Organic Nitrate Formation Research Articles

Organic nitrate formation in the radical-initiated oxidation of model aerosol particles in the presence of NOx

Using a flow tube reactor coupled to a chemical ionization mass spectrometer, the Cl-initiated oxidation of solid and supercooled liquid brassidic acid (BA, trans-13-docosenoic acid) particles was investigated in the presence of NO and NO2. For the first time, organic nitrate formation from the heterogeneous oxidation of model organic aerosols in the presence of NO was observed, but none was formed by the addition of up to 600 ppb of NO2. Also, no nitrate formation was observed in liquid particles, but the nitrate yields in the solid particles were measured to be as large as 6% with a negative temperature dependence over the range 259-293 K. The corresponding effective activation energy of -7.5 (+/-4.4) kJ mol(-1) suggests that the mechanism of particulate organic nitrate formation is analogous to the termolecular gas-phase reaction of . The yields are smaller than those from analogous gas-phase reactions, but this may result from photodissociation of the nitrate by the UV (355 nm) laser for which there is indirect evidence. Additionally, enhanced rates of the RO2+RO2 reactions in the condensed phase could lead to smaller nitrate yields. The results suggest that slower diffusion of the RO2 radicals in the solid particles compared to the liquid particles makes the RO2+NO reaction competitive with the RO2+RO2 reactions and results in nitrate formation near the surface of the particle. The organic nitrates formed in these experiments are observed intact after the reacted particles have been vaporized at temperatures up to 380 degrees C suggesting that they are thermally stable in the troposphere and may enable long-range transport of NOx if they photodissociate on the timescale of days. The findings from these experiments are not specific to unsaturated carboxylic acids but should apply to nearly all particulate hydrocarbons, and they indicate that the particle phase could be important in determining how organic aerosols evolve chemically through radical-initiated oxidation in polluted atmospheres.

Interactions of NO 2 with activated carbons modified with cerium, lanthanum and sodium chlorides

Highly porous wood-based activated carbon was impregnated with cerium, lanthanum and sodium chlorides using incipient impregnation method. On the samples prepared adsorption of NO 2 was carried out from moist (70% humidity) air either with or without the prehumidification. The materials were characterized using adsorption of nitrogen, thermal analysis, FTIR, and potentiometric titration. The results indicated that for all materials a significant amount of NO 2 was reduced to NO and released from the system. In the case of virgin carbons, the NO 2 interacting with the surface along with nitric and nitrous acids formed there in the presence of water significantly increased the acidity of the carbons by the formation of oxygen-containing groups and organic nitrates. On the other hand, when chlorides were present the capacity to interact with nitrogen dioxide increased since the inorganic phase, depending on the nature of metal, bound NO 2 in the forms of nitrates (Ce, La, Na), got oxidized/oxidized carbon surface (for Ce) or contributed to the formation of nitrosyl chloride (for Na).

Activated carbons modified with sewage sludge derived phase and their application in the process of NO 2 removal

Highly porous wood-based activated carbon was treated with species extracted from the surface of pyrolyzed sewage sludge. Their deposition on the external surface was visible by a change of the color of the carbon and on internal surfaces, by a decrease in porosity. The as-received carbon and its impregnated counterpart were heat treated at 950 °C at an inert atmosphere. Data for the adsorption on NO 2 was carried out from dry and moist (70% humidity) air. The results indicated that for all materials a significant amount of NO 2 was reduced to NO and released from the system. Heat treatment increases the capacity possibly as a result of an increase in basicity. The addition of the inorganic phase has a positive effect only when adsorption is run in moist conditions and inorganic nitrates and nitrites were formed. Otherwise, the NO 2 adsorbed and nitric and nitrous acids formed on the surface significantly increase the acidity of the carbons by the formation of oxygen-containing groups and organic nitrates.

