辽河干流坝间耕地土壤重金属污染特征研究

通过对辽河干流坝间10个断面耕地土壤0~5 cm、5~15 cm、15~30 cm沉积层重金属铜、镉、锌、铅含量测定,评价了该区土壤重金属污染程度,并采用地质累积指数法评价单一重金属污染状况与潜在生态危害指数,综合评价重金属生态危害程度。研究结果表明,该区土壤铜、铅、锌与镉含量均值分别为32.42 mg?kg~(-1)、38.23 mg?kg~(-1)、47.35 mg?kg~(-1)和1.625 mg?kg~(-1);铅、锌含量均值在达牛渡口最大,分别为55.54 mg?kg~(-1)和80.51 mg?kg~(-1);铜、镉含量均值在通江口处最大,分别为50.24 mg?kg~(-1)和3.103 mg?kg~(-1)。除镉外,铅、铜、锌含量各断面不同深度浓度均低于全国土壤环境质量Ⅱ级标准,镉含量均值是全国土壤环境质量Ⅱ级标准的1.70倍,最大值为3.402 mg?kg~(-1);辽河大桥上游干流镉含量是下游镉含量的6.47倍。镉的地质累积指数值在坝间均显污染,其中,辽河大桥以上各断面显强污染。通江口至毓宝台特大桥重金属潜在生态风险指数值最强。各断面镉对多种金属潜在生态风险指数值的贡献达78.77%~98.23%,贡献率与潜在生态危害指数(RI)呈正相关。多种重金属潜在生态风险指数值变化趋势与镉地质积累指数分布趋势相同,最大值出现于通江口断面。

Characteristics of soil heavy metals pollution in cultivated land in zones between ipsilateral dams of Liaohe River

The heavy metals zinc (Zn), lead (Pb), copper (Cu) and cadmium (Cd)] contents in the 0-5 cm, 5-15 cm and 15-30 cm soil depths of zones between ipsilateral dams in ten sections along Liaohe River were detected and the pollution situation of single heavy metal was evaluated using the geological accumulation index method. The potential degree of ecological damage by heavy metals was comprehensively evaluated using potential ecological risk index. The aims of the study were to evaluate the pollution degree of heavy metals, and explore the agricultural safety in zones between ipsilateral dams of Liaohe River. The results showed that the average contents of Cu, Pb and Zn were 32.42 mg·kg-1, 38.23 mg·kg-1 and 47.35 mg·kg-1, respectively. The contents of heavy metals in different sections and at various soil depths were lower than the GradeⅡstandard of the National Soil Environmental Quality Standard. The average content of Cd was 1.625 mg·kg-1, which was 1.70 times higher than the GradeⅡ standard of the National Soil Environmental Quality Standard. While from Zhuer Mountain to Yu-baoTai Grand Bridge, the trend of soil Cd content increased, it decreased from Yubaotai Grand Bridge to the estuary. Then using the Liaohe Bridge as the divide, the average content of Cd in the upper stream region was 6.47 times that in the lower reaches. The geological accumulation indexes of Pb, Cu and Zn in each sample section were all lower than 1.0, but the geo-logical accumulation index of Cd obviously reflected a pollution trend in the study area. Strong pollution in excess of Grade V standard mainly occurred in the upper reaches of Liaohe River. From Tongjiang port to Yubaotai Bridge, potential ecological risk index of various heavy metals was very strong. Hudedian, Daniudukou, on to Liaohe Bridge was an area with a strong ecological hazard. Then the dawn bridge area had a medium ecological hazard. Finally, Lengdong Bridge, Zhaoquan River and Liaohe River estuary constituted the area with slight ecological hazard. The contribution of Cd in various sections to potential ecological risk of multi-metal was 78.77%-98.23%, which was positively correlated with the potential ecological risk index. The performance trend of various heavy metals in terms of potential ecological risk index was similar to the distribution trend in geological accumulation index of Cd, with the maximum value in Tongjiang estuary.