Browsing by Subject "Black carbon"

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  • Zanatta, M.; Gysel, M.; Bukowiecki, N.; Mueller, T.; Weingartner, E.; Areskoug, H.; Fiebig, M.; Yttri, K. E.; Mihalopoulos, N.; Kouvarakis, G.; Beddows, D.; Harrison, R. M.; Cavalli, F.; Putaud, J. P.; Spindler, G.; Wiedensohler, A.; Alastuey, A.; Pandolfi, M.; Sellegri, K.; Swietlicki, E.; Jaffrezo, J. L.; Baltensperger, U.; Laj, P. (2016)
    A reliable assessment of the optical properties of atmospheric black carbon is of crucial importance for an accurate estimation of radiative forcing. In this study we investigated the spatio-temporal variability of the mass absorption cross-section (MAC) of atmospheric black carbon, defined as light absorption coefficient (sigma(ap)) divided by elemental carbon mass concentration (m(EC)). sigma(ap) and m(EC) have been monitored at supersites of the ACTRIS network for a minimum period of one year. The 9 rural background sites considered in this study cover southern Scandinavia, central Europe and the Mediterranean. sigma(ap) was determined using filter based absorption photometers and m(EC) using a thermal-optical technique. Homogeneity of the data-set was ensured by harmonization of all involved methods and instruments during extensive intercomparison exercises at the European Center for Aerosol Calibration (ECAC). Annual mean values of sigma(ap) at a wavelength of 637 nm vary between 0.66 and 1.3 Mm(-1) in southern Scandinavia, 3.7-11 Mm(-1) in Central Europe and the British Isles, and 2.3-2.8 Mm(-1) in the Mediterranean. Annual mean values of mEC vary between 0.084 and 0.23 mu g m(-3) in southern Scandinavia, 0.28 -1.1 in Central Europe and the British Isles, and 0.22-0.26 in the Mediterranean. Both sigma(ap) and mEC in southern Scandinavia and Central Europe have a distinct seasonality with maxima during the cold season and minima during summer, whereas at the Mediterranean sites an opposite trend was observed. Annual mean MAC values were quite similar across all sites and the seasonal variability was small at most sites. Consequently, a MAC value of 10.0 m(2) g(-1) (geometric standard deviation = 133) at a wavelength of 637 nm can be considered to be representative of the mixed boundary layer at European background sites, where BC is expected to be internally mixed to a large extent. The observed spatial variability is rather small compared to the variability of values in previous literature, indicating that the harmonization efforts resulted in substantially increased precision of the reported MAC. However, absolute uncertainties of the reported MAC values remain as high as +/- 30-70% due to the lack of appropriate reference methods and calibration materials. The mass ratio between elemental carbon and non-light-absorbing matter was used as a proxy for the thickness of coatings around the BC cores, in order to assess the influence of the mixing state on the MAC of BC. Indeed, the MAC was found to increase with increasing values of the coating thickness proxy. This provides evidence that coatings do increase the MAC of atmospheric BC to some extent, which is commonly referred to as lensing effect. (C) 2016 The Authors. Published by Elsevier Ltd.
  • Wiedensohler, A.; Andrade, M.; Weinhold, K.; Müller, T.; Birmili, W.; Velarde, F.; Moreno, Adam; Forno, R.; Sanchez, M. F.; Laj, P.; Ginot, P.; Whiteman, D. N.; Krejci, R.; Sellegri, K.; Reichler, T. (2018)
    Urban development, growing industrialization, and increasing demand for mobility have led to elevated levels of air pollution in many large cities in Latin America, where air quality standards and WHO guidelines are frequently exceeded. The conurbation of the metropolitan area of La Paz/El Alto is one of the fastest growing urban settlements in South America with the particularity of being located in a very complex terrain at a high altitude. As many large cities or metropolitan areas, the metropolitan area of La Paz/El Alto and the Altiplano region are facing air quality deterioration. Long-term measurement data of the equivalent black carbon (eBC) mass concentrations and particle number size distributions (PNSD) from the Global Atmosphere Watch Observatory Chacaltaya (CHC; 5240 m a.s.l., above sea level) indicated a systematic transport of particle matter from the metropolitan area of La Paz/El Alto to this high altitude station and subsequently to the lower free troposphere. To better understand the sources and the transport mechanisms, we conducted eBC and PNSDs measurements during an intensive campaign at two locations in the urban area of La Paz/El Alto from September to November 2012. While the airport of El Alto site (4040 m a.s.l.) can be seen as representative of the urban and Altiplano background, the road site located in Central La Paz (3590 m a.s.l.) is representative for heavy traffic-dominated conditions. Peaks of eBC mass concentrations up to 5 mu g m(-3) were observed at the El Alto background site in the early morning and evening, while minimum values were detected in the early afternoon, mainly due to thermal convection and change of the planetary boundary layer height. The traffic-related eBC mass concentrations at the road site reached maximum values of 10-20 mu g m(-3). A complete traffic ban on the specific Bolivian Day of Census (November 21, 2012) led to a decrease of eBC below 1 mu g m(-3) at the road site for the entire day. Compared to the day before and after, particle number concentrations decreased by a factor between 5 and 25 over the particle size range from 10 to 800 nm, while the submicrometer particle mass concentration dropped by approximately 80%. These results indicate that traffic is the dominating source of BC and particulate air pollution in the metropolitan area of La Paz/El Alto. In general, the diurnal cycle of eBC mass concentration at the Chacaltaya observatory is anti-correlated to the observations at the El Alto background site. This pattern indicates that the traffic-related particulate matter, including BC, is transported to higher altitudes with the developing of the boundary layer during daytime. The metropolitan area of La Paz/El Alto seems to be a significant source for BC of the regional lower free troposphere. From there, BC can be transported over long distances and exert impact on climate and composition of remote southern hemisphere.
