Etienne Quivet

Emission characteristics of air pollutants from incense and candle burning in indoor atmospheres

Volatile organic compounds (VOCs) and particles emitted by incense sticks and candles combustion in an experimental room have been monitored on-line and continuously with a high time resolution using a state-of-the-art high sensitivity-proton transfer reaction-mass spectrometer (HS-PTR-MS) and a condensation particle counter (CPC), respectively. The VOC concentration–time profiles, i.e., an increase up to a maximum concentration immediately after the burning period followed by a decrease which returns to the initial concentration levels, were strongly influenced by the ventilation and surface interactions. The obtained kinetic data set allows establishing a qualitative correlation between the elimination rate constants of VOCs and their physicochemical properties such as vapor pressure and molecular weight. The emission of particles increased dramatically during the combustion, up to 9.1(±0.2) × 104 and 22.0(±0.2) × 104 part cm−3 for incenses and candles, respectively. The performed kinetic measurements highlight the temporal evolution of the exposure level and reveal the importance of ventilation and deposition to remove the particles in a few hours in indoor environments.

The persistence of pesticides in atmospheric particulate phase: An emerging air quality issue.

The persistent organic pollutants (POPs) due to their physicochemical properties can be widely spread all over the globe; as such they represent a serious threat to both humans and wildlife. According to Stockholm convention out of 24 officially recognized POPs, 16 are pesticides. The atmospheric life times of pesticides, up to now were estimated based on their gas-phase reactivity. It has been only speculated that sorption to aerosol particles may increase significantly the half‐lives of pesticides in the atmosphere. The results presented here challenge the current view of the half-lives of pesticides in the lower boundary layer of the atmosphere and their impact on air quality and human health. We demonstrate that semivolatile pesticides which are mostly adsorbed on atmospheric aerosol particles are very persistent with respect to the highly reactive hydroxyl radicals (OH) that is the self-cleaning agent of the atmosphere. The half-lives in particulate phase of difenoconazole, tetraconazole, fipronil, oxadiazon, deltamethrin, cyprodinil, permethrin, and pendimethalin are in order of several days and even higher than one month, implying that these pesticides can be transported over long distances, reaching the remote regions all over the world; hence these pesticides shall be further evaluated prior to be confirmed as POPs.

Combustion Processes as a Source of High Levels of Indoor Hydroxyl Radicals through the Photolysis of Nitrous Acid

Hydroxyl radicals (OH) are known to control the oxidative capacity of the atmosphere but their influence on reactivity within indoor environments is believed to be of little importance. Atmospheric direct sources of OH include the photolysis of ozone and nitrous acid (HONO) and the ozonolysis of alkenes. It has been argued that the ultraviolet light fraction of the solar spectrum is largely attenuated within indoor environments, thus, limiting the extent of photolytic OH sources. Conversely, the ozonolysis of alkenes has been suggested as the main pathway of OH formation within indoor settings. According to this hypothesis the indoor OH radical concentrations span in the range of only 10(4) to 10(5) cm(-3). However, recent direct OH radical measurements within a school classroom yielded OH radical peak values at moderate light intensity measured at evenings of 1.8 × 10(6) cm(-3) that were attributed to the photolysis of HONO. In this work, we report results from chamber experiments irradiated with varying light intensities in order to mimic realistic indoor lighting conditions. The exhaust of a burning candle was introduced in the chamber as a typical indoor source causing a sharp peak of HONO, but also of nitrogen oxides (NOx). The photolysis of HONO yields peak OH concentration values, that for the range of indoors lightning conditions were estimated in the range 5.7 ×· 10(6) to 1.6 × 10(7) cm(-3). Excellent agreement exists between OH levels determined by a chemical clock and those calculated by a simple PSS model. These findings suggest that significant OH reactivity takes place at our dwellings and the consequences of this reactivity-that is, formation of secondary oxidants-ought to be studied hereafter.

Kinetic studies of imazapyr photolysis and characterization of the main photoproducts

The fate of imazapyr (2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)nicotinic acid), a broad-spectrum herbicide in the imidazolinone family, has been studied upon UV irradiation. Most of the photoproducts occurring during the photodegradation have been characterized by means of liquid chromatography and mass spectrometry coupled techniques (LC-MS). The use of high resolution mass spectrometry has allowed to maximize the chemical information obtained from a single LC-MS analysis. The degradation of a 10 ppm imazapyr solution leads to pyridine derivatives which remain in solution during 50–100 h while the imazapyr is completely degraded after 6 h.

