Israeli-U.S. Study Looks at Natural Pollutant Absorbents in Plants

A new study closely examines the role degrading plant materials play in absorbing organic pollutants in the soil. These “biopolymers” are the waxy, water resistant barriers between the plant cells and the environment. This information is important to evaluate the role of these biopolymers as a natural sorbent for organic pollutants in the environment.

The study, reported in the July/August 2010 edition of the Soil Science Society of America Journal, found that the 30-35 percent of the polymers decomposed after 20 months of incubation. There are two types of polymer; cutin, providing structural framework, as well as cutan, which increases the plant’s resistance to water. Cutin’s role as a natural absorbent decreases as it decomposes. Cutan, in contrast, continued to act as a natural, highly efficient sorbent for organic compounds in soil. The journal is published by the Soil Science Society of America.

Previous studies of plants suggest that because of cutan’s highly crystalline structure, it was resistant to degradation. The findings of this study suggest that cutan is actually a mix of rigid and amorphous structure, rather than pure crystalline carbon.

A plant’s cutin was generally found to degrade into humus, or organic material, suggesting it is a critical component to natural leaf litter. The researchers concluded that of the two, cutan is more likely to perform as an absorbent in the soil.

The research was conducted by soil and environmental chemists from Hebrew University of Jerusalem and the University of Massachusetts. A marked difference from previous studies, the researchers performed their research on purified polymers, absent of the whole leaf and other residues. Thus, rates of decomposition were lower than previously reported.

“Sorption interactions have significant effects on the fate and behavior of organic compounds in the environment,” said Benny Chefetz, Hebrew University, who conducted the study. “In order to be able to predict the sorption-desorption behavior of compounds in soils, the level and composition of the natural [plant cutin/cutan] components of soil organic matter must be evaluated. These soil organic matter structures cannot be ignored as natural sorbents in soils and sediments.”

The project was funded by The United States–Israeli Binational Agricultural Research and Development Fund, and presented at the 15th Meeting of the International Humic Substances Society in June 2010.

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