Monitoring regional gradients in atmospheric heavy metal pollution: A comparative application of top-soil,epiphytic moss and plant litter as indicators

Heavy metal levels in top-soils, plant litter and mosses from uninhabited areas of southwest Nigeria were used to examine the gradients of metal contamination levels in the area. Correlations of metal levels between the different materials were poor. However, the highest levels of some of the metals were obtained in all the indicator materials within the higher pollution zones. Thus, the materials were all suitable for discerning the pollution zones.Higher levels of most metals were accumulated in mosses than in soil or litter within the lower and higher pollution zones. The extents of accumulation in the higher pollution zone relative to the lower pollution zone showed that the moss was not necessarily more effective in indicating the gradients in metal levels than the top-soil and plant litter.