Bioaccumulation and ecotoxicity increase during indirect photochemical transformation of polycyclic musk tonalide: A modeling study

Polycyclic musks (PCMs) have recently caused a worldwide environmental concern due to their bioaccumulation potential and ecotoxicological effects. Herein, the OH-initiated indirect photochemical transformation mechanism, environmental fate and ecotoxicity of PCMs (by taking tonalide as an example) were theoretically studied. Results show that tonalide can be degraded readily through OH-addition and H-abstraction pathways, with total rate constants of 6.03 × 109–15.8 × 109 M−1 s−1. The OH-addition pathways were dominant at low temperature (<∼287 K), whereas H-abstraction was the dominant pathway at high temperature. Further, the bioconcentration factors (BCF) and aquatic toxicities to fish of all transformation products from H-abstraction pathways were smaller than tonalide. In contrast, these values of most intermediates from OH-addition pathways were up to 8 times higher than tonalide. Particularly, the resultant phenolic product PC1 had a BCF of 5590 L/kg wet-wt, which exceeds the cutoff criterion set for the typically persistent organic pollutants as critically bioaccumulative. Notably, PC1 would mainly be produced under anaerobic aquatic conditions at low temperatures. Therefore, particular attention should be paid to the indirect photochemical products and parental PCMs, particularly the intermediates from OH-addition pathway.