ABSTRACT The Air Quality Directive (2008/50/EC) asks for the organisation of quality assurance pr... more ABSTRACT The Air Quality Directive (2008/50/EC) asks for the organisation of quality assurance programmes for air quality assessment methods at European level. Since the early 1990s the European Reference Laboratory for Air Pollution (ERLAP) of the EC’s Joint Research Centre (JRC) has carried out Intercomparison Exercises (IE) for air pollution measurements on a regular basis for Member States of the EU. All European National Reference Laboratories (NRLs), joined together in the AQUILA Network, are obliged to participate in IE. More than 45 laboratories and institutes, coming from 35 European countries, have participated in the IE during the last 15 years. The results of the most recent IE which took place from 2005 to 2010 are described. Gas mixtures with some concentrations of CO, SO2, NOx, and O3 were generated and measured by the participants. With the results of the participants’ z’-score, En number, repeatability and reproducibility, outlier through the test of Grubb were evaluated. Keywords: air quality, intercomparison, ozone, sulphur dioxide, nitrogen monoxide, nitrogen dioxide, carbon monoxide. 1 Introduction With the adoption of Directive 2008/50/EC [1] on ambient air quality and cleaner air for Europe, a framework for a harmonized air quality assessment in Europe was set. This Directive specifies, among others, the reference methods
The PEOPLE (Population Exposure to Air Pollutants in Europe) project is presented. With the suppo... more The PEOPLE (Population Exposure to Air Pollutants in Europe) project is presented. With the support of the media and thousands of citizens, at six European cities (Brussels, Lisbon, Bucharest, Ljubljana, Dublin, Madrid), samples of personal, indoor and outdoor air pollution concentrations were collected. Air quality in cities is controlled by the relationship between emissions of and dispersion of pollutants. Transportation
The influence of environmental parameters on the uptake rate of the nitrogen dioxide (NO(2)) Palm... more The influence of environmental parameters on the uptake rate of the nitrogen dioxide (NO(2)) Palmes diffusive sampler was investigated. The main factors affecting the uptake rate were found to be wind speed, the preponderant factor, followed by relative humidity and temperature. The NO(2) concentration and exposure time, as well as the interactions among the factors were not found to have a significant influence on the uptake rate of the Palmes sampler. As a result, a model able to predict the uptake rate of the Palmes sampler was established. In addition, by using the model-predicted uptake rate, the agreement between chemiluminescence and the Palmes sampler during the field tests was improved. The NO(2) Palmes diffusive sampler was shown to comply with the requirement on accuracy defined by the European Directive for the indicative methods of measurements.
Hereafter, an assessment of the ability of the chemiluminescence method to measure ambient NO2 wi... more Hereafter, an assessment of the ability of the chemiluminescence method to measure ambient NO2 with an accuracy within 15%, as requested by the data quality objective of European directive 1999/30/CE, is presented. In general, uncertainty is evaluated using the response to reference materials or by means of inter-comparisons used to determine some statistics like repeatability, reproducibility and calibration bias. These are incomplete approaches and the method of the Guide to the Expression of Uncertainty in Measurement, advised by the Directive, should be preferred. In fact, even if it requires a large data set, it allows the relative influence of all possible sources of uncertainty to be studied. The extent of NO2 uncertainty is mainly dependent on the level of NO. It is decreased by NOx and the correlation between NOx and NO. Furthermore, the uncertainty budget reveals that the contribution of accuracy of calibration standard, linearity, converter efficiency and drift of the analyser between calibration checks to the overall uncertainty is less important than the contribution of interference, mainly humidity and PAN in rural areas. The relative expanded uncertainty of the NO2 hourly average exceeds 30% for NO2 concentrations lower than 40 microg m(-3). Nevertheless, the data quality objective of 15% is reached for 200 microg m(-3), the hourly limit value of the European directive. On the contrary, at the limit value on the annual average, 40 microg m(-3), the data quality objective is not met if NO is higher than 100 microg m(-3). However, the data quality objective could be reached by correcting the measurements with the bias due to interference.
