三峡库区小流域不同土地利用类型“土壤-水体”氮磷含量特征及其相互关系

Characteristics and the Relationship of Nitrogen and Phosphorus in Soil and Water of Different Land Use Types of a Small Watershed in the Three Gorges Reservoir Area

利用长期田间监测数据,分析了三峡库区典型农业小流域不同土地利用类型土壤、浅层地下水氮磷含量分异特征,剖析了坡面土壤氮磷含量与浅层地下水、坡面地表径流氮磷浓度的相互关系.结果表明梯田的土壤TN平均含量显著(P<0.05)高于坡耕地,水田梯田平均含量1.49 g·kg^(-1)最高;旱地坡耕地和桑树套种坡耕地土壤TP平均含量显著高于其它地类;旱地梯田土壤NO_3^--N平均含量最高,离散程度最大.坡面土地利用类型对浅层地下水TN、NO_3^--N浓度影响较大,但对TP浓度影响较小;流域浅层地下水TN浓度与NO_3^--N浓度呈极显著正相关,不同坡面浅层地下水NO_3^--N对TN平均贡献率在67.82%~78.51%之间;浅层地下水TN、NO_3^--N月平均浓度变化规律基本一致,春秋两季农作物施肥后均呈现明显上升趋势.坡面土壤TN平均含量与浅层地下水TN浓度呈显著指数关系,坡面土壤NO_3^--N平均含量与浅层地下水NO_3^--N浓度呈对数关系,但与坡面地表径流TN、NO_3^--N浓度无显著相关性;当坡面地表径流TP浓度>0.1 mg·L^(-1)时,坡面土壤TP平均含量与其呈显著线性相关;坡面地表径流与浅层地下水TN、NO_3^--N浓度均呈显著幂函数关系,且NO_3^--N相关性更好.

Long-term field monitoring data was analyzed regarding the characteristics of nitrogen and phosphorus in the soil and shallow groundwater of different land use types in a typical small watershed of the Three Gorges Reservoir area. Furthermore,the relationships among soil nitrogen and phosphorus contents,concentrations of nitrogen and phosphorus in shallow groundwater,and slope surface runoff were analyzed. The results showed that the average contents of TN and NO_3^--N in terrace soil were significantly higher than those in sloping upland soil（ P〈0. 05）,for which the average content of paddy terrace was highest（ 1. 49 g·kg^（-1））. The average contents of TP in the soil of sloping upland and mulberry-sloping upland were significantly higher than those in the soil of other land types. The average content of NO_3^--N in the soil of dryland terrace was highest of all land use types and its discrete degree was also largest. The slope land use type had greater impact on the concentrations of TN and NO_3^--N in shallow groundwater,but it had little influence on TP concentration. In addition,the shallow groundwater TN concentration and NO_3^--N concentration had significant positive correlation,and the average contribution rate of NO_3^--N to TN in five wells ranged from 67. 82% to 78. 51%. The monthly average concentration of TN and NO_3^--N in shallow groundwater changed little,only showing a significant upward trend after the fertilization stage of the two crops in spring and autumn. The average contents of TN and NO_3^--N in the slope soil were significantly correlated with the TN and NO_3^--N concentrations in the shallow groundwater,but there was no significant correlation between the TN and NO_3^--N concentrations in the surface runoff. When the slope surface runoff TP concentration was 0. 1 mg·L^（-1）,the average content of TP had a significant linear correlation with it. There was a significant power function relationship between the concentrations of TN and NO_3^--N in the surface runoff and concentrations of TN and NO_3^--N in the shallow groundwater,with higher correlation of NO_3^--N concentrations between surface runoff and shallow groundwater.