Added Value of Vaisala AQT530 Sensors as a Part of a Sensor Network for Comprehensive Air Quality Monitoring

Poor air quality influences the quality of life in the urban environment. The regulatory observation stations provide the backbone for the city administration to monitor urban air quality. Recently a suite of cost-effective air quality sensors has emerged to provide novel insights into the spatio-temporal variability of aerosol particles and trace gases. Particularly in low concentrations these sensors might suffer from issues related e.g., to high detection limits, concentration drifts and interdependency between the observed trace gases and environmental parameters. In this study we characterize the optical particle detector used in AQT530 (Vaisala Ltd.) air quality sensor in the laboratory. We perform a measurement campaign with a network of AQT530 sensors in Helsinki, Finland in 2020–2021 and present a long-term performance evaluation of five sensors for particulate (PM10, PM2.5) and gaseous (NO2, NO, CO, O3) components during a half-year co-location study with reference instruments at an urban traffic site. Furthermore, short-term (3–5 weeks) co-location tests were performed for 25 sensors to provide sensor-specific correction equations for the fine-tuning of selected pollutants in the sensor network. We showcase the added value of the verified network of 25 sensor units to address the spatial variability of trace gases and aerosol mass concentrations in an urban environment. The analysis assesses road and harbor traffic monitoring, local construction dust monitoring, aerosol concentrations from fireworks, impact of sub-urban small scale wood combustion and detection of long-range transport episodes on a city scale. Our analysis illustrates that the calibrated network of Vaisala AQT530 air quality sensors provide new insights into the spatio-temporal variability of air pollution within the city. This information is beneficial to, for example, optimization of road dust and construction dust emission control as well as provides data to tackle air quality problems arising from traffic exhaust and localized wood combustion emissions in the residential areas.

Download Full-text

Airborne observation during KORUS-AQ show aerosol optical depth are more spatially self-consistent than aerosol intensive properties

10.5194/acp-2021-1012 ◽

2022 ◽

Author(s):

Samuel E. LeBlanc ◽

Michal Segal-Rozenhaimer ◽

Jens Redemann ◽

Connor J. Flynn ◽

Roy R. Johnson ◽

...

Keyword(s):

Air Quality ◽

Aerosol Optical Depth ◽

Optical Depth ◽

Temporal Variability ◽

Spatial Scales ◽

Aerosol Emission ◽

Fine Mode ◽

Predominant Factor ◽

Spatio Temporal ◽

Microphysical Processes

Abstract. Aerosol particles can be emitted, transported, removed, or transformed, leading to aerosol variability at scales impacting the climate (days to years and over hundreds of kilometers) or the air quality (hours to days and from meters to hundreds of kilometers). We present the temporal and spatial scales of changes in AOD (Aerosol Optical Depth), and aerosol size (using Angstrom Exponent; AE, and Fine-Mode-Fraction; FMF) over Korea during the 2016 KORUS-AQ (KORea-US Air Quality) atmospheric experiment. We use measurements and retrievals of aerosol optical properties from airborne instruments for remote sensing (4STAR; Spectrometers for Sky-Scanning Sun Tracking Atmospheric Research) and in situ (LARGE; NASA Langley Aerosol Research Group Experiment) on board the NASA DC-8, geostationary satellite (GOCI; Geostationary Ocean Color Imager; Yonsei aerosol retrieval (YAER) version 2) and reanalysis (MERRA-2; Modern-Era Retrospective Analysis for Research and Applications, version 2). Measurements from 4STAR when flying below 500 m, show an average AOD at 501 nm of 0.43 and an average AE of 1.15 with large standard deviation (0.32 and 0.26 for AOD and AE respectively) likely due to mixing of different aerosol types (fine and coarse mode). The majority of AODs due to fine mode aerosol is observed at altitudes lower than 2 km. Even though there are large variations, for 18 out of the 20 flight days, the column AOD measurements by 4STAR along the NASA DC-8 flight trajectories matches the south-Korean regional average derived from GOCI. We also observed that, contrary to prevalent understanding, AE and FMF are more spatially variable than AOD during KORUS-AQ, even when accounting for potential sampling biases by using Monte Carlo resampling. Averaging between measurements and model for the entire KORUS-AQ period, a reduction in correlation by 15 % is 65.0 km for AOD and shorter at 22.7 km for AE. While there are observational and model differences, the predominant factor influencing spatial-temporal homogeneity is the meteorological period. High spatio-temporal variability occur during the dynamic period (25–31 May), and low spatio-temporal variability occur during blocking Rex pattern (01–07 June). The changes in spatial variability scales between AOD and FMF/AE, while inter-related, indicate that microphysical processes that impact mostly the dominant aerosol size, like aerosol particle formation, growth, and coagulation, vary at shorter scales than the aerosol concentration processes that mostly impact AOD, like aerosol emission, transport, and removal.

