Effects of microalgal (Tetradesmus obliquus MCX38) attachment on photobioreactor treatment efficiency of raw swine wastewater.

Attachment of microalgae on the inner surfaces of photobioreactors impacts the efficiency of swine wastewater treatment by reducing the light intensity, which has been overlooked in previous studies. This study investigated the relationship between microalgal attachment biomass and light intensity in photobioreactors, determined the optimal attachment time for effective pollutant removal, and clarified the mechanisms of microalgal attachment in swine wastewater. After 9 days of treatment, the attached biomass in the photobioreactor increased from 0 to 6.4 g/m2, decreasing the light intensity from 2,000 to 936 lux. At the 24 h optimal attachment time, the concentrations of chemical oxygen demand, ammonia nitrogen, and total phosphorus decreased from 2725.1, 396.4, and 87.2 mg/L to 361.2, 4.9, and 0.8 mg/L, respectively. Polysaccharides in the extracellular polymeric substances released by microalgae play a significant role in facilitating microalgae attachment. Optimizing the microalgal attachment time within photobioreactors effectively mitigates pollutant concentrations in swine wastewater.

Free triiodothyronine to free thyroxine ratio as a marker of poor prognosis in euthyroid patients with acute coronary syndrome and diabetes after percutaneous coronary intervention.

Objectives: In recent years, the free triiodothyronine/free thyroxine (FT3/FT4) ratio, a new comprehensive index for evaluating thyroid function, which could reflect thyroid function more stably and truly than serum thyroid hormone level, has been demonstrated to correlate with the risks of diabetes and cardiovascular disease in euthyroid adults. However, the correlation between thyroid hormone sensitivity and long-term prognosis in euthyroid patients with acute coronary syndrome (ACS) and diabetes after percutaneous coronary intervention (PCI) remains unclear. Methods: A total of 1,786 euthyroid patients with ACS who successfully underwent PCI at Beijing Anzhen Hospital from August 2021 to April 2022 were included in our study, which was divided into three groups according to tertiles of thyroid hormone sensitivity index. Cox regression, Kaplan-Meier, and receiver operating characteristic analyses were applied to analyze the associations between the FT3/FT4 ratio with ACS and diabetes after PCI. Results: Our analysis indicated that a lower level of FT3/FT4 ratio in euthyroid patients with acute coronary syndrome (ACS) and diabetes after PCI showed significantly higher incidences of major adverse cardiac and cerebrovascular events (MACCE) when compared with a higher level of FT3/FT4 ratio. After adjusting for other covariates, patients with a lower level of FT3/FT4 ratio were negatively associated with the risk of MACCE than those with a higher level of FT3/FT4 ratio (adjusted OR =1.61, 95% CI 1.05-2.47, P = 0.028). In subgroup analyses, individuals were stratified by age, sex, BMI, ACS type, hypertension, and dyslipidemia, showing that there were no significant interactions between the FT3/FT4 ratio and all subgroups for MACCE. In addition, the FT3/FT4 ratio performed better on ROC analyses for cardiac death prediction [area under the curve (AUC), 0.738]. Conclusion: A reduced level of FT3/FT4 ratio was a potential marker of poor prognosis in euthyroid patients with ACS and diabetes after PCI.

Influences of shallow groundwater depth on N2O diffusion along the soil profile of summer maize fields in North China Plain.

The emissions of nitrous oxide (N2O) from agricultural fields are a significant contribution to global warming. Understanding the mechanisms of N2O emissions from agricultural fields is essential for the development of N2O emission mitigation strategies. Currently, there are extensive studies on N2O emissions on the surface of agricultural soils, while studies on N2O fluxes at the interface between the saturated and unsaturated zones (ISU) are limited. Uncertainties exist regarding N2O emissions from the soil-shallow groundwater systems in agricultural fields. In this study, a three-year lysimeter experiment (2019-2020, 2022) was conducted to simulate the soil-shallow groundwater systems under four controlled shallow groundwater depth (SGD) (i.e., SGD = 40, 70, 110, and 150 cm) conditions in North China Plain (NCP). Weekly continuous monitoring of N2O emissions from soil surface, N2O concentration in the shallow groundwater and the upper 10 cm of pores at the ISU, and nitrogen cycling-related parameters in the soil and groundwater was conducted. The results showed that soil surface N2O emissions increased with decreased shallow groundwater depth, and the highest emissions of 96.44 kg ha-1 and 104.32 kg ha-1 were observed at G2 (SGD = 40 cm) in 2020 and 2022. During the observation period of one maize growing season, shallow groundwater acted as a sink for the unsaturated zone when the groundwater depth was 40 cm, 70 cm, and 110 cm. However, when SGD was 150 cm, shallow groundwater became a source for the unsaturated zone. After fertilization, the groundwater in all treatment plots behaved as a sink for the unsaturated zone, and the diffusion intensity decreased with increasing SGD. The results would provide a theoretical basis for cropland water management to reduce N2O emissions.

