Abstract:
The Dongting Lake Plain is one of the most important food production bases in China. However, the non-point source pollution has posed a great threat to social and economic development in the cultivated land, due to a large number of chemical fertilizers and pesticides that have widely been used unreasonably during agricultural production in recent years. It is also very serious for the pollution of livestock and poultry breeding. Taking 21 county-level administrative units in part of Hunan Province in the Dongting Lake Plain as the research area, the inventory analysis was made to construct three types of pollution units for the farmland fertilizer, human and livestock excrement, as well as farmland solid wastes. Some parameters were calculated, including the total emission and intensity of Chemical Oxygen Demand (COD), Total Nitrogen (TN), and Total Phosphorus (TP). The temporal and spatial evolution of non-point source pollution was determined in the cultivated land, further to analyze the movement trajectory of emission intensity barycenter and the degree of spatial agglomeration, using the center of gravity model and the cold/hot spot analysis. The results showed that: 1) There was a great decrease in the total emissions and emission intensity of COD, TN, and TP from the cultivated land non-point source pollution in the study area from 2005 to 2019. It was related to the promotion of ecological farming, soil testing formula technology, as well as the scale control of livestock and poultry breeding. There were also the spatial distribution characteristics of "east>west>central" in the pollution degree for three types of pollutants. 2) Three types of pollutants all moved in the longitude and latitude directions, but there was a more obvious in the east-west direction, where the barycenter of emission intensity presented a tendency to run westward. The adjustment and implementation of pollution prevention policies were attributed to the shift of the barycenter of the emission intensity in the three pollutants. 3) There were significant differences in the spatial patterns of the three pollutants. Specifically, the COD pollution was significantly different, TP was followed, and TN was the smallest in various regions. Hot spots were mostly distributed in the east of the Dongting Lake plain around the basin. The main reason was that these areas were on the edges of the intersection of the Dongting Lake and the Yangtze River, with advantageous location, rapid urbanization and industrialization, and stronger arable land utilization. The cold spots were mostly distributed in Nanxian and the surrounding areas in the middle of the Dongting Lake Plain. The concept of ecological civilization was contributed greatly to the distribution. As a result, much attention needs to pay to the treatment of non-point source pollution in the cultivated land and surrounding counties. Consequently, the non-point source pollution was improved in the cultivated land in the process of ecological civilization construction. There was also a great difference in the degree and control of cultivated land non-point source pollution in various regions. The finding can provide a sound theoretical basis to manage the non-point source pollution of cultivated land.