Validation of an agricultural non-point source(AGNPS)pollution model for a catchment in the Jiulong River watershed,China

This study tested and evaluated the agricultural non-point source （AGNPS） model for the Wuchuan catchment, a typical agricultural area in the Jiulong River watershed, Fujian Province, China. The AGNPS model was calibrated and validated for the study area with observed data on ten storms. The data on eight storms in 2002 were used for calibration while data on two storms were used for validation of the model. Considering the lack of water quality data over a long-term series, a novel method, comparing an internal nested catchment with its surrounding catchment, was used to supplement the less long-term series data. Dual calibration and validation of the AGNPS model was obtained by this comparison. The results indicate that the correlation coefficients were 0.99 and 0.98 for runoff, 0.94 and 0.95 for the peak runoff rate of the large catchment and the small catchment, respectively, and 0.76 for the sediment of the small catchment only. Each pair of correlation coefficients is homogeneous for the same event for the two catchments. With the exception of the sediment yield and particulate phosphorus, the peak runoff rate and other nutrients were well predicted. Sensitivity analysis showed that the Soil Conservation Service curve number and rainfall quantity were the most sensitive parameters, which resulted in high output variations. Erosivity and other parameters had little influence on the hydrological and quality outputs.

Distributed Simulation of Non-Point Source Pollution in Ashi River Basin

In order to get a thorough understanding of non-point source pollution,it is essential to examine its temporal and spatial distribution. A physically-based distributed model,Soil and Water Assessment Tool( SWAT),was used in this research,to quantitatively estimate the NPS load and analyze the temporal and spatial distributions of NPS pollution in Ashi River Basin. The results indicated that SWAT was suitable to simulate stream-flow and water quality in Ashi River Basin. Total Nitrogen which was contributed by NPS( NPS-TN) accounted for 32. 47%-62. 61%,and Total Phosphorus which was contributed by NPS( NPS-TP)accounted for 22. 30%- 57. 85% of the total load respectively. In inter-annual timescale,both NPS-TN and NPS-TP were influenced by stream-flow and fertilizer. However,when compared with fertilizer,NPS pollution was more directly affected by stream-flow. In annual timescale,NPS-TN and NPS-TP mainly occurred in flood season( from May to September). In the aspect of space,spatial differences of NPS-TN and NPS-TP were extremely significant. The spatial variations of NPS pollution were mainly influenced by land use,precipitation,soil and slope.

Spatio-Temporal Distribution of Agricultural Non-Point Source Pollution in Binzhou City Based on Large Computer Data

Based on the relevant statistics on the agricultural non-point source pollution in Binzhou City,we studied the spatio-temporal variation in agricultural non-point source nitrogen pollution and phosphorus pollution in Binzhou City during 2008-2015. The results showed that the agricultural non-point source nitrogen pollution and phosphorus pollution in Binzhou City changed from 114400 t and 28800 t in 2008 to110600 t and 24400 t in 2015,respectively; for the non-point source nitrogen pollution sources,the proportion of chemical fertilizer,manure and domestic sewage changed from 80. 41%,10. 47% and 9. 13% in 2008 to 82. 94%,4. 77% and 12. 29% in 2015,respectively; for the non-point source phosphorus pollution sources,the proportion of chemical fertilizer,manure and domestic sewage changed from 89. 29%,8. 32% and 2. 39% in 2008 to 91. 6%,4. 78% and 3. 62% in 2015,respectively; in 2015,the non-point source nitrogen pollution was most serious in Wudi County and Huimin County and least serious in Zhanhua County; the non-point source phosphorus pollution was most serious in Zouping County and least serious in Wudi County.

Do Water Matrix and Particulate Buffering Capacity Affect the Rate and Extent of P Release?

The aim of this study was to investigate the release of inorganic and organic phosphorus species from particles in rivers and estuaries during resuspension events such as storm, wind and tidal induced turbulence. To achieve this aim, laboratory beaker experiments were designed with autoanalyzer 3 (AA3). The study first investigates phosphorus equilibration in ultra-pure water (UHP) water, biotic river water and abiotic river water under short term and long term conditions. Then, three typical organic and inorganic phosphorus compounds were selected (orthophosphate, phytic acid (PTA) and β-D-glucose-6-phosphate monosodium salt (G-6-P)) to simulate the effect of addition input to river and estuaries in the time period of 150 h. The results show that in a turbulent river, dissolved inorganic phosphorus (DIP) and dissolved organic phosphorus (DOP) will reach equilibrium between the particulate matter and the water column within 24 h. Additional input of DIP or DOP to the river, has different effects to the river nutrients balance. The buffering capacity of the suspended particulate matter (SPM) plays an important role and behavior difference to the inorganic and various organic phosphorus compounds.

