Soil Contamination and Food Chain Transfer in Niger State, Nigeria

Abstract

The issue of soil pollution has taken on a rather acute environmental and human health situation in agrarian Nigerian states, especially in states like Niger where agricultural activities constitute the main source of living in the rural areas. The penetration of heavy metals, agrochemical residues, hydrocarbons and other enduring pollutants in the agricultural soils are very dangerous because it will be transferred to food crops and will finally end up in the human food chain. This paper examines the levels of soil pollution, and the food-chain transfer processes in some of the selected agricultural and mining affected communities in Niger state. Priority is given to such contaminants as:  lead (Pb), cadmium (Cd), arsenic (As) and mercury (Hg), chromium (Cr), and zinc (Zn) which are often related to artisanal mining, excessive use of fertilizers, industrial effluents, and random dumping of waste. Based on modern environmental-geochemical methods, the study combines the physicochemical analysis of the soil, crop-uptake analysis, the transfer-factor analysis, exposure-risk analysis to evaluate the magnitudes and the trophic mobility of contamination. The representative samples of soil and crops are analyzed to identify the concentration of heavy-metals and their distribution of accumulation in soil and plants. Geospatial methods are used to map the hot spots of contamination, test the spatial variation and find the communities that are at a significant risk of exposure. The paper also uses human-health risk assessment indices to describe the possible non-carcinogenic and carcinogenic risks that are related to the consumption of contaminated food crops. Recent empirical research in Niger State shows that the soils located near the mining areas and agricultural settings that have high agrochemical application have high levels of heavy-metals. A number of food crops are also highly bio accumulative; especially the leafy vegetables and root tubers; their transfer-factors are higher than the advised safety limits. The consequences of these contamination patterns are deep as they are the decrease in the quality of crops and ecological decay, as well as long-term health hazards among the inhabitants. The study is relevant to the current body of knowledge because it offers a multi-layered evaluation of the processes of soil contamination and food-chain transfer in the Niger State. It highlights the dire necessity of better environmental surveillance, better regulation of agricultural-inputs and community-based public-health based interventions. It recommends the steps that can be used to help in evidence-based policymaking and to encourage sustainable land-use processes to enhance the health of the soil, food safety and human wellbeing in the state of Niger.