| Pollutants from industrial and urban continue to increase and gradually concentrate during the rapid development of urbanization and industrialization. However. The sewage treatment capacity is fall behind the level of economic development, causing the point source pollution load to increase, coupled with nonpoint source pollution. Thus, the water quality of rivers, lakes and other water-bodies in the recent years has a serious degradation, with the aquatic ecosystems function destruction. National ―12Th five-year plan‖ for environmental protection adds the chemical oxygen and ammonia indicators to improve the water environment.But, in some key watersheds, the exceed problems of total nitrogen and total phosphorus are more prominent which severely restrict water environmental quality improvement. This research investigated water quality of Xiaoqinghe Watershed during rainy and dry season in the year 2012-2013. Factor analysis and cluster analysis were conducted to identify spatio-temporal distribution Characteristics of various forms of nitrogen(N) and phosphorus(P) in the watershed. Meanwhile, spatial analysis and correlation analysis were carried out to identify effects of various land use types on N and P export. SWAT model constructed by collecting and analyzing spatial and attribute data in the Xiaoqinghe watershed can characterize the actual situation and simulate the hydrological cycle, sediment transportation, nutrients migration and transformation based on the sensitivity analysis,calibration and verification for parameters. Further analyzing the simulation results ultimately determine the total pollution amount control scheme to meet the requirement of functional area for water quality. The main results of this research are listed as following :1 Nitrogen nutrients are parameters causing water quality impairment throughout the watershed, especially the exceeding standard ratio of total nitrogenis 100%. Ammonia nitrogen(NH4-N) and orthophosphate-phosphorus concentrations(PO4-P) are significantly higher in rainy season than in dry season, whereas nitrate nitrogen concentration is higher in dry season than in rainy season. TN, TP, NH4-N, PO4-Pand TDP concentrations have a significantly positive correlation with percentage of residential and industrial build-up area in the watershed; NO3-Nconcentration is positively correlated with area percentage of cropland and negatively correlated with area percentage of forestland and grassland. Spatially, distribution characteristics of nitrogen and phosphorus by cluster analysis were identified three groups: the first and second groups located on southern part of the watershed, have low area proportion of build-up area and relatively less pollution; on the contrary, the third group locating northern plain of the watershed is seriously polluted by N and P loading from point sources along the stream reaches.2 Non-point source pollution in the Xiaoqinghe watershedhas a larger proportionamong the total anthropogenic emissions. Fertilizer and livestock activities emissions for nitrogen are the most important contributionsource. Fertilizerpollutant sourcehas some differences in space. For example,the annual fertilization density in sub-basins located in Zhangqiu city and Shouguang city are 250~330 kg/ha, higher than the upper safe limit which is 225 kg/ha. the annual emissions of nitrogen and phosphorus from livestock pollutants also has the spatial differences. The nutrient carrying amount of nitrogen per hectare from livestock discharge in Zhangqiu city is as high as 309~351 kg/ha.3 The different pollutant source has different contribution ratio in Xiaoqinghe watershed. Human activities seriously impact on the water quality, in which 97% of the total nitrogen load and 99% of the total phosphorus load into river is caused. The contribution ratios of fertilizer runoff and livestock pollution are 33% and 29% for the total nitrogen loads.The contribution ratios of industrial emissions and residents emissions are55% and 37% for total phosphorus. The rural dwelleremissions have the smallest impact on annual loads for total nitrogen and total phosphorus.4 This research sets up two types of programs based on the simulation results by SWAT model for the point and non-point pollution source. Those scenarios all can improve the water quality, but it still can not achieve the requirement of water function. Controlling the emissions of point source can get better result compared fertilizer and livestock discharge, especially the phosphorus load into river was been cut more than 17% loads. Depending on the reduction effect of different scenarios, the total pollution amount control scenario from point and non-point sources can ultimately meet the water quality requirement of functional area in Xiqoinghe watershed. |
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