Influence of temperature on the chemical removal of 3-methylbutanal,trans-2-methyl-2-butenal,and 3-methyl-2-butenal by OH radicals in the troposphere

Absolute rate coefficients for the gas-phase reactions of OH radical with 3-methylbutanal (k₁), trans-2-methyl-2-butenal (k₂), and 3-methyl-2-butenal (k₃) have been obtained with the pulsed laser photolysis/laser-induced fluorescence technique. Gas-phase concentration of aldehydes was measured by UV absorption spectroscopy at 185 nm. Experiments were performed over the temperature range of 263–353 K at total pressures of helium between 46.2 and 100 Torr. No pressure dependence of all k_i (i = 1–3) was observed at all temperatures. In contrast, a negative temperature dependence of k_i (i.e., k_i increases when temperature decreases) was observed in that T range. The resulting Arrhenius expressions (±2σ) are: k₁(T) = (5.8 ± 1.7)×10^?12 exp{(499 ± 94)/T} cm³ molecule^?1 s^?1, k₂(T)=(6.9 ± 0.9)×10^?12 exp{(526 ± 42)/T} cm³ molecule^?1 s^?1, k₃(T)=(5.6 ± 1.2)×10^?12 exp{(666 ± 54)/T} cm³ molecule^?1 s^?1.The tropospheric lifetimes derived from the above OH-reactivity trend are estimated to be higher for 3-methylbutanal than those for the unsaturated aldehydes. A comparison of the tropospheric removal of these aldehydes by OH radicals with other homogeneous degradation routes leads to the conclusion that this reaction can be the main homogeneous removal pathway. However, photolysis of these aldehydes in the actinic region (λ > 290 nm) could play an important role along the troposphere, particularly for 3-methyl-2-butenal. This process could compete with the OH reaction for 3-methylbutanal or be negligible for trans-2-methyl-2-butenal in the troposphere.     

Defining Chlorophyll-a Reference Conditions in European Lakes

The concept of “reference conditions” describes the benchmark against which current conditions are compared when assessing the status of water bodies. In this paper we focus on the establishment of reference conditions for European lakes according to a phytoplankton biomass indicator—the concentration of chlorophyll-a. A mostly spatial approach (selection of existing lakes with no or minor human impact) was used to set the reference conditions for chlorophyll-a values, supplemented by historical data, paleolimnological investigations and modelling. The work resulted in definition of reference conditions and the boundary between “high” and “good” status for 15 main lake types and five ecoregions of Europe: Alpine, Atlantic, Central/Baltic, Mediterranean, and Northern. Additionally, empirical models were developed for estimating site-specific reference chlorophyll-a concentrations from a set of potential predictor variables. The results were recently formulated into the EU legislation, marking the first attempt in international water policy to move from chemical quality standards to ecological quality targets.     

Measurement of arsenic compounds in littoral zone algae from the Western Mediterranean Sea. Occurrence of arsenobetaine

The determination of arsenic compounds in algae collected on the Catalan coast (Western Mediterranean) is reported. Ten algae species and the seagrass Posidonia oceanica were analyzed. Total arsenic in the samples was determined by microwave digestion and inductively coupled plasma mass spectrometry (ICPMS). Arsenic speciation in water extracts of samples was analyzed by liquid chromatography with both anionic and cationic exchange with ICPMS detection (LC-ICPMS). The total arsenic content of the algae samples ranged from 2.96 to 39.0mg As kg(-1). The following compounds were detected: arsenite (As(III)), arsenate (As(V)), methylarsonate (MA), dimethylarsinate (DMA), sulfonate sugar (SO3-sug), sulfate sugar (SO4-sug), phosphate sugar (PO4-sug), arsenobetaine (AB), arsenocholine (AC), trimethylarsine oxide (TMAO) and glycerol sugar (Gly-sug). The main arsenic species found were arsenosugars. Significant percentages of arsenobetaine (0.54 mg As kg(-1), 28% of the extractable arsenic and 0.39 mg As kg(-1), 18% of the extractable arsenic) were found in Ulva rigida and Enteromorpha compressa. These results are discussed in relation to the presence of epiphytes.     

