Distribution and behaviour of organotin compounds in the coastal marine environment of the eastern Adriatic

Trisupstituirani organokos i trovi spojevi tributilkositar (TBT) i trifenilkositar (TPhT) korišteni su kao biocidna sredstva u protuobraštajnim bojama. Međutim, nakon što je ustanovljeno njihovo toksično djelovanje prema raznim neciljanim vodenim organizmima, njihova upotreba u tu svrhu zabranjena je u mnogim zemljama diljem svijeta, kao i u Hrvatskoj od 2006. godine. S obzirom da je hrvatska obala Jadrana područje s razvijenim nautičkim turizmom i intenzivnim priobalnim prometom, postoji velika vjerojatnost njenog onečišćenja organokositrovim spojevima, međutim ono do sada nije bilo istraživano. U ovom radu ono je provedeno određivanjem raspodjele organokositrovih spojeva (butilnih, fenilnih, oktilnih i metililnih) u različitim dijelovima morskog okoliša (morska voda, dagnje Mytilus galloprovincialis i sediment) duž cijelog priobalnog područja. Istraživanje je pokazalo da je na gotovo svim ispitivanim lokacijama prisutno zagađen je butil kositrovim spojevima, a najzagađenija su područja intenzivnog morskog prometa (marine i lučice). Također je istraživana stabilnost i ponašanje butilkositrovih i fenilkositrovih spojeva u zagađenim sedimentima te je pokazano kako se njihova razgradnja odvija prije svega u pornoj vodi, pri čemu proces desorpcije sa sedimenta određuje cjelokupan proces njihove razgradnje. Mehanizam i kinetika razgradnje istraživana je primjenom spojeva obogaćenih specifičnim izotopima kositra. Utvrđeno je kako se butilkositrovi spojevi u sedimentu razgrađuju brže od fenilkositrovih spojeva, dok je za obje grupe spojeva najsporija razgradnja trisupstituiranih derivata. Dokazano je kako značajnu ulogu u cjelokupnom procesu razgradnje tributilkositra imaju karakteristike sedimenta, posebice organska tvar koja određuje jačinu adsorpcije, a time i biodostupnu frakciju u pornoj vodi. Dakle, u sedimentima bogatim organskom tvari tributilkositar će biti stabilniji, sporije se razgrađivati i time dulje biti izvor zagađenja za morski okoliš.Trisupstituted organotin compounds, namely tributyltin (TBT) and triphenyltin (TPhT), have been used as biocides in antifouling paints. Since it was established that they are highly toxic to various untargeted aquatic organisms, their usage in antifouling paints is banned in many countries worldwide, as well as in Croatia since 2006. In spite of the fact that Croatian Adriatic coast is an area with highly developed nautical tourism and intensive marine traffic, the level of contamination with organotin compounds was never investigated. In this work a comprehensive investigation of the distribution of organotin compounds (butyl tins, phenyl tins, methyltins and octyltins) in different marine compartments (seawater, mussels Mytilus galloprovincialis and sediments) long the entire coastal area was performed. The results obtained demonstrated that the majority of the investigated location is significantly polluted with butyltins, with the degree of pollution decreasing from marinas and ports to locations which are less exposed to marine traffic. A detailed research of butyltins and phenyltins behaviour and stability in contaminated sediments was performed. It was demonstrated that the degradation is taking place primarily in the porewater, while the critical step in the whole process is their desorption from sediments. The mechanism and kinetic of butyltins and phenyltins degradation was studied by species - specific isotopically enriched tracers. It was demonstrated that the first dealkylation step is the limiting step in their total degradation, while the degradation of butyltins is faster than the degradation of phenyltins. Furthermore, it was shown that sediments characteristics, mainly organic matter, by controlling the desorption influence the TBT degradation efficiency and consequently define its persistence in the contaminated sediments, which thus increase in sediments rich in organic matter