赣西典型小流域河道镉元素迁移规律研究

Migration Rules of Soil Cd in Typical Small Watershed of Western Jiangxi

通过1 km×1 km的网格化区域调查及针对重点异常区的"T"型剖面追踪查证,研究了赣西泸水流域上游干流重金属的分布分配规律,发现泸水沿岸约50~500 m范围内的农田土壤中存在显著的Cd异常带。在山前盆地、岗丘洼地及水库处的表层土壤形成了3处浓集中心,其含量依次为2.00 mg/kg、1.87 mg/kg和1.34 mg/kg,对应的垂向剖面土壤平均含量依次为2.33 mg/kg、0.40 mg/kg和0.19 mg/kg,说明Cd元素扩散受水流控制明显,易在水动力减弱的平缓地带沉积,且异常程度从上游往下游逐渐降低;在河床横断面上,土壤Cd元素在河漫滩、一级阶地、二级阶地、岗坡的平均含量依次为7.73 mg/kg、0.46 mg/kg、0.22 mg/kg、0.18 mg/kg,即微地形随着高程增加,Cd元素含量越低,说明Cd元素主要来源于河流上游,且受微地形影响显著,易沉积于地势低洼处。

Throughing the 1 km×1 km griding investigation and the"T"profile verification in the key anormaly areas,we studied the Cd element distribution of the upstream Lushui river in western jiangxi province.We found that there are significant Cd anormaly zones in the farmland soil about 50~500 m along the Lushui river,and three high value areas are the piedmont basin,hills depression and reservoir,their Cd concentration are2.00 mg/kg,1.87 mg/kg and 1.34 mg/kg,with the corresponding average soil contents in the profile are 2.33 mg/kg,0.40 mg/kg and 0.19 mg/kg respectively.The paper shows that the Cd element diffusion is obviously controlled by flowing,and that it is easy to deposit in the gentle zone with weakened hydrodynamic force,and finally the degree of the Cd anomaly decreases from upstream to downstream.Research shows the Cd average contents in flood plain,first terrace,secondary terrace and slope respectively are 7.73 mg/kg,0.46 mg/kg,0.22 mg/kg and 0.18 mg/kg in the transversal river bed.It illustrates the Cd element content decreases as the microtopography elevation increases;Cd element comes from the upstream of the river;Cd element is affected by microtopography,and Cd element deposits in low-lying areas.