Spatiotemporal variability and environmental effects of greenhouse gases, nutrients, and dissolved carbons in an ice-covered reservoir.

Ice cover restructures the distribution of substances in ice and underlying water and poses non-negligible environmental effects. This study aimed to clarify the spatiotemporal variability and environmental effects of methane (CH4), nitrous oxide (N2O), total nitrogen (TN), total phosphorus (TP), dissolved organic carbon (DOC), and dissolved inorganic carbon (DIC) in ice and water columns during different ice-covered periods. We surveyed the ice-growth, ice-stability, and ice-melt periods in an ice-covered reservoir located in Northeast China. The results showed that underlying water (CH4: 1218.9 ± 2678.9 nmol L-1 and N2O: 19.3 ± 7.3 nmol L-1) and ice (CH4: 535.2 ± 2373.1 nmol L-1 and N2O: 9.9 ± 1.5 nmol L-1) were sources of atmospheric greenhouse gases. N2O concentrations were the highest in the bottom water of the reservoir while CH4 accumulated the most below the ice in the riverine zone. These can be attributed to differences in the solubilities and relative molecular masses of the two gases. Higher concentrations of N2O, TN, TP, DOC, and DIC were recorded in the underlying water than those in the ice due to the preferential redistribution of these substances in the aqueous phase during ice formation. Additionally, we distinguished between bubble and no-bubble areas in the riverine zone and found that the higher CH4 concentrations in the underlying water than those in the ice were due to CH4 bubbles. In addition, we reviewed various substances in ice-water systems and found that the substances in ice-water systems can be divided into solute exclusion and particle entrapment, which are attributed to differences between dissolved and particulate states. These findings are important for a comprehensive understanding of substances dynamics during ice-covered periods.

Water quality assessment and pollution source apportionment in a highly regulated river of Northeast China.

Dams and sluices break down the river continuum, alter the river hydrological regime, and intercept the migration processes of nutrients and pollutants. The regulation of dams and sluices will have great impacts on water quality characteristics in the river basin. In this study, variable fuzzy pattern recognition model (VFPR), principal component analysis/factor analysis (PCA/FA), and the absolute principal component score-multiple linear regression (APCS-MLR) were used to assess the water quality and identify the potential pollution sources in a highly regulated river of Northeast China. A set of water quality variables at three stations were measured from January 2015 to August 2017. The water quality assessment results showed that there were spatial and temporal variations of water quality and the total nitrogen (TN) and fecal coliforms (F. coli) were the major pollution factors of the study river section. Four pollution sources, including industrial effluent source, domestic sewage source, meteorological factor and atmospheric deposition source, and agricultural non-point source, were identified in dry and wet seasons using the PCA/FA method. The APCS-MLR results showed that the industrial effluent source was the main pollution source in dry seasons and had a decrease in wet seasons. While the mean contribution of the domestic sewage source had an increase in wet seasons, influenced by the sewage overflow and the flushing of pollutants during the extreme precipitation, the construction of dams decreased the flow obviously in wet seasons and increased in dry seasons. The increase in pollutants caused by storm runoff and the reduction of dilution water in the river channel could be the main reason for the water quality degradation in wet seasons.

Deposition behavior, risk assessment and source identification of heavy metals in reservoir sediments of Northeast China.

