Ambient air particle mass concentrations in the urban area of the capital city of Yaoundé (Cameroon, Central Africa): monthly and seasonal behaviour

Abstract. A fast-growing area of research is the development of low-cost sensors for measuring air pollutants. The affordability and size of low-cost particle sensors makes them an attractive option for use in experiments requiring a number of instruments such as high-density spatial mapping. However, for these low-cost sensors to be useful for these types of studies their accuracy and precision need to be quantified. We evaluated the Alphasense OPC-N2, a promising low-cost miniature optical particle counter, for monitoring ambient airborne particles at typical urban background sites in the UK. The precision of the OPC-N2 was assessed by co-locating 14 instruments at a site to investigate the variation in measured concentrations. Comparison to two different reference optical particle counters as well as a TEOM-FDMS enabled the accuracy of the OPC-N2 to be evaluated. Comparison of the OPC-N2 to the reference optical instruments shows some limitations for measuring mass concentrations of PM1, PM2.5 and PM10. The OPC-N2 demonstrated a significant positive artefact in measured particle mass during times of high ambient RH (> 85 %) and a calibration factor was developed based upon κ-Köhler theory, using average bulk particle aerosol hygroscopicity. Application of this RH correction factor resulted in the OPC-N2 measurements being within 33 % of the TEOM-FDMS, comparable to the agreement between a reference optical particle counter and the TEOM-FDMS (20 %). Inter-unit precision for the 14 OPC-N2 sensors of 22 ± 13 % for PM10 mass concentrations was observed. Overall, the OPC-N2 was found to accurately measure ambient airborne particle mass concentration provided they are (i) correctly calibrated and (ii) corrected for ambient RH. The level of precision demonstrated between multiple OPC-N2s suggests that they would be suitable devices for applications where the spatial variability in particle concentration was to be determined.

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Physical and chemical characterization of the particulate matter suspended in aerosols from the urban area of Belgrade

Journal of the Serbian Chemical Society ◽

10.2298/jsc0911319j ◽

2009 ◽

Vol 74 (11) ◽

pp. 1319-1333 ◽

Cited By ~ 7

Author(s):

Jasminka Joksic ◽

Milena Jovasevic-Stojanovic ◽

Alena Bartonova ◽

Mirjana Radenkovic ◽

Karl-Espen Yttri ◽

...

Keyword(s):

Trace Elements ◽

Particulate Matter ◽

Urban Area ◽

Chemical Characterization ◽

Ambient Air ◽

Pollution Sources ◽

Limit Values ◽

Secondary Ions ◽

Physical And Chemical ◽

Mass Concentrations

Within this study, attempts were made to characterize the coarse and fine particulate aerosol fractions in urban area of Belgrade and define the inorganic chemical composition of the aerosol fractions. For this purpose, daily deposits of PM10, PM2.5 and PM1 aerosol fractions were collected during spring and autumn sampling periods in 2007 and analyzed for the PM mass concentrations, trace elements and secondary ions. The results obtained in the two campaigns showed average daily mass concentrations of 37 and 44 ?g/m3 for PM10, 22 and 23 ?g/m3 for PM2.5 and 15 and 17 ?g/m3 for the finest particulate matter fraction PM1 with the maximums exceeding the limit values set by the EU air quality regulations. A correlation with the gas-phase ambient air pollutants SO2, NO2 and O3 was found and is discussed. The concentrations of trace elements (Mg, Al, K, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Mo, Cd, Sb, Ba, Tl, Pb and Th) and secondary ions (NO3 -, SO4 2-, NH4 +, K+, Ca2+ and Na+) determined in the PM10, PM2.5 and PM1 aerosol fractions showed levels and distributions indicating soil and traffic-related sources as the main pollution sources. This study was conducted as the first step of PM assessment in order to point out main air pollution sources and suggest a remedy strategy specific for this region.

