Treatment of phenylmercury salts by heterogeneous photocatalysis over TiO(2)

UV/TiO(2) photocatalysis of phenylmercury salts in aqueous solutions has been performed starting from both acetate (C(6)H(5)HgCH(3)CO(2), PMA) and chloride (C(6)H(5)HgCl, PMC) salts, in the presence or the absence of oxygen at acidic pH. Removal of Hg(II) in solution took place with the simultaneous deposit of dark or pale gray solids on the photocatalyst, identified as metallic Hg (when starting from PMA) or mixtures of Hg(0) and Hg(2)Cl(2) (when starting from PMC). Partial mineralization of the organic part of both compounds has also been achieved. Hg(II) removal and mineralization were enhanced in the absence of oxygen. PMA photocatalysis followed a saturation kinetics, going from first order at low concentration to zero order at higher concentrations (>0.5mM). For PMA, reaction was faster at high pH (11) with formation of mixtures of Hg and HgO. Phenol was detected as a product of the reaction in both cases, PMA and PMC, and no formation of dangerous methyl- or ethylmercury species was observed in the first case. A mechanism for the photocatalytic reaction has been proposed. The fact that calomel was found as a deposit when starting from PMC under nitrogen suggests that the mechanism of Hg(II) transformation proceeds through successive one-electron transfer reactions passing by mercurous forms.     

High-solids anaerobic digestion of municipal sludge pretreated by thermal hydrolysis

High-solids anaerobic digestion can consistently achieve 55 to 60% volatile solids destruction after thermal hydrolysis pretreatment, which reduces its viscosity and increases the fraction of soluble organic matter. For feed sludge with total solids concentrations between 6.8 and 8.2%, the process is stable at hydraulic retention times of 9 to 12 days, significantly increasing the treatment capacity of existing digesters or, in treatment plants without spare capacity, helping to postpone, reduce, or even avoid costly infrastructure investments. Process stability is related to the high concentration of soluble organic matter in the digesters. High-solids temperature-phased digestion appears to be superior to high-solids mesophilic digestion, with respect to process flexibility and stability, biosolids stabilization, and biogas generation, although ammonia inhibition may have occurred. Implementation of high-solids digestion could significantly reduce operation and maintenance costs of solids-handling operations.     

On-board emission measurement of high-loaded light-duty vehicles in Algeria

A sample of eight private gasoline and diesel conventional light-duty vehicles (LDVs) in use with various ages, carrying a load of 460 kg, were tested on a representative trip in the traffic flow of the city of Blida to obtain emission factors representing the actual use conditions of Algerian LDVs. The gas sampling system (mini-constant volume sampling) as well as the analyzers are carried on-board the vehicle. Around 55 tests were conducted during 3 months covering more than 480 km under various real driving conditions. The mean speed downtown is about 16.1 km/hr with a rather low acceleration, an average of 0.60 m/sec2. For each test, kinematics are recorded as well as the analysis of the four emitted pollutants carbon dioxide, carbon monoxide, oxides of nitrogen, and total hydrocarbons. Emission factors were evaluated according to speed for each category of gasoline and diesel engines. The influence of some parameters such as cold/hot start, age of vehicle and its state of maintenance are discussed. Results are compared with the European database ARTEMIS for comparable vehicles. These measurements contribute to the development of unit emission of the vehicles used in Algeria, which are necessary for the calculation of emission inventory of pollutants and greenhouse gases from the road transportation sector. The unit emissions constitute a tool of decisionmaking aid regarding the conception of new regulations of vehicle control and inspection in Algeria and even in similar developing countries.     

The underutilization of street markets as a source of food security indicators in famine early warning systems: a case study of Ethiopia

Famine Early Warning Systems (EWS) are reliant on data aggregated from multiple sources. Consequently, they are often insensitive to localized changes in food security status, leading to delayed response or interventions. While price and infrastructural data are often gathered, this case study suggests that local street markets and vendor knowledge are underutilized. Few efforts have been made to monitor systematically the street markets as an indicator of local stressors. Findings from Ethiopia show that knowledge generated by expanding food security indicators in this sector can be used in combination with EWS to facilitate earlier intervention in, or to monitor more effectively, on-going humanitarian crises. Indicators developed from this study are accurate, cost effective, and sensitive to local climatic and food stressors.     

