Comparative study of the quick action effect of multiple enzyme-based nano-emulsified oils in enhancing nitrate contamination remediation in groundwater.

Emulsified vegetable oil (EVO), as a novel green slow-releasing substrate, has performed great potential in subsurface bioremediation due to its slow release and longevity. Nevertheless, the long time it takes to initiate this process still exposed some limitations. Herein, multiple enzyme-based EVOs (EN-EVOs) were developed to enhance the quick-acting effect in nitrate-contaminated bioremediation. This study demonstrated that EN-EVOs loaded with cellulose (c-EVO) and protein enzymes (p-EVO) performed best, not only did not change the advantages of traditional EVO, but also optimized the stability and particle size to the level of 0.8-0.9 and 247.95-252.25 nm, respectively. Nitrate (NO3-N) degradation further confirmed the superiority of c-EVO in rapidly initiating degradation and achieving stable denitrification. Compared with traditional EVO, the maximum start-up efficiency and the rapid achieving stable denitrification efficiency were improved by 37.6% and 1.71 times, respectively. In such situation, the corresponding NO3-N removal efficiency, kinetics rate constant (k1), and half-life period (t1/2) reached as high as 85.39%, as quick as 1.079 d-1, and as short as 0.64 d after 30-day cultivation. Meanwhile, the rapid conversion efficiency of NO2-N was observed (k2 = 0.083 d-1). High-throughput 16S rRNA gene sequencing indicated that the quick-acting process of NO3-N reduction coupled to c-EVO was mediated by microbial reducers (e.g., Ralstonia, Gulbenkiania, and Sphingobacterium) with regulations of narG, nirS and norB genes. Microorganisms with these genes could achieve quick-acting not only by enhancing microbial activity and the synthesis and metabolism of volatile fatty acids, but also by reducing the production and accumulation of loosely bound-extracellular polymeric substances (LB-EPS). These findings advance our understanding on fast-acting of NO3-N degradation supported by c-EVO and also offer a promising direction for groundwater remediation.

The association between the non-high-density lipoprotein cholesterol to high-density lipoprotein cholesterol ratio and the risk of osteoporosis among U.S. adults: analysis of NHANES data.

BACKGROUND: Osteoporosis and atherosclerosis frequently afflict older adults, and recent insights suggest a deeper connection between these conditions that surpasses mere aging effects. The ratio of non-high-density to high-density lipoprotein cholesterol (NHHR) has emerged as a novel lipid marker for evaluating the risk of cardiovascular diseases. Nonetheless, investigations into the correlation of the NHHR with the risk of developing osteoporosis remain unexplored. METHODS: We collected NHHR and bone mineral density (BMD) data from 11,024 National Health and Nutrition Examination Survey (NHANES) participants between 2011 and 2018. Multivariate linear regression was employed to examine the correlation between BMD and NHHR. Smooth curves were employed to deal with the nonlinearity. To further account for the nonlinear link, we used a two-part linear regression model. The threshold effects were estimated using two components of a linear regression model. Subgroup and sensitivity analyses were carried out to ascertain the stability of the findings. RESULTS: We discovered a negative relationship between the NHHR and lumbar spine BMD in all three models. An L-shaped curvilinear association existed between the NHHR and lumbar spine BMD, with a key inflection point of 6.91. The fully adjusted model showed that the BMD of the lumbar spine fell by 0.03 g/cm2 in those who were in the fourth quartile as opposed to the lowest quartile. The sensitivity analysis using unweighted logistic analysis verified the stability of the results. In addition, BMD in the nondiabetic group was more significantly affected by the negative effect of the NHHR in the subgroup analysis. CONCLUSIONS: According to this research, there appears to be a negative correlation between BMD and NHHR in US Adults. To clarify the precise physiological mechanisms by which the NHHR contributes to the onset of osteoporosis, more research is necessary.

The area ratio of Modic changes has predictive value for postoperative surgical site infection in lumbar spine surgery: a retrospective study.