DITCHES AND PONDS CAN BE THE SOURCES OR SINKS OF NON-POINT SOURCE POLLUTION:OBSERVATIONS IN AN UPLAND AREA IN THE JINGLINXI CATCHMENT,CHINA

As the common features of agroecosystems,ditches and ponds benefit the irrigation and drainage,as well as intercepting non-point source pollutants.However,most ditch-pond studies have been conducted in lowland areas.To test this source-sink assumption in upland areas,this study made observations on the ecological function of the ditch and pond system in a typical catchment in China.First,the changes in ponds in the catchment were analyzed using high-resolution remote sensing data.Then,the migration of agricultural pollutants in ditches and ponds were analyzed by field sampling and laboratory detection.The results showed that over the past 15 years the length of ditches in the catchment and the number of small ponds(<500 m2)have increased by 32%and 75%,respectively.The rate of change in nutrient concentrations in the ditches and ponds were mostly from-20%to 20%,indicating ditches and ponds can be both sources and sinks for agricultural pollutants.Lastly,the contributing factors were explored and it was found that ditches and ponds are important sinks in dry season.However,during the rainy season,ditches and ponds become sources of pollutants,with the rapid drainage of ditches and the overflow of ponds in upland areas.The results of this study revealed that the ditches and ponds could be used for ecological engineering in upland catchments to balance drainage and intercept pollutants.

Nitrogen and Phosphorus Loss Law and Emission Reduction Effects Under Water and Fertilizer Management Integrated Mode in Dike Paddy Field

To achieve the purpose of reducing farm non-point source pollution, we integrated site specific nitrogen management precise irrigation, controlled drainage, and wetland eco-repair system in dike area of Taihu basin. During investigation, it had given prominence for the water and fertilizer coupling effects of precise irrigation and site specific nutrient management, the characteristics of integration on controlled irrigation, controlled drainage and wetland ecosystem non-point source pollution control. Then the water and fertilizer integrated management mode of paddy field was put forward in Taihu basin where the water production efficiency increased to 1.64 kg. m-3, water saved 37.8%, fertilizer use efficiency raised 15,4%, yield raised 10%, and N, P load decreased 26%-72%. The modern agricultural and farmland ecosystems that control and cut down the farm non-point source pollution came into being, which can be a reference by Taihu basin to control its agricultural non-point source pollution and eutrophicated water body.

Reactive Stream Stabilization for Minimizing Transport of Phosphorus and Nitrogen from Agricultural Landscapes

A reactive stream stabilization (RS2) system based on aluminum as the adsorbent and garden mulch as the organic matter source was designed to minimize release of agricultural nonpoint source pollutants and installed along the bank of the Little Bogue Creek, MS in 2008. The scope of this research was to design, install and assess the performance of a field scale RS2 structure based on results from previous lab scale studies. Concentrations of alum and total organic carbon (TOC) in the RS2 test barrier and surrounding area were measured to evaluate design parameters of RS2 and the removal effectiveness was examined from soils and monitoring wells that were sampled in 2009. The mean concentration of Al from the reactive barrier was 2.1 mg/g and organic matter from the monitoring wells was 4.7 mg/L, values significantly greater than the surrounding area (p < 0.05). Soil Mehlich-3 P and total phosphorus (TP) were decreased by 55% and 30%, and 40% of the TN and 51% of the nitrate in the ground water were removed through the RS2. The design objectives have been satisfied with the installed RS2 system and the initial sampling data shows effective nutrient removal.

Agricultural Phosphorus Management for Environmental Protection: A Review

This review addresses research done over the past 40 years on different aspects of agricultural phosphorus (P) management for environmental protection. Inputs of P are essential for profitable crop production. Long-term application of P to agricultural soils has resulted in elevated levels of soil P. This accumulation may be desirable from an agronomic point of view but it represents a threat to freshwater quality. Indeed, P in runoff from agricultural land is an important component of non-point source pollution and can accelerate eutrophication of lakes and streams. Even very small amounts of P can raise the concentration above the critical value for eutrophication. Excessive eutrophication restricts water use for recreation, industry, and drinking due to the increased growth of undesirable algae and aquatic weeds. Current concerns facing the environmentally sound management of P in agriculture are similar worldwide and revolve around agricultural, economic, and environmental compromises associated with balancing productivity with environmental values. Agricultural P management strategies should be geared towards ensuring that P, a finite earth resource, is not wasted and those soils do not become so enriched with P that there is an unnecessary risk of too much P being mobilized to water from agricultural fields. Approaches, such as soil P testing and either P models or indices have been studied and implemented to mitigate agricultural P losses. Apparently, P indices are preferred instead of P models for this purpose because they are more flexible. A holistic management strategy is therefore suggested by using soil P testing in conjunction with either a P index or a P model.

