Experimental Freshwater Microcosm Biodegradability Study of Butyl Benzyl Phthalate

WJ Adams; WJ Renaudette; JD Doi; MG Stepro; MW Tucker; RA Kimerle; BB Franklin; JV Nabholz

doi:10.1520/STP10278S

SYMPOSIA PAPER Published: 01 January 1988

STP10278S

Experimental Freshwater Microcosm Biodegradability Study of Butyl Benzyl Phthalate

Source

A 30-day freshwater microcosm study was conducted to measure the biodegradability of butyl benzyl phthalate (BBP) in water and sediment. Microcosms were designed to simulate the flow rate, water to sediment surface ratio, and environmental conditions of the Illinois River. Water and undisturbed sediment cores were brought into the laboratory from the Illinois River and placed in 53-L all-glass microcosms. BBP was tested at 10 and 100 μg/L and at 100 μg/L sterilized with five replicates at each concentration. BBP was added to each microcosm three times per week at one half the initial dose. The microcosms were sealed to trap radiolabeled carbon dioxide (¹⁴C-CO₂) for purposes of assessing mineralization and obtaining a mass balance on each microcosm. Uniformly ring-labeled ¹⁴C-BBP was used as the test material and analyses were performed for parent BBP as well as for carbon-14 (¹⁴C) intermediates.

The results of this study indicated that BBP was readily degraded in both water and sediment. The estimated half-life in water for primary degradation was typically two days or less. Mineralization of BBP did occur, with an average of 10.4% of the total BBP dosed in each microcosm trapped as ¹⁴CO₂. Concentrations of BBP on the sediments were lower than predicted from sediment partition coefficients. (200 to 600 μg/kg) and ranged from 7 to 23 μg/kg. Both the sediment and water analyses showed that the majority of the ¹⁴C activity detected was not BBP. The transient appearance of primary metabolites was observed, however, the preponderance of ¹⁴C remaining in solution was not BBP.

A mass balance of each component (water, sediment, carbon dioxide, and so forth) in each microcosm indicated that 78.2% of the total amount of ¹⁴C-BBP added to the microcosms could be accounted for. Approximately 50% of the mass remained as ¹⁴C metabolites in the water, and only 1.8% and <0.1% were found as ¹⁴C and parent BBP, respectively, on the sediment. The remainder of the ¹⁴C-BBP was found on the glass, in silicone joints and stoppers, in evolved CO₂, or was removed by water sampling.

The collective data indicate that BBP should not be a persistent chemical in freshwater aquatic environments.

Author Information

Adams, WJ