“…The characterization of sewage sludge samples is performed using quantitative methods of analysis to determine a limited number of elements, in most cases, only the concentrations of the PTEs that are monitored according to national or European regulations. Their concentrations have been determined using ICP-MS [3], ICP-OES [4,5,12,13], AAS [1,2,14], and WD-XRF [15]. In rarer cases, the content of nutrient elements (P, Ca, Na, K, Mg, and Zn) needed for plant growth are also determined [1,4,5].…”