Identification of arsenobetaine in sole,lemon sole,flounder, dab,carb and shrimps by field desorption and fast atom bombardment mass spectrometry

Organo-arsenic has been isolated from sole, lemon sole, flounder, dab, crab and shrimps by extraction or ion-exchange in combination with thin-layer chromatography. An alkaline digestion of the samples, followed by a reduction with sodiumborohydride leads to the formation of trimethylarsine. The behaviour of the organo-arsenic compound was very similar to that of synthesized arsenobetaine. Field desorption mass spectrometry (FDMS) can be used to identify arsenobetaine in the isolates. Sufficient purification by thin-layer chromatography is found to be a prerequisite for the detection of a protonated molecular ion of arsenobetaine. If this situation is not met acid enhanced FDMS or Fast Atom Bombardment mass spectrometry in high resolution can be used successfully.     

Influence of air pollution on the incidence of respiratory tract neoplasm

To evaluate the possible influence of air pollutants on the incidence of respiratory tract neoplasm we studied 12 S?o Paulo City districts where air pollution is observed. We collected data on pollutants from 1981-1990 and correlated it with the incidence of larynx and lung neoplasms in 1997. Ozone was the pollutant that best correlated with the incidence of neoplasm. The correlation coefficients were 0.7234 (p=0.277) and 0.9929 (p=0.007) for lung and larynx cancer, respectively. There may be a relationship between air pollution and the incidence of respiratory tract neoplasm. This study, however, does not allow us to conclude that there is a causal relationship.     

Spectroscopic behavior of oxygenated combustion by-products

The oxygenated species, massively produced in the energy production plants based on combustion processes, constitute one of the most numerous categories of hazardous air pollutants. Therefore, development of real time diagnostic tools are needed in order to study their formation during combustion processes and to reveal their presence both in the exhaust and in the atmosphere. In this work, oxygenated compounds were identified inside fuel-rich premixed ethylene/air flames by means of ultraviolet fluorescence spectroscopy with the support of qualitative chemical analysis of the sampled combustion gases.

Strong band progression, typical of aldehydic functionality, were recognized in fluorescence spectra (λ_exc=355 nm) measured in the early oxidation region of premixed flames varying the equivalence ratio from 3.0 up 21.6. Downstream of the oxidation region, spectroscopic signatures of pyrolytic species were found to prevail on those peculiar of oxygenated compound. The position and the extension of the two main flame zones were found to depend on the flame conditions (C/O ratio) due to the effect of the C/O ratio on the temperature history along the flame axis. This correlation was interpreted on the basis of the measured axial temperature profiles.     

Evaluation of soil temperature effect on herbicide leaching potential into groundwater in the Brazilian Cerrado

The effect of annual variations in the daily average soil temperatures, at different depths, on the calculation of pesticide leaching potential indices is presented. This index can be applied to assess the risk of groundwater contamination by a pesticide. It considers the effects of water table depth, daily recharge net rate, pesticide sorption coefficient, and degradation rate of the pesticide in the soil. The leaching potential index is frequently used as a screening indicator in pesticide groundwater contamination studies, and the temperature effect involved in its calculation is usually not considered. It is well known that soil temperature affects pesticide degradation rates, air-water partition coefficient, and water-soil partition coefficient. These three parameters are components of the attenuation and retardation factors, as well as the leaching potential index, and contribute to determine pesticide behavior in the environment. The Arrhenius, van't Hoff, and Clausius-Clapeyron equations were used in this work to estimate the soil temperature effect on pesticide degradation rate, air-water partition coefficient, and water-soil partition coefficient, respectively. The relationship between leaching potential index and soil temperature at different depths is presented and aids in the understanding of how potential pesticide groundwater contamination varies on different climatic conditions. Numerical results will be presented for 31 herbicides known to be used in corn and soybean crops grown on the municipality of S?o Gabriel do Oeste, Mato Grosso do Sul State, Brazil.     

A voltammetric screening method to determine ronidazole in bovine meat

Abstract

An original voltammetric screening method, employing glassy carbon electrode (GCE) with the differential-pulse voltammetry technique (DPV), has been developed to determine residues of the anti-parasitic agent Ronidazole (RNZ) in bovine meat. By using cyclic voltammetry (CV), it has been demonstrated that an irreversible cathodic process occurs at approximately ?0.740?V (vs. Ag|AgCl, KCl 3?mol L^?1) in a 0.100?mol L^?1 phosphate buffer at pH 6.5 as supporting electrolyte. Furthermore, the behavior of RNZ in CV indicates the occurrence of a diffusion mass transfer process to the working electrode surface. The RNZ reduction mechanism was proposed as a 6-electron transfer, similar to Metronidazole under the same pH range. Quantification of RNZ and method validation were then carried out by DPV. The relative standard deviation (RSD) were 3.21% for intraday precision of 10 consecutive repetitions and 6.78% for interday precision after five analysis. Limits of detection and quantification were also obtained, and the values were 0.107 and 0.358?mg kg^?1, respectively. The recovery percentage for three different concentrations of RNZ in the bovine meat matrix ranged between 98.1% and 100.3%. The method proved to be efficient for screening RNZ in bovine meat.     

Enhanced solubilization of arsenic and 2,3,4,6 tetrachlorophenol from soils by a cyclodextrin derivative

The application of extracting aqueous solutions with cyclodextrins in several soil remediation technologies has been increasingly studied but little is known about their removal capacities toward the inorganic species. Herein, the effectiveness of cyclodextrins (CDs) in extracting arsenic, copper, and iron from a mining soil is presented. In a preliminary test of four types of CD aqueous solutions, only the addition of carboxylmethyl-beta-cyclodextrin CMCD (a cyclodextrin derivative) led to a significant enhancement in arsenic removal. An increase in the concentration of copper and iron in the leachates was also observed with CMCD. Kinetic study of arsenic release was carried out at two temperatures (20 and 35 degrees C). The arsenic concentration in the leachates increases with increasing cyclodextrin concentration. At an 80 mM CMCD concentration, arsenic, copper, and iron released in filtrates were about 20-, 1,000-, and 4,000-fold greater, respectively, than that obtained using deionized water. In the soil system, the CMCD capacity removal was found to be higher for cations than for arsenic. Because the tetrachlorophenol can co-occur with arsenic and copper in several contaminated sites, its solubilization by CMCD was also investigated. Extraction experiments were performed to extract 2,3,4,6 tetrachlorophenol (TeCP) in spiked soil with CMCD. The results of batch experiments have shown that CMCD could significantly increase the TeCP extraction from soil. CD sorption on soils as quantified by a fluorescence technique was low, indicating no significant loss of CD during the leaching experiments. The use of CMCD as a flushing agent to enhance the removal of both inorganic and organic pollutants from mixed-contaminated soils appears as a promising remediation method.     

The ecological and economic potential of carbon sequestration in forests: examples from South America

Costs of reforestation projects determine their competitiveness with alternative measures to mitigate rising atmospheric CO2 concentrations. We quantify carbon sequestration in above-ground biomass and soils of plantation forests and secondary forests in two countries in South America-Ecuador and Argentina-and calculate costs of temporary carbon sequestration. Costs per temporary certified emission reduction unit vary between 0.1 and 2.7 USD Mg(-1) CO2 and mainly depend on opportunity costs, site suitability, discount rates, and certification costs. In Ecuador, secondary forests are a feasible and cost-efficient alternative, whereas in Argentina reforestation on highly suitable land is relatively cheap. Our results can be used to design cost-effective sink projects and to negotiate fair carbon prices for landowners.