Download Full-text

Impact of Settlement Growth on Yenagoa’s Urban Environment

European Journal of Environment and Earth Sciences ◽

10.24018/ejgeo.2021.2.1.107 ◽

2021 ◽

Vol 2 (1) ◽

pp. 24-29

Author(s):

E. E. Imaitor-Uku ◽

O. B. Owei ◽

L. Hart ◽

A. Ayotamuno

Keyword(s):

Land Use ◽

Urban Environment ◽

Sustainable Land Use ◽

Mapping Technique ◽

Citizen Education ◽

Management Framework ◽

Urban Planning And Development ◽

Spatio Temporal ◽

The City ◽

Settlement Growth

This research is a study on the assessment of settlement growth and its impact on the urban environment in Yenagoa Metropolis. Landsat imageries of 1988, 1996, 2004, 2012 and 2020 were acquired from the United Sates Geographical Survey. Supervised image classifications using level 1 classification scheme was adopted to extract LandUse/LandCover. The five Epochs of images were used to extract the built-up areas, water bodies and vegetation areas. The area (ha) of land use for each epoch was determined using clipping images. The spatio-temporal changes were determined as a percentage of LULC per epoch and which was done following standard methods. Mapping technique was used to compare satellite imageries. Findings showed that built up areas was 1,279.81 in 1988, 2,497.87 in 1996, 4,554.73 in 2009, 7,804.30 in 2012 and 10,447.50 in 2020. While the percentage change of built-up are in 1988 was 6.12%, 1996 was 11.94%, 2004 was 21.78%, 2012 was 34.31% and 2020 was 30.09%, respectively. It is therefore recommended here that government should empower urban planning and development agencies, legally and financially to carry out their responsibility to implement existing master plan of the city. Engage in citizen education on how to contribute in managing the environment and sustainable land use management framework in the study area for proper management of the urban environment to enhance sustained settlement growth in the city.

Download Full-text

Solution to Urban Air Pollution – Carbon Free Transport

Baltic Journal of Real Estate Economics and Construction Management ◽

10.1515/bjreecm-2016-0003 ◽

2016 ◽

Vol 4 (1) ◽

pp. 32-47

Author(s):

Jānis Kleperis ◽

Biruta Sloka ◽

Justs Dimants ◽

Ilze Dimanta ◽

Jānis Kleperis

Keyword(s):

Air Pollution ◽

Air Quality ◽

Urban Environment ◽

Fossil Fuel ◽

Fine Particles ◽

Combustion Engine ◽

City Council ◽

Dust Particles ◽

City Centre ◽

The City

Abstract The analysis of the results of long-term air quality monitoring in Riga is presented, which shows that in city centre throughout the measurement time (2004-2014) according to the guidelines defined by the European Union directives and Latvian laws the limits of small particles PM10 and nitrogen dioxide (NO2) are exceeded. From the nature of appearance of pollution and from the research of morphology and composition of fine dust particles it was concluded that in the city centre where the monitoring was performed the main air pollutants are caused by internal combustion engine vehicles. The measures to reduce air pollution performed by two Action Programs (2004-2009; 2011-2015) of the City Council showed that there were only two possible ways to improve air quality in urban environment ‒ to decrease the number of traffic units and/or to decrease exhaust emissions from vehicles. From the analysis of energy consumption and resources used for it the conclusion was drawn that Latvia is dependent on fossil fuel import, especially in traffic sector (99 %). A new trend has been observed in Latvia ‒ the type of cars is changing: the number of gasoline cars rapidly decreases and number of diesel cars is growing. Both fuels in exhaust gases of second-hand cars are giving high emissions of fine particles (soot) and nitrogen oxides as compared with new cars; 72 % of cars on the roads of Latvia are more than 13 years old. The switch to bio-diesel can improve Latvian statistics according to CO2 reduction target for 2020 but not the concentration of PM10 and NO2 on streets with dense traffic. Therefore, to improve air quality in urban environment and simultaneously reduce the dependence of Latvia from fossil fuel import, a scenario is proposed for the changeover to zero-carbon technologies in transport and energy production. Hydrogen is analyzed from the point of view of availability of resources and commercialized technologies. The research of the public opinion was done because there is little awareness in society about hydrogen as energy carrier and simultaneously as fuel.