Observational constraints on the chemistry of isoprene nitrates over the eastern United States

The formation of organic nitrates during the oxidation of the biogenic hydrocarbon isoprene can strongly affect boundary layer concentrations of ozone and nitrogen oxides (NOx = NO + NO2). We constrain uncertainties in the chemistry of these isoprene nitrates using chemical transport model simulations in conjunction with observations over the eastern United States from the International Consortium for Atmospheric Research on Transport and Transformation (ICARTT) field campaign during summer 2004. The model best captures the observed boundary layer concentrations of organic nitrates and their correlation with ozone using a 4% yield of isoprene nitrate production from the reaction of isoprene hydroxyperoxy radicals with NO, a recycling of 40% NOx when isoprene nitrates react with OH and ozone, and a fast dry deposition rate of isoprene nitrates. Simulated boundary layer concentrations are only weakly sensitive to the rate of photochemical loss of the isoprene nitrates. An 8% yield of isoprene nitrates degrades agreement with the observations somewhat, but concentrations are still within 50% of observations and thus cannot be ruled out by this study. Our results indicate that complete recycling of NOx from the reactions of isoprene nitrates and slow rates of isoprene nitrate deposition are incompatible with the observations. We find that ∼50% of the isoprene nitrate production in the model occurs via reactions of isoprene (or its oxidation products) with the NO3 radical, but note that the isoprene nitrate yield from this pathway is highly uncertain. Using recent estimates of rapid reaction rates with ozone, 20–24% of isoprene nitrates are lost via this pathway, implying that ozonolysis is an important loss process for isoprene nitrates. Isoprene nitrates are shown to have a major impact on the nitrogen oxide (NOx = NO + NO2) budget in the summertime U.S. continental boundary layer, consuming 15–19% of the emitted NOx, of which 4–6% is recycled back to NOx and the remainder is exported as isoprene nitrates (2–3%) or deposited (8–10%). Our constraints on reaction rates, branching ratios, and deposition rates need to be confirmed through further laboratory and field measurements. The model systematically underestimates free tropospheric concentrations of organic nitrates, indicating a need for future investigation of the processes controlling the observed distribution.

Why are there large differences between models in global budgets of tropospheric ozone?

Global 3‐D tropospheric chemistry models in the literature show large differences in global budget terms for tropospheric ozone. The ozone production rate in the troposphere, P(Ox), varies from 2300 to 5300 Tg yr−1 across models describing the present‐day atmosphere. The ensemble mean of P(Ox) in models from the post‐2000 literature is 35% higher than that compiled in the Intergovernmental Panel on Climate Change (IPCC) Third Assessment Report (TAR). Simulations conducted with the GEOS‐Chem model using two different assimilated meteorological data sets for 2001 (GEOS‐3 and GEOS‐4), as well as 3 years of GISS GCM meteorology, show P(Ox) values in the range 4250–4700 Tg yr−1; the differences appear mostly because of clouds. Examination of the evolution of P(Ox) over the GEOS‐Chem model history shows major effects from changes in heterogeneous chemistry, the lightning NOx source, and the yield of organic nitrates from isoprene oxidation. Multivariate statistical analysis of model budgets in the literature indicates that 74% of the variance in P(Ox) across models can be explained by differences in NOx emissions, inclusion of nonmethane volatile organic compounds (NMVOCs, mostly biogenic isoprene), and ozone influx from stratosphere‐troposphere exchange (STE). Higher NOx emissions, more widespread inclusion of NMVOC chemistry, and weaker STE in the more recent models increase ozone production; however, the effect of NMVOCs does not appear generally sensitive to the magnitude of emissions within the range typically used in models (500–900 Tg C yr−1). We find in GEOS‐Chem that P(Ox) saturates when NMVOC emissions exceed 200 Tg C yr−1 because of formation of organic nitrates from isoprene oxidation, providing an important sink for NOx.

The production of organic nitrates from atmospheric oxidation of ethers and glycol ethers

AbstractThe production of organic nitrates from OH reaction (in the presence of NO) with methoxy propane, 1‐methoxy‐2‐propanol, ethoxy butane, and 2‐butoxyethanol was studied. The measured total organic nitrate yields were 1.8 (±0.4)%, 0.98 (±0.2)%, 7.7 (±2)%, and 9.6 (±1)%, respectively. The total organic nitrate yield for methoxypropane is 26% of that (7.0%) for n‐butane. The organic nitrate yield for ethoxy butane is 55% of that (14%) for n‐hexane. The peroxy radicals produced from OH reaction with the methylene groups α to the ether linkage have an organic nitrate branching ratio (k3b/k3) value ∼50% of those in analogous n‐alkanes. On the other hand, k3b/k3 values for peroxy radical functional groups not adjacent to the ether linkage (in γ and δ positions) are on average 1.7 times greater than for the analogous n‐alkyl peroxy radicals. The organic nitrate formation yield for 1‐methoxy‐2‐propanol is almost half that of methoxy propane, while for 2‐butoxyethanol it is 21% greater than that of butoxyethane. Our data lead us to the conclusion that the ether linkage imparts an inductive effect that decreases the value of k3b/k3 for peroxy radicals adjacent to it, yet has a stabilizing effect, from the additional vibrational modes for those peroxy radicals not adjacent to it, increasing their k3b/k3 values. The effect of both the O and OH groups in these molecules and the importance of their position relative to the peroxy group are discussed in this paper. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 686–699, 2005

