Dimitrios Kotzias

Gas-phase terpene oxidation products: a review

Abstract Terpenes are emitted in large quantities from vegetation into the troposphere, where they react readily with ozone, OH and NO3 radicals leading to a number of oxidation products. The current knowledge about gas-phase terpene oxidation products is reviewed. Their formation and decomposition pathways, their products and their relevance for the troposphere, and their chemical analysis are discussed. Data on oxidation kinetics, and product yields is presented for 23 terpenes and 65 oxidation products. A total of 84 references are quoted.

Decomposition of Terpenes by Ozone during Sampling on Tenax

The ozonolytic decomposition of terpenes and terpenoids during sampling on Tenax is investigated in an artificial air system at ambient concentration levels. The detrimental effect of 8-150 ppbv ozone depends on the chemical structure of the compounds:  saturated terpenoids such as 1,8-cineole, camphor, and bornyl acetate are unaffected by ozone. The terpenes and terpenoids which containing one C-C double bond are slightly decomposed in the order camphene < β-pinene ≈ myrtenal < α-pinene < sabinene ≈ citronellal. The compounds containing two or more double bonds are significantly decomposed in the order d-limonene ≈ citral < linalool < β-ocimene < terpinolene << α-terpinene ≈ β-caryophyllene. For α-pinene, sabinene and d-limonene, their ozonolysis products are found on the tubes:  pinonaldehyde, 5-(1-methylethyl)bicyclo[3.1.0]hexan-2-one, and 3-(1-methylethenyl)-6-oxoheptanal. The analytical recoveries are significantly enhanced for many compounds when the sampling duration is reduced from 10 min to 30 s, explained by the time available for ozonolysis. A miniature ozone scrubber with multiple layers of MnO(2)-coated copper nets was developed and thoroughly tested. The optimal number of plies is found to be 8, which ensures quantitative recoveries for all test compounds except α-terpinene, β-caryophyllene, citral, and citronellal. The results that are reported here call into question previous data on terpenes and terpenoids and/or their oxidation products where measurements have been carried out without the prior removal of ozone.

Investigation of Volatile Organic Compounds and Phthalates present in the Cabin Air of Used Private Cars

The presence of selected volatile organic compounds (VOCs) including aromatic, aliphatic compounds and low molecular weight carbonyls, and a target set of phthalates were investigated in the interior of 23 used private cars during the summer and winter. VOC concentrations often exceeded levels typically found in residential indoor air, e.g. benzene concentrations reached values of up to 149.1 microg m(-3). Overall concentrations were 40% higher in summer, with temperatures inside the cars reaching up to 70 degrees C. The most frequently detected phthalates were di-n-butyl-phthalate and bis-(2-ethylhexyl) phthalate in concentrations ranging from 196 to 3656 ng m(-3).

Product analysis of the gas-phase reaction of β-caryophyllene with ozone

Abstract The semivolatile ketoaldehydes 3,3-dimethyl-y-methylene-2-(3-oxobutyl)-cyclobutanebutanal 1 and 3,3-dimethyl-γ-oxo-2-(3-oxobutyl)-cyclobutanebutanal 2 and formaldehyde have been identified as the main products of the reaction of s-caryophyllene with ozone in the gas phase. In minor amounts 9-methylene-,t,12,12-trimethyl-5-oxabicyclo[8.2.0.0.s]dodecane 3 was also formed. Nature and yields of these carbonyl products are discussed in terms of oxidation mechanisms involving the gas-phase reaction with ozone and OH radicals.

Polyphenylenesulfide, NOXON, an Ozone Scavenger for the Analysis of Oxygenated Terpenes in Air.

Abstract During sampling, oxygenated terpenes may undergo decomposition through reaction with atmospheric ozone. We have studied their ozonolytic decomposition during preconcentration on Tenax. The saturated. terpenoids 1,8-cineole, bornyl acetate nopinone and pinonaldehyde are practically unaffected by ozone in the range of 8 to 120 ppbv. Compounds which contain one or more C-C double bonds are decomposed in the order: linalool ≈ citronellal ≈ 6-methyl-5-hepten-2-one > citral > 4-acetyl-1-methyl-cyclohexane > 3-(1-methylethenyl)-6-oxo-heptanal > myrtenal ≈ 2-methyl-3-buten-2-ol. The degree of decomposition varies from 0 to 5% for the least reactive to 80 to 90% for the most reactive compounds. A broad range of material was investigated as potential ozone scavengers. By using the polymer noXon (polyphenylenesulfide) all the investigated compounds could be sampled with quantitative recoveries even at high ozone mixing ratios (95–110 ppbv). This ozone scrubber was tested for sampling of terpene oxidation products on Tenax and dinitrophenylhydrazine impregnated C 18 -silicagel cartridges. Recoveries from 85 to 110% were obtained for all investigated compounds. The method was used for the analysis of oxidation products of terpenes in ambient air in three campaigns. Attention was focused on nopinone from β-pinene, pinonaldehyde from α-pinene, 3-(1-methylethenyl)-6-oxo-heptanal and 4-acetyl-1-methyl-cyclohexane from limonene, and 5-(1-methylethyl)-bicyclo[3.1.0] hexan-2-one from sabinene. Nopinone was the only product which could be frequently detected in ratios from 0 to 90% of the measured β-pinene concentrations. Pinonaldehyde was encountered only once (30% of α-pinene) while the other products were not found. These data have to be seen as a first attempt to measure terpene oxidation products in the troposphere.

