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International audience; Given that nicotine salts are a growing market, methods are needed to characterize nicotine forms in e-cigarette vaping products. By lowering the free-base nicotine fraction (αfb) in favor of protonated forms, the addition of organic acids to the e-liquid mix greatly modulates nicotine pharmacokinetics and improves vapers’ craving. This research investigated (1) the performance of pH measurement, liquid–liquid extraction (LLE), and acid/nicotine molar ratio calculation methods for αfb estimation in 6 nicotine benzoate and nicotine salicylate e-liquids and (2) nicotine protonation in the aerosol post vaporization. Aerosols were generated with a JUUL device and another mod-pod on a vaping machine to assess device effects. E-liquid and aerosol samples were then analyzed after further analytical optimization of previous methods and careful consideration of biases. Globally, performances were comparable between methods. αfb accounted for less than 5% of nicotine content regardless of experimental conditions. αfb were consistent between e-liquids and aerosols irrespective of e-cigarette devices. Hence, e-liquids are adequate surrogates for aerosols, facilitating the establishment of regulations. pH measurement is one of the most used methods and enables the establishment of relative scales for e-liquid classification but lacks automation possibility. Until now, the extent of sample dilution remained arbitrary. The dilution factor was fixed at 10, as usually achieved, since no effect of dilution was noted. pH values ranged from 5.3 to 6.3 in accordance with the literature. By contrast, LLE relies on the specificity of organic solvent for free-base nicotine extraction, causing discrepancies in previous studies. Here, the results were similar to αfb values from pH determination. Yet, LLE presented the highest variability and was the most time-consuming protocol. Finally, αfb calculation from molar ratio was the most robust and versatile method. Estimations can be made in silico from reported composition data and/or after liquid chromatography routine analysis.

International audience; Plants play a central role in the photochemistry of chemicals in the environment. They represent a major atmospheric source of volatile organic compounds (VOCs) but also an important environmental surface for the deposition and photochemical reactions of pesticides, gaseous and particulate pollutants. In this review, we point out the role of plant leaves in these processes, as a support affecting the reactions physically and chemically and as a partner through the release of natural constituents (water, secondary metabolites). We discuss the influence of the chosen support (leaves, needle surfaces or fruit cuticles, extracted cuticular waxes and model surfaces) and other factors (additives, pesticides mixture, and secondary metabolites) on the photochemical degradation kinetics and mechanisms. We also show how plants can be a source of photochemically reactive species which can act as photosensitizers promoting the photodegradation of pesticides or the formation and aging of secondary organic aerosols (SOA) and secondary organic materials (SOM). Understanding the fate of chemicals on plants is a research area located at the interface between photochemistry, analytical chemistry, atmospheric chemistry, microbiology and vegetal physiology. Pluridisciplinary approaches are needed to deeply understand these complex phenomena in a comprehensive way. To overcome this challenge, we summarize future research directions which have been clearly overlooked until now.

The effect of water on the transient kinetics of the decomposition reaction of zinc dialkyldithiophosphate (ZDDP) additive has been investigated using X-ray photoelectron spectroscopy (XPS). Water was found to have a long-lasting detrimental effect on ZDDP triboreactive film layers by changing their composition depending on their proximity to the metal surface. Particularly, water impeded the polymerisation reaction in the top layers, which results in the formation of short zinc (thio)phosphate chains. The most probable explanation for this was related to the formation of a single or multiple bridges between water molecules and PO 2 − groups of the decomposed ZDDP. This caging effect, which does not fade away as water evaporates, can suppress the chemical reactivity of these groups to a great extent, which in turn can hinder their polymerisation into long phosphate chains.

The paper explores the application of thermodynamic formalism to model and control transportation networks. Specifically, by considering the vehicles as the abstract energy supplied to the system, we show in certain circumstances that certain thermodynamic concepts such as temperature, thermal capacity and thermal equilibrium can have the corresponding notions in transportation context. In addition, despite the lack of a natural principle in transportation context that corresponds to the second law of thermodynamic as we will show, the most important thermodynamic notion, which is the entropy, can be also defined in order to measure the disorder of transportation systems. It is then shown that the state when all lanes have the same occupancy corresponds to the thermal equilibrium arising in isolated thermodynamic system. This equilibrium occupancy leads to a minimum entropy corresponding to a minimal disorder. Besides, by taking the transportation entropy as the storage function, a robust dissipativity based control strategy is presented to reduce the disorder and render the system better organized. Finally, an example is worked out to illustrate the results.

Dissolved organic matter (DOM) controls the degradation and sequestration of aquatic pollutants and, in turn, water quality. In particular, pollutant degradation is performed by oxidant species that are generated by exposure of DOM to solar light, yet, since DOM is a very complex mixture of poorly known substances, the relationships between potential oxidant precursors in DOM and their oxydative capacity is poorly known. Here, we hypothesized that production of oxidant species could be predicted using fluorescence analysis. We analysed water samples from an alluvial plain by fluorescence spectroscopy; the three-dimensional spectra were then decomposed into seven individual components using a multi-way algorithm. Components include a protein-like fluorophore, e.g. tryptophan-like and tyrosine-like, three humic fluorophores, 2-naphthoxyacetic acid, and a by-product. We compared component levels with the ability of water samples to generate reactive species under solar light. The results show a strong correlation between reactive species production and the intensity of two humic-like fluorophores assigned to reduced quinones. Monitoring these fluorophores should thus allow to predict the ability of DOM degradation of pollutants in surface waters.

International audience; Green roofs are a promising approach to mitigate air pollution in urban environments, but limited experimental data is yet available. In this study, we developed a laboratory-scale setup to measure the removal nitrogen dioxide (NO2) and ozone (O3) using a variety of common green roof species. Experiments were conducted on detached leaves and whole plants using two chambers (0.6 L and 12 L), visible lighting, NOx/O3 sources and online analyzers. Three species were the best performant (Thymus vulgaris, Sedum sexangulare and Heuchera Americana L.) with deposition velocities (νd) ranging from 1.6 to 4.82 m/h for NO2, and 1.7–5.56 m/h for O3. In both cases, thyme was the most effective plant likely due to its higher stomatal area and the reactivity of its volatile metabolites with O3 leading to several oxidized by-products. Furthermore, NO2 uptake was found to be enhanced by surface water released by leaf transpiration leading to the production of nitrous acid (HONO). Similar values of (νd) were observed (3.84–4.65 m/h) when whole thyme plant was used. The soil was also found to be competitive in removing O3 but less performant in capturing NO2. Using a dry deposition model, we estimated that the three plant species can uptake up to 9 kg/ha/year of NO2 and 13.6 kg/ha/year, which fall in agreement with previously reported modeling data. Our experimental approach can be a rapid tool for screening the depollution performances of green roof species enabling an effective prioritization for deployment in urban environments.

