NO_x Background Mixing Ratios in Surface Air Over Europe and the Atlantic Ocean

Summary

An O₃-NO chemiluminescence detector combined with a FeSO₄ converter was used to measure tropospheric NO₂ and NO at the UBA Station in Deuselbach, a rural Community about 90 km west of Mainz, and onboard research ships during north-south cruises in the Atlantic ocean. The mixing ratios of NO₂ found at Deuselbach had monthly mean values of 4.5 ppbv in summer, and 16 ppbv in winter. Mixing ratios of NO, by contrast, were by a factor of ten lower. The winter maximum attests to the importance of home heating as a source of NO_X. The data obtained so far during ship cruises indicate minimum values of about 25 pptv in the tropical and polar regions with a pronounced maximum of about 70 pptv in the northern hemisphere near 45° latitude, and a weaker secondary maximum in the middle latitudes of the southern hemisphere. Both maxima are ascribed to anthropogenic NO_X carried over the ocean within the circumpolar belt of the westerlies.