[Show abstract][Hide abstract] ABSTRACT: 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.
Journal of Environmental Monitoring 09/2008; 10(8):941-50. · 2.09 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Exposure concentrations of aromatic compounds were correlated with variables derived from time-microenvironment-activity (TMA) diaries to understand the relationship between exposure patterns and commuting behaviour of the population in a case study in Madrid. Approximately 200 air pollution samples were taken during a one-day campaign by means of diffusive samplers. An approach to determine the importance of selected activities and locations relative to a baseline condition, defined by a sample of approximately 100 commuters is described. A regression model is applied to determine the relative importance of identified situations, whether related directly to transport behaviour or through a labelled situation. The regression defines a baseline exposure concentration level where activities act as multiplying factors. The relationship of this baseline level and the set of activity factors, assigned to the population considered, to the ambient background is explored for its application to future studies. The calculation of exposure concentration gradients from the regression provides a means to characterise of the relative importance of different activities. A good level of agreement, in particular for benzene, was evident between the observed exposure concentrations and those calculated using the regression model.
[Show abstract][Hide abstract] ABSTRACT: 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 and environmental tobacco smoke were important factors for exposure to the
air pollutant benzene. While collecting scientific data the project also helped to raise awareness of the public to air pollution
in general and more specifically to the importance of personal behaviour for exposure to air pollutants
[Show abstract][Hide abstract] ABSTRACT: This paper describes the experimental methodology and basic results of the PEOPLE project (Population Exposure to Air Pollutants in Europe). Simultaneous diffusive measurements of outdoor, indoor and human exposure benzene concentrations were made during one day campaigns. Six cities were assessed, namely: Brussels and Lisbon (22 October 2002), Bucharest and Ljubljana (27 May 2003), Madrid (3 December 2003) and Dublin (28 April 2004). In general, human exposure to benzene was higher than concentrations reported at urban background monitoring sites. Traffic was the dominant source of benzene in all the six cities that were studied. The highest exposure levels from the commuting groups were car users. The control group, with no influence from commuting or smoking, reported concentrations closer to the background level of the city. The smoking group had the highest level of exposure. The level of exposure of school children was similar to that of the commuting groups. Indoor locations that were influenced by smoking sources, or with free access to busy streets, reported relatively high concentrations. The highest indoor concentrations were measured in bars and inside motor vehicles. When considering the six cities together, a linear relationship was evident between ambient levels and human exposure. Daily median values of human exposure for non-smoking commuters were 1.5 times the level of urban background and 0.6 times the maximum outdoor value (hotspot).
[Show abstract][Hide abstract] ABSTRACT: 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.
Journal of Environmental Monitoring 03/2005; 7(2):169-74. · 2.09 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The results of a European level intercomparison involving measurements of 26 hydrocarbons (from C2 to C9) at ambient air concentration level are discussed. On-line sampling with cryo-GC-FID analysis was the most commonly used methodology among the 20 participating laboratories. The stability of the gas samples in the canisters; the calibration methodology, the separation of peaks and the low level of concentrations were identified as the most important factors, which contributed to the increase in the uncertainty of the measurement. Uncertainty values associated with the common method used for the quantification of each compound and exercise were also determined.