Sediment cores from five reservoirs, located in the Liaoning and Jilin Provinces in Northeast China, were collected to investigate the accumulation and potential toxicity of heavy metals (Fe, Mn, Cu, Cd, Pb, Zn, and Cr) during a sampling campaign in February, 2015. The results showed that all the detected metals accumulated significantly, especially Cd, compared to their respective background values. Among these reservoirs, Biliuhe Reservoir had markedly increasing trends for organic matter and all the metals, among which Mn was elevated by 280% to 3411mg/kg in a core of only 18cm in depth. Xinlicheng Reservoir was characterized by heavy siltation and varying metal distribution due to its regular geometric features and pulsed flood events. The Enrichment factor (EF) and geo-accumulation index (Igeo) indicated Cd was strongly enriched by anthropogenic inputs, with the values of EF and Igeo greater than 8 and 3, respectively. The toxicity assessment calculated using consensus-based sediment quality guidelines (SQGs) implied the whole cores of Tanghe and Dahuofang and the upper cores of Biliuhe, Xinlicheng and Fengman exhibited toxicity to sediment-dwelling organisms. Cr contributed more to Qm-PEC than the other heavy metals, because only Cr exceeded the probable effect concentration (PEC) despite its low enrichment. According to the results of correlation analysis (CA) and principal components analysis (PCA), mining industries and agricultural activities within the basin were the main anthropogenic pollution sources for these heavy metals.

Haeme Oxygenas-1-Induced Liver Regeneration Protects Graft Against Small-for-Size Syndrome in Rats.

BACKGROUND: Haeme oxygenase (HO-1) affords protection against ischemia/reperfusion (I/R) injury; however, its effects on liver regeneration remain poorly explored. Our previous studies have shown that HO-1 is probably involved in liver regeneration, but its role in small-for-size syndrome (SFSS) is still unclear. Therefore, this study aims to investigate the effects of HO-1 on small-for-size graft (SFSG) and the underlying mechanism. METHODS: Knockout of HO-1 rats by TALEN technique. Immunohistochemistry was used to detect HO-1 nuclear translocation. Haeme oxygenase activity was measured by detecting the amount of carbon monoxide (CO) generated from cell lysates. Flow cytometry was used to detect cell apoptosis and cell cycle. Western blot were performed to measure the expression level of HO-1 protein. RESULTS: We identified that HO-1 was involved in SFSG regeneration; HO-1-knockout rats demonstrated significantly decreased liver proliferation and recovery. Interestingly, our results showed HO-1-induced SFSG regeneration was more likely to be the primary protector against SFSS than IRI. Furthermore, we verified the nuclear translocation of HO-1 and its protective effect on hypoxia/reoxygenation (H/R) damage in clone9 cells. Our results indicated that the HO-1 protein itself rather than heme breakdown metabolites might play a key role in liver regeneration. CONCLUSIONS: The HO-1 protein itself rather than its metabolites possess a protective effect on small-for-size graft (SFSG) against SFSS via nuclear translocation.

Effects of storm runoff on the spatial-temporal variation and stratified water quality in Biliuhe Reservoir, a drinking water reservoir.

Stormflow runoff is an important non-point source of pollution in drinking water reservoirs. Storm runoff is usually very turbid and contains a high concentration of organic matter, therefore affecting water quality when it enters reservoirs. In order to investigate the impact of storm runoff on spatial-temporal variation and stratification of water quality during this rainstorm event, the inflow process of the storm runoff was studied through a combination of field investigation and simulation using the Delft3D-Flow model. Water samples were collected from Biliuhe Reservoir at four different periods: before storm runoff, storm runoff flood peak period, 1 week after storm runoff, and 5 weeks after storm runoff. The results showed that the input of storm runoff resulted in a significant increase in the nitrogen (N) and phosphorus (P) in the reservoir water, especially in the reservoir entrance. The concentrations of total nitrogen (TN) and total phosphorus (TP) gradually decreased after the flood peak period; however, the average concentrations of TN and TP in the entire reservoir remained higher than those before the storm runoff levels for an extended duration. The storm runoff will greatly contribute to the contamination of water quality in a reservoir, and the water quality cannot be quickly restored by self-purification in the short term. During the flood peak period, under the influence of density current, the electrical conductivity (EC) and turbidity increased significantly in the water depth of 10-15 m, so that the reservoir water had obvious stratification between 10 and 15 m. The form of pollutants in storm runoff was mostly in particle phosphorus. Total particulate phosphorus (TPP) concentration was 0.015 ± 0.011 mg/L, accounting for 44.12% of total phosphorus (TP) concentration in storm runoff flood peak period. The process of a rainstorm caused runoff, which carried high levels of turbidity, particulate phosphorus, and organic matter. The storm runoff disrupts the stratification of the reservoir water. In terms of vertical distribution, the turbidity in the reservoir area increased to 73.75 NTU. Therefore, the occurrence of significant turbidity density flow in the reservoir is frequently accompanied by intense rainfall events. Gaining insights into the impact of storm runoff on the vertical distribution of reservoir turbidity can help managers in selecting an appropriate inlet height to mitigate high turbidity outflow.

