滇西北剑湖表层沉积物中铁锰分布和生态风险

Distribution Characteristics and Ecological Risks of Iron and Manganese in Surface Sediments of Jianhu Lake,Northwest Yunnan Province,China

为了解剑湖表层沉积物铁锰水平空间分布规律及形态特征,揭示其生态风险,使用优化的BCR连续提取法提取了四种形态含量,使用电感耦合等离子体发射光谱仪测定了剑湖表层沉积物中铁锰含量,利用富集因子法和次生原生比值法评价了其生态风险状况。结果如下:①剑湖表层沉积物铁、锰元素平均含量为(40611.89±1659.49)mg·kg^-1、(669.30±27.13)mg·kg^-1,两种元素均从湖东南向湖内其他区域辐射递减;②铁、锰元素不同形态含量顺序分别为残渣态(95.07%)>可还原态(4.35%)>可交换态(0.51%)>可氧化态(0.06%),残渣态(94.55%)>可交换态(3.04%)>可还原态(2.19%)>可氧化态(0.21%);③铁、锰残渣态最高值均在湖东南,可氧化态最高值在泉眼附近;铁可还原态南多北少,可交换态由新水河、黄龙河之间区域向周围辐射递减;锰可交换态最高值位于湖东南,可还原态高值区位于湖西南部、东北部;④生态风险方面,铁锰均处于无污染或中度污染等级,来源均主要为自然富集。

In order to understand the spatial distributions,fraction characteristics and ecological risks of iron and manganese in the surface sediments of Jianhu Lake,the optimized BCR method was used to extract four fractions of iron and manganese,inductively coupled plasma-optical emission spectrometer was used to determine their concentrations,and the enrichment factor method and ratio of secondary and primary phase method were used to evaluate the ecological risks.The following results are got from the research.In Jianhu Lake,the concentrations of iron and manganese in the surface sediments are(40611.89±1659.49)mg·kg^-1 and(669.30±27.13)mg·kg^-1,respectively,and the concentrations of these two elements decrease from the southeast to the north and west areas.The proportions of iron fraction concentrations are in the following orders:iron residue fraction(of 95.07%)>iron reducible fraction(of 4.35%)>iron exchangeable fraction(of 0.51%)>iron oxidizable fraction(of 0.06%).For manganese,manganese residual fraction(of 94.55%)>manganese exchangeable fraction(of 3.04%)>manganese reducible fraction(of 2.19%)>manganese oxidizable fraction(of 0.21%),respectively.The highest value of iron and manganese residue fraction concentrations is in the southeast of the lake,and the highest oxidizable fraction is near the spring.The iron reducible fraction concentrations gradually decrease from south to north,and the exchangeable fraction concentrations diminish along an increasing distance away from the area between the Xinshui River and the Huanglong River.Manganese exchangeable fraction concentration with the highest value is found in the southeast of Jianhu Lake,and the manganese reducible fraction concentrations with the high value are found in the southwest and northeast of the lake.In terms of ecological risks,iron and manganese are at the level of non-pollution or moderate pollution,and natural enrichment is the main source for both of them.