On the Mechanism for Nitrate Formation via the Peroxy Radical + NO Reaction

We present a master equation study of organic nitrate formation from the peroxy radical (RO2) + NO reaction. The mechanism is constrained by both quantum chemical calculations of the potential energy surface and existing yield data. This mechanism displays heretofore unrecognized features of the system, including distinct conformers of a critical peroxynitrite (ROONO) intermediate that do not interconvert and a dual falloff behavior driven by collisional stabilization in multiple wells. These features have significant implications for atmospheric chemistry; in particular, only a fraction of the ROONO intermediates may easily isomerize to nitrates, resulting in a limit to total nitrate production. Existing mechanisms, extrapolated to low temperature and high pressure, produce nitrate almost exclusively. As a consequence, hydrocarbon oxidation sequences based on these mechanisms do not propagate radical chemistry, which is inconsistent with available experimental data. To reproduce observed nitrate yields, we model a transition state from the ROONO intermediate to RONO2 that differs considerably from the few found in computational studies. Specifically, the data require that this transition state energy lie well below the energy of separated radical products (RO + NO2), while computational studies find the transition state at higher energies. A second feature of yield data is difficult to model; to enable collisional stabilization of C5 systems, as observed, we reduce the unimolecular decomposition rate constants from the ROONO intermediate by a factor that is at the far end of the plausible range. However, with these experimental constraints in place, the model successfully reproduces multiple features of existing data quantitatively, including both high- and low-pressure asymptotes to nitrate production as well as the observed shifting of pressure falloff curves with carbon number. Consequently, we present a new parametrization of nitrate yields, providing interpolation equivalent to existing parametrizations but dramatically improved extrapolation behavior.

Observed and modeled VOC chemistry under high VOC/NO conditions in the Southeast United States national parks

In airsheds that contain high volatile organic compounds (VOCs) and low NO x (=NO+NO 2 ) concentrations, ozone (O 3 ) production may be significantly suppressed by NO x reactions that lead to the formation of organic nitrates. O 3 and its precursors (VOCs and NO x ) ambient levels simulated using a regional-scale photochemical model, called Multiscale Air Quality Simulation Platform, are analyzed and compared to observed data from three southeast United States national parks.

Products of reaction of OH radicals with α‐pinene

Products of the gas‐phase reaction of α‐pinene with OH radicals in the presence of NO have been investigated using gas chromatography with flame ionization detection to quantify pinonaldehyde and in situ atmospheric pressure ionization mass spectrometry in the negative ion mode to quantify selected other products as their NO2− adducts by utilizing C6‐dihydroxycarbonyls and C6‐hydroxynitrates formed in situ from the reaction of OH radicals with 1‐hexene as an internal standard. The products quantified, and their molar formation yields, were: pinonaldehyde, 28 ± 5%; molecular weight 184 product (dihydroxycarbonyl), 19% (with an estimated uncertainty of a factor of ∼2); molecular weight 200 product, 11% (with an estimated uncertainty of a factor of ∼2). Together with a very approximate yield from our API‐MS analyses for the formation of organic nitrates (∼1%) and literature data for acetone (plus coproducts), ∼65–70% of the reaction products and pathways are accounted for.

Measurements of the kinetics of the OH‐initiated oxidation of isoprene

The mechanism of the OH‐initiated oxidation of isoprene has been studied at 300 K and 100 and 150 Torr total pressure using a turbulent flow technique coupled with laser‐induced fluorescence detection of the OH radical. The rate constant for the reaction of OH with isoprene was measured to be (10.8 ± 0.5) × 10−11 cm3 molecule−1 s−1 at 150 Torr total pressure and independent of pressure between 100 and 150 Torr, in excellent agreement with most previous absolute measurements. In the presence of O2 and NO, propagation of OH radicals and loss of OH through radical termination resulting from the formation of organic nitrates were measured at 150 Torr total pressure and compared to simulations of the kinetics of this reaction system. The results of these experiments are consistent with an overall rate constant of (1.1 ± 0.8) × 10−11 cm3 molecule−1 s−1 for the reaction of NO with isoprene‐based hydroxyalkyl peroxy radicals, with branching ratios of 0.85 ± 0.10 for the bimolecular channel (oxidation of NO to NO2) and 0.15 ± 0.10 for the termolecular channel (formation of organic nitrates). Although the organic nitrate yield reported here is the result of indirect measurements, it suggests that isoprene may be a more significant sink of NOx than previously estimated.

