Sequential Extraction of Heavy Metals Found in MSW-Derived Compost

Compost standards usually contain maximum permissible levels of heavy metals. These almost always refer to “total” concentrations. However, more relevant to environmental impact due to compost usage are “leachable” concentrations. This study utilized a sequential extraction technique to evaluate availability of heavy metals present in an MSW-derived compost. Five fractions (A-E) were obtained, the result of progressively stronger leaching solutions. Profiles of fraction distributions varied drastically from metal to metal. Manganese and zinc had very significant amounts in fractions B and C, whereas copper and chromium were present almost entirely in fractions D and E, respectively. Comparisons with other leachate methods are offered.