Spatial distribution of zinc, lead and cadmium in snails, leaves and soils from diverse sites

Abstract

The potentials of snails, leaves and soils to act as indicators for mapping environmental concentrations of toxic heavy metals was assessed in diverse sites in Benin metropolis, Nigeria.  Steady state metal concentrations (Zn, Pb and Cd) were measured in the snail (Limicolaria aurora), plant leaf (Zanchezia nobilis) and soil samples from rural and urban sites. Each replicate snail was partitioned into two soft tissues (kidney and entire rest) and their Zn, Pb and Cd levels compared with those of soil and leaves of a food plant Zanchezia nobilis.

     In all sites, the concentrations of all metals were highest in the pooled snail fractions in an increasing order of snail > soil > leaf. Metal concentrations also showed rural-urban differential, being higher in the urban sites in all matrices. Zinc, which is an essential metal, had the highest concentration in all the matrices. Monthly variations were species and metal specific. Mean metals concentrations in snail tissue fractions correlated with soil levels. Thus, the use of snail (L. aurora) as a sentinel for the quantification of metal contamination is further recommended in mapping environmental metal pollution inNigeria.