| Nonylphenol (NP) and other hydrophobic biodegradation intermediates of nonylphenol ethoxylate (NPE) surfactants have been identified in wastewater treatment biosolids. These biosolids are often land applied. Hydroponic experiments were conducted to examine the uptake and translocation of NP, NPE4, and NPE9 by crested wheatgrass (Agropyron cristatum). The uptake of phenol was also evaluated for comparison.; Plants were exposed to NP, NPE4, NPE9, or phenol (14C and unlabeled) for 11–14 weeks. Plant tissue was analyzed for 14C and for the parent compounds. Rhizosphere mineralization was quantified via 14CO2 production. The majority of the plant-associated 14C was in the roots (NP = 98%, NPE4 = 92% and NPE9 = 81%). Carbon-14 concentrations in the foliar tissue ranged from 2.0 × 10−6 to 4.5 × 10−5 mg-equivalent per g (dry weight) but no parent compounds were detected, implying that the 14C was transformed or unextractable. Little mineralization was observed for NP, NPE 4, and NPE9; however, for phenol 11–21% of the added 14C was mineralized. Experiments also showed that root desorption was restricted, either kinetically or by increased binding. The results demonstrate that root-to-shoot transfer of these contaminants is small and the association with roots may reduce the mobility of these contaminants in the presence of plants. |
