Emission of NO and deposition of O₃ in a tropical forest system

Abstract

Rates for emission of NO and deposition of O 3 were measured at a tropical forest site in Reserve Adolfo Ducke, near Manaus, Brazil. Two independent techniques were used to determine the NO flux: (1) a soil enclosure method and (2) a method based on simultaneous observations of NO and O 3 vertical profiles at night, when NO is irreversibly removed by reaction with O 3 . Results obtained using the two techniques agreed well, giving an average NO flux of 5.2±1.7×10 10 molecules cm −2 s −1 and an average vertical exchange coefficient of 2.2×10 3 cm 3 s −1 . Sources of NO from tropical forest soils may be important for global atmospheric chemistry. Rapid removal of O 3 was observed in the lowest levels of the forest. The nocturnal deposition rate was estimated to be 5.6±2.5 ×10 11 molecules cm −2 s −1 through the 6 m level. The large deposition rate for O 3 is consistent with the strong sink inferred from observations of ozone in the Amazon region.