Evaluation of Micro-Sensors to Monitor Ozone in Ambient Air

Micro-sensors are very small sensors with physical dimensions in the sub-micrometer to millimetre range that are used to monitor ozone (O3) in ambient air. They are either based on the variation of the resistance of a semi-conductor or on miniaturized electrochemical cells able to deliver a current varying with the level of the pollutant of interest. In the last years, some technological progress took place and a few commercial sensors are now available in the market. In fact, micro-sensors represent a promising technology in several fields like: monitoring of O3 in ambient air to survey of the limit/target values of the Air Quality Directive, rapid mapping of air pollution over small area, validation of dispersion models, evaluation of exposure of population, emissions monitoring and forest monitoring. However, due to reliability problems there is a hesitancy to apply these sensors for air pollution monitoring. The suitability of these sensors is evaluated in this report. In this study, the response time of micro-sensors is investigated. Moreover, warming time after a cold start, linearity, drift over time and the effect of NO2 interference, wind velocity, temperature and humidity on the response of sensors are presented. The comparison of the response of these samplers versus UV photometry is investigated both under controlled conditions using exposure chamber and under field conditions. All sensors used in the study are commercially available. O3 is determined according to the specifications of the manufacturers, without modification of the model equation proposed by the manufacturers.JRC.H.4-Transport and air qualit

Intercomparison Exercise for Heavy Metals in PM10

The Joint Research Centre (JRC) has carried out an Intercomparison Exercise (IE) for the determination of heavy metals in particulate matter (PM10). The IE focussed on Lead (Pb), Arsenic (As), Nickel (Ni) and Cadmium (Cd), the heavy metals regulated by the 1st and 4th Daughter Directives for Air Pollution. Copper (Cu), Chromium (Cr) and Zinc (Zn), the elements included in the EMEP programme together with Aluminium (Al), Cobalt (Co), Iron (Fe), Manganese (Mn) and Vanadium (V) were also tested. Fourteen Laboratories, generally members of the Network of Air Quality Reference Laboratories (AQUILA), participated in the IE. The participants mainly used microwave digestion with nitric acid and hydrogen peroxide and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) or Graphite Furnace Atomic Absorption Spectrometry (GF-AAS) for analysis as recommended in the reference method (EN 14902). However, a few participants used other methods: Energy Dispersive X-ray Fluorescence (EDXRF), Atomic Emission Spectrometry (ICP-AES) and Voltammetry for analysis and vaporisation on hot plate before microwave digestion, Soxhlet extraction, high pressure or cold Hydrogen Fluoride methods for digestion. Each participant received 5 samples to be analysed: a liquid sample prepared by dilution of a Certified Reference Material (CRM), a solution of a dust CRM sample digested by the JRC13F, a sub-sample of a dust CRM that each participating laboratory had to digest and analyse, a solution prepared by JRC after digestion of an exposed filter and a pair of filters (one blank filter and one exposed filter) to be digested and analysed by each participant. For 89 % of all types of samples, the DQOs of the 1st and 4th European Directives (uncertainty of 25 % for Pb and 40 % for As, Cd and Ni) were met. All together, this is a very good score. The best results were obtained for the liquid CRM, dust CRM digested by JRC, dust CRM and filter digested by JRC with 92, 90, 96 and 93 % of DQOs being met, respectively. It was found that the DQOs were not met if the difference of acidity between test samples and participant calibration standards was high. Conversely, only 76 % of DQOs were met for the filter to be digested by each participant with (about 85 % for Cd and Ni, 73/64 % for Pb and As, the most difficult element to determine). The worst results were associated with special events: explosion in microwave oven during digestion for two participants, a wrong dilution factor used by one participant and a huge contamination in the blank filter for another participant. Among the two explosions, one of them was probably the effect of a lack of temperature control in the digestion vessel. For the other explosion, the microwave digestion and the digestion program advised by EN 14902 is to be questioned. Moreover, satisfactory results were obtained using Soxhlet extraction, high pressure method and cold Hydrogen Fluoride digestion methods which are not presented in EN 14902. The DQOs of As and Cd could not be met with EDXRF whose limit of detection was too high for these two elements and for Cd using Voltammetry which suffered a strong interference for this element. Regarding the methods of analysis, apart the points mentioned just before about EDXRF and Voltammetry, good results were observed using ICP-OES for Cd, Ni and Pb. A few discrepancies were also registered for GF-AAS and ICP-MS but they were created by the special events or acidity problem mentioned before. This shows that even though GF-AAS and ICP-MS are found suitable, the implementation by each participant may be responsible for important mistakes.JRC.H.4-Transport and air qualit

