『Abstract
Recent studies of chemical weathering of andesitic-dacitic material
on high-standing islands (HSIs) have shown these terrains have
some of the highest observed rates of chemical weathering and
associated CO2 consumption yet reported.
However, the paucity of stream gauge data in many of these terrains
has limited determination of chemical weathering product fluxes.
In July 2006 and March 2008, stream water samples were collected
and manual stream gauging was performed in watersheds throughout
the volcanic island of Dominica in the Lesser Antilles. Distinct
wet and dry season solute concentrations reveal the importance
of seasonal variations on the weathering signal. A cluster analysis
of the stream geochemical data shows the importance of parent
material age on the overall delivery of solutes. Observed Ca:Na,
HCO3:Na and Mg:Na ratios suggest crystallinity
of the parent material may also play an important role in determining
weathering fluxes. From total dissolved solids concentrations
and mean annual discharge calculations we calculate chemical weathering
yields of (6-106 t km-2 a-1), which are
similar to those previously determined for basalt terrains. Silicate
fluxes (3.1-55.4 t km-2 a-1) and associated
CO2 consumption (190-1575×103
mol km-2 a-1) determined from our study
are among the highest determined to date. The calculated chemical
fluxes from our study confirm the weathering potential of andesitic-dacitic
terrains and that additional studies of these terrains are warranted.』
1. Introduction
2. Study area background
2.1. Geology
2.2. Climate and hydrology
2.3. Topography and soils
3. Sampling and analytical methods
3.1. Sample methodology
3.2. Stream gauging and annual discharge determination
3.3. Water analysis
3.4. Data interpretation
4. Results and discussion
4.1. Representativeness of the data
4.2. Concentration of major elements and statistical analysis
4.3. Source of solutes
4.3.1. Weathering of primary minerals and soils
4.3.1.1. Ca:Mg
4.3.1.2. Sum of cations in stream water
4.3.1.3. Source of cations in stream water
4.3.2. Cluster analysis
4.4. Dominica River chemistry compared to silicate terrains worldwide
5. Chemical weathering and potential CO2
consumption
5.1. Chemical weathering rates
5.2. Silicate weathering and CO2 consumption
6. Conclusions
Acknowledgments
References