Spectral and molecular insights into the characteristics of dissolved organic matter in nitrate-contaminated groundwater.

The characteristics of dissolved organic matter (DOM) serve as indicators of nitrate pollution in groundwater. However, the specific DOM components associated with nitrate in groundwater systems remain unclear. In this study, dual isotopes of nitrate, three-dimensional Excitation emission matrices (EEMs) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) were utilized to uncover the sources of nitrate and their associations with DOM characteristics. The predominant nitrate in the targeted aquifer was derived from soil organic nitrogen (mean 46.0%) and manure &sewage (mean 34.3%). The DOM in nitrate-contaminated groundwater (nitrate-nitrogen >20 mg/L) exhibited evident exogenous characteristics, with a bioavailable content 2.58 times greater than that of uncontaminated groundwater. Regarding the molecular characteristics, DOM molecules characterized by CHO + 3N, featuring lower molecular weights and H/C ratios, indicated potential for mineralization, while CHONS formulas indicated the exogenous features, providing the potential for accurate traceability. These findings provided insights at the molecular level into the characterization of DOM in nitrate-contaminated groundwater and offer scientific guidance for decision-making regarding the remediation of groundwater nitrate pollution.

Insights into the role of the microbial community lifestyle strategies in variations of the dissolved organic matter molecular composition along an effluent-dominated river.

Urbanization has dramatically changed the quality and quantity of dissolved organic matter (DOM) fluxes in rivers, thereby affecting the diversity and lifestyle strategies of microbial communities. However, relationships between DOM molecular composition and microbial lifestyle strategies in effluent-dominated rivers are poorly understood. Herein, we investigated the variations in DOM structure and composition of an effluent-dominated river and further revealed how these changes alter the abundance and lifestyle strategies of microbial communities. Results demonstrated that macromolecular (MW > 35 kDa) humic-like substances constituted the major components of effluent-dominated riverine DOM. Also, due to the degradation of humic-like substances, the accumulation of protein-like substances was observed from upstream to downstream areas, corresponding to an apparent decrease in overall aromaticity. The abundance of bacterial, Actinobacteria, and eukaryotic was higher in the upstream and midstream areas but relatively lower in the downstream area. The response of bacterial and Actinobacteria communities to the changes in DOM composition was more prominent as compared to that of eukaryotic. Based on multivariate statistical analysis, the decrease in aromatic components (MW > 35 kDa) was mainly attributed to the degradation of Proteobacteria and Actinobacteria (K-strategists), resulting in a decrease in their relative abundance along the river course. Proteins and polysaccharides (15 kDa < MW < 35 kDa, MW < 6 kDa) were more easily utilized by Firmicutes and Bacteroidetes (r-strategists), leading to an increase in their relative abundance. With the decrease of macromolecular humic-like substances and the increase of protein-like substances, river microbial communities shifted from K-strategists to r-strategists. This work unveils the evolution of DOM in an effluent-dominated river and the influence of the degradation of macromolecular humic-like substances on r/K-strategists.

Recent progress on in-situ chemical oxidation for the remediation of petroleum contaminated soil and groundwater.

Accidental oil leaks and spills can often result in severe soil and groundwater pollution. In situ chemical oxidation (ISCO) is a powerful and efficient remediation technology. In this review, the applications and recent advances of three commonly applied in-situ oxidants (hydrogen peroxide, persulfate, and permanganate), and the gap in remediation efficiency between lab-scale and field-scale applications is critically assessed. Feasible improvements for these measures, especially solutions for the 'rebound effect', are discussed. The removal efficiencies reported in 108 research articles related to petroleum-contaminated soil and groundwater were analyzed. The average remediation efficiency of groundwater (82.7%) by the three oxidants was higher than that of soil (65.8%). A number of factors, including non-aqueous phase liquids, adsorption effect, the aging process of contaminants, low-permeability zones, and vapor migration resulted in a decrease in the remediation efficiency and caused the residual contaminants to rebound from 19.1% of the original content to 57.7%. However, the average remediation efficiency of ISCO can be increased from 40.9% to 75.5% when combined with other techniques. In the future, improving the utilization efficiency of reactive species and enhancing the contact efficiency between oxidants and petroleum contaminants will be worthy of attention. Multi-technical combinations, such as the ISCO coupled with phase-transfer, viscosity control, controlled release or natural attenuation, can be effective methods to solve the rebound problem.