Measurement of the organic nitrate yield from OH reaction with isoprene

This paper describes the results of measurements of the branching ratio (k2b/(k2a + k2b)) for formation of organic nitrates via peroxy radical reaction with NO, following the reaction of the OH radical with isoprene (2‐methyl‐l,3‐butadiene). The experiments were conducted in a 5 m3 all‐Teflon photochemical reaction chamber, via the photolysis of isopropyl nitrite in the presence of isoprene and NO. The organic nitrate yield was determined from the measurement of the sum of all organic nitrate isomers, using an organic nitrate selective detector, as a function of isoprene consumed. Organic nitrates were sampled directly from the reaction chamber into a capillary Chromatographic column, followed by separation and quantitative pyrolytic conversion to NO2, which was detected through luminol chemiluminescence. In this manner, seven isomeric organic nitrates were observed, with a total yield of 4.4%. The structural features of the precursor peroxy radicals that influence the magnitude of the yield is discussed. Emission inventories for isoprene and NO lead to the conclusion that as much as 7% of NO emitted in the eastern United States in the summer months is lost from the atmosphere through the isoprene nitrate channel.

Seasonal budgets of reactive nitrogen species and ozone over the United States, and export fluxes to the global atmosphere

A three‐dimensional, continental‐scale photochemical model is used to investigate seasonal budgets of O3 and NOy species (including NOx and its oxidation products) in the boundary layer over the United States and to estimate the export of these species from the U.S. boundary layer to the global atmosphere. Model results are evaluated with year‐round observations for O3, CO, and NOy species at nonurban sites. A seasonal transition from NOx to hydrocarbon‐limited conditions for O3 production over the eastern United States is found to take place in the fall, with the reverse transition taking place in the spring. The mean NOx/NOy molar ratio in the U.S. boundary layer in the model ranges from 0.2 in summer to 0.6 in winter, in accord with observations, and reflecting largely the seasonal variation in the chemical lifetime of NOx. Formation of hydroxy organic nitrates during oxidation of isoprene, followed by decomposition of these nitrates to HNO3, is estimated to account for 30% of the chemical sink of NOx in the U.S. boundary layer in summer. Model results indicate that peroxyacylnitrates (PANs) are most abundant in the U.S. boundary layer in spring (25% of total NOy.), reflecting a combination of active photochemistry and low temperatures. About 20% of the NOx emitted from fossil fuel combustion in the United States in the model is exported out of the U.S. boundary layer as NOx or PANs (15% in summer, 25% in winter). This export responds less than proportionally to changes in NOx emissions in summer, but more than proportionally in winter. The annual mean export of NOx and PANs from the U.S. boundary layer is estimated to be 1.4 Tg N yr−1, representing an important source of NOx on the scale of the northern hemisphere troposphere. The eventual O3 production in the global troposphere due to the exported NOx and PANs is estimated to be twice as large, on an annual basis, as the direct export of O3 pollution from the U.S. boundary layer. Fossil fuel combustion in the United States is estimated to account for about 10% of the total source of O3 in the northern hemisphere troposphere on an annual basis.

Export of reactive nitrogen from North America during summertime: Sensitivity to hydrocarbon chemistry

The global influence on tropospheric chemistry of nitrogen oxides (NOx = NO + NO2) emitted by fossil fuel combustion may be strongly modulated by nonmethane hydrocarbon (NMHC) chemistry taking place in the continental boundary layer. This effect is investigated using a three‐dimensional, continental‐scale model of tropospheric O3‐NOx‐NMHC chemistry over North America in summer. The model includes detailed representation of NMHC chemistry including in particular isoprene. Model results are evaluated with observations for ozone, reactive nitrogen species, and photochemical tracers at a number of sites in North America. Sensitivity analyses are conducted to explore the effects of assumptions regarding the aerosol chemistry of peroxy radicals and the fate of hydroxy organic nitrates produced from the oxidation of isoprene. A budget analysis for the United States in the model indicates that 9% Of NOx. emitted from fossil fuel combustion is exported out of the continental boundary layer as NOx, 3.5% is exported as peroxyacetyl nitrate (PAN), and 3.7% is exported as other organic nitrates. Isoprene is the principal NMHC responsible for the formation and export of organic nitrates, which eventually decompose to provide a source of NOx in the remote troposphere. Export of NOx. and organic nitrates from the U.S. boundary layer is found to be a major source of NOx. on the scale of the northern hemisphere troposphere and on the scale of the upper troposphere at northern midlatitudes. Proper representation of isoprene chemistry in the continental boundary layer is important for simulation Of NOx in global tropospheric chemistry models.

