Mineralization and Plant Uptake of 14C-Labeled Nonylphenol, Nonylphenol Tetraethoxylate, and Nonylphenol Nonylethoxylate In Biosolids/Soil Systems Planted with Crested Wheatgrass

Microcosm experiments (duration, 150 d) were conducted to evaluate the mineralization and plant uptake of [14C]nonylphenol (NP), [14C]nonylphenol tetraethoxylate (NPE4), and [14C]nonylphenol nonylethoxylate (NPE9) in a soil/biosolids (99.5:0.5 w/w) environment planted with crested wheatgrass (Agropyron cristatum). Three initial nominal concentrations (6, 24, and 47 mg/kg dry wt) each of NP, NPE4, and NPE9 were examined along with unplanted and unplanted poisoned controls. Phenol (22 mg/kg) also was evaluated as a more degradable reference compound. The biosolids were obtained from a municipal treatment plant, and the loamy sand soil was freshly collected. Mineralization ranged from 7% for NP to 53% for phenol, and no enhancement was observed in the planted systems. For NP, NPE4, and NPE9, 14C foliar tissues concentrations were proportional to exposure concentrations but were 10-fold lower than the root concentrations and two- to threefold lower than the soil concentrations. Bioconcentration factors (BCFs) based on 14C measurements ranged from 0.31 (mg compound/kg dry plant/ mg compound/kg dry soil) for systems spiked with NP to 0.52 for systems spiked with NPE9. Results of the NP analysis (initial concentration, 47 mg/ kg) showed a 90% decrease in the soil concentration and an average BCF of 1.0. The lower BCF calculated from the 14C analysis likely resulted from the presence of NP transformation products in the soil that are less available or are translocated by the plants but quantified by the combustion/liquid scintillation counting procedure

Accumulation of polar compounds in leaves and fruits – questioning the suitability of widely used TSCF–log Kow regressions

Although the specific mechanisms are not completely understood, plant uptake of most xenobiotic organic compounds is believed to be a passive process related at least in part to the lipophilicity of the compound. The transpiration stream concentration factor (TSCF), a ratio of xylem to root-zone solution concentrations, is one of the most widely used descriptors in plant uptake modeling. Unfortunately, experimentally determined TSCF values are extremely limited and TSCF used in modeling efforts are often estimated from empirically derived bell-shaped curves that relate TSCF to the log octanol/water partition coefficient (Kow). The shape of the curve implies that there is an optimallipophilicity for uptake and translocation and compounds that are highly polar are not expected to be significantly translocated.However, recent experimentaluptake data generated for highly water-soluble and water miscible compounds(e.g.. sulfolane, 1,4- dioxane, MTBE) suggest that this relationship may not be appropriate. An alternative TSCF-log Kow relationship in combination with a refined model for predicting uptake and accumulation in edible fruits