International audience; Plant defense inducers (PDIs) are booming and attractive protection agents designed to immunostimulate the plant to reduce subsequent pathogen colonization. The structure–PDI activity relationships of four flavan-3-ols: Epicatechin (EC), Epigallocatechin (EGC), Epicatechin gallate (ECG), Epigallocatechin gallate (EGCG) and Gallotannic acid (GTA) were investigated in both whole plant and suspension cell systems. ECG, EGCG, and GTA displayed elicitor activities. Their infiltration into tobacco leaves induced hypersensitive reaction-like lesions with topical scopoletin and PR-target transcript accumulations. On the contrary, EC and EGC infiltrations fail to trigger the biochemical changes in tobacco tissues. The tobacco BY-2 cells challenged with ECG, EGCG, or GTA led to alkalinization of the BY-2 extracellular medium while EC and EGC did not trigger any pH variation. This work provides evidence that the esterified gallate pattern is as an essential flavonoid entity to induce plant defense reactions in tobacco. The phytoprotective properties of the esterified gallate-free EC and the esterified gallate-rich GTA were evaluated on the tobacco/Phytophthora parasitica var. nicotianae (Ppn) pathosystem. Tobacco treatment with EC did not induce significant protection against Ppn compared to GTA which shows antimicrobial properties on Ppn and decreases the infection on GTA-infiltrated and -sprayed wild-type leaves. GTA protection was impaired in the transgenic NahG tobacco plants, suggesting that protection was mediated by salicylic acid.

International audience; Among the numerous studies devoted to the photodegradation of pesticides, very scarce are those investigating the effect of plant volatiles. Yet, pesticides can be in contact with plant volatiles after having been spread on crops or when they are transported in surface water, making interactions between the two kind of chemicals possible. The objectives of the present study were to investigate the reactions occuring on plants. We selected thyme as a plant because it is used in green roofs and two pesticides : the fungicide chlorothalonil for its very oxidant excited state and the insecticide imidacloprid for its ability to release the radical NO 2 under irradiation. Pesticides were irradiated with simulated solar light first in a solvent ensuring a high solubility of pesticides and plant volatiles, and then directly on thyme's leaves. Analyses were conducted by headspace gas chromatography-mass spectrometry (HS-GC-MS), GC-MS and liquid chromatography-high resolution mass spectrometry (LC-HRMS). In acetonitrile, chlorothalonil photosensitized the degradation of thymol, -pinene, 3-carene and linalool with high quantum yields ranging from 0.35 to 0.04, and was photoreduced, while thymol underwent oxidation, chlorination and dimerization. On thyme's leave, chlorothalonil was photoreduced again and products arising from oxidation and dimerization of thymol were detected. Imidacloprid photooxidized and photonitrated thymol in acetonitrile, converting it into chemicals of particular concern. Some of these chemicals were also found when imidacloprid was irradiated dispersed on thyme's leaves. These results show that photochemical reactions between pesticides and the plants secondary metabolites 2 can take place in solution as on plants. These findings demonstrate the importance to increase our knowledge on these complex scenarios that concern all the environmental compartments.

In this study, we reveal the capacity of imidacloprid (a neonicotinoid insecticide) to photoinduce the nitration and nitrosation of three aromatic probes (phenol, resorcinol, and tryptophan) in water. Using a gas-flow reactor and a NO

Humic substances (HS) play an important role in the phototransformation of micro-pollutants in surface waters and a significant part of this reactivity is often attributed to oxidant triplet excited states (3HS*). The present study aims to understand why 3HS* were found to be negligibly involved in the HS-mediated phototransformation of β2-adrenoceptor agonist terbutaline (TBL) while this chemical shows a high reactivity towards triplet 3-carboxybenzophenone (3CBP*), a typical HS model sensitizer. To clarify this apparent discrepancy, several experiments were conducted. We first confirmed that TBL can be easily oxidized by triplet riboflavin (3RF*), another sensitizer (k = (1.7 ± 0.4) × 109 M−1 s−1). Afterwards, we studied the effect of TBL on the HS-mediated phototransformation of 2,4,6-trimethylphenol (TMP), chosen for its high reactivity with 3HS*. TBL was found to enhance the rate of TMP loss. This result is rationalized by postulating that (i) TMP and TBL are both oxidized by 3HS* to yield the phenoxyl radicals TMP-H• and TBL-H•, respectively, and (ii) TBL-H• is further reduced by TMP which generates additional TMP-H•. Fitting the experimental data gives k = (1.8 ± 0.5) × 109 M−1 s-1 for the reaction between 3HS* and TBL and DFT calculations further support the conclusion that TBL-H• can be reduced by a lot of phenols. Hence, in the case of TBL, the oxidant effect of 3HS* is counterbalanced by the antioxidant properties of HS.

Red maple leaf extracts (RME) were tested for their plant defense inducer (PDI) properties. Two extracts were obtained and compared by different approaches: RME1 using ethanol&ndash, water (30&ndash, 70%, v/v, 0.5% HCl 1N) and RME2 using pure water. Both extracts titrated at 1.9 g L&minus, 1 in polyphenols and infiltrated into tobacco leaves efficiently induced hypersensitive reaction-like lesions with topical accumulation of auto-fluorescent compounds noted under UV and scopoletin titration assays. The antimicrobial marker PR1, &beta, &minus, 1,3-glucanase PR2, chitinase PR3, and osmotin PR5 target genes were all upregulated in tobacco leaves following RME1 treatment. The alkaline hydrolysis of RME1 and RME2 combined with HPLC titration of gallic acid revealed that gallate functions were present in both extracts at levels comprised between 185 and 318 mg L&minus, 1. HPLC-HR-MS analyses and glucose assay identified four gallate derivatives consisting of a glucose core linked to 5, 6, 7, and 8 gallate groups. These four galloyl glucoses possessed around 46% of total gallate functions. Their higher concentration in RME suggested that they may contribute significantly to PDI activity. These findings define the friendly galloyl glucose as a PDI and highlight a relevant methodology for combining plant assays and chemistry process to their potential quantification in crude natural extracts.

