Nitrous oxide emissions from unpolluted and polluted rivers of the Paquequer Basin (Teresópolis, Rio de Janeiro)

Dissolved N₂O concentrations and water-air fluxes (using floating chambers) were measured along the Paquequer River and in some tributaries. Concentrations ranged from 0.32 to 4.7 μgN.L^-1 and fluxes from <0.56 to 141 μgN.m^-2.h^-1. The lowest N₂O concentrations and fluxes were found in the headwaters of Paquequer river and in Príncipe brook, and the highest within the urban boundaries and in Fischer brook. Dissolved N₂O concentrations and water-air fluxes were positively correlated with highly variable NH₄ ⁺concentrations. Mass emission rate of N₂O in the polluted stretch of Paquequer River is likely to be higher than the estimate 0.62 kgN.day^-1 since transfer by turbulent degassing in falls, cascades and rapids were not determined.

nitrous oxide; river water pollution; urban sewage