BACKGROUND: Increasing evidence suggests an association between Modic changes (MC) and subclinical infection and inflammatory reactions. However, the relationship between preoperative MC and surgical site infection (SSI) has not been fully explored. This study aims to investigate the correlation between MC and SSI. METHODS: A retrospective analysis was conducted on patients (n = 646) who underwent single-level lumbar spine surgery for lower back pain in our hospital between 2018 and 2023. According to the Centers for Disease Control and Prevention (CDC) criteria, the patients were divided into an SSI group (n = 40) and a Non-SSI group (n = 606). Univariate analysis was performed to determine the statistical differences in variables between the two groups, and the variables with significant differences were included in a multivariable logistic regression analysis to identify independent risk factors for SSI. Receiver operating characteristic (ROC) curve analysis was performed on the independent risk factors. RESULTS: The SSI group and the Non-SSI group exhibited significant differences in diabetes prevalence, MC prevalence, Total endplate score (TEPS) and area ratio of MC (P < 0.05). Age, gender, American Society of Anesthesiologists(ASA)score, hypertension, coronary heart disease (CHD), chronic obstructive pulmonary disease (COPD), MC classification, and the location of MC in the endplate showed no significant differences (P > 0.05). Multivariate binary logistic regression analysis was performed on the variables with significant differences, and the results indicated a significant correlation between TEPS (P = 0.009) and the area ratio of MC changes (P = 0.001) with SSI. ROC curve analysis was performed on the TEPS and area ratio of MC changes, and the results showed that the diagnostic value of TEPS (AUC: 0.641; CI: 0.522-0.759) is lower than the area ratio of MC (AUC: 0.722; CI: 0.621-0.824), and the combined diagnosis did not significantly improve the diagnostic value (AUC: 0.747; CI: 0.653-0.842). The area ratio of MC had moderate diagnostic value for SSI (AUC: 0.722; CI: 0.621-0.824), with a cut-off value of 24.62% determined by the Youden index (sensitivity: 69.2%; specificity: 73.1%), and for every 1% increase in the area ratio of MC changes, the risk of SSI in MC patients increased by 10.3% (OR = 1.103; CI: 1.044-1.167). CONCLUSION: The area ratio MC and the TEPS are independent risk factors for SSI after lumbar spine surgery. The predictive value of the area ratio of MC is greater than TEPS, and when the two are combined, the predictive value is not significantly improved. When the rate of MC exceeds 24.62%, caution should be exercised regarding the occurrence of SSI.

Anodic C(sp3)-H Acyloxylation of Indolin-3-ones Enabled by Oxidant-Free Cross-Dehydrogenative C(sp3)-O Coupling.

An efficient anodic C(sp3)-H acyloxylation protocol has been established via intermolecular cross-dehydrogenative C(sp3)-O coupling. The protocol provides various C2-acyloxy indolin-3-ones without the addition of metal catalysts and external oxidants because indolin-3-ones can be directly oxidized at the anode. The effective application of several medical drugs and the realization of the gram-scale experiment have proven the practicality of this protocol.

Transport and retention of nano emulsified vegetable oil in porous media: Effect of pore straining, roughness wedging, and interfacial effects.

Emulsified vegetable oil (EVO), as one of the novel green substrates, has been widely used in subsurface remediation. In these applications, the retention behavior of EVO presents a challenge to remediation efficiency as mechanism insights into the retention of EVO is limited. Herein, Brinell funnels experiments with X-ray microtomography (XMT) were conducted to examine the drainage and retention of nanoscale EVO in porous media, with a specific focus on investigating the impact of pore straining, grain surface roughness, and interfacial effects on Nano-EVO (NEVO) retention. This study demonstrated that the retention of NEVO in porous media is the synergistic result of pore straining, roughness wedging, and interface attachment. With the action of these effects, three residual states of NEVO, incorporating retention at porous ganglia, grain-grain contacts, and grain surface, were identified by XMT in porous media. After multiple periods of drainage and imbibition, the NEVO arrived at stable retention proportions of 46.3%, 72.2%, and 85.9% in three independent systems with coarse, medium, and fine sand as porous media, respectively. The interfacial effects, including the attachment of solid-phase and air-liquid interface, are confirmed as the dominant factors for the retention of NEVO in porous media, which contributed 35.63-47.33% of total retention for the conditions employed. Correspondingly, the contributions of pore straining and roughness wedging only ranged 3.78-24.06% and 3.87-9.94%, respectively. The consistency of the contributions between the actual measurement of XMT and computational evaluation further confirmed the rationality and reliability of the results. In such the dominant factor, interfacial tension, contact angle, and capillary radius play an essential role in NEVO retention, which could be reflected by capillary rise height. These findings advance our understanding on NEVO retention caused by substrate-media interaction and also offer a promising direction for subsurface remediation.

