Electrochemical advanced oxidation processes: today and tomorrow. A review

In recent years, new advanced oxidation processes based on the electrochemical technology, the so-called electrochemical advanced oxidation processes (EAOPs), have been developed for the prevention and remediation of environmental pollution, especially focusing on water streams. These methods are based on the electrochemical generation of a very powerful oxidizing agent, such as the hydroxyl radical (^?OH) in solution, which is then able to destroy organics up to their mineralization. EAOPs include heterogeneous processes like anodic oxidation and photoelectrocatalysis methods, in which ^?OH are generated at the anode surface either electrochemically or photochemically, and homogeneous processes like electro-Fenton, photoelectro-Fenton, and sonoelectrolysis, in which ^?OH are produced in the bulk solution. This paper presents a general overview of the application of EAOPs on the removal of aqueous organic pollutants, first reviewing the most recent works and then looking to the future. A global perspective on the fundamentals and experimental setups is offered, and laboratory-scale and pilot-scale experiments are examined and discussed.     

Gemfibrozil modulates cytochrome P450 and peroxisome proliferation-inducible enzymes in the liver of the yellow European eel (Anguilla anguilla)

The human lipid regulator gemfibrozil (GEM) has been shown to induce peroxisome proliferation in rodents leading to hepatocarcinogenesis. Since GEM is found at biological active concentrations in the aquatic environment, the present study investigates the effects of this drug on the yellow European eel (Anguilla anguilla). Eels were injected with different concentrations of GEM (0.1 to 200 μg/g) and sampled 24- and 96-h post-injection. GEM was shown to inhibit CYP1A, CYP3A and CYP2K-like catalytic activities 24-h post-injection, but at 96-h post-injection, only CYP1A was significantly altered in fish injected with the highest GEM dose. On the contrary, GEM had little effect on the phase II enzymes examined (UDP-glucuronyltransferase and glutathione-S-transferase). Peroxisome proliferation inducible enzymes (liver peroxisomal acyl-CoA oxidase and catalase) were very weakly induced. No evidence of a significant effect on the endocrine system of eels was observed in terms of plasmatic steroid levels or testosterone esterification in the liver.     

Mineralization of the biocide chloroxylenol by electrochemical advanced oxidation processes

Electrochemical advanced oxidation processes (EAOPs) are environmentally friendly methods based on the destruction of organic pollutants in wastewaters with in situ electrogenerated hydroxyl radical. This species is formed in anodic oxidation (AO) from water oxidation at the anode and in indirect electro-oxidation methods like electro-Fenton (EF) and photoelectro-Fenton (PEF) also from reaction between catalytic Fe2+ and H2O2 continuously produced at the O2-diffusion cathode. The PEF method involves the irradiation of the treated solution with UVA light to enhance the photolysis of organics including Fe(III) complexes. In this work, the oxidation power of such EAOPs to decontaminate synthetic wastewaters of the biocide chloroxylenol (4-chloro-3,5-dimethylphenol) at pH 3.0 is comparatively examined with an undivided electrolytic cell containing a Pt or boron-doped diamond (BDD) anode and a stainless steel or O2-diffusion cathode. The initial chlorine is released as Cl(-) ion, which remains stable in the medium using Pt or is oxidized to Cl2 on BDD. The biocide solutions can be completely decontaminated using AO with a BDD anode, as well as PEF with a Pt or BDD anode. The PEF procedure with a BDD anode is the most powerful method leading to total mineralization in about 300 min, practically independent of current density. When current density rises, the degradation rate of processes increases, but they become less efficient due to the larger enhancement of waste reactions of oxidants. Chloroxylenol is much more rapidly removed in EF and PEF than in AO. 2,6-dimethylhydroquinone, 2,6-dimethyl-p-benzoquinone and 3,5-dimethyl-2-hydroxy-p-benzoquinone are identified as aromatic by-products, and maleic, malonic, pyruvic, acetic and oxalic acids are found as generated carboxylic acids. A general pathway for chloroxylenol mineralization by all EAOPs including the above by-products is proposed.     

The effects of predator abundance and habitat structural complexity on survival of juvenile sea urchins

We studied the effect of the abundance of predatory fishes and structural complexity of algal assemblages on the survival of juveniles of the sea urchin Paracentrotus lividus on Mediterranean infralittoral rocky bottoms. Post-settlement juveniles (2–10 mm) were placed on four distinct natural substrates with increasing structural complexity (coralline barren, algal turf, erect fleshy algal assemblages and small crevices) inside and outside the Medes Islands Marine Reserve. Predation on these sea urchins increased at greater abundance of predatory fishes, and decreased with greater structural complexity. The refuge provided by structural complexity, however, decreased with increasing size of sea urchin recruits. Predation on the smallest post-settlers was carried out almost exclusively by small fishes (<20 cm), mainly the labrid Coris julis, while the dominant predator of larger juveniles was the sparid Diplodus sargus. Our results demonstrate the cascading effects caused by the prohibition of fishing in marine reserves, and highlight the potential role of small predatory fishes in the control of sea urchin populations.Communicated by O. Kinne, Oldendorf/Luhe     

Removal of the herbicide amitrole from water by anodic oxidation and electro-Fenton

Here we demonstrate that an aqueous solution of the herbicide amitrole can be completely depolluted at pH 3.0 by anodic oxidation and electro-Fenton process. Anodic oxidation gives faster degradation with a boron-doped diamond anode than with a Pt anode. Electro-Fenton with a Pt anode and 1 mmol l ^–1 Fe²⁺ as catalyst yields the quickest depollution. Amitrole decay always follows a pseudo first-order reaction. NO₃^– and NH₄⁺ are accumulated in the medium during mineralization, although volatile N-products are also formed. These environmentally friendly electrochemical treatments could be applied to the remediation of wastewaters containing amitrole.     

