Evaluation of relative photonic efficiency in heterogeneous photocatalytic reactors

The evaluation of photonic efficiency in heterogeneous photocatalysis remains elusive because the number of absorbed photons is difficult to assess experimentally. The photonic efficiency of heterogeneous photocatalytic reactors depends on the reactor geometry, irradiation source, and photocatalyst properties. In this work, the relative photonic efficiency of heterogeneous photocatalytic reactors to degrade an azo dye was evaluated using phenol as the standard system. The experimental tests were carried out in a batch reactor under different conditions of pH, catalyst dosage, initial concentration, and ultraviolet (UV) lamps. The kinetics of disappearance of both phenol and azo dye were studied using the initial rate method and were described according to the Langmuir-Hinshelwood (L-H) kinetic model. It was observed that the relative photonic efficiency depends on the adsorption/desorption properties of the photocatalyst.     

Comparison of different physiological parameter responses in Lemna minor and Scenedesmus obliquus exposed to herbicide flumioxazin

The sensitivity of different physiological parameters in Scenedesmus obliquus and Lemna minor exposed to herbicide (flumioxazin) was investigated to indicate the most convenient and sensitive parameter. To assess toxicity of flumioxazin, we used a panel of biomarkers: pigment contents, chlorophyll fluorescence parameters and antioxidative enzyme activities. Algae and duckweed were exposed to 48-h IC50 for growth rate. In L. minor, the sensitivity of the parameters was as follows: QN > Oxygen emmision > phiS(PSII) > QP > phi(PSII) > CAT, GR > Pigment> APO > Growth. For S. obliquus, this ranking was as follows: CAT > Oxygen emission > QP > APO > GR > Pigment > phiS(PSII) > Growth > phi(PSII) > QN (from the greatest to the least sensitive). The results demonstrated that the observed toxicity is related not only to interspecific variations but also to the selected parameter.     

Inflammation biomarkers associated with arsenic exposure by drinking water and respiratory outcomes in indigenous children from three Yaqui villages in southern Sonora,México

Environmental Science and Pollution Research - Environmental arsenic exposure in adults and children has been associated with a reduction in the expression of club cell secretory protein (CC16) and...     

Rapporteurs' report on discussions at the workshop on excess nitrogen deposition, Leatherhead, September 1987

This paper reports major points from the discussions which took place during the Workshop on Excess Nitrogen Deposition.     

Determination of selected quaternary ammonium compounds by liquid chromatography with mass spectrometry. Part I. Application to surface, waste and indirect discharge water samples in Austria

A method for simultaneous quantitative determination of alkyl benzyl, dialkyl and trialkyl quaternary ammonium compounds (QACs) has been developed, validated and subsequently applied to real water samples in Austria. The method employs liquid-liquid extraction (LLE) followed by liquid chromatography/tandem mass spectrometry (LC-MS/MS), using electrospray ionization (ESI) in positive mode. The overall method quantification limits range from 4 to 19ng/L for the enrichment of 500mL water samples and analyte recoveries are between 80 and 99%. The method was applied to 62 of the respective water samples without filtration to avoid the loss of the analytes due to the high adsorption capacity of these compounds. Maxima in the mg/L range, especially in the wastewater of hospitals and laundries, could be detected for the selected target compounds.     

Analysis and fit of surface CO2 concentrations at a rural site

Purpose

The impact of CO₂ urban plume in a rural area was investigated by concentrations recorded near surface.

Methods

CO₂ dry concentrations at three levels near surface were recorded for about 8 months at a rural site. Daily cycles were obtained and directional analysis was made with percentiles. Several functions were used to fit background and plume concentrations and the goodness of fit was evaluated with different statistics, which were also compared.

Results

Daily cycle showed a difference of around 2 ppm during the night between the lowest (1.8 m) and the highest (8.3 m) levels. Weighting functions of the directional analysis revealed the influence of the Valladolid urban plume. Two regions were established, with local factors prevailing below 3 m?s^?1 and transport dominating above 6 m?s^?1. The best fit was achieved with a quadratic function for the background and a cubic function for the plume due to the lack of symmetry observed. Gamma and Weibull distributions were also successfully used. Some statistics, such as the root mean square error (RMSE), stood out when evaluating the goodness of fit, whilst others were discarded due to their extremely low values and the lack of sensitivity against the functions used. Finally, a comprehensive metric merging several statistics was also tested with slight differences against RMSE.     

Validation of an analytical method for the quantification of pyrethrins on lemons and apricots using high-performance liquid chromatography/mass spectrometry

An analytical procedure has been developed for the determination of natural pyrethrins (pyrethrin I, pyrethrin II, jasmolin I, jasmolin II, cinerin I and cinerin II) in lemon and apricot. The QuEChERS method, which stands for quick, easy, cheap, effective, rugged and safe was used for extraction. Analysis of the extract was performed by liquid-chromatography-electrospray ionisation-tandem mass spectrometry. The ions prominent in the ESI spectra were [M+H]+ for the six compounds. A Zorbax SB-C18 column was used with a programmed gradient mobile phase consisting of (A) water containing 0.1% formic acid and 5 mM ammonium formate and (B) ACN. The method was linear within the investigated concentration range, displaying a calibration curve correlation factor of 0.99. The coefficients of variation obtained (RSD) were below 20% and the recoveries were in the 70-110% range.     

Conceptual and Numerical Modeling of Radionuclide Transport and Retention in Near-Surface Systems

Scenarios of barrier failure and radionuclide release to the near-surface environment are important to consider within performance and safety assessments of repositories for nuclear waste. A geological repository for spent nuclear fuel is planned at Forsmark, Sweden. Conceptual and numerical reactive transport models were developed in order to assess the retention capacity of the Quaternary till and clay deposits for selected radionuclides, in the event of an activity release from the repository. The elements considered were carbon (C), chlorine (Cl), cesium (Cs), iodine (I), molybdenum (Mo), niobium (Nb), nickel (Ni), radium (Ra), selenium (Se), strontium (Sr), technetium (Tc), thorium (Th), and uranium (U). According to the numerical predictions, the repository-derived nuclides that would be most significantly retained are Th, Ni, and Cs, mainly through sorption onto clays, followed by U, C, Sr, and Ra, trapped by sorption and/or incorporation into mineral phases.     

Heterogeneous photocatalytic decomposition of halosubstituted benzyl alcohols on semiconductor particles in aqueous media

The photodegradation of 2-, 3- and 4-halosubstituted benzyl alcohols (HBAs) on semiconductive oxides (TiO2, ZnO) was studied. It was found out that the photodegradation rate increases from the fluoro to bromo derivates in the case of 2- and 4-HBAs, whereas in the case of 3-HBAs the reverse trend was observed.