L. Hellings et al., Origin and fate of dissolved inorganic carbon in interstitial waters of two freshwater intertidal areas: A case study of the Scheldt Estuary, Belgium, BIOGEOCHEMI, 51(2), 2000, pp. 141-160
Processes affecting the concentration and isotopic composition of dissolved
inorganic carbon (DIC) were investigated in pore waters of two freshwater
intertidal areas of the Scheldt Estuary, Belgium. Pore water delta(13)C(DIC
) values from marshes and mudflats varied from -27 to +13.4 parts per thous
and, these very large variations reflect the contribution of different carb
on sources to the DIC pool.
In pore waters of the upper mudflat, river water DIC and dissolution of cal
cite contribute to a lesser extent (10% and 16% respectively) to the total
DIC pool. Results indicate that inorganic carbon added to the pore water of
the mudflats has a delta(13)C value of +20.3 parts per thousand in May 199
8. These strongly enriched delta(13)C(DIC) values suggest that the major co
ntribution (up to three-quarters) to total DIC is CO2 derived from methanog
enesis.
In pore waters of the marshes, CO2 derived from organic matter degradation
(-27.5 parts per thousand) and river DIC (-11.5 to -16.1 parts per thousand
) are the major sources of inorganic carbon contribution to the total DIC p
ool. In pore waters from a marsh site colonised by willow trees, the contri
bution from CO2 derived from organic matter degradation is larger than in p
ore waters from an area with only reed vegetation. In the latter case river
water DIC is the major source of pore water DIC.