Distribution of Cd and Pb Accumulated in Medicinal Plant Roots and Their Cultivation Soils

Abstract

In general, plant roots accumulate more heavy metals than the above ground organs such as leaf, stem, and fruit. This implies that root medicinal plants would be an issue with excessive heavy metal accumulation. Therefore, the current study was carried out to investigate the distribution of heavy metal (focused on Cd and Pb) concentrations in soils and medicinal plant roots grown in different region of Korea. Total 293 samples for each soil and plant were collected along the national wide. Soil pH, total and phytoavailable metal concentrations (1 M NH4NO3 extracted) in soils were determined and heavy metal concentrations in root of the medicinal plants were analyzed. Heavy metal concentrations of the soil samples studied were not exceeded standard limits legislated in ‘Soil Environmental Conservation Act’, except 2 samples for Cu. However, substantial amount of Cd was accumulated in medicinal plant roots with 29% samples exceeding the standard limit legislated in ‘Pharmaceutical Affairs Act’ while all plant samples were lower than the standard limit value for Pb. Also the current study demonstrated that cadmium concentrations in the roots were governed by the phytoavailable Cd in soils, which decreased as soil pH increased. From this result, application of heavy metal immobilization technique using a pH change-induced immobilizing agents can be suggested for safer root medicinal plant production.