In the present study, we investigated the degradation kinetics and transformation pathways of two 5-halogenosalicylic acids (5XSAs), namely, 5-chlorosalicylic acid (5ClSA) and 5-bromosalicylic acid (5BrSA) by sulfate radical (SO4•−) in a thermo-activated persulfate system. The reaction pathways and mechanisms were proposed based on laser flash photolysis (LFP) techniques, HPLC-HRMS and molecular orbital calculations. Our results revealed that efficient removal of 5XSAs could be achieved by thermo-activated persulfate, and phenoxyl radicals were found to play key roles in the primary oxidation pathways. The subsequent transformation of phenoxyl radicals included hydroxylation and coupling processes. The resulting coupling products could undergo secondary reactions with sulfate radical, including dehalogenation, decarboxylation and hydroxylation. Hydroxylated products were in turn oxidized by SO4•−, leading to the ring opening and the formation of a series of small molecular carbonyl byproducts. These processes could be responsible for the mineralization and the release of Br− or Cl−. In addition, the degradation rate constants of 5XSAs increased appreciably with increasing temperature, and higher efficiency of oxidation was observed around neutral initial pH. Moreover, degradation kinetics were found to be hardly affected by dissolved oxygen (DO), showing the possibility of applying SR-AOPs under environmental realistic conditions, not only for surface waters, but also for oxygen-deficient underground waters. The present work could increase our understanding on the reactivity and pathways of halogen phenols widely present in natural waters.

Bromoxynil (BXN, 3,5-dibromo-4-hydroxybenzonitrile) is a herbicide that is classified as a highly hazardous chemical, toxic for the reproduction. The processes and mechanisms regarding the fate of this compound in the environmental compartments subject to solar light are poorly documented. In this work, we investigated the photochemical transformation of BXN and its main photoproducts on two relevant compartments: the surface of plant leaves that are contaminated during the crop treatments and water as the medium receiving pollutions. In a first step, BXN was deposited on wax films mimicking the surface of leaves and exposed to simulated solar light. Deposited as a pure molecule, BXN was photostable whereas deposited in the presence of an ethoxylated surfactant (5–10% in weight) BXN underwent a fast photoreduction yielding 3-bromo-4-hydroxybenzonitrile (MBr) as the unique primary photoproduct. Using muconic acid as a trapping agent for bromine atoms, it was shown that photodebromination was partly homolytic with release of bromine radical. In a second step, we studied the photolyses of BXN and MBr in water, because both should be able to reach surrounding aquatic media by wash off and leaching. The primary reactions were the heterolytic replacement of Br− by OH−, but photoreduction, photooxidation and formation of adducts were also observed at higher extent of the reactions. These results demonstrate that the mechanism of phototransformation of BXN depends drastically on the medium. They also stress the potentially important role of surfactants in the fate of BXN on leaves, and the need to investigate the photochemical reactions in a wide range of conditions to cover the diversity of situations.

International audience; In this study, we evaluated for the first time the capacity of six biochars to remove gaseous ozone, adsorbed nitrate and aqueous bisphenol A (BPA). An experimental setup was developed to study the heterogeneous chemistry of ozone and nitrate on the surface of biochars. Biochars showed excellent performance in removing ozone (55 ppbv) for periods up to 24 h, and no volatile byproducts were observed during the reaction process. Challenging biochars with adsorbed nitrate led to the formation of reduced nitrogen oxides (NO and NO2) under UV irradiation. The photoreduction of nitrate was induced by the reduced carbon present in the biochars which led to the formation of nitrite followed by photoreduction to NO in the gas phase and on the surface. Adsorption capacities of biochars for removing BPA from water were also estimated. After long-term aging by ozone, BPA adsorption capacities of all biochars did not change while they were found to decrease slightly after nitrate aging. This could be attributed to partial oxidation of biochar surface as evidenced by infrared analysis and the formation of surface-hydroxyl and -carbonyl groups. This study will allow a better evaluation of biochars as promising materials for removal of air and aqueous pollutants.

Antiplatelet medication use in the perioperative period for elective surgical procedures remains controversial. We hypothesized that for elective hernioplasty, the continuation of antiplatelet agents would not increase postoperative complications. A single surgeon prospectively tracked all elective hernia repairs performed. All patients were included except those on anticoagulation therapy. Patients already on antiplatelet therapy (APT) continued their regimen throughout the perioperative period, whereas those who were not remained off antiplatelet medications. All patients had postoperative visits between 7 and 10 days at which point they were evaluated with complications documented. One thousand four patients underwent open hernia repair. Two hundred sixty-seven patients were taking APT, whereas 737 were not. The mean age of the antiplatelet group was greater than those not on APT (66 vs 51 years old, P < 0.0001). Ecchymosis occurred more frequently in the APT group than in those not on APT (9.36% vs 2.71%, P = 0.0005). This was the only statistically significant difference in postoperative complications noted between these two groups. Patients taking clopidogrel alone or a combination of aspirin and clopidogrel had a significantly higher rate of ecchymosis compared with those on other antiplatelet regiments (10%, 21.6%, and 7.4%, respectively, P = 0.047). There were no postoperative hematomas, bleeding complications, urinary retention, or any patients who required cessation of antiplatelet medications. Continuation of APT in the perioperative period for elective hernia repair did not result in an increased frequency of postoperative complications except for ecchymosis development. We conclude that the continuation of antiplatelet medications throughout the perioperative period of elective hernioplasty is safe.

The present study aimed to investigate the changes in the chemical composition, and in the optical and photooxidant properties of Suwannee River Natural Organic Matter (SRNOM) induced by UVC (254 nm) treatment. The extent of the photodegradation was first assessed by UV–visible/fluorescence spectroscopies and organic carbon analysis. An in-depth investigation of the chemical changes was also conducted using liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry after derivatizations. A series of mono, di and tricarbonyls and mono and dicarboxylic acids in C1 C6 were identified in samples irradiated from 1 to 4 h. After 3 h of irradiation, carbonyls accounted for 46% of the organic carbon remaining in solution whereas carboxylic acids represented about 2%. Then, we investigated the modifications of the photooxidant properties of SRNOM induced by these chemical changes. At 254 nm, UVC pre-irradiated SRNOM photodegraded glyphosate 29 times faster than original SRNOM and the reaction was fully inhibited by 2-propanol (5 × 10−3 M). This enhanced photooxidant properties at 254 nm toward glyphosate was therefore reasonably due to •OH radicals formation, as confirmed by additional ESR measurements. A mechanism involving a chain reaction was proposed based on independent experiments conducted on carbonyl compounds, particularly pyruvic acid and acetone. The findings of this study show that UVC pre-treatment of NOM can enhance the removal of water pollutants and suggests a possible integration of a NOM pre-activation step in engineered water treatment sytems.

