Effects of the river breeze on the transport of gases in Central Amazonia

Abstract

River breezes occur regularly along the Amazonia river but little is known about their effects on air pollution. During the first week of August 2014, river breeze events were observed on two days on the banks of the Negro River, central Amazonia. The WRF-Chem model was used to analyze this period to understand the formation mechanism and the influence of the river breeze on the transport of pollutants such as ozone (O3) and carbon monoxide (CO). We show that the river breeze occurred due to a reduction of the easterly winds associated with the cooling of the waters of the Negro River. The river breeze was responsible for inhibiting the transport of pollutants to the East, increasing its concentrations while breeze circulation is observed, as well as a re-circulation of these gases on the riverbank where the breeze was associated. The strongest breeze occurred in a forest region which maintained the highest concentrations of CO and O3 on the East bank of the Negro River. In the Urban region, the breeze was less intense and had a shorter duration, however, it was still able to maintain higher concentrations of CO and O3 in the western region of the city of Manaus, which is a predominantly residential region and therefore, the population of this region lives in a more polluted environment during the occurrence of breezes.