Sorption of phenanthrene and atrazine by plant cuticular fractions

Abstract

Abstract-Several studies have shown selective preservation of plant cuticular materials in soils. However, very little is known about their function as sorbents for the hydrophobic organic contaminants (HOCs) in the soil. In this study, we investigated the sorption and desorption of phenanthrene and atrazine by cuticular fractions of pepper (bulk, dewaxed, nonsaponifiable, and nonhydrolyzable) to better understand the sorptive activity of cuticular matter in soils. The bulk and dewaxed cuticles exhibited carbonnormalized distribution coefficients (K oc ) for phenanthrene and atrazine in the range of that reported for soil humic substances, although both samples were rich in aliphatic structures. No hysteresis was observed in the desorption isotherms of either solute. The nonhydrolyzable residue exhibited a very high K oc value for atrazine, whereas the nonsaponifiable sample exhibited the lowest K oc value for both sorbates. Based on solubility parameter data, it is suggested that the nonsaponifiable sample be considered an intermediate between the physical and chemical mixture of pectin and cutan/lignin-like fractions, whereas the dewaxed cuticle is a chemical blending of cutin and pectin. The n-hexane-normalized sorption data suggest that the pepper cuticle can interact specifically with atrazine. This study leads to the conclusion that the contribution of aliphatic-rich plant biopolymers to the sorption of HOCs can be significant because of their preservation and accumulation in soils.

Decomposition and sorption characterization of plant cuticles in soil

“…Cutin biodegradation has been observed by Kögel-Knabner et al (1989) andStimler et al (2006). Though this process (depolymerization) does not significantly affect the amount of organic matter, the sorption capability of the system is drastically decreased due to the high sorptive capacity of the cutin (Chamel and Vitton 1996;Chefetz 2003;Chen et al 2005;Shechter et al 2006).…”

“…Because of the high polarity of the pectin, it is a more unfavorable partition medium for phenanthrene. Moreover, Chefetz (2003) has suggested that the polymeric materials pectin and cutin can best be considered an intermediate between physical and chemical mixtures. In the mixture, cutin dominates the sorption potential and the polar component (pectin) has a significant decreasing sorption effect.…”

“…Freshly picked leaves and fruits were washed several times in deionized water and then boiled in water for 60 min, after which the cuticle sheets were manually peeled. These sheets were further treated in ammonium oxalate (16 g/l) and oxalic acid (4 g/l) solution at 90°C for 24 h to remove residual fruit and leaf materials (Chefetz 2003;Kögel-Knabner et al 1994). This treatment was followed by sonication in an ultrasonic bath for 2 h. The isolated cuticles were washed in deionized water to remove excess of ammonium oxalate and oxalic acid and allowed to dry at room temperature.…”

“…In addition to the importance of plant cuticular matter as possible precursors for SOM, these and other natural aliphatic-rich materials have been recently reported as highly efficient natural sorbents for hydrophobic and polar organic compounds (Boyd et al 1990;Chefetz 2003;Chefetz et al 2000;Chen et al 2005;Kang and Xing 2005;Salloum et al 2002;Shechter et al 2006;Stimler et al 2006). In most cases, sorption of hydrophobic organic compounds (HOCs) by these sorbents, including plant cuticular materials, is in the same range or even higher than the sorption affinity values reported for aromatic-rich natural sorbents.…”

Evaluation of the phytoremediation potential of three plant species for azoxystrobin-contaminated soil

“…Azoxystrobin is a moderately hydrophobic compound (log K ow 2.64) and is likely to partially adsorb onto roots or be taken up by roots and move across cell membranes to reach the aboveground portion of plants. Also, potential uptakes of organic contamination are influenced by evapotranspiration (Chefetz 2003).…”