The presence of inorganic ions and organic matter in natural water would cause unpredictable consequence on the oxidation efficiency and pathways of sulfate radical (SO4 −) based advanced oxidation process (SR-AOPs). In this study, the impacts of water constituents, namely, halides (including chloride (Cl−) and bromide (Br−)), bicarbonate (HCO3−) and natural organic matter (NOM) on SO4 − induced degradation of salbutamol (SAL) and terbutaline (TBL) were evaluated systematically. Our results indicated that chloride exhibited no effect on oxidation efficiencies of SAL and TBL, while Br−, HCO3− and NOM all showed inhibitory effects. Specifically, the detrimental effect of bromide was mainly attributed to the scavenging of SO4 − to form the less reactive species, Br2 −. By using laser flash photolysis (LFP), the second-order rate constants of Br2 − with SAL and TBL were estimated to be 2.1 and 3.9 × 108 M−1 s−1, respectively, much smaller than those with SO4 − (3.7 × 109 M−1 s−1 for SAL and 4.2 × 109 M−1 s−1 for TBL). Moreover, bromine addition products of SAL and TBL were detected in the presence of Br−, which were believed to be more toxic than the parent compounds. Similar to bromide, HCO3− could also quench SO4 − to generate carbonate radical (CO3 −), also less reactive than sulfate radical with SAL (4.8 × 107 M−1 s−1) and TBL (3.2 × 108 M−1 s−1). In the case of NOM, a light screening effect was regarded as the major factor responsible to the decrease of reaction rates, while sulfate radical scavenging played a very limited role. The present work would increase the awareness of secondary reactions during SR-AOPs, as more toxic products were generated in the case of bromide.

The photodegradation reactions of two typical β2-adrenoceptor agonists, salbutamol (SAL) and terbutaline (TBL), alone, and in the presence of Aldrich humic acid (AHA) or Suwannee River fulvic acid (SRFA) were investigated by steady-state photolysis experiments, laser flash photolysis (LFP), kinetic modeling and quantum calculation. AHA and SRFA (2-20 mgC L-1) accelerated the phototransformation of both SAL and TBL. For SAL, an inhibiting effect of oxygen on the photodegradation was observed that is fully consistent with the main involvement of excited triplet states of HS (3HS*). On the contrary, oxygen drastically enhanced the photodegradation of TBL showing that 3HS* were negligibly involved in the reaction. The involvement of singlet oxygen was also ruled out because of the low reaction rate constant measured between TBL and singlet oxygen. Quantum calculations were therefore performed to explore whether oxygenated radicals could through addition reactions explain the differences of reactivity of TBL and SAL in oxygen medium. Interestingly, calculations showed that in the presence of oxygen, the addition of phenoxyl on TBL led to the formation of adducts and to the loss of TBL while the same addition reaction on SAL partly regenerated the starting compound and at the end degraded SAL less efficiently. This study is of high relevance to understand the processes involved in SAL and TBL phototransformation and the photoreactivity of HS. Moreover, our findings suggest that TBL might be a promising probe molecule to delineate the role of oxygenated radicals.

International audience; This study characterized emissions from IQOS, a heated tobacco product promoted as a less harmful alternative to cigarettes. Consumable tobacco plugs were analyzed by headspace GC/MS to assess the influence of heating temperature on the emission profile. Yields of major chemical constituents increased from 4.1 mg per unit at 180 °C to 6.2 mg at 200 °C, and 10.5 mg at 220 °C. The Health Canada Intense smoking regime was used to operate IQOS in an environmental chamber, quantifying 33 volatile organic compounds in mainstream and sidestream emissions. Aldehydes, nitrogenated species, and aromatic species were found, along with other harmful and potentially harmful compounds. Compared with combustion cigarettes, IQOS yields were in most cases 1–2 orders of magnitude lower. However, yields were closer to, and sometimes higher than electronic cigarettes. Predicted users’ daily average intake of benzene, formaldehyde, acetaldehyde and acrolein were 39 μg, 32 μg, 2.2 mg and 71 μg, respectively. Indoor air concentrations were estimated for commonly encountered scenarios, with acrolein levels of concern (over 0.35 μg m–3) derived from IQOS used in homes and public spaces. Heated tobacco products are a weaker indoor pollution source than conventional cigarettes, but their impacts are neither negligible nor yet fully understood.

International audience; This study investigated the environmental fate of myrigalone A, a light absorbing natural herbicide found on leaves and fruits of Myrica gale. Myrigalone A was irradiated in water and as a dry solid deposit to simulate reactions on leaves, alone and in the presence of the terpenes generated by Myrica gale. The phototransformation was fast (t1/2 = 35 min in water). Analyses by liquid chromatography coupled to high resolution orbitrap electrospray mass spectrometry (MS) and gas chromatography-MS revealed the formation of 11 photoproducts in water and solid and 9 in gaseous phase. Some were detected in the leaf glands and oil covering the fruits of Myrica gale, which suggested that photodegradation occurred in the field. Moreover, myrigalone A photoinduced the oxidation of terpenes that in turn protected it against photolysis. This highlights the need for additional research on the effect of terpenes on the photodegradation of pesticides on vegetation.

Chemical and physical stress, weathering, organic and inorganic matter deposition, and microbial growth over time, or “aging”, affect the optical-radiative performance of building envelope materials. Natural exposure helps to quantify these effects, but it usually requires several years. Further, the contribution of the different degradation agents cannot be isolated, and results from different campaigns cannot be easily compared because of the variability in the boundary conditions producing aging. Here we present an adaptation of the protocol implemented by ASTM as D7897-18 “Standard Practice for Laboratory Soiling and Weathering of Roofing Materials to Simulate Effects of Natural Exposure on Solar Reflectance and Thermal Emittance”. The aim is to reproduce in the laboratory the changes in albedo (solar reflectance) and thermal emittance experienced by building envelope materials in European urban areas rather than in the United States. We tuned the spraying duration and weathering cycles, and we compared the UV–vis–NIR reflectances of naturally-aged specimens (48 months in Rome and Milan) of roofing and wall finish materials to those exposed to laboratory weathering and soiling. Excluding those materials that show early physical-chemical degradation, the mean absolute deviation between natural and laboratory exposure of roofing products is equal to 0.027 in albedo. This is a lower value than the differences between two natural exposure campaigns at the same site. We clearly defined the limits of application of the protocol, providing an appraisal of the repeatability of natural aging. Moreover, we identified possible improvements in the methodology to conduct both natural and laboratory exposure.

