Validation of microwave-assisted digestion and Inductive coupled plasma -mass spectrometer for the determination of trace metals in the soil around Darvill sludgeland and their environmental complications

This study presents the optimization, validation, and application of microwave-assisted digestion and inductively coupled plasma mass spectrometry (ICP-MS) for the simultaneous determination of trace metals (B, Cd, Co, Cr, Cu, Mo, Ni, Pb, Se, V, Zn, and As) in soils from sludgeland. This analytical method was validated according to the requirements of ISO standards for new methods, which include parameters such as linearity, sensitivity and range, accuracy, precision, selectivity, the limit of detection (LOD), the limit of quantification (LOQ), and recoveries. The method demonstrated good linearity with a correlation coefficient greater than 0.999 for all 12 metals of interest. The limit of detection (LOD) was found to be between 0.001 and 0.006 mu g/L and the Limit of Quantification (LOQ) was between 5 and 200 mu g/L. The method was then applied to soil samples from 28 sites where sludge is disposed to assess the presence of trace metals and their concentrations were compared with background concentrations of metals in South Africa. The Cr with the value ranging from 83.5 mg/kg to 480 mg/kg exceeded the limits in all sites while Zn, Co, Ni, As exceeded in some sites. Geo accumulation was then used to categorize the contamination level of soil by trace metals and observed to be strongly contaminated by Zn with values between 1.2 and 3.5 while moderately contaminated by Pb, Ni, Cu, and As with values between 1.3 and 2.7 which poses their environmental risk.