Formation Process of Silicate-Iron Oxyhydroxide Complex and Its Influence on the Distribution of Heavy Metals in Mining Area.

Silicate-iron oxyhydroxide complex formed by mineral weathering has an important influence on the geochemical reactions of heavy metals in mining areas. In this work, tailings were collected from an abandoned iron tailings pond, and the physicochemical properties and distribution of heavy metals were studied under natural weathering and hydraulic processes. The results showed that Fe2+ in the iron tailings were transported to the surface during the weathering process, and then the iron oxyhydroxide formed by mineralization adsorbed Cu2+ and Zn2+. Silicic acid and exchangeable acid were released during the formation of binary agglomerates between hydroxy iron oxide and kaolin, then they migrated to the lower area of a tailing pond via surface runoff. Finally, silicate-iron oxyhydroxide complex were formed. The heavy metals were replaced by H+ and penetrated to the bottom layer with water. This research provides an important scientific basis for the prevention and control of heavy metal pollution in mining areas.

Cytotoxicity of chemical constituents from Torricellia tiliifolia DC. on Spodoptera litura (SL-1) cells.

In this study, we evaluated cytotoxicity of chemicals isolated from Torricellia tiliifolia DC. on Spodoptera litura (SL-1) cell line. Among the isolated compounds, 4-hydroxy-3-methoxycinnamaldehyde, 3,5-dimethoxy-4-hydroxycinnamaldehyde, and syringaresinol inhibited SL-1 cell survival in both dose- and time-dependent manners. Meanwhile, the in vivo insecticidal activity test revealed that 4-hydroxy-3-methoxycinnamaldehyde and 3,5-dimethoxy-4-hydroxycinnamaldehyde showed obvious insecticidal activities. These two compounds exhibited toxicity to SL-1 cells by inducing cellular morphological changes including shape change, cell shrinkage, vacuolation, cell membrane blebbing and chromatin condensation and apoptosis. 4-hydroxy-3-methoxycinnamaldehyde and 3,5-dimethoxy-4-hydroxycinnamaldehyde showed the most effect on mitochondrial membrane depolarization at 24h and 72h respectively and induced the apoptosis at a late time point 72h. Our results suggest that 4-hydroxy-3-methoxycinnamaldehyde and 3,5-dimethoxy-4-hydroxycinnamaldehyde inhibit SL-1 survival by inducing apoptosis.

Formation process and mechanism of humic acid-kaolin complex determined by carbamazepine sorption experiments and various characterization methods.

To explore the formation process and mechanism of organic matter and organic-mineral complex under humification and mineralization conditions, a series of samples including humic acid, kaolin, and humic acid-kaolin complex were prepared using a subcritical water treatment method (SWT) under specific temperature, pressure and reaction time conditions. HA was used as a surrogate for natural organic matter because it has a similar abundant pore structure, variety of carbon types, and chemical components. These samples were used in carbamazepine (CBZ) sorption experiments and characterized by a variety of techniques. The polymerization of humic acid under the conditions of increased temperature and pressure resulted in an increase in specific surface area and molecular quantity. In addition, the degree of aromaticity rose from 59.52% to 70.90%. These changes were consistent with the transformation from 'soft carbon' to 'hard carbon' that occurs in nature. The results of sorption experiments confirmed the interaction between humic acid and kaolin from the difference between the predicted and actual Qe values. The conceptual model of humic acid-kaolin complex could be deduced and described as follows. Firstly, the aromatic components of humic acid preferentially combine with kaolin through the intercalation effect, which protects them from the treatment effects. Next, the free carboxyl groups and small aliphatic components of humic acid interact on the surface of kaolin, and these soft species transform into dense carbon through cyclization and polymerization. As a result, humic acid-kaolin complex with a mineral core and dense outer carbonaceous patches were formed.

Characteristics of change in water quality along reclaimed water intake area of the Chaobai River in Beijing, China.

