title: Differences between carbon dioxide levels over suburban and rural sites in Northern Spain.
abstract: OBJECTIVE
  A comparison between suburban and rural atmospheric carbon dioxide concentrations in Northern Spain is made.
  
  
  METHODS
  Measurements were carried out from April 2006 to November 2007 using MIR 9000 continuous analyzers based on the infrared technique. Two locations were established: a suburban site in Valladolid, a medium-sized city, and a rural location at CIBA, approximately 24 km northwest of Valladolid.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Applied Physics, Faculty of Sciences, University of Valladolid, c/ Prado de Magdalena s/n, 47071 Valladolid, Spain. magperez@fa1.uva.es
authors.forename: Ma Angeles
authors.initials: MA
authors.lastname: García
authors.forename: Ma Luisa
authors.initials: ML
authors.lastname: Sánchez
authors.forename: Isidro A
authors.initials: IA
authors.lastname: Pérez
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D000397:Air Pollution / Q000032:analysis*; D002245:Carbon Dioxide / Q000032:analysis*; D002947:Cities; D004784:Environmental Monitoring / Q000379:methods*; D012621:Seasons; D013030:Spain
chemical_list: D000393:Air Pollutants; D002245:Carbon Dioxide