke-derived WSOC remain poorly understood in water. Herein, we explored the molecular-level formation mechanism of pyrolytic smoke-derived WSOC in water to explain the evolution, heterogeneous correlations, and sequential responses of molecules and functional groups to increasing pyrolysis temperature. Two-dimensional correlation spectroscopy was used to innovatively establish the characteristic correlations between spectroscopy and Fourier transform-ion cyclotron resonance mass spectrometry. Temperature-dependent formation of WSOC exhibited diversity in absorbance/fluorescent components, unique/common molecules, and their chemical parameters, showing the simultaneous formation and degradation reactions. The common WSOC molecules with lower and higher degrees of oxidation showed significant positive and negative correlations with the fluorescent components, respectively. The primary sequential response of WSOC molecules to increasing pyrolysis temperature (lignin-like molecules â†’ unsaturated hydrocarbons, condensed aromatic molecules â†’ lipid-like/aliphatic-/peptide-like molecules) corresponded to the temperature response of functional groups (carboxylic/alcoholic â†’ polysaccharides â†’ aromatics/amides/phenolic/aliphatic groups), demonstrating well synergistic relationships between them. These novel findings will contribute to the comprehensive understanding and assessments of potential environmental behavior or risks of WSOC in aquatic ecosystems.

Study on the removal of iron (II) and manganese (II) in acidic mine drainage by red mud: Performance and mechanism.

Red mud is an environmental burden during the alumina production process. To mitigate the hazards associated with red mud storage, this study investigated the utilization of alkaline red mud as a treatment agent for acidic mine drainage (AMD) with high concentrations of Fe(II) and Mn(II). This study explored the influence of reaction times, addition amounts of red mud, and pH values on the removal efficiency of Fe (II) and Mn(II) from high-concentration AMD. Various parameters such as suspended solids levels, effluent pH, and zeta potentials were measured to meet discharge standards. The adsorption mechanism of red mud was examined using SEM, XRD, EDX, XPS, and 3D-EEM analysis. Optimal conditions were determined as a reaction time of 2 h, pH value of 5.01 and the addition of 100 g/L red mud, achieving effective removal of Fe(II) (reduced from 1000 to 0.224 mg/L) and Mn (II) (reduced from 20 to 1.03 mg/L). The treated AMD meets discharge standards with reduced suspended matter content of 37.4 mg/L. These findings provided valuable insights for the utilization of red mud waste in engineering applications.

Predicting the acute toxicity of organophosphate esters (OPEs) to aquatic organisms by modelling the structure-toxicity relationships using partial least square regression.

Organophosphate esters (OPEs) have been used worldwide as organophosphate flame retardants (OPFRs) since brominated flame retardants (BFRs) were banned. Due to the toxicity of these OPEs, environmental concerns and ecological risks arose. However, there are still large gaps in the understanding of their toxicity to organisms and the mechanisms of toxicity. After collecting the existing toxicity information and obtaining molecular descriptors of OPEs, a partial least square (PLS) regression model was used in this study to quantify the structure-toxicity relationships of OPEs. Based on the regression results, the acute toxicity of the remaining OPEs lacking acute toxicity data was predicted, and the risk level of total common OPEs was classified. The acute toxicity of 15 chemicals was collected, and >1660 molecular structure descriptors were obtained. The cross-validation results of the partial least square regression indicated that two principal components met the regression requirements with the selected features, and the regression equations of these chemicals were generated with selected molecular descriptors. The influence of physicochemical properties, such as hydrophobicity/molecular weight, in traditional perception of OPE toxicity was not that obvious, and acute toxicity was mainly influenced by the autocorrelation coefficients. However, the regression results indicated that the correlation between autocorrelation coefficients calculated based on different physicochemical properties and toxicity was different. According to the prediction result based on PLS regression, CDP may pose a high risk and halogenated alkyl-substituted OPEs such as TCEP may be less toxic. The results of the present study may help inform the environmental management and risk assessment of emerging chemicals such as OPEs.

Construction of a transition-metal sulfide heterojunction photocatalyst driven by a built-in electric field for efficient hydrogen evolution under visible light.