International audience; Increasing attention is being paid to the environmental fate and impact of plastics and their additives under sunlight exposure. We evaluated the photodegradation of polystyrene (PS) films (∼100 μm) containing brominated flame retardants (BFRs): decabromodiphenylether (BDE-209), tetrabromobisphenol A (TBBPA), and tetrabromobisphenol A-bis (2.3-dibromopropylether) (TBBPA-DBPE). Irradiations were performed in a solar simulator and outdoors. Infrared (IR) analyses indicated an acceleration of the photooxidation rate of fire-retarded PS films compared to pure PS with an enhancement factor of 7 for TBBPA-DBPE and TBBPA, and 10 for BDE-209. The accelerating effect was found to be correlated with the quantum yield for BFR photodegradation and its absorbance in the PS films. The presence of BFRs also modified the PS photooxidation mechanism and resulted in the formation of 14 brominated photoproducts via bromination and oxidation of PS. Furthermore, a drastic increase in chain scissions and loss of molecular weight was revealed by size exclusion chromatography. This enhanced degradation of PS led to significant leaching (15%) of oxidation products from PS films after immersion in water, and to the gas-phase emission of several volatile brominated products. Our findings suggest that fire-retarded plastics may be a source of potentially hazardous contaminants when exposed to sunlight.

International audience; In this study, we aimed to better understand the transformation mechanisms of bifenazate, a biphenyl hydrazine derivative insecticide poorly studied up to now. For this, we compared its reactivity in the dark and under simulated solar light irradiation in different media (water, non-aqueous polar solvent, surface of apolar wax films, skin of vegetable). In air-saturated pH = 5.7 water, bifenazate underwent both autoxidation in the dark (t1/2 = 34 h) and photolysis (t1/2 = 17 h). In an aprotic polar solvent such as acetonitrile, bifenazate was stable in the dark but was quickly photodegraded in the presence of oxygen (t1/2 = 2 h). The phototransformation of bifenazate was due to the oxidation of excited states by oxygen and to the cleavage of the NN bond, while the autoxidation in water started by the initial oxidation of the molecule by oxygen and involved the superoxide anion as chain carrier. On paraffinic wax film, photodegradation (t1/2 = 365 h) and dark autoxidation (t1/2 = 1600 h) were very slow. On green pepper skin, bifenazate disappeared both in the dark (t1/2 = 34 h) and through photolysis (t1/2 = 23 h) at rates close to those measured in water. This shows that on green pepper skin, bifenazate is affected by water contained in the vegetable and possibly released by transpiration. Bifenazate diazene was the major degradation product in all studied conditions. Minor byproducts were detected too. They depended on the experimental conditions showing that degradation pathways are governed by the nature and properties of the medium. In particular, on green pepper one found byproducts generated in acetonitrile and on wax by photolysis and in water by autoxidation. This finding highlights the need for a better model than wax to mimic photolysis on plant surfaces.

International audience; This work demonstrates that the fungicide thiophanate-methyl generates a sensitizing photoproduct upon irradiation in solar light and explains how the reaction proceeds. The degradation profileof aqueous thiophanate-methyl in simulated solar light showed an autoaccelerated shape indicating the formation of some photodegrading compounds. Among the detected photoproducts, I (λmax = 340 nm), a quinoxaline derivative generated in the very beginning of the reaction seemed to be the molecule responsible for this autoacceleration. Further experiments were conducted to confirm this hypothesis. The laser flash photolysis (λexc = 355 nm) of I generated a transient species reminiscent to the triplet excited state of unsubstituted quinoxaline. The two triplets reacted with the phenolic probe, 2,4,6-trimethylphenol, with k = 2 × 109 M−1 s−1. Steady-state irradiations showed that thiophanate-methyl drastically accelerated the photolysis of the probe in an auto-accelerated reaction confirming the production of a sensitizing photoproduct. Moreover, unsubstituted quinoxaline sensitized the degradation of thiophanate-methyl showing that this latter contains labile H atoms. All these data confirmed that I was the sensitizer responsible for the auto-accelerated light induced transformation of thiophanate-methyl. The mechanism of formation of I was studied by quantum calculations. It proceeds through photocyclisation to form a SS bridge, followed by intra and intermolecular H abstractions and finally departure of HSS.The sensitizing properties of micropollutants photoproducts open a large array of investigations. Our study provides a reliable approach to investigate the overlooked photosensitizing effect of photoproducts during photochemical reactions in water and opens the way to a vast array of research.

International audience; In this study, we examined the photodegradation of decabromodiphenyl ether (BDE-209) on the surface of car seat covers from end-of-life vehicles (ELVs). Samples were collected at two car dismantling facilities in Sweden and cover car models from 1989 to 1998. The content of polybrominated diphenyl ethers (PBDEs) in nine real samples (fabric and polyurethane foam) was first characterized. Fabric samples that did not contain BDE-209 were then spiked with BDE-209 and irradiated in the laboratory and under sunlight. Photoproducts were identified using high performance liquid chromatography coupled to electrospray ionization mass spectrometer (HPLC-ESI-Orbitrap-MS), whereas volatile products were analyzed by gas chromatography–mass spectrometry (GC-MS). Similar photodegradation rates and oxidation products were observed in fabric samples irradiated in the laboratory and those collected from ELVs. Estimated half-life of BDE-209 on fabric inside vehicles ranged from 3 to 6 years. Thirteen major photoproducts were identified as lower brominated products, hydroxylated BDEs, brominated and hydroxylated dibenzofurans (PBDFs) and dioxins (PBDDs). Furthermore, several photoproducts were found to be transferable into water, particularly bromophenols and hydroxylated BDEs, and others into gas phase, such as bromomethanol and 1,2-dibromoethane. This should be taken into consideration for better estimating exposure to PBDEs and to develop strategies for ELV recycling.

International audience; Brominated flame retardants (BFRs) are widely used as additives in plastics, textiles and electronics materials. Here, we investigated the photodegradation of four BFRs including decabromobiphenylether (BDE-209), tetrabromobipsphenol A (TBBPA), tetrabromobisphenol A-bis(2,3-dibromopropylether) (TBBPA-DBPE) and tetrabromobisphenol A bis (allyl) ether (TBBPA-BAE). Experiments were carried out in polystyrene (PS) films using monochromatic and polychromatic irradiations. For comparison, irradiations were also carried in a solvent (tetrahydrofuran: THF). Monitoring of BFR degradation was performed using bulk and surface infrared (IR) measurements, as well as by extraction and HPLC-UV. Photoproducts were characterized using HPLC-high resolution electrospray ionization mass spectrometry (HPLC-ESI-Orbitrap-MS).All four BFRs underwent photochemical transformation in THF at 290 nm with a quantum yield (Φ) ranging from 0.05 for TBBPA to 0.27 for BDE-209, indicating an increase of photoreactivity with the number of Br atoms in BFRs. On the other hand, no major difference in the Φ values was observed when BFRs were embedded in PS films (Φ: 0.82–0.89). The higher photoreactivity in PS appears to be associated with a fast oxidation of PS as revealed by infrared (IR) analysis and yellowing of the films. Interestingly, the faster the yellowing occurred, the faster the BFR degradation was inhibited due to light screening effect. Several major photoproducts were identified for TBBPA and TBBPA-DBPE. Additional photoproducts possibly arising from PS oxidation and bromination by Br● were observed for the first time. This work provides a better understanding of the reactivity and fate of BFRs in polymers allowing for a better assessment of their environmental impacts.

