TOXIC ELEMENTS IN SOIL AND SEDIMENT OF THE AWE BRINEFIELD, NORTHCENTRAL NIGERIA: SOURCES, POTENTIAL ENVIRONMENTAL AND HEALTH IMPACT.

Abstract

Soil and sediment in the Awe brinefield were studied in the light of their trace element
content with the view to determining their toxicity levels. Forty samples (33 soil, 7 stream
sediment) were collected and analysed from disturbed and undisturbed areas. Geochemical
data were subjected to analysis using standard pollution assessment indices such as
enrichment factor (EF), geo-accumulation index (Igeo), amongst others. Results showed that
soil of the Awe brinefield has been polluted by elements such as Pb, Cd, As, Zn, Sr amongst
others. EF indicated enrichment of As (154.10) and Zn (125.80), a similar trend was also
revealed by Igeo for these elements. However, variability exists in the levels of
contamination and geoaccumulation of individual trace element investigated. PLI values in
most of the areas sampled indicated heavy metal pollution with PLI greater than one. The
PIAvg results showed the soil around Mahanga area to be of low quality with values ranging
between 0.1-20.4. On the whole, Zn, As and Co portray potential risk elements, as revealed
by ecological risk assessment. High concentrations of As, Pb, Zn and Sr in the soil and
sediment could be due to activities of artisanal miners and partly agricultural chemicals used.
Also, the contributions from the basaltic rocks around the Jangerigeri is also inferred to be
another source. The high concentration or enrichment of these elements which are considered
potentially toxic implies pollution.