| 1. |
- Falk, John, et al.
(författare)
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Immersion freezing ability of freshly emitted soot with various physico-chemical characteristics
- 2021
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Ingår i: Atmosphere. - : MDPI AG. - 2073-4433. ; 12:9
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Tidskriftsartikel (refereegranskat)abstract
- The immersion freezing ability of soot particles has in previous studies been reported in the range of low/insignificant to very high. The aims of this study were to: (i) perform detailed physico-chemical characterisation of freshly produced soot particles with very different properties, (ii) investigate the immersion freezing ability of the same particles, and (iii) investigate the potential links between physico-chemical particle properties and ice-activity. A miniCAST soot generator was used to produce eight different soot samples representing a wide range of physico-chemical properties. A continuous flow diffusion chamber was used to study each sample online in immersion mode over the temperature (T) range from −41 to −32◦C, at a supersaturation of about 10% with respect to liquid water. All samples exhibited low to no heterogeneous immersion freezing. The most active sample reached ice-activated fractions (AF) of 10−3 and 10−4 at temperatures of 1.7 and 1.9 K, respectively, above the homogeneous freezing temperature. The samples were characterized online with respect to a wide range of physico-chemical properties including effective particle density, optical properties, particle surface oxidation and soot maturity. We did observe indications of increasing immersion freezing ice-activity with increasing effective particle density and increasing particulate PAH fraction . Hence, those properties, or other properties co-varying with those, could potentially enhance the immersion freezing ice-activity of the studied soot particle types. However, we found no significant correlation between the physico-chemical properties and the observed ice-nucleating ability when the particle ensemble was extended to include previously published results including more ice-active biomass combustion soot particles. We conclude that it does not appear possible in general and in any straightforward way to link observed soot particle physico-chemical properties to the ice-nucleating ability using the online instrumentation included in this study. Furthermore, our observations support that freshly produced soot particles with a wide range of physico-chemical properties have low to insignificant immersion freezing ice-nucleating ability.
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| 2. |
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| 3. |
- Gren, Louise, et al.
(författare)
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Effects of renewable fuel and exhaust aftertreatment on primary and secondary emissions from a modern heavy-duty diesel engine
- 2021
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Ingår i: Journal of Aerosol Science. - : Elsevier BV. - 0021-8502. ; 156
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Tidskriftsartikel (refereegranskat)abstract
- Compared to petroleum diesel, renewable diesel fuels and exhaust aftertreatment systems can reduce primary exhaust emissions that are hazardous to human health and the environment. Secondary aerosol emissions which form upon atmospheric processing have, however, been less studied. This study aimed to quantify the impacts of replacing petroleum diesel with renewable fuels (hydrotreated vegetable oil [HVO] and rapeseed methyl ester [RME]) on primary and secondary aerosol emissions from a heavy-duty diesel engine at different stages of an exhaust aftertreatment system. Emission characterization was obtained by combining a battery of physical characterization techniques with chemical characterization using aerosol mass spectrometry. At engine-out measurements, RME and HVO reduced primary particulate matter (PM) emissions (for example equivalent black carbon [eBC]) and secondary aerosol production (studied with an oxidation flow reactor [OFR]) by mass compared to petroleum diesel. The diesel oxidation catalyst (DOC) reduced primary nucleation mode emissions, reduced the effective density of soot mode emissions, and reduced secondary particle production by mass. The DOC + a diesel particulate filter removed >99% of the particle number and eBC emissions. Volatile PM emissions (for example organic aerosol) were found to be distributed between the nucleation mode and soot mode for both primary and secondary emissions, to a degree that depends on both fuel type and aftertreatment. A high mass concentration of condensable species and a low condensation sink in the soot mode led to increased fractions of condensable species present in the nucleation mode. Aging in the OFR led to increases in particle effective density. Motoring the engine (running without combustion) showed that the nucleation mode originated primarily from lubricating oil, and nonvolatile nanoparticle emissions were identified down to 1.2 nm in particle size. In conclusion, replacing petroleum diesel with HVO and RME changes emission characteristics and can help reduce key aerosol emissions of relevance for adverse health and climate impact, especially for diesel engines with no or limited exhaust aftertreatment.
