Research On Control Of Agricultural Non-point Source Pollutants By Riparian Buffer Strips In Typical Sloping Arable Land In Xiangxi Watershed

Agricultural sources have some important impacts on eutrophication and water blooms,what the reasons mainly are due to the large cross-strait farmland slope,land use unreasonable manner,coupled with agricultural chemical fertilizer,Which makes nitrogen,phosphorus and other nutrients with rain runoff into the river and pollute the water.To cut point Source Pollution by constructing the riparian buffer zone system,the article regarded calcareous soils which was important in the basin as a test object,The purpose was to study the process and characteristics of runoff and sediment yield as well as nutrient loss under different rainfall by the artificial simulation rainfall experiments in field;what's more,conducting a scouring test on the former experimental basis in the rain,The aim was in order to explore riparian forest buffers which had effect of the pollutants of runoff under different slope,vegetation type,pollution load,buffer width conditions,This paper's main conclusions as follow:(1)Under different conditions of rainfall,the losses of different forms of nitrogen nutrients in runoff were expressed as peak concentration in the initial rain,then quickly decreased with the rains were,and fluctuated within a small range of variation,the concentration of total phosphorus output was manifested as increased at the beginning,but decreased rapidly and then tended to be stable;the loss concentration of each pollutant in runoff were positively correlated with rainfall intensity;Nitrate turnover rate was higher than ammonia nitrogen,Sediment runoff amount of each nutrient loss with runoff showed a sustained period of increased firstly and then decreased,and changes in rainfall intensity had no effect on the content of each nutrient,nitrogen loss rate was greater than the available phosphorus.(2)The two buffer zones were gradually reduced about the efficiency of runoff reduction with flushing tests time,while the reduction efficiency of various pollutants in runoff were gradually increasing;two buffer zones was a negative correlation with the flushing flow rate about runoff and nitrogen,ammonia nitrogen,total phosphorus in runoff;The reduction efficiency of nitrate was a positive correlation between the flushing flow rate;at the same flow rate,gradient,width condition,the reduction efficiency of Cynodon dactylon buffer strips about runoff,sediment and the total nitrogen,nitrate nitrogen,total phosphorus of runoff was higher than Manila buffer zone under the same flow rate,slope,width condition;But the latter was higher than the former about the removal of ammonia nitrogen.(3)The reduction efficiency of two buffer zones was decreased with slope increasing about runoff and all pollutants of runoff;Executing the nonlinear fitting between sediment reduction rate under each slope runoff with along distance found that the both were logarithmic relationship.The reduction efficiency of Buffer zones for each pollutant was as follows: ammonia nitrogen> TP> nitrate> TN.(4)The reduction efficiency of two buffer zones was increased with the buffer width increasing about various contaminants;The improvement of purification efficiency of buffer zones for pollutants mainly was 30 min ago,and when the width of the buffer zone increased a certain value,the ability of purify runoff pollutants would near stabilize.When the width of Cynodon dactylon buffer increased form 5m to 7m,the promotion rate of purification efficiency about the total nitrogen,total phosphorus and sediment were 2.72%,2.19% and 6.40%.(5)Between the reduction efficiency of various pollutants and distance was logarithmic relationship,considering local conditions and the reduction efficiency of buffer zones,the width of buffer zone was 5m in local riparian buffers.