Photocatalytic H2 evolution is of prime importance in the energy crisis and in lessening environmental pollution. Adopting a single semiconductor as a photocatalyst remains a formidable challenge. However, the construction of an S-scheme heterojunction is a promising method for efficient water splitting. In this work, CdS nanoparticles were loaded onto NiS nanosheets to form CdS/NiS nanocomposites using hollow Ni(OH)2 as a precursor. The differences in the Fermi energy levels between the two components of CdS and NiS resulted in the formation of a built-in electric field in the nanocomposite. Density functional theory (DFT) calculations reveal that the S-scheme charge transfer driven by the built-in electric field can accelerate the effective separation of photogenerated carriers, which is conducive to efficient photocatalytic hydrogen evolution. The hydrogen evolution rate of the optimized photocatalyst is 39.68 mmol·g-1 h-1, which is 6.69 times that of CdS under visible light. This work provides a novel strategy to construct effective photocatalysts to relieve the environmental and energy crisis.

Distribution and Characterization of Typical Antibiotics in Water Bodies of the Yellow River Estuary and Their Ecological Risks.

A total of 34 antibiotics from five major classes of antibiotics, including macrolides, sulfonamides, quinolones, tetracyclines and chloramphenicol, were considered as contaminants, considering the Yellow River Estuary as the study area. The distribution, sources and ecological risks of typical antibiotics in the Yellow River Estuary were investigated using an optimized solid-phase extraction pre-treatment and an Agilent 6410B tandem triple-quadrupole liquid chromatography-mass spectrometer for antibiotic detection. The results show that antibiotics were widely present in the water bodies of the Yellow River Estuary, with 14 antibiotics detected to varying degrees, including a high detection rate for lincomycin hydrochloride. Farming wastewater and domestic sewage were the primary sources of antibiotics in the Yellow River Estuary. The distribution characteristics of antibiotics in the study area were linked to the development of farming and social activities. The ecological risk evaluation of 14 antibiotics in the Yellow River Estuary watershed showed that clarithromycin and doxycycline hydrochloride were present at medium-risk levels, and lincomycin hydrochloride, sulfamethoxazole, methomyl, oxifloxacin, enrofloxacin, sulfadiazine, roxithromycin, sulfapyridine, sulfadiazine and ciprofloxacin were present at low-risk levels in the samples collected from water bodies of the Yellow River Estuary. This study provides novel, beneficial information for the assessment of the ecological risk presented by antibiotics in the Yellow River Estuary water bodies and provides a scientific basis for future antibiotic pollution control in the Yellow River Basin.

Temperature-Dependent Molecular Evolution of Biochar-Derived Dissolved Black Carbon and Its Interaction Mechanism with Polyvinyl Chloride Microplastics.

Biochar-derived dissolved black carbon (DBC) molecules are dependent on the BC formation temperature and affect the fate of emerging contaminants in waters, such as polyvinyl chloride microplastic (MPPVC). However, the temperature-dependent evolution and MPPVC-interaction of DBC molecules remain unclear. Herein, we propose a novel DBC-MPPVC interaction mechanism by systematically interpreting heterogeneous correlations, sequential responses, and synergistic relationships of thousands of molecules and their linking functional groups. Two-dimensional correlation spectroscopy was proposed to combine Fourier transform-ion cyclotron resonance mass spectrometry and spectroscopic datasets. Increased temperature caused diverse DBC molecules and fluorophores, accompanied by molecular transformation from saturation/reduction to unsaturation/oxidation with high carbon oxidation states, especially for molecules with acidic functional groups. The temperature response of DBC molecules detected via negative-/positive-ion electrospray ionization sequentially occurred in unsaturated hydrocarbons → lignin-like → condensed aromatic → lipid-/aliphatic-/peptide-like → tannin-like → carbohydrate-like molecules. DBC molecular changes induced by temperature and MPPVC interaction were closely coordinated, with lignin-like molecules contributing the most to the interaction. Functional groups in DBC molecules with m/z < 500 showed a sequential MPPVC-interaction response of phenol/aromatic ether C-O, alkene C═C/amide C═O → polysaccharides C-O → alcohol/ether/carbohydrate C-O groups. These findings help to elucidate the critical role of DBCs in MP environmental behaviors.