  • Fung, Pak Lun; Sillanpää, Salla; Niemi, Jarkko V.; Kousa, Anu; Timonen, Hilkka; Zaidan, Martha Arbayani; Saukko, Erkka; Kulmala, Markku; Petäjä, Tuukka; Hussein, Tareq (2022)
    To convey the severity of ambient air pollution level to the public, air quality index (AQI) is used as a communication tool to reflect the concentrations of individual pollutants on a common scale. However, due to the enhanced air pollution control in recent years, air quality has improved, and the roles of some air pollutant species included in the existing AQI as urban air pollutants have diminished. In this study, we suggest the current AQI should be revised in a way that new air pollution indicators would be considered so that it would better represent the health effects caused by local combustion processes from traffic and residential burning. Based on the air quality data of 2017-2019 in three different sites in Helsinki metropolitan area, we assumed the statistical distributions of the current indicators (NO2 and PM2.5) and the proposed particulate indicators (BC, LDSA and PNC) were related as they have similar sources in urban regions despite the varying correlations between the current and proposed indicators (NO2: r = 0.5-0.85, PM2.5: r = 0.28-0.72). By fitting the data to an optimal distribution function, together with expert opinions, we improved the current Finnish AQI and determined the AQI breakpoints for the proposed indicators where this robust statistical approach is transferrable to other cities. The addition of the three proposed indicators to the current AQI would decrease the number of good air quality hours in all three environments (largest decrease in urban traffic site, similar to 22 %). The deterioration of air quality class appeared more severe during peak hours in the urban traffic site due to vehicular emission and evenings in the detached housing site where domestic wood combustion often takes place. The introduction of the AQI breakpoints of the three new indicators serve as a first step of improving the current AQI before further air quality guideline levels are updated.
  • Xie, Conghui; Xu, Weiqi; Wan, Junfeng; Liu, Dantong; Ge, Xinlei; Zhang, Qi; Wang, Qingqing; Du, Wei; Zhao, Jian; Zhou, Wei; Li, Jie; Fu, Pingqing; Wang, Zifa; Worsnop, Douglas; Sun, Yele (2019)
    The light absorption enhancement (E-abs) of black carbon (BC) caused by non-BC materials is an important source of uncertainty in radiative forcing estimate, yet remains poorly understood in relatively polluted environment such as the megacity Beijing. Here BC absorption enhancement at 630 nm was in-situ measured using a ther-modenuder coupled with a soot particle aerosol mass spectrometer and a single scattering albedo monitor in Beijing in summer. The project average (+/- 1 sigma) E-abs was 1.59 ( +/- 0.26), suggesting a significant amplification of BC absorption due to coating materials. E-abs presented a clear daytime increase due to enhanced photochemical processing, and a strong dependence on the mass ratios of non-BC coatings to BC (R-BC). Our results showed that the increase in E(abs )as a function of R-BC was mainly caused by the increased contributions of secondary aerosol. Further analysis showed that the BC absorption enhancement in summer in Beijing was mainly associated with secondary formation of nitrate, sulfate and highly oxidized secondary organic aerosol (SOA), while the formation of freshly and less oxidized SOA appeared not to play an important role.