Association between the cumulative average triglyceride glucose-body mass index and cardiovascular disease incidence among the middle-aged and older population: a prospective nationwide cohort study in China.

BACKGROUND: Findings from earlier research have established that insulin resistance (IR) is implicated in atherosclerosis progression, representing a noteworthy risk factor for cardiovascular disease (CVD). Recently, the triglyceride glucose-body mass index (TyG-BMI) has been introduced as a straightforward and robust alternative indicator for early detection of IR. Nevertheless, there is a scarcity of studies that have examined the capability of TyG-BMI for predicting incident CVD. Consequently, the core objective of this study was to determine whether the cumulative average TyG-BMI correlated with CVD incidence. METHODS: All data was sourced from the China Health and Retirement Longitudinal Study (CHARLS). The exposure was the cumulative average TyG-BMI, determined by the average of TyG-BMI values for the baseline and follow-up investigations (Wave 1 in 2011, Wave 3 in 2015, respectively). The calculation of TyG-BMI involved a combination of triglyceride, fasting blood glucose, and body mass index. The primary outcome was incident CVD. Logistic regression analyses as well as restricted cubic spline (RCS) regression analyses were performed for examining the association between the cumulative average TyG-BMI and CVD incidence. RESULTS: In all, 5,418 participants were enrolled in our analysis, with 2,904 (53.6%) being female, and a mean (standard deviation, SD) age of 59.6 (8.8) years. The mean (SD) cumulative average TyG-BMI among all participants was 204.9 (35.7). Totally, during a 4-year follow-up, 543 (10.0%) participants developed CVD. The fully adjusted logistic regression analysis revealed a significant association between the cumulative average TyG-BMI and incident CVD [odds ratio (OR), 95% confidence interval (CI): 1.168, 1.040-1.310, per 1 SD increase]. The RCS regression analysis displayed a positive, linear association of the cumulative average TyG-BMI with CVD incidence (P for overall = 0.038, P for nonlinear = 0.436). CONCLUSIONS: Our study revealed a noteworthy correlation between the cumulative average TyG-BMI and incident CVD among the middle-aged and older population. The cumulative average TyG-BMI emerges as a valuable tool that may enhance the primary prevention and treatment of CVD.

Non-negligible N2O emission hotspots: Rivers impacted by ion-adsorption rare earth mining.

Rare earth mining causes severe riverine nitrogen pollution, but its effect on nitrous oxide (N2O) emissions and the associated nitrogen transformation processes remain unclear. Here, we characterized N2O fluxes from China's largest ion-adsorption rare earth mining watershed and elucidated the mechanisms that drove N2O production and consumption using advanced isotope mapping and molecular biology techniques. Compared to the undisturbed river, the mining-affected river exhibited higher N2O fluxes (7.96 ± 10.18 mmol m-2d-1 vs. 2.88 ± 8.27 mmol m-2d-1, P = 0.002), confirming that mining-affected rivers are N2O emission hotspots. Flux variations scaled with high nitrogen supply (resulting from mining activities), and were mainly attributed to changes in water chemistry (i.e., pH, and metal concentrations), sediment property (i.e., particle size), and hydrogeomorphic factors (e.g., river order and slope). Coupled nitrification-denitrification and N2O reduction were the dominant processes controlling the N2O dynamics. Of these, the contribution of incomplete denitrification to N2O production was greater than that of nitrification, especially in the heavily mining-affected reaches. Co-occurrence network analysis identified Thiomonas and Rhodanobacter as the key genus closely associated with N2O production, suggesting their potential roles for denitrification. This is the first study to elucidate N2O emission and influential mechanisms in mining-affected rivers using combined isotopic and molecular techniques. The discovery of this study enhances our understanding of the distinctive processes driving N2O production and consumption in highly anthropogenically disturbed aquatic systems, and also provides the foundation for accurate assessment of N2O emissions from mining-affected rivers on regional and global scales.