The need to collect data representative of overall urban pollution is all-important in order to m... more The need to collect data representative of overall urban pollution is all-important in order to monitor the population exposure. High spatial resolution monitoring using diffusive samplers allows studying of the urban pollutant distribution, thus enabling deeper investigation of their generation and diffusion mechanisms. Nevertheless, such a monitoring campaign has a certain cost. In this study we point out how to find the best compromise between the number of necessary measurements and the affordable costs for monitoring campaigns. We also describe an innovative method for the proper design of a fixed urban monitoring network by means of preliminary high spatial resolution campaigns using diffusive samplers. Four European capital cities (Dublin, Madrid, Paris and Rome) were monitored six times, each time for seven days. Benzene, toluene, ethylbenzene, xylenes (BTEX) and NO(2) concentrations were measured at 146 sites in Dublin, 293 in Madrid, 339 in Paris and 290 in Rome. Multiscale grids have been drawn which ranged in mesh size from 500 m to 2 km. The statistical processing of data produced a twofold result: the creation of isoconcentration maps with geostatistical procedures, and an algorithm aimed at locating the minimum number of sampling sites where the fixed monitoring stations should be placed. Average urban levels estimated on the basis of these selected sites differ by less than 8% from those calculated on the whole populations of the sampled points. The aim of this work is to investigate how far the resolution of a monitoring campaign of urban pollution by diffusive sampling can be reduced, thus making the monitoring less expensive in terms of human and financial resources, while preserving the same quality of the results that could be achieved with a higher resolution. We found that there is no significant loss of information when the resolution of the monitoring grid for BTEX is lowered to a mesh size of 1.85 km, that is a sampling site each 3.4 km(2), and that the minimum number of sampling sites to be used is N = 0.29 A, where A is the urban surface to be monitored (in km(2)). As the spatial distribution of NO(2) is less sensitive to the distance from the emission source than that of BTEX, this relationship could be retained as a valid lower limit for the mesh grid size also for NO(2) monitoring.
This study presents an evaluation of the extent of differences between measurements performed by ... more This study presents an evaluation of the extent of differences between measurements performed by O(3) and NO(2) diffusive samplers and by the reference methods for diffusive samplers commercially available. The tests were performed in an exposure chamber under extreme conditions of controlling factors and under field conditions. For NO(2), the results of the laboratory experiments showed that most of the diffusive samplers were affected by extreme exposure conditions. The agreement between the samplers and the reference method was better for the field tests than for the laboratory ones. The estimate of the uptake rate for the exposure conditions using a model equation improved the agreement between the diffusive samplers and the reference methods. The agreement between O(3) measured by the diffusive samplers and by the reference method was satisfactory for 1-week exposure. For 8-hour exposures, the diffusive samplers with high uptake rates quantified better the O(3) concentration than the samplers with low uptake rates. As for NO(2), the results of the O(3) field tests were in better agreement with the reference method than the ones of the laboratory tests. The field tests showed that the majority of diffusive samplers fulfils the 25% uncertainty requirement of the NO(2) European Directive and the 30% uncertainty requirement of the O(3) European Directive for 1-week exposure.
A study of the equivalence to the reference methods of the Radiello samplers for ozone (O(3)) and... more A study of the equivalence to the reference methods of the Radiello samplers for ozone (O(3)) and benzene as well as the membrane-closed Palmes tube (MCPT) for nitrogen dioxide (NO(2)) is presented. These samplers benefit from new model equations capable of estimating their uptake rate. For O(3), the aim here was to demonstrate the equivalence for the reference period of 8 h and 120 microg m(-3), the target value of the 3rd European Daughter Directive. For benzene, the demonstration of equivalence to the annual limit value of 5 microg m(-3) of the 2nd European Daughter Directive was examined. In the case of NO(2), the equivalence to the annual limit value of the 1st European Daughter Directive (40 microg m(-3)) was considered. Results show that the radial sampler for O(3) fails to meet the Data Quality Objective (DQO) for continuous monitoring. However, with an expanded uncertainty of less than 30%, the O(3) diffusive sampler fulfils the DQO for indicative measurements. For benzene, the Radiello sampler exposed for 7 days gave satisfying results showing the ability of the sampler to meet the DQO of the reference method. Nevertheless, the field tests should be complemented by measurements for a wider range of benzene concentrations. In the case of NO(2), all the results of the laboratory and field experiments respected the requirements necessary for the demonstration of equivalence. Overall, these findings thus show that the Radiello sampler and the MCPT are equivalent to the reference methods only for assessment of benzene and NO(2), respectively.