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| 4. |
- Karjalainen, Panu, et al.
(författare)
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Time-resolved characterization of primary particle emissions and secondary particle formation from a modern gasoline passenger car
- 2016
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 16:13, s. 8559-8570
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Tidskriftsartikel (refereegranskat)abstract
- Changes in vehicle emission reduction technologies significantly affect traffic-related emissions in urban areas. In many densely populated areas the amount of traffic is increasing, keeping the emission level high or even increasing. To understand the health effects of traffic-related emissions, both primary (direct) particulate emission and secondary particle formation (from gaseous precursors in the exhaust emissions) need to be characterized. In this study, we used a comprehensive set of measurements to characterize both primary and secondary particulate emissions of a Euro 5 level gasoline passenger car. Our aerosol particle study covers the whole process chain in emission formation, from the tailpipe to the atmosphere, and also takes into account differences in driving patterns. We observed that, in mass terms, the amount of secondary particles was 13 times higher than the amount of primary particles. The formation, composition, number and mass of secondary particles was significantly affected by driving patterns and engine conditions. The highest gaseous and particulate emissions were observed at the beginning of the test cycle when the performance of the engine and the catalyst was below optimal. The key parameter for secondary particle formation was the amount of gaseous hydrocarbons in primary emissions; however, also the primary particle population had an influence.
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| 5. |
- Korhonen, Kimmo, et al.
(författare)
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Particle emissions from a modern heavy-duty diesel engine as ice nuclei in immersion freezing mode: a laboratory study on fossil and renewable fuels
- 2022
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7324. ; 22:23, s. 1615-1631
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Tidskriftsartikel (refereegranskat)abstract
- We studied ice-nucleating abilities of particulate emissions from a modern heavy-duty diesel engine using three different types of fuel. The polydisperse particle emissions were sampled during engine operation and introduced to a continuous-flow diffusion chamber (CFDC) instrument at a constant relative humidity RHwater=110 %, while the temperature was ramped between −43 and −32 ∘C (T scan). The tested fuels were EN 590 compliant low-sulfur fossil diesel, hydrotreated vegetable oil (HVO), and rapeseed methyl ester (RME); all were tested without blending. Sampling was carried out at different stages in the engine exhaust aftertreatment system, with and without simulated atmospheric processing using an oxidation flow reactor. In addition to ice nucleation experiments, we used supportive instrumentation to characterize the emitted particles for their physicochemical properties and presented six parameters. We found that the studied emissions contained no significant concentrations of ice-nucleating particles likely to be of atmospheric relevance. The substitution of fossil diesel with renewable fuels, using different emission aftertreatment systems such as a diesel oxidation catalyst, and photochemical aging of total exhaust had only minor effect on their ice-nucleating abilities.
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| 6. |
- Lepistö, Teemu, et al.