Advanced oxidation processes based on sulfate radicals (SO 4 ·− ) are capable of efficiently degrade organic pollutants from ground, surface and wastewaters. However, this degradation may be limited by aqueous natural organic matter (NOM). Here we measured the absolute rate constants of reaction of SO 4 ·− with four types of organic matter: two fulvic acids and two lake organic matter. We used laser flash photolysis technique to monitor the SO 4 ·− decay and the formation of the transients from organic matters. Reaction rate constants comprised between 1530 and 3500 s−1 mgC−1 L were obtained by numerical analysis of differential equations and the weighted average of the extinction coefficient of the generated organic matters radicals between 400 and 800 M−1 cm−1.

Reactive oxygen species (ROS), such as free radicals and peroxides, are environmental trace pollutants potentially associated with asthma and airways inflammation. These compounds are often not detected in indoor air due to sampling and analytical limitations. This study developed and validated an experimental method to sample, identify and quantify ROS in indoor air using fluorescent probes. Tests were carried out simultaneously using three different probes: 2′,7′-dichlorofluorescin (DCFH) to detect a broad range of ROS, Amplex ultra Red® (AuR) to detect peroxides, and terephthalic acid (TPA) to detect hydroxyl radicals (HO•). For each test, air samples were collected using two impingers in series kept in an ice bath, containing each 10 mL of 50 mM phosphate buffer at pH 7.2. In tests with TPA, that probe was also added to the buffer prior to sampling; in the other two tests, probes and additional reactants were added immediately after sampling. The concentration of fluorescent byproducts was determined fluorometrically. Calibration curves were developed by reacting DCFH and AuR with known amounts of H2O2, and using known amounts of 2-hydroxyterephthalic acid (HTPA) for TPA. Low detection limits (9-13 nM) and quantification limits (18-22 nM) were determined for all three probes, which presented a linear response in the range 10-500 nM for AuR and TPA, and 100-2000 nM for DCFH. High collection efficiency (CE) and recovery efficiency (RE) were observed for DCFH (CE=RE=100%) and AuR (CE=100%; RE=73%) by sampling from a laboratory-developed gas phase H2O2 generator. Interference of co-occurring ozone was evaluated and quantified for the three probes by sampling from the outlet of an ozone generator. The method was demonstrated by sampling air emitted by two portable air cleaners: a strong ozone generator (AC1) and a plasma generator (AC2). High ozone levels emitted by AC1 did not allow for simultaneous determination of ROS levels due to high background levels associated with ozone decomposition in the buffer. However, emitted ROS were quantified at the outlet of AC2 using two of the three probes. With AuR, the concentration of peroxides in air emitted by the air cleaner was 300 ppt of H2O2 equivalents. With TPA, the HO• concentration was 47 ppt. This method is best suited to quantify ROS in the presence of low ozone levels. Fil: Montesinos, Victor Nahuel. Comisión Nacional de Energía Atómica. Gerencia del Área de Seguridad Nuclear y Ambiente. Gerencia de Química (CAC); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina Fil: Sleiman, Mohamad. Clermont Université; Francia. Lawrence Berkeley National Laboratory. Environmental Energy Technologies División. Indoor Environment Group; Estados Unidos. Centre National de la Recherche Scientifique; Francia Fil: Cohn, Sebastian. Lawrence Berkeley National Laboratory. Environmental Energy Technologies División. Indoor Environment Group; Estados Unidos Fil: Litter, Marta Irene. Universidad Nacional de San Martín. Instituto de Investigación en Ingeniería Ambiental; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Seguridad Nuclear y Ambiente. Gerencia de Química (CAC); Argentina Fil: Destaillats, Hugo. Lawrence Berkeley National Laboratory. Environmental Energy Technologies División. Indoor Environment Group; Estados Unidos

This paper proposes a novel approach to control the velocity of a piston using dilatant fluid. Commonly, a pressure compensated flow control valve is used for this purpose. It produces excellent results but is mechanically complex. A setup is proposed that makes use of the unique properties of dilatant (i.e. shear thickening) non-Newtonian fluids. A simple tube section filled with dilatant material can be used to achieve very low sensitivity of flow rate vs. pressure difference. A numerical study shows how the power law which relates the fluid shear rate to its viscosity results in this low sensitivity of flow to pressure difference. An experimental setup was build to validate the findings using a cheap and commercially available shear thickening fluid. It was found that the dilatant material used does not have a highly pronounced dilatant property and therefore the sensitivity of flow vs. pressure difference was not as low as desired. Nevertheless, the results support the practical applicability of this novel type of velocity control.

This paper aims at presenting a Sliding Mode Control with constraints for urban transportation network. Firstly, by applying the store-and-forward approach, the transportation network is modeled into a linear model. Then, the controllability analysis has shown that the system is not totally controllable. Hence, it is split into controllable subsystem and uncontrollable one. Furthermore, the Sliding Mode Control is applied in order to prevent the congestion in the network and reduce the effect of disturbance. By applying the proposed traffic signal control strategy, we achieved our objective and at the same time we respected the constraints on the state and the control by means of Linear Matrix Inequality (LMI). Finally, a simulation for a network with four intersections is realized to show the performance of the results.

International audience; The photoreactivity of plant activator benzo(1,2,3)thiadiazole-7-carbothioic acid S-methyl ester (BTH), commonly named acibenzolar-S-methyl, was studied on the surfaces of glass, paraffinic wax films, and apple leaves. Experiments were carried out in a solar simulator using pure and formulated BTH (BION). Surface photoproducts were identified using liquid chromatography coupled with electrospray ionization and high-resolution Orbitrap mass spectrometry, while volatile photoproducts were characterized using an online thermal desorption system coupled to a gas chromatography–mass spectrometry (GC–MS) system. Pure BTH degraded quickly on wax surfaces with a half-life of 5.0 ± 0.5 h, whereas photolysis of formulated BTH was 7 times slower (t1/2 = 36 ± 14 h). On the other hand, formulated BTH was found to photolyze quickly on detached apple leaves with a half-life of 2.8 h ± 0.4 h. This drastic difference in photoreactivity was attributed to the nature and spreading of the BTH deposit, as influenced by the surfactant and surface characteristics. Abiotic stress of irradiated apple leaf was also shown to produce OH radicals which might contribute to the enhanced photodegradability. Eight surface photoproducts were identified, whereas GC–MS analyses revealed the formation of gaseous dimethyl disulfide and methanethiol. The yield of dimethyl disulfide ranged between 1.5% and 12%, and a significant fraction of dimethyl disulfide produced was found to be absorbed by the leaf. This is the first study to report on the formation of volatile chemicals and OH radicals during agrochemical photolysis on plant surfaces. The developed experimental approach can provide valuable insights into the heterogeneous photoreactivity of sprayed agrochemicals and could help improve dissipation models.

