partition to 5 ppm for a "hot spot" model based on previous dye 
discharge experiments. 
New chemical methods based on gas chromatography/mass spec¬ 
trometry analysis of DBP (dibutylphthalate) and DEHP (di(2- 
ethylhexyl)phthalate) were developed. The relative standard de¬ 
viation was demonstrated at + 20 percent of the 0.1 ppm level in 
sediment. Accuracy is more difficult to specify, but this may 
be judged on the basis of split samples measured by an independ¬ 
ent laboratory (0.3 ppm) and our own data (0.1 ppm). 
MICROBIAL TRANSFORMATION OF TIN 
This work was undertaken to determine if tin or products re¬ 
sulting from the biotransformation of tin may contribute to oys¬ 
ter mortality in the Chester River, Maryland. 
Data were collected at two sites in the River: Spaniard 
Bar, which suffered extensive oyster mortality, and Buoy Rock, 
which did not exhibit extensive oyster mortality. Three sites 
associated with potential sources of tin in the River were also 
studied: the Tenneco plant and the Campbell's Soup plant, both 
near Chestertown, Maryland, and the Chestertown sewage treatment 
plant. For comparison, some samples were taken in Baltimore 
Harbor, a site known to be polluted with heavy metals, and in 
Tangier Sound near Tilghman Island, a site regarded as relatively 
free of pollution. 
Water and sediment samples were examined for total viable 
counts of microorganisms, for counts of microorganisms resistant 
to inorganic tin, and for counts of microorganisms resistant to 
organic tin. Sediment from each site was used as inoculum for 
cultures to determine if microorganisms at the site could trans¬ 
form inorganic tin to volatile (organic) tin compound(s). Water 
and sediment were assayed for tin content. 
Among physiochemical parameters measured onsite, only low 
dissolved oxygen is a potential contributor to oyster mortality. 
Microorganisms resistant to inorganic tin were detected in all 
samples and most samples contained microorganisms resistant to 
organotin, although organotin was more toxic than inorganotin to 
the microbial flora. Microorganisms capable of converting in¬ 
organic tin to volatile tin compound(s) were present at every 
site. Comparison of tin concentrations at the several sites 
showed that it is not possible to attribute the oyster kill 
solely to tin, although interaction with other stress factors is 
possible. 
This work was submitted in fulfillment of contract # 
R805976010 by the University of Maryland, Chesapeake Biological 
Laboratory under contract to the Maryland Water Resources Admin¬ 
istration and sponsored by the U.S. Environmental Protection 
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