Limonene Emissions: Do Different Types Have Different Biological Effects?

Limonene is one of the most abundant pollutants indoors, and it contributes to the formation of additional pollutants, such as formaldehyde and photochemical smog. Limonene is commonly used in fragranced consumer products, such as cleaning supplies and air fresheners, which have also been associated with health problems. Limonene can exist in different enantiomeric forms (R-limonene and S-limonene) and be derived from different sources. However, little is known about whether different forms and sources of limonene may have different effects. This research explored whether different types of limonene, at the same concentrations, could elicit different biological effects. To investigate this question, the study employed Aedes aegypti mosquitoes, which have sophisticated olfactory abilities, in olfactometer tests of repellency/attraction. The results indicate that a synthetic source of R-limonene is more repellent than a natural source of R-limonene. In addition, synthetic sources of both R-limonene and S-limonene are not significantly different in repellency. These findings can contribute to our understanding and further exploration of the effects of a common fragrance compound on air quality and health.

Deriving Nitrogen Oxide emissions from inland waterway vessels using MAX-DOAS measurements

<p>Inland waterway shipping is an important mode of freight transport in Europe with an extended network especially in Germany, e.g. the Rhine and Danube Rivers, and a variety of artificial channels. Nitrogen oxides (NO<sub>x </sub>= NO + NO<sub>2</sub>), which are also emitted by ships, play an important role in tropospheric chemistry. NO<sub>x</sub> contributes to the formation of tropospheric ozone and thus photochemical smog. Moreover, NO<sub>x</sub> affects human health and increases the acidification of ecosystems.  Monitoring of NO<sub>x</sub> emissions from inland waterway vessels could provide cities that are located along the rivers with valuable information about ship contribution to the pollution.</p><p>In this study, ground-based MAX-DOAS (Multi AXis-Differential Optical Absorption Spectroscopy) measurements were performed along the Rhine River. The aim is to derive NO<sub>2</sub> emissions from individual ships. First sensitivity measurements showed that our Tube MAX-DOAS instrument is sensitive enough to detect a NO<sub>2</sub> signal that can be attributed to passing ships. However, finding the optimal measurement mode to determine the emissions proves to be a challenging endeavour.</p>

Ambient nitro-aromatic compounds – biomass burning versus secondary formation in rural China

Nitro-aromatic compounds (NACs) were measured hourly at a rural site in China during wintertime to monitor the changes due to local and regional impacts of biomass burning (BB). Concurrent and continuous measurements of the concentrations of 16 NACs in the gas and particle phases were performed with a time-of-flight chemical ionization mass spectrometer (CIMS) equipped with a Filter Inlet for Gases and AEROsols (FIGAERO) unit using iodide as the reagent ion. NACs accounted for <2 % of the mass concentration of organic matter (OM) and total particulate matter (PM), but the total particle mass concentrations of these compounds can reach as high as 1000 ng m−3 (299 ng m−3 avg), suggesting that they may contribute significantly to the radiative forcing effects of atmospheric particles. Levels of gas-phase NACs were highest during the daytime (15:00–16:00 local time, LT), with a smaller night-time peak around 20:00 LT. Box-model simulations showed that this occurred because the rate of NAC production from gas-phase sources exceeded the rate of loss, which occurred mainly via the OH reaction and to a lesser degree via photolysis. Data gathered during extended periods with high contributions from primary BB sources (resulting in 40 %–60 % increases in NAC concentrations) were used to characterize individual NACs with respect to gas–particle partitioning and the contributions of regional secondary processes (i.e. photochemical smog). On days without extensive BB, secondary formation was the dominant source of NACs, and NAC levels correlated strongly with the ambient ozone concentration. Analyses of individual NACs in the regionally aged plumes sampled on these days allowed precursors such as phenol and catechol to be linked to their NAC derivatives (i.e. nitrophenol and nitrocatechol). Correlation analysis using the high time resolution data and box-model simulation results constrained the relationships between these compounds and demonstrated the contribution of secondary formation processes. Furthermore, 13 of 16 NACS were classified according to primary or secondary formation process. Primary emission was the dominant source (accounting for 60 %–70 % of the measured concentrations) of 5 of the 16 studied NACs, but secondary formation was also a significant source. Photochemical smog thus has important effects on brown carbon levels even during wintertime periods dominated by primary air pollution in rural China.

Kondisi Gradien Temperatur terhadap Proses Pengenceran Smog Fotokimia di Cekungan Bandung

