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
     "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