Nitrous oxide (n2o) and methane (ch4) in rivers and estuaries of northwestern borneo

Abstract

Nitrous oxide ( N2O) and methane ( CH4) are atmospheric trace gases which play important roles in the climate and atmospheric chemistry of the Earth. However, little is known about their emissions from rivers and estuaries, which seem to contribute significantly to the atmospheric budget of both gases. To this end concentrations of N2O and CH4 were measured in the Rajang, Maludam, Sebuyau and Simunjan rivers draining peatland in northwestern (NW) Borneo during two campaigns in March and September 2017. The Rajang River was additionally sampled in August 2016 and the Samunsam and Sematan rivers were additionally sampled in March 2017. The Maludam, Sebuyau, and Simunjan rivers are typical "blackwater" rivers with very low pH (3.7-7.8), very high dissolved organic carbon (DOC) concentrations (235-4387 mmol L -1) and very low O2 concentrations (31-246 μ mol L -1; i.e. 13 %-116 % O2 saturation). The spatial and temporal variability of N2O and CH4 concentrations (saturations) in the six rivers or estuaries was large and ranged from 2.0 nmol L -1 (28 %) to 41.4 nmol L -1 (570 %) and from 2.5 nmol L -1 (106 %) to 1372 nmol L -1 (57 459 %), respectively. We found no overall trends of N2O with O2 or NO 3 - , NO 2 -