Long-term safety of ultrathin bioabsorbable-polymer sirolimus-eluting stents versus thin durable-polymer drug-eluting stents in acute coronary syndrome: A systematic review and meta-analysis.

BACKGROUND: Because of the advancement of bioabsorbable polymers and thinner struts, bioabsorbable-polymer sirolimus-eluting stents (BP-SES) with ultrathin struts may be related to superior performance when compared to durable-polymer drug-eluting stents (DP-DES) with thin struts. Nonetheless, the long-term safety of ultrathin BP-SES in acute coronary syndrome (ACS) remains unknown. METHODS: We sought to assess the long-term safety of ultrathin BP-SES in ACS patients, conducting a thorough meta-analysis of all relevant trials drawing a comparison between ultrathin BP-SES and contemporary thin DP-DES. Target lesion failure (TLF), which includes cardiac death (CD), target-vessel myocardial infarction (TV-MI), and clinically driven target lesion revascularization (CD-TLR) was considered the primary endpoint. Multiple databases comprising Embase, MEDLINE, Cochrane Library, and Pubmed were all thoroughly searched. RESULTS: There were seven randomized controlled trials included in our study with 7522 randomized patients with ACS (BP-SES = 3888, DP-DES = 3634). TLF occurred in 371 (9.5% in BP-SES) and 393 (10.8% in DP-DES) patients, respectively, across a 40.7-month weighted mean follow-up, with no statistically significant group differences (risk ratio [RR]: 0.87; 95% confidence interval [CI]: 0.73-1.04; p = .12). Furthermore, no significant differences in cardiac death (RR: 0.96; 95% CI: 0.68-1.35; p = .81), TV-MI (RR: 0.63; 95% CI: 0.36-1.10; p = .10) and CD-TLR (RR: 0.77; 95% CI: 0.46-1.29; p = .32) were detected between two groups. CONCLUSION: During a follow-up of 40.7 months, ultrathin BP-SES and thin DP-DES had a comparable risk of TLF and its individual components (CD, TV-MI, and CD-TLR), indicating that ultrathin BP-SES held at least the same safety and efficiency as thin DP-DES presented in patients with ACS.

Insights on the assembly processes and drivers of soil microbial communities in different depth layers in an abandoned polymetallic mining district.

Soil microbes, which play crucial roles in maintaining soil functions and restoring degraded lands, are impacted by heavy metal pollution. This study investigated the vertical distribution of bacterial communities along the soil profiles across four types of areas (heavy metal pollution level: tailings heap area > phytoremediation area > natural restoration area > original forest area) in an abandoned polymetallic mining district by 16S rRNA sequencing, and aimed to disentangle the assembly mechanisms and key drivers of the vertical variation in bacterial community structure. Bacterial diversity and composition were found to vary remarkably between the depth layers in all types of areas, with heterogeneous selection dominated the vertical distribution pattern of soil bacterial communities. Pearson correlation analysis and partial Mantel test revealed that soil nutrients mainly shaped the vertical distribution of bacterial microbiota along soil profiles in the original forest and natural restoration areas. Ni, As, and bioavailable As were the key drivers regulating the vertical variation of bacterial assemblages in the phytoremediation area, whereas Pb, pH, soil organic carbon, and available nitrogen were crucial drivers in the tailings heap area. These findings reveal the predominant assembly mechanisms and drivers governing the vertical distribution of soil bacterial microbiota and indicate the efficiency of phytoremediation and ecological restoration on ameliorating edaphic micro-ecosystems in heavy metal-contaminated areas.

Phosphors Ba2 LaTaO6 :Mn4+ and its alkali metal charge compensation for plant growth illumination.

