Toxicokinetics and biotransformation of p-nitrophenol in red abalone (Haliotis rufescens)

Nitration processes of acetaminophen in nitrifying activated sludge

This work is an attempt to elucidate the quantitative significance of acetaminophen (APAP) nitration in nitrifying activated sludge and to propose a reaction mechanism for this process. The link between nitrification and nitration of APAP was investigated at different scales. Results from field studies showed the occurrence of 3-nitro-APAP and to a lesser extent 3-chloro-5-nitro-APAP at concentration levels in the 50-300 ng/L range in effluents of a full scale wastewater treatment plant (WWTP) operated with nitrogen removal, whereas 3-hydroxy-APAP was eliminated after the nitrification step. Batch experiments with nitrifying activated sludge confirmed APAP transformation by nitration and suggested that nitrifying bacteria may play a role in this transformation process through the release of reactive nitrogen species. In vitro assays provided evidence that nitration through the production of nitrous acid is a very unlikely pathway. In contrast, nitric oxide (*NO) produced by nitrifying bacteria is probably involved in APAP nitration through the formation of peroxynitrite in presence of superoxide anion. The production of 3-nitro-APAP would only account for a few percents of the total transformation rate of APAP in WWTPs. The production of nitrated derivatives is highly relevant because of the potential ecotoxicological risks of these compounds.

Adsorption of p-nitrophenol on activated carbon fixed-bed

Carbon fixed-beds are usually used to remove organic contaminants. Adsorption in a carbon filter is a dynamic, non-steady process which is not yet completely understood. The objective of this paper is to establish a methodology to simplify the study of this process based on the wave theory, rapid small-scale column test and experimental design/surface response analysis. The constant pattern wave hypothesis was confirmed by the experimental data. The influence of the inlet concentration of p-nitrophenol and the flow rate on dynamic adsorption was studied at 20 degrees C following a central composite design using a second-order model. Both parameters have an important influence on the response variables studied. The methodology used is a useful tool for studying the dynamic process and shows interactions that are difficult to verify by the classical step-by-step method.

Toxicokinetics and biotransformation of p-nitrophenol in white sturgeon (Acipenser transmontanus)

White sturgeon (Acipencer transmontanus) were exposed to 7.2 microM (1.0 ppm) 14C-labeled p-nitrophenol (PNP) in brackish water for 24 h and then allowed to depurate in clean brackish water for another 24h. Absorption, conditional uptake clearance, and conditional elimination rate constants were 0.08+/-0.04 h(-1), 8.1+/-3.6 mL g(-1) h(-1), and 0.46+/-0.21 h(-1), respectively. A whole-organism total concentration factor of 18.7+/-2.6 was determined from equilibrium tissue and water concentrations. Sturgeon depurated 89.4% of absorbed PNP within 24h, of which 53.0+/-8.3% was unmetabolized parent compound, 9.6+/-3.6% was p-nitrophenyl-beta-d-glucuronide, and 39.1+/-8.3% was p-nitrophenylsulfate.