Strategies of sample preparation for selected trace metal speciation and determination of pesticides in environmental samples

Abstract: Soil is an environmental constituent of the earth that performs a collection of essential purposes in our humanity such as food production. With fast industrial development and growth that have happened in most areas of the world during the recent years, the soil section is getting a large amount of persistent pollutants from different sources. These include trace metals and pesticides. An immense number in the scientific literature have been documented on the concentrations of trace metals and pesticides in soil. Contamination caused by agricultural activities such as pesticides and fertilisers is the main source of low soil and groundwater quality in many countries. Ineffective administering of agricultural processes can lead to contamination of soil and groundwater by nutrients and pesticides. For this reason, there is a need for the development of simple analytical techniques for motoring of these pollutants. Therefore, the main objective of the study was to develop sample preparation methods for the fractionation of trace elements and extraction of pesticides from environmental samples collected from different areas in Bloemfontein in the Free State. An ultrasound assisted sequential extraction procedure derived from a three-step Bureau Community of Reference (BCR) method was applied for fractionation of elements in three agricultural soil samples collected in geographical areas surrounding specifically Glen Agricultural College outside Bloemfontein (Free state Province, South Africa). The results obtained demonstrated that Mn, Co, Tl and Cd (except Soil 1) were found to have the highest percentage in the easily reducible fraction compared to other elements. Cu, Zn, Mo, Pb and Cd (in Soil 1) were dominant in the oxidizable fraction. Furthermore, the highest concentration of most metals such as Fe, Ni, V, Cr, Sb, Pb and As were obtained in the residual fraction of the soil samples. The environmental risks and degree of contamination were assessed using risk assessment code (RAC), individual contamination factors (ICF) and global contamination factor (GCF). According to risk assessment code (RAC) values, the soil samples demonstrated that Mn, Co, Ni, Zn, Mo and Cd pose a medium risk to the environment while Tl and Cd showed to high risk. In addition, individual contamination factors (ICF) were computed for each element and the highest ICF values (>10) were obtained for Cd and Mo. The global contamination factor (GCF) demonstrated that Soil 2 and 3 present the highest environmental risk compared to Soil 1...M.Sc. (Chemistry