Determination and accuracy of VOC-fluxes above the pine/oak forest at Castelporziano

Concentrations of α-pinene, β-pinene and limonene were determined as two or three point profiles above the Mediterranean pine/oak forest at Castelporziano, Italy. Based on these, as well as on micrometecrological data, the fluxes of these compounds were estimated using the modified Bowen-ratio method and a log-profile fit. The accuracy of the calculated fluxes was estimated, resulting in errors around 50%, which were mainly produced by the relatively small concentration gradients observed. The dependence of emission fluxes on surface temperature was interpolated by three equations of the form F(T) = Fsexp(β•(T − TS)) for the three compounds. The three resulting temperature exponents β were significantly greater than the value for monoterpenes given by Guenther et al. (1993, J. Geophysical Research 18, 12,609–12,617). It is also greater than the corresponding value derived by Bertin et al. (1997, Atmospheric; Environment) from the isoprene model of Guenther et al. (1993, J. Geophysical Research 18, 12,609–12,617).