Transfluthrin indoor air concentration and inhalation exposure during application of electric vaporizers.

Different household insecticide applications via two electric vaporizers emitting transfluthrin were realized in a full-scale experimental room under controlled air exchange rate conditions. On-line high-time resolved measurements of the gas-phase concentrations of the active substance during and immediately after the spreading periods were performed with a High Sensitivity Proton-Transfer-Reaction Mass Spectrometer (HS-PTR-MS). Experimental and modelled data from the ConsExpo 4.0 software were also compared to evaluate the sources of differences. Different application scenarios were also compared. Averaged inhaled concentrations over 1h, 1week, and 5months were estimated to be 8.3, 1.8, and 1.8μg.m(-3), respectively. Corresponding margins of exposures range from 1000 to 10,000, claiming for the absence of effect. Dermal and dust ingestion pathways, although roughly estimated, seems being non-negligible. This claims for a more in-depth integrated risk assessment.

Measurements of VOC/SVOC emission factors from burning incenses in an environmental test chamber: influence of temperature, relative humidity, and air exchange rate

This study investigates the influence of three environmental indoor parameters (i.e., temperature, relative humidity, and air exchange rate) on the emission of 13 volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs) during incense burning. Experiments have been carried out using an environmental test chamber. Statistical results from a classical two-level full factorial design highlight the predominant effect of ventilation on emission factors. The higher the ventilation, the higher the emission factor. Moreover, thanks to these results, an estimation of the concentration range for the compounds under study can be calculated and allows a quick look of indoor pollution induced by incense combustion. Carcinogenic substances (i.e., benzene, benzo(a)pyrene, and formaldehyde) produced from the incense combustion would be predicted in typical living indoors conditions to reach instantaneous concentration levels close to or higher than air quality exposure threshold values.

Adsorption of Imazamox herbicide onto Filtrasorb 400 activated carbon

Imazamox is an imidazolinone herbicide, a new class of pesticides, which can exist as cationic, anionic or neutral species in water. The adsorption isotherms of Imazamox onto Filtrasorb 400 (F400) activated carbon were determined varying the pH and the ionic strength of the aqueous medium. The results show that ionic strength has no significant effect on Imazamox uptake, contrary to pH, and that F400 has a high affinity for Imazamox. Moreover, it is found that Imazamox adsorbs onto F400 as its neutral form. The best fit of the experimental points is obtained with the Langmuir–Freundlich model, consistent with surface site heterogeneity. Finally, calculating Langmuir–Freundlich isotherms for various constant pH values, it is shown that the two plateaus observed in the experimental isotherms obtained at free pH are due to the variation of the pH along the isotherms.

Use of the HS-PTR-MS for online measurements of pyrethroids during indoor insecticide treatments

A high-sensitivity proton transfer reaction mass spectrometer (HS-PTR-MS) has been used to study the temporal evolution of pesticide concentrations in indoor environments. Because of the high time variability of the indoor air concentrations during household pesticide applications, the use of this online high time resolution instrument is found relevant. Four pyrethroid pesticides of the latest generation that are commonly found in electric vaporizer refills, namely, transfluthrin, empenthrin, tetramethrin, and prallethrin, were considered. A controlled pesticide generation system was settled and coupled to a HS-PTR-MS analyzer, and a calibration procedure based on the fragmentation patterns of the protonated molecules was performed. To illustrate the functionality of the method, measurements of the concentration–time profiles of transfluthrin contained in an electric vaporizer were carried out in a full-scale environmental room under air exchange rate-controlled conditions. This study demonstrates that the HS-PTR-MS technique can provide online and high time-resolved measurements of semi-volatile organic compounds such as pyrethroid insecticides.

Crystal and molecular structure of bis(imazapyr)diaqua copper(II)

AbstractThe imidazolinone herbicide imazapyr, 2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)nicotinic acid (H2imz) interacts with Cu(II) leading to [Cu(Himz)2(H2O)2] which crystallizes in the space group Pbca, with a = 12.5370(3) Å, b = 19.8500(5) Å, c = 22.7720(9) Å, and Z = 8. The Cu(II) atom is octahedrally surrounded by four nitrogen atoms of two Himz− anions and two water molecules. Each Himz− acts as a chelating ligand by means of N pyridine and N lactam atoms leading to five-membered chelate rings. The Cu