Building materials. VOC emissions, diffusion behaviour and implications from their use

Five cement- and five lime-based building materials were examined in an environmental chamber for their emissions of Volatile Organic Compounds (VOCs). Typical VOCs were below detection limits, whereas not routinely analysed VOCs, like neopentyl glycol (NPG), dominated the cement-based products emissions, where, after 72 h, it was found to occur, in levels as high as 1400 μg m(-3), accounting for up to 93% of total VOCs. The concentrations of NPG were not considerably changed between the 24 and 72 h of sampling. The permeability of building materials was assessed through experiments with a dual environmental chamber; it was shown that building materials facilitate the diffusion of chemicals through their pores, reaching equilibrium relatively fast (6 h).

Evaluation of the Fate of the Active Ingredients of Insecticide Sprays, Used Indoors

The fate of the active ingredients of insecticide sprays after use in indoor environments was investigated. Indoor air sampling was performed through two types of adsorbents, namely, TENAX TA and XAD-2 (10 L). After sampling, both adsorbents were ultrasonically extracted and analyzed by Gas Chromatography coupled to Mass Spectroscopy. The separation and analysis of the selected compounds were satisfactory and fast (duration of the chromatographic run: 40 min). The method was linear for all examined chemicals over the tested range (2 to 50 ng of absolute compound); limits of detection ranged from 0.42 to 1.32 ng of absolute compound. The method was then applied in the determination of the active ingredients of three commercially available insecticide sprays that were separately used in a full-scale environmental chamber (30 m3). After spraying, the fate of the active ingredients [propoxur, piperonyl butoxide (PBO) and pyrethrin insecticides] was monitored over 40 minutes, with and without ventilation. Both adsorbent materials were proven to be efficient and the differences in the concentrations deriving from sampling with both materials were in almost all cases less than 10%. All chemicals were removed in rates that exceeded 80%, after the 40 minutes of monitoring, exhibiting different decay rates. The removal of insecticides was not significantly affected by the ventilation of the chamber. The correlation analysis of propoxur, PBO and pyrethrins with the aerosols of various sizes (15 fractions, from 0.3 to > 20 μ m) showed that propoxur and PBO mainly associated with the medium size aerosols (3–7.5 μm) while pyrethrins seem to link more with heavier particles (> 10 μm).

Chemical emissions from toys – the case of stink blasters

The aim of the present study was to characterise and quantify the emissions of volatile organic compounds that can be released into the air from stink blasters (a toy in human shape that releases malodorous substances after squeezing the head) and to evaluate possible health risks, particularly for children. Although the stink blasters are intended for outdoor use, a hypothetical indoor use (e.g. a childs room) has been considered relevant for exposure assessment studies. The emissions of the items were investigated in environmental chambers and their content was assessed by chemical extraction. In addition to these preliminary experiments and in order to evaluate airborne exposure to cyclohexanone, the stink blasters were placed in the Indoortron facility, a 30 m3 volume walk-in type environmental chamber, and tested for emissions after squeezing several times under ‘real world setting’ conditions (23°C, 50% relative humidity, 0.5 air changes per hour). The amount of chemicals released was determined by applying two different techniques and time series analysis of the air inside the chamber sampled on Tenax TA tubes and DNPH cartridges, followed by thermal desorption gas chromatography mass spectrometry and HPLC–UV, respectively. The main resulting compounds emitted were cyclohexanone and toluene, with concentrations reaching values of 25 and 32 µg m−3, respectively. These levels are much lower than established permissible exposure limits. Measured toluene levels are also below the chronic inhalation reference limit value (300 µg m−3) set for this compound by the California Environmental Protection Agency (Cal EPA). However, such a value is not set for cyclohexanone, so attention should be given to chronic exposures at low concentration levels, in particular for sensitive sub-groups such as children.

Photo-Induced OH reactions of naphthalene and its oxidation products on SiO2

The photo-induced degradation of naphthalene, 1,4-naphthoquinone, 1-naphthol and 1-NO2 naphthalene, adsorbed on silica gel, and with the addition of nitrogenous air pollutants e.g. NO2 (as KNO2) was investigated. Results indicate that compounds adsorbed onto a solid carrier are degraded when irradiated with UV light (λ > 290 nm) in the presence of nitrites. The key species initiating the naphthalene degradation is the OH-radical which is generated through the photolysis of NO2. Reaction products identified were 2-formyl-cinnamaldehyde, 1,4-naphthoquinone, nitronaphthol, o-phthaldialdehyde, phthalide and nitronaphthalene. A mass balance between 40–50% was achieved. Under the same irradiation conditions, 1-NO2 naphthalene is mainly degraded by direct photolysis while degradation of 1-naphthol and 1,4-naphthoquinone proceeds via the reaction with OH-radicals. Identified products were hydroxy-nitro-nitroso- and quinones compounds.