Download Full-text

Cold-Air Pool Processes in the Inn Valley During Föhn: A Comparison of Four Cases During the PIANO Campaign

Boundary-Layer Meteorology ◽

10.1007/s10546-021-00663-9 ◽

2021 ◽

Author(s):

Maren Haid ◽

Alexander Gohm ◽

Lukas Umek ◽

Helen C. Ward ◽

Mathias W. Rotach

Keyword(s):

Temporal Variability ◽

Flow Instability ◽

Heat Budget ◽

Comprehensive Analysis ◽

City Centre ◽

The West ◽

Cold Air ◽

Spatio Temporal ◽

Shear Flow Instability ◽

The City

AbstractWe present a comprehensive analysis of four south föhn events observed during the Penetration and Interruption of Alpine Foehn (PIANO) field campaign in the Inn Valley, Austria, in the vicinity of Innsbruck. The goal is to detect and quantify processes of cold-air pool (CAP) erosion by föhn as well as processes of föhn breakdown. Despite differences in föhn breakthrough and strength, the four cases exhibit similarities in CAP evolution: initially, the CAP experienced strongest warming in the centre of Innsbruck, where the föhn jet from the Wipp Valley interacted with the CAP in the Inn Valley. The resulting shear-flow instability at the föhn–CAP interface caused turbulent CAP erosion and, together with vertical warm-air advection, led to CAP depression over the city centre. This depression drove pre-föhn westerlies near the surface that caused cold-air advection inside the CAP west of the city centre and warm-air advection in the east. Ultimately, the latter contributed to stronger CAP erosion in the east than in the west. This stronger heating also explains the preferential initial föhn breakthrough at the valley floor east of Innsbruck. In two of the cases, subsequent westward propagation of the föhn–CAP boundary across the city accompanied by northerly (deflected) föhn winds led to a complete föhn breakthrough. Föhn breakdown occurred either by a backflow of the CAP remnant or by a cold-frontal passage. This study emphasizes the importance of both turbulence and advection in the CAP heat budget and reveal their large spatio–temporal variability.

Download Full-text

Intra–Community Scale Variability of Air Quality in the Center of a Megacity in South Korea: A High-Density Cost-Effective Sensor Network

Applied Sciences ◽

10.3390/app11199105 ◽

2021 ◽

Vol 11 (19) ◽

pp. 9105

Author(s):

Yongmi Park ◽

Ho-Seon Park ◽

Subin Han ◽

Kyucheol Hwang ◽

Seunghyun Lee ◽

...

Keyword(s):

Air Quality ◽

South Korea ◽

Sensor Network ◽

Temporal Variability ◽

Urban Areas ◽

Pearson Correlation ◽

Urban Canopy ◽

Air Pollutant ◽

Sensor Nodes ◽

Spatial And Temporal Variability

To investigate the spatial and temporal variability of air quality (CO, NO2, O3, and PM2.5) with a high spatial resolution in various adjacent micro-environments, 30 sets of sensor-nodes were deployed within an 800 × 800 m monitoring domain in the center of the largest megacity (Seoul) in South Korea. The sensor network was operated in summer and winter. The daily variation in air pollutant concentrations revealed a similar trend, with discernible concentration differences among monitoring sub-sites and a government-operated air quality monitoring station. These differences in pollutant levels (except PM2.5) among the sub-sites were pronounced in the daytime with high volumes of traffic. The coefficient of divergence and Pearson correlation coefficient showed that spatial and temporal variability was more significant in summer than winter. Ozone displayed the greatest spatial variability, with little temporal variability among the sub-sites and a negative correlation with NO2, implying that ozone concentrations were primarily determined by vehicular NOX emissions due to NO titration effects under the urban canopy. The PM2.5 concentration displayed homogeneous spatial and temporal distributions over the entire monitoring period, implying that PM2.5 monitoring with at least a 1 × 1 km resolution is sufficient to examine the spatial and temporal heterogeneity in urban areas.