Documentation of the endotoxins present in the ambient air of cotton fiber textile mills in Québec

Cotton workers are recognized as being at risk of developing occupational lung diseases. Some researchers have identified endotoxins as being a potential etiologic agent for some of the respiratory problems. This study wants to document the concentration of endotoxins found in the ambient air of textile mills where cotton fibers are handled and to identify the processing steps where the highest endotoxins concentrations in the air were found and the one where the relative limit values (RLVs) are exceeded. The 4 mills studied process cotton fibers. All the air samples were analyzed using the chromogenic Limulus Amoebocytes lysate LAL method using a kinetic detection principle based on the IRSST's standard method. In this study, a large variability in the concentrations of endotoxins in the air was observed, depending on the mill, the processing step, and the time. Despite these variations, some processes can be identified as being major generators of endotoxins in the ambient air of the mills. The highest concentrations were measured in the weaving and drawing processes and reached 10,000 EU m(-3) of air. The opening, cleaning, carding, spinning and drawing processes are the other major endotoxins generating processes with concentrations from 24 to 8,700 EU m(-3) of air. The endotoxins concentrations exceeded the RLVs for 55% of the workstations in this project. This study demonstrated that endotoxins levels in the cotton industry are high and appropriate control measures are needed.     

Evaluation of the vulnerability to contamination of drinking water systems for rural regions in Québec,Canada

The aim of this paper is to describe a method for evaluating the vulnerability of drinking water systems to contamination, in particular in rural regions used intensively for agriculture. To do so, various indicators were developed to represent the source to tap multi-barrier approach for drinking water safety. These indicators correspond to four barriers: source susceptibility to contamination; water treatment efficiency; distribution system management; and, overall management of water quality. The indicators were classified, regrouped and weighted within a model based on a multi-criteria analysis. The method was developed and applied to 39 municipal water systems of rural Quebec, Canada. The model obtained can be used for planning purposes to prioritise water systems requiring improvements.     

Environmental impacts of training activities at an air weapons range

Within Canada, it has been recognized in the last decade that military training activities may have impacts on the environmental quality of training ranges. However, impacts of activities specific to Air Force Bases have not yet been intensely documented. A hydrogeological study was accomplished at the Cold Lake Air Weapons Range, Alberta, to evaluate the environmental impacts of using bombs, rockets, strafing, and open burning/open detonation (OB/OD) on the quality of soil, ground water, surface water, and lake sediments. Samples were analyzed for metals, anions, ammonium perchlorate (NH(4)ClO(4)), and energetic materials (EM). It was found that training activities did not result in measured values being exceeded on the basis of guidance values for surface water and lake sediments. Contamination by metals was mostly limited to soils, and some metals may be related to the use of bombs (Cd, Cu, Pb), strafe (Cu), and rockets (As, Ba, Cd, Cr, Cu, Fe, Ni, Pb, U, V, Zn). TNT (2,4,6-trinitrotoluene) was the main EM found in soils, while RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) was more common in ground water. Both are related to live bombing, while nitroglycerine (NG) is related to rocket use and was detected in soils only. Aluminum, nitrate, and ammonium perchlorate detected in ground water may be related to live bombing or rockets. OB/OD operations resulted in the presence of various EM in soils, and of perchlorate and nitrate in ground water. Contamination by metals and explosives in soils was localized around the targets and varied significantly in time; however, in ground water it was more constant and may persist for a period of several years after a target has been removed.     

Effects of some environmental parameters on catalase activity measured in the mussel (Mytilus galloprovincialis) exposed to lindane

Mussels (Mytilus galloprovincialis), collected from the Bizerta lagoon, were acclimated for four days to various conditions of temperature, salinity, photoperiod and food supply and then exposed to lindane at a concentration of 40 microg l(-1). Catalase activity, which is a biomarker of exposure to an oxidative stress, was measured in the whole soft tissues of control and assay groups. In control mussels, high temperature, high salinity and light duration significantly increased catalase activity whereas this activity decreased when food, composed of freeze-dried, algae was available. When mussels were treated with lindane, catalase activities were higher than in controls. This increase was significant with temperature, salinity and light duration. The food supply did not change catalase activity, which was always higher compared to controls. Oxidative stress was shown in mussels exposed to lindane. The results highlight the need of considering abiotic parameters in biomonitoring studies, and especially when using catalase as a biomarker.     

Photoinductive efficiency of soil extracted humic and fulvic acids

Humic and fulvic acids extracted from soils of different genesis were investigated for their ability to photoinduce the transformation of fenuron (2 x 10(-4) mol(-1)) at 365 nm. The ratio of the initial rate of fenuron consumption over the rate of light absorption by humic substances was found to be higher for fulvic acids (range 2.0 x 10(-3) to 9.0 x 10(-5)) than for humic acids (range 1.7 x 10(-4) to - 3.6 x 10(-5)). Within the FAs population, this ratio decreased as the specific absorption coefficient at 365 nm increased. It seems therefore that most of 365-nm absorbing components have no photoinductive activity and even reduce that of photoinductive chromophores.