Heavy metal assessment in vineyard sludge. Copper lixiviation and recovery studies.

The use of copper-based compounds to prevent fungi diseases in vineyards have contributed to heavy metal accumulation in soil, vegetation and waste, causing a serious environmental and agro-industrial problem. One main issue is the waste generated both during and after wine production. This waste must undergo through aerobic/anaerobic digestions, so a safe disposal is possible. As a result, a main final sludge waste is generated, characterized by the presence of significant nutrients for soil fertilization and regeneration, so the return of sludge to vineyard soils would provide a sustainable solution for this waste. However, its hazardous copper (Cu) and zinc (Zn) content hinders its use in soils. The risk associated to its use, does not depend on the total heavy metal content but to the retention phases and metal speciation present in the sludge, which will determine the mobility and bioavailability of the metals. In this research, Cu and Zn availability assessment is determined by applying sequential speciation methodologies to determine both the risk associated with the use of this sludge as a soil improver and fertilizer, and the metal distribution in the sludge phases to accomplish for a most appropriate and environmentally safe treatment process for their recovery and re-use.