Accumulation of Heavy Metals by Japanese Weeds and Their Seasonal Movement

Abstract

Phytoremediation is a technique for the removal of contaminants in the environment using plants, which is currently is being researched worldwide. We focus attention on certain Japanese weeds, which have a large biomass and high environmental adaptability as a hyperaccumulator. Specifically, we investigated the seasonal metals movement of roots, stems and leaves on Artemisia princeps, a common Japanese weeds, and examined methods of heavy metal removal from the soil. Plants and surface soils were collected at watersides such as a reservoir and adjustment pond around our University at Nara Prefecture, and around the Kizu river of Seika town at Kyoto Prefecture in Japan. The soils and plants were ashed using H₂NO₃, HCl, and H₂O₂. Mn, Ni, Cr, Fe, Cu, Zn and Li in the ashes were measured by AAS. Hyperaccumulators have not been found yet at our investigation sites. However, Aster leiophyllus, Artemisia princeps and Stenactis annuus accumulated 2 or 3 times as many metals (Cr, Cu, Mn) as other plants in the same s ites. As to the seasonal metals movement of roots, stems and leaves on Artemisia princeps, plants concentration and accumulation ratio of Cu that compared the concentration between soil and plants are high in autumn. As a result, we think that Cu plays special role different from other metals. Accordingly, this movement is important in examination of the treatment stage after having taken in heavy metal.