Geochemical characterization of soils, sediments and waters around active and abandoned dumpsites in Lagos.

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Abimbola, A.F
Odukoya, A.M
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Chinese Journal of Geochemistry
In developing countries, large amounts of wastes are dumped daily in open dumping sites without proper management. This practice usually causes enhanced concentration of metallic ions in environmental media within and beyond the vicinity of such dumps with attendant adverse environmental and health risks. Hence the aim of this study is to assess and elucidate the physico- and metallic ions concentrations in three environmental media (soils, sediments and waters) around active (Ojota) and abandoned (Isolo) dumpsites in Lagos and also to do a comparative study with reference to possible environmental and health impacts. A total of eighty samples comprising water, sediments and topsoils were collected around the two dumpsites. The soil and sediment were dried, disaggregated and sieved to <75 ~tm fraction for analysis of the metallic ions using aqua-regia digestion technique and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The analysis of metallic ions and cations in water was carded out using Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) while unacidified water samples were analyzed for anions concentrations using the DIONEX DX-120 Ion Chromatography techniques. Analytical results show that pH, NO3, Fe, Mn and Na in most of the water samples are above WHO and EPA standards. Also there are relatively strong correlations between NO3 and C1, SO4, Coliform, TDS and EC which are an indicator of water contamination especially in the direction of groundwater flow. The mean values of the significant metallic ions present in the water samples include Cu (16.29 and 38.0), Zn (535.71 and 667.0), A1 (0.27 and 0.19), Ba (42.86 and 55.0), Sr (80.0 and 136.0) and B (118.7 and 160.2) for active (Ojota) and abandoned (Isolo) dumpsites respectively. Soil samples revealed varied concentrations with the estimated average contamination factors of 3.86 and 5.71 (As), 1.60 and 1.93 (Mo), 3.41 and 4.24 (Zn), 0.93 and 2.23 (Cu), 7.71 and 12.64 (Pb), 8.71 and 9.21(Cd) for both active and abandoned sites respectively. All these metals with Ag are also significant and follow the same trend in the sediments. Ag, Bi, Sb, Ga, Sc, M_n, Ga and La in soil samples are only significant for samples close to the dumpsites while Bi, Be, Sb, Co, Cu, La and Cr are significant for sediments taken downstream. Most of the metallic ions show significant enrichment in both soil and sediments while A1, B, Ba and Sr are only significant in water. These may be attributed to the adsorption characteristics of the soil and sediments, and relatively high mobility and solubility of the metals in water, respectively. The overall contamination degrees for both active and abandoned dumpsites are 23 and 34 for water, 40 and 30 for soil, 62 and 25 for sediments, respectively, which indicate a very high degree of contamination and a considerable degree of contamination, respectively. It can be concluded that samples around the abandoned dumpsite show higher level of contamination than those of active dumpsite. This may be the result of total decomposition and chemical reactions of wastes within the abandoned dumpsite as a result of its abandonment for a long time without any treatment measure, thus resulting in leachates plume that migrated from the dumpsite to the soil, surface water, sediments and eventually to the groundwater within and beyond the vicinity of the dnmpsite.
waste , metallic ion , water , soil , sediment
Abimbola, A. F., & Odukoya, A. M. (2006). Geochemical characterization of soils, sediments and waters around active and abandoned dumpsites in Lagos. Chinese Journal of Geochemistry, 25, 131-132.