SPATIAL VARIABILITY AND GEOSTATISTICAL ANALYSIS OF HEAVY METALS IN THE MINING AREAS OF BAGEGA, ZAMFARA STATE, NIGERIA.

Salisu, K., Ahmed, M.* and Yakubu, I.B.

Heavy metal occur naturally, its uses have led to wide distribution in the environment rising concerns over their potential effect on human health. Analysing the spatial distribution of heavy metal in Bagega, Zamfara State is necessary because of the recent outbreak poisoning that impacted mostly women and children due to illegal mining activities; the analysis will help the planners especially the health sector for identification of clustering and or “hot spots”. Spatial variability of heavy metals (Pb, Cr, Mn, Cd, Ni) from the soil depth of 0-15cm in Bagega, Zamfara State was geostatistically examined, employing GIS technique. The results of semivariogram analysis of Cr, Mn and Ni exhibited strongly spatial autocorrelations. This was controlled by intrinsic factors of parent material, relief and soil type. Pb and Cr were greatly affected by extrinsic factors of mining or anthropogenic activities. Kriging method was also employed to estimate the unobserved points and their spatial distribution. Resultant maps indicate the clustering of Cr and Cd in the farmland areas, and Pb and Ni clustered at the central part of the area while Mn concentrated at the southwestern part. The trends of variability among the heavy metals in the study area indicate that Ni varies more than any other element in the area followed by Cd and Cr. The study recommends further studies on mapping the concentration of heavy metals using more soil depth to adequately compare the level of concentration of the heavy metals across the soil profile. Also, studies should be conducted on mapping areas that are vulnerable to pollution using fuzzy models.

Key words: Geostatistics, GIS, Heavy Metals, Kriging, Spatial Variation.