TABLE 3.—Chemical analyses of sediment-trap samples—Continued 
260 ym 
a eet eA Se Sod ee Lo Me 
Field Lab Al Ba Cd Cr Cu Fe Hg Mn Ni Pb V Zn 
number number (4) _* _(ppm)__(ppm)__ (ppm) (ppm)__(%)_—_— (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) 
$T403-00-03Y W-226336 2.60 260 -050 760.0 6.0 1.50 Ol 200 34.0 13.0 34.0 68.0 
ST536-02-04Y W-226338 2.90 270 096 36.0 11.0 1.60 03 250 18.0 16.0 31.0 50.0 
ST537Y W-226339 2.80 260 e150 33.0 14.0 1.60 -03 280 16.0 15.0 34.0 48.0 
<60 um (X) and >60 um (Y) 
Field Lab Al Ba Cd Cr Cu Fe Hg Mn Ni Pb Vv Zn 
number number (%) (ppm) (ppm) (ppm) __ (ppm) __(%)__(ppm)_(ppm) (ppm) __(ppm)__((ppm)_(ppm) 
$T424-00-04X W-226329 3.60 1500 -600 51.0 14.0 2.90 04 390 33.0 31.0 74.0 170.0 
ST424-00-O04Y W-226337 2.10 870 -380 31.0 10.0 1.50 03 240 10.0 15.0 31.0 91.0 
STOO1-—00-08X W-226332 3.60 190 250 54.0 17.0 3.20 04 350 36.0 30.0 78.0 88.0 
STOO1-00-08Y W-226340 3.00 230 120 42.0 13.0 2.50 02 310 24.0 24.0 62.0 55.0 
lgothner and others, 1984b. 
Depth interval (cm) in sediment-trap sample. 
3w=whole sediment trap homogenized before analysis. 
subsurface sediments and migrates upward into 
oxidizing sediments, where it precipitates. Suf- 
ficient reducing conditions in the sediments for 
the characteristic migration and precipitation of 
Mn have been observed in the interstitial water 
of core 83G9-B (K. O. Buesseler and EH. R. 
Sholkovitz, Woods Hole Oceanographic Institu- 
tion, written commun., July 1984) as well as in the 
total sediment phase (appendix table 4D). The 
absence of a gradient in Ba or Ba/AI at all four 
locations, which represent different sediment 
types, suggests that the gradients measured closer 
to drilling sites are not due to diagenetic 
reactions. 
An additional point regarding core 83G9-B, 
from 1,250-m water depth on the slope, is that con- 
centrations of Pb are higher in the surficial sedi- 
ment than in the subsurface sediment (appendix 
table 4D). The source of this Pb is probably the 
burning of lead alkyls in gasoline in coastal 
metropolitan areas, which began in 1924 and which 
has dramatically increased each year since 1940 
until the recent switch to unleaded gasoline. 
Atmospheric transport of Pb with the prevailing 
westerly winds would introduce Pb to surface 
waters offshore. Similar profiles of lead were 
observed in sediments near Station 13A collected 
before drilling began (Bothner and others, 1981). 
We also analyzed sediment profiles from loca- 
tions west of the drilling activity where deposition 
of transported drilling mud was expected (fig. 16). 
Both Ba and Ba/AI at station M10-12-00-GX are 
slightly enriched in the surface 8 cm compared 
to the deeper section of the core (fig. 16C). This 
enrichment supports the conclusion that Ba has 
been transported to this station (see p. 13 and 
fig. 9). At locations OC140-39 and OC140-41 to 
the east of transect III (fig. 1), the Ba concen- 
trations of fine-fraction samples in the upper 
5 cm are about the same as those in deeper sec- 
tions in the sediments, but there is a slight 
enhancement in the Ba/AI ratio in the surface sedi- 
ment (fig. 16A, B). This enhancement is 
statistically significant at the 99.9-percent level of 
confidence (t test). At stations M12-19 and M12- 
21, small increases in the Ba/AI ratio occur in the 
surficial sediment, but no increase occurs in the 
Ba concentration (fig. 16D, F). Profile M12-20 
shows no increase in either Ba or Ba/AI (fig. 16£). 
At stations 19, 20, and 21, an increase in both Ba 
and Ba/AI in the surface sediments was measured 
at the time of cruise 9 (reported in Bothner and 
others, 1984b). 
The Ba and Ba/AI profiles at stations M12-05 
and M12-16, adjacent to drilling locations in 
blocks 312 and 410, respectively, show much 
higher concentrations than at any of the other 
more distant stations (fig. 17A, B). These profiles 
illustrate two points. First, fine-grained Ba-rich 
particles have penetrated to a depth of at least 15 
cm since the drilling began at these locations. 
Second, the subsurface maximum in concentration 
suggests either that new sediments, having a 
lower Ba concentration, have accumulated on top 
of the drilling mud components or that new sedi- 
ments have been exchanged (no net accumulation) 
20 