To reveal the basic characteristics and controlling factors of water quality change in the project Wenyu to Chaobai reclaimed water diversion, the water quality in the study area was monitored for one year at seven monitoring sites. Inverse geochemical models of the statistical groups were developed using PHREEQC to elucidate the hydrochemistry characteristics of reclaimed water and the factors. The monitoring results indicated that nitrogen and phosphorus contents were significantly reduced along the river mainly caused by seasonal and location variation. The pH ranged from 7.44 to 9.81. Photosynthesis of algae and denitrification in anaerobic microenvironment ultimately led to a sudden pH increase after the Jian River and the Chaobai River confluence. Mg2+ and SO42- levels dropped obviously in the summer and increased in winter seasons after intersection. Na+ and Cl- are relatively stable, and marked drop in the concentration only after the two rivers meet. And there is a decrease of Ca2+ and HCO3- and increase in CO32- during monitoring period. As a whole, the primary ions and nutrient components, including nitrogen and phosphorus, had high levels in winter. Algae's photosynthesis and respiration were observed to have an impact on the river water quality; there was precipitation-dissolution of minerals and denitrification from upstream to downstream. Inverse geochemical PHREEQC modeling confirmed that there was precipitation of aragonite or calcite, and gypsum or anhydrite in summer, and dissolution in winter; as well as precipitation of dolomite in winter, and cationic exchange and denitrification along the river.

Synthesis and LC-MS/MS analysis of desmosine-CH2, a potential internal standard for the degraded elastin biomarker desmosine.

Desmosine-CH2, an analog of the elastic tissue degradation biomarker desmosine, can be regarded as a potential internal standard for precise quantification of desmosines by LC-MS/MS. In this study, the chemical synthesis of desmosine-CH2 was completed in 22% overall yield in five steps. The LC-MS/MS analysis of desmosine-CH2 was also achieved.

Evaluation of the effect of herbal agents as management of radiodermatitis in breast cancer patients: A systematic review and meta-analysis.

OBJECTIVE: To evaluate the effectiveness of herbal agents in the prevention and therapy of radiodermatitis in breast cancer patients. METHODS: Randomized controlled trials were searched from databases such as PubMed, Web of Science, Embase, Cochrane Library, and Chinese National Knowledge Infrastructure (CNKI) to assess the effectiveness of herbal agents compared to a standard medication or placebo in prevention or treatment of radiodermatitis in breast cancer. RESULTS: Data from 16 studies involving 1994 patients were included. This meta-analysis included 10 clinical trials of 562 breast cancer patients treated with calendula, silymarin, or aloe vera for the prevention of radiodermatitis. Silymarin showed positive effects in ameliorating the damage of radiodermatitis, whereas the efficacy of calendula and aloe vera in the treatment of radiodermatitis lacks sufficient evidence. CONCLUSIONS: Herbal medicine may show therapeutic effects on radiodermatitis in breast cancer, but more comprehensive investigations and clinical trials are required in the future.

Revealing the drivers and genesis of NO3-N pollution classification in shallow groundwater of the Shaying River Basin by explainable machine learning and pathway analysis method.

Nitrate (NO3-N), as one of the ubiquitous contaminants in groundwater worldwide, has posed a serious threat to public health and the ecological environment. Despite extensive research on its genesis, little is known about the differences in the genesis of NO3-N pollution across different concentrations. Herein, a study of NO3-N pollution concentration classification was conducted using the Shaying River Basin as a typical area, followed by examining the genesis differences across different pollution classifications. Results demonstrated that three classifications (0-9.98 mg/L, 10.14-27.44 mg/L, and 28.34-136.30 mg/L) were effectively identified for NO3-N pollution using Jenks natural breaks method. Random forest exhibited superior performance in describing NO3-N pollution and was thereby affirmed as the optimal explanatory method. With this method coupling SEMs, the genesis of different NO3-N pollution classifications was proven to be significantly different. Specifically, strongly reducing conditions represented by Mn2+, Eh, and NO2-N played a dominant role in causing residual NO3-N at low levels. Manure and sewage (represented by Cl-) leaching into groundwater through precipitation is mainly responsible for NO3-N in the 10-30 mg/L classification, with a cumulative contribution rate exceeding 80 %. NO3-N concentrations >30 mg/L are primarily caused by the anthropogenic loads stemming from manure, sewage, and agricultural fertilization (represented by Cl- and K+) infiltrating under precipitation in vulnerable hydrogeological conditions. Pathway analysis based on standardized effect and significance further confirmed the rationality and reliability of the above results. The findings will provide more accurate information for policymakers in groundwater resource management to implement effective strategies to mitigate NO3-N pollution.

