Two-years of NO3 radical observations in the boundary layer over the Eastern Mediterranean

[摘要] This is the first study that investigates the seasonal variability ofnitrate (NO₃) radicals in the marine boundary layer over the EastMediterranean Sea. An extensive data set of NO₃ radical observations onthe north coast of Crete for more than two years (June 2001–September 2003) ispresented here. NO₃ radicals follow a distinct seasonal dependency withthe highest seasonally average mixing ratios in summer (5.6±1.2 pptv)and the lowest in winter (1.2±1.2 pptv). Episodes with high NO₃mixing ratios have been encountered mainly in polluted air massesoriginating from mainland Greece, Central and East Europe, and Turkey.Ancillary measurements of ozone, nitrogen dioxide (NO₂) andmeteorological parameters have been conducted and used to reveal possiblerelationship with the observed NO₃ variability. The acquired NO₂nighttime observations provide the up-to-date most complete overview ofNO₂ temporal variability in the area. The data show correlations of theNO₃ nighttime mixing ratios with temperature (positive), relativehumidity (negative) and to a lesser extend with O₃ (positive). Asinferred from these observations, on average the major sink of NO₃radicals in the area is the heterogeneous reaction of dinitrogen pentoxide(N₂O₅) on aqueous particles whereas the homogeneous gas phasereactions of NO₃ are most important during spring and summer. Theseobservations support a significant contribution of NO₃ nighttimechemistry to the oxidizing capacity of the troposphere.

[学科分类] 大气科学