北部湾盐沼茳芏盐沼湿地土壤-植物系统重金属污染评价

Assessment of Heavy Mental Contamination in the Soil-plant System of Cyperus malaccensis Salt Marsh Wetland in Beibu Gulf

滨海湿地是典型的环境脆弱带和敏感带,重金属污染是其中受关注度较高的一方面。为全面了解北部湾滨海盐沼的重金属污染水平,以北部湾典型滨海盐沼植被茳芏(Cyperus malaccensis)所在的南流江入海口和茅尾海钦江入海口湿地为研究对象,通过对植物和对应土壤进行采样分析,测定该区土壤及植物中重金属元素(Cu、Zn、Cr、Pb、Cd和Hg)的含量,并评价不同潮滩位置(内滩、中滩和外滩)重金属的污染程度及其在土壤-植物系统中的富集特性。结果表明,两区域盐沼湿地土壤综合污染程度处于低污染状态,南流江口Zn的含量(283.59±132.50)mg·kg^(-1)接近中度污染,其次是Cd(0.10±0.03)mg·kg^(-1)和Hg(0.11±0.05)mg·kg^(-1),而其他重金属元素含量未超标;茅尾海受Zn轻度污染,其次是Cu和Hg,Cr、Pb和Cd未达到污染水平。受海洋动力和河流径流混合动力作用,两区域各滩面盐沼土壤重金属分布规律存在差异,南流江口3个滩面重金属的含量表现为:内滩>中滩>外滩,茅尾海口则表现为:中滩>外滩>内滩。两区域盐沼茳芏富集特征表明:茅尾海盐沼茳芏对Cd(BCF=1.66)和Hg(BCF=0.89)具有较强的富集作用,而南流江口盐沼茳芏仅对Cd(BCF=1.93)具有较强的富集作用,其余重金属Cu、Zn、Cr、Pb未在茳芏体内显著富集,因而茳芏可作为富集Cd、Hg的天然盐沼植物。进一步研究发现,两区域茳芏地下茎对重金属的富集能力远大于地上茎,富集能力因重金属种类及积累部位的不同而表现出一定的差异性和选择性。该研究可为滨海盐沼湿地生态修复和保护提供重要依据。

To comprehensively understand the environmental quality of the coastal waters of the Beibu Gulf, the soils of the NanliuRiver estuary and Maoweihai Bay wetland were selected as the research object. The field sampling of the plant and thecorresponding soil was investigated. And the concentrations of heavy metals （Cu, Zn, Cr, Pb, Cd and Hg） in the soil were selected tostudy the contamination levels of heavy metals in different tidal flats locations （inside beach, middle beach and outside beach） andtheir accumulation in soil-plant system. The results showed that the concentration of Zn in the salt marshes soils was low in the twoareas. The concentrations of Zn in the Nanliu River estuary nearly reached to moderate level of pollution, followed by Cd and Hg,while the other heavy metals did not exceed the standard level. And Maoweihai Bay were slightly polluted by Zn, followed by Cuand Hg, while no pollution of Cr, Pb and Cd. The concentration of heavy metals in the different tidal flats locations was significantlydifferent from that of the oceanic and river runoff, the concentration of heavy metals in Nanliu River estuary was insidebeach〉middle beach〉outside beach, and the concentration of heavy metals in Maoweihai Bay was middle beach〉outsidebeach〉inside beach. The results showed Cyperus malaccensis had strong concentrating-accumulating effects on Cd （BCF=1.66） andHg （BCF=0.89） in Maoweihai Bay, while it had strong effects only for enriching Cd （BCF=1.93） in Nanliu River estuary, and the restof the heavy metals Cu, Zn, Cr, and Pb was not significantly enriched in C. malaccensis. Thus the plant C. malaccensis could be usedfor absorption of Cd and Hg elements in salt marshes. We also found that the enrichment ability of the belowground stems for theheavy metals was much higher than that of aboveground stems, the enrichment effects was different due to the identity of heavymetals and the accumulation ability by different tissue.