Occurrence of Toxic Organometal Species in the Aquatic Environment
Jon M. Bellama
Department of Chemistry, University of Maryland
About the Lecture
The presence of toxic species, including heavy metals and organometals, has significantly altered the character of the Chesapeake Bay and other waterways. In order to control these species, their chemical transformations and interactions in water and in sediment must be understood. The occurrence of several organometal substances in the aquatic environment will be discussed with special emphasis on silicones, methylmercury species, and tributyltin species. The analytical problems of measuring these species, which occur at ultratrace levels, will be discussed. Some of the analogous problems, e.g., cadmium, facing the newly emerging democracies of Eastern Europe, with special emphasis on the Czech Republic, will also be mentioned.
About the Speaker
Mr. Bellama received his Ph.D in chemistry from the University of Pennsylvania in 1966 and immediately joined the faculty of the Department of Chemistry, University of Maryland, College Park. He has been a Science Research Council fellow in Great Britain, a National Academy of Sciences Exchange Scientist on several occasions in the Czech Republic, an invited lecturer for the (former) Soviet Academy of Sciences, a visiting Professor at the University of Paris (XI), and a Senator J. W. Fulbright scholar in the Czech Republic. His research interests comprise the above environmental topics, organosilicon chemistry, nuclear magnetic resonance, and science education.
The President, Mr. Spargo, called the 2018th meeting to order at 8:15 p.m. on November 19, 1993. The Recording Secretary read the minutes of the 2017th meeting and they were approved.
The speaker for the 2018th meeting was Jon M. Bellama of the Department of Chemistry, University of Maryland, and the title of his talk was “Occurrence of Toxic Organometal Species in the Aquatic Environment”.
Mr. Bellama indicated his work is trying to combine the analytical and environmental viewpoints of the problem of toxic organometal species. The analytical approach determines how to measure the species to determine the amount present, whereas the environmental approach determines how the species interacts with the environment. One well-known toxic metal that Mr. Bellama discussed in detail is mercury. As an element, mercury is magical, a shiny dense liquid at standard conditions and insoluble in water. Mercury is toxic if swallowed and is easily absorbed through the skin. Mercury enters the food chain primarily as an organometal such as methyl mercury, a mercury ion bound to a methyl group. Methyl mercury is water and lipid soluble so that the mercury tends to accumulate in the brain and other tissues. Since organometals are water soluble, they are easily mobilized and transported in the environment. Most sources for organometals are human activities.
Mr. Bellama discussed measurements of non-speciated mercury in the Chesapeake Bay. Hot spots are located in Baltimore harbor, near the Bay Bridge, and near the Delaware canal. For Baltimore harbor, the water itself had concentrations that were about a one-thousandth the concentrations found in the sediment and in plankton, which were about a part per million. The mercury in the sediment is often stirred up by dredging operations.
Mercury has been found to be methylated by other methyl metals also found in the water and by microorganisms. Organosilicon compounds that are commonly used to dissolve mercury were found to methylate mercury faster than methylated metals. Specifically, organosilanes had rapid reaction rates with mercury. Silicone polymers, which are common materials used in products such as anti-foaming agents and gaskets, were found to react similarly with mercury.
Mr. Bellama closed his talk by discussing conditions in the Czech Republic. Southern Bohemia is still pristine but the forests on the Polish border have been destroyed. Further, one of the three reservoirs that provide water to Prague is threatened with pollution, particularly fertilizer runoff. Lead and cadmium are the significant toxic metal species present here and in the rest of Eastern Europe. Mr. Bellama then kindly responded to questions from the audience.
The President thanked the speaker for the Society. The Vice President announced two new members. The President then announced the next meeting, made the usual parking announcement, and adjourned the 2018th meeting to the Social Hour at 9:37 p.m.