Degradation of azo dyes in water by Electro-Fenton process

The degradation of the azo dyes azobenzene, p-methyl red and methyl orange in aqueous solution at room temperature has been studied by an advanced electrochemical oxidation process (AEOPs) under potential-controlled electrolysis conditions, using a Pt anode and a carbon felt cathode. The electrochemical production of Fenton's reagent (H₂O₂, Fe²⁺) allows a controlled in situ generation of hydroxyl radicals (^·OH) by simultaneous reduction of dioxygen and ferrous ions on the carbon felt electrode. In turn, hydroxyl radicals react with azo dyes, thus leading to their mineralization into CO₂ and H₂O. The chemical composition of the azo dyes and their degradation products during electrolysis were monitored by high performance liquid chromatography (HPLC). The following degradation products were identified: hydroquinone, 1,4-benzoquinone, pyrocatechol, 4-nitrocatechol, 1,3,5-trihydroxynitrobenzene and p-nitrophenol. Degradation of the initial azo dyes was assessed by the measurement of the chemical oxygen demand (COD). Kinetic analysis of these data showed a pseudo-first order degradation reaction for all azo dyes. A pathway of degradation of azo dyes is proposed. Specifically, the degradation of dyes and intermediates proceeds by oxidation of azo bonds and aromatic ring by hydroxyl radicals. The results display the efficiency of the Electro-Fenton process to degrade organic matter. Electronic Publication     

European scale application of atmospheric reactive nitrogen measurements in a low-cost approach to infer dry deposition fluxes

A European scale network was established in 2006 as part of the NitroEurope Integrated Project to infer reactive nitrogen (Nr) dry deposition fluxes, based on low-cost sampling of gaseous and aerosol species and inferential modelling. The network provides monthly measurements of NH₃, NH₄⁺, HNO₃ and NO₃⁻, as well as SO₂, SO₄²⁻, HCl, Cl⁻ and base cations at 58 sites. Measurements are made with an established low-cost denuder methodology (DELTA) as a basis to: (1) examine temporal trends and spatial patterns across Europe, (2) improve and calibrate inferential modelling techniques to estimate exchange of Nr species, (3) provide best estimates of atmospheric dry N deposition, and (4) permit an analysis of net GHG exchange in relation to atmospheric and agricultural N inputs at the European scale. Responsibility for measurements is shared among seven European laboratories. An inter-comparison of the DELTA implementation by 6 laboratories at 4 test sites (Montelibretti, Italy; Braunschweig, Germany; Paterna, Spain and Auchencorth, UK) from July to October 2006 provided training for the laboratories and showed that good agreement was achieved in different climatic conditions (87% of laboratory site-means within 20% of the inter-laboratory median). Results obtained from the first year of measurements show substantial spatial variability in atmospheric Nr concentrations, illustrating the major local (NH₃) and regional (HNO₃, NO₃⁻, and NH₄⁺) differences in Nr concentrations. These results provide the basis to develop future estimates of site-based Nr dry deposition fluxes across Europe, and highlight the role of NH₃, largely of agricultural origin, which was the largest single constituent and will dominate dry Nr fluxes at most sites.     

Persistent organochlorine compounds in soils and sediments of European high altitude mountain lakes

The composition of persistent organochlorine compounds (OC) in soils and sediments from two high altitude European mountain lakes, Redon in the Pyrenees and Ladove in the Tatra mountains, has been studied. Sediment cores from two additional lakes in the Tatra mountains, Starolesnianske Pleso and Dlugi Staw, have also been examined. DDTs (1.7-13 ng g(-1)) were the most abundant OC in soils followed by total polychlorobiphenyls (PCBs; 0.41-1.5 ng g(-1)) and hexachlorobenzene (HCB; 0.15-0.91 ng g(-1)). In sediments, the dominant OC were also DDTs (3.3-28 ng g(-1)) and PCBs (2.3-15 ng g(-1)). These concentrations are low, involving absence of major pollution sources in these high mountain regions. The downcore OC profiles in soils and sediments were similar but higher concentrations and steeper vertical gradients were observed in the latter. Radiometric determinations showed absence of significant OC transport from catchment to lake. The sediment-soil difference points therefore to a better retention of the OC load in sediments than soils which may be related to the low temperatures that are currently encountered at the bottom of the lake water column and the depletion of sediment bioturbation in these cold environments. Significant qualitative changes in the soil PCB distributions are observed downcore. These involve a dominance of the high molecular weight congeners in the top core sections and those of lower weight (i.e. less chlorinated) in the bottom. Anaerobic dechlorination of higher molecular weight congeners occurring in microsites, e.g. as observed in flooded or poorly drained soils, could be responsible for these changes. This process could be concurrent to bioturbation.     

