Figure 2. Mean TBP RSS total error estimation of bioaccumulation potential compared with measured PCDD/F concentrations

ERDC TN-DOER-R5

September 2004

Figure 2.

Mean TBP RSS total error 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)

RSS calculations were also performed using an overall mean BSAF = 0.573 (Table 3) for all

congeners and homologue groups, to determine whether the overall BSAF could produce

adequate TBP predictions. This resulted in larger average method error (157 percent) as well as

larger propagated error and total error, and thus less precise estimates of TBP. Using the overall

mean BSAF, TBP and its uncertainty interval were generally larger than the corresponding

values calculated using congener/homologue mean BSAFs (Figure 3). The relative percent

difference between TBP and mean Ct ranged from 90 percent to nearly +600 percent (Figure 3),

and the broad RSS TBP uncertainty intervals always included mean Ct. On average, TBP

underestimated Ct by 30 percent when congener-specific BSAFs were used, and overestimated

Ct by 137 percent when the overall mean BSAF was used. Excluding homologue groups, the

average relative disparity between TBP and mean Ct was +2 percent when congener-specific

BSAFs were used, and +179 percent when the overall mean BSAF was used.