Patterns in pCO_2 in boreal streams and rivers of northern Quebec, Canada

摘要

Here we examine the patterns in carbon dioxide partial pressure (pCO_2) measured in a number of small boreal streams (<5 km in length) in the northwestern boreal region of Quebec during the ice-free season and compare these to the patterns found in a major river (Eastmain River) and in a tributary in the same region. All systems were consistently supersaturated in CO_2 (range 450 to 5000 μatm) streams having both higher (mean 1850 μatm) and more variable pCO_2 than that of rivers (range 550 to 800 μatm). Stream pCO_2 was positively related to DOC concentration and stream segment length, both suggesting a direct influence of the surrounding landscape. Calculated stream water-air CO_2 fluxes ranged from 700 to over 3000 mg C m~(-2) d~(-1),up to 2 orders of magnitude higher than those measured in large rivers and lakes of the same region. Small streams, despite their extremely reduced areal coverage (1% of the aquatic surface), accounted for 25% of the total aquatic C emissions, and the resulting areal stream fluxes were comparable to those measured in different soils or wetlands in the region.