Novelelectronic health records applied for prediction of pre-eclampsia: Machine-learning algorithms.

OBJECTIVE: To predict risk of pre-eclampsia (PE) in women using machine learning (ML) algorithms, based on electronic health records (EHR) collected at the early second trimester. STUDY DESIGN: A total of 3759 cases of pregnancy who received antenatal care at Xinhua hospital Chongming branch Affiliated to Shanghai Jiaotong University were included in this retrospective EHR-based study. Thirty-eight candidate clinical parameters routinely available at the first visit in antenatal care were collected by manual chart review. Logistic regression (LR), random forest (RF), support vector machine (SVM) and extreme gradient boosting (XGBoost) were used to construct the prediction model. Features that contributed to the model predictions were identified using XGBoost. OUTCOME MEASURES: The performance of ML models to predict women at risk of PE was quantified in terms of accuracy, precision, recall, false negative score, f1_score, brier score and the area under the receiver operating curve (auROC). RESULTS: The XGboost model had the best prediction performance (accuracy = 0.920, precision = 0.447, recall = 0.789, f1_score = 0.571, auROC = 0.955). The most predictive feature of PE development was fasting plasma glucose, followed by mean blood pressure and body mass index. An easy-to-use model that a patient could answer independently still enabled accurate prediction, with auROC of 0.83. CONCLUSION: risk of PE development can be predicted with excellent discriminative ability using ML algorithms based on EHR collected at the early second trimester. Future studies are needed to assess the real-world clinical utility of the model.

K-strategy species plays a pivotal role in the natural attenuation of petroleum hydrocarbon pollution in aquifers.

The natural attenuation of petroleum hydrocarbons is inseparable from the action of microorganisms, while the degradation methods and ecological strategies of microorganisms in petroleum-contaminated aquifers are still under debate. In the present study, 16 S rRNA sequencing and quantitative real-time polymerase chain reaction were used to assess the potential microbial degradation of petroleum hydrocarbons, and the ecological strategy of microorganisms under petroleum stress was analyzed through a co-occurrence network. The results showed that the microbial community in sediments exhibit higher efficiency and stability and stronger ecological function than that in groundwater. Keystone species coordinated with the community to execute ecosystem processes and tended to choose a K-strategy to survive, with the aquifer sediment being the main site of petroleum hydrocarbon degradation. Under natural conditions, the presence of petroleum hydrocarbons at concentrations higher than 126 µg kg-1 and 5557 µg kg-1 was not conducive to the microbial degradation of polycyclic aromatic hydrocarbons and alkanes, respectively. These results can be used as a reference for an enhanced bioremediation of contaminated groundwater. Overall, these findings provide support to managers for developing environmental management strategies.

Dissolved Silicate Enhances the Oxidation of Chlorophenols by Permanganate: Important Role of Silicate-Stabilized MnO2 Colloids.

Dissolved silicate is an important background constituent of natural waters, but there is little clarity regarding the effect of silicate on the oxidizing capability of permanganate (Mn(VII)) and on its efficiency for remediation applications. In the present study, we found that dissolved silicate, metasilicate or disilicate (DS), could significantly promote the oxidation of 2,4-dichlorophenol (2,4-DCP) by Mn(VII), and the extent of the promoting effect was even more evident than that of pyrophosphate (PP). The experiments showed that, unlike PP, DS was not capable of coordinating with Mn(III) ions, and the promoting effect of DS was not due to the oxidizing capability of complexed Mn(III). Instead, DS ions, as a weak base, could combine with the hydroxyl groups of MnO2 via hydrogen bonding to limit the growth of colloidal MnO2 particles. The DS-stabilized colloidal MnO2 particles, with hydrodynamic diameters less than 100 nm, could act as catalysts to enhance the oxidation of 2,4-DCP by Mn(VII). The best promoting effect of DS on the performance of Mn(VII) oxidant was achieved at the initial solution pH of 7, and the coexisting bicarbonate ions further improved the oxidation of 2,4-DCP in the Mn(VII)/DS system. Sand column experiments showed that the combined use of Mn(VII) and DS additive could mitigate the problem of permeability reduction of sand associated with the retention of MnO2 particles. This study not only deepens our understanding on the role of dissolved silicate in a Mn(VII) oxidation process but also provides an effective and green method to enhance the oxidizing capacity of Mn(VII)-based treatment systems.

