Cocheo Claudio, Sacco Paolo, Ballesta Pascual Perez, Donato Eugenio, Garcia Saul, Gerboles Michel, Gombert Dominique, McManus Brian, Patier Rosalia Fernandez, Roth Chris, de Saeger Emile, Wright Evelyn
Fondazione Salvatore Maugeri-IRCCS, via Svizzera 16, 35127 Padova, Italy.
J Environ Monit. 2008 Aug;10(8):941-50. doi: 10.1039/b806910g. Epub 2008 Jul 14.
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.
为监测人群暴露情况，收集能代表城市总体污染的数据至关重要。使用扩散采样器进行高空间分辨率监测有助于研究城市污染物分布，从而能更深入地探究其生成和扩散机制。然而，这样的监测活动有一定成本。在本研究中，我们指出如何在必要测量次数与监测活动可承受成本之间找到最佳平衡点。我们还描述了一种创新方法，通过使用扩散采样器进行初步高空间分辨率监测活动，来合理设计固定的城市监测网络。对四个欧洲首都城市（都柏林、马德里、巴黎和罗马）进行了六次监测，每次为期七天。在都柏林的146个地点、马德里的293个地点、巴黎的339个地点和罗马的290个地点测量了苯、甲苯、乙苯、二甲苯（BTEX）和二氧化氮浓度。绘制了网格大小从500米到2公里不等的多尺度网格。数据的统计处理产生了双重结果：使用地统计程序创建等浓度图，以及一种算法，旨在确定应设置固定监测站的最少采样点数量。根据这些选定地点估算的城市平均水平与根据采样点总体计算出的水平相差不到8%。这项工作的目的是研究通过扩散采样进行城市污染监测活动的分辨率能降低到何种程度，从而在人力和财力资源方面使监测成本更低，同时保持与更高分辨率监测所能达到的相同结果质量。我们发现，当BTEX监测网格的分辨率降低到网格大小为1.85公里（即每3.4平方公里一个采样点）时，信息没有显著损失，并且使用的最少采样点数量为N = 0.29A，其中A是要监测的城市面积（平方公里）。由于二氧化氮的空间分布对与排放源距离的敏感度低于BTEX，这种关系也可作为二氧化氮监测网格大小的有效下限保留。