ABSTRACT Estimating measurement uncertainty for NO2 and PM10 is a complex issue that is normally ... more ABSTRACT Estimating measurement uncertainty for NO2 and PM10 is a complex issue that is normally addressed by experimentalists specifically for every type of instrument and measurement. On the other hand, an estimate of the maximum expected measurement uncertainty is needed when a numerical model is to be evaluated against observations, as proposed in Thunis et al. (2012, referred to as T2012). In a companion paper (Thunis et al., 2013, referred to as T2013) a simplified formulation of the measurement uncertainty in function of the measured concentration is proposed and applied to the simpler case of Ozone. In this paper the same approach is applied for NO2 and PM10, but using different techniques for the uncertainty estimation. For NO2 the Guide to the expression of Uncertainty in Measurement JCGM (2008, referred to as GUM) approach is used and applied on each urban AirBase (1997) measurement over the year 2009. For PM10, the method of the Guide for the Demonstration of Equivalence (ECWG, 2010) is used on data obtained with two different PM samplers used in parallel either during specific monitoring campaign or as available within the AirBase database. The resulting concentration dependent measurement uncertainties are then used to update the MQO (Model Quality Objective) and MPC (Model Performance Criteria) proposed in T2012. An estimate of the measurement uncertainty for annual means is proposed as well.
Energy Dispersive X-ray Fluorescence (EDXRF) was compared to Inductively Coupled Plasma Mass Spec... more Energy Dispersive X-ray Fluorescence (EDXRF) was compared to Inductively Coupled Plasma Mass Spectrometer (ICP-MS) for the measurements of elements (Mg, Al, Si, S, Cl, K, Ca, Ti, V, Cr, Fe, Co, Ni, Mn, Cu, Zn, As, Br, Sr, Pb, Mo, Cd, Sn and Sb) in particulate matter (PM 10 ) collected on Teflon and two types of quartz filters at different sites. Two different methods of EDXRF analysis, linear calibration and standardless analysis, were studied. For the linear calibration, Pb, Mn, Fe, Cu, Ti and Zn were found to be site and filter type independent whereas Ca was only site independent. The site effect was evidenced for K, As, Ni, and V for quartz filter. The standardless EDXRF analysis showed better results than linear calibrations except for As, Co and V for Teflon filters and Cr and V for quartz filters. The measurement uncertainty of standardless EDXRF analysis was estimated by establishing a model equation. The measurement uncertainty estimated with this model equation was confirmed by field experiments provided that elemental masses exceeded observed thresholds. It was found that standardless EDXRF analysis is able to quantify most of the elements studied, particularly on Teflon filters rather than quartz filters. The standardless EDXRF analysis complies with the data quality objectives (DQO) of European Directives to measure Pb in PM 10 for three types of filters, even at concentrations lower than limit values (LV). The detection limits (MDL) of standardless EDXRF analysis for measuring As and Cd were found to be insufficient to meet the legislative requirements. The MDL of Ni was sufficiently low for measurements; however, measurement uncertainties remained higher than the DQO at the lower concentrations than LV.
... the analysis of heavy metals (in food, soil, medicinal plants, water, etc.) because it can be... more ... the analysis of heavy metals (in food, soil, medicinal plants, water, etc.) because it can be fully automated, can be used for multi-element analysis, and it requires only relatively low investment costs (eg, Nedeltcheva et al., 2005; Locatelli and Torsi, 2003; Feeney and Kounaves ...
Hereafter, a modification of the traditional Palmes diffusion tube by fitting a membrane at the o... more Hereafter, a modification of the traditional Palmes diffusion tube by fitting a membrane at the open end of the tube is presented. The membrane is placed to avoid the effect of turbulence due to wind speed. Further optimisations of the volume of absorbent and number of meshes retaining the absorbent are also described. Finally, the sampler is placed in an air proof container and is ready to use in order to improve the quality of measurement.
This paper presents the results of an intercomparison exercise for the determination of arsenic (... more This paper presents the results of an intercomparison exercise for the determination of arsenic (As), cadmium (Cd), nickel (Ni) and lead (Pb) in PM 10 , which are regulated by the European Directives for ambient air quality. Thirteen laboratories participated, generally using the European reference methods of measurement which consist of a microwave digestion followed by analysis with either ICP-MS or GFAAS. 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).
The strength of the described methodology derives from its comprehensive approach. The preliminar... more The strength of the described methodology derives from its comprehensive approach. The preliminary tests check whether source/factors belong to a given source category. The performance tests assess the bias with respect to pre-defined quality standards. A synthetic testing dataset is provided including the procedure for its creation. The new SID indicator is suitable to compare source or factor profiles.
