Correlation of the equilibrium and kinetics of leaf-air exchange of hydrophobic organic chemicals

Abstract

A simple fugacity-based model is presented describing the equilibrium and kinetics of uptake by leaves of hydrophobic organic chemicals in the vapor state from the atmosphere. A correlation is suggested for the leaf-air bioconcentration factor as a function of the chemicals' water-air and octanol-air partition coefficients and the leaf properties of air, water, and octanol-equivalent volume fractions. The octanol-air partition coefficient (which can be evaluated from the octanol-water and air-water partition coefficient) is suggested as the key partitioning descriptor for hydrophobic chemicals. A correlation for the leaf clearance rate constant is suggested in terms of two empirical leaf-specific transport parameters and the octanol-air partition coefficient.

Polycyclic aromatic hydrocarbons and their oxygenated derivatives in the urban atmosphere of Athens

“…For urban particulate material, since secondary aerosol is derived from the oxidation of fairly low molecular weight species [45], a reasonable range for MW om might be around 100-300 [39]. In our estimation, like in octanol-air partition coefficient absorption models [46,47], the assumption that organic compounds present on urban aerosols have, on average, the molecular formula of octanol (74% carbon) has been used, M om = M octanol = 130 [38,48].…”

Aerial distribution, temperature-dependent seasonal variation, and sources of polycyclic aromatic hydrocarbons in pine needles from the Houston metropolitan area, Texas, USA

“…Assuming that the partitioning of PAHs between air and lipid in pine needles is analogy to partitioning between air and octanol, atmospheric concentrations of PAHs can be estimated from the levels of PAHs in pine needles using empirically obtained bioconcentration factor (BCF) and its relationship with octanol-air partition coefficients as reported by Bacci et al [34] and Paterson et al [35] C a = C p /BCF (1) Log BCF = 0.86 Log K oa − 2.63 (2) where C a (ng/g air) and C p (ng/g dry pine needle) are PAH concentrations in the air and pine needle, BCF is bioconcentration factor (mass/mass), and K oa is dimensionless octanol-air partition coefficient. To convert mass based air concentrations (ng/g) to volume based concentrations (ng/m 3 ), air density (1,160-1,230 g/ m 3 ) at corresponding temperature was multiplied by mass based concentrations.…”

Transport, Accumulation and Transformation Processes

“…To estimate K foliage-air , the foliage can be treated as a mixture of several different phases, such as air, water, lipids, carbohydrate, cuticle, and protein (Figure 3.25). The protein and carbohydrate compartments are often neglected and K foliage-air approximated by [93]: One factor that distinguishes foliage-air partitioning from root-soil partitioning or biota-water partitioning is its strong temperature dependence. A change in the foliage temperature of 25˚C, a not atypical diurnal variation, can change K foliage-air by more than one order of magnitude [95].…”