Estimating Grass–Soil Bioconcentration of Munitions Compounds from Molecular Structure

A partitioning–based
model is presented to estimate the
bioconcentration of five munitions compounds and two munition–like
compounds in grasses. The model uses polyparameter linear free energy
relationships (pp–LFERs) to estimate the partition coefficients
between soil organic carbon and interstitial water and between interstitial
water and the plant cuticle, a lipid–like plant component.
Inputs for the pp–LFERs are a set of numerical descriptors
computed from molecular structure only that characterize the molecular
properties that determine the interaction with soil organic carbon,
interstitial water, and plant cuticle. The model is validated by predicting
concentrations measured in the whole plant during independent uptake
experiments with a root-mean-square error (log predicted plant concentration–log
observed plant concentration) of 0.429. This highlights the dominant
role of partitioning between the exposure medium and the plant cuticle
in the bioconcentration of these compounds. The pp–LFERs can
be used to assess the environmental risk of munitions compounds and
munition–like compounds using only their molecular structure
as input.