Respirable particulate matter present in outdoor and indoor environments is a health hazard. The particle concentrations can quickly change, with steep gradients on short temporal and spatial scales, ...and their chemical composition and physical properties vary considerably. Existing networks of aerosol particle measurements consist of limited number of monitoring stations, and mostly aim at assessment of compliance with air quality legislation regulating mass of particles of varying sizes. These networks can now be supplemented using small portable devices with low-cost sensors for assessment of particle mass that may provide higher temporal and spatial resolution if we understand the capabilities and characteristics of the data they provide. This paper overviews typical currently available devices and their characteristics. In addition it is presented original results of measurement and modelling in the aim of one low-cost PM monitor validation.
•Rreal time monitoring of indicative levels of PM in the ambient air with high temporal/spatial resolution.•Summary of standards/guidelines for PM levels in urban areas all over the world.•Summary of available PM low cost sensors and monitors.•Requirements for low-cost PM devices validation.
Systematic literature review and experimental validation proved that low-cost PM monitors are suitable for high time/space measurement that is crucial for personal exposure assessment.
The current compliance networks of automatic air-quality monitoring stations in large urban environments are not sufficient to provide spatial and temporal measurement resolution for realistic ...assessment of personal exposure to pollutants. Small low-cost sensor platforms with greater mobility and expected lower maintenance costs, are increasingly being used as a supplement to compliance monitoring stations. However, low-cost sensor platforms usually provide data with uncertain precision. To improve the precision, these sensor platforms require in-field calibration. Our paper aims to demonstrate that data from each individual sensor system can be corrected using that sensor system's own data to achieve much improved data quality compared to a reference. However, in this procedure, there are practical difficulties such as individual sensor outputs from the multi-sensor system not being sufficiently available due to malfunctions for instance. We explore how this can be dealt with. In our opinion, this is a novel approach, of practical importance both to users and manufacturers. We present a detailed comparative analysis of Linear Regression (univariate), Multivariate Linear Regression and Artificial Neural Networks used with a specific aim of calibrating field-deployed low-cost CO and O3 sensors. For Artificial Neural Network models, the performance of three common training algorithms was compared (Levenberg-Marquardt, Resilient back-propagation and Conjugate Gradient Powell-Beale algorithm). Data for this study were obtained from two campaigns conducted with 25 multi-sensor AQMESH v.3.5 platforms used within the activities of the CITI-SENSE project. The platforms were co-located to reference gas monitors at the Automatic Monitoring Station Stari Grad, in Belgrade, Serbia. This paper demonstrates that Multivariate Linear Regression and Artificial Neural Network calibration models can improve the output signal. This improvement can be measured by changes in the median and interquartile ranges of statistical parameters used for model evaluation. Artificial Neural Networks showed the best results compared to Linear Regression and Multivariate Linear Regression models. The best predictors for CO, in addition to CO low-cost sensor data, were PM2.5 and NO2, while for O3, in addition to O3 low-cost sensor data, the most suitable input predictors were NO and aH. Based on residual error analysis, we have shown that for CO and O3, a certain range of concentrations exists in which calibrated values differ by less than 10% from the reference method results. In addition, it was noted that for all models, CO sensors consistently showed lower variability between platforms compared to O3 sensors.
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•Precision of measured concentrations can be enhanced by using other available sensors.•Calibration predictors for CO were COlc, PM2.5 and NO2, for O3 were O3,lc, NO and aH.•ANN models perform better compared to linear or multilinear regression models.•Within certain ranges of CO and O3 the error of calibrated data is less than 10%.•CO sensors show less variability between the platforms than O3 sensors.
