phthalates are readily degraded by bacteria, photolysis, and 
hydrolysis, it is our belief that the known persistence of alkyl 
phthalates in the marine environment is the result of rapid sorp¬ 
tion by suspended clay-rich matter which eventually settles 
through sedimentation. Once sorbed, the rate of degradation is 
indefinite, but it is slow enough that the phthalates are con¬ 
sidered "persistent." In view of the rapid bioturbation process, 
surficial sediments (upper 10 cm) are quite likely to carry 
memory effects due to accumulative pollution during the previous 
decade. 
The difficult part in the present study was to develop 
reliable methods of measurement since it was felt that none of 
the initially available measurement technology was reliable 
enough or accurate enough for the purposes of this study. 
The principal focus in the work to be presented next is 
based on the significance of the clay-rich sediment regions be¬ 
low a 2-8 m water column. These should contain the residual 
compounds that may help to understand whether threatening or 
tpxoc plasticizer concentrations exist now, or were likely within 
the past decade. Since sedimentation occurs at an estimated rate 
of 1 cm per year, our efforts were focused on values in the top 
10 cm. 
Based on preliminary studies we initially picked sampling 
sites included apex of the mortality. The sites were chosen as 
likely to show whether or not the alkyl phthalates could have 
caused the oyster mortality. The first region is Tenneco Pond 
where the sediment composition was found to be highly polluted. 
The second region involves a series of five samples taken at the 
apex of the oyster mortality. That is where the downstream 
mortality movement was not clearly in evidence. The third region 
is at the mouth of the Chester River. That region is likely to 
contain a representative mixture of pollutants from the upper 
Chesapeake Bay. Since this region is a reference point for pos¬ 
sible upstream river pollution, we used a homogenized sample of 
the river mouth sediment "R" for reference purposes and for in¬ 
dependent analysis. 
Efforts were also made toward development of methods for 
analysis of oyster tissue. We underestimated the problems here 
so that aspect of the study was the last to be completed. These 
results will be presented later in this report. 
EXPERIMENTAL PROCEDURES 
Trace Analysis Techniques 
The key goals in trace organic analysis of sediment are to 
gchieve complete extraction, to avoid loss, to prevent contami 
and to avoid interferences. In preliminary experiments we found 
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