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TA7 Alkylphenols and Alkylphenol Ethoxylates
(224) Fate of nonylphenol and nonylphenol ethoxylates in hydroponic and biosolid/soil systems planted with crested wheatgrass.
Wheeler, B1, Doucette, W2, Chard, J3, Sims, R4, Carbone, J5, 1 Utah State University, Logan, UT, USA2 Utah State University, Logan, UT, USA3 Utah State University, Logan, UT, USA4 Utah State University, Logan, UT, USA5 Rohm and Haas Company, Spring House, PA, USA
ABSTRACT- Nonylphenol ethoxylate (NPE) surfactants and associated biodegradation intermediates such as nonylphenol (NP) have been identified in wastewater treatment plant biosolids. These biosolids are often land applied but little is known about the potential fate of these compounds in biosolid/soil systems especially in the presence of plants. Initially, a series of hydroponic studies were preformed to evaluate the potential uptake and translocation of 14C-labeled NP, NPE4, and NPE9 by crested wheat grass. The fate of 14C-phenol, a structurally similar but much less hydrophobic compound, was also evaluated for comparison. Plants were exposed to a constant aqueous concentration of NP, NPE or phenol for 11-14 weeks. Samples of shoots and roots were separately collected and analyzed by combustion/liquid scintillation counting to determine the distribution of 14C. The plant tissue concentrations, volumes of water transpired and root-zone concentrations were also used to calculate transpiration stream concentration factors (TSCFs) for subsequent plant uptake modeling. At the end of the 14-week experiments, the majority of the 14C associated with the plants was found in the roots for NP (98%), NPE4 (92%) and NPE9 (81%). While transfer into the shoots was relatively small for all three compounds, the extent of transfer was inversely proportional to the compounds hydrophobicity as expressed by log Kow. Little or no mineralization was observed for NP, NPE4 and NPE9 during the 14 week hydroponic studies. However for phenol, significant mineralization within the root zone (11-21% added 14C) was observed which likely impacted the extent of plant uptake. Similar uptake and degradation experiments are being conducted using sludge soil systems planted with crested wheatgrass.
Key words: alkylphenol ethoxylates, plant uptake, bioaccumulation, land application
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