Abstract
Investigation of anthropogenic versus natural controls of the carbon cycle in the Lagan River revealed a strong influence of carbonates.
This was evident by increasing pH values along the river as well as
isotopic compositions of the riverine dissolved inorganic carbon
(delta(13)C(DIC)) that approached expected values for carbonate
dissolution. This predominant influence of carbonates existed despite
their minor abundance of only similar to 5% in this densely populated
catchment basin and outlines their capacity of buffering anthropogenic
influences and CO2 turnover. These effects should be even more
pronounced in other rivers where carbonates occupy a larger proportion
of the catchment basin geology. Other controls on the riverine carbon
cycle were silicate weathering and respiratory turnover of organic
material that originated mainly from anthropogenic inputs and increased
the DIC pool by up to 26.6%. Predominant natural controls on the Lagan
River carbon cycle changed to anthropogenic ones closer to the mouth.
Before discharging into Belfast Lough, a recently installed weir caused
stagnant seawater to make up between 53% and 92% of the water mass.
Poor vertical mixing caused O-2 decreases and anaerobic sedimentary
activity that resulted in methane production. Recently installed
aerators at the sediment surface did not prevent ongoing
methanogenesis. This was documented by decreased pCO(2) and more
C-13-enriched DIC values at the sediment-water interface when compared
to those of surface waters from the same sampling sites. Installations
of such weirs in estuaries of other rivers may cause similar anoxic
effects that influence their biogeochemistry. (C) 2003 Elsevier B.V.
All rights reserved.
Original language | English |
---|---|
Pages (from-to) | 203-216 |
Number of pages | 14 |
Journal | Chemical Geology |
Volume | 200 |
Issue number | 3-4 |
DOIs | |
Publication status | Published - Oct 2003 |
Keywords
- river
- ground water
- carbonates
- anthropogenic influences
- stable carbon isotope
- major elements