3f is ikaite. Onset time (τ) under different pH, salinities (both in ASW and NaCl medium), temperatures and PO4 Metformin concentrations is illustrated in Fig. 4(a–d) and Table 2. At pH from 8.5 to 10.0, τ decreases nonlinearly with increasing pH; it decreases steeply at low pH and then slows down at high pH. At salinities from 0 to 105, in ASW, τ increases with salinity; in the NaCl medium, τ first increases with salinity and above salinity 70, it decreases slightly. τ is longer in ASW than in the NaCl medium under the same salinity conditions. There is no significant difference in τ in the temperature range from 0 to − 4 °C and in the
PO4 concentration range from 0 to 50 μmol kg− 1. The evolution of the common logarithmic ion activity product of Ca2 + and CO32 − (log (IAP)) until the onset of ikaite precipitation and the solution supersaturation at the onset of ikaite precipitation (Ω = IAP / Ksp, ikaite) under different pH, salinities (both in ASW and NaCl medium), EPZ5676 in vitro temperatures and PO4 concentrations are illustrated in Fig. 5(a–e) and Table 2. At pH from 8.5 to 10.0, the rates of log (IAP) evolution are much faster at higher pH but the
evolution curves are getting closer with the increase in pH. Ω increases with increasing pH. At salinity from 0 to 105, log (IAP) evolution shows a similar pattern in ASW and NaCl medium: that is at salinity 0, the evolution is much faster than those at salinities equal or larger than 35. And the evolution curves are getting closer with the increase in salinity. The rates in log (IAP) evolution are slower in ASW than those in the NaCl medium under the same salinity conditions. For example, at salinity 70, the time to reach ikaite solubility (ts) is 72 min in ASW while it is 65 min in the NaCl medium ( Table 2). Ω is similar in ASW in this studied salinity range; while it decreases with increasing salinity selleck chemicals llc in the NaCl medium. At temperatures from 0 to − 4 °C, the curves of log (IAP) evolution overlap as do the curves of log (IAP) evolution at PO4 concentrations from 0 to 50 μmol kg− 1. There is no significant difference in Ω in this temperature and PO4 concentration range. The smaller size of ikaite crystals in our experiments
compared to those found in natural sea ice might be due to the much faster precipitation rate under laboratory conditions, which favors calcium carbonate nucleation over further growth of crystals (Vekilov, 2010). In sea ice, the precipitation of ikaite probably goes through a much slower process, allowing the crystals to grow larger. However, the size of natural ikaite in sea ice could also be limited by the dimensions of the brine pockets or brine channels (Dieckmann et al., 2008). The different precipitates in the NaCl medium with and without PO4 indicate that the presence of PO4 is important for ikaite formation in the NaCl medium. This result is consistent with other studies stating that ikaite is usually found in an elevated PO4 environment (Buchardt et al.