H54B-03:
Using a Multi Sensor Core Logger to investigate hydraulic conductivity, specific yield, bulk density and organic matter in six peatland complexes located in southern Quebec, Canada
Friday, 19 December 2014: 4:30 PM
Marc-André Bourgault1,2, Marie Larocque1,2, Marjolaine Roux2, Michelle Garneau1,3 and Guillaume St-Onge4, (1)GEOTOP-UQAM, Montreal, QC, Canada, (2)University of Quebec at Montreal UQAM, Science de la terre et de l'atmosphère, Montreal, QC, Canada, (3)University of Quebec at Montreal UQAM, Géographie, Montreal, QC, Canada, (4)University of Quebec at Rimouski UQAR, Rimouski, QC, Canada
Abstract:
Flow dynamics within peatlands support several internal processes such as water and carbon storage and are governed by variations in hydraulic conductivity (Kv, Kh), specific yield (ne), and bulk density (ρbulk). Peat carbon storage is estimated using the loss-on-ignition method whereas hydraulic parameters are measured using standard field and laboratory methods that are highly time consuming. Automatic methods such as the continuous measurement of physical properties using a Multi Sensor Core Logger (MSCL) would be a rapid alternative in estimating these variables. The aims of this study are to 1) evaluate the use of MSCL as a tool to measure ρbulk on peat samples, 2) derive analytical solution linking K, ne and organic matter to ρbulk using the same samples and 3) investigate the spatial variability of K, ne and organic matter in six peatland complexes formed in different hydrogeomorphological environments of the St. Lawrence lowlands (Quebec, Canada). The study sites were first characterised using fine scale LiDAR digital elevation data. Three cores were sampled at three different locations (upstream, intermediate and downstream), with a total of 48 peat cores collected using a stainless steel Box corer (8 x 8 x 100 cm). The cores were used to measure Kv and Kh (Modified Cube Method-MCM), organic matter (Standard method from Dean, 1974) and ρbulk (Gamma Ray Attenuation Method-GRAM with MSCL and Standard method from Dean, 1974). Piezometric variations were recorded at every 5 minutes and used to evaluate ne of the surface peat layer (acrotelm) following rain events. Preliminary results show ρbulk (GRAM) variations between 0.60 and 1.05 g/cm3 which compare well with laboratory-derived data. K (MCM) values vary from 0.59 cm/s to 1.30*10-5 cm/s. GRAM ρbulk are logarithmically correlated to K (MCM) (r2 = 0.75) and could therefore be used as a proxy to evaluate spatial variability of K within peatland complexes. Finally, analyses are under way to link GRAM ρbulk to ne and organic matter.
