Agricultural Non-point Source (Soil Runoff) Pollution Research In Hainan Island

The project is one part of the project Study on Survey and prevention countermeasures of Agricultural Non-point Source Pollution in Hainan, which is conducted by Hainan province’s Environmental Resource Office. In order to analyze the generation process of runoff and sediment erosion, as well as to understand the output coefficient and characteristics of farmland non-point pollutants in different bio-climatic divisions, Hainan Island, which analyzing from the aspects of Bio-climatic Division, geography and physiognomy, soil types, as well as the land utilization modes and so on; the simulative rainfall combined with farmland runoff fields were applied in this paper. The agriculture soil in Hainan mainland was took as the object of study; field observations on the Agricultural Non-point Source Pollution in Hainan were conducted. According to the soil factors, on the level of space, we analyzed the farmlands in Hainan. The agricultural non-point source pollution model (Output coefficient method) was also applied to estimate the farmland area-source pollution load in various administrative division of Hainan province, then to collect the fundamental information of the agricultural non-point source pollution in various cities and counties. The results are of significant instructive and meaningful to protect and administrate the Hainan Provincial environment, as well as to realize the coordinated and sustainable development of agriculture, rural areas, resources and the environment. The specific results are following:(1) the average output coefficient of Agricultural non-point source pollution on Hainan Island, for the runoff, total nitrogen reached 37.19 kg/hm2·a; total phosphorus reaches 3.64 kg/hm2·a; COD reaches 1050.6 kg/hm2·a, and the sediment erosion rate reaches 11367 kg/hm2·a.(2)Under the moderate and heavy rain conditions, the loss of particulate nitrogen and dissolved nitrogen are half and half; while under rainstorm condition, the loss of particulate nitrogen is 80 percent of the total runoff nitrogen; and the particulate phosphorus is the main run off mode of total phosphorus.(3) From the observation and analysis of spatial distribution in Bio-climatic Division, the sequence of average output coefficient of total runoff nitrogen is semi-moist region (52.88 kg/hm2·a)> damp region (46.25 kg/hm2·a)> moist region (40.19 kg/hm2·a)> semi-arid region (16.00 kg/hm2·a); while that of total runoff phosphorus is semi-moist region (5.00 kg/hm2·a)>damp region(4.41 kg/hm2·a)>moist region (4.00 kg/hm2·a)> semi-arid region(1.30 kg/hm2·a); then that of runoff COD is damp region(1489.7 kg/hm2·a)> moist region(1180.5 kg/hm2·a)> semi-moist region(789.7 kg/hm2·a)> semi-arid region(241.8 kg/hm2·a).(4)From the observation and analysis of topography spatial distribution, the sequence of average output coefficient of total runoff nitrogen is Hilly region(87.26 kg/hm2·a)>Plam tableland region(29.66 kg/hm2·a)>Hummocky tableland region (22.92 kg/hm2·a)>Central mountain region (21.85 kg/hm2·a);while that of total runoff phosphorus is Hilly region (8.59 kg/hm2·a)>Plain tableland region (4.42 kg/hm2·a)>Hummocky tableland region (2.12 kg/hm2·a)>Central mountain region (1.33 kg/hm2·a); then that of runoff COD is Hilly region (2394.8 kg/hm2·a)> Plain tableland region (1500.6 kg/hm2·a)> Central mountain region (701.6kg/hm2·a)>Hummocky tableland region (407.0 kg/hm2·a).(5)From the observation and analysis of soil types spatial distribution, the sequence of average output coefficient of total runoff nitrogen is Latosol (50.20 kg/hm2·a)> Rocky soil (41.79 kg/hm2·a)> Paddy soil (29.61 kg/hm2·a)>Lateritic red earths(18.58 kg/hm2·a)>Dry red soil (15.91 kg/hm2·a)\while that of total runoff phosphorus is Rocky soil (5.27 kg/hm2·a)> Paddy soil (4.41 kg/hm2·a)> Latosol (4.27 kg/hm2·a)> Dry red soil (1.38 kg/hm2·a)> Lateritic red earths (1.27 kg/hm2·a); then that of runoff COD is Paddy output (1500.2 kg/hm2·a)> Latosol (1272.4 kg/hm2·a)> Rocky soil (783.2 kg/hm2·a)> Lateritic red earths (662.9 kg/hm2·a)> Dry red soil (207.8 kg/hm2·a).(6)From the observation and analysis of spatial distribution of land ultilization, the output characteristics of agricultural pollution in various rainfall intensities, the average output coefficient of total nitrogen, total phosphorus and COD which runoff from the soils planted Perennial fruit trees were higher than annual crops, reached 43.55 kg/hm2·a,3.73 kg/hm2·a and1131.2 kg/hm2·a, respectively.(7)According to statistics of the administrative divisions in Hainan, the output characteristics of agricultural pollution in different various rainfall intensities,, the highest average output coefficient of total runoff nitrogen is Baoting county, is 85.37 kg/hm2·a; while that of highest total phosphorus is Changjiang county, is 9.04 kg/hm2·a; that of highest COD is Tunchang county, is 2742 kg/hm2·a;and the highest output load of total nitrogen is Qionghai city, is 1554 t/a; In Haikou, the output load of total phosphorus and COD are the highest, are 255 t/a and 7.2×104t/a, respectively.This project is a research of census properties which obtained the fundamental information of Agricultural Non-point Source Pollution in Hainan province. It is of important reference value to control the agricultural non-point pollution, environmental management and further research in Hainan province.