Tolerance to agricultural pesticides of strains belonging to four genera of Rhizobiaceae

In order to determine their tolerance to pesticides, 122 strains of rhizobia isolated from different geographical regions, and belonging to the genera Rhizobium, Mesorhizobium, Sinorhizobium and Bradyrhizobium were tested against eight herbicides, four fungicides and five insecticides. Sensitivity to the pesticides was measured by using the filter paper disk method at four concentrations, 0.45, 4.5, 45 and 450 μg per disk. When the pesticides were used at 0.45 μg per disk, a concentration similar to that found when pesticides are applied under field conditions, no inhibition was observed. Strains growth was affected at concentrations of 45 and 450 μg pesticide per disk. These higher concentrations can be encountered when seeds are treated with pesticides. Pesticides tolerance level was correlated to pesticide function, i.e rhizobial strains were more tolerant to insecticides, followed by herbicides and then fungicides. Two fungicides, captan and mancozeb, inhibited the highest number of strains. Only one insecticide, carbaryl, affected the growth of some rhizobial strains. Strains isolated from the arctic (Mesorhizobium spp. and R. leguminosarum bv. viciae), a putative pesticides-free environment, were either less or equally affected by pesticides compared to strains isolated from agricultural regions.     

Utilization of fly ash to improve the quality of the acid mine drainage generated by oxidation of a sulphide-rich mining waste: column experiments

The production of Acid Mine Drainage (AMD) as a result of the oxidative dissolution of sulphides is one of the main pollution problems affecting natural watercourses in mining environments with sulphide-rich residues. In this work, the generation of AMD was prevented by means of the addition of fly ash to sulphide-rich residues in non-saturated column experiments. A column experiment filled with a pyrite-rich sludge with artificial irrigation leached acid drainages (pH approx. 2) containing high concentrations of sulphate, iron and other metals. However, non-saturated column experiments filled with pyritic-rich sludge and fly ash drained leachates characterized by alkaline pH (pH up to 10), low sulphate concentration, and lack of iron and other metals in solution. The pyrite oxidative dissolution at high pH, as a consequence of the leaching of fly ash, favours the metal precipitation inside the column (mainly iron), the coating of pyrite grains, and the attenuation of the oxidation process, resulting in a great improvement in the quality of the leachates.     

Levels of metals, PCBs, PCNs and PAHs in soils of a highly industrialized chemical/petrochemical area: temporal trend

In 2005, the concentrations of various metals and organic pollutants were analyzed in soils collected in different areas of Tarragona (Catalonia, Spain), where an important chemical/petrochemical complex is located. The levels of seven elements (As, Cd, Cr, Hg, Mn, Pb and V), as well as those of polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs) and polycyclic aromatic hydrocarbons (PAHs) were determined in soils, and compared with those obtained in a background study carried out in 2002. Only Cd and Pb showed significant higher concentrations in the petrochemical zone, while no significant differences were found for the remaining elements. In turn, vanadium was the only element showing a significant increase in the concentration between 2002 and 2005. With regard to the organic pollutants, no significant differences were found according to the area of sampling. However, an increase in naphthalene levels was observed during the period 2002-2005 in soils of the chemical and petrochemical areas. According to the present results, it is suggested that the levels of vanadium must be periodically monitored to assure that the important industrialization of Tarragona does not mean health risks for the population living near the complex.     

Spatial and temporal trends of polycyclic aromatic hydrocarbons in wild mussels from the Cantabrian coast (N Spain) after the Prestige oil spill

Polycyclic aromatic hydrocarbon (PAH) levels were determined in tissues of wild mussels (Mytilus galloprovincialis) collected at 17 stations along the Cantabrian coast (N Spain), from Navia (Asturias) to Fuenterrabía (Basque Country), in order to assess the extent of the environmental impact caused by the Prestige oil spill (November 13, 2002). Six sampling campaigns were carried out in April, June and November in 2003 and 2004. The comparison of PAH data with those obtained earlier in 2000 showed a widespread pyrolytic and petrogenic contamination and allowed an estimation, for the first time, of the background pollution in the region and identification of the chronic hotspots. The spatial distribution found in the first samples after the oil spill revealed the eastern area as the most affected due to the continuous arrival of fuel slicks since early summer 2003. Several stations in this area showed increased total PAH concentrations of up to 15 times the pre-spill levels, which did not recover until April 2004, more than one year after the accident. Molecular parameters within the aliphatic and aromatic fractions were determined to assess the presence of Prestige oil in these samples.     

