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Abstract: We report here a new analytical methodology for the investigation of toluene photocatalytic removal at indoor-relevant concentration level (ppbv). Experiments were performed using an annular flow-through reactor with TiO2 as photocatalyst, toluene as a model VOC and under different ranges of relative humidity (RH: 0–70%), inlet concentration (20–400ppbv) and flow rate (70–350mLmin−1). Analysis of reaction intermediates was conducted using an automated thermal desorption technique coupled to GC–MS instrument (ATD–GC–MS) whereas a GC coupled to pulsed discharge helium ionization detector (GC–PDPID) was used for the first time for on-line measurements of CO and CO2 at ppbv level. Under these conditions, toluene conversion was up to 90–100% with a slight influence of inlet concentration and RH, whereas flow rate was found to be a prevalent factor. Mineralization (%) varied from 55 to 95% and has shown to be strongly inhibited by the increase of RH whereas flow rate and inlet concentration exhibited a negligible effect. The reaction intermediates were found to be different according to the RH level: in absence of water vapor, traces of low molecular weight carbonyls (formaldehyde, methyl glyoxal, etc.) were detected and quantified in the gas phase whereas at RH 40%, hydroxylated intermediates such as cresols and benzyl alcohol were observed. On the basis of identification results, a reaction mechanism was proposed involving mainly direct hole oxidation at dry conditions and hydroxylation by OH radicals at high RH level. [Copyright &y& Elsevier]

Abstract: The photocatalytic degradation of a sulfonylurea herbicide, iodosulfuron methyl ester (IOME), has been studied in TiO2 aqueous suspensions under UV irradiation. The influence of various parameters such as initial concentration, TiO2 concentration and light intensity on the kinetic process was investigated. Disappearance rate of iodosulfuron followed pseudo-first order kinetics. A special attention was devoted to the identification of intermediates, using a new analytical approach which consists of coupling HPLC–DAD (UV), HPLC–ESI-MS and HPLC–1H NMR techniques after a SPE pre-concentration step. By combining UV, MS and NMR data, up to 20 degradation products were unambiguously identified. Furthermore, 1H NMR data allowed the differentiation of several positional isomers, in particular those of hydroxylation resulting from the attack of OH radicals on the benzene ring of IOME. Kinetic evolution profiles of main intermediates, end products (NO3 −, NH4 +, SO4 2−) and total organic carbon (TOC) were also examined in detail. From obtained kinetic and analytical results, the presence of privileged sites for the attack of OH radicals was shown and a detailed degradation pathway was proposed. [Copyright &y& Elsevier]

By means of a wetted-wall flow tube, we studied the multiphase chemistry of ozone on aqueous solutions containing fulvic acids (FA), taken as proxies for atmospheric "humic like substances", so-called HULIS. In these experiments, the loss of gaseous O3 was monitored by UV-visible absorption spectroscopy at the reactor outlet (i.e., after contact between the gaseous and liquid phases). Measurements are reported in terms of dimensionless uptake coefficients (γ) in the range from 1.6 × 1011 to 1.3 × 1011 depending on ozone gas phase concentration (in the range from 6.6 to 34.4 × 1011 molecules cm-3) and fulvic acid aqueous concentration (in the range from 0.25 to 2.5 mg L-1) and pH (in the range from 2.5 to 9.2). The measured kinetics were observed to follow a Langmuir-Hinshelwood type mechanism, in which O3 first adsorbs on the liquid surface and then reacts with the Fulvic Acid molecules. The reported uptake coefficients are greatly increased over those measured on pure water, demonstrating that the presence in solution of fulvic acids does greatly. enhance the uptake kinetics. Accordingly, the chemical interactions of fulvic acids (or HULIS) may be a driving force for the uptake of ozone on liquid organic aerosols and can also represent an important mechanism for the O3 deposition to the rivers and lakes. [ABSTRACT FROM AUTHOR]

Climate change is expected to increase drought frequency and intensity which will threaten plant growth and survival. In such fluctuating environments, perennial plants respond with hydraulic and biomass adjustments, resulting in either tolerant or avoidant strategies. Plants' response to stress relies on their phenotypic plasticity. The goal of this study was to explore physiology of young Populus nigra in the context of a time‐limited and progressive water deficit in regard to their growth and stress response strategies. Fourteen French 1‐year‐old black poplar genotypes, geographically contrasted, were subjected to withholding water during 8 days until severe water stress. Water fluxes (i.e. leaf water potentials and stomatal conductance) were analyzed together with growth (i.e. radial and longitudinal branch growth, leaf senescence and leaf production). Phenotypic plasticity was calculated for each trait and response strategies to drought were deciphered for each genotype. Black poplar genotypes permanently were dealing with a continuum of adjusted water fluxes and growth between two extreme strategies, tolerance and avoidance. Branch growth, leaf number and leaf hydraulic potential traits had contrasted plasticities, allowing genotype characterization. The most tolerant genotype to water deficit, which maintained growth, had the lowest global phenotypic plasticity. Conversely, the most sensitive and avoidant genotype ceased growth until the season's end, had the highest plasticity level. All the remaining black poplar genotypes were close to avoidance with average levels of traits plasticity. These results underpinned the role of plasticity in black poplar response to drought and calls for its wider use into research on plants' responses to stress. [ABSTRACT FROM AUTHOR]