Download Full-text

Mid-IR spectrometer for mobile, real-time urban NO<sub>2</sub> measurements

Atmospheric Measurement Techniques ◽

10.5194/amt-11-2669-2018 ◽

2018 ◽

Vol 11 (5) ◽

pp. 2669-2681 ◽

Cited By ~ 4

Author(s):

P. Morten Hundt ◽

Michael Müller ◽

Markus Mangold ◽

Béla Tuzson ◽

Philipp Scheidegger ◽

...

Keyword(s):

Air Quality ◽

Urban Environment ◽

Real Time ◽

Infrared Laser ◽

Detailed Knowledge ◽

Data Set ◽

Laser Absorption ◽

Spatial Coverage ◽

Spatio Temporal ◽

The Impact

Abstract. Detailed knowledge about the urban NO2 concentration field is a key element for obtaining accurate pollution maps and individual exposure estimates. These are required for improving the understanding of the impact of ambient NO2 on human health and for related air quality measures. However, city-scale NO2 concentration maps with high spatio-temporal resolution are still lacking, mainly due to the difficulty of accurate measurement of NO2 at the required sub-ppb level precision. We contribute to close this gap through the development of a compact instrument based on mid-infrared laser absorption spectroscopy. Leveraging recent advances in infrared laser and detection technology and a novel circular absorption cell, we demonstrate the feasibility and robustness of this technique for demanding mobile applications. A fully autonomous quantum cascade laser absorption spectrometer (QCLAS) has been successfully deployed on a tram, performing long-term and real-time concentration measurements of NO2 in the city of Zurich (Switzerland). For ambient NO2 concentrations, the instrument demonstrated a precision of 0.23 ppb at one second time resolution and of 0.03 ppb after 200 s averaging. Whilst the combined uncertainty estimated for the retrieved spectroscopic values was less than 5 %, laboratory intercomparison measurements with standard CLD instruments revealed a systematic NO2 wall loss of about 10 % within the laser spectrometer. For the field campaign, the QCLAS has been referenced to a CLD using urban atmospheric air, despite the potential cross sensitivity of CLD to other nitrogen containing compounds. However, this approach allowed a direct comparison and continuous validation of the spectroscopic data to measurements at regulatory air quality monitoring (AQM) stations along the tram-line. The analysis of the recorded high-resolution time series allowed us to gain more detailed insights into the spatio-temporal concentration distribution of NO2 in an urban environment. Furthermore, our results demonstrate that for reliable city-scale concentration maps a larger data set and better spatial coverage is needed, e.g., by deploying more mobile and stationary instruments to account for mainly two shortcomings of the current approach: (i) limited residence time close to sources with large short-term NO2 variations, and (ii) insufficient representativeness of the tram tracks for the complex urban environment.

Download Full-text

Spatial and temporal variability of air quality in Shanghai in 2015

E3S Web of Conferences ◽

10.1051/e3sconf/202019405063 ◽

2020 ◽

Vol 194 ◽

pp. 05063

Author(s):

Li Liu ◽

Lihuan He ◽

Yu Bai ◽

Mi Zhou ◽

Fengying Zhang ◽

...

Keyword(s):

Spatial Distribution ◽

Air Quality ◽

Urban Area ◽

Spatial Patterns ◽

Temporal Variability ◽

Air Pollutants ◽

Quality Index ◽

Air Quality Index ◽

Spatial And Temporal Variability ◽

The City

In order to understand the temporal-spatial patterns of air pollutants in Shanghai, the concentrations of six air pollutants (SO2, NO2, PM10, PM2.5, CO, O3) and air quality index (AQI) were analyzed. The results showed that, the percentage of excellent/good-AQI days was 70.7% during the whole year of 2015, and PM2.5, O3 and NO2 were the main air pollutants in Shanghai. Besides, the air quality in winter was most serious, followed by that in spring and autumn, and the air quality in summer was the best. From the perspective of spatial distribution, monitoring stations in YangpuSipiao and Putuo which were located in the urban area were affected by traditional industries and the air quality were poor, while those in Chuansha and Zhangjiang of Pudong which were located on the edge of the city showed relatively good air quality.

