ALTERATION OF CALCITE SAMPLES IN THE ARCTIC ENVIRONMENT (SPITSBERGEN) OBSERVED IN ATOMIC FORCE MICROSCOPY

This study addresses chemical weathering and biological activity on mineral surfaces in the newly forming arctic soil of Spitsbergen. Chemical weathering and soil forming processes associated with glaciers affects several geochemical cycles, including the global carbon cycle, and as a result contribute to changes of the global climate. The study areas are located in the foreland of the Werenskiold Glacier (continuously retreating by several meters a year) and the slopes of nearby Mount Torbjörnsenfiellet. Several samples of freshly cleaved calcite were buried on the arctic soil in six different locations throughout the study areas. The calcite samples were placed at elevations ranging from 1 m amsl and 590 m amsl (the highest on the slope of Mt.Torbjörnsenfiellet), and at distances varying from 10 m to 3000 m from the Greenland Sea. The calcite samples were retrieved after one and three years, and were analyzed using an Atomic Force Microscope (AFM), with the lengths of the AFM images ranging from 325 to 5000 nm. The retrieved samples were compared with a control sample that 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 rounded edges with irregular surfaces, which feature numerous dissolution features and rounded pitches associated with bacterial activities. The observations suggest that the retrieved calcite samples undergo rapid chemical and biological weathering when exposed to the relatively unsaturated, with respect to calcite, glacial meltwaters. The magnitude of the changes on mineral surfaces reflects the temperature and moisture conditions which affect both the thermodynamic equilibrium and reaction kinetics. Typically upper edges of mineral steps are altered more than lower edges, and lower temperature environments result in more pronounces changes.