海南岛河流底泥肥力和重金属污染特征及其风险评价

特征分析及其评价是底泥资源化利用的重要前提,为了解海南岛热带玄武岩地区河流底泥特征及其资源化利用的可能性,选取典型河段塘柳塘为研究对象,采用典型断面布点采样法,对52个底泥样本的重金属和肥力进行检测和评价.结果表明:1)参照第2次全国土壤普查土壤养分分级指标,底泥中全氮质量分数指标达到Ⅰ级水平,全磷、全钾和有机质质量分数均为Ⅱ级水平,阳离子交换量达到Ⅳ级水平;各肥力指标的灰色关联度指数均大于对照区,说明河流底泥养分较为良好.2)采用HJ 332-2006《食用农产品产地环境质量评价标准》,评价底泥重金属污染状况,主要污染物Cd超标率为65.4％,超标幅度为14％;Hg超标率为59.6％,超标幅度为11％.3)地累积指数和内梅罗综合污染指数评价结果显示,该河段底泥中主要污染物为Cd和Hg,河段整体达到中度污染水平.4)潜在生态风险指数评价表明,Hg是最主要的潜在生态风险因子,河段整体达到“轻微生态危害”等级.该研究在海南省南渡江土地整治重大工程中,为疏浚底泥生态改造与土壤资源化利用,提供科学依据和技术支撑.

Fertility,heavy metal pollution characteristics of river sediment and the risk assessment in Hainan Island

[Background]It is pointed in the governmental document of "Water Pollution Control Action Plan" that the water sediment after dredging and disposal,could directly eliminate the phenomenon of black smelly water.The dredged sediment utilization is the main way of land use,ecological restoration materials,construction materials,sewage treatment,etc.Hainan is a unique volcanic tropical island in China,nutrients and heavy metals in sediments formed by unique soil parent material have become the academic research priorities,and the reuse of river sediment can solve the problem of insufficient exogenous soil in land ecological remediation project.Characterization and evaluation is an important prerequisite for sediment resource utilization.In order to understand the characteristics of river sediment in the tropical basalt area of Hainan Island and the possibility of resource utilization,comprehensive and detailed understanding of river sediment heavy metal pollution status,nutrient level and ecological risk,for the river sediment dredging and subsequent resource disposal,is of great significance.[Methods] The typical river pond Tangliutang was selected as the research object,and the typical section distribution point in August 2015 was used.The heavy metals and fertility of 52 sediment samples were tested and evaluated by different evaluation methods.Data was statistically processed by SPSS 22.[Results] 1) According to the index of soil nutrient grading in the second national soil survey,the total nitrogen content in the sediment reached grade I,the contents of total phosphorus,total potassium and organic matter were in grade Ⅱ,and the CEC (Cation Exchange Capacity) reached grade Ⅳ.The gray relational index of each fertility index was higher than that in the control area,which indicated that the nutrient of river sediment was fine.2) Standard " Environmental Quality Evaluation Standards for Farmland of Edible Agricultural Products" (HJ 332-2006) was used to evaluate the heavy metal pollution of the sediment.The main pollutants were Cd and Hg,Cd exceeded the standard by 14％ with 65.4％ samples,and Hg exceeded the standard by 11％ with 59.6％ samples.3) The evaluation results of geo-accumulative pollution index and comprehensive geo-accumulative pollution index (Icgeo) showed that the main pollutants in the river sediment were Cd and Hg,while the river sediment was moderate pollution.4) The evaluation of potential ecological risk index showed that Hg was the most important potential ecological risk factor.The sediment was at the level of "slight ecological hazard" according to comprehensive potential ecological risk index ERI.[Conclusions] Under the situation of above results.Whether or not the sediment can be applied in land reuse is up to each practical case,for instance,it can be used for forest restoration but not for rice planting.This study provides a scientific basis and technical support for the ecological reconstruction and soil resource utilization of dredged sediment in the major land rehabilitation project of Nandu River ndu River in Hainan Province.