A simple pre-factor for contaminant biodegradation potential and its application to pesticides risk assessment

In this study, we extend our earlier work presented in the 22nd International Congress on Modelling and Simulation (MODSIM 2017) and propose a simple parametric pre-factor (the biodegradation potential ψ_B), which can be used to estimate the biodegraded fraction of a contaminant in soil. ψ_B can be determined based on either first-order or Michaelis-Menten-Monod (MMM) kinetics. We show the application in the environmental risk assessments of the herbicides atrazine (ATZ) and glyphosate (GLP). We compare the ATZ and GLP biodegraded fractions estimated with ψ_B against those predicted with bioreactive models accounting for more comprehensive ATZ and GLP biodegradation reaction networks. Our analyses show that ψ_B matched relativity well the biodegraded fraction predicted by the mechanistic model, with ψ_B calculated using the MMM framework providing a more accurate result. We conclude that ψ_B can be used to scale the predicted environmental concentration of a contaminant to account for its biodegradation potential in simplistic transport models.