A Patient With Hepatocellular Carcinoma and Lung Metastasis Successfully Underwent Curative Surgery Following the Downstaging Treatment: A Case Report.

Hepatocellular carcinoma (HCC) is the most common primary liver malignancy. Hepatic resection constitutes the major curative treatment option, but a significant proportion of patients are not surgical candidates on initial evaluation. Along with the development of novel therapeutic strategies including targeted therapies and immunotherapies, a few HCCs can achieve tumor downstaging and be curatively resected. A 52-year-old man was diagnosed with HCC with portal vein invasion and extensive pulmonary and lymph node metastasis. Transarterial chemoembolization (TACE) in conjunction with donafenib and sintilimab was given. Primary tumors in the liver largely shrank with almost complete elimination of the lung metastases following treatment. The patient subsequently underwent curative surgery for HCC, and the pathological examination revealed complete necrosis of the tumor. Targeted immunotherapy was continued after surgery and no disease progression was found on the latest follow-up. Advanced HCC with distant metastasis might have an excellent response to combination therapy of TACE with tyrosine kinase-targeted inhibitors and PD-1 blocker, and achieve opportunity for curative surgery. This efficacy may be associated with the remodeling of immune microenvironment and angiogenesis. HCC is extremely heterogeneous, and the response to therapeutics varies among patients. There is a lack of useful biomarkers to predict therapeutic efficacy, which needs further studies.

Bubbles dominated the significant spatiotemporal variability and accumulation of methane concentrations in an ice-covered reservoir.

Climate-sensitive ice-covered reservoirs are critical components of methane (CH4) release. However, the mechanisms that influence CH4 dynamics during ice-covered periods remain poorly studied. To investigate the effects of bubbles on CH4 dynamics, we conducted intensive field and incubation experiments in an ice-covered reservoir (ice growth, stability, and melt period) in Northeast China. We found that the mean dissolved CH4 concentrations in the ice (625.9 ± 2419.7 nmol L-1) and underlying water (1218.9 ± 2678.9 nmol L-1) were high, making them atmosphere CH4 sources. The visible bubble bands (bubble area) in the riverine zone and the vertical profile of the CH4 concentration in the ice reflect the distribution of trapped bubbles. The mean CH4 concentration in the ice of the bubble area (1674.8 ± 3926.8 nmol L-1) was 2 orders of magnitude higher than that of no-bubble area (53.7 ± 9.2 nmol L-1). Moreover, a large amount of CH4 accumulated under the ice in the bubble area. These findings suggest that bubbles determine the CH4 storage in ice and CH4 accumulation in the underlying water. Ice growth increases CH4 storage in ice and the underlying water because of the entrapment and re-dissolution of CH4 bubbles. However, ice melting releases the CH4 accumulated in the ice and underlying water. A comparison of the field and incubation experiments indicated that the deep-water environment of the reservoir had a CH4 burial effect. Stepwise regression analysis revealed that higher sediment organic matter content, median particle size, and porosity increased the production and release of CH4 bubbles, trapping more CH4 bubbles in ice. Overall, this study improves the mechanistic understanding of CH4 dynamics and predictability of CH4 emissions during ice-covered periods.

Water limitation regulates positive feedback of increased ecosystem respiration.

