173 research outputs found
Distribution of perfluorinated compounds in Lake Taihu (China): Impact to human health and water standards
The distribution in water and sediment, the sources/sinks and the risk of perfluorinated compounds (PFCs) in Lake Taihu, China were investigated. The total PFCs concentration was 164 to 299 ng L− 1 in water and 5.8 to 35 ng g− 1 (dw) in sediment. The highest concentrations of perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) in water were 29.2 ng L− 1 and 136 ng L− 1. PFOS was largely associated with sediment, whereas short chain PFCs predominated in water. The partition coefficient (Kd) was positively correlated with the organic carbon fraction (ƒoc) for PFOS but not for the other PFCs. The organic carbon normalized partition coefficient (Koc) increased by 0.51 log units for each additional CF2 moiety from perfluoro-butanesulfonate (PFBS) to PFOS. For the same chain length but different functional groups, the log Koc of PFOS was 1.35 units higher than PFOA. PFOS exhibited the highest affinity for sediment through the partition mechanism, and ƒoc affected the sediment as a sink of PFOS. Although there was no immediate health impact by the intake of the water alone, the consumption of aquatic products may cause potential health risks for animals/humans on the time scale of months to years. The relationship between the concentration, water-sediment distribution, bioaccumulation and toxicity should be considered in determining the water standards of PFCs
The effectiveness of sewage treatment processes to remove faecal pathogens and antibiotic residues
Pathogens and antibiotics enter the aquatic environment via sewage effluents and may pose a health risk to wild life and humans. The aim of this study was to determine the levels of faecal bacteria, and selected antibiotic residues in raw wastewater and treated sewage effluents from three different sewage treatment plants in the Western Cape, South Africa. Sewage treatment plant 1 and 2 use older technologies, while sewage treatment plant 3 has been upgraded and membrane technologies were incorporated in the treatment processes. Coliforms and Escherichia coli (E. coli) were used as bioindicators for faecal bacteria. A chromogenic test was used to screen for coliforms and E. coli. Fluoroquinolones and sulfamethoxazole are commonly used antibiotics and were selected to monitor the efficiency of sewage treatment processes for antibiotic removal. Enzyme Linked Immunosorbent Assays (ELISAs) were used to quantitate antibiotic residues in raw and treated sewage. Raw intake water at all treatment plants contained total coliforms and E. coli. High removal of E. coli by treatment processes was evident for treatment plant 2 and 3 only. Fluoroquinolones and sulfamethoxazole were detected in raw wastewater from all sewage treatment plants. Treatment processes at plant 1 did not reduce the fluoroquinolone concentration in treated sewage effluents. Treatment processes at plant 2 and 3 reduced the fluoroquinolone concentration by 21% and 31%, respectively. Treatment processes at plant 1 did not reduce the sulfamethoxazole concentration in treated sewage effluents. Treatment processes at plant 2 and 3 reduced sulfamethoxazole by 34% and 56%, respectively. This study showed that bacteria and antibiotic residues are still discharged into the environment. Further research needs to be undertaken to improve sewage treatment technologies, thereby producing a better quality treated sewage effluent
Kinetics of Rapid Covalent Bond Formation of Aniline with Humic Acid: ESR Investigations with Nitroxide Spin Labels
Levels, distributions and sources of veterinary antibiotics in the sediments of the Bohai Sea in China and surrounding estuaries
Chemical oxidation of dissolved organic matter by chlorine dioxide, chlorine, and ozone:Effects on its optical and antioxidant properties
Remoção de fármacos e desreguladores endócrinos em estações de tratamento de esgoto: revisão da literatura
Scientific Opinion about the Guidance of the Chemical Regulation Directorate (UK) on how aged sorption studies for pesticides should be conducted, analysed and used in regulatory assessments
Reactions of a Sulfonamide Antimicrobial with Model Humic Constituents: Assessing Pathways and Stability of Covalent Bonding
The mechanism of covalent bond formation of the model
sulfonamide
sulfathiazole (STZ) and the stronger nucleophile <i>para</i>-ethoxyaniline was studied in reactions with model humic acid constituents
(quinones and other carbonyl compounds) in the absence and presence
of laccase. As revealed by high resolution mass spectrometry, the
initial bonding of STZ occurred by 1,2- and 1,4-nucleophilic additions
of the aromatic amino group to quinones resulting in imine and anilinoquinone
formation, respectively. Experiments using the radical scavenger <i>tert</i>-butyl-alcohol provided the same products and similar
formation rates as those without scavenger indicating that probably
not radical coupling reactions were responsible for the initial covalent
bond formation. No addition with nonquinone carbonyl compounds occurred
within 76 days except for a slow 1,4-addition to the β-unsaturated
carbonyl 1-penten-3-one. The stability of covalent bonds against desorption
and pressurized liquid extraction (PLE) was assessed. The recovery
rates showed no systematic differences in STZ extractability between
the two product types. This suggests that the strength of bonding
is not controlled by the initial type of bond, but by the extent of
subsequent incorporation of the reaction product into the formed polymer.
This incorporation was monitored for <sup>15</sup>N aniline by <sup>1</sup>H–<sup>15</sup>N HMBC NMR spectroscopy. The initial
1,2- and 1,4-addition bonds were replaced by stronger heterocyclic
forms with increasing incubation time. These processes could also
hold true for soils, and a slow nonextractable residue formation with
time could be related to a slow increase of the amount of covalently
bound sulfonamide and the strength of bonding
Covalent Binding of Sulfamethazine to Natural and Synthetic Humic Acids: Assessing Laccase Catalysis and Covalent Bond Stability
Sulfonamide antibiotics form stable
covalent bonds with quinone
moieties in organic matter via nucleophilic addition reactions. In
this work, we combined analytical electrochemistry with trace analytics
to assess the catalytic role of the oxidoreductase laccase in the
binding of sulfamethazine (SMZ) to Leonardite humic acid (LHA) and
to four synthetic humic acids (SHAs) polymerized from low molecular
weight precursors and to determine the stability of the formed bonds.
In the absence of laccase, a significant portion of the added SMZ
formed covalent bonds with LHA, but only a very small fraction (<0.4%)
of the total quinone moieties in LHA reacted. Increasing absolute,
but decreasing relative concentrations of SMZ–LHA covalent
bonds with increasing initial SMZ concentration suggested that the
quinone moieties in LHA covered a wide distribution in reactivity
for the nucleophilic addition of SMZ. Laccase catalyzed the formation
of covalent bonds by oxidizing unreactive hydroquinone moieties in
LHA to reactive, electrophilic quinone moieties, of which a large
fraction (5%) reacted with SMZ. Compared to LHA, the SHA showed enhanced
covalent bond formation in the absence of laccase, suggesting a higher
reactivity of their quinone moieties toward nucleophilic addition.
This work supports that binding to soil organic matter (SOM) is an
important process governing the fate, bioactivity, and extractability
of sulfonamides in soils
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