Download Full-text

The influence of residential wood combustion on the concentrations of PM<sub>2.5</sub> in four Nordic cities

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-4333-2020 ◽

2020 ◽

Vol 20 (7) ◽

pp. 4333-4365 ◽

Cited By ~ 6

Author(s):

Jaakko Kukkonen ◽

Susana López-Aparicio ◽

David Segersson ◽

Camilla Geels ◽

Leena Kangas ◽

...

Keyword(s):

Air Quality ◽

Atmospheric Dispersion ◽

Ambient Air ◽

City Centre ◽

Wood Combustion ◽

Annual Average ◽

Suburban Areas ◽

Extensive Evaluation ◽

Urban Concentration ◽

The City

Abstract. Residential wood combustion (RWC) is an important contributor to air quality in numerous regions worldwide. This study is the first extensive evaluation of the influence of RWC on ambient air quality in several Nordic cities. We have analysed the emissions and concentrations of PM2.5 in cities within four Nordic countries: in the metropolitan areas of Copenhagen, Oslo, and Helsinki and in the city of Umeå. We have evaluated the emissions for the relevant urban source categories and modelled atmospheric dispersion on regional and urban scales. The emission inventories for RWC were based on local surveys, the amount of wood combusted, combustion technologies and other relevant factors. The accuracy of the predicted concentrations was evaluated based on urban concentration measurements. The predicted annual average concentrations ranged spatially from 4 to 7 µg m−3 (2011), from 6 to 10 µg m−3 (2013), from 4 to more than 13 µg m−3 (2013) and from 9 to more than 13 µg m−3 (2014), in Umeå, Helsinki, Oslo and Copenhagen, respectively. The higher concentrations in Copenhagen were mainly caused by the relatively high regionally and continentally transported background contributions. The annual average fractions of PM2.5 concentrations attributed to RWC within the considered urban regions ranged spatially from 0 % to 15 %, from 0 % to 20 %, from 8 % to 22 % and from 0 % to 60 % in Helsinki, Copenhagen, Umeå and Oslo, respectively. In particular, the contributions of RWC in central Oslo were larger than 40 % as annual averages. In Oslo, wood combustion was used mainly for the heating of larger blocks of flats. In contrast, in Helsinki, RWC was solely used in smaller detached houses. In Copenhagen and Helsinki, the highest fractions occurred outside the city centre in the suburban areas. In Umeå, the highest fractions occurred both in the city centre and its surroundings.

Download Full-text

The MetVed model: development and evaluation of emissions from residential wood combustion at high spatio-temporal resolution in Norway

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-10217-2019 ◽

2019 ◽

Vol 19 (15) ◽

pp. 10217-10237 ◽

Cited By ~ 5

Author(s):

Henrik Grythe ◽

Susana Lopez-Aparicio ◽

Matthias Vogt ◽

Dam Vo Thanh ◽

Claudia Hak ◽

...

Keyword(s):

