Messenger - Vol. 3, No. 4, Page 10 Summer 1994 Rainwater keeps dropping metals into the sea Rainwater from Bermuda, Barbados, Ireland and the Canary Islands helps Thomas M. Church, professor of marine studies, determine how air pollutants enter and interact with the sea. In the Lammot du Pont Laboratory on campus, Church and his associates analyze rainwater samples for traces of atmospheric pollutants generated on the North American and European continents. Using sensitive analytical techniques, they are able to compare present-day levels of certain elements with pre-industrial levels. "For that, we use ice cores taken, for example, from Greenland," Church says. "By comparison, most trace elements are found at extremely low levels in ice cores prior to about 1850." When Church first came to Delaware in 1973, he was involved in calculating inputs, storage and outputs for a variety of trace metals in seawater-elements like lead, copper and zinc that typically occur in very small quantities. But, for many of these elements, the inputs and outputs didn't balance: transport by rivers could only partly account for levels found in the open ocean. So, Church began monitoring the chemical composition of rainwater at a site in Cape Henlopen State Park near Lewes, Del. These records, maintained for more than 16 years, now form one of the longest and most important records of rainwater chemistry in the world. "Our analysis of rainwater over the years has revealed a significant input of nitrogen and toxic metals to the Delaware estuary and no significant change from an average pH of 4.3, approximately the same acidity as tomato juice," says Church. But, Church and marine laboratory technical coordinator Joe Scudlark have documented a six- fold decrease in the amount of lead in rainwater since 1982, when leaded gasoline was phased out. Lead is useful in tracking atmospheric emissions because it occurs naturally in a variety of forms, or isotopes, that allow scientists to determine the date and source of a particular emission. Evidence from Cape Henlopen and corroboration from other sources around the world have led scientists to conclude that the atmosphere is an important pathway for the transfer of nutrients and pollutants to the sea. Chemicals carried by the wind are incorporated into raindrops, washed from the sky and deposited in the ocean below. Once in the sea, these chemicals may play an important role in living systems or react with other ocean constituents. Church has worked to describe and quantify the sources and fates of such input, first collecting rainwater data from Bermuda more than 10 years ago. By 1986, he established his first transoceanic station in Ireland. Samples from Ireland did contain elements traceable to North America, but the levels were less than 10 percent of those he had encountered previously, challenging the limitations of Church's analytical techniques and equipment. An opportunity to create a state-of-the-art trace element laboratory arose in 1989 when the Collge of Marine Studies joined forces with the Department of Chemistry and Biochemistry to develop plans for the Lammot du Pont Laboratory. Among the built-in features are an uninterrupted power supply with back-up battery systems, a filtered air supply to keep dust out, a deionized and filtered water supply and no metallic surfaces. Laboratory implements are coated with Teflon or made of inert plastics. "I believe this lab is really going to be world class," says Church. "It will be among the best of about a dozen such labs that now exist in the U.S." -Elizabeth A. Chajes