Influence of fulvic acid sub-fractions on aggregation kinetics of graphene oxide in aqueous environments.

Fulvic acid (FA) can affect the dispersion of graphene oxide (GO) in aquatic environments, however, the possible mechanisms remain unclear. Dynamic light scattering techniques combined with a multiple regression model were applied to explore the influence of FA sub-fractions (FApH3 - FApH13) on the aggregation kinetics of GO in aqueous environments. The ratios of critical coagulation concentration (CCC) values were CCCNa: CCCMg: CCCLa: CCCCe = 1:2-5.15:3-7.31:3-7.35, which were consistent with the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory and Schulze-Hardy rules. The GO remained stable at pH 3-10 and aggregated at pH < 3 or pH > 10, and its critical coagulation pH values were 1.44 and 12.25 with 10 mM NaCl as background. The CCC values of GO in the presence of FApH3 - FApH13 were greater than those in the absence of FA sub-fractions. The ratios of CCC values of GO (r) increased in the presence of FA sub-fractions in the order of FApH13 > FApH9 > FApH7 > FApH5 > FApH3 and ranged from 1.01 to 2.15 for certain metal ions including Na+, Mg2+, La3+, and Ce3+. The CCC values of GO were significantly related to C, H, O, N, S, H/C, O/C, carboxylic C, and carbonyl C of FA sub-fractions (P < 0.05), respectively, and could be predicted using the multiple linear regression eq. CCC = Z-n (98.959- 60.911 ∗ O/C + 4.799 ∗ O-alkyl C - 0.845 ∗ aromatic C - 6.237 ∗ carbonyl C). The predicted CCC values for GO were within 90 % prediction intervals, and the average error of the CCC values was 3.3 % and R2 = 0.986. This investigation is expected to provide a scientific basis for the transport and ecotoxicity of GO in environments.

Heterogeneous Dynamic Behavior and Synergetic Evolution Mechanism of Internal Components and Released Gases during the Pyrolysis of Aquatic Biomass.

Evolution of gaseous contaminants from biomass pyrolysis has drawn increasing attention. However, the thermal degradation, dynamics, and synergetic evolution mechanisms during real-time biomass pyrolysis remain unclear. Herein, a novel method using thermogravimetry-Fourier transform infrared spectrometry-gas chromatography/mass spectrometry (TG-FTIR-GC/MS) combined with thermal kinetics and two-dimensional correlation spectroscopy was proposed to explore the chemical properties and temperature response mechanisms of gaseous species released during Phragmites communis (PC) and Typha angustifolia (TA) pyrolysis. The thermal degradation mechanisms of PC/TA pyrolysis were mainly associated with the sigmoidal rate and random nucleation mechanisms. The formation intensities of alcohols/ethers, phenols/esters, acids, aldehydes, and ketones were higher during low-temperature TA pyrolysis and high-temperature PC pyrolysis. The average carbon oxidation state (OS¯C) of gaseous species mainly ranged from -1.5 to -0.5, and the OS¯C slope of most gaseous species was greater than -2.0, which was related to the reduction of aldehyde/ketone groups. Two-dimensional (2D)-TG-FTIR-COS analysis revealed that the sequential temperature response of gaseous species followed: acids → phenols, esters → aldehydes → hydrocarbons → alcohols, ethers → aromatics during PC/TA pyrolysis. The establishment of relationships between the sequential response of gases and degraded components provides an important basis for online monitoring/recovery of gaseous contaminants during biomass pyrolysis.

Organophosphate esters cause thyroid dysfunction via multiple signaling pathways in zebrafish brain.

