Levels of heavy metals in Capsicum Annuum and Lycopersicon esculentum cultivated in two farming communities in Obuasi

Vegetables have become an integral part of human’s diet due to their nutritional values thus any form of contamination especially by heavy metals is of great concern. In Ghana agricultural lands are increasingly being used for Mining. As a result, the limited available agricultural lands are now found within or very close to Mining Concessions. In a bid to investigate the levels of heavy metals in vegetables grown in mining areas, the concentrations of six heavy metals (Arsenic, Cadmium, Lead, Copper, Iron and Zinc) in the fruits, shoots and roots of two commonly used vegetables Capsicum annuum (Pepper) and Lycopersicon esculentum (Tomato) in four farms in two farming communities in Obuasi (three farms from Apitikoko and one farm from Kwabenakwa) were determined using Atomic Absorption Spectrometer. All four farms are within 16 km from the Southern Tailings Storage Facility (STF) of Anglogold Ashanti Limited. The levels of the heavy metals in the soils were also determined. The levels of all six heavy metals determined in the fruits of both vegetables in all four farms exceeded the recommended standards. In the shoots and roots the levels of the heavy metals exceeded the recommended standards excepts for Cd in Tomato shoots in Farm 1, Cd in Pepper roots Farm 1 and Zn in Pepper roots in all four farms. Except for As the levels of heavy metals in the soils were below the recommended standards. The highest accumulated heavy metal in the fruits, shoots, roots and soils was Iron whilst the lowest accumulated metal was Cadmium. Farm 4 which is located outside the Anglogold Ashanti concessional area recorded the highest levels of heavy metals for both vegetables and soils than the other three farms which are located within the concessional area. In general the levels of heavy metals in the vegetative organs of the vegetables were higher than that of the reproductive organ; the fruit which is the edible part. In Lycopersicon esculentum heavy metals accumulation was highest in the roots whilst in Capsicum annuum accumulation was highest in the shoot. The levels of heavy metals in Lycopersicon esculentum fruits were higher than those of Capsicum annuum fruits. The general ranking of heavy metals levels in decreasing order in fruits, shoots and roots was Fe>Zn>As>Cu>Pb>Cd. Bioaccumulation ratio indicated that Lycopersicon esculentum plant accumulated more Pb, Fe and Zn whilst Capsicum annuum plant accumulated more As, Cd and Cu. Bioaccumulation ratio above one was recorded for all the heavy metals in both fruits except for As. The farm outside the concessional area tends to be more polluted than farms within the area and closer to the STF. Results indicate that there is a high level of atmospheric transport of heavy metals. It can be concluded that the soils in the two farming communities are polluted with Arsenic and the two vegetables cultivated have high levels of heavy metals, posing a health risk to humans and other livestock that consume them. Thus vegetables and possibly food crops cultivated within and around the Mining areas in Obuasi are unsuitable for human consumption.

Source: KNUST