• • Trifluoropropylmethylsiloxanes (D3F, D4F) in Bohai Bay sediments ranged <LOD–17.1 ng/g dw (mean 5.6 ng/g, detection 30%), and in mollusks <LOD–20.2 ng/g ww (mean 4.1 ng/g, detection 21.7%), indicating widespread but low-level contamination compared to legacy dimethylsiloxanes.
• • Despite lower BSAF values (D3F: 0.67, D4F: 0.61 vs. D4: 1.11, D5: 1.35, D6: 0.97), trifluoropropylmethylsiloxanes exhibited higher annual accumulation rates from 2017–2023: 21.5% in sediments and 32.8% in mollusks, versus 10.2% and 6.7% for dimethylsiloxanes, signaling a rising environmental burden.
• • Stronger sediment sorption (lg KOC: 6.77 for D3F, 8.81 for D4F vs. 4.22–5.99 for D4–D6) and slower elimination in mollusks (half-lives: 11.1 d for D3F, 20.1 d for trans-D4Fa vs. 5.4–8.6 d for D4–D6) drive the differential accumulation, with implications for food web transfer and ecological risk.
• • The degradation product methyl(3,3,3-trifluoropropyl)silanediol was detected in sediments (mean 15.7 ng/g dw) and mollusks (mean 31.2 ng/g ww), with a 1.4 times faster annual increase in mollusks (24.2%) than sediments (13.7%), suggesting its utility as a bioaccumulation indicator for trifluoropropylmethylsiloxanes.