Organophosphate esters (OPEs) are widespread in various environmental media, and can disrupt thyroid endocrine signaling pathways. Mechanisms by which OPEs disrupt thyroid hormone (TH) signal transduction are not fully understood. Here, we present in vivo-in vitro-in silico evidence establishing OPEs as environmental THs competitively entering the brain to inhibit growth of zebrafish via multiple signaling pathways. OPEs can bind to transthyretin (TTR) and thyroxine-binding globulin, thereby affecting the transport of TH in the blood, and to the brain by TTR through the blood-brain barrier. When GH3 cells were exposed to OPEs, cell proliferation was significantly inhibited given that OPEs are competitive inhibitors of TH. Cresyl diphenyl phosphate was shown to be an effective antagonist of TH. Chronic exposure to OPEs significantly inhibited the growth of zebrafish by interfering with thyroperoxidase and thyroglobulin to inhibit TH synthesis. Based on comparisons of modulations of gene expression with the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes databases, signaling pathways related to thyroid endocrine functions, such as receptor-ligand binding and regulation of hormone levels, were identified as being affected by exposure to OPEs. Effects were also associated with the biosynthesis and metabolism of lipids, and neuroactive ligand-receptor interactions. These findings provide a comprehensive understanding of the mechanisms by which OPEs disrupt thyroid pathways in zebrafish.

A QSAR-ICE-SSD model prediction of the PNECs for alkylphenol substances and application in ecological risk assessment for rivers of a megacity.

Alkylphenols (APs) are ubiquitous and generally present in higher residue levels in the environment. The present work focuses on the development of a set of in silico models to predict the aquatic toxicity of APs with incomplete/unknown toxicity data in aquatic environments. To achieve this, a QSAR-ICE-SSD model was constructed for aquatic organisms by combining quantitative structure-activity relationship (QSAR), interspecies correlation estimation (ICE), and species sensitivity distribution (SSD) models in order to obtain the hazardous concentrations (HCs) of selected APs. The research indicated that the keywords "alkylphenol" and "nonylphenol" were most commonly studied. The selected ICE models were robust (R2: 0.70-0.99; p-value < 0.01). All models had a high reliability cross- validation success rates (>75%), and the HC5 predicted with the QSAR-ICE-SSD model was 2-fold than that derived with measured experimental data. The HC5 values demonstrated nearly linear decreasing trend from 2-MP to 4-HTP, while the decreasing trend from 4-HTP to 4-DP became shallower, indicates that the toxicity of APs to aquatic organisms increases with the addition of alkyl carbon chain lengths. The ecological risks assessment (ERA) of APs revealed that aquatic organisms were at risk from exposure to 4-NP at most river stations (the highest risk quotient (RQ) = 1.51), with the highest relative risk associated with 2.9% of 4-NP detected in 82.9% of the sampling sites. The targeted APs posed potential ecological risks in the Yongding and Beiyun River according to the mixture ERA. The potential application of QSAR-ICE-SSD models could satisfy the immediate needs for HC5 derivations without the need for additional in vivo testing.

Hardness-Dependent Water Quality Criteria for Protection of Freshwater Aquatic Organisms for Silver in China.

Silver is toxic to freshwater aquatic organisms and aquatic ecosystems, and it is necessary to develop regional water quality criteria (WQC) for silver to protect the freshwater aquatic organisms in China. The toxicity database of silver for freshwater aquatic organisms involved 121 acute toxicity values for 35 species (6 phyla and 27 families) and 15 chronic toxicity values for 4 species (2 phyla and 4 families). Teleost fish showed the most sensitivity to silver after both short-term and long-term exposure. Significant correlations between the natural logarithms of hardness and the natural logarithms of acute silver toxicity were found for Daphnia magna, Oncorhynchus mykiss, and Pimephales promelas. The criterion maximum concentration (CMC) was calculated by the species sensitivity distribution method with sigmoid as the best fitting model (Adj R2 0.9797), and the criterion continuous concentration (CCC) was obtained by the acute-to-chronic ratio method. The CMC and CCC of silver were e1.58ln(HCaCO3)-8.68, and e1.58ln(HCaCO3)-10.28 respectively, in China, with water hardness (HCaCO3, mg/L) as an independent variable. This research can provide a basis and reference for the management of silver to protect freshwater aquatic organisms in China.

Dynamic Evolution and Covariant Response Mechanism of Volatile Organic Compounds and Residual Functional Groups during the Online Pyrolysis of Coal and Biomass Fuels.