Municipal wastewater effluent influences dissolved organic matter quality and microbial community composition in an urbanized stream.

Dissolved organic matter (DOM) from wastewater treatment plant (WWTP) effluent poses serious threats to the receiving aqueous ecosystems and their microbial communities. However, the correlation between effluent-derived DOM and microbial community diversity in urbanized rivers is still poorly understood. In this study, the response relationship between the microbial community dynamics and the DOM evolution process in the effluent-dominated Xiaohe River was revealed. The results showed that macromolecular humic acids were the main components of DOM in this river with more carboxylic acid groups and humic-like acid substances found upstream and protein-like substances dominated downstream. The bacterial abundance in the upstream section of Xiaohe River was low, while its community structure was unstable but exhibited good uniformity, and the bacterial diversity in the downstream was rich. The response of bacterial and eukaryotic communities to WWTP effluent was weak, while that of Actinobacteria to WWTP effluent was more prominent. Furthermore, different microbial communities were affected by different compositions and structure of DOM in the effluent of WWTP. The protein-like components in DOM had the most profound impact on the microbial community, followed by polysaccharides and components rich in hydroxyl and amino functional groups. The study grasped the migration and evolution of DOM in rivers with unconventional water recharge, and revealed their diverse effects on microbial community in urbanized rivers.

Redox properties and dechlorination capacities of landfill-derived humic-like acids.

Electron transfer capacities (ETC) of humic-like acids (HLA) and their effects on dechlorination are dependent on their redox-active properties. Aging and minerals can affect the chemical compositions and structures of HLA. However, the underlying mechanism and the impacts on the dechlorination capacities of HLA are poorly understood. We investigated how redox properties change in association with the intrinsic chemical natures and exterior minerals of the HLA extracted from landfilled solid wastes. Furthermore, the ETC of the landfill-derived HLA could be strengthened by increasing landfill age and demineralization, thereby facilitating the dechlorination of pentachlorophenol (PCP). The HLA molecules started to polymerize aromatic macromolecules during landfilling, leading to an increase in ETC and dechlorination capacities. Macromolecular HLA were dissociated to smaller molecules and exposed more aromatic and carboxyl groups when separated from minerals, which enhanced the ETC and the dechlorination abilities of the HLA. Microbial-mediated dechlorination was an effective way to degrade PCP, and almost 80% of the PCP was transformed after 40 days of demineralized HLA and Shewanella oneidensis MR-1 incubation. The demineralization and aging further facilitated the microbial-mediated PCP dechlorination. The findings provide a scientific base for improving in-situ bioremediation of chlorinated compound-contaminated soils using freshly synthesized HLA.

Redox properties of compost-derived organic matter and their association with polarity and molecular weight.

