Photo-fenton assisted reaction of dimethoate in aqueous solutions

The photo-Fenton reaction of an organophosphorus insecticide, dimethoate (O,O-dimethyl methylcarbamoylmethyl phosphorodithioate), was studied by following the identification and determination of the decomposition products and the total carbon removal rate. The reactions were performed in a batch recycle reactor, at room temperature, using UV radiation, H2O2 as oxidant, and FeCl3 x 6H2O as catalyst. The oxidation results were determined with a total organic carbon (TOC) analyzer and ion chromatography. The presence of reaction products was identified by gas chromatography-mass spectrometry (GC-MS). Apart from the sulfate, phosphate, and ammonium ions, the presence of dimethyl phosphite, N-methyl-acetamide, and formic acid was also detected. Excess of H2O2 concentration did not influence the reaction rate. The expression for the total carbon removal was assessed and the TOC removal rate constants were calculated.     

Speciated hydrocarbon and carbon monoxide emissions from an internal combustion engine operating on methyl tertiary butyl ether-containing fuels

In the present work, engine and tailpipe (after a three-way catalytic converter) emissions from an internal combustion engine operating on two oxygenated blend fuels [containing 2 and 11% weight/weight (w/w) methyl tertiary butyl ether (MTBE)] and on a nonoxygenated base fuel were characterized. The engine (OPEL 1.6 L) was operated under various conditions, in the range of 0-20 HP. Total unburned hydrocarbons, carbon monoxide, methane, hexane, ethylene, acetaldehyde, acetone, 2-propanol, benzene, toluene, 1,3-butadiene, acetic acid, and MTBE were measured at each engine operating condition. As concerns the total HC emissions, the use of MTBE was beneficial from 1.90 to 3.81 HP, which were by far the most polluting conditions. Moreover, CO emissions in tailpipe exhaust were decreased in the whole operation range with increasing MTBE in the fuel. The greatest advantage of MTBE addition to gasoline was the decrease in ethylene, acetaldehyde, benzene, toluene, and acetic acid emissions in engine exhaust, especially when MTBE content in the fuel was increased to 11% w/w. In tailpipe exhaust, the catalyst operation diminished the observed differences. Ethylene, methane, and acetaldehyde were the main compounds present in exhaust gases. Ethylene was easily oxidized over the catalyst, while acetaldehyde and methane were quite resistant to oxidation.     

Impact of climate change and seasonal trends on the fate of Arctic oil spills

We investigated the effects of a warmer climate, and seasonal trends, on the fate of oil spilled in the Arctic. Three well blowout scenarios, two shipping accidents and a pipeline rupture were considered. We used ensembles of numerical simulations, using the OSCAR oil spill model, with environmental data for the periods 2009–2012 and 2050–2053 (representing a warmer future) as inputs to the model. Future atmospheric forcing was based on the IPCC’s A1B scenario, with the ocean data generated by the hydrodynamic model SINMOD. We found differences in “typical” outcome of a spill in a warmer future compared to the present, mainly due to a longer season of open water. We have demonstrated that ice cover is extremely important for predicting the fate of an Arctic oil spill, and find that oil spills in a warming climate will in some cases result in greater areal coverage and shoreline exposure.     

Photocatalytic degradation of C5–C7 alkanes in the gas–phase

The gas-phase photocatalytic oxidation (PCO) of pentane, i-pentane, hexane, i-hexane and heptane over illuminated titanium at ambient temperatures was studied in a continuous stirring-tank reactor and for different values of VOC feed concentrations and relative humidity levels. Conversions achieved were over 90% for residence times from 50 to 85 s and the only products formed were CO₂ and H₂O, while no catalyst deactivation was observed. The obtained results indicate that the molecular and stereochemical structures of the compounds play an important role in the reaction, as the rate was increasing with higher molecular weight, and the presence of a tertiary carbon atom enhanced the reactivity. It was also observed that the increase of the carbon chain by a methyl group had the same influence in the reaction rate in the case of both pentane and i-pentane, while the ratio of the rates for the linear and branched structure was the same for both C₅ and C₆ isomers. The presence of water in the system had an inhibitory effect in all cases. The PCO kinetics was well fit by a Langmuir–Hinshelwood model, modified so as to take into consideration the influence of water vapour. The rate constants ranged from 1.87 × 10^?7 mol m^?2 s^?1 for pentane to 3.03 × 10^?7 mol m^?2 s^?1 for heptane, and the VOC adsorption constants from 1.14 10⁴ to 2.83 10⁴ m³ mol^?1, while the water adsorption constant was 11.2 m³ mol^?1.     

Oil spill response capabilities and technologies for ice-covered Arctic marine waters: A review of recent developments and established practices

Renewed political and commercial interest in the resources of the Arctic, the reduction in the extent and thickness of sea ice, and the recent failings that led to the Deepwater Horizon oil spill, have prompted industry and its regulatory agencies, governments, local communities and NGOs to look at all aspects of Arctic oil spill countermeasures with fresh eyes. This paper provides an overview of present oil spill response capabilities and technologies for ice-covered waters, as well as under potential future conditions driven by a changing climate. Though not an exhaustive review, we provide the key research results for oil spill response from knowledge accumulated over many decades, including significant review papers that have been prepared as well as results from recent laboratory tests, field programmes and modelling work. The three main areas covered by the review are as follows: oil weathering and modelling; oil detection and monitoring; and oil spill response techniques.     

Speciated Hydrocarbon and Carbon Monoxide Emissions from an Internal Combustion Engine Operating on Methyl Tertiary Butyl Ether-Containing Fuels

ABSTRACT

In the present work, engine and tailpipe (after a three-way catalytic converter) emissions from an internal combustion engine operating on two oxygenated blend fuels [containing 2 and 11% weight/weight (w/w) methyl tertiary butyl ether (MTBE)] and on a nonoxygenated base fuel were characterized. The engine (OPEL 1.6 L) was operated under various conditions, in the range of 0-20 HP. Total unburned hydrocarbons, carbon monoxide, methane, hexane, ethylene, acetaldehyde, acetone, 2-propanol, benzene, toluene, 1,3-butadiene, acetic acid, and MTBE were measured at each engine operating condition. As concerns the total HC emissions, the use of MTBE was beneficial from 1.90 to 3.81 HP, which were by far the most polluting conditions. Moreover, CO emissions in tailpipe exhaust were decreased in the whole operation range with increasing MTBE in the fuel.

The greatest advantage of MTBE addition to gasoline was the decrease in ethylene, acetaldehyde, benzene, toluene, and acetic acid emissions in engine exhaust, especially when MTBE content in the fuel was increased to 11% w/w. In tailpipe exhaust, the catalyst operation diminished the observed differences. Ethylene, methane,and acetaldehyde were the main compounds present in exhaust gases. Ethylene was easily oxidized over the catalyst,while acetaldehyde and methane were quite resistant to oxidation.