E-cigarettes likely represent a lower risk to health than traditional combustion cigarettes, but they are not innocuous. Recently reported emission rates of potentially harmful compounds were used to assess intake and predict health impacts for vapers and bystanders exposed passively. Vapers' toxicant intake was calculated for scenarios in which different e-liquids were used with various vaporizers, battery power settings and vaping regimes. For a high rate of 250 puff day-1 using a typical vaping regime and popular tank devices with battery voltages from 3.8 to 4.8 V, users were predicted to inhale formaldehyde (up to 49 mg day-1), acrolein (up to 10 mg day-1) and diacetyl (up to 0.5 mg day-1), at levels that exceeded U.S. occupational limits. Formaldehyde intake from 100 daily puffs was higher than the amount inhaled by a smoker consuming 10 conventional cigarettes per day. Secondhand exposures were predicted for two typical indoor scenarios: a home and a bar. Contributions from vaping to air pollutant concentrations in the home did not exceed the California OEHHA 8-h reference exposure levels (RELs), except when a high emitting device was used at 4.8 V. In that extreme scenario, the contributions from vaping amounted to as much as 12 μg m-3 formaldehyde and 2.6 μg m-3 acrolein. Pollutant concentrations in bars were modeled using indoor volumes, air exchange rates and the number of hourly users reported in the literature for U.S. bars in which smoking was allowed. Predicted contributions to indoor air levels were higher than those in the residential scenario. Formaldehyde (on average 135 μg m-3) and acrolein (28 μg m-3) exceeded the acute 1-h exposure REL for the highest emitting vaporizer/voltage combination. Predictions for these compounds also exceeded the 8-h REL in several bars when less intense vaping conditions were considered. Benzene concentrations in a few bars approached the 8-h REL, and diacetyl levels were close to the lower limit for occupational exposures. The integrated health damage from passive vaping was derived by computing disability-adjusted life years (DALYs) lost due to exposure to secondhand vapor. Acrolein was the dominant contributor to the aggregate harm. DALYs for the various device/voltage combinations were lower than - or comparable to - those estimated for exposures to secondhand and thirdhand tobacco smoke. Fil: Logue, Jennifer M.. Lawrence Berkeley National Laboratory. Environmental Energy Technologies División. Indoor Environment Group; Estados Unidos Fil: Sleiman, Mohamad. Lawrence Berkeley National Laboratory. Environmental Energy Technologies División. Indoor Environment Group; Estados Unidos. Institut de Chimie de Clermont-ferrand; Francia Fil: Montesinos, Victor Nahuel. Comisión Nacional de Energía Atómica. Gerencia del Área de Seguridad Nuclear y Ambiente. Gerencia de Química (CAC); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Russell, Marion L.. Lawrence Berkeley National Laboratory. Environmental Energy Technologies División. Indoor Environment Group; Estados Unidos Fil: Litter, Marta Irene. Universidad Nacional de San Martín. Instituto de Investigación en Ingeniería Ambiental; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Seguridad Nuclear y Ambiente. Gerencia de Química (CAC); Argentina Fil: Benowitz, Neal L.. University Of San Francisco.; Estados Unidos Fil: Gundel, Lara A.. Lawrence Berkeley National Laboratory. Environmental Energy Technologies División. Indoor Environment Group; Estados Unidos Fil: Destaillats, Hugo. Lawrence Berkeley National Laboratory. Environmental Energy Technologies División. Indoor Environment Group; Estados Unidos

SSCI-VIDE+ATARI+LZO:CFE:JMC; International audience; The present study investigated the reactivity and oxidation mechanisms of salbutamol (SAL) and terbutaline (TBL), two typical β2-adrenoceptor agonists, towards sulfate radical (SO4−) by using photo-activated persulfate (PS). The reaction pathways and mechanisms were proposed based on products identification using high resolution HPLC-ESI-MS, laser flash photolysis (LFP) and molecular orbital calculations. The results indicated that SO4− was the dominant reactive species in the UV/PS process. The second-order rate constants of sulfate radical reaction with SAL and TBL were measured as (3.7 ± 0.3) × 109 and (4.2 ± 0.3) × 109 M−1 s−1 by LFP, respectively. For both SAL and TBL, phenoxyl radicals were found to play key roles in the orientation of the primary pathways. For SAL, a benzophenone derivative was generated by oxidation of the phenoxyl radical. However, in the case of TBL, the transformation of the phenoxyl radical into benzoquinone was impossible. Instead, the addition of OSO3H on the aromatic ring was the major pathway. The same reactivity pattern was observed in the case of TBL structural analogs resorcinol and 3,5-dihydroxybenzyl alcohol. Our results revealed that basic conditions inhibited the decomposition of SAL and TBL, while, increasing PS dose enhanced the degradation. The present work could help for a better understanding of the difference in oxidation reactivity of substituted phenols widely present in natural waters.

Highly reflective roofs can decrease the energy required for building air conditioning, help mitigate the urban heat island effect, and slow global warming. However, these benefits are diminished by soiling and weathering processes that reduce the solar reflectance of most roofing materials. Soiling results from the deposition of atmospheric particulate matter and the growth of microorganisms, each of which absorb sunlight. Weathering of materials occurs with exposure to water, sunlight, and high temperatures. This study developed an accelerated aging method that incorporates features of soiling and weathering. The method sprays a calibrated aqueous soiling mixture of dust minerals, black carbon, humic acid, and salts onto preconditioned coupons of roofing materials, then subjects the soiled coupons to cycles of ultraviolet radiation, heat and water in a commercial weatherometer. Three soiling mixtures were optimized to reproduce the site-specific solar spectral reflectance features of roofing products exposed for 3 years in a hot and humid climate (Miami, Florida); a hot and dry climate (Phoenix, Arizona); and a polluted atmosphere in a temperate climate (Cleveland, Ohio). A fourth mixture was designed to reproduce the three-site average values of solar reflectance and thermal emittance attained after 3 years of natural exposure, which the Cool Roof Rating Council (CRRC) uses to rate roofing products sold in the US. This accelerated aging method was applied to 25 products–single ply membranes, factory and field applied coatings, tiles, modified bitumen cap sheets, and asphalt shingles–and reproduced in 3 days the CRRC's 3-year aged values of solar reflectance. This accelerated aging method can be used to speed the evaluation and rating of new cool roofing materials.

