80 
3 S 3 
WN 
[e) 
WEIGHT PERCENT OF TOTAL SAMPLE 
-500 500-210 
Aaa 
-105 
105-60 
JMIO-2 
MIO -16 
MIO-5-2 
60-30 
30-10 0-1 <| 
SEDIMENT-SIZE CLASSES, IN ym 
FIGURE 10B.—Weight percent of sediment in different size fractions of bottom sediment collected on cruise 10 at control sta- 
tion 2, regional station 16, and site-specific station 5-2 on Georges Bank. 
a greater density than the average sediment on the 
bank, the rates of removal determined for barium 
may provide some insight into the fate of future 
contaminants that reach the sediments on Georges 
Bank. 
To determine the inventories of Ba within the 
6-km-radius circle (fig. 1B), the Ba concentrations 
on each ring of the sample pattern were aver- 
aged and then used to estimate a representative 
concentration for each annulus around the drill 
site. We assume that the Ba added by the intro- 
duction of drilling mud is contained within the 
sampling depth interval of 0-2 cm. This assump- 
tion is valid until at least cruise 5, based on core 
profiles from station 5-1 reported in the second 
year final report. For comparison to the amount 
of BaSO, used in the drilling operation, we have 
22 
converted both predrilling and postdrilling Ba 
concentrations to BaSO,. The inventory of barite 
is calculated from the field data with the follow- 
ing relation: 
Total=  A-d-Z-C: (BaSO,/Ba) 
where A=area of each annulus, d=bulk density 
of dry sediment (1.6 g/cc), Z=depth interval (0-2 
cm), C=concentration of Ba (ug/g), and 
BaSO,/Ba=the ratio of molecular weights. 
We estimate that the inventory of BaSO, in the 
upper 2 cm of sediment in the 6-km circle totals 
0.59X10® to 0.62X10® lb before drilling began 
(cruises 1 and 2). The inventory increases to 
0.86 X10® Ib on cruise 5 just after drilling stops 
(net increase of 0.27X10® lb) and decreases to 
