Source Apportionment Of Planting Non-point Source Pollution In Nansi Lake Basin

Nansi Lake is an important transmission channel and storage lake which would directly influent the water quality of the East Route Project of the South to North Water Transfer. In recent years, non-point source pollution of Nansi Lake basin has been effectively controlled; however, non-point source pollution, especially agricultural non-point source pollution play a key role in affecting eutrophication in the Nansi Lake region. To control and eliminate pollution source is the fundamental measure to prevent and control pollution. Thus, the analysis of the water environment contamination source is the premise for effective controlling water environment pollution. The research on source apportionment of agricultural non-point source pollution in Nansi Lake basin has not been examined well. Therefore, it not only has important scientific significance, but also has very important practical value to study on agricultural non-point source pollution in Nansi Lake basin.This study is in the background of the East Route�'Project of the South to North Water Transfer and under the auspices of the project in the national science and technology program during the eleventh five-year plan period-Agricultural non-point Pollution Load and Control Model along the Lake (Nansi Lake) District (No.2007BAD87B05). Based on the investigation of agricultural non-point source pollution situation and Nansi Lake and its main inflow rivers, the study program and experiment plan are made. Field runoff pools were used to collect the surface runoff samples of farmland, Samples were also collected from the11main rivers of Nansi lake basin and the concentrations of different forms of nitrogen (N) and phosphorus (P) were determined by ion chromatography and other methods. Principle component analysis (PCA) was applied to obtain cropping non-point pollution sources of N and P, and according to the results of source apportionment, agricultural non-point source pollution prevention and control measures of Nansi Lake basin have been proposed. The main contents and results of this study are as follows:(1) The investigation on planting non-point pollution and the main inflow rivers status in Nansi Lake basinStatuses on planting non-point source pollution and the main inflow rivers in Nansi Lake basin were surveyed by the methods of field survey and data access to obtain planting mode, position distribution and situation of the main inflow rivers. The cropping systems in Nansi Lake watershed are mostly wheat-rice rotation, wheat-maize rotation, and garlic-maize rotation, which are distributed in Yutai County, Weishan County and Liangcheng Township, respectively. There are53rivers inflowing into Nansi Lake,29rivers into the upper lake and24rivers into the lower lake.11main rivers are selected with larger area in this study including Si River、Liangji Canal、Baima River、Zhuzhaoxin River、Wanfu River、Fuxin River、Chengguo River、Dongyu River、Guangfu River、Xinxue River、Dsha River.(2)Study of the planting non-point pollution characteristic in Nansi Lake basinField runoff pools were employed in typical experiment districts to collect surface runoff samples of wheat-rice rotation, wheat-maize rotation and garlic-maize rotation in Nansi Lake region and the different forms of nitrogen and phosphorus concentrations and runoff loss load were analysed. The non-point pollution characteristics of three different rotation systems were also obtained. The results showed that, from the point view of the loss concentrations of nitrogen and phosphorus, the loss concentrations of nitrogen and phosphorus in wheat-corn rotation and garlic-corn rotation are similar, but differ significantly with those in wheat-rice rotation. The TN average concentrations in wheat-rice rotation, wheat-maize rotation and garlic-maize rotation were4.33mg/L、10.54mg/L and11.87mg/L, respectively; The TP average concentrations were0.286mg/L、0.158mg/L and0.225mg/L, respectively. The characteristics of NH4+-N loss concentrations were wheat-maize>garlic-maize>wheat-rice, while DP and PO43--P were wheat-rice>garlic-maize>wheat-maize. From the point view of the loss loads of nitrogen and phosphorus, the TN loss loads from wheat-rice rotation, wheat-maize rotation and garlic-maize rotation runoff water were1.31-13.68kg/hm2、5.83-19.27kg/hm2and4.75-32.66kg/hm2and the TP were0.053-0.627kg/hm2、0.021-0.348kg/hm2and0.033-0.578kg/hm2, respectively. (3) Establishment of source profiles and receptor profilesThe source profiles and receptor profiles were established by normalizng the different forms of nitrogen and phosphorus experimental data of water samples in three different cropping systems and the main inflow rivers. The source profiles showed that the losses of N and P had similar profile characteristics in the three different rotation systems. The receptor profiles indicated that the concentrations of nitrogen and phosphorus varied greatly in the main inflow rivers and the concentrations of nitrogen and phosphorus were higher in Guangfu River, Chengguo River, Dongyu River, Fuxin River and Dasha River.(4) Source apportionment for nitrogen and phosphorus of planting non-point sources in Nansi Lake basinAccording to the normalized data of water samples from the main inflow rivers of Nansi Lake, principle component analysis was applied to achieve Source apportionment for nitrogen and phosphorus of planting non-point sources in Nansi Lake basin. The result showed that field surface runoff from the three different rotation systems were the main pollution sources for water eutrophication of Nansi Lake. The first source was from field surface runoff of wheat-maize rotation with wide pollution range and larger contribution, and it contributed50.220%of the total contamination burden; the field runoff pollution from garlic-maize rotation was the second source, whose percentages of contribution were25.119%; the third source was the surface runoff from wheat-rice rotation, it contributed19.937%.(6) Study on planting non-point source pollution prevention and contronl measures in Nansi Lake basinBased on source apportionment results, the contribution rate of nitrogen and phosphorus pollution from the wheat-maize field runoff is the largest. Combined with agricultural non-point source pollution survey and pollution control technology researches at home and abroad, adjusting the land uses and promoting soil testing and fertilizer technology, pollution control and management of wheat-maize rotation were purposefully emphasized. Practical pollution control measures and suggestions suitable for Nansi Lake basin are put forward, which provide the scientific basis for comprehensive governance and pollution control of Nansi Lake basin.