科研之友
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摘要
Understanding the output process characteristics of non-point source pollutants on different underlying surfaces is one of the prerequisites for comprehensive management of small watersheds. Taking a typical small watershed in red soil hilly region of Southern China as an example, this study observed and compared the output process of non-point source phosphorus pollution of the main underlying surfaces of forest land, agricultural planting land (orchards and arable land) and construction land (rural roads and roofs) under rainfall conditions. Results showed that all underlying surfaces had high concentrations of pollutants in the early stage of runoff. The average concentration of total phosphorus (TP) on the five main underlying surfaces in typical rainfall events was in a decreasing order of arable land (0.75 mg·L?1), orchard land (0.59 mg·L?1), rural roads (0.38 mg·L?1), forest land (0.25 mg·L?1), and roofs (0.08 mg·L?1).The TP output intensity was in a decreasing order of rural roads (0.07 kg·hm?2), arable land (0.06 kg·hm?2), orchard land (0.04 kg·hm?2), roofs (0.021 kg·hm?2), and forest land (0.019 kg·hm?2). The type of underlying surfaces affected the output composition of non-point source phosphorus. Dissolved phosphorus accounted for the highest proportion of the whole non-point source phosphorus from construction land (51%~71%), followed by forest land (44%), and planting land (25%). The proportion of land use area and phosphorus pollution load contribution ratio of the entire small watershed were in a decreasing order of forest land (87%; 55%), planting land (9%; 42%), and construction land (1%; 3%). Results of this study, together with local rainfall characteristics and soil erosion conditions, can provide scientific guidance for non-point source pollution control in hilly red soil areas in Southern China..
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