Contamination assessment of toxic elements in the soil within and around two dumpsites in Lagos, Nigeria

Abstract

This study assessed some contamination indices of trace elements in the soil within and around two  dumpsites in Lagos, Southwestern Nigeria. This was with a view to assessing the degree of soil  contamination. Thirty samples were collected from the two dumpsites, dried, disaggregated and sieved to <75um fraction for analysis of trace elements using aqua-regia digestion and Inductively Coupled  Plasma Mass Spectrometry (ICP-MS). The soil generally showed background to minimum enrichment  with arsenic, chromium, molybdenum and background to very high enrichment with cadmium, zinc, lead, Copper and nickel. Scandium, vanadium and strontium were only present in the active dumpsite with minimum enrichment while Lanthanum was present only in the abandoned dumpsite with background enrichment. The geo-accumulation index (Igeo) values for arsenic, chromium, molybdenum, manganese, lanthanum and arsenic, strontium, vanadium for active and abandoned dumpsites respectively were within background concentration. Chromium, scandium, molybdenum, nickel for active site and copper for the abandoned site fell in the class of moderate pollution. Cadmium, lead and zinc ranged between moderate pollution to strong pollution for the abandoned site while copper, cadmium, lead and i zinc fell within strong to extreme pollution for the active site. The grade of ecological risk indices (E ) for  Chromium and Zn indicated low risk and low to moderate risk respectively for both dumpsites. Soil from the active dumpsite showed that arsenic fell within considerable risk, copper (moderate risk), lead and cadmium (very high risk). Soil from the abandoned dumpsite showed low to very high risk with copper, considerable to very high risk with arsenic, moderate to very high risk with lead and very high risk with cadmium. The potential ecological risk (RI) for the abandoned and the active dumpsites ranged between 43.86 to 1567.2 and 133.7 to 732.4 which indicated low to very high risk and very high risk respectively. The results of contamination degrees ranged between low and very high degree of contamination for both dumpsites.

Keywords: Soil, Dumpsites, Trace Elements, Contamination, Lagos