A series of Mn4+ -doped and Mn4+ ,K+ -co-doped Ba2 LaTaO6 (BLT) double-perovskite phosphors was synthesized using a high-temperature solid-state reaction. The phase purity and luminescence properties were also studied. The optimum doping concentration of Mn4+ and K+ was obtained by investigating the photoluminescence excitation spectra and photoluminescence emission spectra. The comparison of BLT:Mn4+ phosphors with and without K+ ions shows that the photoluminescence intensity of K+ -doped phosphors was greatly enhanced. This is because there was a charge difference when Mn4+ ions were doped with Ta5+ ions in BLT. Mn4+ -K+ ion pairs were formed after doping K+ ions, which hinders the nonradiative energy transfer between Mn4+ ions. Therefore, the luminescence intensity, quantum yield, and thermal stability of phosphors were enhanced. The electroluminescence spectra of BLT:Mn4+ and BLT:Mn4+ ,K+ were measured. The spectra showed that the light emitted from the phosphors corresponded well with chlorophyll a and phytochrome PR . The results show that the BLT:Mn4+ ,K+ phosphors had good luminescence properties and application prospects and are ideal materials for plant-illuminated red phosphors.

The predictive value of atherogenic index of plasma for cardiovascular outcomes in patients with acute coronary syndrome undergoing percutaneous coronary intervention with LDL-C below 1.8mmol/L.

BACKGROUND: The potential predictive significance of atherogenic index of plasma (AIP) for cardiovascular outcomes in patients with acute coronary syndrome (ACS) and who have undergone percutaneous coronary intervention (PCI), with low-density lipoprotein-cholesterol (LDL-C) below 1.8mmol/L, has not been well explored. METHODS: The retrospective cohort analysis included 1,133 patients with ACS and LDL-C levels below 1.8mmol/L who underwent PCI. AIP is calculated as log (triglyceride/high-density lipoprotein-cholesterol). Patients were divided into two groups according to the median value of AIP. The primary endpoint was major adverse cardiovascular and cerebrovascular events (MACCEs), a composite of all-cause death, nonfatal myocardial infarction, ischemic stroke or unplanned repeat revascularization. The association between AIP and the prevalence of MACCE was evaluated using multivariable Cox proportional hazard models. RESULTS: Over a median follow-up of 26 months, the incidence of MACCE was higher in the high AIP group compared to the low AIP group (9.6% vs. 6.0%, P log-rank = 0.020), and the difference was mainly derived from an increased risk of unplanned repeat revascularization (7.6% vs. 4.6%, P log-rank = 0.028). After adjusting for multiple variables, elevated AIP was independently associated with an increased risk of MACCE, regardless of whether AIP was considered a nominal or continuous variable (hazard ratio [HR] 1.62, 95% confidence interval [CI] 1.04-2.53 or HR 2.01, 95% CI 1.09-3.73). CONCLUSIONS: The present study demonstrates that AIP is a significant predictor of adverse outcomes in ACS patients undergoing PCI with LDL-C < 1.8mmol/L. These results suggest that AIP may offer supplementary prognostic information for ACS patients with optimally managed LDL-C levels.

NOX2 inhibition stabilizes vulnerable plaques by enhancing macrophage efferocytosis via MertK/PI3K/AKT pathway.

NADPH oxidases 2 (NOX2) is the main source of ROS in macrophages, which plays a critical role in the formation of atherosclerosis. However, effects of NOX2 inhibition on established vulnerable plaques and the potential role involved remain unclear. The purpose of this study is to investigate the latent mechanism of NOX2-triggered vulnerable plaque development. We generated a vulnerable carotid plaque model induced by carotid branch ligation and renal artery constriction, combined with a high-fat diet in ApoE-/- mice. NOX2 specific inhibitor, GSK2795039 (10 mg/kg/day by intragastric administration for 8 weeks) significantly prevented vulnerable plaque, evaluated by micro-ultrasound imaging parameters. A profile of less intraplaque hemorrhage detection, increased collagen-lipid ratio, fibrous cap thickness and less necrotic core formation were also found in GSK2795039 treated group. Mechanistically, reduced 4-HNE, in situ lesional apoptosis and enhanced efferocytosis were involved in mice treated with NOX2 inhibitor. Further analysis in mouse macrophages confirmed the role of NOX2 inhibition in enhancing macrophage efferocytosis by regulating the MertK/PI3K/AKT pathway. In summary, our data defined previously few recognized roles of NOX2 in vulnerable plaque pathogenesis and an undescribed NOX2-ROS-MerTK axis acts involved in regulating macrophage efferocytosis in the formation of rupture-prone vulnerable plaques.

