Photochemical studies in the savannah boundary layer during the wet season

A photochemical study including measurements of ozone, peroxides, and formaldehyde together with nitrogen oxides and the photolysis rate of nitrogen dioxide was conducted in the Venezuelan savannah during the wet season, September 1993. Pronounced diurnal variations were observed with midday maximum and early morning minimum concentrations for peroxides, formaldehyde, and ozone of 2/0.1, 1.5/0.2, and 15/2 ppbv, respectively. The NOx concentrations ranged from less than 0.4 ppbv during midday conditions to I ppbv in the evening. Evaluation of the photostationary state deviations indicated high production rates of ozone. These evaluations were however not in agreement with the observed concentrations. Possible explanations for this contradiction can be interferences in the NOx measurements or perturbations due to soil NO emissions.