(K_ow (based) Aquatic BioAccumulation Model)

• F.1 Bioconcentration
• F.2 Bioaccumulation
• F.3 Biomagnification

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Appendix F. Description of Equations Used to Calculate the BCF, BAF, BMF, and BSAF Values

Bioconcentration, bioaccumulation, and biomagnification factors are calculated in the "results" worksheet of the KABAM tool using data from the "parameters & calculations" worksheet. The equations for these calculations are described below.

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• F.1 Bioconcentration

  Bioconcentration is a measure of the amount of pesticide residue in an organism's tissue relative to the concentration in the organism's environment (USEPA 2008c). This includes pesticide uptake through respiration and contact, not through dietary sources. Bioconcentration factors (BCFs) are calculated by considering pesticide tissue concentrations with respect to environmental pesticide concentrations. BCF values > 1 indicate that the concentration in the organism is greater than that of the medium (e.g., soil or water) from which the pesticide was taken. BCFs can be calculated on a total organism basis or normalized to the lipid content of the organism.

  KABAM calculates the total (body weight) BCFs of a chemical for each aquatic organism according to Equation F1 (USEPA 2003). C_BCF is calculated using equation A1 (see Table A.1 of Appendix A for a full description) where C_B = C_BCF, when k_D = k_E = k_M = k_G = 0. The units of total BCF values are expressed as: (µg pesticide/kg wet weight)/(µg pesticide/L water). Total BCF values account for the total amount of the pesticide in the water (i.e., C_WTO).

  Equation F1

  Total BCF = C_BCF / C_WTO

  Equation A1

  C_B = [k₁ * (m₀ * Φ * C_WTO + m_P * C_WDP) + k_D *Σ (P_i * C_Di)] / (k₂ + k_E + k_G + k_M)

  KABAM also calculates the lipid-normalized BCFs of a chemical for each aquatic organism according to Equation F2 (USEPA 2003). The units of lipid normalized BCF values are expressed as: (µg pesticide/kg lipid)/(µg pesticide/L water). V_LB represents the fraction of lipid in the body of the organism for which the BCF is being derived. Lipid normalized BCF values account for the pesticide concentration that is freely dissolved in the water (i.e., C_WTO * Φ).

  Equation F2

  Lipid normalized BCF = (C_BCF / V_LB) / (C_WTO * Φ)

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• F.2 Bioaccumulation

  Bioaccumulation is the net uptake of a pesticide from the environment by all possible routes (e.g., respiration, diet, dermal) from any source (e.g., water, sediment, and other organisms) (Spacie et al. 1995). Bioaccumulation factors (BAF) are calculated by considering pesticide tissue concentrations with respect to environmental pesticide concentrations. BAF values > 1 indicate that the accumulation in the organism is greater than that of the medium (e.g., soil or water) from which the pesticide was taken. These factors can be calculated on a total organism basis or normalized to the lipid content of the organism.

  KABAM calculates the total BAFs of a chemical for each aquatic organism according to Equation F3 (USEPA 2003). The units of total BAF values are expressed as: (µg pesticide/kg wet weight)/(µg pesticide/L water). C_B is calculated according to Equation A1. Total BAF values account for the total amount of the pesticide in the water (i.e., C_WTO).

  Equation F3

  Total BAF = C_B / C_WTO

  Lipid-normalized BAFs of a chemical are calculated for each aquatic organism according to Equation F4 (USEPA 2003). The units of lipid normalized BAF values are expressed as: (µg pesticide/kg lipid)/(µg pesticide/L water). The variable C_B is calculated according to Equation A1. The variable V_LB represents the fraction of lipid in the body of the organism for which the BCF is being derived. Lipid normalized BAF values account for the pesticide concentration that is freely dissolved in the water (i.e., C_WTO*Φ).

  Equation F4

  Lipid normalized BAF = (C_B / V_LB) / (C_WTO * Φ)

  Accumulation factors are also derived by considering pesticide tissue concentrations with respect to pesticide concentrations in sediment. Biota-sediment accumulation factors (BSAFs) are calculated by dividing the lipid normalized concentration of a chemical in an organism by the chemical concentration in the sediment (dry weight), normalized to the organic carbon content of the sediment (Equation F5) (USEPA 2003). The variable C_SOC represents the pesticide concentration in the sediment, normalized to the organic carbon content of the sediment (units of g/kg OC).

  Equation F5

  BSAF = (C_B / V_LB) / C_SOC

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• F.3 Biomagnification

  Biomagnification is the increase of a pesticide concentration in the tissue of an organism compared to the tissue concentrations of its prey (USEPA 2008b). Biomagnification factors (BMFs) are calculated by considering lipid normalized pesticide tissue concentrations within an organism with respect to the lipid normalized concentrations of that pesticide in the prey of the organism. Factors > 1 indicate the occurrence of biomagnification.

  KABAM calculates the BMFs of a chemical for each aquatic organism according to Equation F6 (USEPA 2003). The units of BMF values are expressed as: (µg pesticide/kg lipid)/(µg pesticide/kg lipid). The variable C_B is calculated according to Equation A1. V_LB represents the fraction of lipid in the body of the organism for which the BMF is being derived. P_i represents the fraction of diet containing prey item i. C_Di represents the concentration of the pesticide in prey item i and V_LBi represents the fraction of lipid in the body of the prey item i. It should be noted that although KABAM allows aquatic organisms to consume sediment, uptake of pesticide through consumption of sediment is not considered in the calculation of BMFs in the model tool.

  Equation F6

  BMF = (C_B / V_LB) / ∑[(P_i * C_Di) / V_LBi]

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