Bioconcentration of organic chemical vapors in plant leaves: experimental measurements and correlation

Abstract

Cr3+_28_Na^_14eluded to a large extent by the membrane, as shown by data collected when the test solution was dialyzed against distilled water (Table IV). The separation factors indicate that the transfer of species containing the solution cations does not significantly influence the transfer of N03~a cross the membrane in the acid solutions studied. The HF system behaved analogously. Summary and ConclusionsThis study investigated the chemical speciation and the dialysis behavior of concentrated acid solutions commonly used in industrial processes. A speciation model was developed that could predict measured F" concentrations with excellent accuracy (r2 = 0.94) over an ionic strength range of 0.5-6 M, a [F~] range of ^-"1 M, and in varied solution species matrices. An important component of that model was the calculation of the liquid junction potential, which must be taken into account if electrodes that have liquid junctions are used for collecting data in these systems.Based on the chemical speciation model results, transfer rates of acid are related via Fick's law to differences across the membrane in the HN03 or HF concentrations. Attempts to correlate the transfer rates to the concentration gradients of individual ionic species (e.g., H+, F~, or N03") were unsuccessful, indicating that the neutral acid species are the ones controlling transport through the membrane.Conventional wisdom has it that the type and number of charged groups in the membrane are critical variables that must be considered in evaluating the performance of ion-exchange membranes. It seems likely that membrane charge does affect the diffusion coefficients of individual species and hence the separation factors among species.However, once those coefficients are established, the performance of at least the membrane investigated can be interpreted on the basis of passive diffusion, without considering possible specific interactions between the ion-exchange sites in the membrane and the diffusing species. In other words, interactions in the membrane may affect the numerical values of the diffusion coefficients, but they do not require any change in the fundamental analysis.The products [H+] [N03~] and [H+][F~] are linearly related to [HN03] and [HF], respectively, via their stability constants, and with the appropriate transfer coefficients these products can also be used to model the experimental data in the framework of Donnan equilibrium.

Uptake of trifluralin and lindane from water by ryegrass

“…Many plant uptake studies have dealt with or assumed the metabolism-free (quasi-) equilibrium conditions (Briggs et al, 1982;Bacci et al, 1990a). From the facts that the plant uptake of organic compounds usually does not reach true equilibrium and organic compounds are often partially metabolized or lost, it is necessary to study the kinetics of plant uptake including metabolism, formation of bound residues and any other losses, and to develop a method to estimate concentration factors under both thermodynamic equilibrium and steady state conditions.…”

DDT residues in the environment—A review with a New Zealand perspective

“…Atmospheric pollutant levels may also be estimated by measuring their content in plant leaves, if pollutants are assumed to be partitioned into cuticular waxes rather than translocated to the foliage (Eriksson et al 1989;Bacci et al 1990). Gaggi et al (1985) have considered DDT residues in a number of woody plant and lichen species, reporting the results of a world-wide survey of foliage samples collected in 1984-85.…”

Effects of exposure time and co-existing organic compounds on uptake of atrazine from nutrient solution by rice seedlings (Oryza sativa L.)

“…In plant uptake of organic chemicals from water, many assumed that the concentrations in roots and water reach equilibrium after a certain root-exposure time [4,16]. However, the equilibrium state has not always been confirmed by an unequivocal criterion.…”