Investigating the Impact of Proximity to Dumpsite on Mercury and Arsenic Levels in Cassava (Manihot esculenta)

Abstract

This study assessed the impact of proximity to dumpsite on mercury and arsenic levels in cassava tubers and peels. A total of eight soil samples and eight plant samples were collected at 10 m and 20 m away from the dumpsite. Two soil and two plant samples each were collected from the east, west, south and north of the dumpsite. The samples were collected from a depth of 0 to 10 cm. Cassava tubers were collected very close to where the soil samples were obtained. The heavy metal in both soil and cassava tuber showed no significant difference (t < 0.05) except with that found on the cassava peel gotten from 20 m away from the dumpsite in both Hg (9.086 mg/kg) and As (0.600 mg/kg). The soil properties showed low to strong association with the heavy metal concentration in the soil and that in the cassava tubers and peels. pH had strong correlation with Hg (r = 0.616) and a weak correlation with the As (r = 0.137) in the cassava tuber. It was found that the BAF of Hg and As in the tuber and peel were all greater than 1. The BTF of cassava tuber of both Hg and As were above 1, which is an indication that there was an effective translocation of these metals to the cassava tuber from the cassava peel. This implies that cassava has the capability of a good bio-accumulator for Hg and As.