Leaching From Land Disposed Municipal Compost: 4. Heavy Metals

Abstract

The leachates from 17 lysimeters containing composts of varying origin, age (3 and 12 months), and packing depths (15-50 cm) were monitored for a 2.5-year period. This paper reports on the results on heavy metals. The initial leachate concentrations exceeded the drinking water standards for all heavy metals studied (Cd, Ni, Co, Zn, Cu, Pb, Cr), but after one and half year of leaching (c.450 mm leachate) only Ni exceeded the standard. Ni was identified as the most serious heavy metal pollutant but was considered less critical than nitrogen compounds and organic matter previously reported in the leachate, The heavy metal leaching is only moderately affected by compost origin, compost age and packing depth. The first year of leaching released between 0.1% (Pb, Cr) and 1.9% (Ni) of the original compost heavy metal content.