Predicting plant uptake of organic chemicals from soil or air using octanol/water and octanol/air partition ratios and a molecular connectivity index

A bioconcentration ratio (BCR) represents the ratio of the concentration of a chemical found in an exposed biological system, such as a plant or fish, to the concentration in the exposure medium (water, soil, or air). A comparison is made of the precision and accuracy of the molecular connectivity index (MCI) and the octanol/water partition coefficient ( K ow ) as predictors of BCRs from the soil matrix into above‐ or below‐ground vegetation tissues. Calculated octanol/air partition coefficient ( K oa ) values are compared with calculated K ow and MCI values as predictors of measured air‐to‐plant BCRs. Based on a statistical evaluation of explained variance, residual error, and cross‐validation, this evaluation reveals that the MCI provides higher precision, greater ease of use, and a more cost‐effective method for predicting the potential bioconcentration of a chemical from soil into above‐ground vegetation. Statistical analyses of the various methods reveal that both the K ow and MCI approaches have a similar level of precision for predicting BCRs from soil solution into roots and, among MCI, K oa and K ow ; K oa is somewhat more precise and valid than MCI and K ow for estimating uptake, but all have limited accuracy as bioconcentration predictors. These latter results are derived mainly from the paucity of both reliable K oa values and measured air‐to‐plant BCRs and indicate a need for more experimental measurements from which more accurate models may be developed.