Calcite dissolution kinetics at the single particle scale
are determined.
It is demonstrated that at high undersaturation and in the absence
of inhibitors the particulate mineral dissolution rate is controlled
by a saturated calcite surface in local equilibrium with dissolved
Ca2+ and CO3
2– coupled with
rate determining diffusive transport of the ions away from the surface.
Previous work is revisited and inconsistencies arising from the assumption
of a surface-controlled reaction are highlighted. The data have implications
for ocean modeling of climate change.
Although, in principle,
the Coulter Counter technique yields an
absolute measure of particle volume, in practice, calibration is near-universally
employed. For regularly shaped and non-biological samples, the use
of latex beads for calibration can provide sufficient accuracy. However,
this is not the case with particles encased in biogenically formed
calcite. To date, there has been no effective route by which a Coulter
Counter can be calibrated to enable the calcification of coccolithophores—single
cells encrusted with biogenic calcite—to be quantified. Consequently,
herein, we seek to answer the following question:
to what
extent can a Coulter Counter be used to provide accurate information
regarding the calcite content of a single
-
species
coccolithophore population?
Through the development of a
new calibration methodology, based on the measurement and dynamic
tracking of the acid-driven calcite dissolution reaction, a route
by which the cellular calcite content can be determined is presented.
This new method allows, for the first time, a Coulter Counter to be
used to yield an absolute measurement of the amount of calcite per
cell.
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