Wednesday, 9 November 2005 - 9:55 AM
269-5

The Effect of Decomposition on Characteristics and Sorption Behavior of Aliphatic Plant Cuticular Materials.

Elizabeth J. Johnson1, Baoshan Xing1, and Benny Chefetz2. (1) University of Massachusetts, Amherst, Plant, Soil and Insect Science, 24 Stockbridge Hall, Amherst, MA 01003, (2) Hebrew University of Jerusalem, Department of Soil & Water, P.O. Box 12, Rehovot, 76100, Israel

SOM is the dominant sorbent of organic compounds, including pesticides, in soils. The aliphatic portion of SOM is often overlooked, although current studies have shown that the aliphatic moieties play an active role in SOM sorption potential. One of the primary sources of aliphatic moieties in SOM is the cuticular material derived from plants. These materials include cutin and cutan, which have been shown to persist in the soil environment, as they are highly resistant to degradation. In this study, the cuticles of tomatoes, peppers and apples were packed into nylon litter bags with 1-mm holes, placed into bins of soil in a greenhouse, and allowed to decompose for 52 weeks (tomato) or 38 weeks (pepper and apple). Throughout these decomposition periods, litter bags were removed to monitor the effects of decomposition on the cuticular material. After each litter bag harvest, cuticular fractions were isolated from the remaining undegraded cuticle: bulk cuticle, dewaxed cuticle, cuticular wax (only in the apple), unpure cutan and pure cutan. These cuticular fractions were characterized using Solid State 13C NMR, ATR, and elemental analysis, and underwent batch sorption experiments with phenanthrene. Preliminary 13C NMR and ATR results confirm that cutin and cutan do persist in the soil environment; their signature peaks are present throughout the decomposition period. The results of this experiment confirm that due to (1) the resistance of aliphatic cuticular material to degradation and (2) its high Koc values throughout the decomposition period studied, the aliphatic component of SOM cannot be overlooked as a source of organic contaminant sorption in the soil.

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