Organic Carbon/Water and Dissolved Organic Carbon/Water Partitioning of Cyclic Volatile Methylsiloxanes: Measurements and Polyparameter Linear Free Energy Relationships
Number of Authors: 4
2015 (English)In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 49, no 20, 12161-12168 p.Article in journal (Refereed) Published
The sorption of cyclic volatile methyl siloxanes (cVMS) to organic matter has a strong influence on their fate in the aquatic environment. We report new measurements of the partition ratios between freshwater sediment organic carbon and water (K-OC) and between Aldrich humic acid dissolved organic carbon and water (K-DOC) for three cVMS, and for three polychlorinated biphenyls (PCBs) that were used as reference chemicals. Our measurements were made using a purge-and-trap method that employs benchmark chemicals to calibrate mass transfer at the air/water interface in a fugacity-based multimedia model. The measured log K-OC of octamethylcydotetrasiloxane (D-4), decamethylcyclopentasiloxane (D-5), and dodecamethylcydohexasiloxane (D-6) were 5.06, 6.12, and 7.07, and log K-DOC were 5.05, 6.13, and 6.79. To our knowledge, our measurements for K-OC of D-6 and K-DOC of D-4 and D-6 are the first reported. Polyparameter linear free energy relationships (PP-LFERs) derived from training sets of empirical data that did not include cVMS generally did not predict our measured partition ratios of cVMS accurately (root-mean-squared-error (RMSE) for logK(OC) 0.76 and for logK(DOC) 0.73). We constructed new PP-LFERs that accurately describe partition ratios for the cVMS as well as for other chemicals by including our new measurements in the existing training sets (logK(OC) RMSEcVMS: 0.09, logk(DOC) RMSEcVMS: 0.12). The PP-LFERs we have developed here should be further evaluated and perhaps recalibrated when experimental data for other siloxanes become available.
Place, publisher, year, edition, pages
2015. Vol. 49, no 20, 12161-12168 p.
Environmental Engineering Earth and Related Environmental Sciences
IdentifiersURN: urn:nbn:se:su:diva-123527DOI: 10.1021/acs.est.5b02483ISI: 000363348700021OAI: oai:DiVA.org:su-123527DiVA: diva2:874968