2.2. Analysis of physical and chemical parameters of wastes and soil substitutes

The content of dry matter (DM) in wastes and soil substitutes was determined by the gravimetric method by drying samples to constant weight at 105°C. The amount of organic matter (OM) in the samples was determined by measuring of the loss-on-ignition of dry matter at 550^oC. Total ash was assessed by incinerating the respective samples at 815^oC followed by weighting the post-combustion residues.

The content of macronutrients, i.e. Ca, K, Mg, P and Na were assayed by means of X-ray fluorescence method with wavelength dispersion WDXRF (Rigaku ZSX Primus, Inc., Wilmington, USA). The content of trace metals, i.e. Cd, Cr, Cu, Ni, Pb and Zn were determined by inductively coupled plasma atomic emission spectroscopy method (ICP-OES) after sample digestion in aqua regia (Perkin Elmer Optima 5300, Perkin Elmer Inc., Waltham, MA. USA). The total content of sulphur was determined with infrared spectroscopy (IR) using a ELTRA CHS (Eltra GmbH, Haan, Germany) whereas the content of nitrogen by the Kjeldahl method.

The wastes and soil substitutes were assayed for pH and electrical conductivity (EC) were measured by photometric and conductometric methods, respectively in aqueous solutions at the ratio 1:2.5 (w/v). A sum up of selected waste parameters was provided in Table 2.

TABLE 2 Physical and chemical characterization of wastes used for soil substitutes blends