Root Uptake of Organic Contaminants into Plants: Species Differences

Xenobiotic organic contaminants are widely found in the environment, including soils, sediments, surface waters, wastewater streams, and even in drinking water. Food chain contamination resulting from the uptake of these contaminants by plants is a concern. Although the uptake of a variety of xenobiotic organic contaminants by plants has been reported but the differences between plant species are not fully understood. The emphasis of this thesis research is to further investigate the unique root to shoot transfer ability of “gold rush” zucchini that has been reported repeatedly in recent years. A pressure chamber technique was used to measure transpiration stream concentration factor (TSCF) values, a descriptor used to quantify root to shoot transfer for several organic chemicals of varying hydrophobicity in soybean “hoyt,” squash “zephyr,” and zucchini “gold rush.” Root tissue was analyzed for total carbon and lipid content. Xylem sap was analyzed for total organic carbon and protein content. The solubilities of the compounds in the xylem sap and deionized water were also determined using a modified shake flask method. The measured TSCF values showed that the uptake of hydrophobic contaminants in zucchini “gold rush” was three to tenfold greater than soybean and squash “zephyr.” The lipid content of the zucchini “gold rush” root tissue was twice that of soybean and squash “zephyr” and showed greater sorption of the hydrophobic compounds. The solubility of triclocarban in zucchini “gold rush” xylem sap was also twice that in soybean xylem sap. The enhanced solubility could be associated with the high protein content measured in zucchini “gold rush” xylem sap. The data generated in this study will be used to better understand the mechanic differences associated with the plant uptake of organic contaminants by different species. This information can also be used in the selection of the plant species used in risk assessment studies and phytoremediation studies