Distribution and mobility of arsenic species in solids and leachate composts

Because arsenic can exist in toxic and non-toxic forms, it is important to identify them in compost. This organic material prepared from urban and agricultural wastes, is often used for recovering or remedying soils. As a matter of fact, it’s important to control the mobility of arsenic and its different forms present in leachate composts.  In this work total arsenic was determined in compost samples, previously submitted to acid digestion using Inductively Coupled Plasma Mass Spectroscopy (ICP–MS). Total inorganic arsenic and As (III) results were compared with those directly determined in solids samples by Square Wave Voltammetry (SWV). It was found that two thirds of arsenic present in solids are in inorganic forms. As (III) is a minor component in the solid, detectable only in agricultural composts. In  leachates, the inorganic arsenic was mobilized in his majority as As (III).