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Thirty-years Assessment of Size-fractionated Particle Mass Concentrations in a Polluted Urban Area and Its Implications for the Regulatory Framework

Journal of Environmental Accounting and Management ◽

10.5890/jeam.2013.08.004 ◽

2013 ◽

Vol 1 (3) ◽

pp. 259-267 ◽

Cited By ~ 2

Author(s):

Marco Casazza ◽

Giorgio Gilli ◽

Angelo Piano ◽

Silvia Alessio

Keyword(s):

Urban Area ◽

Regulatory Framework ◽

Particle Mass ◽

Mass Concentrations

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Chemical characterization of the inorganic fraction of aerosols and mechanisms of the neutralization of atmospheric acidity in Athens, Greece

Atmospheric Chemistry and Physics ◽

10.5194/acp-7-3015-2007 ◽

2007 ◽

Vol 7 (11) ◽

pp. 3015-3033 ◽

Cited By ~ 28

Author(s):

E. T. Karageorgos ◽

S. Rapsomanikis

Keyword(s):

Mass Concentration ◽

Fine Fraction ◽

Ambient Air ◽

Coarse Fraction ◽

Particle Mass ◽

Coarse Particle ◽

Breathing Zone ◽

Neutralizing Agent ◽

Pm10 Mass ◽

Mass Concentrations

Abstract. The PM10 mass concentration levels and inorganic chemical composition were determined on 12-h resolution sampling during August 2003 and March 2004, in the centre of Athens, Greece. The August 2003 campaign mean PM10 mass concentration, obtained by Beta Attenuation at 5 m above ground in Athinas Street, was 56 μg m−3 while the corresponding value for March 2004 was 92 μg m−3. In both campaigns the E.U. imposed daily limit of 50 μg m−3 was exceeded on several days. During the March campaign, in Athinas Street, additionally obtained DSFU-PM10 (PM10-2.5+PM2.5) gravimetric mass concentrations (mean: 121 μg m−3) in the "breathing zone", at 1.5 m above ground were significantly higher compared to the respective mean PM10 mass concentrations obtained by the same method at 25 m above ground, in a second site (AEDA; mean: 86 μg m−3) also in the centre of the city. The above findings suggest that, for a realistic estimation of the exposure of citizens to particulate matter, PM10 sampling in the "breathing zone" (1.5–3 m above ground) is necessary. Such data are presented for the first time for the centre of Athens. In both campaigns, calcium was found to be the predominant component of the coarse fraction while crust-related aluminosilicates and iron were the other major components. The above elements constitute the most important components of the fine fraction, together with the predominant sulphur. All toxic metals were found in concentrations below the established air quality limits, and most of them in lower concentrations compared to older studies. Lead in particular, appeared mostly in the fine fraction and in very low concentrations compared to studies dating more than a decade back. The predominant ions of the coarse fraction have been found to be Ca2+, NO3−, Na+ and Cl−, while SO42−, Ca2+ and NH4+ were the major ionic components of the fine fraction. In the fine particles, a low molar ratio of NH4+/SO42− indicated an ammonium-poor ambient air, and together with inter-ionic correlations suggested that atmospheric ammonia is the major neutralizing agent of sulfate, while being insufficient to neutralize it to full extend. The formation of NH4NO3 is therefore not favored and additional contribution to the neutralization of acidity has been shown to be provided by Ca2+ and Mg2+. In the coarse particle fraction, the predominantly abundant Ca2+ has been found to correlate well with NO3− and SO42−, indicating its role as important neutralizing agent in this particle size range. The proximity of the location under study to the sea explains the important concentrations of salts with marine origin like NaCl and MgCl2 that were found in the coarse fraction, while chloride depletion in the gaseous phase was found to be limited to the fine particulate fraction. Total analyzed inorganic mass (elemental+ionic) was found to be ranging between approximately 25–33% of the total coarse particle mass and 35–42% of the total fine particle mass.

