| 61. |
- Cavalli, F., et al.
(författare)
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A European aerosol phenomenology-4 : Harmonized concentrations of carbonaceous aerosol at 10 regional background sites across Europe
- 2016
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 144, s. 133-145
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Tidskriftsartikel (refereegranskat)abstract
- Although particulate organic and elemental carbon (OC and EC) are important constituents of the suspended atmospheric particulate matter (PM), measurements of OC and EC are much less common and More uncertain than measurements of e.g. the ionic components of PM. In the framework of atmospheric research infrastructures supported by the European Union, actions have been undertaken to determine and mitigate sampling artefacts, and assess the comparability of OC and EC data obtained in a network of 10 atmospheric observatories across Europe. Positive sampling artefacts (from 0:4 to 2.8 mu g C/m(3)) and analytical discrepancies (between -50% and +40% for the EC/TC ratio) have been taken into account to generate a robust data set, from which we established the phenomenology of carbonaceous aerosols at regional background sites in Europe. Across the network, TC and EC annual average concentrations range from 0.4 to 9 mu g C/m(3), and from 0.1 to 2 mu g C/m(3), respectively. TC/PM10 annual mean ratios range from 0.11 at a Mediterranean site to 0.34 at the most polluted continental site, and TC/PM2.5 ratios are slightly greater at all sites (0.15-0.42). EC/TC annual mean ratios range from 0.10 to 0.22, and do not depend much on PM concentration levels, especially in winter. Seasonal variations in PM and TC concentrations, and in TC/PM and EC/TC ratios, differ across the network, which can be explained by seasonal changes in PM source contributions at some sites.
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| 62. |
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| 63. |
- Chham, E., et al.
(författare)
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Sources of the seasonal-trend behaviour and periodicity modulation of 7Be air concentration in the atmospheric surface layer observed in southeastern Spain
- 2019
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; , s. 148-158
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Tidskriftsartikel (refereegranskat)abstract
- The components and the periodicity characterising airborne 7Be monthly concentration collected in Granada (SE Spain) between 2000 and 2018 are studied. These 19 years of measurements are particularly significant for the 7Be analysis as they cover the complete 24th solar cycle, 2008–2018. A Time Series Decomposition (TSD) technique has been applied to determine the different components present in the dataset: the trend, seasonal and irregular components. Then, the atmospheric parameters (Precipitation (Pp), Relative Humidity (RH), Temperature (Temp), Wind speed (WS), Total Cloudiness (TC), Low Cloudiness (LC)), teleconnection indices and the solar activity (Sun Spot Number, SSN) were used to justify the variability of each component. SSN and the teleconnection indices (Western Mediterranean Oscillation (WeMO), Atlantic Multidecadal Oscillation (AMO) and Quasi Biennial Oscillation (QBO)) are found to have a major impact on the trend component of 7Be. In turn, all the atmospheric parameters were found to have strong impact on the seasonal component. In order to observe the change in the impact of the parameters from the 24th solar cycle (from 2008 to 2018) to the complete time series (starting in 2000), the comparison between the two periods has been carried out. The results show that, over the 24th solar cycle, the SSN impacted predominantly on the trend component, whereas atmospheric parameters showed a slightly higher impact on the seasonal component. In addition, some atmospheric factors (Temp, RH, Pp, TC, LC) appeared to partially affect the irregular component. The analysis of the two phases of the 24th solar cycle shows that the influence of SSN is higher during the descending phase than during the ascending one. This behaviour is opposed to the one found for the 23rd solar cycle, which clarifies the special characteristics of the 24th cycle. Besides that, the Continuous Wavelet Transform (CWT) analysis was applied in order to extract the possible periodicities characterising 7Be data. The analysis revealed three sets of periodicities. Then, the Wavelet Coherence Analysis (WCA) method was particularly useful to study coherences between 7Be data and teleconnection indices. The 7Be concentrations in the large period (11–14 years) detected by CWT was found to be mainly modulated by WeMO, AMO and QBO, while the NAO modulates the smaller periods. © 2019 Elsevier Ltd
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| 64. |
- Cho, Chaeyoon, et al.
