人工湿地系统中梭鱼草和香蒲对镉积累的动态变化

为探讨人工湿地系统中挺水植物梭鱼草(Pontederia cordata)和香蒲(Typha orientalis)对镉(Cd)积累的动态变化,通过在室外表面流人工湿地采样和室内分析相结合的方法,对8-12月梭鱼草和香蒲地上部和地下部的生物量、镉含量及积累量的动态变化进行了分析。结果表明,梭鱼草根部和茎叶镉含量为0.25~0.70mg/kg和0.07~0.18mg/kg,香蒲根部和茎叶镉含量为0.16~0.39mg/kg和0.11~0.17mg/kg,根部镉含量均显著高于各自的茎叶部,两种植物各部位镉含量均在10月达到最大值,两者对镉的富集与转运能力均随着月份的变化而变化,都呈先增高、后降低的趋势;其中,梭鱼草对底泥镉的富集系数为0.76~3.13,香蒲为0.63~0.91,两者的富集系数最高值均出现在10月;两者的转运量系数分别为1.12~10.47、3.25~8.10,最大值分别出现在9月、10月。在10月之前,同一月份梭鱼草地上部的生物量和对湿地中镉积累量均极显著或显著高于香蒲。两种植物地上部分生物量和对湿地中镉积累量均极显著高于地下部分(P<0.01)。综合考虑两种植物的生物量及对镉的积累量,9月和10月分别为梭鱼草和香蒲地上部分最佳收获月份,能够最大化去除湿地系统中的镉。

Cadmium Accumulation in Pontederia cordata and Typha orientalis in a Constructed Wetland

Aquatic plants that can effectively remove heavy metals and other pollutants from water are selected for use in the construction of artificial wetlands. In this study, we investigated the dynamic changes in cadmium accumulation in Pontederia cordata and Typha orientalis in a surface flow constructed wetland. The wetland system used for the investigated has three treatment ponds and the P. cordata and T. orientalis were transplanted into the first treatment pond in May, 2017. The biomass and cadmium accumulation, above and below ground, in the two emergent plant species were analyzed each month from August to December. The study objectives were to provide basic data and a theoretical reference for assessing the cadmium removal capacity of the plants and determine the best time for harvesting plants in the constructed wetland. The cadmium content ranges of P. cordata and T. orientalis roots were 0.25-0.70 mg/kg and 0.16-0.39 mg/kg, while the ranges in stems/leaves were 0.07-0.18mg/kg and 0.11-0.17 mg/kg. The cadmium content of roots was significantly higher than that of the stems/leaves. Although tissue concentrations were lower, the biomass and cadmium accumulation were significantly higher in the stems and leaves of both species (P<0.01). Cadmium removal and accumulation varied by month, increasing initially and then decreasing in both species. Before October, the biomass and cadmium accumulation of the above-ground parts of P. cordata were significantly higher than those of T. orientalis. The maximum cadmium concentration, in both tissue types of both species occurred in October, as did the highest cadmium accumulation coefficients. The cadmium accumulation coefficient ranges were 0.76-3.13 for P. cordata and 0.63-0.91 for T. orientalis, the translocation coefficient ranges were 1.12-10.47 for P. cordata and 3.25-8.10 for T. orientalis, and the maximum values were observed in September and October. In summary, September and October is the best time for harvesting the above-ground parts of P. cordata and T. orientalis, respectively, as it maximizes cadmium removal from the wetland.