Mean suburban CO(2) concentrations are 4.5 ppm higher than rural levels. Frequencies of suburban concentrations from 400 to 450 ppm were around twice the rural frequencies. The suburban daily evolution presented two maxima in the predawn hours and at 1900-2000 GMT, mainly associated to anthropogenic emissions which also affected maximum concentrations recorded in autumn-winter and minimum levels in summer. The rural variation with minimum values during the day and high levels at night is mainly related to vegetation activity which also impacts the highest CO(2) concentrations obtained in spring, coinciding with maximum vegetation growth. Boundary layer processes also affected variability of concentrations recorded at both sites. Air quality at the rural site was also influenced by air mass transport from the urban plume (S, SSE, and ESE), which had a mean CO(2) value of 402 ppm. By contrast, concentrations were low when SW-W and NW winds prevailed and brought cleaner air. The relationship between rural CO(2) concentrations and wind speed using a mathematical fit provides a valuable estimation of the background level at the site, 384.8 ppm.

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Air trajectory calculations are commonly found in a variety of atmospheric analyses. However, most of reported research usually focuses upon the transport of pollutants via trajectory routes and not on the trajectory itself. This paper explores the major areas of research in which air trajectory analyses are applied with an effort to gain deeper insights into the key points which highlight the necessity of such analyses. Ranging from meteorological applications to their links with living beings, air trajectory calculations become important tool especially when alternative procedures do not seem possible. This review covers the reports published during last few years illustrating the geographical distribution of trajectory applications and highlighting the regions where trajectory application research proves most active and useful. As a result, relatively unexplored areas such as microorganism transport are also included, suggesting the possible ways in which successful use of air trajectory research should be extended.