Bio-transfer and bioaccumulation patterns of heavy metals in mine site-inhabiting ants and grasshoppers, across mine site restoration chronosequence.

Abstract

Soil is known to serve as a significant sink for heavy metals in coal mine sites, thus also influence the plant and other organisms of that area. Hence, the presence of heavy metals in coal mine soil is of concern to land managers. Insects occupy different trophic positions in the food chains, thus many insect species accumulate large amounts of heavy metals in their bodies and this is a matter of concern. In the present study, we investigated biotransfer and bioaccumulation of heavy metals from soil, grass species Cynodon dactylon, Vetiveria zizanioides, grasshopper species Gastrimargus africanus, Choroedocus robustus, ant species Cataglyphis longipedem and Camponotus compressus in six different ages (2, 4, 6, 8, 10 and 12 year old) of coal mine sites. Our study revealed that at some extent the heavy metal content and BAF patterns of heavy metals along different pathways (from soil to grass, soil to grasshoppers and from grass to grasshoppers) were not consistent and did not reflect the soil pollution status for all the metals, related to the mine spoil dump age. However, in contrast, ants successfully reflected a consistent pattern in the bioaccumulation of heavy metals via soil, thereby indicating the pollution status of the soil along with the restoration age of mine spoil dumps. Our study showed that ant species can successfully forecast the presence of heavy metals of coal mine spoils along with their restoration.