(författare)
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Observation-based estimates of the mass absorption cross-section of black and brown carbon and their contribution to aerosol light absorption in East Asia
- 2019
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 212, s. 65-74
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we estimated the contribution of black carbon (BC) and brown carbon (BrC) to aerosol light absorption from surface in-situ and aerosol robotic network (AERONET) columnar observations. The mass absorption cross-section (MAC) of BC (MAC(BC)) was estimated to be 6.4 +/- 1.5 m(2) g(-1) at 565 mn from in-situ aerosol measurements at Gosan Climate Observatory (GCO), Korea, in January 2014, which was lower than those observed in polluted urban areas. A BrC MAC of 0.62 +/- 0.06 m(2) g(-1) (565 mn) in our estimate is approximately ten times lower than MACK at 565 nm. The contribution of BC and BrC to the carbonaceous aerosol absorption coefficient at 565 nm from the in-situ measurements was estimated at 88.1 +/- 7.4% and 11.9 +/- 7.4%, respectively at GCO. Similarly, the contribution of BC and BrC to the absorption aerosol optical depth (AAOD) for carbonaceous aerosol (CA), constrained by AERONET observations at 14 sites over East Asia by using different spectral dependences of the absorption (i.e., absorption Angstrom exponent) of BC and BrC, was 84.9 +/- 2.8% and 15.1 +/- 2.8% at 565 nm, respectively. The contribution of BC to CA AAOD was greater in urban sites than in the background areas, whereas the contribution of BrC to CA AAOD was higher in background sites. The overall contribution of BC to CA AAOD decreased by 73%-87% at 365 nm, and increased to 93%-97% at 860 nm. The contribution of BrC to CA AAOD decreased significantly with increasing wavelength from approximately 17% at 365 nm to 4% at 860 nm.
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| 65. |
- Cicenaite, Aurelija, et al.
(författare)
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Feasibility of a simple laboratory approachnext term for determining temperature influence on SPMD–air partition coefficients of selected compounds
- 2007
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 41, s. 2844-50
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Tidskriftsartikel (refereegranskat)abstract
- Semipermeable membrane devices (SPMDs) are previous termanext term widely used passive sampling methodology for both waterborne and airborne hydrophobic organic contaminants. The exchange kinetics and partition coefficients of an analyte in previous termanext term SPMD are mediated by its physicochemical properties and certain environmental conditions. Controlled previous termlaboratorynext term experiments are used for determining the SPMD–air (Ksa's) partition coefficients and the exchange kinetics of organic vapors. This study focused on determining previous terma simple approachnext term for measuring equilibrium Ksa's for naphthalene (Naph), o-chlorophenol (o-CPh) and p-dichlorobenzene (p-DCB) over previous termanext term wide range of temperatures. SPMDs were exposed to test chemical vapors in small, gas-tight chambers at four different temperatures (−16, −4, 22 and 40 °C). The exposure times ranged from 6 h to 28 d depending on test temperature. Ksa's or non-equilibrium concentrations in SPMDs were determined for all compounds, temperatures and exposure periods with the exception of Naph, which could not be quantified in SPMDs until 4 weeks at the −16 °C temperature. To perform this study the assumption of constant and saturated atmospheric concentrations in test chambers was made. It could influence the results, which suggest that flow through experimental system and performance reference compounds should be used for SPMD calibration.
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| 66. |
- Cirino, Glauber, et al.
