武夷山五夫荷塘底泥重金属赋存特征及其生物有效性

Speciation and Bioavailability of Heavy Metals in Sediment of Lotus Ponds from Wufu Downtown,Wuyishan

研究武夷山市五夫镇白莲荷塘底泥中7种重金属(Hg、As、Cd、Pb、Cr、Cu和Zn)的全量和形态分布,运用风险评价编码(RAC)法及次生相与原生相分布比值(RSP)法评价元素生物有效性、判断元素的主要来源,并利用相关系数分析重金属形态受土壤理化性质的影响。结果表明:部分荷塘底泥样品的Hg、Cd全量超出NY/T5010—2016《无公害农产品种植业产地环境条件》的标准限值,且均值分别为福建省土壤背景值的3.09、5.37倍,富集较为严重。其中,Hg的残渣态占总量的80.79%,RAC值和RSP值较小,生物有效性较低且以自然来源为主;Cd以离子交换态、碳酸盐态和残渣态三种形态为主,RAC值和RSP值最大,生物有效性最高且受人为污染最为严重;Pb和Cu以残渣态为优势形态,但RAC值和RSP值较大,一定程度受人为来源的影响;As、Cr和Zn以残渣态为主,基本为自然来源。研究区荷塘底泥重金属形态分布在不同程度上受土壤基本理化指标(有机质和p H值)的影响。本研究可为合理地防治武夷山土壤重金属污染提供科学依据。

The total concentrations and chemical speciation of seven heavy metals（Hg, As, Cd, Pb, Cr, Cu and Zn） in the sediment samples from the lotus ponds in Wufu Town, Wuyishan were analyzed, the bioavailability and main source was evaluated by means of risk assessment code（RAC） and the ratio of secondary phase and primary phase（RSP）, and the effects of soil physical and chemical properties on heavy metal chemical speciation were studied by the analysis of correlation coefficient. The results showed that the total contents of Hg and Cd in some sediment samples of the lotus ponds exceeded the standard limit for n Y/T 5010—2016 Environmental Conditions for Non-Pollution Agricultural Products Production Area. The average contents of Hg and Cd was 3.09 and 5.37 times higher than that of the respective reference values for Fujian standards on these elements, respectively. With low value of RAC and RSP, Hg in residual fraction accounted for 80.79% of the total content, which presented tiny bioavailability and mainly came from natural source. Cd, with the greatest bioavailability and the highest value of RAC and RSP, existed mainly in forms of exchange, carbonate and residual fractions, and was greatly polluted by agriculture activities. With higher value of RAC and RSP, the predominant existing speciation of Pb and Cu were residual fractions, and were subjected to a certain extent by human source influence. However, the main origin of As, Cr and Zn which mainly existed as residual fractions was natural source. The different effect of soil physical and chemical properties（organic matter and the value of pH） on heavy metal chemical speciation existed. it might provide a scientific basis for the prevention and management of heavy metal pollution of soil in Wuyishan.