南四湖菹草对上覆水和表层沉积物中汞和砷的富集特征

Enrichment characteristics of mercury and arsenic by Potamogeton crispus in the overlying water and surface sediment of Nansi Lake

为了解南四湖菹草对水体中汞(Hg)和砷(As)的富集能力,于2019年4月在南四湖采集了49个采样点的上覆水、菹草、表层沉积物样品,测定了样品中Hg和As的含量,并采用生物富集系数法(BCF)评价了菹草茎、叶和果实对上覆水和表层沉积物中Hg和As的富集能力.结果表明,南四湖上覆水中Hg的超标率为34.7%,As浓度达到Ⅲ类水标准;表层沉积物Hg和As的平均含量分别为南四湖底泥背景值的6.23倍和2.44倍;菹草中Hg和As平均含量分别为0.14 mg∙kg^(−1)和3.02 mg∙kg^(−1);Hg在叶中的含量分别是茎和果实的1.22倍和1.56倍;As在茎中的含量分别是叶和果实的1.22倍和1.47倍.上覆水、菹草和表层沉积物中的Hg、As含量的空间分布差异均较大,且出现局部的高值区.菹草各器官对Hg的富集能力表现为叶>茎>果实,对As富集能力为茎>叶>果实.菹草对上覆水和表层沉积物中Hg、As富集系数均为高度变异,空间分布差异较大,且与上覆水和表层沉积物中Hg、As含量具有相关关系,说明Hg和As在菹草-上覆水-沉积物系统中具有一定的动态迁移能力.

In order to understand the enrichment abilities of mercury(Hg)and arsenic(As)by Potamogeton crispus(P.crispus)in Nansi Lake,P.crispus,overlying water and surface sediment samples were synchronously collected in 49 sampling sites around the Nansi Lake in April,2019.The total content of Hg and As in all the samples and in organs of P.crispus were analyzed,and the bioconcentration factors(BCFs)were calculated to assess the enrichment abilities of Hg and As by the whole plant and organs of P.crispus during its growing period.The results showed that Hg concentrations in 34.7%sampling sites exceeded the typeⅢstandard value of the GB3838—2002 National Environment Quality Standards for Surface Water,while As concentrations were all lower than its corresponding typeⅢstandard value.The average content of Hg and As in the surface sediment were 6.23 times and 2.44 times of the sediment background values of Nansi Lake,respectively.The average content of Hg and As in P.crispus were 0.14 mg∙kg^(−1) and 3.02 mg·kg^(−1),respectively.The average Hg content in leaves was severally 1.22 times and 1.56 times of those in stems and fruits,while the average As content in stems was 1.22 times and 1.47 times of those in leaves and fruits respectively.The spatial distribution of Hg and As content in overlying water,P.crispus and surface sediments differed greatly,and the high values of Hg and As occurred in different areas of the lake.The enrichment abilities of Hg in different organs of P.crispus were in the order of leaf>stem>fruit,while for As it was stem>leaf>fruit.The BCFs of Hg and As in overlying water and surface sediments by P.crispus were highly variable,and their spatial distribution was quite different.Moreover,the BCFs had some significant correlations with their corresponding content of Hg and As in overlying water and surface sediment,which suggested that Hg and As might have certain dynamic migration abilities in P.crispus,overlying water and sediment system.