B.2 Transformations in the Environment
267
concepts of biomagnification and bioaccumulation. As shown in Eq. B.4, the
biomagnification factor (BMF) is the ratio of an organism’s internal concentration of
a chemical to the chemical’s concentration in the organism’s food source. The BMF
represents the ability for the chemical’s concentration to increase in organisms up
the food chain (at higher trophic levels):
BMF = c biota /c diet
(B.4)
• BMF: biomagnification factor [kg diet/kg biota]
• c biota : concentration of substance in the organism from uptake via the food web
[mol/kg biota]
• c diet : concentration in the organism’s diet [mol/kg diet]
The bioaccumulation factor (BAF) is defined in Eq. B.5 and is similar to the
bioconcentration factor (BCF). The important difference is that the BAF considers
all routes of exposure to the chemical (not just from surrounding water):
BAF = c biota /c surroundings
(B.5)
• BAF: bioaccumulation factor [kg surroundings/kg biota]
• c biota : concentration of substance in the organism from uptake via any possible
pathway [mol/kg biota]
• c surroundings : concentration in the organism’s surroundings [mol/kg surroundings]
B.2
Transformations in the Environment
B.2.1 Biodegradation
Biodegradation of chemicals in the environment occurs often in the water, soil, and
sediment compartments. This microbial degradation process can be approximated
by a pseudo first-order reaction for low environmental concentrations of the
chemical undergoing biodegradation:
r biological = −
dc
dt
biological
= k b × c
(B.6)
• r: biodegradation rate [mol m −3 s −1 ]
• c: concentration of chemical undergoing biodegradation [mol/m 3 ]
• k b : pseudo first-order rate constant for biodegradation [s −1 ]
267
concepts of biomagnification and bioaccumulation. As shown in Eq. B.4, the
biomagnification factor (BMF) is the ratio of an organism’s internal concentration of
a chemical to the chemical’s concentration in the organism’s food source. The BMF
represents the ability for the chemical’s concentration to increase in organisms up
the food chain (at higher trophic levels):
BMF = c biota /c diet
(B.4)
• BMF: biomagnification factor [kg diet/kg biota]
• c biota : concentration of substance in the organism from uptake via the food web
[mol/kg biota]
• c diet : concentration in the organism’s diet [mol/kg diet]
The bioaccumulation factor (BAF) is defined in Eq. B.5 and is similar to the
bioconcentration factor (BCF). The important difference is that the BAF considers
all routes of exposure to the chemical (not just from surrounding water):
BAF = c biota /c surroundings
(B.5)
• BAF: bioaccumulation factor [kg surroundings/kg biota]
• c biota : concentration of substance in the organism from uptake via any possible
pathway [mol/kg biota]
• c surroundings : concentration in the organism’s surroundings [mol/kg surroundings]
B.2
Transformations in the Environment
B.2.1 Biodegradation
Biodegradation of chemicals in the environment occurs often in the water, soil, and
sediment compartments. This microbial degradation process can be approximated
by a pseudo first-order reaction for low environmental concentrations of the
chemical undergoing biodegradation:
r biological = −
dc
dt
biological
= k b × c
(B.6)
• r: biodegradation rate [mol m −3 s −1 ]
• c: concentration of chemical undergoing biodegradation [mol/m 3 ]
• k b : pseudo first-order rate constant for biodegradation [s −1 ]