Progress in regulating inflammatory biomaterials for intervertebral disc regeneration.

Intervertebral disc degeneration (IVDD) is rising worldwide and leading to significant health issues and financial strain for patients. Traditional treatments for IVDD can alleviate pain but do not reverse disease progression, and surgical removal of the damaged disc may be required for advanced disease. The inflammatory microenvironment is a key driver in the development of disc degeneration. Suitable anti-inflammatory substances are critical for controlling inflammation in IVDD. Several treatment options, including glucocorticoids, non-steroidal anti-inflammatory drugs, and biotherapy, are being studied for their potential to reduce inflammation. However, anti-inflammatories often have a short half-life when applied directly and are quickly excreted, thus limiting their therapeutic effects. Biomaterial-based platforms are being explored as anti-inflammation therapeutic strategies for IVDD treatment. This review introduces the pathophysiology of IVDD and discusses anti-inflammatory therapeutics and the components of these unique biomaterial platforms as comprehensive treatment systems. We discuss the strengths, shortcomings, and development prospects for various biomaterials platforms used to modulate the inflammatory microenvironment, thus providing guidance for future breakthroughs in IVDD treatment.

Revealing discrepancies and drivers in the impact of lomefloxacin on groundwater denitrification throughout microbial community growth and succession.

The coexistence of antibiotics and nitrates has raised great concern about antibiotic's impact on denitrification. However, conflicting results in these studies are very puzzling, possibly due to differences in microbial succession stages. This study investigated the effects of the high-priority urgent antibiotic, lomefloxacin (LOM), on groundwater denitrification throughout microbial growth and succession. The results demonstrated that LOM's impact on denitrification varied significantly across three successional stages, with the most pronounced effects exhibited in the initial stage (53.8% promotion at 100 ng/L-LOM, 84.6% inhibition at 100 µg/L-LOM), followed by the decline stage (13.3-18.2% inhibition), while no effect in the stable stage. Hence, a distinct pattern encompassing susceptibility, insusceptibility, and sub-susceptibility in LOM's impact on denitrification was discovered. Microbial metabolism and environment variation drove the pattern, with bacterial numbers and antibiotic resistance as primary influencers (22.5% and 15.3%, p < 0.01), followed by carbon metabolism and microbial community (5.0% and 3.68%, p < 0.01). The structural equation model confirmed results reliability. Bacterial numbers and resistance influenced susceptibility by regulating compensation and bacteriostasis, while carbon metabolism and microbial community impacted energy, electron transfer, and gene composition. These findings provide valuable insights into the complex interplay between antibiotics and denitrification patterns in groundwater.

Alpha-1 antitrypsin augmentation therapy and biomarkers of elastin degradation.

BACKGROUND: Intravenous alpha-1 antitrypsin protein (AAT) augmentation is a prescribed therapy for severe, genetically determined, alpha-1 antitrypsin deficiency (AATD), a genetic basis for pulmonary emphysema. AAT, a predominant systemic inhibitor of neutrophil elastase thus far has not been shown to decrease elastin degradation in a significant number of patients on this therapy. The objective of this study was to compare levels of biomarkers of elastin degradation in plasma, bronchoalveolar lavage (BALF) fluid and urine before and after beginning AAT augmentation therapy in patients with AATD. METHODS: Desmosine and isodesmosine (DI), which occur only in elastin, are amino acid cross-links in mature elastin. Levels of DI in body fluids measure degradation of elastin and can be measured more specifically by mass spectrometry. This method was used to measure DI levels in plasma, bronchoalveolar lavage fluid and urine in cohorts of severe AATD patients on augmentation, not on augmentation and before and after the initiation of augmentation therapy. RESULTS: Statistically significant reductions in plasma DI and in BALF DI were demonstrated in AATD patients receiving intravenous (IV) augmentation therapy as compared with those not receiving it. Administration by aerosol also produced statistically significant reductions in levels of DI in BALF. CONCLUSIONS: Results indicate that the currently prescribed doses of AAT augmentation inhibit neutrophil elastase adequately to reduce elastin degradation, both systemically and in the lung per se. The currently prescribed doses did not reduce elastin degradation to control levels, which may be possible with higher doses.

