Leaching of heavy metals from brick clay and sewage sludge ash, measured with ICP-OES and ICP-MS

The concentrations of Cd, Cr, Cu, Ni, and Pb were measured by inductively coupled plasma atomic emission spectroscopy (ICP-OES; type Varian 720-ES ), after the material was first digested by Microwave Assisted Acid Digestion, using 0.5 g and 10 mL of concentrated nitric acid, according to the American Standard EPA 3051A. The content of Cl and SO4 was measured in a suspension with 10 g of sample and 25 mL of distilled water after 24 h of agitation, using ion chromatography (IC). The leaching of heavy metals was found by the leaching test, DS/EN 12457-2:2002, where 10 g of material and 100 mL of distilled water (L/S 10) were agitated for 24 h. The content of heavy metals in the leachate was measured with inductively coupled plasma mass spectrometry (ICP-MS). The leaching results were compared with the limiting level described in the Dutch Soil Quality Decree, 2015. All these analyses were made in triplicate.