Multimedia fate of sulfamethoxazole (SMX) in a water-scarce city by coupling fugacity model and HYDRUS-1D model.

Increased concentrations of pharmaceutical and personal care products (PPCPs) have raised concerns about their impact on the ecological system and human health. To understand the environmental impact of PPCPs, we evaluated the fate of a typical PPCP of sulfamethoxazole (SMX) in a water-scarce city of Tianjin during 2013-2020 using a coupled model based on the dynamic fugacity model and HYDRUS-1D model. The results showed that the coupled model successfully simulated the reported SMX concentrations in the main fate media of water and soils, which accounted for 46.4 % and 53.0 % with equilibrium concentrations of 135-165 ng/L and 0.4-0.5 ng/g, respectively. The cross-media transfer flux results showed that advection was the prime input path for SMX in water, while degradation was the dominant output path. Wastewater irrigation and degradation were the main transfer processes of SMX in the soil. Moreover, human activities (i.e., emission loads) and climate (i.e., temperature and precipitation) change can significantly affect the concentrations and transfer rate of SMX in the media. These findings provide basic data and methods for the risk assessment of SMX in water-scarce regions.

Pollution caused by mining reshaped the structure and function of bacterial communities in China's largest ion-adsorption rare earth mine watershed.

Ion-adsorption rare earth mining results in the production of high levels of nitrogen, multiple metals, and strong acidic mine drainage (AMD), the impacts of which on microbial assembly and ecological functions remain unclear. To address this knowledge gap, we collected river sediments from the watershed of China's largest ion-adsorption rare earth mine and analyzed the bacterial community's structure, function, and assembly mechanisms. Results showed that bacterial community assembly was weakly affected by spatial dispersion, and dispersal limitation and homogeneous selection were the dominant ecological processes, with the latter increasing with pollution gradients. Bacterial alpha diversity decreased with pollution, which was mainly influenced by lead (Pb), pH, rare earth elements (REEs), and electrical conductivity (EC). However, bacteria developed survival strategies (i.e., enhanced acid tolerance and interspecific competition) to adapt to extreme environments, sustaining species diversity and community stability. Community structure and function showed a consistent response to the polluted environment (r = 0.662, P = 0.001). Enhanced environmental selection reshaped key microbial-mediated biogeochemical processes in the mining area, in particular weakening the potential for microbial denitrification. These findings provide new insights into the ecological response of microbes to compound pollution and offer theoretical support for proposing effective remediation and management strategies for polluted areas.

Soil bacterial community structure in the habitats with different levels of heavy metal pollution at an abandoned polymetallic mine.

Heavy metal pollution caused by mining activities can be harmful to soil microbiota, which are highly sensitive to heavy metal stress. This study aimed to investigate the response of soil bacterial communities to varying levels of heavy metal pollution in four types of habitats (i.e., tailing, remediation, natural recovery, and undisturbed areas) at an abandoned polymetallic mine by high-throughput 16 S rRNA gene sequencing, and to determine the dominant ecological processes and major factors driving the variations in bacterial community composition. The diversity and composition of bacterial communities varied significantly between soil habitats (p < 0.05). Heterogeneous selection played a crucial role in shaping the difference of bacterial community composition between distinct soil habitats. Redundancy analysis and Pearson correlation analysis revealed that the total contents of Cu and Zn were key factors causing the difference in bacterial community composition in the tailing and remediation areas, whereas bioavailable Mn and Cd, total nitrogen, available nitrogen, soil organic carbon, vegetation coverage, and plant diversity were key factors shaping the soil bacterial structure in the undisturbed and natural recovery areas. These findings provide insights into the distribution patterns of bacterial communities in soil habitats with different levels of heavy metal pollution, and the dominant ecological processes and the corresponding environmental drivers, and expand knowledge in bacterial assembly mechanisms in mining regions.