Author(s): Levinson, RM; chen, S; ban-weiss, G; gilbert, H; berdahl, P; rosado, P; destaillats, H; sleiman, M; kirchstetter, T | Abstract: As the least expensive category of high-slope roofing in the U.S., shingles are found on the roofs of about 80% of U.S. homes, and constitute about 80% (by product area) of this market. Shingles are also among the least reflective high-slope roofing products, with few cool options on the market. The widespread use of cool roofs in the two warmest U.S. climate zones could reduce annual residential cooling energy use in these zones by over 7%. This project targets the development of high-performance cool shingles with initial solar reflectance at least 0.40 and a cost premium not exceeding US$0.50/ft². Phase 1 of the current study explored three approaches to increasing shingle reflectance. Method A replaces dark bare granules by white bare granules to enhance the near-infrared reflectance attained with cool pigments. Method B applies a white basecoat and a cool-color topcoat to a shingle surfaced with dark bare granules. Method C applies a visually clear, NIR-reflecting surface treatment to a conventionally colored shingle. Method A was the most successful, but our investigation of Method B identified roller coating as a promising top-coating technique, and our study of Method C developed a novel approach based on a nanowire mesh. Method A yielded red, green, brown, and black faux shingles with solar reflectance up to 0.39 with volumetric coloration. Since the base material is white, these reflectances can readily be increased by using less pigment. The expected cost premium for Method A shingles is less than our target limit of $0.50/ft², and would represent less than a 10% increase in the installed cost of a shingle roof. Using inexpensive but cool (spectrally selective) iron oxide pigments to volumetrically color white limestone synthesized from sequestered carbon and seawater appears to offer high albedo at low cost. In Phase 2, we plan to refine the cool shingle prototypes, manufacture cool granules, and manufacture and market high-performance cool shingles.

Exposure to thirdhand smoke (THS) is a newly described health risk. Evidence supports its widespread presence in indoor environments. However, its genotoxic potential, a critical aspect in risk assessment, is virtually untested. An important characteristic of THS is its ability to undergo chemical transformations during aging periods, as demonstrated in a recent study showing that sorbed nicotine reacts with the indoor pollutant nitrous acid (HONO) to form tobacco-specific nitrosamines (TSNAs) such as 4-(methylnitrosamino)-4-(3-pyridyl)butanal (NNA) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). The goal of this study was to assess the genotoxicity of THS in human cell lines using two in vitro assays. THS was generated in laboratory systems that simulated short (acute)- and long (chronic)-term exposures. Analysis by liquid chromatography-tandem mass spectrometry quantified TSNAs and common tobacco alkaloids in extracts of THS that had sorbed onto cellulose substrates. Exposure of human HepG2 cells to either acute or chronic THS for 24h resulted in significant increases in DNA strand breaks in the alkaline Comet assay. Cell cultures exposed to NNA alone showed significantly higher levels of DNA damage in the same assay. NNA is absent in freshly emitted secondhand smoke, but it is the main TSNA formed in THS when nicotine reacts with HONO long after smoking takes place. The long amplicon-quantitative PCR assay quantified significantly higher levels of oxidative DNA damage in hypoxanthine phosphoribosyltransferase 1 (HPRT) and polymerase β (POLB) genes of cultured human cells exposed to chronic THS for 24h compared with untreated cells, suggesting that THS exposure is related to increased oxidative stress and could be an important contributing factor in THS-mediated toxicity. The findings of this study demonstrate for the first time that exposure to THS is genotoxic in human cell lines.

Photocatalytic oxidation (PCO) air cleaning is a promising technology suitable for the elimination of a broad range of volatile organic compounds (VOCs). However, performance of poorly designed PCO systems may be affected by the formation of volatile aldehydes and other partially oxidized byproducts. This study explored the role of key design and dimensioning parameters that influence the effective removal of primary pollutants and can help reduce or eliminate the formation of secondary byproducts. A model pollutant mixture containing benzene, toluene, o-xylene, undecane, 1-butanol, formaldehyde and acetaldehyde was introduced at a constant rate in a 20-m 3 environmental chamber operating at an air exchange rate of 1 h −1 . Individual pollutant concentrations were kept at realistically low levels, between 2 and 40 μg m −3 . A prototype air cleaner provided with flat or pleated PCO filtering media was operated in an external ductwork loop that recirculated chamber air at flow rates in the range 178–878 m 3 h −1 , corresponding to recycle ratios between 8.5 and 38. Air samples were collected upstream and downstream of the air cleaner and analyzed off-line to determine single-pass removal efficiency. The final-to-initial chamber concentration ratio was used to determine the global chamber removal efficiency for each pollutant. In the flat filter configuration, longer dwelling times of compounds on the TiO 2 surface were attained by reducing the recirculation airflow by a factor of ∼5, leading to increasing total pollutant removal efficiency from 5% to 44%. Net acetaldehyde and formaldehyde removal was achieved, the later at airflow rates below 300 m 3 h −1 , illustrating the critical importance of controlling the contact time of primary and secondary pollutants with the TiO 2 surface. The use of pleated media was shown to increase significantly the system performance by extending the dwelling time of pollutants on the irradiated surface of the PCO media, with a 70% degradation of target pollutants. With the pleated media, formaldehyde removal efficiency increased to 60%. Irradiation using either a UVC or a UVA lamp under identical flow conditions produced similar pollutant elimination. A simple correlation between the steady-state single pass removal efficiency and the global chamber removal efficiency was used to rationalize these experimental results and identify optimal operating conditions.

Traffic signal control strategies concern generally two distinct objectives: the prevention or reduction of the congestion. Traffic congestion appears when the traffic demand exceeds the capacity of the network. In this case, some lanes of the network are saturated and consequently an overflow occurs at some intersections. In this paper, we show that congestion can be avoided by forcing the number of vehicles to not exceed the level corresponding to the optimal operational traffic of each lane. By using the concept of positive invariance and Linear Matrix Inequalities (LMI), we derive a state feedback traffic light control law that achieves our objective and at the same time respecting both the constraints of state and control variables. The results of the simulations indicate that our control strategy guarantees a high degree of control benefit.