Compost-derived dissolved organic matter (DOM), which has a wide distribution of molecular weight (MW) and polarity, has a potential application in the remediation of the contaminated soil due to its redox-active functional groups. Composting treatment can change the MW and polarity of the DOM through microbial transformation and degradation. However, the relationship between the redox properties of compost-derived DOM and its MW and polarity is still unclear. DOM was extracted from municipal solid wastes with different composting times in this study, and it was further fractionated into humic acids (HA), fulvic acids (FA) and hydrophilic (HyI) fractions based on its hydrophobicity and XAD-8 resin. Electron transfer capacities [including electron accepting capacities (EAC) and electron donating capacities (EDC)] of the HA, FA and HyI fractions and their associations with polarity and MW were studied. The results showed that the EAC of the HA, FA and HyI all increased after composting. The EDC of the HA and HyI exhibited an increasing trend as well, though that of the FA decreased remarkably after composting. The MW, polarity and redox-active functional groups of the HA, FA and HyI fractions were determined using high performance liquid chromatography and excitation-emission matrix fluorescence spectra coupled with parallel factor analysis. The result showed that the quinone-like groups were mainly detected in the medium MW and transphilic sub-fractions of the HA, FA and HyI, and were the main functional groups responsible for the EAC. The low MW sub-fractions, which consisted mainly of tyrosine-like matter, were the main functional components accounted for the EDC. The results advance our understanding of the influence of MW and polarity on the redox properties of organic substances, and facilitate to reveal the important redox-active functional groups when compost is utilized to remediate the contaminated soil.

[Spectral Characteristics of Dissolved Organic Matter in Landfill Groundwater].

Landfills have been the most common methods of organized waste disposal in China posing an incredible groundwater pollution threat. Dissolved organic matter (DOM) can be used to trace the source, species and migration of contaminants in groundwater, and the investigations of its composition, structure, and distribution play a role in environmental protection. This study investigated the DOM source, composition, and molecular structure in groundwater at landfills for different years of operation, and explored the dynamics of groundwater DOM evolution over time, usingmodern spectroscopy in combination with multivariate statistical analysis. The results showed that DOM in landfill groundwater was initially dominated by outputs from microbial activities, and this was followed by autogenous terrigenous input. In the early stages of landfilling, the DOM of microbial origin was significant; however, towards the late stages of landfilling, the presence of microbial DOM has weakened. The groundwater DOM with short landfill times were mainly composed of newly produced tryptophan and tyrosine, which had low humification, aromaticity, and molecular weight. Microbial activity was strong, and while there were initial, significant differences between sampling points, evidence of its presence could be used for early warning of contamination and monitoring should be conducted for its presence. Microbial activity weakened with longer landfill operation time, landfill waste tended towards stability, and the DOM in groundwater with high humification, aromaticity and molecular weight, was able to reduce the landfill impact on groundwater.

Characterization of isolated fractions of dissolved organic matter derived from municipal solid waste compost.

Understanding the heterogeneous evolution characteristics of dissolved organic matter fractions derived from compost is crucial to exploring the composting biodegradation process and the possible applications of compost products. Herein, two-dimensional correlation spectroscopy integrated with reversed-phase high performance liquid chromatography and size exclusion chromatography were utilized to obtain the molecular weight (MW) and polarity evolution characteristics of humic acid (HA), fulvic acid (FA), and the hydrophilic (HyI) fractions during composting. The high-MW humic substances and building blocks in the HA fraction degraded faster during composting than polymers, proteins, and organic colloids. Similarly, the low MW acid FA factions transformed faster than the low weight neutral fractions, followed by building blocks, and finally polymers, proteins, and organic colloids. The evolutions of HyI fractions during composting occurred first for building blocks, followed by low MW acids, and finally low weight neutrals. With the progress of composting, the hydrophobic properties of the HA and FA fractions were enhanced. The degradation/humification process of the hydrophilic and transphilic components was faster than that of the hydrophobic component. Compared with the FA and HyI fractions, the HA fraction exhibited a higher MW and increased hydrophobicity.

Investigating the composition characteristics of dissolved and particulate/colloidal organic matter in effluent-dominated stream using fluorescence spectroscopy combined with multivariable analysis.

Fluorescence excitation-emission matrix (EEM) spectroscopy combined with principal component analysis (PCA) and parallel factor analysis (PARAFAC) were used to investigate the compositional characteristics of dissolved and particulate/colloidal organic matter and its correlations with nitrogen, phosphorus, and heavy metals in an effluent-dominated stream, Northern China. The results showed that dissolved organic matter (DOM) was comprised of fulvic-like, humic-like, and protein-like components in the water samples, and fulvic-like substances were the main fraction of DOM among them. Particulate/colloidal organic matter (PcOM) consisted of fulvic-like and protein-like matter. Fulvic-like substances existed in the larger molecular form in PcOM, and they comprised a large amount of nitrogen and polar functional groups. On the other hand, protein-like components in PcOM were low in benzene ring and bound to heavy metals. It could be concluded that nitrogen, phosphorus, and heavy metals in effluent had an effect on the compositional characteristics of natural DOM and PcOM, which may deepen our understanding about the environmental behaviors of organic matter in effluent.