Terrestrial ecosystem respiration increases exponentially with temperature, constituting a positive feedback loop accelerating global warming. However, the response of ecosystem respiration to temperature strongly depends on water availability, yet where and when the water effects are important, is presently poorly constrained, introducing uncertainties in climate-carbon cycle feedback projections. Here, we disentangle the effects of temperature and precipitation (a proxy for water availability) on ecosystem respiration by analysing eddy covariance CO2 flux measurements across 212 globally distributed sites. We reveal a threshold precipitation function, determined by the balance between precipitation and ecosystem water demand, which separates temperature-limited and water-limited respiration. Respiration is temperature limited for precipitation above that threshold function, whereas in drier areas water limitation reduces the temperature sensitivity of respiration and its positive feedback to global warming. If the trend of expansion of water-limited areas with warming climate over the last decades continues, the positive feedback of ecosystem respiration is likely to be weakened and counteracted by the increasing water limitation.

CT-based radiomics research for discriminating the risk stratification of pheochromocytoma using different machine learning models: a multi-center study.

OBJECTIVES: The purpose of this study was to explore and verify the value of various machine learning models in preoperative risk stratification of pheochromocytoma. METHODS: A total of 155 patients diagnosed with pheochromocytoma through surgical pathology were included in this research (training cohort: n = 105; test cohort: n = 50); the risk stratification scoring system classified a PASS score of < 4 as low risk and a PASS score of ≥ 4 as high risk. From CT images captured during the non-enhanced, arterial, and portal venous phase, radiomic features were extracted. After reducing dimensions and selecting features, Logistic Regression (LR), Extra Trees, and K-Nearest Neighbor (KNN) were utilized to construct the radiomics models. By adopting ROC curve analysis, the optimal radiomics model was selected. Univariate and multivariate logistic regression analyses of clinical radiological features were used to determine the variables and establish a clinical model. The integration of radiomics and clinical features resulted in the creation of a combined model. ROC curve analysis was used to evaluate the performance of the model, while decision curve analysis (DCA) was employed to assess its clinical value. RESULTS: 3591 radiomics features were extracted from the region of interest in unenhanced and dual-phase (arterial and portal venous phase) CT images. 13 radiomics features were deemed to be valuable. The LR model demonstrated the highest prediction efficiency and robustness among the tested radiomics models, with an AUC of 0.877 in the training cohort and 0.857 in the test cohort. Ultimately, the composite of clinical features was utilized to formulate the clinical model. The combined model demonstrated the best discriminative ability (AUC, training cohort: 0.887; test cohort: 0.874). The DCA of the combined model showed the best clinical efficacy. CONCLUSION: The combined model integrating radiomics and clinical features had an outstanding performance in differentiating the risk of pheochromocytoma and could offer a non-intrusive and effective approach for making clinical decisions.

Wnt/ß-catenin signaling enhances hypoxia-induced epithelial-mesenchymal transition in hepatocellular carcinoma via crosstalk with hif-1α signaling.

Epithelial-mesenchymal transition (EMT) is a critical process for tumor invasion and metastasis. Hypoxia may induce EMT, and upregulated ß-catenin expression has been found in various tumors. In this study, we investigate the role of ß-catenin in hypoxia-induced EMT in hepatocellular carcinoma (HCC). Induction of EMT in HCC cell lines by hypoxia was confirmed by altered morphology, expression change of EMT-associated markers and enhanced invasion capacity. We showed that hypoxia-induced EMT could be enhanced by addition of recombinant Wnt3a while it was repressed by ß-catenin small interfering RNA. An interaction between ß-catenin and hypoxia-induced factor-1α (hif-1α) was found, and an underlying competition for ß-catenin between hif-1α and T-cell factor-4 was implied. Notably, increased hif-1α activity was accompanied with more significant EMT features. We also showed that the pro-EMT effect of ß-catenin in hypoxia was deprived in the absence of hif-1α. Moreover, ß-catenin was found to be responsible for the maintenance of viability and proliferation for tumor cells undergoing hypoxia. We further showed a correlation between hif-1α and ß-catenin expression, and corresponding expression of EMT-associated markers in human HCC tissues. Our results suggest that Wnt/ß-catenin signaling enhances hypoxia-induced EMT in HCC by increasing the EMT-associated activity of hif-1α and preventing tumor cell death.