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Impact of COVID-19 induced lockdown and unlock down phases on the ambient air quality of Delhi, capital city of India

Urban Climate ◽

10.1016/j.uclim.2021.100945 ◽

2021 ◽

pp. 100945

Author(s):

Mayank Pandey ◽

M.P. George ◽

R.K. Gupta ◽

Deepak Gusain ◽

Atul Dwivedi

Keyword(s):

Air Quality ◽

Ambient Air ◽

Capital City ◽

Ambient Air Quality

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Pollution Characteristics of Atmospheric Carbonyls in Urban Linfen in Winter

Atmosphere ◽

10.3390/atmos11070685 ◽

2020 ◽

Vol 11 (7) ◽

pp. 685

Author(s):

Fanxiu Li ◽

Hengyuan Wang ◽

Xuezhong Wang ◽

Zhigang Xue ◽

Liqin Duan ◽

...

Keyword(s):

Urban Area ◽

Atmospheric Chemistry ◽

Mass Concentration ◽

High Performance ◽

Exhaust Emissions ◽

Photochemical Reactions ◽

Vehicle Exhaust ◽

Pollution Characteristics ◽

The North ◽

Mass Concentrations

Atmospheric carbonyls (aldehyde and ketone compounds) can be precursors for ozone and PM2.5, and they play an essential role in atmospheric chemistry. Linfen is a basin between mountains on the east and west, and there are many coking plants on the north and south sides of its urban area. The special topography and unfortunate industrial layout have frequently contributed to serious air pollution in Linfen. In order to investigate the pollution characteristics of atmospheric carbonyls in winter in urban Linfen, the carbonyl compounds were collected from the Municipal Committee site (MC) and the Yaowangtai site (YWT) from 16 to 25 January 2019, and their concentrations were analyzed by a high performance liquid chromatography-ultraviolet detector (HPLC-UV). The results show that formaldehyde, acetaldehyde, and acetone were the most abundant compounds, accounting for more than 70% of the total mass concentration of carbonyls in urban Linfen. Levels of these three carbonyls increased during the morning and evening traffic rush hours. The mass concentration of formaldehyde at both sites reached peak values at around noon (10:00–14:00). In addition, the mass concentrations of formaldehyde, acetaldehyde, and acetone were positively correlated with CO mass concentrations, whereas only formaldehyde and acetaldehyde were positively correlated with temperature. Therefore, atmospheric formaldehyde in urban Linfen’s winter mainly came from vehicle exhaust emissions and the secondary generation of photochemical reactions. Most of the acetaldehyde came from vehicle exhaust emissions, and photochemical reactions also partially contributed to it. For acetone, vehicle exhaust emissions were the main source. In addition, coking industry emissions from Northern Linfen′s Hongtong County may also have contributed to the atmospheric carbonyls in the urban area of Linfen. For the first time, this study found that formaldehyde showed different behavior to acetaldehyde and acetone; that is, the nighttime decrease in formaldehyde mass concentration was greater than that of acetaldehyde and acetone.

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Effect of aerosol composition on the performance of low-cost optical particle counter correction factors

10.5194/amt-2019-370 ◽

2019 ◽

Author(s):

Leigh R. Crilley ◽

Ajit Singh ◽

Louisa J. Kramer ◽

Marvin D. Shaw ◽

Mohammed S. Alam ◽

...

