Chapter 10
Occurence, Pathways and Bioaccumulation
of Organometallic Compounds in
Marine Environments
R. Frache . P. Rivaro
10.1
Introduction
The last fifteen years have seen a growing concern for several classes of hydrophobic
contaminants such as polychlorobiphenyls, polycyclic aromatic hydrocarbons and
more lately organometallic compounds. Organometallic compounds occur in the environment as a result of direct anthropogenic inputs or because they are naturally
formed there. They are used in a wide variety of industrial processes sometimes at
the percent level. Some organometallic forms of Hg, As and now Pb have been observed
to have efficient biocidal properties. This fact has largely been applied to the synthesis of a large variety of pesticides, leading then to direct introduction in the environment. In this paper the marine environmental impact of some organotin compounds
will be examined.
10.2
Organotin Compounds: Environmental Chemical Aspects
Organotin compounds consist of a single central Sn atom covalently bound to one to
four organic groups [RxSn(4_n)j. In Fig. 10.1 general forms of organotin compounds are
shown. The introduction of organic groups increases the toxicity of the molecule reaching a maximum for trisubstituted compounds. The sensitivity shown by different types
of organisms also depends on the nature of the organic substituent. For example,
marine organisms are very sensitive to tributyltin (TBT) and triphenyltin (TPhT)
substitutes. Organotin compounds are generally of anthropogenic origin apart from
methyltins, which may be produced by environmental methylation as well. After
recognising the biocidal properties of trialkylated organotins in the 1950S, the variety
of applications increased considerably. Total worldwide use of organotin compounds
increased from about 5000 tons annually at the beginning of the sixties to over
60000 tons annually in the late eighties. To date, organotins - butyltin and phenyltin
- are the most widely used organometallic compounds (Morabito et al. 1995; Ritsema
1997). Butyltin compounds are mainly used as stabilizers for polyvinylchloride and as
biocides.About 23% of the total worldwide organotin production is used as agrochemicals and as biocides in a broad spectrum of applications. However their environmental impact is far more than for organotins used as stabilizers due to direct introduction into the environment. The organotins used as antifouling agents (both tributyltin
and triphenyltin) or agrochemicals (triphenyltin) will give direct input into the (marine) environment. Tributyltin (TBT) was in the 1970S and 1980s mainly used as a biocide in antifouling paints for ships, pleasure boats and docks. Since the eighties there
Occurence, Pathways and Bioaccumulation
of Organometallic Compounds in
Marine Environments
R. Frache . P. Rivaro
10.1
Introduction
The last fifteen years have seen a growing concern for several classes of hydrophobic
contaminants such as polychlorobiphenyls, polycyclic aromatic hydrocarbons and
more lately organometallic compounds. Organometallic compounds occur in the environment as a result of direct anthropogenic inputs or because they are naturally
formed there. They are used in a wide variety of industrial processes sometimes at
the percent level. Some organometallic forms of Hg, As and now Pb have been observed
to have efficient biocidal properties. This fact has largely been applied to the synthesis of a large variety of pesticides, leading then to direct introduction in the environment. In this paper the marine environmental impact of some organotin compounds
will be examined.
10.2
Organotin Compounds: Environmental Chemical Aspects
Organotin compounds consist of a single central Sn atom covalently bound to one to
four organic groups [RxSn(4_n)j. In Fig. 10.1 general forms of organotin compounds are
shown. The introduction of organic groups increases the toxicity of the molecule reaching a maximum for trisubstituted compounds. The sensitivity shown by different types
of organisms also depends on the nature of the organic substituent. For example,
marine organisms are very sensitive to tributyltin (TBT) and triphenyltin (TPhT)
substitutes. Organotin compounds are generally of anthropogenic origin apart from
methyltins, which may be produced by environmental methylation as well. After
recognising the biocidal properties of trialkylated organotins in the 1950S, the variety
of applications increased considerably. Total worldwide use of organotin compounds
increased from about 5000 tons annually at the beginning of the sixties to over
60000 tons annually in the late eighties. To date, organotins - butyltin and phenyltin
- are the most widely used organometallic compounds (Morabito et al. 1995; Ritsema
1997). Butyltin compounds are mainly used as stabilizers for polyvinylchloride and as
biocides.About 23% of the total worldwide organotin production is used as agrochemicals and as biocides in a broad spectrum of applications. However their environmental impact is far more than for organotins used as stabilizers due to direct introduction into the environment. The organotins used as antifouling agents (both tributyltin
and triphenyltin) or agrochemicals (triphenyltin) will give direct input into the (marine) environment. Tributyltin (TBT) was in the 1970S and 1980s mainly used as a biocide in antifouling paints for ships, pleasure boats and docks. Since the eighties there