New observations of the gills of Placopecten magellanicus (Mollusca: Bivalvia), and implications for nutrition

The organization, general anatomy, and surface microanatomy of all regions of the gills of a representive bivalve mollusc, Placopecten magellanicus Gmelin, were studied using stereo-microscopic, histological, and scanning electron microscopic techniques. Individuals were collected in May and November 1985 from Chamcook Bay, New Brunswick, Canada. In addition to correcting earlier accounts of this structure, a number of new observations are reported. The orientation of the ciliated spurs appears to be responsible for the sinusoidal arrangement of the gill filaments. Micrographs showing the structure of the dorsal respiratory expansion are presented. The entire abfrontal surface of the principal filament, including the dorsal respiratory expansion, is densely ciliated and mucosecretory. These characteristics may aid in the establishment of a respiratory current and in the prevention of gill damage during escape responses. All nonciliated regions of the gill filaments are covered with microvilli, thus greatly increasing the surface area of the gill. The feeding mechanism is discussed in relation to the dorsal and ventral ciliated tracts. Symbiotic ciliate protozoans are constantly dislodged from the gill filaments and transported via the ventral mucus string to the buccal region. The nutritional implications of these observations are discussed.     

Electrochemical degradation of the dye indigo carmine at boron-doped diamond anode for wastewaters remediation

Here we demonstrate that anodic oxidation with a boron-doped diamond (BDD) electrode can be applied to the remediation of wastewaters containing indigo carmine. This environmentally friendly method decontaminates completely acid and alkaline aqueous solutions of this dye. The degradation rate increases with increasing current and dye concentration. Indigo carmine is more rapidly removed in alkaline than in acid medium, but its kinetics does not follow a defined reaction order. Isatin 5-sulfonic acid is the main aromatic product formed. Oxalic and oxamic acids are generated as ultimate carboxylic acids. The nitrogen of the dye is converted into NH₄ ⁺ and NO₃ ⁻.     

Effect of delayed first feeding on larval performance of the spider crab Maja brachydactyla assessed by digestive enzyme activities and biometric parameters

The effect of food deprivation on larval performance of the spider crab Maja brachydactyla was studied in terms of survival, moulting capacity, size, weight and enzymatic activities. Five feeding treatments that differed in the initial age of first feeding larvae (fed from hatching, 2, 4 and 6 days post-hatching and unfed) were tested for 20 days. Newly hatched larvae kept without food supply lasted for 10 days and did not moult; with 50% survival observed at 6 days post-hatching. Larvae (zoea I stage) were only able to tolerate 2 days of food deprivation after the onset of exogenous feeding without their performance being compromised. Multivariate analyses suggest that digestive enzyme activities may be good indicators of the nutritional condition of larvae.     

A landscape ecology assessment of land-use change on the Great Plains-Denver (CO,USA) metropolitan edge

Regional Environmental Change - For better or worse, in those parts of the world with a widespread farming, livestock rising, and urban expansion, the maintenance of species richness and ecosystem...     

Vegetation structure constrains primary production response to water availability in the Patagonian steppe

Grassland aboveground net primary production (ANPP) increases linearly with precipitation in space and time, but temporal models relating time series of ANPP and annual precipitation for single sites show lower slopes and regression coefficients than are shown by spatial models. The analysis of several ANPP time series showed lags in the ecosystem response to increased water availability, which may explain the difference between spatial and temporal models. The lags may result from constraints that ecosystems experience after drought. Our objective was to explore the structural constraints of the ANPP response to rainfall variability in a semiarid ecosystem, the Patagonian steppe, in southern Argentina. We designed a 3-yr rainfall manipulation experiment where we decreased water input with rainout shelters during two consecutive years, which included three levels of rainfall interception (30%, 55%, and 80%) and a control. In the third year, we irrigated one-half of the plots of each rainfall-interception treatment. We evaluated the immediate effects of drought on current-year ANPP and the effects of previous-year drought on vegetation recovery after water supplementation. ANPP (g x m(-2) x yr(-1)) was linearly related to annual precipitation input (APPT; mm/yr) along the experimental precipitation gradient (ANPP = 0.13 x APPT + 58.3; r2 = 0.34, P < 0.01), and this relationship was mostly accounted for by changes in the ANPP of grasses. Plant density (D; no. individuals/mm2) was related to the precipitation received during the drought period (D = 0.11 x APPT + 18; r2 = 0.39, P < 0.05). The recovery of plants after irrigation was lower for those plots that had experienced experimental drought the previous years relative to controls, and the lags were proportional to the intensity of drought. Therefore, our results suggest that the density of plants may constrain the recovery of vegetation after drought, and these constraints may determine lags that limit the capacity of the ecosystem to take advantage of wet years after dry years.