Laboratory study on coprecipitation of phosphate with ikaite in sea ice

摘要

Ikaite (CaCO3�6H2O) has recently been discovered in sea ice, providing first direct evidence ofudCaCO3 precipitation in sea ice. However, the impact of ikaite precipitation on phosphate (PO4) concentrationudhas not been considered so far. Experiments were set up at pH from 8.5 to 10.0, salinities from 0 to 105,udtemperatures from 24°C to 0°C, and PO4 concentrations from 5 to 50 mmol kg-1 in artificial sea ice brine soudas to understand how ikaite precipitation affects the PO4 concentration in sea ice under different conditions.udOur results show that PO4 is coprecipitated with ikaite under all experimental conditions. The amount ofudPO4 removed by ikaite precipitation increases with increasing pH. Changes in salinity (S >=35) as well as temperatureudhave little impact on PO4 removal by ikaite precipitation. The initial PO4 concentration affects theudPO4 coprecipitation. These findings may shed some light on the observed variability of PO4 concentration inudsea ice.