  • Yli-Halla, Markku Juhani; Rimhanen, Karoliina; Muurinen, Johanna; Kaseva, Janne; Kahiluoto, Helena (2018)
    Soil carbon (C) represents the largest terrestrial carbon stock and is key for soil productivity. Major fractions of soil C consist of organic C, carbonates and black C. The turnover rate of black C is lower than that of organic C, and black C abundance decreases the vulnerablility of soil C stock to decomposition under climate change. The aim of this study was to determine the distribution of soil C in different pools and impact of agricultural management on the abundance of different species. Soil C fractions were quantified in the topsoils (0-15 cm) of 23 sites in the tropical highlands of Ethiopia. The sites in central Ethiopia represented paired plots of agroforestry and adjacent control plots where cereal crops were traditionally grown in clayey soils. In the sandy loam and loam soils of northern Ethiopia, the pairs represented restrained grazing with adjacent control plots with free grazing, and terracing with cereal-based cropping with adjacent control plots without terracing. Soil C contained in carbonates, organic matter and black C along with total C was determined. The total C median was 1.5% (range 0.33.6%). The median proportion of organic C was 85% (range 53-94%). 6% (0-41%) for carbonate C and 6% (421%) for black C. An increase was observed in the organic C and black C fractions attributable to agroforestry and restrained grazing. The very low concentration of the relatively stable black C fraction and the dominance of organic C in these Ethiopian soils suggest vulnerability to degradation and the necessity for cultivation practices maintaining the C stock. (C) 2018 Elsevier B.V. All rights reserved.
  • Hussein, Tareq; Boor, Brandon E.; dos Santos, Vanessa N.; Kangasluoma, Juha; Petäjä, Tuukka; Lihavainen, Heikki (2017)
    Air pollution research and reports have been limited in the Middle East, especially in Jordan with respect to aerosol particle number concentrations. In this study, we utilized a simple "mobile setup" to measure, for the first time, the spatial variation of aerosol concentrations in Eastern Mediterranean. The mobile setup consisted of portable aerosol instruments to measure particle number concentrations (cut off sizes 0.01, 0.02, 0.3, 0.5, 1, 2.5, 5, and 10 mu m), particle mass concentrations (PM1, PM2.5, and PM10), and black carbon concentration all situated on the back seat of a sedan car. The car was driven with open windows to ensure sufficient cabin air ventilation for reliable outdoor aerosol sampling. Although the measurement campaign was two days long, but it provided preliminary information about aerosols concentrations over a large spatial scale that covered more than three quarters of Jordan. We should keep in mind that the presented concentrations reflect on road conditions. The submicron particle concentrations were the highest in the urban locations (e.g., Amman and Zarqa) and inside cities with heavy duty vehicles activities (e.g., Azraq). The highest micron particle concentrations were observed in the southern part of the country and in places close to the desert area (e.g., Wadi Rum and Wadi Araba). The average submicron concentration was 4.9 x 10(3)-120 x 10(3) cm-3 (5.7-86.7 mu g m(-3)) whereas the average micron particle concentration was 1-11 cm(-3) (8-150 mu g m(-3), assume rho(p) = 1 g cm(-3)). The main road passing through Jafr in the eastern part of Jordan exhibited submicron concentration as low as 800 cm(-3). The PM10 concentration consisted of about 40-75% as PM1. The black carbon (BC) concentration variation was in good agreement with the PM1 as well as the submicron particle number concentration.
  • Pirjola, Liisa; Kuuluvainen, Heino; Timonen, Hilkka; Saarikoski, Sanna; Teinilä, Kimmo; Salo, Laura; Datta, Arindam; Simonen, Pauli; Karjalainen, Panu; Kulmala, Kari; Rönkkö, Topi (2019)
    The use of fossil fuels in traffic is a significant source of air pollutants and greenhouse gases in rapidly growing and densely populated cities. Diesel exhaust emissions including particle number concentration and size distribution along with the particles’ chemical composition and NOx were investigated from a Euro 4 passenger car with a comprehensive set of high time-resolution instruments. The emissions were compared with three fuel standards – European diesel (EN590), Indian diesel (BS IV) and Finnish renewable diesel (Neste MY) – over the New European Driving Cycle (NEDC) and the Worldwide harmonized Light vehicles Test Cycle (WLTC). Fuel properties and driving conditions strongly affected exhaust emissions. The exhaust particulate mass emissions for all fuels consisted of BC (81–88%) with some contribution from organics (11–18%) and sulfate (0–3%). As aromatic-free fuel, the MY diesel produced around 20% lower black carbon (BC) emissions compared to the EN590 and 29–40% lower compared to the BS IV. High volatile nanoparticle concentrations at high WLTC speed conditions were observed with the BS IV and EN590 diesel, but not with the sulfur-free MY diesel. These nanoparticles were linked to sulfur-driven nucleation of new particles in cooling dilution of the exhaust. For all the fuels non-volatile nanoparticles in sub-10 nm particle sizes were observed during engine braking, and they were most likely formed from lubricant-oil-originated compounds. With all the fuels, the measured particulate and NOx emissions were significantly higher during the WLTC cycle compared to the NEDC cycle. This study demonstrated that renewable diesel fuels enable mitigations of particulate and climate-warming BC emissions of traffic, and will simultaneously help tackle urban air quality problems.