» Soil

Polydimethylsiloxanes (PDMS) degrade when they are added to agricultural or other soils as a component of sludge. This is a complex process that is initiated by contact with the clay component of the soil. It is fastest under dry conditions, but once the silicone molecules are 'unlocked', biological degradation can follow. Experiments show that the degradation products may either evaporate into the air or, depending on the soil type, degrade further in the soil. In either case the ultimate degradation products are silica and carbon dioxide, thus completing the PDMS life cycle. A similar mechanism has been shown to operate for VMS during degradation in the atmosphere.

In view of the significance of the soil compartment in the life cycle of PDMS, a number of studies have been conducted on various soil-living animals and plants. For example, there was no evidence of uptake or adverse effects on worms or crops such as wheat or soybean grown in sewage sludge amended soils containing PDMS.

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