(författare)
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Particle lung deposited surface area (LDSAal) size distributions in different urban environments and geographical regions : Towards understanding of the PM2.5 dose–response
- 2023
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Ingår i: Environment International. - : Elsevier. - 0160-4120 .- 1873-6750. ; 180
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Tidskriftsartikel (refereegranskat)abstract
- Recent studies indicate that monitoring only fine particulate matter (PM2.5) may not be enough to understand and tackle the health risk caused by particulate pollution. Health effects per unit PM2.5 seem to increase in countries with low PM2.5, but also near local pollution sources (e.g., traffic) within cities. The aim of this study is to understand the differences in the characteristics of lung-depositing particles in different geographical regions and urban environments. Particle lung deposited surface area (LDSAal) concentrations and size distributions, along with PM2.5, were compared with ambient measurement data from Finland, Germany, Czechia, Chile, and India, covering traffic sites, residential areas, airports, shipping, and industrial sites. In Finland (low PM2.5), LDSAal size distributions depended significantly on the urban environment and were mainly attributable to ultrafine particles (<100 nm). In Central Europe (moderate PM2.5), LDSAal was also dependent on the urban environment, but furthermore heavily influenced by the regional aerosol. In Chile and India (high PM2.5), LDSAal was mostly contributed by the regional aerosol despite that the measurements were done at busy traffic sites. The results indicate that the characteristics of lung-depositing particles vary significantly both within cities and between geographical regions. In addition, ratio between LDSAal and PM2.5 depended notably on the environment and the country, suggesting that LDSAal exposure per unit PM2.5 may be multiple times higher in areas having low PM2.5 compared to areas with continuously high PM2.5. These findings may partly explain why PM2.5 seems more toxic near local pollution sources and in areas with low PM2.5. Furthermore, performance of a typical sensor based LDSAal measurement is discussed and a new LDSAal2.5 notation indicating deposition region and particle size range is introduced. Overall, the study emphasizes the need for country-specific emission mitigation strategies, and the potential of LDSAal concentration as a health-relevant pollution metric.
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| 7. |
- Novakovic, Maja, et al.
(författare)
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Fresh and Aged Organic Aerosol Emissions from Renewable Diesel-Like Fuels HVO and RME in a Heavy-Duty Compression Ignition Engine
- 2023
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Ingår i: Technical paper - WCX SAE World Congress Experience. - 2688-3627 .- 0148-7191. ; :2023-01-0392
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Konferensbidrag (refereegranskat)abstract
- A modern diesel engine is a reliable and efficient mean of producing power. A way to reduce harmful exhaust and greenhouse gas (GHG) emissions and secure the sources of energy is to develop technology for an efficient diesel engine operation independent of fossil fuels. Renewable diesel fuels are compatible with diesel engines without any major modifications. Rapeseed oil methyl esters (RME) and other fatty acid methyl esters (FAME) are commonly used in low level blends with diesel. Lately, hydrotreated vegetable oil (HVO) produced from vegetable oil and waste fat has found its way into the automotive market, being approved for use in diesel engines by several leading vehicle manufacturers, either in its pure form or in a mixture with the fossil diesel to improve the overall environmental footprint. There is a lack of data on how renewable fuels change the semi-volatile organic fraction of exhaust emissions. In order to characterize and explain the difference in exhaust emissions from fossil diesel, HVO and RME fuels, particulate matter (PM) emissions were sampled at two exhaust positions of an experimental single cylinder Scania D13 heavy-duty (HD) diesel engine: at the exhaust manifold, and after a diesel oxidation catalyst (DOC). Advanced analyzing techniques were used to characterize the composition of the organic PM. Special attention was paid to an operating point at 18% intake oxygen level with constant engine operating conditions where the emission level of nitrogen oxides (NOx) was low, and carbon monoxide (CO) and total hydrocarbon (THC) were relatively low. On-line aerosol mass spectrometry (AMS) suggests that the chemical composition of the organic aerosols (OAs) was similar for HVO and diesel. However, RME both reduced the OA emissions and changed the composition with evidence for fuel signatures in the mass spectra. When the emissions were aged in an oxidation flow reactor to simulate secondary organic aerosol (SOA) formation in the atmosphere, it was found that OA concentration strongly increased for all fuels. However, SOA formation was substantially lower for RME compared to the other fuels. The DOC strongly reduced primary organic emissions in both the gas (THC) and particle phase (OA) and only marginally affected OA composition. The DOC was also effective in reducing secondary organic aerosol formation upon atmospheric aging.
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| 8. |
- Roslin, Tomas, et al.