ABSTRACT The Air Quality Directive (2008/50/EC) asks for the organisation of quality assurance pr... more ABSTRACT The Air Quality Directive (2008/50/EC) asks for the organisation of quality assurance programmes for air quality assessment methods at European level. Since the early 1990s the European Reference Laboratory for Air Pollution (ERLAP) of the EC’s Joint Research Centre (JRC) has carried out Intercomparison Exercises (IE) for air pollution measurements on a regular basis for Member States of the EU. All European National Reference Laboratories (NRLs), joined together in the AQUILA Network, are obliged to participate in IE. More than 45 laboratories and institutes, coming from 35 European countries, have participated in the IE during the last 15 years. The results of the most recent IE which took place from 2005 to 2010 are described. Gas mixtures with some concentrations of CO, SO2, NOx, and O3 were generated and measured by the participants. With the results of the participants’ z’-score, En number, repeatability and reproducibility, outlier through the test of Grubb were evaluated. Keywords: air quality, intercomparison, ozone, sulphur dioxide, nitrogen monoxide, nitrogen dioxide, carbon monoxide. 1 Introduction With the adoption of Directive 2008/50/EC [1] on ambient air quality and cleaner air for Europe, a framework for a harmonized air quality assessment in Europe was set. This Directive specifies, among others, the reference methods
The PEOPLE (Population Exposure to Air Pollutants in Europe) project is presented. With the suppo... more The PEOPLE (Population Exposure to Air Pollutants in Europe) project is presented. With the support of the media and thousands of citizens, at six European cities (Brussels, Lisbon, Bucharest, Ljubljana, Dublin, Madrid), samples of personal, indoor and outdoor air pollution concentrations were collected. Air quality in cities is controlled by the relationship between emissions of and dispersion of pollutants. Transportation
The influence of environmental parameters on the uptake rate of the nitrogen dioxide (NO(2)) Palm... more The influence of environmental parameters on the uptake rate of the nitrogen dioxide (NO(2)) Palmes diffusive sampler was investigated. The main factors affecting the uptake rate were found to be wind speed, the preponderant factor, followed by relative humidity and temperature. The NO(2) concentration and exposure time, as well as the interactions among the factors were not found to have a significant influence on the uptake rate of the Palmes sampler. As a result, a model able to predict the uptake rate of the Palmes sampler was established. In addition, by using the model-predicted uptake rate, the agreement between chemiluminescence and the Palmes sampler during the field tests was improved. The NO(2) Palmes diffusive sampler was shown to comply with the requirement on accuracy defined by the European Directive for the indicative methods of measurements.
Hereafter, an assessment of the ability of the chemiluminescence method to measure ambient NO2 wi... more Hereafter, an assessment of the ability of the chemiluminescence method to measure ambient NO2 with an accuracy within 15%, as requested by the data quality objective of European directive 1999/30/CE, is presented. In general, uncertainty is evaluated using the response to reference materials or by means of inter-comparisons used to determine some statistics like repeatability, reproducibility and calibration bias. These are incomplete approaches and the method of the Guide to the Expression of Uncertainty in Measurement, advised by the Directive, should be preferred. In fact, even if it requires a large data set, it allows the relative influence of all possible sources of uncertainty to be studied. The extent of NO2 uncertainty is mainly dependent on the level of NO. It is decreased by NOx and the correlation between NOx and NO. Furthermore, the uncertainty budget reveals that the contribution of accuracy of calibration standard, linearity, converter efficiency and drift of the analyser between calibration checks to the overall uncertainty is less important than the contribution of interference, mainly humidity and PAN in rural areas. The relative expanded uncertainty of the NO2 hourly average exceeds 30% for NO2 concentrations lower than 40 microg m(-3). Nevertheless, the data quality objective of 15% is reached for 200 microg m(-3), the hourly limit value of the European directive. On the contrary, at the limit value on the annual average, 40 microg m(-3), the data quality objective is not met if NO is higher than 100 microg m(-3). However, the data quality objective could be reached by correcting the measurements with the bias due to interference.
