Fluids and Rocks - Introduction to Carbon Capture and Sequestration - page 444

out for the purpose of evaluating the corrosion rates of these glasses in
high-level radioactive waste repositories. Ancient glass artifacts buried in
soils or immersed in seawater for thousands of years provide a longer-
term view of weathering processes. Geological media with well-known
ages enable reconstruction of mineral weathering rates on time scales of
millions of years ( Figure 9.8.7 ) [9.40]. In all cases, long-term weathering
rates are orders of magnitude smaller than the rates observed in short-
term laboratory dissolution experiments. This is the main reason why
geochemists expect that mineral trapping will take tens of thousands of
years ( Figure 8.2.3 ), whereas laboratory experiments suggest that it
could occur hundreds of times more rapidly ( Figure 9.8.3 ).
Plagioclase
Years
Figure 9.8.7 Dissolution rate of plagioclase feldspar as a function of observation time
scale
Compilation of plagioclase feldspar dissolution rates as a function of the time scale of
observation. Measurements of the short-term dissolution rates of fresh samples of pure
feldspar yield relatively high rates ( ∼ 10 − 12 mol/m 2 s). Geochemical reconstructions of the
long-term dissolution rates of feldspar samples recovered from natural formations yield
much lower rates ( ∼ 10 − 16 mol/m 2 s). Figure reproduced from White and Brantley [9.40],
with permission from Elsevier.