The Influence of Mycorrhiza on Uranium and Phosphorus Uptake by Barley Plants from a Field-contaminated Soil (7 pp)

Background Recent studies indicated that arbuscular mycorrhizal fungi (AMF) play important roles in plant accumulation of uranium (U) from contaminated environments, but the impacts of fertilization practices on functioning of the symbiotic associations, which are crucial factors influencing plant nutrition and growth responses to mycorrhiza, have rarely been considered. Materials and Methods In a greenhouse experiment, a bald root barley mutant (brb) together with the wild type (wt) were used to test the role of root hairs and AMF in uranium (U) uptake by host plants from a U contaminated soil. Nil, 20 and 60 mg KH2PO4-P kg–1 soil were included to investigate the influences of phosphorus (P) fertilization on plant growth and accumulation of U. Results Dry matter yield of barley plants increased with increasing P additions and wt produced significantly higher dry weight than brb. Mycorrhiza markedly improved dry matter yield of both genotypes grown at nil P, whereas only brb responded positively to mycorrhiza at 20 mg P kg-1. At the highest P level, mycorrhiza resulted in growth depressions in both genotypes, except for the roots of wt. In general, plant P concentrations increased markedly with increasing P additions and in response to mycorrhiza. Mycorrhiza and P additions had no significant effects on shoot U concentrations. However, root U concentrations in both genotypes were significantly increased by mycorrhiza. On the other hand, shoot U contents increased with increasing P levels, while 20 mg P kg-1 stimulated, but 60 mg P kg-1 marginally affected the U accumulation in roots. Root length specific U uptake was moderately enhanced both by root hairs and strongly enhanced by mycorrhiza. Moreover, non-inoculated plants generally had higher shoot-root ratios of U content than the corresponding inoculated controls. Conclusion Our study shows that AMF and root hairs improves not only P acquisition but also the root uptake of U, and mycorrhiza generally decreases U translocation from plant root to shoot. Hence, mycorrhiza is of potential use in the phytostabilization of U contaminated environments. Perspectives The complex impacts of P on U accumulation by barley plants suggested that U behavior in mycorrhizosphere and translocation along the soil-fungi-plant continuum as affected by fertilization practices deserve extensive studies for optimizing the function of mycorrhizal associations for phytoremediation purposes.     

Cyanide Removal by Chinese Vegetation. Quantification of the Michaelis-Menten Kinetics (6 pp)

Background Little is known about metabolism rates of environmental chemicals by vegetation. A good model compound to study the variation of rates among plant species is cyanide. Vascular plants possess an enzyme system that detoxifies cyanide by converting it to the amino acid asparagine. Knowledge of the kinetic parameters, the half-saturation constant (Km) and the maximum metabolic capacity (vmax), is very useful for enzyme characterization and biochemical purposes. The goal of this study is to find the enzyme kinetics (KM and vmax) during cyanide metabolism in the presence of Chinese vegetation, to provide quantitative data for engineered phytoremediation, and to investigate the variation of metabolic rates of plants. Methods Detached leaves (1.0 g fresh weight) from 12 species out of 9 families were kept in glass vessels with 100 mL of aqueous solution spiked with potassium cyanide at 23°C for 28 h. Four different treatment concentrations of cyanide were used, ranging from 0.44 to 7.69 mg CN/L. The disappearance of cyanide from the aqueous solution was analyzed spectrophotometrically. Realistic values of the half-saturation constant (KM) and the maximum metabolic capacity (vmax) were estimated by a computer program using non-linear regression treatments. As a comparison, Lineweaver-Burk plots were also used to estimate the kinetic parameters. Results and Discussion The values obtained for KM and vmax varied with plant species. Using non-linear regression treatments, values of vmax and KM were found in a range between 6.68 and 21.91 mg CN/kg/h and 0.90 to 3.15 mg CN/L, respectively. The highest vmax was by Chinese elder (Sambucus chinensis), followed by upright hedge-parsley (Torilis japonica). The lowest vmax was demonstrated by the hybrid willow (Salix matssudana x alba). However, the highest KM was found in the water lily (Nymphea teragona), followed by the poplar (Populus deltoides Marsh). The lowest KM was demonstrated by corn (Zea mays L.). The values of vmax were normally distributed with a mean of 13 mg CN/kg/h. Conclusions Significant removal of cyanide from aqueous solution was observed in the presence of plant materials without phytotoxicity, even at high doses of cyanide. This gives rise to the conclusion that the Chinese plant species used in this study are all able to efficiently metabolize cyanide, although with different maximum metabolic capacities. A second conclusion is that the variation of metabolism rates between species is small. All these plants had a similar KM, indicating the same enzyme is active in all plants. Recommendations and Outlook Detoxification of cyanide with trees seems to be a feasible option for cleaning soils and water contaminated with cyanide. For phytoremediation projects, screening appropriate plant species adapted to local conditions should be seriously considered. More chemicals should be investigated to find common principles of the metabolism of environmental chemicals by plants.     