Effects of straw mulching and nitrogen application rates on crop yields, fertilizer use efficiency, and greenhouse gas emissions of summer maize.

Although straw mulching and nitrogen applications are extensively practiced in the agriculture sector, large uncertainties remain about their impacts on crop yields and especially the environment. The responses of summer maize yields, fertilizer use efficiency, and greenhouse gas (GHG) emissions including carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) in the North China Plain (NCP) to two straw management practices (S0: no straw and S1: straw mulching) and two nitrogen application rates (N1: 180 and N2: 210 kg N ha-1) were investigated in field tests in 2018, 2019, and 2020. The highest yields and partial factor productivity (PFP) were obtained by S1N1, followed by S1N2, S0N1, and S0N2. S1N2 had the highest CO2 emissions and greatest CH4 uptake, S0N1 had the lowest CO2 emissions, and S0N2 had the smallest CH4 uptake. The highest and lowest N2O emissions were found in S0N1 and S1N1, respectively. The S1N2 treatment, an extensively applied practice, had the greatest global warming potential (GWP), which was 70.3 % larger than S1N1 and two times more than S0N1 and S0N2. The largest GHG emission intensity (GHGI) of 19.4 was found in the S1N2 treatment, while the other three treatments, S0N1, S0N2, and S1N1, had a GHGI of 10.1, 10.7, and 10.7, respectively according to three tested results. In conclusion, S1N1 treatment achieved a better trade-off between crop yields and GHG emissions of summer maize in NCP.

Effects of no-tillage on greenhouse gas emissions in maize fields in a semi-humid temperate climate region.

Agricultural tillage practices have a significant impact on the generation and consumption of greenhouse gases (GHGs), the primary causes of global warming. Two tillage systems, conventional tillage (CT) and no-tillage (NT), were compared to evaluate their effects on GHG emissions in this study. Averaged from 2018 to 2020, significant decreases of CO2 and N2O emissions by 7.4% and 51.1% were observed in NT as compared to those of CT. NT was also found to inhibit the soil CH4 uptake. In this study, soil was a source of CO2 and N2O but a sink for CH4. The effect of soil temperature on the fluxes of CO2 was more pronounced than that of soil moisture. However, soil temperature and soil moisture had a weak correlation with CH4 and N2O flux variations. As compared to CT, NT did not affect maize yields but significantly reduced global warming potential (GWP) by 8.07%. For yield-scaled GWP, no significant difference was observed in NT (9.63) and CT (10.71). Taken together, NT was an environment-friendly tillage practice to mitigate GHG emissions in the soil under the tested conditions.

Virtual water transfers in Africa: Assessing topical condition of water scarcity, water savings, and policy implications.

Africa is facing an increasing challenge with respect to water scarcity (WS), which is driven by climate change, population growth, and socioeconomic growth combined with inadequate water resources management. In particular, there is significant concern of virtual water (VW) trade, which plays the key role in water resource management and food security sustainability. Using bilateral trade data, this study consistently evaluated the change and balanced trade of major grains, the VW flows, WS status, water dependency (WD), water self-sufficiency (WSS), and water savings/losses within5 African sub-regions and their partners from 2000 to 2020. The ratio of water use to water availability was used to estimate the WS. The WD was quantified by the ratio of the net VW import to the regional water appropriation and the regional water savings/losses were also quantified by multiplying the inter-regional trade by the virtual water content of the imported/exported grains. The overall average trade deficit of African regions was found to increase to -1364.22 × 106 tons and Africa imported 41,359.07 Bm3 of VW from grain products. Green water contributed 79.33% of the total VWI. The WS values for East African countries were >100, indicating overexploitation. Besides, the overall WD in Africa was 465.5% for the studied period. The trade of main grains between Africa and the rest of the planet corresponded to a global water loss of 2820.7 Bm3·yr-1. However, the inter-continental cereal VW trade pattern and high trend will continue in the future. In view of the rising tension of WS, some African countries need to revise international crop trade and water resources conservation policies to promote a more balanced ecosystem. This study exemplifies that decision makers would consider VW flows and water savings/losses for enhancing water use efficiency and fair trading, thus increasing food production in Africa.

