喀斯特坡耕地浅层地下孔(裂)隙发育过程中径流产污特征

降雨径流产生的非点源污染是地下水污染的重要来源,喀斯特坡耕地浅层地下孔(裂)隙养分流失是造成该地区地下水污染的关键因素.通过模拟喀斯特坡耕地地下孔(裂)隙特征,采用人工模拟降雨和室内分析相结合的方法,研究浅层地下孔(裂)隙发育过程中降雨径流产污特征.结果表明:喀斯特坡耕地地下径流产污是一个极其复杂的过程,微度(1%)孔(裂)隙发育的坡耕地径流全氮、全磷和全钾流失量随雨强变化不明显,全氮和全磷流失量均在70 mm·h-1雨强达到最大值;轻度(3%)孔(裂)隙发育的坡耕地全氮、全磷流失量在雨强50 mm·h-1时达到最大值;中度(5%)孔(裂)隙发育的坡耕地全氮、全磷、全钾流失量则在雨强为90 mm·h-1时达到最大值;各孔(裂)隙发育条件下的全氮、全磷、全钾养分流失量对坡度的响应不明显,轻度发育下的全氮和全磷流失量最大,在中度发育条件下,坡耕地土壤中全钾流失总量最大;不同雨强、坡度条件下的地下径流全氮、全磷和全钾次产污模数随地下孔(裂)隙度变化亦不明显,其中全氮次产污模数在4.38~58.72 mg·h-1·m-2,全磷在0.16~3.15 mg·h-1·m-2,全钾在0.16~3.03 mg·h-1·m-2范围变化.

Characteristics of nitrogen,phosphorus and potassium losses in underground runoff of Karst slope farmlands during the developing process of shallow Karst fissure

Non-point source pollution caused by rainfall runoff is an important source of groundwater pollution, and nutrient loss of underground pore fissure in Karst slope is the key factor causing groundwater pollution in Karst region. This study has investigated the characteristics of runoff nitrogen (N), phosphorus (P), potassium (K) loss in the developing process of shallow underground pore fissure by using artificial simulated rainfall experiments, based on simulating shallow underground pore fissure characteristics of slope farmlands in Karst region. Results show that nutrient loss of underground runoff in Karst slope farmlands is a complex process, the loss amount of total N, total P and total K in micro pore (1%) fissure''s slope farmlands significantly changed with the rainfall intensity. The loss of total N and total P reached maximum at 70, 50 and 90 mm·h^-1 rainfall intensity for slope farmlands with pore fissures of 1%, 3% and 5%, respectively. There was no obvious changes between the loss of total N, total P and total K in different pore fissure and slope gradient; the loss of nutrients in slope farmlands reached maximum in mild (3%) porefissure for TN and TP, but in moderate (5%) pore fissure for TK. There was also no obvious changes between individual pollutant modulus of N, P and K and underground pore fissure degree under different rainfall intensity and slope gradient conditions, in which the individual pollutant modulus of N, P and K were changed in the range of 4.38~58.72, 0.16~3.15 and 0.16~3.03 mg·h^-1·m^-2, respectively.