WEATHERING PATTERNS AND DISSOLUTION RATES OF CALCITE BURIED IN ARCTIC SOILS ON SPITSBERGEN – AFM AND SEM STUDY

This study presents the results of Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) imaging of calcite sample surfaces after they have been buried for one year and three years respectively, in the arctic soil of Spitsbergen. The objective of the study was to determine the pattern of calcite surface alterations and to compare the effects of various environments. Six samples of freshly cleaved calcite were buried in three different environments. Environmental effects include varying elevations (ranging from 1 to 590 m amsl), distances from the Greenland Sea (from 10 m to 3000 m), and distances from the Werenskiold Glacier (from 100 to 3500 m). The retrieved samples were analyzed using AFM and SEM and compared with a control sample that was freshly cleaved and has never been exposed to an arctic environment. The control sample is characterized by sharp step edges and smooth surfaces. Overall, all of the calcite samples recovered from Spitsbergen have more irregular surfaces with rounded edges. The development of numerous intersecting, both isometric and elongated, etch pits is common. Distribution of etch pits is heterogeneous with some areas being less affected. Typically top step surfaces are altered more than bottom step surfaces. Rhombohedral weathering patterns are present on many surfaces and are more dominant in samples retrieved after three years. Calcite surfaces are covered locally by biofilms. The most prominent dissolution features (advanced weathering) were observed in the sample located at the Greenland Sea shore characterized by the longest contact time with water, higher moisture air masses, and soils with more active microbial activity . The dissolution rates varied between 1.25E-08 mol/cm² /yr to 5.97E-07 mol/cm²/yr. Annual dissolution rates were higher in all samples retrieved after 3 years than in samples retrieved 1 year. The average annual dissolution rate increased by 202% for samples retrieved after 3 years as compared to samples retrieved after 1 year. This dissolution rate increase can result from a larger calcite surfaces areas exposed to chemical reactions in all samples but there might also be additional regional factor (such as regional weather or climate pattern) that has influenced the dissolution rate for all samples.