Origin of anthropogenic hydrocarbons and halocarbons measured in the summertime european outflow (on Crete in 2001)

[摘要] During the Mediterranean Intensive Oxidant Study MINOS in August 2001, 87 air samples werecollected at the ground-based station Finokalia (35°19'N, 25°40'E) on the north coast of Crete andsubsequently analysed by GC-MS. The analysis includes various hydrocarbons, organo-halogens, HCFCsand CFCs. These compounds have a wide variety of sources and sinks and a large range of atmosphericlifetimes. We evaluated the characteristics of the sampling site in terms of proximity to individual sources byplotting the measured variability of these species against lifetime. The resulting linear relationship suggeststhat the sampling site is representative of intermediate conditions between a remote site and one that is in thevicinity of a wide variety of sources. Our analysis of air mass origin and chemical ratios also showsthat several distinct anthropogenic sources influenced the atmospheric composition over Crete. Propaneobservations are compared to a global model to assess the fossil fuel related emission inventory. Althoughthe model reproduces the general pattern of the propane variations, the model mixing ratios aresystematically too low by a factor of 1.5 to 3, probably due to an underestimation of the propane emissionsfrom east European countries in the underlying global database EDGAR. Another important finding was thatmethyl chloroform, a compound banned under the Montreal protocol, showed significant enhancements frombackground, which were well correlated with CFC-113. This suggests continued use and emission of methylchloroform by one or more European countries. We also discuss the observed variations of methyl bromideand suggest that the significant peak observed on 12 August 2001 reflects heavy agricultural use as a soilfumigant in Italy.

[学科分类] 大气科学