Organic matter and heavy metal uptake

The uptake of the organic matter and heavy metal content of sludge has become increasingly important due to the economically beneficial disposal of sludge for agricultural purposes. The greater portion of heavy metals combined with soil organic matter are insoluble, stable combination with humic substances. The presence of humus in soil is beneficial because it holds heavy elements needed for plant growth for long periods of time and releases them as needed. Deficiencies of these heavy metals are most consistently found in plants grown on peat and muck soils. Low pH causes reduced availability from organic matter relative to the same soil without organic matter; high pH causes this availability to increase. The organic matter degradation rate in soil is dependent on microbial activity. Incubation studies indicated that metal release by sludge decomposition in an alkaline soil did not make these metals available for plant uptake. Other studies indicated that plants grown on soils coor its nauplii.