ABSTRACTBig cities with valley or basin topography such as Bandung, generally have problems with air pollution due to the inversion layer and photochemical smog formations. The inversion conditions cause photochemical smog settling so that the air looks dark on the surface. This study was conducted to analyze the character of inversion events in Bandung due to vertical temperature changes. The inversion layer is obtained from the TAPM (The Air Pollution Model) model and in situ measurement of vertical temperatures by flying a temperature sensor to get the temperature profile. The TAPM running model is carried out in July and December following the dry and rainy seasons. In situ temperature observations are carried out in September 2018 using a drone according to the dry season and data corresponding to the rainy season using data from previous research with a radiosonde balloon. The running model results show that the inversion layer in the rainy season is stronger and more persistent than in the dry season. The inversion layer at night until morning occurs at the surface level, then the inversion layer rises, and finally, the inversion layer breaks up around 10:00 in July and around 12:00 in December. Validation with in situ measurements shows similarity in the pattern. The inversion event correlates with the subsidence and dilution of smog and photochemical smog pollutants from the edge of the Bandung Basin area.Keywords: basin, urban, photochemical smog, inversionABSTRAKKota besar dengan topografi berbentuk lembah atau cekungan seperti Bandung, umumnya memiliki masalah dengan polusi udara karena adanya pembentukkan lapisan inversi dan smog fotokimia. Kondisi inversi menyebabkan terjadinya pengendapan smog fotokimia, sehingga udara terlihat gelap pada permukaan. Penelitian ini dilakukan untuk menganalisis karakter kejadian inversi di Cekungan Bandung akibat dari perubahan temperatur vertikal. Lapisan inversi diperoleh dari model TAPM (Model Polusi Udara) dan pengukuran in situ temperatur vertikal dengan menerbangkan sensor suhu untuk mendapatkan profil suhu. Running model TAPM dilakukan pada bulan Juli dan bulan Desember berkesesuaian dengan musim kemarau dan hujan, sedangkan pengamatan temperatur in situ dilakukan pada bulan September 2018 dengan menggunakan wahana drone yang berkesesuaian dengan musim kemarau, serta untuk data yang berkesesuaian dengan musim hujan menggunakan data hasil penelitian sebelumnya dengan wahana balon radiosonde. Hasil running model menunjukkan, lapisan inversi pada musim hujan lebih kuat dan lebih persisten dari pada musim kemarau. Lapisan inversi pada malam sampai pagi hari terjadi pada level permukaan, kemudian lapisan inversi ini naik dan akhirnya lapisan inversi pecah sekitar pukul 10:00 pada bulan Juli dan sekitar pukul 12:00 pada bulan Desember. Validasi dengan pengukuran in situ menunjukkan kemiripan pola. Kejadian inversi berkorelasi dengan pengendapan dan pengenceran polutan smog dan smog fotokimia dari pinggir Cekungan Bandung. Kata kunci: cekungan, urban, smog fotokimia, inversi

Characterisation of semi-volatile hydrocarbon emissions from diesel engines

Exhaust emissions from diesel vehicles have recently been receiving global attention, due to potential human health effects associated with exposure to emitted pollutants. In addition, a link has recently been established between unburnt hydrocarbon (HC) emissions from diesel engines and photochemical smog. Despite being present at very low concentrations in the exhaust, these HCs may act as precursors in the formation of photochemical smog pollution. While short-chain HCs are easier to characterise and have been successfully reduced in many developed cities, longer chain HCs, most likely arising from diesel exhaust emissions, have been poorly quantified and to date, a limited range of HCs from this source has been studied. In this study, transient cycle tests were conducted to collect exhaust emissions from a Euro 3 compliant, 1.6 L test engine fuelled with three diesel fuels (SAM10, PAR10, and EUR10), using portable denuder samplers which were analysed by thermal desorption-comprehensive 2D gas chromatography-time of flight mass spectrometry (TD-GC x GC-TofMS). The SAM10 diesel had the greatest n-alkane emissions with greater emissions observed in the earlier phases (low and medium phase) of the WLTC test cycle. PAR10 diesel had the second highest n-alkane emissions and EUR10 had the lowest n-alkane emissions amongst the three fuels. Substituted alkyl-benzenes were also detected in the gas phase emissions from each fuel. The results showed that long-chain HCs were present at easily detectable concentrations in diesel engine exhaust emissions, which is critical in understanding their contribution to photochemical ozone and informing appropriate mitigation and management strategies.

Evaluation of characterization models for the photochemical smog impact category focused on the Brazilian reality

The Life Cycle Impact Assessment (LCIA) is composed of characterization models, and in Brazil, the methodological and scientific LCIA framework is still under development. The research’s aim was to evaluate the literature available characterization models to photochemical smog category. Thus, the contribution of work is recommending one of these models to be used in Brazilian LCA studies, standardizing the studies in Brazil. The methodology consisted of searching the literature and selecting, describing and analyzing the characterization models as well as elaborating a table of criteria for better comparison. Aiming to visualize the differences in the results of each selected model, a case study was applied to analyze the photochemical smog formation potential to the transport of one ton of sugar using two transportation modes (road and railroad). Five characterization models related to smog category were selected, described and compared. Herewith, it was observed that the models present significant differences, that is, each model presents Characterization Factors (CF) for different categories within the environmental impact chain of the photochemical smog (midpoint and/or endpoint), differences in modeling, scale of the model (regional, continental or global), quantity and quality of elementary flows, etc. Those factors have influence in the CF’s calculation and, consequently, the LCA’s results, in the same case study. The criteria table’s results suggested that the model of Van Zelm et al. (2016) – World (midpoint and endpoint), is the best interim option to be used in studies of LCA in Brazil, because it was the model that resulted in the highest grade referring to the established criteria and it presents results on a Global scale. However, the results do not rule out the need for regionalization studies, which would develop a model that presents results and studies directed to the Brazilian reality or adjust the model of Van Zelm et al. (2016) - Brazil