Temporal and spatial characteristics of flocculated suspended solids in a deep reservoir: an in situ observation in the Biliuhe Reservoir.

The amount of total suspended solids (TSS) is the most visible indicator for evaluating water quality in reservoirs. Previous investigations paid more attention to TSS of the surface layer in reservoirs, while suspended particles are prone to settle, resuspend, and aggregate at the bottom of reservoir. There may be different patterns of the TSS in different depths. This study is to assess the TSS concentration by weight analysis, find the evidence of the existence of flocculated suspended particles by in situ underwater imaging analysis, and discuss the impact of the flocculation process of suspended solids on water quality in deep reservoirs. Although the TSS concentration is lower than other reservoirs with the same trophic level, many flocs were found at the bottom of the deep-water area (> 15 m) in the Biliuhe Reservoir according to the recordings of the in situ underwater camera. The further comprehensive analysis demonstrates that the fine particle in flood season and resuspension is the main source of suspended flocs at the bottom of the reservoir. While the slow settling velocity results in the flocculation of fine suspended particles and long-term residence in the bottom layer of the reservoir. TSS has a significant correlation with iron and total phosphorus. Resuspension, flocculation, and settling impact on the transport of suspended sediment and associated contaminants. The evidence from this study suggests that the impact of flocs on water quality should be further discussed to ensure water supply safety.

Integrating fractional amplitude of low-frequency fluctuation and functional connectivity to investigate the mechanism and prognosis of severe traumatic brain injury.

Objective: Functional magnetic resonance imaging (fMRI) has been used for evaluating residual brain function and predicting the prognosis of patients with severe traumatic brain injury (sTBI). This study aimed to integrate the fractional amplitude of low-frequency fluctuation (fALFF) and functional connectivity (FC) to investigate the mechanism and prognosis of patients with sTBI. Methods: Sixty-five patients with sTBI were included and underwent fMRI scanning within 14 days after brain injury. The patient's outcome was assessed using the Glasgow Outcome Scale-Extended (GOSE) at 6 months post-injury. Of the 63 patients who met fMRI data analysis standards, the prognosis of 18 patients was good (GOSE scores ≥ 5), and the prognosis of 45 patients was poor (GOSE scores ≤ 4). First, we apply fALFF to identify residual brain functional differences in patients who present different prognoses and conjoined it in regions of interest (ROI)-based FC analysis to investigate the residual brain function of sTBI at the acute phase of sTBI. Then, the area under the curve (AUC) was used to evaluate the predictive ability of the brain regions with the difference of fALFF and FC values. Results: Patients who present good outcomes at 6 months post-injury have increased fALFF values in the Brodmann area (7, 18, 31, 13, 39 40, 42, 19, 23) and decreased FC values in the Brodmann area (28, 34, 35, 36, 20, 28, 34, 35, 36, 38, 1, 2, 3, 4, 6, 13, 40, 41, 43, 44, 20, 28 35, 36, 38) at the acute phase of sTBI. The parameters of these alterations can be used for predicting the long-term outcomes of patients with sTBI, of which the fALFF increase in the temporal lobe, occipital lobe, precuneus, and middle temporal gyrus showed the highest predictive ability (AUC = 0.883). Conclusion: We provide a compensatory mechanism that several regions of the brain can be spontaneously activated at the acute phase of sTBI in those who present with a good prognosis in the 6-month follow-up, that is, a destructive mode that increases its fALFF in the local regions and weakens its FC to the whole brain. These findings provide a theoretical basis for developing early intervention targets for sTBI patients.

Quantifying the effects of conservation practices on soil, water, and nutrients in the Loess Mesa Ravine Region of the Loess Plateau, China.

