Levels of Cobalt in Some Tree Barks and Soils from Yobe State Nigeria

Abstract

Two different species of trees (Ficus thoningi, and Adansonia digitata) from Yobe State, north east, Nigeria were used in the investigations. The barks and the soils around these trees were analysed for their cobalt concentrations using atomic absorption spectrophotometry. The results of the analysis indicate various concentration levels obtained from soil solution through mineral uptake by plants. The mean values of Co range between 0.44 - 3.01µgg^-1 in the bark and 0.26 - 2.68µgg^-1 in the soil. All the values obtained correlate well with the anthropogenic activities in the study area and are below the recommended safe limits for heavy metals by WHO, FAO, EU, and NESREA guidelines. However, there is need for constant monitoring since the inhabitants depends on some of these plants for their primary health care.  The statistical comparison of the values between the bark and soil shows correlation at P < 0.01 and significant difference at P < 0.05. The study further demonstrates the suitability of some of the trees as a good bioindicator.

Keywords: Cobalt, Tree back, Soil, Yobe State.