Nitrogen Attenuation Efficiency At Difference Types Stream Riparian Buffer Zones

With the development of agriculture and stockbreeding, agricultural non-point source pollution have been the main source of water body pollution. The riparian plays a vital role on the protection of surface water quality, they could reduce the different form N concentration from the agricultural land runoff through a series of physical, chemical and biological processes. Studying the effect of the riparian on the nitrogen in the soil water and groundwater attenuation could offer theory basis for the protecting and fathering water environment and provided necessary data for the maintenance of riparian health and scientific management. Our study site located at the fringe of low order stream under agricultural and forested background, we analyzed the concentration of different form N in the soil water and the groundwater from different type of riparian zones, through these data we conferred the attenuation effectiveness on nutrient and the effect on the maintenance water quality of different type of streamriparian buffer zones. The result showed:(1) Due to the disturbance of cultivation and fertilization, the difference of nutrient concentration in soil water and groundwater was found between agricultural and forested background. In the soil water, the concentration of NO₃^--N under the agricultural background was different significantly from that under forested background, with the concentration being 25.8ppm and 8.8ppm respectively; no difference was found in the concentration of NH₄⁺-N, but the concentration from the agricultural background (3.1ppm) was slightly lower than that from the forested background (3.9ppm) , the concentration of total N (75.3ppm) was higher than that from the forested background (70.4ppm) . In the ground water, the concentration of NO₃^--N, NH₄⁺-N, total N (0.6ppm, 1.2ppm, and 45.2ppm) under agricultural background were lower than those under forested background(0.8ppm, 1.4ppm, and 48.9ppm).(2) Under the agricultural background, no significant difference was found in the nutrient concentration of the soil water and the groundwater from non-vegetation riparian with the agricultural background value; While the concentration of NO3-N and total N in the soil water on grass and forest riparian zone were lower than the agricultural background value, but in the groundwater, the value were samiler with agricultural background value; the NH₄⁺-N concentration was slight lower in grass riparian and higher in the forest riparian(3) Under the forested background, due to the diversity of sampling sites the nutrient background value had great difference with those of non-vegetation and forest riparian, the forest background value was higher than those of riparian; there was not significant difference in nutrient concentration of the soil water and underground waterbetween after-cutting non-vegetation riparian and the forest riparian.(4) Under the agricultural background, riparian zones had more higher the attenuation effectiveness for nitrate in soil water. The attenuation effectiveness of non-vegetation riparian was lower (34.6%) , while those of grass and forest riparian were higher (>88.5%) , forest riparian's was the highest, 94.4%.(5) N in the main form of nitrate through the subsurface runoff was put into the stream, the vegetation-covered riparian had high on the nutrient in the soil water. Under 2 type background, the max attenuation effectiveness on nutrient had difference with the difference of nutrient forms.(6) The 12m wide grass riparian and 14.5m wide forest riparian could attenuate the nitrate in the soil water from the agricultural land to protect the water quality.