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Conversion of inorganic and organic selenium compounds to volatile selenium compounds (dimethyl selenide, dimethyl disetenide, and an unknown compound) by microorganisms in lake sediment has been observed. This conversion could also be effected by pure cultures of bacteria and fungi. Such transformations are significant in the transportation and cycling of elements in the environment.

The effects of a number of inorganic and organic tin compounds on pure cultures of green and blue-green algae and natural phytoplankton in lake water were tested. Organic tin compounds were generally more inhibitory to primary production and reproduction of the algae than inorganic tin compounds. The toxicity of organotin compounds varied considerably with the number and nature of the organic groups attached to tin, with trialkyl tin compounds being the most toxic forms. Within a given alkyl tin compound series, the longer the carbon chain, the higher the toxicity. A direct relationship between toxicity and partition coefficients of trialkyl tin compounds was observed. Other tin compounds had no such direct relationship.Key words: algae, tin, toxicity, partition coefficients

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A tissue solubilizer is used to dissolve biological samples without altering the chemical forms of the alkyliead species.The various alkyliead species and lead(II) are Isolated quantitatively by chelation extraction with sodium dlethyldlthlocarbamate, followed by n-butyiation to their corresponding tetraalkyl forms, Rn PbBu(4_",, and Bu4Pb, respectively (R = Me, Et), all of which can be determined by a GC/AAS method. The method determines simultaneously the following species In one sample: tetraaikyllead (Me4Pb, Me3EtPb, Me2Et2Pb, MeEt3Pb, Et4Pb); Ionic alkyliead (Me2Pb2+, Et2Pb2+, Me3Pb+, Et3Pb+); Pb2+. Analyses of sediment, fish, and aquatic weeds are given. Detection limits expressed for Pb are 7.5 ng/g and 15 ng/g, respectively, for biological and sediment samples.

The highly polar and solvated methyltln, dlmethyltln, trlmethyltln, and Sn(IV) species are extracted Into benzene

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