Photocatalytic abatement results from a model street canyon

During the European Life+ project PhotoPAQ (Demonstration of Photocatalytic remediation Processes on Air Quality), photocatalytic remediation of nitrogen oxides (NOx), ozone (O3), volatile organic compounds (VOCs), and airborne particles on photocatalytic cementitious coating materials was studied in an artificial street canyon setup by comparing with a colocated nonactive reference canyon of the same dimension (5 × 5 × 53 m). Although the photocatalytic material showed reasonably high activity in laboratory studies, no significant reduction of NOx, O3, and VOCs and no impact on particle mass, size distribution, and chemical composition were observed in the field campaign. When comparing nighttime and daytime correlation plots of the two canyons, an average upper limit NOx remediation of ≤2% was derived. This result is consistent only with three recent field studies on photocatalytic NOx remediation in the urban atmosphere, whereas much higher reductions were obtained in most other field investigations. Reasons for the controversial results are discussed, and a more consistent picture of the quantitative remediation is obtained after extrapolation of the results from the various field campaigns to realistic main urban street canyon conditions.

Construction of a photocatalytic de-polluting field site in the Leopold II tunnel in Brussels

Within the framework of the European Life+-funded project PhotoPAQ (Demonstration of Photocatalytic remediation Processes on Air Quality), which was aimed at demonstrating the effectiveness of photocatalytic coating materials on a realistic scale, a photocatalytic de-polluting field site was set up in the Leopold II tunnel in Brussels, Belgium. For that purpose, photocatalytic cementitious materials were applied on the side walls and ceiling of selected test sections inside a one-way tunnel tube. This article presents the configuration of the test sections used and the preparation and implementation of the measuring campaigns inside the Leopold II tunnel. While emphasizing on how to implement measuring campaigns under such conditions, difficulties encountered during these extensive field campaigns are presented and discussed. This included the severe de-activation observed for the investigated material under the polluted tunnel conditions, which was revealed by additional laboratory experiments on photocatalytic samples that were exposed to tunnel air. Finally, recommendations for future applications of photocatalytic building materials inside tunnels are given.

The Gas-phase Ozonolysis of 1-Penten-3-ol, (Z)-2-Penten-1-ol and 1-Penten-3-one: Kinetics, Products and Secondary Organic Aerosol Formation

The gas-phase ozonolysis of the biogenic unsaturated compounds 1-penten-3-ol, (Z)-2-penten-1-ol and 1-penten-3-one has been investigated in two atmospheric simulation chambers. The following rate coefficients (in units of 10−17 cm3 molecule−1 s−1) were determined at atmospheric pressure and 293±2 K using an absolute rate method: 1-penten-3-ol, (1.64±0.15); (Z)-2-penten-1-ol, (11.5±0.66); 1-penten-3-one, (1.17±0.15). Reaction products were identified by in situ FTIR spectroscopy and gas chromatography – mass spectrometry (GC-MS). The major products and their average molar yields in the presence of a radical scavenger at relative humidity < 1% were: formaldehyde (0.49±0.02), 2-hydroxybutanal (0.46±0.03) and propanal (0.15±0.02) from 1-penten-3-ol; propanal (0.39±0.03) and glycolaldehyde (0.43±0.04) from (Z)-2-penten-1-ol; formaldehyde (0.37±0.02) and 2-oxobutanal (0.49±0.03) from 1-penten-3-one. The formation of secondary organic aerosol was also observed with yields ranging from 0.13–0.17 for the unsaturated alcohols. Significantly lower yields of around 0.03 were measured for 1-penten-3-one. The results of this work are used to determine atmospheric lifetimes and reaction mechanisms for the gas-phase ozonolysis of 1-penten-3-ol, (Z)-2-penten-1-ol and 1-penten-3-one. The broader atmospheric implications of this work are also discussed.

Development of a supercritical fluid extraction-gas chromatography-mass spectrometry method for the identification of highly polar compounds in secondary organic aerosols formed from biogenic hydrocarbons in smog chamber experiments

A new one-step method for the analysis of highly polar components of secondary organic aerosols (SOA) has been developed. This method should lead to a better understanding of SOA formation and evolution since it enables the compounds responsible for SOA formation to be identified. Since it is based on supercritical fluid extraction coupled to gas chromatography-mass spectrometry, it minimizes the analysis time and significantly enhances sensitivity, which makes it suitable for trace-level compounds, which are constituents of SOA. One of the key features of this method is the in situ derivatisation step: an online silylation allowing the measurement of highly polar, polyfunctional compounds, which is a prerequisite for the elucidation of chemical mechanisms. This paper presents the development of this analytical method and highlights its ability to address this major atmospheric issue through the analysis of SOA formed from the ozonolysis of a biogenic hydrocarbon (sabinene). Ozonolysis of sabinene was performed in a 6 m3 Teflon chamber. The aerosol components were derivatised in situ. More than thirty products, such as sabinaketone, sabinic acid and other multifunctional compounds including dicarboxylic acids and oxoacids, were measured. Nine of them were identified and quantified. The sensitivity and the linearity (0.91<R<0.98) of the method were both good and detection limits ranged from 1.2 to 6.4 ng for the investigated compounds.