Linking monitoring and modelling for river basin management:Danish experience with combating nutrient loadings to the aquatic environment from point and non-point sources

Nationwide monitoring of the aquatic environment was initiated in 1988 in Denmark as a means to follow the outcome of the Action Plans for nutrient pollution of the aquatic environment. Five Action Plans have been adopted by the Danish Parliament since 1985 and the nationwide monitoring programme can be used to quantify the outcome as shown by reductions in nutrient discharges from both point and non-point sources. Moreover, the empirical experience gathered from nearly 20 years of monitoring is assisting the development and calibration of models for simulation of nitrogen leaching, nitrogen removal in groundwater and surface waters and the establishment of a P-index all covering the entire land area of Denmark.

Study on phosphorus loss and influencing factors in the water source area

Maintaining drinking water security is a global issue,and phosphorus is a limiting factor affecting drinking water quality.Hence,this study took Fushi Reservoir as a test area,and set up field runoff observation plots around the reservoir catchment,which is covered by moso bamboo stands.Through field observation,the vertical variation of phosphorus loss in different stands of moso bamboo was initially studied.The results showed that:(1)For the vertical dimensions(atmospheric rainfall,stemflow,throughfall,surface runoff)from high to low,the loss of total phosphorus(TP)increased,and the pro-portion of dissolved phosphorus increased from 29.29%(atmospheric rainfall)to 62.76%(surface runoff).(2)Different rainfall factors had various impacts on phosphorus loss at the different vertical levels.The accumulation of rainfall had the greatest impact on surface runoff TP loss,with the correlation coefficient reaching 0.994(P<0.01),while surface runoff particulate phosphorus loss was mostly affected by the average rainfall intensity.(3)Modifying the forest structure in water source areas can reduce the loss of TP via stemflow and throughfall,but the effect on surface runoff TP loss is variable.Thus,it is expected that this novel study can serve as a reference for improving the environmental quality of water source areas,and help in reducing phosphorus loss and controlling non-point source pollution.

Impact of nutrient losses from agricultural lands on nutrient stocks in Dianshan Lake in Shanghai, China

Abstract： The water quality of Dianshan Lake in Shanghai Municipality, China, is impacted by nutrient losses from agricultural lands around the lake. In this study, nine types of agricultural land use were monitored in 2010 and 2011, and a correlation analysis between nutrient losses from agricultural non-point sources （NPS） and nutrient stocks in the lake was conducted over monthly and seasonal time periods. The results indicate that the monthly average concentration of total nitrogen （TN） ranged from 1.41 to 7.34 mg/L in 2010 and from 1.52 to 5.90 mg/L in 2011, while the monthly average concentration of total phosphorous （TP） ranged from 0.11 to 0.26 mg/L in 2010 and from 0.13 to 0.30 mg/L in 2011. The annual loss of TN from agricultural NPS was 195.55 tons in 2010 and 208.40 tons in 2011. The cultivation of water oat made the largest contribution to the loss of TN. The annual loss of TP was 44.58 tons in 2010 and 48.12 tons in 2011, and multi-vegetable cultivation made the largest contribution to the loss of TP. The results of correlation analysis show that the monthly stocks of TN and TP in the lake have a positive correlation with the monthly losses of TN and TP from agricultural NPS. According to the seasonal data, the stocks of TN and TP in the lake both have a much stronger correlation with the losses of TN and TP from agricultural NPS in summer than in other seasons. Agricultural NPS pollution control should be the main focus for the water resource conservation in this area.

改进输出系数模型在农业面源氮磷污染物负荷估算中的应用

There is a great uncertainty in generation and formation of non-point source(NPS)pollutants,which leads to difficulties in the investigation of monitoring and control.However,accurate calculation of these pollutant loads is closely correlated to control NPS pollutants in agriculture.In addition,the relationships between pollutant load and human activity and physiographic factor remain elusive.In this study,a modified model with the whole process of agricultural NPS pollutant migration was established by introducing factors including rainfall driving,terrain impact,runoff index,leaching index and landscape intercept index for the load calculation.Partial least squares path modeling was applied to explore the interactions between these factors.The simulation results indicated that the average total nitrogen(TN)load intensity was 0.57 t km-2 and the average total phosphorus(TP)load intensity was 0.01 t km-2in Chengdu Plain.The critical effects identified in this study could provide useful guidance to NPS pollution control.These findings further our understanding of the NPS pollution control in agriculture and the formulation of sustainable preventive measures.