The Agricultural Environment And Pollution Control Of Small Watershed

With the industry and agriculture development of the Dahuofang River Basin, the pollution of this river is becoming more and more serious. Especially, the non-point source pollution of the nitrogen is concerned extensively in recent years, so researching the nitrogen circulation, managing the non-point source pollution of the nitrogen is very crucial for the economic and ecological sustainable development of the river. According to the surveying and analysising of the Dahuofang River Basin's non-point source pollution of the nitrogen in Liaoning Province, this paper estimates the Nitrogen balance of payments of a typical small watershed, the Nitrogen's flowing of agro-ecosystems, the Circulation of nitrogen bringing load to the environment. Provideing a reference for researching and management the nitrogen and other non-point source pollution of hun river. The results of the researching are following:First, chosed the small watershed of the upper reaches of Dahuofang reservoir as the studying aera, and investigated the nitrogen fertilizer applicated rate, the feed and food bought by the farmers, and the manure excreted by the farmers and livestock, then analyzed the non-point source pollution of the nitrogen characteristic of the farmers. The results show that, according to flowing characteristic of the nitrogen in this watershed, divided the farmers into three different types, that is the cultivation-based farmers, the vegetable growers, the traditional farmers. The different types of farmers'pollution load of the nitrogen is in the order of the cultivation-based farmers>the vegetable growers>the traditional farmers, the nitrogen content of farmland are (348±76),(307±127),(213±126) kg·hm-2·a-1. The amount of nitrogen remained in the different type of farmers'farmland is in the order of the vegetable growers> the cultivation-based farmers> the traditional farmers. The amount of nitrogen remained in the farmland are (256±21),(188±52),(168±65) kg·hm-2·a-1.The results still show that the vegetable growers and the cultivation-based farmers are more great threat to the water's quality in this watershed than the other type of farmers. So the two types of farmers should be treated as the focus object of the non-point source pollution of the nitrogen to be prevented. In the nitrogen pollution load in this watershed, the nitrogen released by the farmers and livestock is 28%, and remained in the farmland is 72%, that is the farmland is the main source of nitrogen pollution, and the farmers and livestock is the important source of nitrogen pollution which should not be ignored.Second, using microbial technology to treat the agricultural non-point source pollution of the little watershed.We have used the DL complex microorganism to simulate study indoor, and to treat the sewage of Mantang river, which has been treated as a model to promote. After surveyed, sampled, and tested, analyzed the sample data between before and after the water have been treated, We conclude that using the DL complex microorganism can purify the sewage effectively, that can provide a scientific basis about how to evaluate the results of being used the complex microorganism to change the water's quality, and apply it reasonably. When the water's temperature is at 15-20℃, The average rate of removal the COD is up to 64.2%.But the activation of DL complex microorganism was greatly affected by the water's temperature. When the water's temperature is lower than 13℃, the average rate of removal the COD is only 25%, the DL complex microorganism efficiency of removal the COD in sewage is affected by the low temperature of the water.Third, Researching the using of the land and the pollution emissions' characteristic of the Chaihe river basin, in order to provide the basis for selecting the appropriate riparian buffer zone to control the watershed point source pollution.According to the changing of the Chaihe river upstream's concentration of pollutants from August 2008 to July 2009, we can conclude that,the changing trend of the nitrogen in this area is that, there was a peak in September,and gradually decreased with the time.then there was a new increasing of the concentration in May of the next year. And the changing trend of the phosphor in this area is gradually decreased, although in May 2008 there was a increased of the phosphor's concentration, but compared to August 2008, the concentration was relatively low, that is the concentration reached to the highest in August in a year period. As the region dominats by hills and slopes, the soil erosion is serious, especially in flood season and farming and fertilizing period. So we suggest to develop the riparian buffer zone, and plant the suitable vegetation between the farmland and the river,that can prevent the wind,conservate the soil and water,and retent the pollutants to the river in this area.