Transfer route and driving forces of antibiotic resistance genes from reclaimed water to groundwater.

The infiltration of reclaimed water has created a significant environmental risk due to the spread of antibiotic resistance genes (ARGs) in riparian groundwater. Reclaimed water from wastewater treatment plants (WWTPs) had been identified as a source of both antibiotics and ARGs in groundwater, based on their spatial and temporal distribution. The assembly process of microbial communities in the groundwater of the infiltration zone was more influenced by deterministic processes. Co-occurrence network analysis revealed that Thermotoga, Desulfotomaculum, Methanobacterium, and other such genera were dominant shared genera. These were considered core genera and hosts of ARGs for transport from reclaimed water to groundwater. The most abundant ARG in these shared genera was MacB, enriched in groundwater point G3 and potentially transferred from reclaimed water to groundwater by Acidovorax, Hydrogenophaga, Methylotenera, Dechloromonas, and Nitrospira. During the infiltration process, environmental factors and the tradeoff between energy metabolism and antibiotic defense strategy may have affected ARG transfer. Understanding the transfer route and driving forces of ARGs from reclaimed water to groundwater provided a new perspective for evaluating the spread risk of ARGs in reclaimed water infiltration.

Effect and genesis of soil nitrogen loading and hydrogeological conditions on the distribution of shallow groundwater nitrogen pollution in the North China Plain.

The North China Plain (NCP) has experienced increasingly severe groundwater nitrogen (TN) pollution. However, the factors influencing TN distribution are still poorly understood. Previous studies have identified surface soil nitrogen (TSN) loading and intrinsic groundwater vulnerability (Inv) as the main factors controlling groundwater TN pollution. However, in this study, based on 3245 shallow groundwater samples in the NCP, the multiple regression analysis results(R2=0.105, p<0.001) revealed that the TN was not mainly controlled by TSN and Inv. The lower prediction accuracy indicated the large data dispersion of TN, which might be affected by nitrogen attenuation or accumulation. Thus, the NCP was divided into balance, attenuation, and accumulation zones according to the regression equation. The attenuation zone was mainly distributed in the inter-fan and fan edge parts of the pre-mountain alluvial floodplain, as well as the west and south of the runoff area, while the accumulation zone was mainly distributed in the top part of the pre-mountain alluvial floodplain and the east of discharge area. Multi-indicators comparative analysis showed that compared to the balance (Eh= 76.2 mV) and accumulation (Eh=126.7 mV) zones, the attenuation zone has a stronger reducing environment (Eh=30.8 mV) favorable to denitrification, which can reduce the TN pollution (0.49 mg/L) caused by surface nitrogen input and consume more electron donors. Conversely, the stronger oxidizing environment in the accumulation zone limited denitrification, resulting in higher TN concentrations (19.14 mg/L) in the aquifers under the same TSN and Inv conditions as the other two zones. The standardized effects and significance on each path of the structural equation model (SEMs) fully confirmed the reliability of the above zonal analysis. Importantly, the feature importance (23.6%) of random forest and standardized effects (0.455, p<0.001) of SEMs showed that the Eh had the strongest influence on TN. Thus, the redox conditions of the aquifer, in addition to TSN and Inv, played a crucial role in controlling the TN pollution in the groundwater of a large region. The zoning work and the analysis of influencing factors are important to guide scientific prevention and control of groundwater nitrogen pollution.

EMMTE: An Excel VBA tool for source apportionment of nitrate based on the stable isotope mixing model.

