Determination of metal concentrations in vegetation, soil, dust, and water in the vicinity of a cement factory in North West province, South Africa

Abstract

On a per capita basis, cement is the second most widely consumed product in the world and its demand is increasing globally due to population growth and urbanisation. Manufacturing plants produce cement kiln dust (CKD) as one of the by-products while coal provides the dominant energy source in the manufacturing process. Various meta ls are found in CKD and some of these are micro nutrients with potentially toxic effects. If these are present in large quantities, they pose a direct threat to vegetation, animals and humans. The aim o f this study was to quantify a selected number of trace metal concentrations in vegetation, soil , dust and water samples near a cement manufacturing pl ant in the North West Province. Thirty-one samples at various distances from approximately 500m to 2700m from where the cement factory is situated, were collected. In addition, similar samples (except for water) were taken from a control site situated 72 kilometres in a north-western direction from the factory. The water control sample was collected from the Ditsobotla municipal water supply. Soil. plant and dust samples as well as the sediment from the water sample were acid digested to obtain total metal concentrations . The acid digested samples were analyzed for selected metal concentrations using the ICP-MS. The relationship between soil metal concentrations and particle size distribution as well as the relationship between dust concentrations and Ca concentrations was established to determine the link with the presence on a CMP in the area. The control samples, reference standards and results from similar research performed were used to compare with metal concentrations found in this study. The study revealed that Ni and Cu concentrations are higher in the silt fraction of the soil whilst V, Co, Zn and Pb in the silt fraction are only marginally higher than the complete soil sample. Only Cr and Mn concentrations were higher in soil samples than the control and reference values, while metal concentrations for Cr, Cu, Pb and Mn were higher in the dust samples than the control and the Emission Limit Value (EL V). Moreover, metal concentrations in the vegetation samples are not a concern as the concentrations a re lower than reference values. Cadmium and As levels are of no concern in this study area especially since dust samples had undetectably low levels. The condition of the environment m relation to pollution from the cement factory was established. Although some metals revealed lower concentrations, the study demonstrated the potential of metal contamination particularly Ni, Mn and Cr to the environment vis-a vis on the surrounding vegetation, animals and possibly on humans. It was therefore recommended that ELV limits for South Africa should be established and monitored for cement factories in South Africa coupled with sustainable land management policies.