(författare)
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Observations of Manaus urban plume evolution and interaction with biogenic emissions in GoAmazon 2014/5
- 2018
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 191, s. 513-524
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Tidskriftsartikel (refereegranskat)abstract
- As part of the Observations and Modeling of the Green Ocean Amazon (GoAmazon 2014/5) Experiment, detailed aerosol and trace gas measurements were conducted near Manaus, a metropolis located in the central Amazon Basin. Measurements of aerosol particles and trace gases were done downwind Manaus at the sites T2 (Tiwa Hotel) and T3 (Manacapuru), at a distance of 8 and 70 km from Manaus, respectively. Based on in-plume measurements closer to Manaus (site T2), the chemical signatures of city emissions were used to improve the interpretation of pollutant levels at the T3 site. We derived chemical and physical properties for the city's atmospheric emission ensemble, taking into account only air masses impacted by the Manaus plume at both sites, during the wet and dry season Intensive Operating Periods (IOPs). At T2, average concentrations of aerosol number (CN), CO and SO2 were 5500 cm(-3) (between 10 and 490 nm), 145 ppb and 0.60 ppb, respectively, with a typical ratio ACN/ACO of 60-130 particles cm(-3) ppb(-1). The aerosol scattering (at RH < 60%) and absorption at 637 nm at T2 ranged from 10 to 50 M m(-1) and 5-10 M m(-1), respectively, leading to a mean single scattering albedo (SSA) of 0.70. In addition to identifying periods dominated by Manaus emissions at both T2 and T3, the plume transport between the two sampling sites was studied using back trajectory calculations. Results show that the presence of the Manaus plume at site T3 was important mainly during the daytime and at the end of the afternoons. During time periods directly impacted by Manaus emissions, an average aerosol number concentration of 3200 cm(-3) was measured at T3. Analysis of plume evolution between T2 and T3 indicates a transport time of 4-5 h. Changes of submicron organic and sulfate aerosols ratios relative to CO (Delta OA/Delta CO and Delta SO4/Delta CO, respectively) indicate significant production of secondary organic aerosol (SOA), corresponding to a 40% mass increase in OA and a 30% in SO4 mass concentration. Similarly, during air mass arrival at T3 the SSA increased to 0.83 from 0.70 at T2, mainly associated with an increase in organic aerosol concentration. Aerosol particle size distributions show a strong decrease in the Aitken nuclei mode (10-100 nm) during the transport from T2 to T3, in particular above 30 nm, as a result of efficient coagulation processes into larger particles. A decrease of 30% in the particle number concentration and an increase of about 50 nm in geometric mean diameter were observed from T2 to T3 sites. The study of the evolution of aerosol properties downwind of the city of Manaus improves our understanding of how coupling of anthropogenic and biogenic sources may be impacting the sensitive Amazonian atmosphere.
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| 67. |
- Ciuzas, Darius, et al.
(författare)
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Characterization of indoor aerosol temporal variations for the real-time management of indoor air quality
- 2015
-
Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 118, s. 107-117
-
Tidskriftsartikel (refereegranskat)abstract
- The study presents the characterization of dynamic patterns of indoor particulate matter (PM) during various pollution episodes for real-time IAQ management. The variation of PM concentrations was assessed for 20 indoor activities, including cooking related sources, other thermal sources, personal care and household products. The pollution episodes were modelled in full-scale test chamber representing a standard usual living room with the forced ventilation of 0.5 h(-1). In most of the pollution episodes, the maximum concentration of particles in exhaust air was reached within a few minutes. The most rapid increase in particle concentration was during thermal source episodes such as candle, cigarette, incense stick burning and cooking related sources, while the slowest decay of concentrations was associated with sources, emitting ultrafine particle precursors, such as furniture polisher spraying, floor wet mopping with detergent etc. Placement of the particle sensors in the ventilation exhaust vs. in the centre of the ceiling yielded comparable results for both measured maximum concentrations and temporal variations, indicating that both locations were suitable for the placement of sensors for the management of IAQ. The obtained data provides information that may be utilized considering measurements of aerosol particles as indicators for the real-time management of IAQ. (C) 2015 Elsevier Ltd. All rights reserved.
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| 68. |
- Córdoba-Jabonero, Carmen, et al.