Experimental and theoretical study of the reaction of OH radical with sabinene

The gas phase sabinene + OH reaction is studied both experimentally and theoretically. Product yields from the reaction of sabinene with OH radicals have been measured in the absence of NOx in the UCC chamber (Cork, Ireland) and in the presence of NOx in the LISA chamber. Three primary carbonyl compounds were observed and quantified: acetone in [(24 +/- 6)%], formaldehyde in [(25 +/- 6)%] and sabinaketone in [(20 +/- 6)%]. The simultaneous quantification of these compounds is one of the major results of this work. The mechanism of product formation for this reaction has been studied using the quantum chemical DFT-B3LYP (6-31G(d,p) method. According to these calculations, the H-atom abstraction channel from sabinene by OH in the initial oxidation step may be taken into account to explain the acetone production. Sabinaketone and formaldehyde are mainly products of the addition channels of OH on the -C=CH2 double bond of sabinene. This is the first theoretical work on the title reaction.

Kinetic and mechanistic study of the atmospheric oxidation by OH radicals of allyl acetate

Acetates are emitted into the atmosphere by several anthropic and natural sources. To better evaluate the environmental impact of these compounds, OH-induced oxidation kinetic and mechanism of allyl acetate (CH3C(O)OCH2-CH=CH2) have been investigated at room temperature and atmospheric pressure using three environmental chambers: an indoor Teflon-film bag (LISA, Créteil), an indoor Pyrex photoreactor (LISA, Créteil), and the outdoor Smog chamber EUPHORE (Valencia). Rate constant of the reaction of allyl acetate with OH radicals was determined by relative rate technique in the indoor Teflon-film bag. It is (30.6 +/- 3.1) x 10(-12) cm3 molecule-1 s-1. Mechanistic experiments were performed in the indoor photoreactor and in the outdoor Smog chamber EUPHORE. The main oxidation products observed by FTIR in both chambers were acetoxyacetaldehyde and formaldehyde. From these data, a mechanism was developed to describe the OH-induced oxidation of this acetate in the presence of NOx. Finally, atmospheric impact of allyl acetate emissions was evaluated using kinetic and mechanistic results.

Multiple-pass cell for very-long-path infrared spectrometry

A multiple-pass cell for mid-IR spectrometry that has been designed to operate in an evacuable environmental chamber is described. Using this new modified White arrangement, we can significantly increase the path length while keeping the spectrometric beam stable. An approximate expression that ties the number of reflections to the optimal signal-to-noise ratio in multiple-reflection cells is derived.

[Hyperthyroidism induced by molar pregnancy]

A case is reported of a Senegalese patient admitted for hydatiform mole. The serum human chorionic gonadotrophin concentration (hCG) was 900,000 UI.l-1. The patient was recognized to be clinically hyperthyroid with raised T4 and T3 values, but a very low TSH concentration. After two days of beta adrenergic blockade and carbimazole, a suction curettage was performed under general anaesthesia. Propranolol was again administered 6 hours after the surgery. Thyroid function returned to normal level two weeks after removal of the mole, suggesting that hCG was responsible for the thyrotoxicosis. Serum hCG concentrations closely paralleled those of free thyroxine, but the correlation was difficult to assess because of carbimazole. Clinical thyrotoxicosis is rare in molar pregnancy. The diagnosis being made in semi-urgent conditions, this raises the question of how to obtain rapid stabilization of the disease before surgery.

[Post-traumatic hyperthyroxinemia or hyperthyroidism]

A fifteen year-old girl presented with several fractures after a road traffic accident. Five days later, fat embolism occurred, complicated by adult respiratory distress syndrome (ARDS) and disseminated coagulation (DIC). She was successfully managed in the intensive therapy unit, and was transferred to a general surgery after five weeks. Tachycardia and fever persisted without any other sign of infection. Clinical examination showed exophthalmos and a thyroid murmur. The venous concentration of T4 was increased: 204 nmol . 1(-1) (N: 70-150), whereas that of T3 was normal: 2.3 nmol . 1(-1) (N: 1-1.25). No other investigations were performed. The regression of clinical symptoms and a normalization of T4 were seen after treatment (carbimazole and acebutolol). Post-traumatic hyperthyroidism is discussed. Although classical, this syndrome was not well documented, as was shown in the literature survey. After trauma or an acute illness, an early fall in thyroid hormone concentrations was usually seen; a late increase in T4 was a rare occurrence.

[Circulatory arrest in the operating room in a patient with a congenital long QT syndrome]

Reversible cardiocirculatory arrest was observed during orthopaedic treatment of a digital dislocation in a 37 year old female patient. Cardiological studies showed a prolonged QT interval (0.6 s) in the patient and her daughter, associated with hypokalemia (3.4 mmol) in the former. The diagnosis suggested was that of Romano-Ward's syndrome. Preparation and choice of anaesthesia are discussed.