Regional budgets for nitrogen oxides from continental sources: Variations of rates for oxidation and deposition with season and distance from source regions

Measurements of nitrogen deposition and concentrations of NO, NO2, NOy (total oxidized N), and O3 have been made at Harvard Forest in central Massachusetts since 1990 to define the atmospheric budget for reactive N near a major source region. Total (wet plus dry) reactive N deposition for the period 1990–1996 averaged 47 mmol m−2 yr−1 (126 μmol m−2 d−1, 6.4 kg N ha−1 yr−1), with 34% contributed by dry deposition. Atmospheric input adds about 12% to the N made available annually by mineralization in the forest soil. The corresponding deposition rate at a distant site, Schefferville, Quebec, was 20 mmol m−2 d−1 during summer 1990. Both heterogeneous and homogeneous reactions efficiently convert NOx to HNO3 in the boundary layer. HNO3 is subsequently removed rapidly by either dry deposition or precipitation. The characteristic (e‐folding) time for NOx oxidation ranges from 0.30 days in summer, when OH radical is abundant, to ∼1.5 days in the winter, when heterogeneous reactions are dominant and O3 concentrations are lowest. The characteristic time for removal of NOx oxidation products (defined as NOy minus NOx) from the boundary layer by wet and dry deposition is ∼1 day, except in winter when it decreases to 0.6 day. Biogenic hydrocarbons contribute to N deposition through formation of organic nitrates but are also precursors of reservoir species, such as peroxyacetylnitrate, that may be exported from the region. A simple model assuming pseudo first‐order rates for oxidation of NOx, followed by deposition, predicts that 45% of NOx in the northeastern U.S. boundary layer is removed in 1 day during summer and 27% is removed in winter. It takes 3.5 and 5 days for 95% removal in summer and winter, respectively.

Impact of inert organic nitrate formation on ground‐level ozone in a regional air quality model using the Carbon Bond Mechanism 4

A regional air quality model is used to assess the impact of inert organic nitrate formation on ground‐level ozone in the eastern United States during summer. The chemical mechanism used is the Carbon Bond Mechanism 4 (CBM4), which is widely used by regulatory agencies in the United States in air quality modeling applications. Recently, modifications were made to the reaction mechanism involving the organic peroxy radicals which form inert organic nitrates without a critical scientific review of the effects of these changes. In this study, we demonstrate for the first time that the simulated large‐scale distribution of ground‐level ozone is extremely sensitive to these mechanism changes. Inclusion of radical‐radical reactions involving the organic peroxy radicals suppresses inert organic nitrate formation, and leads to significant increases in nitrogen oxide levels over large parts of the model domain. As a consequence of increased rates of ozone photochemical production, ozone mixing ratios are enhanced by as much 10–25 ppbv when these additional radical termination pathways are considered in the model.

Gas-phase reaction of NO3 radicals with isoprene: a kinetic and mechanistic study

The gas-phase reaction of NO3 radicals with isoprene was investigated under flow conditions at 298 K in the pressure range 6.8<P(mbar)<100 using GC-MS/FID, direct MS, and long-path FT–IR spectroscopy as detection techniques. By means of a relative rate method, the rate constant for the primary attack of NO3 radicals toward isoprene was determined to be (6.86±2.60)×10−13 cm3 molecule−1 s−1. The formation of the possible oxiranes, 2-methyl-2-vinyl-oxirane and 2-(1-methyl-vinyl)-oxirane, was observed in dependence on total pressure. In the presence of O2 in the carrier gas, the product distribution was found to be strongly dependent on the reaction pathways of formed peroxy radicals. If the peroxy radicals mainly reacted in a self-reaction, the formation of organic nitrates was detected and 4-nitroxy-3-methyl-but-2-enal was identified as a main product. On the other hand, when NO was added to the gas mixture and the peroxy radicals were converted via RO2+NO→RO+NO2, the formation of methyl vinyl ketone as the main product as well as 3-methylfuran and meth-acrolein was observed. From the ratio of the product yields if NO was added to the gas mixture it was concluded that the attack of NO3 radicals predominantly takes place in the 1-position. A reaction mechanism is proposed and the application of these results to the troposphere are discussed. © 1997 John Wiley & Sons, Inc.

