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ABSTRACT: 4-Nonylphenols (4-NPs) are known endocrine disruptors and by-products of the microbial degradation of nonylphenol polyethoxylate surfactants. One of the challenges to understanding the toxic effects of nonylphenols is the large number of isomers that may exist in environmental samples. In order to attribute toxic effects to specific compounds, a method is needed for the separation and quantitation of individual nonylphenol isomers. The pre-concentration methods of solvent sublimation, solid-phase extraction or liquid-liquid extraction prior to chromatographic analysis can be problematic because of co-extraction of thousands of compounds typically found in complex matrices such as municipal wastewater or landfill leachate. In the present study, steam distillation extraction (SDE) was found to be an effective pre-concentration method for extraction of 4-NPs from leachate and wastewater, and comprehensive two-dimensional gas chromatography (GC×GC) coupled with fast mass spectral data acquisition by time-of-flight mass spectrometry (ToFMS) enhanced the resolution and identification of 4-NP isomers. Concentrations of eight 4-NP isomers were determined in leachate from landfill cells of different age and wastewater influent and effluent samples. 4-NP isomers were about 3 times more abundant in leachate from the younger cell than the older one, whereas concentrations in wastewater effluent were either below detection limits or <1% of influent concentrations. 4-NP isomer distribution patterns were found to have been altered following release to the environment. This is believed to reflect isomer-specific degradation and accumulation of 4-NPs in the aquatic environment.
Journal of chromatography. A 03/2012; 1230:110-6. · 4.19 Impact Factor
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ABSTRACT: A new Vis-Fe(0)-H(2)O(2)-citrate-O(2) system comprising zero-valent iron, hydrogen peroxide, citrate anion and aeration at circumneutral pH under visible irradiation was studied. 21 μmol L(-1) of Rhodamine B (RhB) was chosen as the substrate to be tested. Experiments were conducted under conditions of 2.9 mmol L(-1) of H(2)O(2), 12.6g of Fe(0) and 1.0 mmol L(-1) of citrate at pH 7.5. Results showed that, in 1h reaction, 54% of RhB was removed with corresponding 26% of COD reduced. Meanwhile, the amount of released dissolved irons from Fe(0) surface was found to be at a very low level as <5.4 μmol L(-1). Extinguishing tests with isopropanol suggested that RhB oxidation by hydroxyl radicals was the main process taken place in Vis-Fe(0)-H(2)O(2)-citrate-O(2) system, which accounted for 75% of substrate removal in 3h reaction. Control and factor influencing experiments showed that the prohibitive extents of individual factor importance on RhB removal followed a decreasing order of Fe(0)>H(2)O(2)>citrate>Vis>O(2). This study showed an excellent system that could remove refractory organic compounds from water in laboratory researches, and also provided a good idea to reduce secondary contamination by dissolved irons in future investigations.
Chemosphere 06/2011; 84(11):1542-7. · 3.21 Impact Factor
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ABSTRACT: The sterol content of leachate from two different landfills (labeled as landfill J and landfill R, respectively) at Wuhan, central China was examined by GC/MS. About 20 types of sterols were identified according to their mass spectra of TMS (trimethylsilyl derivates) ethers and their eluting orders. Three types of indices of sterols, namely the ratio of 5beta/(5beta+5alpha) stanol, the ratio of coprostanol/epicoprostanol and the ratio of coprostanol/cholesterol, were used to assess and cross-validate sterol sources. The results showed that landfill R suffered faecal pollution while there are complex sterol sources in landfill J. The ratios of cholesterol/(chloesterol+cholestanol) were 0.24 in landfill R and 0.32 in landfill J, indicating cholesterol reduction in both landfills. C29 sterols consisted of 58% of total sterols in landfill J leachate. The sources for the landfill leachate included not only allochthonous domestic wastes, but biodegradation products of autochthonous wastes in the landfills.
Journal of Chromatography B 09/2008; 874(1-2):1-6. · 2.89 Impact Factor
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ABSTRACT: Dissolved organic macromolecules (DOM) and micropollutants, such as phthalic acid esters (PAEs), are often enriched in landfill leachate. PAEs were detected in 10 leachate samples from three landfills in Hubei province, central China. In particular, di-(2-ethyhexyl) phthalate (DEHP) concentration was higher than 70microgL(-1) in most samples, and the highest DEHP concentration was in the colloid fraction (1000Da-0.45microm). Use of flocculants may result in flocculation and precipitation of colloids and associated contaminants, such as DEHP. Biodegradation is not effective for long chain PAEs or the landfill leachate, given the low ratio of BOD5/COD (less than 0.2) and deficient phosphorus content. Complexation-flocculation is therefore proposed as an alternative process for removing DOM and PAEs. Jar-test experiments were employed to investigate the mechanism and feasibility of the process. Among tested coagulants (ferric chloride, aluminum sulfate and poly aluminum chloride (PAC)), PAC was the most efficient. Hydrophobic contaminants with log KOC greater than 4 and DOM in wastewater can be removed simultaneously through the complexation-flocculation process.
Waste Management 05/2008; 29(1):110-6. · 2.43 Impact Factor
