"Comparative Study on Bioaccumulation of Lead (Pb) in Some Birds and Plant Species in Rapidly Degrading Mining Sites in Three Selected Local Government Areas of Nasarawa State, Central Nigeria"

Abstract

Heavy metals are an integral part of nature and play an important role in the lives of living species at trace levels. These become toxic when in excess in the organisms. Therefore, this study investigated the bioaccumulation of lead (Pb) in some birds and plant species in rapidly degrading mining sites in three selected Local Government Areas (LGAs) of Nasarawa State, Central Nigeria, from June 2017 to May 2018. Birds were trapped using mist nets. Ninety (90) tail feathers of birds and forty-eight (48) tree stand leaf samples were collected for quantitative measurements of Pb using the Atomic Absorption Spectrophotometer (AAS). A total of ninety (90) individual birds belonging to thirty five (35) species were trapped. Eighty-nine percent (89%) of the species were passerines while non-passerines were only 11%. The non-passerines accumulated more Pb than the passerines; however, there was no significant variation (t = 2.2312, df = 9.7714, P = 0.05034) between bird groups. Bird species-specific Pb bioaccumulation was highest in Shikra (3.24 ppm). The carnivorous birds had the highest Pb concentration, yet there was no significant difference (P > 0.05) in relation to the other feeding guilds. Pb concentration was not significant (P > 0.05) between birds' age groups and sexes, respectively. The respective differences in mean Pb concentration in bird feathers as well as plant leaves across the surveyed sites significantly varied (P < 0.05). Ficus plant Pb concentration was highest over the other three plant species, although not significant (P > 0.05). The association in bioaccumulation of Pb between plants and birds was negative (t = -1.4223, df = 88, P = 0.1585, r = -0.15). The pooled average Pb bioaccumulation in birds as well as plants, respectively, was negligibly below the World Health Organization threshold (maximum permissible limit), which would have had an adverse effect. In conclusion, in the long term, Pb bioaccumulation might have more severe consequences for non-migratory species from the checklist of birds recorded in this study that carry out their entire life functions within a confined area. Thus, there is an urgent need for continuous bio-monitoring using this non-invasive technique, which will aid regulatory agencies in collaborating with miners and local communities to explore safer mining practices in order to conserve biodiversity in light of the detrimental effects of Pb bioaccumulation.