A large number of soil and water conservation programs have been implemented on the Loess Plateau of China since the 1950s. To comprehensively assess the merits and demerits of the conservation practices is of great importance in further supervising the conservation strategy for the Loess Plateau. This study calculates the impact factors of conservation practices on soil, water, and nutrients during the period 1954-2004 in the Nanxiaohegou Catchment, a representative catchment in the Loess Mesa Ravine Region of the Loess Plateau, China. Brief conclusions could be drawn as follows: (1) Soil erosion and nutrient loss had been greatly mitigated through various conservation practices. About half of the total transported water and 94.8 % of the total transported soil and nutrients, had been locally retained in the selected catchment. The soil retained from small watersheds do not only form large-scale fertile farmland but also safeguard the Yellow River against overflow. (2) Check dam was the most appropriate conservation practice on the Loess Plateau. In the selected catchment, more than 90 % of the retained soil and water were accomplished by the dam farmland, although the dam farmland occupied only 2.3 % of the total area of all conservation measures. Retention abilities of the characteristic conservation practices were in the following order: dam farmland > terrace farmland > forest land and grassland. (3) The conservation practices were more powerful in retaining sediment than in reducing runoff from the Loess Plateau, and the negative effects of the conservation practices on reducing water to the Yellow River were relatively slight.

Assessment of a Multifunctional River Using Fuzzy Comprehensive Evaluation Model in Xiaoqing River, Eastern China.

Rivers are beneficial to humans due to their multiple functions. However, human meddling substantially degrades the functions of rivers and constitutes a threat to river health. Therefore, it is vital to assess and maintain river function. This study used the Xiaoqing River in Shandong Province, China, as a case study and established a multilayered multifunctional river evaluation indicator system consisting of environmental function, ecological function, social function, and economic function. The weights of indicators were calculated using the analytic hierarchy process (AHP) and the entropy method. Furthermore, a fuzzy comprehensive evaluation model based on the Cauchy distribution function was developed to assess the operation status of each function in each river segment. The results of the indicator and criterion layers in different river sections varied. The multifunctionality of the river decreased from upstream to downstream. The Jinan section was the most multifunctional, followed by the Binzhou, Zibo, and Dongying sections, and finally the Weifang section. Through additional analysis, this study determined the constraint indicators and functions of each river section. Overall, the results reveal that the idea of a "multifunctional river" can advance the theoretical understanding of a river's function, and the fuzzy comprehensive evaluation model is demonstrated to provide fresh perspectives for evaluating river function.

Accumulation characteristic of nitrogen in reservoirs during the ice-covered period under superimposed influence of ice and sediments: A case study of Biliuhe reservoir.

Reservoirs located in middle and high latitudes freeze for months in winter, where the accumulation characteristics of pollutants are changed by superimposed influence of salt exclusion from ice on the surface and pollution release from sediments at the bottom. Taking total nitrogen (TN) of Biliuhe reservoir in Northeast China as an example, we developed a model to simulate TN accumulation characteristics influenced by ice and sediments during the freezing period (NACISF), and quantified contributions of TN from ice and sediments. Model parameters of ice and sediments were determined by laboratory freeze-up simulation experiment and sediment release flux simulation experiment, and water quality data were obtained from field investigations. Results showed that the annual average amount of TN input during the ice-covered period from 2015 to 2020 was 220.77 t, the output was 400.11 t, and the accumulated amount was 589.52 t. TN excluded from ice and released from sediments contributed 8.12% and 7.17% of the total TN inputs in winter, respectively. Analysis showed that the TN excluded from ice was positively correlated with ice thickness and initial TN concentration. The maximum ice thickness of Biliuhe reservoir had a 13 year cyclic feature, and the proportion of TN excluded from ice to the total TN inputs in different periods ranged from 10.68% to 17.30% (mean 13.18%). Meanwhile, TN accumulated seasonally as summer > autumn > winter > spring. The TN exclusion effect in 2050 would be weakened when considering the combined effects of climate change and human activities, with a reduction of about 40.85% compared to the current. It is concluded that the NACISF model took into account the influences of both ice and sediments, which provided a detailed understanding of the accumulation characteristics of TN during freezing period, and had important reference significance for water quality management in winter.