Air Quality ◽

Black Carbon ◽

Temporal Resolution ◽

National Level ◽

Temporal Distribution ◽

Emission Factors ◽

Wood Combustion ◽

Spatio Temporal ◽

Urban Emissions ◽

Wood Consumption

Abstract. We present here emissions estimated from a newly developed emission model for residential wood combustion (RWC) at high spatial and temporal resolution, which we name the MetVed model. The model estimates hourly emissions resolved on a 250 m grid resolution for several compounds, including particulate matter (PM), black carbon (BC) and polycyclic aromatic hydrocarbons (PAHs) in Norway for a 12-year period. The model uses novel input data and calculation methods that combine databases built with an unprecedented high level of detail and near-national coverage. The model establishes wood burning potential at the grid based on the dependencies between variables that influence emissions: i.e. outdoor temperature, number of and type and size of dwellings, type of available heating technologies, distribution of wood-based heating installations and their associated emission factors. RWC activity with a 1 h temporal profile was produced by combining heating degree day and hourly and weekday activity profiles reported by wood consumers in official statistics. This approach results in an improved characterisation of the spatio-temporal distribution of wood use, and subsequently of emissions, required for urban air quality assessments. Whereas most variables are calculated based on bottom-up approaches on a 250 m spatial grid, the MetVed model is set up to use official wood consumption at the county level and then distributes consumption to individual grids proportional to the physical traits of the residences within it. MetVed combines consumption with official emission factors that makes the emissions also upward scalable from the 250 m grid to the national level. The MetVed spatial distribution obtained was compared at the urban scale to other existing emissions at the same scale. The annual urban emissions, developed according to different spatial proxies, were found to have differences up to an order of magnitude. The MetVed total annual PM2.5 emissions in the urban domains compare well to emissions adjusted based on concentration measurements. In addition, hourly PM2.5 concentrations estimated by an Eulerian dispersion model using MetVed emissions were compared to measurements at air quality stations. Both hourly daily profiles and the seasonality of PM2.5 show a slight overestimation of PM2.5 levels. However, a comparison with black carbon from biomass burning and benzo(a)pyrene measurements indicates higher emissions during winter than that obtained by MetVed. The accuracy of urban emissions from RWC relies on the accuracy of the wood consumption (activity data), emission factors and the spatio-temporal distribution. While there are still knowledge gaps regarding emissions, MetVed represents a vast improvement in the spatial and temporal distribution of RWC.

Download Full-text

The MetVed model: Development and evaluation of emissions from residential wood combustion at high spatio-temporal resolution in Norway

10.5194/acp-2019-95 ◽

2019 ◽

Author(s):

Henrik Grythe ◽

Susana Lopez-Aparicio ◽

Matthias Vogt ◽

Dam Vo Thanh ◽

Claudia Hak ◽

...

Keyword(s):

Air Quality ◽

Black Carbon ◽

Temporal Resolution ◽

National Level ◽

Temporal Distribution ◽

Emission Factors ◽

Wood Combustion ◽

Spatio Temporal ◽

Urban Emissions ◽

Wood Consumption

Abstract. We present here emissions estimated from a newly developed emission model for residential wood combustion (RWC) at high spatial and temporal resolution, which we title the MetVed model. The model estimates hourly emissions resolved on a 250 m grid resolution for several compounds, including particulate matter (PM), black carbon (BC) and polycyclic aromatic hydrocarbons (PAH) in Norway for a 12 year period. The model uses novel input data and calculation methods that combine databases built with an unprecedented high level of detail and near national coverage. The model establishes wood burning potential at the grid based on the dependencies between variables that influence emissions; i.e., outdoor temperature, number of and type and size of dwellings, type of available heating technologies, distribution of wood-based heating installations and their associated emission factors. RWC activity with a 1 hr temporal profile was produced by combining heating degree day, and hourly and weekday activity profiles reported by wood consumer in official statistics. This approach results in an improved characterisation of the spatio-temporal distribution of wood use and subsequently of emissions, required for urban air quality assessments. Whereas most variables are calculated based on bottom up approaches on a 250 m spatial grid, the MetVed model is set up to use official wood consumption at county level, and then distributes consumption to individual grids proportional to the physical traits of the residences within it. MetVed combines consumption with official emission factors that makes the emissions also upward scalable from the 250 m grid to national level. The MetVed spatial distribution obtained was compared at urban scale to other existing emissions at the same scale. The annual urban emissions, developed according to different spatial proxies, were found to have differences up to order of magnitude. The MetVed total annual PM2.5 emissions in the urban domains compare well to emissions adjusted based on concentration measurements. In addition, hourly PM2.5 concentrations estimated by an Eulerian dispersion model using MetVed emissions was compared to measurements at air quality stations. Both hourly daily profiles and the seasonality of PM2.5 show a slight overestimation of PM2.5 levels. However, a comparison with black carbon from biomass burning and benzo(a)pyrene measurements indicates higher emissions during winter than that obtained by MetVed. The accuracy of urban emissions from RWC relies on the accuracy of the wood consumption (activity data), emission factors and the spatio-temporal distribution. While there are still knowledge gaps regarding emissions, MetVed represents a vast improvement in the spatial and temporal distribution of RWC.

Download Full-text