Atmospheric BTEX concentrations in the vicinity of the crude oil refinery of the Baltic region

Among chemical industries, petroleum refineries have been identified as large emitters of a wide variety of pollutants. Benzene, toluene, ethylbenzene, and xylene (BTEX) form an important group of aromatic volatile organic compounds (VOCs) because of their role in the troposphere chemistry and the risk posed to human health. A very large crude oil refinery of the Baltic States (200,000 bbl/day) is situated in the northern, rural part of Lithuania, 10 km from the town of Ma?eikiai (Lithuania). The objectives of this study were: (1) to determine of atmospheric levels of BTEX in the region rural and urban parts at the vicinity of the crude oil refinery; and (2) to investigate the effect of meteorological parameters (wind speed, wind direction, temperature, pressure, humidity) on the concentrations measured. The averaged concentration of benzene varied from 2.12 ppbv in the rural areas to 2.75 ppbv in the urban areas where the traffic was determined to be a dominant source of BTEX emissions. Our study showed that concentration of benzene, as strictly regulated air pollutant by EU Directive 2008/50/EC, did not exceed the limit of 5 ppbv in the region in the vicinity of the crude oil refinery during the investigated period. No significant change in air quality in the vicinity of the oil refinery was discovered, however, an impact of the industry on the background air quality was detected. The T/B ratio (0.50-0.81) that was much lower than 2.0, identified other sources of pollution than traffic.     

Alnus shrub expansion increases evapotranspiration in the Swiss Alps

Regional Environmental Change - Shrub encroachment is one of the main consequences of abandonment of montane grassland. Higher surface roughness of shrubs leads to stronger aerodynamic coupling....     

Intraspecific hyperparasitism in a primary hymenopteran parasitoid

In solitary parasitoids, in which only one individual can emerge per host, the adaptive value of conspecific superparasitism is a function of the survival probability of the egg laid by the superparasitizing female. In the few cases which these probabilities are compared, the oldest immature has an advantage over the other individuals. We measured the acceptance rate of parasitized hosts and survival rate of supernumerary larvae in Anaphes victus (Hymenoptera: Mymaridae) in relation to the interval between ovipositions. When this interval was 5–7 days, the first immature was at the prepupa and pupa stage respectively, and female Anaphes victus changed their oviposition behavior markedly. They killed the developing parasitoid of their own species before ovipositing in it. The progeny of these females, which are normally primary parasitoids, developed thereafter as hyperparasitoids. Indeed, in contrast with other species, the survival of the second female's progeny increased with the time interval between ovipositions. This type of facultative intraspecific hyperparasitism is different from autoparasitism in Aphelinidae and has never been mentioned in other parasitoids; it would be adaptive if females of this short-lived species encounter low-quality patches.     

Qualitative time trend analysis of ground water monitoring networks

The detection of significant (short-term) time trends is one of the major goals of ground water monitoring networks. These trends can be used to recognize active geochemical processes and potential environmental threats. This paper presents a case history of time trend analysis on macrochemical parameters of ground water quality. It shows the difficulties and traps that are generally encountered in such studies. The data used originated from the Dutch National Groundwater Quality Monitoring Network. This network is operative since 1979, and keeps track of the ground water composition at 350 locations at two depths (ca. 10 and 25 m below surface; general density, one location per 100 km²). Prior to the trend analysis the data set was divided into geochemically homogeneous groups using fuzzy c-means clustering. Each group represents a specific ground water type, characterized by a distinct source (seawater, surface water or precipitation) and a unique combination of dominant geochemical processes (e.g. mineralization of organic matter, carbonate dissolution and cation exchange).To study trends qualitatively, the concentrations of the various macro-constituents in ground water are correlated with time of sampling. The nonparametric and outlier insensitive Spearman rank correlation coefficient is computed per well screen. A frequency distribution of correlation coefficients is formed by combining the Spearman correlation coefficients of all individual wells within a homogeneous group. This distribution is tested for trends against the appropriate theoretical distribution of zero correlation by use of the Kolmogorov-Smirnov one-sample test. The type of trend is derived from the shape of the distribution.Most ground water types show statistically significant qualitative trends, of which many, however, are caused by changes in the sampling and analytical procedures over the monitoring period. After elimination of differences in limits of detection for NO₃, total-P, and NH₄, most trends in these compounds disappeared. In some water types trends for alkalinity, apparent trends for pH, Ec, and total-P are caused by variations in the laboratory practice, e.g. varying storage procedures, leading to erroneous analyses. Other parameters showed statistically significant trends, related to geochemical processes.The most interesting and most substantial trends are observed in the water type characterized by infiltrating rainwater with agricultural pollutants. In this water type the lowering ground water table induces lower rates of evapotranspiration, giving lower concentrations in time of conservative parameters (Cl, Na, Ca). The aerated zone is enlarged, resulting in increased oxidation of organic material, less efficient nutrient (NO₃, K) uptake by plant roots, leading to increased ground water concentrations of nutrients. In other water types trends are quantitatively small. However, trends are not necessarily linear, and all should be closely monitored in future.     

Morphological features of a case of retinoic acid embryopathy

A case of retinoic acid embryopathy which was retrospectively diagnosed after delivery is presented. The affected fetus was exposed to the drug during the first month of pregnancy and second-trimester sonographic examination showed hydrocephalus and cardiacmalformation. The diagnosis was made on the basis of autopsy findings and genetic enquiry.