Subject: Re: Lead shot
Date: Jul 19 10:38:29 1995
From: James Neitzel - neitzelj at elwha.evergreen.edu


I have had students, as a chemistry project, measure lead levels in soil
and plant material in areas of Tacoma. By comparison with results from
earlier work, it appears that small but detectable amounts of lead are
taken up by the species looked at (Doug-fir and alder), as well as some
cadmium. These levels are lower than those seen several years ago,
suggested that either the 1) the absorbable lead has been mostly removed,
2) the lead has moved somewhere else in the soil, or 3) much lead has
been removed in foilage and via street sweepings and lawn bagging is now
in land fills.

There is a great deal of interest in utilizing plants that by nature of
their metabolism selectively absorb various elements as a way of
cleaning up soil lead levels. (Someone even got a National Endowment for
the Arts grant for a garden design utilizing these plants in Minnesota.)
Mercury is another story-many bacteria carry genes for enzymes that
protect them from mercury, which often result in the conversion of
elemental mercury to methylmercury and other organic compounds. This was
the basis of the well doumented inceidence of extreme human birth defects
in Japan, where the chor-alkali industry discarded spent seawater,
containing mercury (used as an electrode) into the ocean. Bacteria
convert mercury into methylmercury, which is fat soluble and enters the
food chain. Pregnant women eat fish from this food chain, resulting in
severly retarted and deformed children. SO FAR AS IS KNOWN, lead is not
subject to this kind of mobilization and is extremely insoluble in sea
water, which is very basic. In acid soils or very acid fresh waters,
(for example, in acid-rain altered northern lakes with little buffering
capacity), lead salts could be moderately soluble.

Jim Neitzel
neitzelj at elwha.evergreen.edu