Worldwide Occurrence of Organotins from Antifouling Paints and Effects in the Aquatic Environment - Antifouling Paint Biocides - page 76

Fig. 2 Bioaccumulation of TBT and TPT in Chrionomus riparius at different pH and DOM
concentrations. DOM (23 mg CL -1 ) significantly reduced the bioaccumulation of TBT and
TPT. The reduction was related to speciation depending on the pH (see Fig. 1). The frac-
tion of TPTOH is more than 99%atpH8,whereasTPT + and TPTOH are present in more
similar fractions at pH 5 (61%and39%, respectively). Undissociated TBTOH and TPTOH
can penetrate biomembranes much more easily. After [25]
mus ,butalsoin Daphnia ,fishlarvae Thymallus thymallus [22, 23]. The freely
dissolved bioavailable fraction was reduced by complexation and hydropho-
bicinteractionstoDOM.Thisresultsincomplexesthataretoolargeortoo
polar to penetrate across biological membranes. In natural waters the portion
of TBT and TPT sorbed to humic and fulvic material is unavailable for uptake
via epithelial surfaces.
3
Environmental Distribution
Organotins leaching from antifouling paints from ship hulls are diluted into
their surroundings. Biodegradation, adsorption to suspended particulates
and subsequent scavenging to sediments are important removal processes.
Bioaccumulation is also important. In mussels, organotin levels are of sev-
eral orders of magnitude higher than in water [14, 28]. Because TBT and
TPT associate with natural sorbents and because they are persistent under
anoxic conditions [14, 19, 29], they accumulate in marine and freshwater
sediments. TBT occurs in harbor waters to 95 to 99%inthedissolved
phase. Particle-water ratios K p range between 10 3 -10 4 (Lkg -1 ) [4]. Particle-