Nitrate source apportionment and risk assessment: A study in the largest ion-adsorption rare earth mine in China.

Nitrate (NO3-) pollution in water bodies has received widespread attention, but studies on nitrogen transformation and pollution risk assessment are still limited, especially in rare earth mining areas. In this study, surface and groundwater samples were collected from the largest rare earth mining site in southern China, and analyzed for the hydrochemical and stable isotopic characteristics. The results showed that the NO3- concentrations ranged from 1.61 to 453.11 mg/L, with 35% of surface water and 53.3% of groundwater samples exceeding the WHO standard (i.e., 50 mg/L). Health risk assessment showed that 31.4% of the water samples had a moderate to high non-carcinogenic risk, and the high-risk areas were concentrated in rare earth mining regions. Additionally, adults were more vulnerable to the non-carcinogenic health risks than children. The high variability of δ15N-NO3- (from -6.43 to 17.09‰) and δ18O-NO3- (from -7.91 to 22.79‰) showed that NO3- was influenced by multiple nitrogen sources and transformation processes. Hydrochemistry and isotopic evidence further indicated that NO3- was primarily influenced by nitrification and hydraulic connection between surface and groundwater. The results of the Bayesian mixing model showed that about 70% of NO3- originated from mine drainage and soil N in the rare earth mining area, while more than 90% of NO3- originated from fertilizer, soil N, and manure and sewage in rural and urban areas in the middle and downstream. This study suggests reducing anthropogenic nitrogen discharge (e.g., leaching agents and fertilizer inputs) as the primary means of NO3- pollution control with biogeochemical processes (e.g., denitrification) to further reduce its pollution.

Fluvial CO2 and CH4 in a lowland agriculturally impacted river network: Importance of local and longitudinal controls.

Despite streams and rivers play a critical role as conduits of terrestrially produced organic carbon to the atmosphere, fluvial CO2 and CH4 are seldom integrated into regional carbon budgets. High spatial variability hinders our ability to understand how local and longitudinal controls affect underlying processes of riverine CO2 and CH4 and challenge the prediction and upscaling across large areas. Here, we conducted a survey of fluvial CO2 and CH4 concentrations spanning multiple stream orders within an agriculturally impacted region, the North China Plain. We explored the spatial patterns of fluvial CO2 and CH4 concentrations, and then examined whether catchment and network properties and water chemical parameters can explain the variations in both carbon gases. Streams and rivers were systematically supersaturated with CO2 and CH4 with the mean concentrations being 111 and 0.63 µmol L-1, respectively. Spatial variability of both gases was regulated by network properties and catchment features. Fluvial CO2 and CH4 declined longitudinally and could be modeled as functions of stream order, dissolved oxygen, and water temperature. Both models explained about half of the variability and reflected longitudinal and local drivers simultaneously, albeit CO2 was more local-influenced and CH4 more longitudinal-influenced. Our empirical models in this work contribute to the upscaling and prediction of CO2 and CH4 emissions from streams and rivers and the understanding of proximal and remote controls on spatial patterns of both gases in agriculturally impacted regions.

Evaluation of no-tillage impacts on soil respiration by 13C-isotopic signature in North China Plain.

It is a challenge to characterize soil respiration of crop residue return systems in the North China Plain (NCP) under no-tillage (NT) and conventional tillage (CT) practices. In this study, we addressed the "hot spot" research challenge of impacts of tillage practices on soil carbon storage and soil CO2 emissions in the NCP by 13C-isotopic signature. A short-term (2018-2020) field experiment was conducted with two tillage practices: NT and CT. The results showed that in the tested area, NT had advantages of lower CO2 emissions compared to CT with average reduced CO2 emissions by 10.82%-19.14%. The results of this study suggested that the NT facilitated enhanced soil carbon storage by 2.80%, which was evidenced by the δ13C data. Based on the path analysis model, the main line of soil respiration reduced by NT was attributed to the increased of soil microbial carbon and nitrogen as well as soil moisture in NT, which further increased δ13C and eventually inhibited soil respiration. Overall, adopting NT in NCP is an effective means to improve soil carbon pool and decrease soil CO2 emissions in agriculture practices.