Analysis of Heavy Metals in PM10 - Measuring Methods and Uncertainty of Measurement

The Joint Research Centre has carried out an Intercomparison Exercise (IE) for the determination of Lead, Arsenic, Nickel and Cadmium, the heavy metals regulated by the European Directives. Fourteen Laboratories, participated in the IE using generally microwave digestion and ICP-MS or GF-AAS for analysis as recommended in the CEN reference method. However, a few participants used other analytical (EDXRF, AES and Voltammetry) and digestion (hot plate before microwave digestion, Soxhlet extraction, high pressure or cold Hydrogen Fluoride) methods. Each participant analysed 5 types of samples: a liquid Certified Reference Material (CRM), two sub-samples of a dust CRM (one digested by the JRC and one to be digested by the participant) and two air-filters (one digested by JRC and one to be digested by the participant). After data treatment, conclusions are drawn about the capacity of participants to meet the Data Quality Objectives of the Directives. It is checked that the differences between participant results and the reference values of the test samples remain within the reported uncertainty. The repeatability/reproducibility of the method of measurements and of all laboratories are evaluated.JRC.H.4-Transport and air qualit

Laboratory and Field Inter-Comparisons of NO2 Diffusive Samplers

Abstract not availableJRC.H-Institute for environment and sustainability (Ispra

Modelling of The Uptake Rate of the Nitrogen Dioxide Palmes Diffusive Sampler Based on the Effect on the Environmenttal Factors.

Abstract not availableJRC.H-Institute for environment and sustainability (Ispra

Interlaboratory Comparison Exercise for the Determination of As, Cd, Ni and Pb in PM10 in Europe

This paper presents the results of an intercomparison exercise for the determination of arsenic (As), cadmium (Cd), nickel (Ni) and lead (Pb) in PM10 which are regulated by the European Directives for ambient air quality. Thirteen laboratories participated, generally using the European reference methods of measurements which consist of a microwave digestion followed by analysis with ICP-MS or GF-AAS. Each participant was asked to analyse five test samples: a liquid Certified Reference Material (CRM), two sub-samples of a NIST dust CRM (one already digested and one to be digested by the participants) and two loaded filters (one already digested and one to be digested by the participants). Participants were able to reach the Data Quality Objectives (DQOs) of the European Directives (uncertainty of 25 % for Pb and 40 % for As, Cd and Ni) for 93 % of all test samples except for the loaded filter that they had to digest by themselves. In fact, only 76 % of DQOs were met for this test sample, the closest to a routine sample analysis in the laboratory. The difficulties in analysing this test sample came from digestion, preparation and contamination processes mainly. Satisfactory results were also obtained using other digestion techniques (Soxhlet extraction and high pressure methods) and analytical methods (ICP-OES for Cd, Ni and Pb, EDXRF for Pb and Ni or Voltammetry for As, Ni, and Pb). Participants claimed uncertainties of about 10 % for Pb and between 15 and 20 % for As, Cd and Ni. These uncertainties were confirmed for 77 % of results. The reproducibility of the methods of measurements was between 41 and 54 % while repeatability remained between 5 and 12 % except for the analysis of As on filter which was up to 20 %. A majority of participant results showed higher between-day variability (14 ± 11 %) than within-day variability (6.0 ± 5.3 %).JRC.DDG.F.9-Sustainable Transport (Ispra

Interlaboratory comparison exercise for the determination of As, Cd, Ni and Pb in PM10 in Europe

International audienc

The use of passive diffusion tubes for measuring concentrations of nitrogen dioxide in air

Passive diffusion tubes have been widely used in Europe for spatial and temporal measurement of NO2 concentrations. The method is cheap, simple, and provides concentration data in most circumstances that are sufficiently accurate for assessing exposure and compliance with Air Quality criteria. Tube-type diffusion samplers are prone to several sources of uncertainty, arising from the materials of construction, the absorbent used, the methods of preparation, the details of their deployment (including the exposure time) and the analytical methods used to establish the concentration of nitrite ion absorbed. This review considers the major sources of uncertainty, and reports on the many experiments aimed at identifying and minimising uncertainties, including modifications to the simple open tube devices that were originally developed in the 1970s