[Analysis of the Characteristics of Groundwater Quality in a Typical Vegetable Field, Northern China].

This study explores the impact of facility farming on the origin and composition of groundwater and on the distribution characteristics of inorganic salts, heavy metals, and dissolved organic matter in groundwater in a typical greenhouse vegetable planting area in North China plains. The methods used include conventional analysis, UV-Visible, and fluorescence spectroscopy combined with parallel factor analysis, principle components analysis, and two-dimensional (2D) hetero-spectral correlation spectra techniques. The results showed that the hydrochemistry type of groundwater in the facility vegetable field was Cl-SO4, the nitrogen content was higher than the National Groundwater V Class Quality Standard (GB/T14848-93), and the heavy metal content was lower than the National Drinking Water Standard (GB5749-2006). The nitrification process was blocked due to a strongly reducing atmosphere and shallow depth in groundwater, which caused high concentrations of NH4+-N. Part of the toxic sulfur-containing metal content increased after the application of inorganic fertilizers. The sources of dissolved organic matter in groundwater were similar; the organic manure components which leach into groundwater were recently produced by microbial metabolism. The main components of dissolved organic matter were small-molecule-biodegradable protein-like substances and the fulvic-like content binding to them. The fulvic-like content that bound to protein-like content in vegetable planting groundwater was stable, while the protein-like content was greatly influenced by the cultivation process of the organic manure application. In the process of vegetable planting, organic manure should be applied scientifically and the supervision of the planting area is crucial.

[Evolution of Dissolved Organic Matter Properties in a Constructed Wetland of Xiao River, Hebei].

The evolution of water DOC and COD, and the source, chemical structure, humification degree and redox of dissolved organic matter (DOM) in a constructed wetland of Xiao River, Hebei, was investigated by 3D excitation--emission matrix fluorescence spectroscopy coupled with ultraviolet spectroscopy and chemical reduction, in order to explore the geochemical processes and environmental effects of DOM. Although DOC contributes at least 60% to COD, its decrease in the constructed wetland is mainly caused by the more extensive degradation of elements N, H, S, and P than C in DOM, and 65% is contributed from the former. DOM is mainly consisted of microbial products based on proxies f470/520 and BIX, indicating that DOM in water is apparently affected by microbial degradation. The result based on PARAFAC model shows that DOM in the constructed wetland contains protein-like and humus-like components, and Fulvic- and humic-like components are relatively easier to degrade than protein-like components. Fulvic- and humic-like components undergo similar decomposition in the constructed wetland. A common source of chromophoric dissolved organic matter (CDOM) and fluorescent dissolved organic matter (FDOM) exists; both CDOM and FDOM are mainly composed of a humus-like material and do not exhibit selective degradation in the constructed wetland. The proxies E2 /E3, A240-400, r(A, C) and HIX in water have no changes after flowing into the constructed wetland, implying that the humification degree of DOM in water is hardly affected by wet constructed wetland. However, the constructed wetland environment is not only beneficial in forming the reduced state of DOM, but also facilitates the reduction of ferric. It can also improve the capability of DOM to function as an electron shuttle. This result may be related to the condition that the aromatic carbon of DOM can be stabilized well in the constructed wetland.

[Pollution Characteristics Analysis in Shallow Groundwater of Typical Farmland Area, Southern China].

