Investigation of heavy metal accumulation in Polygonum thunbergii for phytoextraction

Abstract

In this study, cadmium (II), lead (II), copper (II) and zinc (II) were determined in Polygonum thunbergii and soil from the Mankyung River watershed, Korea. Soil samples contained detectable lead (<17.5 μg g−1), copper (<8.4 μg g−1) and zinc (<24.5 μg g−1), whereas cadmium was undetectable. Whole plants of P. thunbergii contained detectable lead (<320.8 μg g−1), copper (<863.2 μg g−1) and zinc (<2427.3 μg g−1), whereas cadmium was detectable only in the stem (<7.4 μg g−1) and root (<10.1 μg g−1). Whole plant concentrations were very different for each metal, particularly in the case of zinc. The mean content of heavy metal in the whole plants increased in the order of cadmium (8.5 μg g−1)<lead (183.3 μg g−1)<copper (548.1 μg g−1)<zinc (1506.7 μg g−1). Soil lead, copper and zinc were correlated with each metal's accumulation in the plants (lead, r=0.841, P<0.005; copper, r=0.874, P<0.001; zinc, r=0.770, P<0.005). Lead content in roots and leaves was highly correlated (r=0.5529, P<0.001), as was lead content in roots and stems (r=0.5425, P<0.001). Mean bioconcentration factors for the aboveground tissues were 4.2 (lead), 14.8 (copper) and 27.7 (zinc), and for the underground tissues, were 22.2 (lead), 92.9 (copper) and 62.7 (zinc). After hydroponic growth, bioaccumulation coefficients were 2.0 (cadmium), 3.2 (lead), 17.2 (copper) and 13.1 (zinc) for whole plants. We considered these results as indicative of the ability of P. thunbergii plants to take up metal ions from a soil matrix contaminated with heavy metals.