A lot of attention has been given recently to developing fugacity-based, multi-compartment models  for the bioconcentration of volatile organic chemicals in vegitation. The basic approach was first developed by Riederer (Environ. Sci. Technol., 1990, 24, 829-837). Polder et al (Environ. Toxicol. Chem., 1998, 17, 962-968), in a literature study, compared Riederer’s model with a simple one-compartment model suggested by  Trapp and Mattheis (Environ.Sci.Technol., 1995, 29, 2333-2338).   The Trapp-Mattheis model is implemented in the European Union Uniform System for the Evaluation of Substances (EUSES).  For herbaceous plants, both models gave acceptable results. 

Haitt (Anal. Chem., 1998, 70, 851-856), working with eight different plant species, obtained satisfactory results with all plant species using a four-compartment model; air, water, lipid and terpenoid compartments.  Haitt recommends using:

where:

                BCF = bioconcentration factor

                V_a = volume fraction of air in plant leaf

                V_w = volume fraction of water in plant leaf

                K_aw = air-water (Henry’s law) partition coefficient

                V_l = volume fraction of lipid in plant leaf

                K_oa = octanol-air partition coefficient  = K_ow/K_aw

                K_ow = octanol-water partition coefficient

V_t =  volume fraction of terpenoid in plant leaf

                K_ta = terpenoid-air partition coefficient

Typically, V_a = 0.19, V_w = 0.7, and V_l =0.05.  Haitt suggests that PK_oa can be substituted for V_tK_ta in the above relationship, where P is the product of V_t and the ratio of the chemical’s activity in octanol and in terpenoid phase.  The average value of P ranged from 6 in juniper to 0.08 in grass.