Figure 4. Bootstrap TBP bootstrap 95-percent confidence interval estimation of bioaccumulation potential compared with measured PCDD/F concentrations (Ct 95 percent confidence interval) for pooled benthic organisms (Table 1) collected in the New York Bight Apex.

ERDC TN-DOER-R5

September 2004

Figure 4.

Bootstrap TBP bootstrap 95-percent confidence interval estimation of bioaccumulation

potential compared with measured PCDD/F concentrations (Ct 95 percent confidence

interval) for pooled benthic organisms (Table 1) collected in the New York Bight Apex. TBPs

calculated with congener- and homologue-specific BSAFs (Table 3). Pairs marked "n.s." are

not significantly different at P > 0.05 by bootstrap test of significance

The bootstrap uncertainty ratio for TBP (bootstrap confidence interval width TBP) was

approximately a factor of two (Table 6). The bootstrap confidence intervals included mean Ct for

the total HxCDF homologue group and for all congeners except 1,2,3,4,6,7,8-HpCDF and OCDF

(Figure 4, Table 6). Tissue concentrations of these two congeners and all the other homologue

groups were underestimated by bootstrap TBP.

When bootstrap simulations were performed using the overall mean BSAF, the resulting

confidence intervals were broader in most cases than when congener/homologue mean BSAFs

were used (Figure 5). Mean Ct fell below the lower bootstrap CL for 1,2,3,6,7,8-HxCDD,

1,2,3,7,8,9-HxCDD, 1,2,3,4,6,7,8-HpCDD, OCDD, OCDF, and total HxCDF, but was otherwise

within the bootstrap confidence interval. The bootstrap relative percent difference between TBP

and mean Ct was 40 percent to +200 percent when the bootstrap confidence interval included

mean Ct, and +130 percent to > +600 percent when mean Ct fell below the lower bootstrap CL.