The need to collect data representative of overall urban pollution is all-important in order to m... more The need to collect data representative of overall urban pollution is all-important in order to monitor the population exposure. High spatial resolution monitoring using diffusive samplers allows studying of the urban pollutant distribution, thus enabling deeper investigation of their generation and diffusion mechanisms. Nevertheless, such a monitoring campaign has a certain cost. In this study we point out how to find the best compromise between the number of necessary measurements and the affordable costs for monitoring campaigns. We also describe an innovative method for the proper design of a fixed urban monitoring network by means of preliminary high spatial resolution campaigns using diffusive samplers. Four European capital cities (Dublin, Madrid, Paris and Rome) were monitored six times, each time for seven days. Benzene, toluene, ethylbenzene, xylenes (BTEX) and NO(2) concentrations were measured at 146 sites in Dublin, 293 in Madrid, 339 in Paris and 290 in Rome. Multiscale grids have been drawn which ranged in mesh size from 500 m to 2 km. The statistical processing of data produced a twofold result: the creation of isoconcentration maps with geostatistical procedures, and an algorithm aimed at locating the minimum number of sampling sites where the fixed monitoring stations should be placed. Average urban levels estimated on the basis of these selected sites differ by less than 8% from those calculated on the whole populations of the sampled points. The aim of this work is to investigate how far the resolution of a monitoring campaign of urban pollution by diffusive sampling can be reduced, thus making the monitoring less expensive in terms of human and financial resources, while preserving the same quality of the results that could be achieved with a higher resolution. We found that there is no significant loss of information when the resolution of the monitoring grid for BTEX is lowered to a mesh size of 1.85 km, that is a sampling site each 3.4 km(2), and that the minimum number of sampling sites to be used is N = 0.29 A, where A is the urban surface to be monitored (in km(2)). As the spatial distribution of NO(2) is less sensitive to the distance from the emission source than that of BTEX, this relationship could be retained as a valid lower limit for the mesh grid size also for NO(2) monitoring.
This study presents an evaluation of the extent of differences between measurements performed by ... more This study presents an evaluation of the extent of differences between measurements performed by O(3) and NO(2) diffusive samplers and by the reference methods for diffusive samplers commercially available. The tests were performed in an exposure chamber under extreme conditions of controlling factors and under field conditions. For NO(2), the results of the laboratory experiments showed that most of the diffusive samplers were affected by extreme exposure conditions. The agreement between the samplers and the reference method was better for the field tests than for the laboratory ones. The estimate of the uptake rate for the exposure conditions using a model equation improved the agreement between the diffusive samplers and the reference methods. The agreement between O(3) measured by the diffusive samplers and by the reference method was satisfactory for 1-week exposure. For 8-hour exposures, the diffusive samplers with high uptake rates quantified better the O(3) concentration than the samplers with low uptake rates. As for NO(2), the results of the O(3) field tests were in better agreement with the reference method than the ones of the laboratory tests. The field tests showed that the majority of diffusive samplers fulfils the 25% uncertainty requirement of the NO(2) European Directive and the 30% uncertainty requirement of the O(3) European Directive for 1-week exposure.
A study of the equivalence to the reference methods of the Radiello samplers for ozone (O(3)) and... more A study of the equivalence to the reference methods of the Radiello samplers for ozone (O(3)) and benzene as well as the membrane-closed Palmes tube (MCPT) for nitrogen dioxide (NO(2)) is presented. These samplers benefit from new model equations capable of estimating their uptake rate. For O(3), the aim here was to demonstrate the equivalence for the reference period of 8 h and 120 microg m(-3), the target value of the 3rd European Daughter Directive. For benzene, the demonstration of equivalence to the annual limit value of 5 microg m(-3) of the 2nd European Daughter Directive was examined. In the case of NO(2), the equivalence to the annual limit value of the 1st European Daughter Directive (40 microg m(-3)) was considered. Results show that the radial sampler for O(3) fails to meet the Data Quality Objective (DQO) for continuous monitoring. However, with an expanded uncertainty of less than 30%, the O(3) diffusive sampler fulfils the DQO for indicative measurements. For benzene, the Radiello sampler exposed for 7 days gave satisfying results showing the ability of the sampler to meet the DQO of the reference method. Nevertheless, the field tests should be complemented by measurements for a wider range of benzene concentrations. In the case of NO(2), all the results of the laboratory and field experiments respected the requirements necessary for the demonstration of equivalence. Overall, these findings thus show that the Radiello sampler and the MCPT are equivalent to the reference methods only for assessment of benzene and NO(2), respectively.