To analyze the characteristics of shallow groundwater pollution in farmland ecosystem in south China and geochemical behavior of major pollutants in the environment, taking the typical farmland in Taihu River Basin as the object, combined with conventional analysis method of the water quality, fluorescence spectrum technology and multivariate statistical analysis method, the characteristics of the water chemistry in shadow groundwater and the distribution of the dissolved organic matter and the heavy metals were studied. The reasons for all the phenomena were researched as well. The result showed that, water body in the study area showed the reducing atmosphere, the main chemical types of shallow groundwater were HCO3-Ca·Na, and compared to the contents of NH3--N and NH2--N, the concentration of NH4+-N was higher. Dissolved organic matter of the shallow groundwater was composed of humic acid, tryptophan and tyrosine. And they were mainly derived from terrestrial and biological source. The distribution was affected by the flow direction of the surface water supplies and groundwater. In the detection of nine kinds of heavy metal elements, the average concentrations of Fe and Cr were higher than the national groundwater environmental quality in class Ⅲ standard. And the contents of Fe, Cr, Mn, Zn elements at some points exceeded the standard. The results showed that fluorescent organic matter characteristics could better reflect the status of shallow groundwater pollution, in which the kind of protein-like substances was closely related to the ammonia nitrogen. The heavy metal elements Cu and Ni were associated with the dissolved organic matter and they were mainly complexed in small molecular fluorescent organic matter.

Contamination of Phthalate Esters (PAEs) in Typical Wastewater-Irrigated Agricultural Soils in Hebei, North China.

The Wangyang River (WYR) basin is a typical wastewater irrigation area in Hebei Province, North China. This study investigated the concentration and distribution of six priority phthalate esters (PAEs) in the agricultural soils in this area. Thirty-nine soil samples (0-20 cm) were collected along the WYR to assess the PAE residues in soils. Results showed that PAEs are ubiquitous environmental contaminants in the topsoil obtained from the irrigation area. The concentrations of Σ6PAEs range from 0.191 µg g-1 dw to 0.457 µg g-1 dw with an average value of 0.294 µg g-1 dw. Di(2-ethylhexyl) phthalate (DEHP) and di-n-butyl phthalate (DnBP) are the dominant PAE species in the agricultural soils. Among the DEHP concentrations, the highest DEHP concentration was found at the sites close to the villages; this result suggested that dense anthropogenic activities and random garbage disposal in the rural area are possible sources of PAEs. The PAE concentrations were weakly and positively correlated with soil organic carbon and soil enzyme activities; thus, these factors can affect the distribution of PAEs. This study further showed that only dimethyl phthalate (DMP) concentrations exceeded the recommended allowable concentrations; no remediation measures are necessary to control the PAEs in the WYR area. However, the PAEs in the topsoil may pose a potential risk to the ecosystem and human health in this area. Therefore, the exacerbating PAE pollution should be addressed.

[Spectral Characteristic of Dissolved Organic Matter in Xiaohe River, Hebei].

The spectral characteristic of dissolved organic matter (DOM) in Xiaohe River, Hebei, was investigated by fluorescence spectroscopy, ultraviolet-visible absorption spectroscopy, and basic chemical water quality indicators. The data was then statistical analyzed using principal component analysis and correlation analysis method. The result based on 3D excitation-emission matrix fluorescence spectroscopy showed that DOM in Xiaohe River contained both protein-like and humus-like components. DOM and N-containing compounds were obviously correlated with COD, especially between NH4+ -N and humic-like component, indicating that COD of water in Xiaohe River can be reduced by removing NH4+ -N and DOM, which could be good indicators for monitoring water quality in the future. The relative content of protein-like component reduces gradually along the downstream, while that of humic-like component showed an increasing trend. DOM in samples S1 and S2 was mainly consisted of humic-like components with larger molecular weight and higher aromaticity, while that in samples S3 and S6 was mainly consisted of protein-like components with smaller molecular weight, lower aromaticity, which are easier to be degraded. Therefore, in order to enhance the remove of refractory humic-like substances, sewage treatment plants of S1 and S2 or improved membrane treatment equipment with better removal effect of macromolecules should be provide. On the other hand, the anaerobic and aerobic biological treatment processes should be optimized in S3 and S6, so as to better remove these degradable protein-like substances.