Titration profiles in seeded experiments with no added aspartic acid.

Black lines show observed profile and red dotted lines show predicted profile as explained in text. N.B. the x- and y-axes are not to the same scale for all the graphs.</p

Fig 6 -

Estimated a) aragonite precipitation rate and b) lag period at start of precipitation in experiments comparing Ω, starting seed mass and different waters. ASW = artificial seawater. Nat. = natural seawater. Error bars indicate 1 σ of duplicate precipitations. The reproducibility of estimated precipitation rates from duplicate experiments was typically 6% and was always <10%. (Reproducibility of lag periods was always better than 57%).</p

Peak centre and FWHM of the ν1 peak in the Raman spectra of precipitates containing different proportions of seed and <i>in vitro</i> precipitate.

a) Peak centre and b) Full width half maxima. The signatures of the seed are shown by the point at 100% seed. Points are means of 10 spectra and error bars are 1 standard deviation.</p

Profiles of titrant volume dosed over time in duplicate unseeded experiments in artificial seawater.

a), b) Ω = 19.2 and c), d) Ω = 6.9. b) and d) showed expanded x axes to compare rates of dosing of 1–5 mLs of titrant between duplicates (T1 and T2, show data from two titrators). Measured [DIC] at the start and during 2 of the precipitations are overlaid onto the graphs.</p

Predicted titrant dosing profiles assuming that all dosing replaces ions consumed in the epitaxial growth of CaCO₃ over the seed.

In this example we assume a precipitation rate of 617 μmol m-2 h-1 onto a seed of surface area of 4.2 m2 g-1 using different masses of seed and 0.6 M titrants.</p

This file consists of the supporting data tables.

(XLSX)</p

Scanning electron micrographs of aragonite precipitated at Ω = 11.2.

a) without aspartic acid and b) with 8.7 mM aspartic acid. Scale bars are 1 μm.</p

Raman of aspartic acid.

(DOCX)</p

Effect of processes on the DIC chemistry of seawater.

Precipitation reduces DIC, alkalinity and hence pH. Titrant dosing after precipitation returns the DIC to the starting composition (black dot). CO2 invasion and outgas modify the DIC but not the alkalinity of the seawater. CO2 invasion reduces pH and triggers the dosing of titrants which return the seawater to the starting pH but at a different DIC and alkalinity composition. Contours join points of equal pH (NBS scale).</p

Chemistry of the waters used for precipitations.

[Ca2+] and [Mg2+] is estimated for artificial seawater (based upon composition) and measured (by ICP-OES) for natural seawater.</p