Loss rates of acetone in filtered and unfiltered coastal seawater

Loss rates of acetone were measured in filtered and unfiltered seawater samples over a 12 month time period at a Pacific Ocean coastal site in Orange County, Southern California, USA, using purge and trap isotope-dilution gas chromatography–mass spectrometry (GC/MS). The average measured first-order rate constant for acetone loss in unfiltered seawater (biotic and abiotic rate) was 0.12 ± 0.05 h− 1 corresponding to a half-life of 5.8 ± 2.4 h. The observed loss rate in filtered seawater (abiotic rate) was less than 10% of this. Seasonal variations were observed, with higher loss measured in winter and after rain events. Diurnal effects were also observed, with loss rates higher earlier in the day and lower at noon. These are attributed to seasonal and temporal variations in bacteria concentrations, suggesting that bacterial metabolism may be the primary loss process for acetone in urbanized coastal waters.