模拟降雨下重庆喀斯特槽谷区径流氮磷元素流失特征

为揭示降雨强度和岩层倾向对喀斯特槽谷区耕层土壤氮磷流失的影响,利用人工降雨装置和可变坡钢槽进行模拟试验,设计坡面坡度为25°,岩石裸露率为15%,岩层倾角为30°,地下孔裂隙度为3%,降雨强度分别为30、60和90mm/h,模拟降雨持续时间为1h。结果表明:1)产流量随着降雨强度的增大而增大,地表产流量表现为裸坡顺层坡逆层坡;地下产流量表现为逆层坡顺层坡裸坡。2)在30mm/h降雨强度条件下径流全氮浓度最高;在60mm/h降雨强度条件下铵态氮浓度和硝态氮浓度最高;磷浓度随着降雨强度的增大而降低;逆层坡的径流氮磷浓度最高。3)氮磷流失量随降雨强度增大而增大,且地下流失量高于地上流失量;不同岩层倾向条件下,氮磷流失量地上表现为裸坡顺层坡逆层坡,地下表现为逆层坡顺层坡裸坡;氮在逆层坡的流失量最多,磷在顺层坡的流失量最多。本研究可为在喀斯特槽谷区布设保水保土措施以及改善土壤质量上针对不同岩层倾向坡方案提供依据。

Runoff nitrogen and phosphorus loss characteristics of Chongqing Karst Trough Valley under simulated rainfall

In order to reveal the influence of rainfall intensity and rock layer tendency on the loss of nitrogen and phosphorus in Karst Trough Valley, a simulation experiment was conducted using artificial rainfall devices and variable slope steel channels. The designed slope was 25°, rock exposed rate was 15%, rock layer dip angle was 30°, and the underground hole fissure degree was 3%. The rainfall intensities were respectively 30, 60, and 90 mm/h, and the rainfall duration time is 1 h. The results showed: 1)The runoff increased with the increase of rainfall intensity. The surface runoffs in descending order was bare slope>bedding slope>reverse slope, and the underground runoffs were reverse slope>bedding slope>bare slope. 2)The concentration of total nitrogen in runoff was the highest under the condition of 30 mm/h rain intensity. The concentration of ammonium and nitrate nitrogen was the highest under the condition of rain intensity of 60 mm/h, while the phosphorus concentration decreased with the increase of rainfall intensity. The concentration of nitrogen and phosphorus reached the highest in the runoff of the slope. 3)The amount of nitrogen and phosphorus loss increased with the increase of rainfall intensity, and the amount of underground loss was higher than that of above-ground loss; under the conditions of different rock formations, the above-ground performances of nitrogen and phosphorus loss in descending order was slope>bedding slope>inverted slope. The performance is inverted layer slope>bedding slope> bare slope; The loss of nitrogen is the most in the inverted layer slope, and the phosphorus loss is the most in the bedding slope. In conclusion, different schemes should be put forward for different rock slopes in terms of water and soil conservation measures and soil quality improvement in Karst Trough Vally.