Geochemical Background of Some Potentially Toxic and Essential Trace Elements in Soils at the Nadowli District of the Upper West Region of Ghana

Use of universal baseline values, such as continental crustal averages, to assess health issues from trace elements in environmental soils may be fraught with challenges because the method only considers unmineralized rocks and soils in the determination of average crustal abundances or background values. Legislated guideline values are also for specific geographic locations in the environments. None of these take into account the human activities at a particular local community as the environmental conditions have dire influence on trace element mobility, concentrations, and storage in the surface soils.
Aim: The aim of this article therefore is to evaluate site-specific geochemical background concentrations of some potentially toxic trace elements in the artisanal mine area and farmland soils of Nadowli District.
The method involved collection of 29 samples of trace element from soils up to the depth of 20 cm. These samples were analyzed using inductively coupled plasma-mass spectrometry (ICP-MS) analytical technique.
The results of the trace element concentrations were statistically and graphically analyzed to isolate sets of background values that are better suited locally to identify and assess areas contaminated and depleted by trace elements. Local background values of 15.00 ppm was estimated for arsenic (As), 0.02 ppm for cadmium (Cd), 0.01 ppm for mercury (Hg), 35.0 ppm for zinc (Zn), 20.0 ppm for copper (Cu), and 0.40 ppm for selenium (Se). The study found that estimated local backgrounds for essential elements were in the range of the legislated guideline values and should be used to assess the environmental quality and health as well as develop environmental policies for environmental monitoring. The potentially toxic elements contrastingly have higher local background values for As and Cd and lower local background for Hg when compared with the legislated soil guideline values.
In conclusion, for cleanup goals in environmental legislation and for the assessment of the impacts of trace elements on health in Nadowli District, these background values should be used.