Spatial and seasonal variations in lead content of plants colonizing the Bo Ngam lead mine, Thailand

Abstract

Seasonal and spatial variations in lead concentrations in soil and plants and lead-tolerant plant species diversity were studied in a closed open-pit Bo Ngam lead mine area. Two different sampling sites at the open pit mine area, the pond site and land site, were observed. Lead content in soil and plants was seasonally dependent. The lowest lead concentrations in soils were found in July during the wet season (0.6%) and highest in October during the dry season (> 11%). Most plants had the highest lead content during the wet season (May to September) and the lowest during the dry season (October to April). Most plants examined were perennials (16 species) with some annuals (6 species). Twelve species were common to both sampling sites. There were a total of 17 plant species that had lead accumulation in shoots > 1 g/kg, though only six species (Ageratum conyzoides, Buddleja asiatica, Chromolaena odoratum, Conyza sumatrensis, Mimosa pudica, and Sonchus arvensis) showed a translocation factor > 1. These plant species have a high potential for remediating the lead mine area.