[Scale Effects of Landscape Pattern on Impacts of River Water Quality： A Meta-analysis].

The landscape pattern determines water pollution source and sink processes and plays an important role in regulating river water quality. Due to scale effects, studies on the relationship between landscape pattern and river water quality showed variance at different scales. However, there is still a lack of integrated study on the scale effect of landscape pattern and river water quality dynamics.

[Nitrate Pollution Characteristics and Its Quantitative Source Identification of Major River Systems in China].

Accurate source identification/apportionment is essential for optimizing water NO-N pollution control strategies. This study conducted a meta-analysis based on data from 167 rivers across China from 2000 to 2022 to analyze the spatial and temporal variation patterns of nitrate pollution in seven major river systems and to quantitatively identify the source composition of riverine nitrate. The average （NO-N） in the seven major river systems was （4.

[Estimation of Cropland Nitrogen Runoff Loss Loads in the Yangtze River Basin Based on the Machine Learning Approaches].

A quantitative understanding of cropland nitrogen (N) runoff loss is critical for developing efficient N pollution control strategies. Using correlation analysis, a structural equation model, variance decomposition, and machine learning methods, this study identified the primary influencing factors of total N (TN) runoff loss from uplands (=570) and paddy (=434) fields in the Yangtze River Basin (YRB) and then developed a machine learning-based prediction model to quantify cropland N runoff loss load. The results indicated that runoff depth, soil N content, and fertilizer addition rate were the major influencing factors of TN runoff loss from uplands, whereas TN runoff loss rate from paddy fields was mainly regulated by runoff depth and fertilizer addition rate.

[Estimation of Nitrous Oxide Emission from River System Based on Water Discharge and Dissolved Nitrous Oxide Concentration].

Due to increasing active nitrogen pollution loads, river systems have become an important source of nitrous oxide (NO) in many areas. Due to the lack of monitoring data in many studies as well as the difficulty in estimating intermediate parameters and expressing temporal-spatial variability in current methods, a high level of uncertainty remains in the estimates of riverine NO emission quantity. Based on the monthly monitoring efforts conducted for 10 sampling sites across the Yonganxi River system in Zhejiang Province from June 2016 to July 2019, the temporal and spatial dynamics of riverine NO dissolved concentrations (NO), NO fluxes, and their influencing factors were addressed.

[Dynamic response of riverine nitrate flux to net anthropogenic nitrogen inputs in a typical river in Zhejiang Province over the 1980-2010 period].

Based on long-term records of river water quality and discharge and nitrogen sources as well as the LOADEST model, annual riverine NO3(-)-N flux and net anthropogenic nitrogen input (NANI) were both estimated for a typical river catchment (2 474 km2) in Zhejiang Province over the 1980-2010 period. Historical trends in both riverine NO3(-) -N flux and NANI and their dynamic relationships were then fully addressed. Finally, the contributions of annual NANI, retained nitrogen pools, and natural background sources to riverine NO3(-)-N flux were indentified.

[Bivariate statistical model for calculating phosphorus input loads to the river from point and nonpoint sources].

Based on the hydrological difference between the point source (PS) and nonpoint source (NPS) pollution processes and the major influencing mechanism of in-stream retention processes, a bivariate statistical model was developed for relating river phosphorus load to river water flow rate and temperature. Using the calibrated and validated four model coefficients from in-stream monitoring data, monthly phosphorus input loads to the river from PS and NPS can be easily determined by the model. Compared to current hydrologica methods, this model takes the in-stream retention process and the upstream inflow term into consideration; thus it improves the knowledge on phosphorus pollution processes and can meet the requirements of both the district-based and watershed-based wate quality management patterns.

[Change traits of phosphorous consumption structure in China and their effects on environmental phosphorous loads].

Substance flow analysis was used to construct a model to analyze change traits of China's phosphorous (P) consumption structure from 1980 to 2008 and their influences on environmental phosphorous loads, then the correlation between several socioeconomic factors and phosphorous consumption pollution was investigated. It is found that phosphorous nutrient inputs of urban life and rural life on a per capita level climbed to 1.20 kg x a(-1) and 0.

[Inversion formula of one-dimensional water quality equation for the export loads of nonpoint sources pollution in headwater area].

An inversion formula for the export loads of nonpoint sources pollution in headwater area was established based on one-dimensional water quality equation, and it was used to calculate the pollution loads for tributaries in the headwater catchment of Laohutan Reservoir, in Huzhou City, Zhejiang Province of China. Monte Carlo method was adopted to determine the sensitivity about each input parameter in the inversion formula. Because each sensitive parameter can be measured directly in the inversion formula, so that this approach can decreased calculation error, which is often caused by the parameter estimation.

[Uncertainty analysis of water environmental capacity in the nonpoint source polluted river].

Based on the one-dimension model for river water environmental capacity (WEC) and the statistical analysis of the measured hydrological and water quality variables, a uncertainty analysis method for the WEC in nonpoint source polluted river was developed, which included the sensitivity analysis for input parameters of the model and the probability distributions analysis for the WEC using Monte Carlo simulation approach. The method, which described the uncertainty derived from the adopted information of the river system and the randomicity from the occurrence of nonpoint source pollution, could provide different WEC combined with reliabilities for different hydrological seasons. As a case study, the total nitrogen (TN) WEC in the Changle River located in southeast China was calculated using the method.

[Water environmental capacity calculation model for the rivers in drinking water source conservation area].

Based on the one-dimension model for water environmental capacity (WEC) in river, a new model for the WEC estimation in river-reservoir system was developed in drinking water source conservation area (DWSCA). In the new model, the concept was introduced that the water quality target of the rivers in DWSCA was determined by the water quality demand of reservoir for drinking water source. It implied that the WEC of the reservoir could be used as the water quality control target at the reach-end of the upstream rivers in DWSCA so that the problems for WEC estimation might be avoided that the differences of the standards for a water quality control target between in river and in reservoir, such as the criterions differences for total phosphorus (TP)/total nitrogen (TN) between in reservoir and in river according to the National Surface Water Quality Standard of China (GB 3838-2002), and the difference of designed hydrology conditions for WEC estimation between in reservoir and in river.

[Estimation and allocation of water environmental capacity in nonpoint source polluted river].

Based on the investigation of the application and emission quantities (QAE) of total nitrogen (TN) and total phosphorus (TP) for nonpoint sources in river catchment' s area, included fertilizer applications, livestock and living pollutants emissions, the quantities of TN and TP entered the river were computed by means of export coefficient model in Changle River, southeast China. Self-purification capacities of TN and TP in the reach were also estimated in terms of input-output balance analysis method. According to the provisions of water function planning in the river, the water environment residual capacity (WERC) or the demand for reducing the application and emission (DRAE) of nitrogen and phosphorus in the corresponding catchment were monthly estimated, and WERC and DRAE were respectively allocated among the pollution sources.

Spatial and temporal variations of water quality in Cao-E River of eastern China.

Evaluation and analysis of water quality variations were performed with integrated consideration of water quality parameters, hydrological-meteorologic and anthropogenic factors in Cao-E River, Zhejiang Province of China. Cao-E River system has been polluted and the water quality of some reaches are inferior to Grade V according to National Surface Water Quality Standard of China (GB2002). However, mainly polluted indices of each tributary and mainstream are different.