Page 677 - The Toxicology of Fishes

Exposure Assessment and Modeling in the Aquatic Environment 657

1,865,000 Legend
140,200 PCB = 101
15,500 uptake by ingestion
2,023,000 uptake by respiration
156,300 loss by respiration
Log K ow = 6.4 loss by egestion
loss by metabolism
Salmonid ʻlossʼ by growth
f = 104.6 2,184,000 (all above in pg/day)
Alewife 14,200
c = 419.7 Chemical Fugacity (nPa):
1,379,000 f = 68.8 536 f W – in water
606,000 c = 120.8 13.530 f S – in sediment
Smelt 14,920 1157 f – in organisms
f = 95.08 212 7690 PCB concentration (mg/m )
3
c = 95.4 7625 c – in organisms
763 9 930
7007 Mysid
5111 f = 24.08
24,870 c = 24.2 19.9
Sculpin 16,430 7460 0.03
f = 83.6 48.3
c = 167.7 575
36.3
99.8 Plankton
398 84.5 16.6 f = 10.03
c = 3.7
3211 452.8 9831 f w = 10.36 1.51
2 439 0
126
1.46 0.05
Pontoporeia
44.05 f = 120.5 f S = 131.3 Oligochaete
c = 90.6 460
40.4 0.002 f = 118.6
3.64 416 44.6 0 c = 29.7
FIGURE 14.5 An example of a complex food web model (Lake Ontario food web); the concentrations, fugacities, and
fluxes (µg/day) for PCB congener 101 are shown. (From Campfens, J. and Mackay, D., Environ. Sci. Technol., 31, 577–583,
1997. With permission.)

physiologically based pharmacokinetic (PBPK) models are invaluable when exploring how chemicals
become distributed in fish. Examples are the models of Gobas et al. (1993). It is also possible to build
models of food chains or food webs in which a variety of organisms feed on each other transferring
contaminant by ingestion. Figure 14.5 is an example of an attempt to model the fate of a PCB congener
in the complex Lake Ontario food web (Campfens and Mackay, 1997).
This chapter has sought to convey the principles underlying mass balance modeling in both the abiotic
and biotic spheres and has provided a glimpse into the benefits derived from obtaining a full quantitative
understanding of contaminant fate in aquatic systems. Again, the complementary nature of monitoring
efforts and modeling tools is emphasized. Both can contribute, along with laboratory investigations, to
a fuller understanding of how chemical substances can impact fish and other aquatic organisms.

References

Ambrose, R. B. (1988). WASP4, A Hydrodynamic and Water Quality Model: Model Theory User’s Manual
and Programmers Guide, EPA-600-3-87-039. U.S. Environmental Protection Agency, Athens, GA.
Barber, M. X., Suarez, L. A., and Lassiter, R. R. (1991). Modelling bioaccumulation of organic pollutants in
fish with an application to PCBs in Lake Ontario salmonids. Can. J. Fish Aquat. Sci., 48, 318–337.
Burns, L. (2002). Exposure Analysis Modeling System (EXAMS): User Manual and System Documentation,
EPA-600-R-00-81/Rev. F. U.S. Environmental Protection Agency, Research Triangle Park, NC.
Campfens, J. and Mackay, D. (1997). Fugacity-based model of PCB bioaccumulation in complex aquatic
foodwebs. Environ. Sci. Technol., 31, 577–583.