Bioaccumulation, Growth and Photosynthetic Response of a New Found in Bulgaria Invasive Species Lemna minuta and L. valdiviana to Heavy Metal Pollution

ABSTRACT: Heavy metals can meet in the surrounding environment as natural ingredients or from agricultural, industrial and chemical industries. The study was conducted in order to trace the potential of the aquatic plant L. minuta and L. valdiviana for the bioaccumulation of Cu, Cd, and Pb from contaminated water at low levels of these elements. Each of the duckweed species was treated separately with CuSO4.5H2O, CdSO4, Pb SO4 (Valerus, Bulgaria) at 0.5 and 1 mg L-1 concentrations of for 96 hours. After conducting the experiments, relative growth rate (RGR), bioconcentration factor (BCF), tolerant index (Ti) and photosynthetic pigments of two Lemna species were studied. The solution with higher metal concentration more inhibits the growth of macrophytes. The BCF of the metals on the two species were in decreasing order: Cu > Pb > Cd. Our study showed that L. minuta and L. valdiviana at a concentration of 0.5 mg L-1 copper have better affected on the photosynthetic apparatus compared to the control. Better bioaccumulation ability was established in L. minuta compared to L. valdiviana.

摘要：重金属可作为天然组分存在于周边环境中，亦可源自农业、工业及化工行业。本研究旨在探究水生植物细叶浮萍（L. minuta）与瓦尔迪维亚浮萍（L. valdiviana）在低浓度重金属污染水体中对铜（Copper, Cu）、镉（Cadmium, Cd）及铅（Lead, Pb）的生物富集潜力。实验分别以浓度为0.5与1 mg·L⁻¹的硫酸铜（CuSO₄·5H₂O）、硫酸镉（CdSO₄）及硫酸铅（PbSO₄，购自保加利亚Valerus公司）对两种浮萍进行为期96小时的单独胁迫处理。试验结束后，对两种浮萍的相对生长速率（relative growth rate, RGR）、生物富集因子（bioconcentration factor, BCF）、耐受指数（tolerance index, TI）及光合色素含量展开测定与分析。金属浓度更高的培养液对大型水生植物的生长抑制作用更强。两种浮萍对三种重金属的生物富集因子均呈现如下递减顺序：Cu＞Pb＞Cd。本研究表明，在0.5 mg·L⁻¹铜浓度处理下，细叶浮萍与瓦尔迪维亚浮萍的光合机构表现相较于对照组更优。本研究证实细叶浮萍的生物富集能力优于瓦尔迪维亚浮萍。