Physicochemical Characteristics and Heavy Metals Contents in Soils and Cassava Plants from Farmlands within Nnamdi Azikiwe University, Awka, Anambra State

Abstract

Soil samples and cassava tubers collected from farmlands within Nnamdi Azikiwe University, Awka vicinity were analyzed for their heavy metal levels using Atomic Absorption Spectrophotometer (AAS) in order to assess their levels of contamination on the environment as a result of excessive fertilizers and automobile emission. Physiochemical properties of the soil samples were determined using standard methods. The soil pH had a mean value of 6.27 ± 0.07, 6.10 ± 0.06 and 6.57 ± 0.03 respectively indicating that the soils were slightly acidic to neutrality. Total organic carbon and nitrate mean values were 105.20 ± 6.20, 95.75 ± 9.57 and 94.6 ± 2.27 and 138.07 ± 12.09, 149.35 ± 14.25 and 149.20 ± 1.17 respectively showing presence of some organic matters. The mean levels of heavy metals in the soil samples were 0.01 ± 0.01, 0.05 ± 0.03 and 0.05 ± 0.03 for lead (Pb), 0.24 ± 0.16, 0.001 ± 0.001 and 0.001 ± 0.000 for cadmium (Cd) and 0.00 ± 0.00, 0.010 ± 0.006 and 0.001 ± 0.001 for chromium (Cr). These metals levels were in the abundance trend of Pb>Cd> Cr. The mean metal concentrations obtained in the cassava tubers respectively were 0.001 ± 0.001, 0.001 ± 0.001 and 0.005 ± 0.005 for lead (Pb), 0.000 ± 0.000, 0.0003 ± 0.0003 and 0.000 ± 0.000 for cadmium (Cd) and 0.002 ± 0.002, 0.000 ± 0.000 and 0.002 ± 0.002 for chromium (Cr). These metals levels were in the abundance trend of Pb> Cr > Cd. For both the soil and cassava samples, there were no significant variations in the heavy metal concentrations and also in physicochemical parameter except for pH; this showed that there is low heavy metal enrichment in the soils studied. Based on the study, the following heavy metals (Pb, Cd, and Cr) falls within the Codex maximum permissible limits 0.1mg/l or ppm expect soil cadmium in science village which is above the Codex limit. The overall results showed that the farmlands (on soils and cassava tuber) appear to be free from poisoning or some metal enrichment and safe for agricultural purposes and also safe for human health and consumption.