Dual nitrate stable isotopes combined with end-member mixing models are typically used to identify nitrate sources in fields of geochemistry and environmental science, which helps to quantitively depict the geochemical behaviors of nitrate and accurately control the sources of nitrate pollution in waters. Recently, various models with different computation principles, working efficiency, and operation difficulty have been developed and applied in the source apportionment of nitrate. In this paper, an end-member mixing model tool on Excel™, namely EMMTE, has been written with Visual Basic for Application (VBA) and built into a macro-enabled Excel™ spreadsheet. Monte Carlo simulation and constraint relative deviation between the observed and the predicted values were included in the working algorithm to solve the mass balance equation. After comparison with the internationally recognized Bayesian framework (mixing stable isotope analysis in R, MixSIAR) in different cases (three practical cases and one virtual case), the preliminary results showed that the contribution of various sources to groundwater nitrate calculated by EMMTE was highly consistent with that by MixSIAR and the performance of EMMTE seemed to be as good as that of MixSIAR as indicated by the higher goodness-of-prediction, lower root-mean-square error, and lower relative deviation. Therefore, EMMTE is applicable in the source apportionment of groundwater nitrate, and might also be extended to other water bodies and mixtures. It provides a simple, feasible, and user-friendly for front-line workers without experience with MixSIAR to quantitively source apportionment of nitrate in waters.

Response of microbial taxonomic and nitrogen functional attributes to elevated nitrate in suburban groundwater.

Anthropogenic nitrogen (N) input has led to elevated levels of nitrate nitrogen (NO3--N) in the groundwater. However, insights into the responses of the microbial community and its N metabolic functionality to elevated NO3--N in suburban groundwater are still limited. Here, we explored the microbial taxonomy, N metabolic attributes, and their responses to NO3--N pollution in groundwaters from Chaobai River catchment (CR) and Huai River catchment (HR) in Beijing, China. Results showed that average NO3--N and NH4+-N concentrations in CR groundwater were 1.7 and 3.0 folds of those in HR. NO3--N was the dominant nitrogen specie both in HR and CR groundwater (over 80 %). Significantly different structures and compositions of the microbial communities and N cycling gene profiles were found between CR groundwater and HR groundwater (p < 0.05), with CR groundwater harboring significantly lower microbial richness and abundance of N metabolic genes. However, denitrification was the dominant microbial N cycling process in both CR and HR groundwater. Strong associations among NO3--N, NH4+-N, microbial taxonomic, and N functional attributes were found (p < 0.05), suggesting denitrifiers and Candidatus_Brocadia might serve as potential featured biomarkers for the elevated NO3--N and NH4+-N concentration in groundwater. Path analysis further revealed the significant effect of NO3--N on the overall microbial N functionality and microbial denitrification (p < 0.05). Collectively, our results provide field evidence that elevated levels of NO3--N and NH4+-N under different hydrogeologic conditions had a significant effect on the microbial taxonomic and N functional attributes in groundwater, with potential implications for improving sustainable N management and risk assessment of groundwater.

Novel insights into source apportionment of dissolved organic matter in aquifer affected by anthropogenic groundwater recharge: Applicability of end-member mixing analysis based optical indices.

The composition and main sources of dissolved organic matter (DOM) in groundwater may change significantly under long-term anthropogenic groundwater recharge (AGR); however, the impact of AGR on quantitative sources of groundwater DOM has seldom been reported. This study evaluated the applicability of optical indices combined with mixing stable isotope analysis in R (MixSIAR) in end-member mixing analysis (EMMA) of groundwater DOM. Fluorescent indices, including C1%, C2%, and C3%, were more sensitive to AGR than other absorbance indices, as indicated by the significant difference between the dominant area of artificial groundwater recharged by surface water and the dominant area of natural groundwater recharged by atmospheric precipitation (NGRP). BIX-C1% was selected as the optimal dual index after the screening protocol of groundwater DOM for EMMA. Our results showed that DOM in the aquifer was mainly subject to autochthonous DOM and the contribution of background groundwater to AGRSW and NGRP groundwater accounted for 36.15% ± 32.41% and 55.46% ± 37.17% (p < 0.05), respectively. Therefore, AGR significantly changed the native DOM in the groundwater. In allochthonous sources of DOM, sewage and surface water contributed 29.54% ± 24.87% and 21.32% ± 28.08%, and 24.79% ± 15.56% and 15.21% ± 14.20% to AGRSW and NGRP groundwater, respectively. The contribution of surface water to AGRSW groundwater was significantly higher than that to NGRP groundwater (p < 0.05), indicating that AGR introduced significantly more DOM from surface water to groundwater. This study provides novel insights into the quantitative source apportionment of DOM in groundwater under long-term AGR, which will facilitate the environmental risk assessment of present AGR measures and the sustainable management of clean water.