| In the Three Gorges reservoir area,the water blooms caused by water pollution have been attracted much attentions,resulting from completion of the Three Gorges Project,the development of regional agricultural intensification and the advancement of urbanization..Excess nitrogen and phosphorus in rivers are caused by human activities and agricultural production.Phosphorus input is an important cause of water bodies eutrophication,and it is also a major pollutant of non-point source pollution,threatening regional water safety and social and economic development.Therefore,in order to quantify the net nitrogen and phosphorus input caused by human activities and its influence factors in the Three Gorges reservoir area,the potential risk assessment of non-point source pollution was applied.The NAN1,NAPI and PNPI model were established in study by the data of socio-economic,ecological environment,agricultural production,to study the spatial and temporal distribution of net nitrogen and phosphorus input by human activities in this area from 2006 to 2016,and their characteristics,composition and contribution rate.Relevant influencing factors were used to evaluate the spatial distribution characteristics and inter-annual variation of potential non-point source pollution risks in this area from 2000 to 2015.The main results are as follows:(1)The discrepancy between spatial and temporal for NANI and NAPI is significant in the Three Gorges reservoir area.From 2006 to2016,the NANI ranges from 10715.2 to 11974.1kg·km-2·a-1 while the NAPI ranges from 2413.5 to 2911.4 kg·km2·a-1.Their trend were rise and then drop with linear function.the spatial distribution characteristics of NANI and NAPI converge,the overall height of the head of the library,the height of the head of the library,the low of the hinterland of the reservoir area and the library The area is high in the north and low in the south.(2)In the composition of NANI in the Three Gorges reservoir area,the main input source is nitrogen fertilizer application and the proportion is 50%～56%.The minor input source is the atmospheric nitrogen deposition and the proportion is 22%～24%.For the NAPI composition,the proportion of phosphate fertilizer application is 58%～61%,followed by phosphorus input of human food and animal feed,accounting for 29%～30%.The relationship between the application rate of nitrogen fertilizer and NANI is most significant using correlation analysis and R2=0.81(p<0.0001).The relationship between the amount of phosphate fertilizer applied and NAPI is most significant and R2=0.84(p<0.0001).(3)NANI and NAPI strongly related with these factors,such as population density,food production,gross agricultural production and regional GDP,cultivated land area,forest coverage and forest area.NANI and NAPI increased as increasing population density,however,they kept stable when the population density reaches a certain value.NANI and NAPI increased as increasing cultivated land area,while decreased as increasing forest area.(4)In 2015,the potential area suffering from source pollution risk in the Three Gorges reservoir area was extremely low,low,medium,high and extremely high.The proportion of land area in the five grades was 22.87%,29.71%,11.31%,17.09%and 18.98%,respectively.The proportion of high-grade risk zones decreased by 5.3%compared with 2000,and the other risk zones changed little,and the overall trend showed a good trend.(5)The potential non-point source pollution risk in the Three Gorges reservoir area is characterized by the distribution of high west and low east and high north and low south,the closer to the river,the higher risk level is potential source pollution.The extremely high and high risk areas mainly focused on the regional extent of the tail of the reservoir in the core urban area of Chongqing and the core of Yichangchang.In the urban area,the extremely low and low risk areas are mainly concentrated in the Wushan,Badong,Xingshan and the hinterland of the reservoir area in Fengshou,Shizhu,Wulong,etc. |
PDF Full Text Request