土壤重金属在桑树体内的分配及富集特征研究

Study on Distribution and Enrichment Characteristics of Heavy Metals in Soil within Mulberry Trees

摘要: 为了探讨利用桑树作为土壤重金属污染修复树种的可行性，以桂西北某锰矿周边的桑园作为研究样地，采集其土壤、桑树根部、茎部、皮部及叶片样品，用湿法消解—火焰原子吸收光谱法，测定了样品中的Cd、Cr、Cu、Zn、Mn、Pb等6种重金属元素的含量，分析了不同调查样地桑树根部土壤的单因子污染指数、内梅罗综合污染指数及地累积指数。结果表明：1) 调查样地桑园土壤中的Zn为无污染到中度污染，Pb为中度污染到强污染，Mn和Cd均达到重度污染。2) 桑树对重金属具有较强的耐受性，但对不同重金属的吸收、富集和转运能力有一定的差异。3) 在被测的6种重金属元素中，桑树对Cr、Zn、Cu的富集能力相对较强，对Pb、Cd、Mn的富集能力相对较弱；桑树对Cr和Mn的转运能力相对较强，对Pb的转运能力最弱，其吸收的重金属元素主要是累积在根部。因为桑树对锰等重金属复合胁迫具有较强的耐性，同时具有一定的吸收和转运能力，经济效益高，所以，桑树可用于土壤重金属污染的植物修复。

Abstract: In order to explore the feasibility of using mulberry trees as tree species for soil heavy metal pollution remediation, mulberry fields around a manganese mine in northwest Guangxi were used as research site. Samples of soil, mulberry roots, stems, bark, and leaves were collected. The content of six heavy metal elements, including Cd, Cr, Cu, Zn, Mn, Pb, in the samples was determined using wet digestion flame atomic absorption spectroscopy. The single factor pollution index, Nemero comprehensive pollution index, and geo-accumulation index of mulberry root soil in different survey sites were analyzed. The results showed that: 1) Zn in the surveyed mulberry orchard soil ranged from no pollution to moderate pollution, Pb ranged from moderate pollution to strong pollution, and both Mn and Cd reached severe pollution. 2) Mulberry trees have strong tolerance to heavy metals, but there are certain differences in their ability to absorb, enrich, and transport different heavy metals. 3) Among the six tested heavy metal elements, mulberry trees have relatively strong enrichment abilities for Cr, Zn, and Cu, while their enrichment abilities for Pb, Cd, and Mn are relatively weak; Mulberry trees have relatively strong transport capacity for Cr and Mn, while their transport capacity for Pb is the weakest. The heavy metal elements they absorb are mainly accumulated in the roots. Due to the strong tolerance of mulberry trees to combined stress of heavy metals such as manganese, as well as their ability to absorb and transport, and high economic benefits, mulberry trees can be used for phytoremediation of soil heavy metal pollution.