The enrichment factors (EF) of metals are shown in Fig. 1. EF has been adopted to show the anthropogenic influence of metals in soil,sediment and atmosphere [29]. The EF values of compost provide useful information on contamination status of finished compost and its suitability for bioremediation and agricultural use.
The compost revealed low EF values less than 2.0 for all the analyzed metals indicating low metal contamination and depletion to minimal enrichment [48]. The metals (Mn, Fe, Zn, Cu and Cr) observed in this study are essential micronutrients required by plants for growth. The contaminated soil samples were enriched in Cu and Zn (EF > 5.0) indicating metal pollution by anthropogenic activities [29]. Cu and Zn enrichment could be attributed to industrial and traffic pollution [49]. Emission sources of Cu and Zn have also been linked to sinter plants, blast furnaces, basic oxygen furnaces, electric arc furnaces, secondary copper production, cop-per/zinc alloys, primary lead/zinc production and glass production[49,50]. Although Cu and Zn are essential micronutrients for plants growth and root development, their high EF values may suggest soil contamination. Excess of Zn and Cu in soil may cause a reduced/halt growth in plant, root death and chlorosis [51]. Zn can also inhibit the uptake of Fe and Mn by plants in soil [52].