Over the last 10 years, as a possible alternative to the conventional approach to air quality monitoring, real-time monitoring systems that use low-cost sensors and sensor platforms have been ...frequently applied. Generally, the long-term characteristics of low-cost PM sensors and monitoring have not been thoroughly documented except for a few widely used sensors and monitors. This article addresses the laboratory and field validation of three low-cost PM monitors of the same type that use the NOVA SDS011 PM sensor module over a 1-year period. In outdoor environments, we co-located low-cost PM monitors with GRIMM EDM180 monitors at the National Air Quality Monitoring stations. In indoor environments, we co-located them with a Turnkey Osiris PM monitor. Several performance aspects of the PM monitors were examined: operational data coverage, linearity of response, accuracy, precision, and inter-sensor variability. The obtained results show that inter-monitor R values were typically higher than 0.95 regardless of the environment. The tested monitors demonstrate high linearity in comparison with PM
10
and PM
2.5
concentrations measured in outdoor air with reference-equivalent instrumentation with R
2
values ranging from 0.52 up to 0.83. In addition, very good agreement (R
2
values ranging from 0.93 up to 0.97) with the gravimetric PM
10
and PM
2.5
method is obtained in the indoor environment (30 <
RH
< 70%). High RH (over 70%) negatively affected the PM monitors’ response, especially in the case of PM
10
concentrations (high overestimation).
Individual monitoring service at the Department for Radiation and Environmental Protection of Vinca Institute of Nuclear Sciences performs individual whole-body and extremities monitoring of exposed ...workers, using thermoluminescent dosimetry (TLD) method. The dosemeters for eye-lens personal dose equivalent measurements, Hp(3), are not regularly used at the workplaces in Serbia, even though the individual monitoring method is accredited and available at the dosimetry service. Type testing of Hp(3) dosemeters based on LiF: Mg,Ti, placed in modified ring holders was done following the changes in ISO 4037:2019 and IEC 62387:2020. The type testing was done by varying radiation-based influence quantities: photon energies ranging from 33.3 keV up to 1.25 MeV, angle of incidence values of 0°, 45°, 60°, 75°, dose range from 0.05 mSv to 10 Sv. The results show that the passive dosimetry monitoring system satisfies IEC 62387:2020 requirements in the mandatory range of influence quantities, except for the lowest tested energy of 33 keV, when incident radiation angle is ±60° and higher.
•Recent changes in ISO 4037 and IEC 62387 prompted new type testing of TLD system.•Introduction of 20 mSv annual limit brought focus to the eye lens dose monitoring.•TLD system that measures Hp(3) due to photon radiation was tested.•Values of CoV limit the use of the system in the dose range from 0.3 mSv to 1 Sv.•System showed unsatisfactory overresponse for more than 60° incident angle.
National systems of automatic air quality monitoring are based on automatic measuring instruments that are installed in stationary air quality monitoring stations. Substantial financial resources are ...required for the procurement, installation, calibration, and maintenance of such measuring devices. For this reason, existing national and local air quality monitoring networks are not able to provide a high temporal and spatial resolution of measurement results. In the last decade, as a possible alternative to the conventional approach to air quality monitoring, real-time monitoring systems using low-cost sensors and sensor plat-forms have begun to be applied. This paper describes the basic characteristics of a portable air quality monitor PAQMAN 2020 based on low-cost sensors. Part of the results of comparative measurements of this device with the reference instruments is presented in the paper.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The European initiatives for citizens? inclusion in the air quality monitoring process have impacted the participants? knowledge, and attitudes towards air pollution and have led to a higher sense of ...community toward activities and measures against air pollution. In the Republic of Serbia, an experiment with self-made sensor kits "Klimerko ? Air to the Citizens" started in 2018. In this paper, we have presented the level of agreement of the particulate matter (PM) readings from selected Klimerko devices to the PM readings of the reference equivalent PM monitors from the National Air Quality Monitoring Network in the cities of Bor and Belgrade. The Klimerko devices that we tested showed excellent stability and reliability during the comparison period. The conclusion of our investigation is that the properly calibrated Klimerko devices could be applied for indicative measurements of PM mass concentrations in the ambient air.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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