Volatile organic compound (VOC) emissions from pyrolysis of widely used biomass are expected to increase significantly under the carbon neutrality target. However, the dynamic emissions and evolution mechanism of biomass-VOCs remain unclear, hindered by complex reactions and offline measurements. Here, we propose a novel covariant evolution mechanism to interpret the emission heterogeneities, sequential temperature responses, and evolved correlations of both VOCs and residual functional groups (RFGs) during corn straw (CS), wood pellet (WP), and semibituminous coal (SBC) pyrolysis. An innovative combination of online thermogravimetric-Fourier transform infrared-gas chromatography/mass spectrometry and two dimensional-correlation spectroscopy was applied. The relative percentages of CS/WP-VOCs were higher than those of SBC-VOCs, and most VOCs tended to have relatively small carbon skeletons as the average carbon oxidation state increased. With the temperature increased from low to high during CS/WP pyrolysis, the primary sequential response of VOCs (acids → phenols/esters → alcohols/ethers/aldehydes/ketones → hydrocarbons/aromatics) corresponded to the RFG response (hydroxyl groups → -CH3/-CH2-/-CH groups → aliphatic ethers and conjugated ketones). Compared with the relative regularity for CS/WP responses, the gas-solid products from SBC pyrolysis exhibited complex temperature-dependent responses and high oxidation-induced variability. These insights provide favorable strategies for the online monitoring system to facilitate priority removal of coal and biomass fuels-VOCs.

General Challenges and Recommendations for the Water Quality Criteria of Endocrine Disrupting Chemicals (EDCs).

Water quality criteria (WQC) play an important role in the environmental management of pollutants in different countries or institutions. It has been found that endocrine disrupting chemicals (EDCs) can potentially alter functions of the endocrine system and consequently cause adverse effects in aquatic organisms. Therefore, the complicated modes of action and mechanisms of EDCs should be carefully considered in WQC studies. For example, the research regarding the WQC derivation of EDCs should prioritize sensitive aquatic species in consideration of the WQC derivation. Second, the chronic toxicity of EDCs should be of utmost concern. In addition, the appropriate effects and endpoints of EDCs should be carefully selected for the WQC derivation. Moreover, it was pointed out that some new methods should be taken into consideration in the WQC studies of EDCs in the near future.

Derivation of water quality criteria for glyphosate and its formulations to protect aquatic life in China.

Extensive use of the herbicide glyphosate leads to a high detection rate in the environment and potential risks to nontarget aquatic life. China ranks first globally in the production and consumption of glyphosate, but there are no glyphosate water quality criteria (WQCs) for protecting aquatic life. Here, data on the acute and chronic toxicity of glyphosate and glyphosate-based formulations (GBFs) to freshwater aquatic life were collected and screened. Significant differences in species sensitivity distributions (SSDs) and toxicity values for acute or chronic toxicity were found between glyphosate and GBFs. The hazardous concentrations for 5% of species (HC5) of glyphosate or GBFs between native and nonnative species were different, and native species were found to be more sensitive to the toxicity of glyphosate. The acute and chronic WQCs derived with the SSD method for glyphosate based on the toxicity data for native species in China were 3.35 and 0.26 mg/L, respectively, and those found for GBFs were 0.21 and 0.005 mg/L, respectively. The WQCs in this study were quite different from those estimated using similar statistical extrapolation methods in other countries, which reflects the differences in species sensitivity to glyphosate toxicity in different regions. The hazard quotients (HQs) were calculated based on the WQCs and concentrations of glyphosate in some surface waters in China and indicated that glyphosate exhibits medium or high hazard risk in some samples of Tai Lake, surface water in Guiyang, fishpond water in Chongqing, rural drinking water, and surface water and reservoir water in Henan Province. The WQCs of glyphosate and GBFs have scientific significance for the exposure and pollution control of herbicide formulations and the protection of aquatic life in China.

Molecular characteristics of biochar-derived organic matter sub-fractions extracted by ultrasonication.

