Salinity impacts on water solubility and N-octanol/water partition coefficients of selected pesticides and oil constituents

Salinity has been reported to influence the water solubility of organic chemicals entering marine ecosystems. However, there is limited data available on salinity impacts for chemicals potentially entering seawater. Impacts on water solubility would correspondingly impact chemical sorption as well as overall bioavailability and exposure estimates used in the regulatory assessment. Pesticides atrazine, fipronil, bifenthrin, cypermethrin, as well as crude oil constituents dibenzothiophene as well as 3 of its alkyl derivatives all have different polarities and were selected as model compounds to demonstrate the impact of salinity on their solubility and partitioning behaviour. The n-octanol/water partition coefficient (KOW) was measured in both distilled-deionised water as well as artificial seawater (3.2%). All compounds had diminished solubility and increased KOW values in artificial seawater as compared to distilled-deionised water. A linear correlation curve estimated salinity may increase the log KOW value 2.6% per one log unit increase in distilled water (R(2) ?=?0.97). Salinity appears to generally decrease the water solubility and increase partitioning potential. Environmental fate estimates based upon these parameters indicate elevated chemical sorption to sediment, overall bioavailability, and toxicity in artificial seawater. These dramatic differences suggest that salinity should be taken into account when conducting exposure estimates for marine organisms.

Authors: Saranjampour P, Vebrosky EN, Armbrust KL. ;Full Source: Environmental Toxicology & Chemistry. 2017 Mar 6. doi: 10.1002/etc.3784. [Epub ahead of print] ;