ABSTRACT Estimating measurement uncertainty for NO2 and PM10 is a complex issue that is normally ... more ABSTRACT Estimating measurement uncertainty for NO2 and PM10 is a complex issue that is normally addressed by experimentalists specifically for every type of instrument and measurement. On the other hand, an estimate of the maximum expected measurement uncertainty is needed when a numerical model is to be evaluated against observations, as proposed in Thunis et al. (2012, referred to as T2012). In a companion paper (Thunis et al., 2013, referred to as T2013) a simplified formulation of the measurement uncertainty in function of the measured concentration is proposed and applied to the simpler case of Ozone. In this paper the same approach is applied for NO2 and PM10, but using different techniques for the uncertainty estimation. For NO2 the Guide to the expression of Uncertainty in Measurement JCGM (2008, referred to as GUM) approach is used and applied on each urban AirBase (1997) measurement over the year 2009. For PM10, the method of the Guide for the Demonstration of Equivalence (ECWG, 2010) is used on data obtained with two different PM samplers used in parallel either during specific monitoring campaign or as available within the AirBase database. The resulting concentration dependent measurement uncertainties are then used to update the MQO (Model Quality Objective) and MPC (Model Performance Criteria) proposed in T2012. An estimate of the measurement uncertainty for annual means is proposed as well.
Energy Dispersive X-ray Fluorescence (EDXRF) was compared to Inductively Coupled Plasma Mass Spec... more Energy Dispersive X-ray Fluorescence (EDXRF) was compared to Inductively Coupled Plasma Mass Spectrometer (ICP-MS) for the measurements of elements (Mg, Al, Si, S, Cl, K, Ca, Ti, V, Cr, Fe, Co, Ni, Mn, Cu, Zn, As, Br, Sr, Pb, Mo, Cd, Sn and Sb) in particulate matter (PM 10 ) collected on Teflon and two types of quartz filters at different sites. Two different methods of EDXRF analysis, linear calibration and standardless analysis, were studied. For the linear calibration, Pb, Mn, Fe, Cu, Ti and Zn were found to be site and filter type independent whereas Ca was only site independent. The site effect was evidenced for K, As, Ni, and V for quartz filter. The standardless EDXRF analysis showed better results than linear calibrations except for As, Co and V for Teflon filters and Cr and V for quartz filters. The measurement uncertainty of standardless EDXRF analysis was estimated by establishing a model equation. The measurement uncertainty estimated with this model equation was confirmed by field experiments provided that elemental masses exceeded observed thresholds. It was found that standardless EDXRF analysis is able to quantify most of the elements studied, particularly on Teflon filters rather than quartz filters. The standardless EDXRF analysis complies with the data quality objectives (DQO) of European Directives to measure Pb in PM 10 for three types of filters, even at concentrations lower than limit values (LV). The detection limits (MDL) of standardless EDXRF analysis for measuring As and Cd were found to be insufficient to meet the legislative requirements. The MDL of Ni was sufficiently low for measurements; however, measurement uncertainties remained higher than the DQO at the lower concentrations than LV.
... the analysis of heavy metals (in food, soil, medicinal plants, water, etc.) because it can be... more ... the analysis of heavy metals (in food, soil, medicinal plants, water, etc.) because it can be fully automated, can be used for multi-element analysis, and it requires only relatively low investment costs (eg, Nedeltcheva et al., 2005; Locatelli and Torsi, 2003; Feeney and Kounaves ...
Hereafter, a modification of the traditional Palmes diffusion tube by fitting a membrane at the o... more Hereafter, a modification of the traditional Palmes diffusion tube by fitting a membrane at the open end of the tube is presented. The membrane is placed to avoid the effect of turbulence due to wind speed. Further optimisations of the volume of absorbent and number of meshes retaining the absorbent are also described. Finally, the sampler is placed in an air proof container and is ready to use in order to improve the quality of measurement.
This paper presents the results of an intercomparison exercise for the determination of arsenic (... more This paper presents the results of an intercomparison exercise for the determination of arsenic (As), cadmium (Cd), nickel (Ni) and lead (Pb) in PM 10 , which are regulated by the European Directives for ambient air quality. Thirteen laboratories participated, generally using the European reference methods of measurement which consist of a microwave digestion followed by analysis with either ICP-MS or GFAAS. 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).
The strength of the described methodology derives from its comprehensive approach. The preliminar... more The strength of the described methodology derives from its comprehensive approach. The preliminary tests check whether source/factors belong to a given source category. The performance tests assess the bias with respect to pre-defined quality standards. A synthetic testing dataset is provided including the procedure for its creation. The new SID indicator is suitable to compare source or factor profiles.
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Papers by M. Gerboles