Biochar-derived organic matter is key to carbon dynamics and pollutant transport in soils remediated by biochar. A limited understanding of the molecular composition of biochar-derived organic matter limits the ability to accurately predict the chemical cycle within soil and how biochar-derived organic matter will interact with contaminants. To describe the relatively comprehensive structure information of soybean straw biochar-extractable organic matter (BEOM) at the molecular level, we used solvents of different polarities, namely, petroleum ether (PE), carbon disulfide (CS2), methanol (CH3OH) and acetone (CH3COCH3), to extract organic samples from soybean straw biochar and used Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) for analysis. We found that a high percentage of unique molecular formulas were extracted by each solvent. This molecular diversity is mainly due to variance in solvent polarity and various intermolecular bonds destroyed by different solvents. The molecular signatures of the sub-fractions reveal that some recalcitrant BEOM sub-fractions will be easily released in the environment and preserved for a long time in the soil environment, while the majority of the labile BEOM sub-fractions tend to be preserved in the biochar itself. In addition, the most readily available organic N and S in biochar will be primarily released. These results reveal that biochar could provide nutrients efficiently and maintain soil organic carbon over the long term, suggesting that biochar is a promising material for soil improvement. By using high-resolution mass spectrometry, we revealed the BEOM signature at the molecular level in various possible environmental processes, which provides a theoretical basis for further research on the interactions between BEOM and organic contaminants.

Effects of Different Delocalized π-Conjugated Systems Towards the TiO2-Based Hybrid Photocatalysts.

Modulating the structure of a photocatalyst at the molecular level can improve the photocatalytic efficiency and provides a guide for the synthesis of highly qualified photocatalysts. In this study, TiO2 was modified by various organic compounds to form different TiO2-based hybrid photocatalysts. 1,10-Phenanthroline (Phen) is an organic material with delocalized π-conjugated systems. It was used to modify TiO2 to form the hybrid photocatalyst Phen/TiO2. Furthermore, 1,10-phenanthrolin-5-amine (Phen-NH2) and 1,10-phenanthroline-5-nitro (Phen-NO2) were also used to modify TiO2 to form NH2-Phen/TiO2 and NO2-Phen/TiO2, respectively. The samples of TiO2, Phen/TiO2, NO2-Phen/TiO2, and NH2-Phen/TiO2 were carefully characterized, and their photocatalytic performance was compared. The results indicated that the photocatalytic efficiency followed the order of NH2-Phen/TiO2 > NO2-Phen/TiO2 > Phen/TiO2 > TiO2. It could be found that modifying TiO2 with different organic compounds containing delocalized π-conjugated systems could enhance the photocatalytic ability; furthermore, the level of this enhancement could be modulated by different delocalized π-conjugated systems.

Novel Insights into the Molecular-Level Mechanism Linking the Chemical Diversity and Copper Binding Heterogeneity of Biochar-Derived Dissolved Black Carbon and Dissolved Organic Matter.

Biochar-derived dissolved black carbon (DBC) varies in chemical composition and significantly affects the environmental fate of metal ions. However, the intrinsic molecular composition of DBC fractions and their molecular interaction mechanisms with metal ions remain unclear. We propose a novel, molecular-level covariant binding mechanism to comparatively interpret the heterogeneities, active sites, and sequential responses of copper binding with molecular compounds in DBC and natural dissolved organic matter (DOM). Relatively large proportions of lipid/aliphatic/peptide-like compounds with low mass distributions and lignin-like compounds with oxidized/unsaturated groups existed in acidic- and alkaline-extracted DBC, respectively. A larger percentage of tannin-like/condensed aromatic compounds and higher average conditional stability constants (logK̅Cu) of visible fluorescent components were found for DOM than for DBC. Overall, 200-320 Da and 320-480 Da molecular components contributed significantly to the logK̅Cu values of UVA and visible fluorescent components, respectively, in DBC/DOM. Nitrogenous groups likely exhibited stronger binding affinities than phenolic/carboxylic groups. The sequential copper-binding responses of molecular compounds in DBC/DOM generally followed the order lipid/aliphatic/peptide-like compounds → tannin-like compounds → condensed aromatic compounds. These insights will improve the prediction of the potential effects of DBC on various contaminants and the risks of biochar application to ecosystems.