10.4 Product Risk Assessment
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in the environment due to thermodynamic drivers only and does not consider flows
of the chemical out of the system (e.g., degradation, etc.).
Task: Answer the following:
(a) Use symbolic notation to represent in three equations the concentration of a
chemical in water (w), soil (s), and air (a) (e.g., c s = . . .) in a level I model
using only the following symbols:
• Partition coefficients: K sw , K aw
• Volumes of compartments: V a , V w , and V s
• Assume that only the mass of the chemical in soil (m s ) is known.
(b) Use the small-world level I model (Scheringer and MacLeod, 2021) to determine
the distribution of ASM into the air, water, soil compartments in Europe. To do
this, the following parameters need to be updated within the model:
• Insert the log K ow and log K aw values from Table 10.6.
• Adjust the modeled system to the size of Europe: review external information
to set the variables for (1) total surface area [m 2 ], (2) fraction of area
covered by water, and (3) fraction of area covered by soil. If you cannot find
these values, default values that can be used are provided in the solutions.
Examine the resulting pie chart. According to the level I model, to which
compartments does ASM partition?
Level III Model
The environmental concentrations of ASM can also be estimated with a level III
model. This model type provides a more realistic estimation of the environmental
fate of a chemical by also including the dynamic exchange of materials between
compartments. In this model, the system is assumed to be in a steady-state
condition where continuous chemical input (emissions) is balanced by its output (via
degradation and advection) and all concentrations are therefore time-independent.
Similar to the level I model, the system here is composed of agricultural soil, a water
body, and the air compartment.
Task: Answer the following:
(a) Write down the first-order differential equations for the change in the mass of
a chemical with time (
dm soil
dt
= . . .) in the three compartments soil (s), water
(w), and air (a). When set to zero, these equations represent a level III model.
Include only the following processes and symbols (start by identifying the gain
and loss processes in each compartment):
253
in the environment due to thermodynamic drivers only and does not consider flows
of the chemical out of the system (e.g., degradation, etc.).
Task: Answer the following:
(a) Use symbolic notation to represent in three equations the concentration of a
chemical in water (w), soil (s), and air (a) (e.g., c s = . . .) in a level I model
using only the following symbols:
• Partition coefficients: K sw , K aw
• Volumes of compartments: V a , V w , and V s
• Assume that only the mass of the chemical in soil (m s ) is known.
(b) Use the small-world level I model (Scheringer and MacLeod, 2021) to determine
the distribution of ASM into the air, water, soil compartments in Europe. To do
this, the following parameters need to be updated within the model:
• Insert the log K ow and log K aw values from Table 10.6.
• Adjust the modeled system to the size of Europe: review external information
to set the variables for (1) total surface area [m 2 ], (2) fraction of area
covered by water, and (3) fraction of area covered by soil. If you cannot find
these values, default values that can be used are provided in the solutions.
Examine the resulting pie chart. According to the level I model, to which
compartments does ASM partition?
Level III Model
The environmental concentrations of ASM can also be estimated with a level III
model. This model type provides a more realistic estimation of the environmental
fate of a chemical by also including the dynamic exchange of materials between
compartments. In this model, the system is assumed to be in a steady-state
condition where continuous chemical input (emissions) is balanced by its output (via
degradation and advection) and all concentrations are therefore time-independent.
Similar to the level I model, the system here is composed of agricultural soil, a water
body, and the air compartment.
Task: Answer the following:
(a) Write down the first-order differential equations for the change in the mass of
a chemical with time (
dm soil
dt
= . . .) in the three compartments soil (s), water
(w), and air (a). When set to zero, these equations represent a level III model.
Include only the following processes and symbols (start by identifying the gain
and loss processes in each compartment):