Tributyltin (TBT) and its degradation products, mono‐ (MBT) and dibutyltin (DBT) have been determined in the dissolved and particulate phases of seawater, sediments, and biota collected in some representative open and enclosed coastal areas of the western Mediterranean Sea. The highest levels were found in sediments and seawater of dry docks and marinas, closely related with boating activity and clearly decreasing according to the distance from the point sources. Triphenyl‐ (TPhT) and diphenyltin (DPhT) were also identified for the first time in seawater and sediments collected in marinas, exhibiting concentrations similar to TBT. Concentration ratios between TBT/DBT and TPhT/DPhT in each environmental compartment as well as the field partition coefficients (Kd, K′d, and Kb) of the different tin species point out the complexity of organotin speciation, because accumulation and degradation processes occur at different rates, depending on the environmental compartment.

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The photodegradation of the pesticides chlorpyrifos, fenamiphos and vamidothion in water containing 2-4% methanol was examined. Acetone (5%) was added as photosensitizer in the photolysis of vamidothion. A suntest apparatus equipped with a xenon arc lamp which exhibits a radiation very close to natural sunlight was employed. Analyses were performed by direct injection of the water samples containing the photoproducts into a liquid chromatograph with diode array and thermospray mass spectrometric detection. The major photodegradation products were identified by matching their diode-array spectra with the corresponding spectra of the authentic standards, their retention times and the spectra obtained using positive and/or negative thermospray mass spectrometry. 3,5,6-trichloro-2-pyridinol, fenamiphos sulfoxide and vamidothion sulfoxide were the major photodegradation products from chlorpyrifos, fenamiphos and vamidothion, respectively.