II) Wood pellets for home heating can be considered environmentally friendly fuels? Heavy metals determination by inductively coupled plasma-optical emission spectrometry (ICP-OES) in their ashes and the health risk assessment for the operators

The aim of the present study was to determine the concentrations of twelve potentially hazardous elements in wood pellet ashes obtained by the combustion of 13 pellet brands for sale in Italy, the impact of adding the ashes to soils and health risk of operator due to dust exposure. Samples were analysed by Inductively Coupled Plasma Optical Emission Spectrometry. The concentrations of heavy metals in ashes from stoves ranged from 0.41 to 7.2 mg kg-1 for As, from 1.3 to 12 mg kg-1 for Sb, from 1.8 to 12 mg kg-1 for Zn, from 0.23 to 0.8 mg kg-1 for Pb, from 0.18 to 2.8 mg kg-1 for Ni, from 0.09 to 1.0 mg kg-1 for Cd, from 0.46 to 3.4 mg kg-1 for Cr, from 0.94 to 2.7 mg kg-1 for V, from 2.2 to 11 mg kg-1 for Cu, from 60 to 409 mg kg-1 for Mn, from 83 to 432 mg kg-1 for Fe and from 3484 to 15,484 mg kg-1 for Al. The total concentrations for the 12 investigated elements, expressed as the sum of the concentrations (∑me), ranged from 3703 mg kg-1 to 15,946 mg kg-1 of dry weight with a mean of 8455 mg kg-1. Considering all the metals, the results indicate that there are very low risks for operators regarding non-carcinogenic and carcinogenic elements contained in the wood pellet ashes produced during cleaning of pellet stoves in confined environments.