Keyword(s):

Correction Factor ◽

Low Cost ◽

Particle Mass ◽

Ambient Atmosphere ◽

Correction Factors ◽

Aerosol Composition ◽

Kohler Theory ◽

Suitable Reference ◽

Aerosol Hygroscopicity ◽

Mass Concentrations

Abstract. There is considerable interest in using low-cost optical particle counters (OPC) to supplement existing routine air quality networks that monitor particle mass concentrations. In order to do this, low-cost OPC data needs to be cross-comparable with particle mass reference instrumentation, and as yet, there is no widely agreed methodology. Aerosol hygroscopicity is known to be a key parameter to consider when correcting particle mass concentrations derived from a low-cost OPC, particularly at high ambient Relative Humidity (RH). Correction factors have been developed that apply κ-Köhler theory to correct for the influence of water uptake by hygroscopic aerosols. We have used datasets of co-located reference particle measurements and a low-cost OPC (OPC-N2, Alphasense), collected in four cities in three continents, to explore the performance of this correction factor. We report evidence that the elevated particle mass concentrations, reported by the low-cost OPC relative to reference instrumentation, is due to bulk aerosol hygroscopicity under different RH conditions, which is determined by aerosol composition and in particular the levels of hygroscopic aerosols (sulphate and nitrate). We exploit measurements made in volcanic plumes in Nicaragua, that are predominantly composed of sulphate aerosol, as a natural experiment to demonstrate this behaviour in the ambient atmosphere, with the observed humidogram closely resembling the calculated pure sulphuric acid humidogram. The results indicate that the particle mass concentrations derived from low-cost OPCs during periods of high RH (> 60 %) need to be corrected for aerosol hygroscopic growth. We employed a correction factor based on κ-Köhler theory and observed corrected OPC-N2 PM2.5 mass concentrations to be within 33 % of reference measurements at all sites. The results indicated that an in situ derived κ (using suitable reference instrumentation) would lead to the most accurate correction relative to co-located reference instruments. Applying literature κ in the correction factor also resulted in improved performance of OPC-N2, to be within 50 % of reference. Therefore, for areas where suitable reference instrumentation for developing a local correction factor is lacking, using a literature κ value can result in a reasonable correction. For locations with low levels of hygroscopic aerosols and RH, a simple calibration against gravimetric measurements (using suitable reference instrumentation) would likely be sufficient. Whilst this study generated correction factors specific for the Alphasense OPC-N2 sensor, the calibration methodology developed is likely amenable to other low cost PM sensors.

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URBAN GROWTH AND WATER QUALITY IN THIMPHU, BHUTAN

Journal of Urban and Environmental Engineering ◽

10.4090/juee.2013.v7n1.082095 ◽

2013 ◽

pp. 82-95 ◽

Cited By ~ 6

Author(s):

Nandu Giri ◽

O. P. Singh

Keyword(s):

Water Quality ◽

Urban Area ◽

Water Samples ◽

Urban Areas ◽

Forest Cover ◽

Rapid Development ◽

Oxygen Demand ◽

Capital City ◽

Quality Data ◽

Water Quality Data

Detailed study was undertaken in 2008 and 2009 on assessment of water quality of River Wang Chhu which flows through Thimphu urban area, the capital city of Bhutan. The water samples were examined at upstream of urban area, within the urban area and its downstream. The water samples were analyzed by studying the physico-chemical, biological and benthic macro-invertebrates. The water quality data obtained during present study are discussed in relation to land use/land cover changes(LULC) and various ongoing human activities at upstream, within the each activity areas and it’s downstream. Analyses of satellite imagery of 1990 and 2008 using GIS revealed that over a period of eighteen years the forest, scrub and agricultural areas have decreased whereas urban area and road network have increased considerably. The forest cover, agriculture area and scrub decreased from 43.3% to 42.57%, 6.88% to 5.33% and 42.55% to 29.42%, respectively. The LULC changes effect water quality in many ways. The water temperature, pH, conductivity, total dissolved solids, turbidity, nitrate, phosphate, chloride, total coliform, and biological oxygen demand were lower at upstream and higher in urban area. On the other hand dissolved oxygen was found higher at upstream and lower in urban area. The pollution sensitive benthic macro-invertebrates population were dominant at upstream sampling sites whereas pollution tolerant benthic macro-invertebrates were found abundant in urban area and its immediate downstream. The rapid development of urban infrastructure in Thimphu city may be posing serious threats to water regime in terms of its quality. Though the deterioration of water quality is restricted to a few localized areas, the trend is serious and needs proper attention of policy planners and decision makers. Proper treatment of effluents from urban areas is urgently needed to reduce water pollution in such affected areas to check further deterioration of water quality. This present study which is based on upstream, within urban area and downstream of Thimphu city can be considered as an eye opener.