Products of the gas‐phase reaction of methyl tert‐butyl ether with the OH radical in the presence of NOx

AbstractThe products of the reaction of the hydroxyl (OH) radical with methyl tert‐butyl ether (MTBE) in NOx‐air systems were identified and measured by Fourier transform infrared absorption spectroscopy and gas chromatography. The products observed, and their yields, were as follows: t‐butyl formate, 76 ± 7%; formaldehyde, 37%; methyl acetate, 17 ± 2%, and acetone, 2.1 ± 0.9%, where the stated error limits represent both random (two standard deviations) and estimated systematic uncertainties. These products account for ca. 95% of the MTBE carbon reacted. Infrared absorption bands which may be due to small amounts of organic nitrate formation were observed, but organic nitrate yields could not be quantified. These data allow a chemical mechanism for the reaction of MTBE with the OH radical in the presence of NOx to be formulated.

Smog chamber study of H2O2 formation in etheneNOx and propeneNOx mixtures

AbstractHydrogen peroxide formation in the photooxidation of CONOx, etheneNOx, and propeneNOx mixtures has been determined in the TVA 31 cubic meter smog chamber under the following conditions: [NOx] ca. 22–46 ppb; ethene = 0.22–1.1 ppm, [propene] = 0.12–0.97 ppm; [H2O] ca. 8 × 10−3 ppm. Ethene, propene, NO, NOx, PAN, HCHO, and CH3CHO were also monitored. Computer modeling was performed using the gas phase ethene and propene mechanism of the Regional Acid Deposition Model. There is good agreement between the model predicted and observed H2O2 concentrations. However, to successfully model all the propeneNOx experimental results, organic nitrate formation from the reaction of peroxy radicals with NO must be included in the mechanism.

Reaction of monoterpenes with ozone, sulphur dioxide and nitrogen dioxide—gas-phase oxidation of SO 2 and formation of sulphuric acid

Teflon bag experiments were carried out in the dark in order to study the gas-phase reactions of selected monoterpenes with O 3 in the presence of SO 2 (β-pinene) as well as in the presence of SO 2/NO 2 (α-pinene, β-pinene, limonene). Emphasis was given in identifying the main reaction products and in quantifying the H 2SO 4 aerosol formed. Apart from the H 2SO 4 aerosol no other S containing compounds could be detected. It was found that the reaction of β-pinene with O 3, SO 2 and NO 2 leads mainly to 6,6-dimethyl-bicyclo [3.1.1] heptan-2-one (nopinone), the α-pinene-O 3-SO 2-NO 2-reaction produced 2′,2′-dimethyl-3-acetyl cyclobutyl ethanal (pinonaldehyde). The reaction of limonene with O 3-SO 2-NO 2 leads mainly to an unidentified product with a molecular weight M + 134. In addition to the above-mentioned volatile products, the formation of organic nitrates could be established by means of gas chromatography-mass spectrometry. The yield of H 2SO 4 in the system β-pinene/O 3/SO 2 varies between 0.13 and 0.44 depending on the initial conditions, e.g. humidity. In the system terpene/O 3/SO 2/NO 2 the yield of H 2SO 4 for α-pinene (after 1 h reaction time) was 0.01–0.03, for β-pinene (2 or 4 h reaction time) 0.07–0.13 and for limonene (1 h reaction time) 0.02–0.09.

A chemical mechanism for dry deposition—the role of biogenic hydrocarbon (Terpene) emissions in the dry deposition of O3, SO2and NOxin forest areas

Abstract Terpenes react quite rapidly with ambient ozone and lead via ozonides to highly oxidizing radicals and consecutive products forming aerosols. In the presence of SO2 sulphur containing compounds, mainly as sulphate, are formed. By means of gas chromatography/mass spectrometry and by comparison with known spectra the main products of the reaction of ß‐pinene (as a model compound) with ozone and sulphur dioxide could be identified. Reaction of terpenes with NO3‐radicals, which build up in the atmosphere at night‐time, leads to the formation of organic nitrates that form aerosols. The kinetics as well as the products of the reaction between NO3‐radicals and ß‐pinene have been studied by FTIR and MS.