The decomposition of phthalate esters in soil

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Abstract
Factors affecting the decomposition of carboxyl‐labelled (14C) phthalic acid (PA), monobutyl phthalate (MBP), and dibutyl phthalate (DBP) were studied in soil incubation experiments conducted under labortory conditions. A lag phase of 10 to 20 days occurred before soil microbes initiated metabolism of MBP and DBP while PA was rapidly decomposed. Approximately 90% of DBP added to soils at rates of 0.1 to 0.4% was decomposed within 80 days under both aerobic and anaerobic conditions. Decomposition of DBP was enhanced in soils by increasing soil pH from 5.2 to 7.0, by adding organic matter, and by elevating the temperature from 23°C to 30°C. Varying soil characteristics and the simultaneous addition of ammonium, CaCO3 or sewage sludge had little effect on the rate or extent of DBP degradation. The addition of DBP in sewage sludge or other waste materials to soils should not pose a long‐term persistence problem.