Study On The Intercepting Process Of Nitrogen And Phosphorus Pollutants In The Buffer Zone System Of Different Vegetation Riparian

In response to the serious agricultural non-point source pollution problem in the Jiulong River Basin in recent years,wechoose 3 kinds of shrub and grass including Pennisetum americanum x P.purpureum,Loropetalum chinense var.rubrum,Photinia fraseri to build different vegetation buffer zones in north creek section of Jiulong River.Field detection of nitrogen and phosphorus pollutants in rainfall runoff by different vegetation buffer zones in 2015-2017 and systematic study on physical and biochemical processes of nitrogen and phosphorus in soil vegetation system in buffer zones were carried out to reveal the(short-term)rainfall runoff and(long-term)purifying mechanism and main controlling factors of nitrogen and phosphorus abatement by different vegetation buffer zones.The main results were as follows:(1)The reduction rates of nitrogen and phosphorus in the rainfall runoff with different vegetation buffer zones on the whole showed the characteristics of herb>shrub+herb>shrub.The reduction effect of different forms of nitrogen and phosphorus was also different,which had a high reduction rate for nitrate nitrogen and total nitrogen.The reduction rate of phosphate and total phosphorus was the second,and the reduction effect of ammonium nitrogen was the worst.The reduction rates of the riparian on the surface and underground runoff were different,but not significant.With the transformation of soil vegetation buffer zones reduction of ammonium nitrogen increased with the decrease of nitrate nitrogen and total nitrogen removal rates were increased,the rate of fluctuation change by phosphate and phosphorus,the growth status of this change was closely related with the vegetation.(2)The initial water content of the plants were between 20.76 and 25.92%,and no significant difference were found.There was a big difference in permeability in different vegetation soil,4 vegetation soil initial infiltration rate and infiltration of the total 5min size comparison are Pennisetum americanum x.purpureum>Photinia fraseri>weeds>Loropetalum chinense var.rubrum.Soil bulk density was an important factor affecting soil permeability,and has a negative correlation with soil permeability,and strong soil permeability also shows high nitrogen and phosphorus reduction rate.(3)The adsorption capacity of phosphate to soil in different buffer zones was significantly higher than that of ammonium nitrogen,and the desorption of ammonium nitrogen was significantly greater than that of phosphate.The adsorption of ammonium nitrogen and phosphate of Loropetalum chinense var.rubrum>Photinia fraseri>Pennisetum americanum x P.purpureum>weeds.Soil clay had a positive correlation with ammonium nitrogen and phosphate adsorption,ammonium nitrogen adsorption and desorption were negatively correlated significantly,while adsorption and desorption in phosphate showed a significant positive correlation.(4)There was significant difference between the 4 vegetation soil net mineralization rate,size for Photinia fraseri>weeds>Loropetalum chinense var.rubrum>Pennisetum americanum x P.purpureum.All of them showed decreasing trend with the increase of culture time,and decreased with the increase of soil depth,but there was no significant difference in net mineralization rate between different vegetation and different depths.The main influencing factors of soil net mineralization rate are:pH value,soil bulk density,TN,DIN,NO3-N、NH4+-N content.(5)There are significant differences in the net mineralization rate of 4 kinds of soil,compared to the size of Photinia fraseri>Loropetalum chinense var.rubrum>weeds>Pennisetum americanum x P.purpureum.On the whole,the denitrification rate of the surface 10cm was the strongest,and the denitrification rate decreased with the increase of soil depth.The main influence factors of soil denitrification rate were:TC,DIN,NO3-N content.(6)The absorption of nitrogen and phosphorus in different vegetation were different after 1 year,due to the higher biomass of Pennisetum americanum x.purpureum growth on nitrogen and phosphorus retention amount were the highest,the holding ability of the vegetation to nitrogen was higher than that of fixed P.The overall fixation of nitrogen and phosphorus in different organs of vegetation is characterized by stem>leaf>root.