(författare)
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Performance of a dust model to predict the vertical mass concentration of an extreme Saharan dust event in the Iberian Peninsula : Comparison with continuous, elastic, polarization-sensitive lidars
- 2019
-
Ingår i: Atmospheric Environment. - : Elsevier. - 1352-2310 .- 1873-2844. ; 214
-
Tidskriftsartikel (refereegranskat)abstract
- An intense dusty event unusually occurred in wintertime over the Iberian Peninsula was detected over two Spanish NASA/MPLNET sites: the temporary Torrejón Observational Tower for Environmental Monitoring (TOTEM, 40.5°N 3.5°W) and the Barcelona station (BCN, 41.4°N 2.1°E). The highest dust incidence was observed from 22 to 23 February 2017; this two-day dusty scenario is examined in order to evaluate the performance of the operational NMMB/BSC-Dust model on forecasted mass concentration profiling in comparison with polarized Micro-Pulse (P-MPL) mass estimates for dust particles. First, the optical properties of the dust (DD) were effectively separated from the non-dust (ND) component by using the combined P-MPL/POLIPHON method. Lidar-derived DD optical depths reached maximums of 1.6–1.7 (±0.1) at both stations. Typical features for dust were obtained: linear particle depolarization ratios between 0.3 and 0.4, and lidar ratios in the range of 41–70 sr and 36–66 sr, respectively, for TOTEM and BCN. Lower AERONET Ångström exponents were reported for TOTEM (0.12 ± 0.04) than at BCN (0.5 ± 0.3). HYSPLIT back-trajectory analysis showed air masses coming from the Sahara region, mostly transporting dust particles. AERONET-derived Mass Extinction Efficiencies (MEE) under dusty conditions were used for the extinction-to-mass conversion procedure as applied to the P-MPL measurements: MEE values were lower at TOTEM (0.57 ± 0.01 m2 g−1) than those found at BCN (0.87 ± 0.10 m2 g−1). Those results reveal that dust particles were predominantly larger at TOTEM than those observed at BCN, and a longer transport of dust particles from the Sahara sources to BCN could favour a higher gravitational settling of coarser particles before reaching BCN than TOTEM. A comparative analysis between profiles as obtained from the lidar DD component of the mass concentration and those forecasted by the NMMB/BSC-Dust model (25 available dusty profiles) was performed. The degree of agreement between both datasets was determined by the percentage of dusty cases satisfying selected model performance criteria (favourable cases) of two proxies: the Mean Fractional Bias, MFB" role="presentation" style="box-sizing: border-box; margin: 0px; padding: 0px; display: inline; line-height: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;">MFBMFB, and the correlation coefficient, CC" role="presentation" style="box-sizing: border-box; margin: 0px; padding: 0px; display: inline; line-height: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;">CCCC. A good agreement is found (72% and 76%, respectively, of favourable cases); however, large discrepancies are found at low altitudes between the dust model and the lidar observations, mostly at early stages of the arrival of the dust intrusion. Higher model-derived centre-of-mass (CoM) heights are found in 60% of the cases (with differences < 15% w.r.t. the lidar CoM, whose values ranged between 1.8 and 2.3 km height). In addition, modelled mass loading (ML) values were generally higher than the lidar-derived ones. However, the evolution of the mass loading along the two days, 22 and 23 February, was rather similar for both the model forecasting and lidar observations at both stations. The relative ML differences (<50%) of the mass loading represented 60% of all cases. Discrepancies can be based on the uncertainties in the lidar retrievals (mainly, the use of single extinction-to-mass conversion factors). In general, a moderately good agreement is observed between the P-MPL-derived dust mass concentration profiles and the NMMB/BSC-Dust model ones at both sites; large discrepancies are found at lower altitudes, plausibly due to a lower sedimentation of dust particles coming from upper layers by gravitational settling than that introduced by the NMMB/BSC-Dust model in the simulations. The methodology described for the dust model evaluation against the continuous P-MPL observations can be easily adopted for an operational use of the NMMB/BSC-Dust model for forecasting the mass concentration profiling in frequently dust-affected regions with serious climate and environmental implications, as long as a typical MEE for dust could be accurately specified. Hence, a statistical analysis for determining AERONET-based MEE values over the Iberian Peninsula is on-going.
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| 69. |
- Cui, Song, et al.