Monitoring PCDD/Fs and other organic substances in workers of a hazardous waste incinerator: a case study

The aim of this study was to measure, 6 years after regular operations, the concentrations of a number of organic substances in blood and urine of 19 workers employed at a hazardous waste incinerator (HWI) in Spain, and to establish the temporal variation with respect to baseline data and previously performed surveys. This facility was the first, and so far the only HWI in that country. The levels of hexachlorobenzene (HCB), polychlorinated biphenyls (PCB 28, 52, 101, 138, 153 and 180) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were analyzed in six composite plasma samples, while concentrations of di-, tri, and pentachlorophenols, as well those of 1-hydroxypyrene were measured in the urine of these workers. The current mean PCDD/F concentration, 10.4 ng I-TEQ/kg lipid, was significantly lower than that found in the baseline survey, 26.7 ng I-TEQ/kg lipid and similar to that found in the previous (2004) study (7.7 ng I-TEQ/kg lipid). PCDD/F levels in plasma were similar or even lower than those recently reported for various non-exposed populations. For the remaining analyzed substances in plasma and urine, there was not any significant increase in comparison with the levels found in the baseline survey. On the other hand, no marked differences between the concentrations of organic substances in plasma or urine were found according to the respective workplace (plant, laboratory and administration). The results of the present survey indicate that after 6 years of regular operation, the workers at the HWI are not occupationally exposed to PCDD/Fs and other organic substances in their workplaces.     

Ecotoxicological evaluation of sodium fluoroacetate on aquatic organisms and investigation of the effects on two fish cell lines

Sodium monofluoroacetate (compound 1080) is one of the most potent pesticides. It is also a metabolite of many other fluorinated compounds, including anticancer agents, narcotic analgesics, pesticides or industrial chemicals. Other sources of water contamination are the atmospheric degradation of hydrofluorocarbons and hydrochlorofluorocarbons. However, there is little information available about the adverse effects of sodium fluoroacetate in aquatic organisms. Firstly, the bacterium Vibrio fischeri (decomposer), the alga Chlorella vulgaris (1st producer) and the cladoceran Daphnia magna (1st consumer) were used for the ecotoxicological evaluation of SMFA. The most sensitive models were C. vulgaris and D. magna, with a NOAEL of 0.1 and an EC50 of 0.5 mM at 72 h, respectively. According to the results after the acute exposure and due to its high biodegradation rate and low bioaccumulation potential, sodium fluoroacetate is most unlikely to produce deleterious effects to aquatic organisms. Secondly, two fish cell lines were employed to investigate the effects and mechanisms of toxicity in tissues from 2nd consumers. The hepatoma fish cell line PLHC-1 was more sensitive to SMFA than the fibroblast-like fish cell line RTG-2, being the uptake of neutral red the most sensitive bioindicator. Lysosomal function, succinate dehydrogenase and acetylcholinesterase activities were inhibited, glucose-6-phosphate dehydrogenase activity was particularly stimulated, and metallothionein and ethoxyresorufin-O-deethylase levels were not modified. Intense hydropic degeneration, macrovesicular steatosis and death mainly by necrosis but also by apoptosis were observed. Moreover, sulphydryl groups and oxidative stress could be involved in PLHC-1 cell death induced by SMFA more than changes in calcium homeostasis.     

A neural-fuzzy approach to classify the ecological status in surface waters

A methodology based on a hybrid approach that combines fuzzy inference systems and artificial neural networks has been used to classify ecological status in surface waters. This methodology has been proposed to deal efficiently with the non-linearity and highly subjective nature of variables involved in this serious problem. Ecological status has been assessed with biological, hydro-morphological, and physicochemical indicators. A data set collected from 378 sampling sites in the Ebro river basin has been used to train and validate the hybrid model. Up to 97.6% of sampling sites have been correctly classified with neural-fuzzy models. Such performance resulted very competitive when compared with other classification algorithms. With non-parametric classification-regression trees and probabilistic neural networks, the predictive capacities were 90.7% and 97.0%, respectively. The proposed methodology can support decision-makers in evaluation and classification of ecological status, as required by the EU Water Framework Directive.