Metal tolerant species distribution and richness in and around the metal based industries: Possible candidates for phytoremediation
Plant species growing in and around 38 metal welding workshops in Benin City, Nigeria, were surveyed. Eragrostis tenella occurred most frequently in all the sites, followed by Amaranthus spinosus, Eleusine indica, while Cucurbita pepo occurred least. The family Poaceae, was identified in all the sites visited. The frequency of occurrence of any particular plant species was used as an indicator of tolerance to heavy metals. Margalef index (R1) showed the richest locations in the study to be workshops at Ekenwan Road Quarters with a value of 2.87, followed by those at Ikpoba Hill (2.75). Shannon-Weiner’s diversity index (H) which reveals the location with the most species diversity, showed that Ekenwan Road gave the most diverse with a value of 2.43, followed by Ikpoba Hill (2.17). Wire Road was least diverse in plant species (1.33). Ugbowo quarters had the highest evenness index of 0.96, followed by Sapele Road (0.95), with Wire Road being the location with least evenness (0.82). Cadmium (Cd) and lead (Pb) occurred in soil samples obtained from the sites. Six of the ten locations (Ekenwan, Plymouth, Siluko, Sapele, Sakponba and Ikpoba Hill Road Quarters) had elevated cadmium in soil samples obtained outside the workshops, with the highest concentration of 1.2 mg/kg detected at Ikpoba. Lead concentration was highest at Ugbowo (53 mg/kg). Metal- tolerant plants obtained in the present study are suggested as possible phytoremediating agents.
Key words: Welding workshops, metal tolerant plants, cadmium, lead, phytoremediation.