(författare)
-
Polycyclic aromatic hydrocarbons in fresh snow in the city of Harbin in northeast China
- 2019
-
Ingår i: Atmospheric Environment. - : Elsevier. - 1352-2310 .- 1873-2844. ; 215
-
Tidskriftsartikel (refereegranskat)abstract
- Characterizing levels of polycyclic aromatic hydrocarbons (PAHs) in snow and their toxicity is important for understanding snow scavenging of PAHs and associated human health and environmental risks in cold regions. A total of 48 fresh snow samples were collected from six precipitation events during the winter of 2014-2015 at eight (5 urban, 2 suburban and 1 rural) sites across the heavily industrialized and agricultural city of Harbin in northeast China, and were analyzed for the USEPA priority 16 PAHs. Concentrations of the sum of the 16 PAHs from individual snow samples ranged from 0.3 to 2549.6 pg L-1 or nearly four orders of magnitude. The arithmetic mean concentration (+/- standard deviation) of the 48 samples was 218.1 +/- 623.7 mu g L-1, and the median value was 10.7 mu g L-1. The most abundant PAHs averaged from all the samples were Pyrene (17.1%), followed by Phenanthrene (14.9%), Naphthalene (14.4%), and Fluoranthene (10.2%). The important carcinogenic Sigma(7)PAHs accounted for 58.4% of the total PAHs at locations directly impacted by road traffic. Source apportionment analysis using diagnostic ratios coupled with principal component analysis (PCA) indicated that coal and biomass combustion and vehicle exhausts are the major sources of PAHs in winter. Concentrations of PAHs in snow were significantly correlated with measured levels of PAHs in airborne particulate matter (PM2.5 (R = 0.857, p < 0.05); PM10 (R = 0.831, p < 0.05)), as well as with ambient temperature (R = -0.851, p < 0.05). Almost all (99%) of PAHs measured in the snow were present in particulate phase. The practice of clearing snow by removing it from urban areas and disposing it in suburban and rural areas may create a new pathway of exposure, which needs to be assessed further.
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| 70. |
- Cui, Song, et al.
(författare)
-
Spatial and temporal variations of open straw burning based on fire spots in northeast China from 2013 to 2017
- 2021
-
Ingår i: Atmospheric Environment. - : Elsevier. - 1352-2310 .- 1873-2844. ; 244
-
Tidskriftsartikel (refereegranskat)abstract
- Open straw burning releases significant amounts of particulate matter (PM) and trace gases into the air and thus is an important source of atmospheric pollutants in China. In this study, based on fire spots in northeast China from 2013 to 2017, we analyzed pollution concentration degree (PCD) and pollution concentration period (PCP), and assessed spatial and temporal variations of open straw burning. Straw types and burning areas were then determined according to the distributions of fire spots and land use dataset. The amounts of several major atmospheric pollutants (PM10, PM25, CO, NOx and NMVOCs (non-methane volatile organic compounds)) emitted into the atmosphere from open straw burning were estimated according to crop production, Residue/Grain ratio (R/G), combustion efficiency and emission factor. Open straw burning occurred frequently in dry and paddy fields, mainly in areas of West and Northeast Heilongjiang Province, Midwest Jilin Province and Central Liaoning Province. The temporal variations of open straw burning tended to be dispersed with PCD varying from >0.8 during 2013-2015 to <0.4 during 2017 and PCP changing from 28.2 to 36.0 during autumn-winter seasons of 2013-2015 to 5.4-7.9 during winter-spring seasons of 2016-2017. During the five-year period (2013-2017), the total straw yield reached 628.7 million tons, of which 10.9 million tons were open burned in northeast China. The total amounts emitted from open straw burning were 108.9, 106.9, 552.9, 36.9 and 99.4 thousand tons for PM10, PM25, CO, NOx and NMVOCs, respectively. Among these emissions, corn straw burning contributed 81.7%, 81.6%, 71.4%, 86.8% and 74.9% while rice straw burning contributed 18.2%, 18.4%, 28.5%, 13.2% and 25.0%, respectively. Emissions from open straw burning have significant impacts on pollutants ambient concentrations, especially for PM2.5 in the autumn-winter seasons as indicated by their good correlations (p < 0.05).
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