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Sources and mixing state of size-resolved elemental carbon particles in a European megacity: Paris

Atmospheric Chemistry and Physics ◽

10.5194/acp-12-1681-2012 ◽

2012 ◽

Vol 12 (4) ◽

pp. 1681-1700 ◽

Cited By ~ 111

Author(s):

R. M. Healy ◽

J. Sciare ◽

L. Poulain ◽

K. Kamili ◽

M. Merkel ◽

...

Keyword(s):

Mass Spectrometer ◽

Biomass Burning ◽

Single Particle ◽

Mass Concentration ◽

Elemental Carbon ◽

Fossil Fuel ◽

Time Of Flight ◽

Particle Mass ◽

Mass Size ◽

Mass Concentrations

Abstract. An Aerosol Time-Of-Flight Mass Spectrometer (ATOFMS) was deployed to investigate the size-resolved chemical composition of single particles at an urban background site in Paris, France, as part of the MEGAPOLI winter campaign in January/February 2010. ATOFMS particle counts were scaled to match coincident Twin Differential Mobility Particle Sizer (TDMPS) data in order to generate hourly size-resolved mass concentrations for the single particle classes observed. The total scaled ATOFMS particle mass concentration in the size range 150–1067 nm was found to agree very well with the sum of concurrent High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) and Multi-Angle Absorption Photometer (MAAP) mass concentration measurements of organic carbon (OC), inorganic ions and black carbon (BC) (R2 = 0.91). Clustering analysis of the ATOFMS single particle mass spectra allowed the separation of elemental carbon (EC) particles into four classes: (i) EC attributed to biomass burning (ECbiomass), (ii) EC attributed to traffic (ECtraffic), (iii) EC internally mixed with OC and ammonium sulfate (ECOCSOx), and (iv) EC internally mixed with OC and ammonium nitrate (ECOCNOx). Average hourly mass concentrations for EC-containing particles detected by the ATOFMS were found to agree reasonably well with semi-continuous quantitative thermal/optical EC and optical BC measurements (r2 = 0.61 and 0.65–0.68 respectively, n = 552). The EC particle mass assigned to fossil fuel and biomass burning sources also agreed reasonably well with BC mass fractions assigned to the same sources using seven-wavelength aethalometer data (r2 = 0.60 and 0.48, respectively, n = 568). Agreement between the ATOFMS and other instrumentation improved noticeably when a period influenced by significantly aged, internally mixed EC particles was removed from the intercomparison. 88% and 12% of EC particle mass was apportioned to fossil fuel and biomass burning respectively using the ATOFMS data compared with 85% and 15% respectively for BC estimated from the aethalometer model. On average, the mass size distribution for EC particles is bimodal; the smaller mode is attributed to locally emitted, mostly externally mixed EC particles, while the larger mode is dominated by aged, internally mixed ECOCNOx particles associated with continental transport events. Periods of continental influence were identified using the Lagrangian Particle Dispersion Model (LPDM) "FLEXPART". A consistent minimum between the two EC mass size modes was observed at approximately 400 nm for the measurement period. EC particles below this size are attributed to local emissions using chemical mixing state information and contribute 79% of the scaled ATOFMS EC particle mass, while particles above this size are attributed to continental transport events and contribute 21% of the EC particle mass. These results clearly demonstrate the potential benefit of monitoring size-resolved mass concentrations for the separation of local and continental EC emissions. Knowledge of the relative input of these emissions is essential for assessing the effectiveness of local abatement strategies.

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