The characterisation of a laboratory quality control material (QCM) for dibutyltin (DBT) and tributyltin (TBT) in sewage sludge is described. For this purpose the extraction procedure was optimized by the use of different extraction methods were tested (microwave- and ultrasound-assisted extraction and mechanical stirring). The reference values were determined by the use GC-ID-ICP-MS. The QCM will be used for an intercomparison study on DBT and TBT in sewage sludge, and as a day-to-day QCM during studies of the transformation of OTC in sewage sludge.
COBISS.SI-ID: 25672231
The input of wastewater treatment plants (WWTPs) may contain high concentrations of Cr(III) and Cr(VI), which can affect nitrogen removal. In the present study the influence of different Cr(III) and Cr(VI) concentrations towards activated sludge nitrification was studied. To better understand the mechanisms of Cr(VI) toxicity, its reduction, adsorption and uptake in activated sludge was investigated in a batch growth system. Quantification of Cr(VI) was performed by speciated isotope dilution inductively coupled plasma mass spectrometry. It was found that Cr(VI) concentrations above 1.0 mg L-1 and Cr(III) concentrations higher than 50 mg L-1 negatively affected nitrification. Speciation studies indicated almost complete reduction of Cr(VI) after 24 hours of incubation when Cr(VI) concentrations were lower than 2.5 mg L-1, whereas for Cr(VI) added to 5 mg L-1 around 40 % remained unreduced. The study of the partitioning of Cr in the activated sludge was performed by the addition of Cr(VI) in concentrations of 2.5 and 5.0 mg L-1. Results revealed that Cr was allocated mainly within the intercellular compartments, whereas intracellular and adsorbed Cr represented less than 0.1 % of the Cr sludge concentrations. Cr(VI) was reduced in all compartments, the most efficiently (about 94 %) within the intracellular and intercellular fractions. The extent of reduction of adsorbed Cr was 92 and 80 % for 2.5 and 5.0 mg of Cr(VI) L-1, respectively. The results of present investigation provide a new insight into the toxicity of Cr species towards activated sludge nitrification, which is of significant importance for the management of WWTPs in order to prevent them from inflows containing harmful Cr(VI) concentrations.
COBISS.SI-ID: 27432487
Described is a procedure for synthesis of 117Sn tributil butyltin. Synthesis starts with bromination of metallic Sn, followed by butylation with butyl lithium. The formed tetrabutyltin (SnBu4) was transformed to tributyltin chloride (TBTCl) using concentrated hydrochloric acid (HCl). The purity of synthesized TBT was verified by the speciation analysis using gas chromatography coupled to inductively coupled plasma mass spectrometry (GC-ICP-MS) and nuclear magnetic resonance (NMR) techniques. Data revealed that TBT has a purity of more than 93 %. The remaining 7 % corresponded to DBT. TBT was quantified by reverse isotope dilution GC-ICP-MS. The synthesis yield was better than 60 % and the stability of product more than 6 months.
COBISS.SI-ID: 27435559
Landfill leachates are an important pool of organotin compounds (OTCs). In the present study transformation of OTCs in landfill leachate was investigated under simulated landfill conditions over a time span of six months by the use of isotopically enriched tin tracers, namely 117Sn-enriched tributyltin (TBT), 119Sn-enriched dibutyltin (DBT), 119Sn-enriched butyltin mix containing TBT, DBT and monobutyltin (MBT) and 117Sn-enriched SnCl2 and SnCl4. Quantification of OTCs was performed by gas chromatography – inductively coupled plasma mass spectrometry (GC-ICP-MS). To discriminate the biotic and abiotic transformations of OTCs and inorganic tin species, sterilization of leachate was also performed and data compared to non-sterilized samples. During the course of the experiment the microbial degradation of TBT was clearly manifested in Sn-enriched spiked leachate samples, while abiotic pathway of degradation was observed for DBT. Biomethylation process was also observed in the leachate spiked with Sn-enriched Sn2+ or Sn4+. Hydrolysis of Sn2+ and Sn4+ species was found to be a limiting factor which controlled the extent of methyltin formation. The present study importantly contributes to a better understanding of the processes that OTCs undergo in leachates, providing also useful information for taking measures necessary to prevent the release of toxic methyltin species to the nearby environment. Due to its novel approach by the use of stable isotopes as tracers to follow the fate of OTC and its originality the article was published in the most renowned journal FIRST from the field: Water Research (IF=4.655).
COBISS.SI-ID: 27462695
In the present work, the procedure based on alkaline melting of 50Cr enriched oxide for preparation of pure 50Cr(VI) spike solution is reported. Moreover, the microwave assisted digestion procedure of 53Cr enriched oxide for preparation of pure 53Cr(III) spike solution is also presented. The purity of 50Cr(VI) and 53Cr(III) isotopic spike solutions was verified by the speciation analysis applying hyphenation of anion-exchange FPLC to ICP-MS. In addition, the artefacts in Cr speciation, which may be initiated by the traces of oxidising and/or reducing agents present in Cr spike solutions, are also shown. The outcomes of our investigation highlighted the importance of the adequate preparation of spike solutions of Cr isotopes that may be used as reliable tracers in the investigations of the oxidation-reduction processes of Cr in wide range of environmentally relevant pH values. The isotopic tracers were applied in the investigations of the transformations of Cr(VI) in sewage sludge and inhibition of nitrification processes by hexavalent and trivalent chromium.
COBISS.SI-ID: 25807399