<p><strong>Abstract.</strong> In this study, the NO<sub><i>x</i></sub> dependence of secondary organic aerosol (SOA) formation from β-pinene photooxidation was comprehensively investigated in the Jülich Plant Atmosphere Chamber. Consistent with the results of previous NO<sub><i>x</i></sub> studies we found increases of SOA yields at low NO<sub><i>x</i></sub> conditions ([NO<sub><i>x</i></sub>]<sub>0</sub> < 30 ppb, [BVOC]<sub>0</sub>/[NO<sub><i>x</i></sub>]<sub>0</sub> > 10 ppbC ppb<sup>−1</sup>). Furthermore, increasing [NO<sub><i>x</i></sub>] at high NO<sub><i>x</i></sub> conditions ([NO<sub><i>x</i></sub>]<sub>0</sub> > 30 ppb, [BVOC]<sub>0</sub>/[NO<sub><i>x</i></sub>]<sub>0</sub> ~ 10 to ~ 2.6 ppbC ppb<sup>−1</sup>) suppressed the SOA yield. The increase of SOA yield at low NO<sub><i>x</i></sub> conditions was attributed to increase of OH concentration, most probably by OH recycling in NO + HO<sub>2</sub> → NO<sub>2</sub> + OH reaction. Separate measurements without NO<sub><i>x</i></sub> addition but with different OH primary production rates confirmed the OH dependence of SOA yields. After removing the effect of OH concentration on SOA mass growth by keeping the OH concentration constant, SOA yields only decreased with increasing [NO<sub><i>x</i></sub>]. Measuring the NO<sub><i>x</i></sub> dependence of SOA yields at lower [NO]/[NO<sub>2</sub>] ratio showed less pronounced increase in both; OH concentration and SOA yield. This result was consistent to our assumption of OH recycling by NO and to SOA yields being dependent on OH concentrations. It furthermore indicated that NO<sub><i>x</i></sub> dependencies vary for different NO<sub><i>x</i></sub> compositions. A substantial fraction of the NO<sub><i>x</i></sub>-induced decrease of SOA yields at high NO<sub><i>x</i></sub> conditions was caused by NO<sub><i>x</i></sub>-induced suppression of new particle formation (NPF). This was shown by probing the NO<sub><i>x</i></sub> dependence of SOA formation in the presence of seed particles. After eliminating the effect of NO<sub><i>x</i></sub>-induced suppression of NPF and NO<sub><i>x</i></sub> induced changes of OH concentrations, the overall effect of NO<sub><i>x</i></sub> on the SOA yield from β-pinene photooxidation was moderate. Comparing with β-pinene experiments, the SOA formation from α-pinene photooxidation was only suppressed by increasing NO<sub><i>x</i></sub>. However, basic mechanisms of the NO<sub><i>x</i></sub> impacts were the same as that of β-pinene.</p>

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<p><strong>Abstract.</strong> The formation of organic nitrates (ON) in the gas phase and their impact on mass formation of Secondary Organic Aerosol (SOA) was investigated in a laboratory study for <i>α</i>-pinene and <i>β</i>-pinene photo-oxidation. Focus was the elucidation of those mechanisms that cause the often observed suppression of SOA mass formation by NO<sub>x</sub>, and therein the role of highly oxygenated multifunctional molecules (HOM). We observed that with increasing NO<sub>x</sub> (a) the portion of HOM organic nitrates (HOM-ON) increased, (b) the fraction of accretion products (HOM-ACC) decreased and (c) HOM-ACC contained on average smaller carbon numbers.</p> <p>Specifically, we investigated HOM organic nitrates (HOM-ON), arising from the termination reactions of HOM peroxy radicals with NO<sub>x</sub>, and HOM permutation products (HOM-PP), such as ketones, alcohols or hydroperoxides, formed by other termination reactions. Effective uptake coefficients γeff of HOM on particles were determined. HOM with more than 6 O-atoms efficiently condensed on particles (<i>γ</i></sub><sub>eff</sub> > 0.5 in average) and for HOM containing more than 8 O-atoms, every collision led to loss. There was no systematic difference in <i>γ</i></sub><sub>eff</sub> for HOM-ON and HOM-PP arising from the same HOM peroxy radicals. This similarity is attributed to the multifunctional character of the HOM: as functional groups in HOM arising from the same precursor HOM peroxy radical are identical, vapor pressures should not strongly depend on the character the final termination group. As a consequence, the suppressing effect of NO<sub>x</sub> on SOA formation cannot be simply explained by replacement of terminal functional groups by organic nitrate groups.</p> <p>The fraction of organic bound nitrate (OrgNO<sub>3</sub>) stored in gas-phase HOM-ON appeared to be substantially higher than the fraction of particulate OrgNO<sub>3</sub> observed by aerosol mass spectrometry. This result suggests losses of OrgNO<sub>3</sub> for organic nitrates in particles, probably due to hydrolysis of OrgNO<sub>3</sub> that releases HNO<sub>3</sub> into the gas phase but leaves behind the organic rest in the particulate phase. However, the loss of HNO<sub>3</sub> alone, could not explain the observed suppressing effect of NO<sub>x</sub> on particle mass formation from <i>α</i>-pinene and <i>β</i>-pinene.</p> <p>We therefore attributed most of the reduction in SOA mass yields with increasing NO<sub>x</sub> to the significant suppression of gas-phase HOM-ACC which have high molecular mass and are potentially important for SOA mass formation at low NO<sub>x</sub> conditions.</p>

Background and aimMarine n-3 fatty acids and γ-linolenic acid both have anti-inflammatory effects and may be useful to help treat inflammatory diseases. The effects of these alone or combined were examined in patients with arthritis in a randomized controlled trial.DesignPatients with rheumatoid arthritis or psoriatic arthritis were randomized into four groups in a double-blind, placebo-controlled parallel designed study. Patients received the respective capsules (1: 3.0 g n-3 LC-PUFA/d; 2: 3.2 g γ-linolenic acid/d; 3: 1.6 g n-3 LC-PUFA + 1.8 g γ-linolenic acid/d; 4: 3.0 g olive oil) for a twelve week period. Clinical status was evaluated and blood samples were taken at the beginning and at the end of the period. Differences before and after intervention were tested with paired t-test or with Wilcoxon test for non-normal data distribution.Results60 patients (54 rheumatoid arthritis, 6 psoriatic arthritis) were randomised, 47 finished per protocol. In group 1, the ratio of arachidonic acid (AA)/eicosapentaenoic acid (EPA) decreased from 6.5 ± 3.7 to 2.7 ± 2.1 in plasma lipids and from 25.1 ± 10.1 to 7.2 ± 4.7 in erythrocyte membranes (p ≤ 0.001). There was no significant influence on AA/EPA ratio due to interventions in group 2-4. In group 2, the intake of γ-linolenic acid resulted in a strong rise of γ-linolenic acid and dihomo-γ-linolenic acid concentrations in plasma lipids, cholesteryl esters, and erythrocyte membranes. The combination of n-3 LC-PUFA and γ-linolenic acid (group 3) led to an increase of γ-linolenic acid and dihomo-γ-linolenic acid concentrations in plasma lipids, cholesteryl esters, and erythrocyte mem-branes. This increase was only half of that in group 2.ConclusionsIncorporation of eicosanoid precursor FAs was influenced by an intake of n-3 LC-PUFA and γ-linolenic acid suggesting a possible benefit for therapy of chronic inflammatory diseases.Trial RegistrationClinicalTrials NCT01179971

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