三峡水库蓄水对库区弃耕地土壤7种金属元素质量分数的影响

Content of seven soil metals on abandoned farmland in the hydrofluctuation belt of the Three Gorges Reservoir

为探究淹水对三峡库区土壤金属元素质量分数的影响,以典型消落带中的弃耕地为研究区域,于2009年和2013年,研究不同海拔(145~155,155~165,165~175 m),不同深度(0~5,5~10,10~20 cm)土壤的重金属(铜、铁、锌、锰),碱性金属(钙、镁、钠)分布特征及与pH值的相互关系,旨在为该地区生态恢复提供科学理论依据。研究发现:2009年145~165 m土壤4种重金属质量分数为10~20 cm层最高,2013年为0~5 cm层质量分数最高,钙质量分数的最高值均出现在10~20 cm层;经历过4个淹水周期后,2013年165~175 m高程土壤铜、铁、锌和锰质量分数依次为0.065,59.37,0.068和0.069 g·kg^(-1),其质量分数比2009年分别增加了50.75%,18.84%,27.46%,27.44%。淹水导致钙、锰质量分数增多,钠质量分数减少,其中钠质量分数变化幅度最大,随着海拔的升高,2013年较2009年分别减低了60.02%,60.09%和59.82%;另外,除钠与pH值呈极显著负相关(r=-0.615,P<0.01)之外,所测金属指标均与pH值呈正相关。淹水不仅导致不同年份土壤金属的分布特征不完全相同,还导致土壤铜、铁、锌、锰、钙、镁等的累积及钠的流失。

To provide a theoretical reference for soil ecological restoration in the Three Gorges Reservoir area,the impact of fluctuating water levels on the content of metals was explored in typical abandoned farmland from the hydro-fluctuation belt of the Three Gorges Reservoir study area. Distribution characteristics of heavy metals（Cu, Fe, Zn, and Mn） and alkaline metals（Ca, Mg, and Na） at different altitudes（145-155, 155-165, and 165-175 m） for three soil layers（0-5, 5-10, and 10-20 cm） on abandoned farmland were examined in 2009 and 2013. At the same time, Pearson＇s correlation coefficients between soil pH and the content of seven soil metals were assessed. Results showed that the content of the four heavy metals was highest in the 10-20 cm soil layer among three soil layers at 145-165 m in 2009; whereas, those at the 0-5 cm layer were highest among three soil layers in 2013. Ca content was highest in the 10-20 cm soil layer among three soil layers both in 2009 and 2013. At 165-175 m, compared with 2009, in 2013 Cu（0.065 g·kg^-1） increased 50.8%, Fe（59.37 g·kg^-1） increased 18.8%, Zn（0.068 g·kg^-1） increased 27.5%, and Mn（0.069 g·kg^-1） increased 27.4%（mean value of the three soil layers）. Meanwhile, as altitude increased, fluctuating water levels resulted in growing content of Ca and Mn whereas the content of Na reductions of 60.0% at 145-155 m, 60.1% at 155-165 m, and 59.8%（mean value of the three soil layers） at 165-175 m. In addition, the relationship between Na content and pH value was significantly negative（r =-0.615, P〈0.01）; whereas, the other six metals were positive. So, fluctuating water levels led to differences in distribution characteristics of soil metal contents after different years, as well as in accumulation of Cu, Fe, Zn, Mn, Ca, and Mg contents and losses in Na content.