Removal process of phosphorus during the settlement of particulates with runoff and its implication for reservoir management.

Substantial particulates and phosphorus (P) loads are carried into the reservoir by flood runoff and the P exchange between water and settling particulates under variable water conditions in the reservoir after flooding is critical to the removal of active P from water. To investigate the impact of particulate sedimentation on P changes in reservoir water, runoff samples were collected at four locations in the upstream channels of two reservoirs after a rainstorm. Two batches of particulate sedimentation simulations were conducted separately in four plexiglass columns to analyze the changes of water P and environmental factors during particulate sedimentation. The results showed that the contents of total P (TP), total particulates P (TPP), and phosphate (PO43-) decreased with the settlement of particulates. The correlation between the environmental factors and the amount of PO43- in water changed from uncorrelated to correlated with particulate settlement, implying that the rapid settling of particulates might weaken the effect of environmental factors on P exchange between water and particulates. Particulates firstly release PO43- rapidly in river or reservoir and then adsorb PO43- slowly during settlement in reservoirs. Coarse particulates release more and adsorb less PO43- during settlement, and fine particulates play an important role in the removal of water PO43- due to the slow sedimentation rates. Therefore, to mitigate the reactive P content of reservoir water, the loss of coarse particulates from the watershed should be controlled, and the discharge of water with particulates downstream should also be avoided during the flood season.

Pollution Source Apportionment and Water Quality Risk Evaluation of a Drinking Water Reservoir during Flood Seasons.

Reservoirs play an important role in the urban water supply, yet reservoirs receive an influx of large amounts of pollutants from the upper watershed during flood seasons, causing a decline in water quality and threatening the water supply. Identifying major pollution sources and assessing water quality risks are important for the environmental protection of reservoirs. In this paper, the principal component/factor analysis-multiple linear regression (PCA/FA-MLR) model and Bayesian networks (BNs) are integrated to identify water pollution sources and assess the water quality risk in different precipitation conditions, which provides an effective framework for water quality management during flood seasons. The deterioration of the water quality of rivers in the flood season is found to be the main reason for the deterioration in the reservoir water quality. The nonpoint source pollution is the major pollution source of the reservoir, which contributes 53.20%, 48.41%, 72.69%, and 68.06% of the total nitrogen (TN), phosphorus (TP), fecal coliforms (F.coli), and turbidity (TUB), respectively. The risk of the water quality parameters exceeding the surface water standard under different hydrological conditions is assessed. The results show that the probability of the exceedance rate of TN, TP, and F.coli increases from 91.13%, 3.40%, and 3.34%, to 95.75%, 25.77%, and 12.76% as the monthly rainfall increases from ≤68.25 mm to >190.18 mm. The risk to the water quality of the Biliuhe River reservoir is found to increase with the rising rainfall intensity, the water quality risk at the inlet during the flood season is found to be much greater than that at the dam site, and the increasing trend of TP and turbidity is greater than that of TN and F.coli. The risk of five-day biochemical oxygen demand (BOD5) does not increase with increasing precipitation, indicating that it is less affected by nonpoint source pollution. The results of this study can provide a research basis for water environment management during flood seasons.

Flood impact on the transport, transition, and accumulation of phosphorus in a reservoir: A case study of the Biliuhe Reservoir of Northeast China.