(författare)
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A molecular-based identification resource for the arthropods of Finland
- 2022
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Ingår i: Molecular Ecology Resources. - : Wiley. - 1755-098X .- 1755-0998. ; 22:2, s. 803-822
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Tidskriftsartikel (refereegranskat)abstract
- To associate specimens identified by molecular characters to other biological knowledge, we need reference sequences annotated by Linnaean taxonomy. In this study, we (1) report the creation of a comprehensive reference library of DNA barcodes for the arthropods of an entire country (Finland), (2) publish this library, and (3) deliver a new identification tool for insects and spiders, as based on this resource. The reference library contains mtDNA COI barcodes for 11,275 (43%) of 26,437 arthropod species known from Finland, including 10,811 (45%) of 23,956 insect species. To quantify the improvement in identification accuracy enabled by the current reference library, we ran 1000 Finnish insect and spider species through the Barcode of Life Data system (BOLD) identification engine. Of these, 91% were correctly assigned to a unique species when compared to the new reference library alone, 85% were correctly identified when compared to BOLD with the new material included, and 75% with the new material excluded. To capitalize on this resource, we used the new reference material to train a probabilistic taxonomic assignment tool, FinPROTAX, scoring high success. For the full-length barcode region, the accuracy of taxonomic assignments at the level of classes, orders, families, subfamilies, tribes, genera, and species reached 99.9%, 99.9%, 99.8%, 99.7%, 99.4%, 96.8%, and 88.5%, respectively. The FinBOL arthropod reference library and FinPROTAX are available through the Finnish Biodiversity Information Facility (www.laji.fi) at https://laji.fi/en/theme/protax. Overall, the FinBOL investment represents a massive capacity-transfer from the taxonomic community of Finland to all sectors of society.
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| 9. |
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| 10. |
- Timonen, Hilkka, et al.
(författare)
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Influence of fuel ethanol content on primary emissions and secondary aerosol formation potential for a modern flex-fuel gasoline vehicle
- 2017
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 17:8, s. 5311-5329
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Tidskriftsartikel (refereegranskat)abstract
- The effect of fuel ethanol content (10, 85 and 100 %) on primary emissions and on subsequent secondary aerosol formation was investigated for a Euro 5 flex-fuel gasoline vehicle. Emissions were characterized during a New European Driving Cycle (NEDC) using a comprehensive setup of high time-resolution instruments. A detailed chemical composition of the exhaust particulate matter (PM) was studied using a soot particle aerosol mass spectrometer (SPAMS), and secondary aerosol formation was studied using a potential aerosol mass (PAM) chamber. For the primary gaseous compounds, an increase in total hydrocarbon emissions and a decrease in aromatic BTEX (benzene, toluene, ethylbenzene and xylenes) compounds was observed when the amount of ethanol in the fuel increased. In regard to particles, the largest primary particulate matter concentrations and potential for secondary particle formation was measured for the E10 fuel (10% ethanol). As the ethanol content of the fuel increased, a significant decrease in the average primary particulate matter concentrations over the NEDC was found. The PM emissions were 0.45, 0.25 and 0.15 mgm-3 for E10, E85 and E100, respectively. Similarly, a clear decrease in secondary aerosol formation potential was observed with a larger contribution of ethanol in the fuel. The secondary-toprimary PM ratios were 13.4 and 1.5 for E10 and E85, respectively. For E100, a slight decrease in PM mass was observed after the PAM chamber, indicating that the PM produced by secondary aerosol formation was less than the PM lost through wall losses or the degradation of the primary organic aerosol (POA) in the chamber. For all fuel blends, the formed secondary aerosol consisted mostly of organic compounds. For E10, the contribution of organic compounds containing oxygen increased from 35 %, measured for primary organics, to 62% after the PAM chamber. For E85, the contribution of organic compounds containing oxygen increased from 42% (primary) to 57% (after the PAM chamber), whereas for E100 the amount of oxidized organics remained the same (approximately 62 %) with the PAM chamber when compared to the primary emissions.
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