Research On Nonpoint Source Pollution Characteristics In Different Forest Lands Around Fushi Reservoir, Anii County

The research on characteristics of soil erosion pollutants under the conditions of openfield was conducted with Chestnut(Castanea mollissima) stand and Bamboo (Phyllostachysedulis)stand by setting up runoff plots in downstream and upstream areas of Fushi Reservoir inAnji county of Zhejiang province. The results showed that there were10runoff events whichhad been observed with the range of rainfall from28.2mm to303mm during March andDecember in2012. The order of pollutant concentration of10runoffs in chestnut stand was,COD(6.12~11.14mg/L)>TN(2.163~5.371mg/L)>NH4+-N(0.733~4.220mg/L)>TP(0.276~1.742mg/L)>NO3--N(0.035~0.433mg/L); and6runoffs in bamboo stand was, COD(0.77~8.87mg/L)>TN(3.424~5.339mg/L)>NH4+-N(0.553~2.140mg/L)>TP(0.222~1.422mg/L)>NO3--N(0.030~1.034mg/L). The concentrations of TN, NH4+-N and COD all had positivecorrelations with rainfall amount（p=0.05）, while TP had negative correlation with rainfallamount（p=0.05） and NO3--N had no correlation with rainfall amount.N was the main loss element for the two forest lands, the average TN concentration ofchestnut stand and bamboo stand were respectively3.707、4.270mg/L; and for TN, they were0.611、0.474mg/L. Meanwhile, they were all higher than the threshold of causing watereutrophication, which indicated that both chestnut and bamboo stands were pollution sourcesof Fushi Reservoir. In addition, N、P and reducing substances losing from chestnut stand weremore than ones in bamboo stand, of which ammonia nitrogen and reducing substances weremore than double of bamboo stand, while TN and TP were a little more, and level of nitratenitrogen lost was less than that of bamboo stand. As a result, chestnut stand contributed morepollutants to the reservoir than bamboo.Plots were set up in chestnut and nearby secondary forest to measure nutrient contents ofsoil samples collected at different layers. Results showed that differences of soil nutrientcontent from the two stands were the biggest at0~20cm profile. Contents of organic matter,TN, hydrolyze nitrogen and effective potassium at0~20cm layer of chestnut stand were lowerby10.81g/kg、0.45g/kg、40.26mg/kg、12.25mg/kg than in secondary forest, respectively.Content of TP and TK had no significant differences, and content of effective phosphorus was2.73mg/kg higher than in secondary forest. Overall, nutrient contents of chestnut stand werelower than that of secondary forest. Since part of forest land was bare due to low plant diversityand the coverage rate of chestnut stand, soil erosion was easy to occur during rainfall events. The soil nutrient reduced in chestnut stand soil was the nutrient been carried and transferred inthe form of soil particles and dissolved of runoff under rainfall, which was the reason whyrunoff of chestnut stand had higher pollutant concentrations.