Stormflow runoff is the most important agent for phosphorus (P) input to reservoirs, as the particulates contained in runoff carry a substantial amount of P. The settling process of particulates affects the P content of water, and the distribution of particulates determines the P distribution in reservoir sediment. An understanding of flood impacts on the transport, transition, and accumulation of P in a reservoir is critical to reservoir management. In this study, water samples before and after flooding and sediment samples after flooding were collected from Biliuhe Reservoir in Northeast China. P content and load in the water and P-fractions and particle sizes of the sediments were analyzed. Results showed that total particulate P (TPP) increased sharply from 1.56 to 26.72 t after flooding, whereas dissolved organic P (DOP) decreased markedly from 3.24 to 1.17 t, which was largely caused by biological uptake directly or indirectly before flooding. Orthophosphate (PO43-) shared a similar trend with TPP, indicating that PO43- could be adsorbed onto settling particulates, helping to reduce the reactive P introduced by flooding. Reservoir sediment showed a fining trend downstream and the clay fraction exhibited an obvious correlation with P-fractions, demonstrating that the distribution of particulate matter determined P distribution in the sediment. This study also found that particulates from the largest tributary (Biliu River) were only minimally transported from its reservoir entrance to the dam because of a longer travel distance, while contrastingly, particulates from a smaller tributary (Bajia River) were maximally carried to the dam because of a shorter distance. Our fundings suggests that surface water in the reservoir should be released prior to flooding in order to mitigate control of P in the water, moreover, it is necessary to strengthen the effectiveness of pollutant control projects at the reservoir entrance of the Bajia River.

Nonpoint-source nitrogen and phosphorus behavior and modeling in cold climate: a review.

Pollution from nonpoint-source (NPS) nitrogen (N) and phosphorus (P) are the main causes of eutrophication in lotic, lentic and coastal systems. The climate of cold regions might play an important role in disturbing environmental behavior of NPS N and P, influencing simulation of watershed scale hydrologic and nonpoint-source pollution models. The losses of NPS N and P increase in regions of cold climate. In cold seasons, accumulations of N and P are accelerated in soil with increasing fine root and aboveground biomass mortality, decreasing plant nutrient uptake, as well as freezing soil. N and P transformation is disturbed by soil frost and snow. Moreover, factors such as physical disruption of soil aggregates, pollutant accumulation in snowpack, and snow melting can all increase the NPS N and P losses to the waterbody. Therefore, NPS N and P in first flush are more serious in cold climate. All these effects, especially frozen soil and snowpack, make great challenges to watershed scale hydrologic and nonpoint-source pollution models simulation in cold climate. Model improvements of snowmelt runoff, nutrient losses in frozen soil, as well as N and P behavior have been initiated and will be continued to evaluate in terms of their performances and suitability with different scale, hydrologic and geologic conditions in the future.

Response of a Coastal Groundwater System to Natural and Anthropogenic Factors: Case Study on East Coast of Laizhou Bay, China.

With a shifting climate pattern and enhancement of human activities, coastal areas are exposed to threats of groundwater environmental issues. This work takes the eastern coast of Laizhou Bay as a research area to study the response of a coastal groundwater system to natural and human impacts with a combination of statistical, hydrogeochemical, and fuzzy classification methods. First, the groundwater level dynamics from 1980 to 2017 were analyzed. The average annual groundwater level dropped 13.16 m with a descent rate of 0.379 m/a. The main external environmental factors that affected the groundwater level were extracted, including natural factors (rainfall and temperature), as well as human activities (irrigated area, water-saving irrigated area, sown area of high-water-consumption crops, etc.). Back-propagation artificial neural network was used to model the response of groundwater level to the above driving factors, and sensitivity analysis was conducted to measure the extent of impact of these factors on groundwater level. The results verified that human factors including irrigated area and water-saving irrigated area were the most important influencing factors on groundwater level dynamics, followed by annual precipitation. Further, groundwater samples were collected over the study area to analyze the groundwater hydrogeochemical signatures. With the hydrochemical diagrams and ion ratios, the formation of groundwater, the sources of groundwater components, and the main hydrogeochemical processes controlling the groundwater evolution were discussed to understand the natural background of groundwater environment. The fuzzy C-means clustering method was adopted to classify the groundwater samples into four clusters based on their hydrochemical characteristics to reveal the spatial variation of groundwater quality in the research area. Each cluster was spatially continuous, and there were great differences in groundwater hydrochemical and pollution characteristics between different clusters. The natural and human factors resulted in this difference were discussed based on the natural background of the groundwater environment, and the types and intensity of human activity.