Sampling Protocols for Frozen Soils.

The assessment of frozen soils with substantial water contents requires special sampling procedures and quantification techniques. In most permafrost-affected soils (i.e., Gelisols), cryoturbation in the active layer distorts and ruptures most subsurface horizons, such that these horizons must be carefully marked and delineated on a diagram to determine where samples can be taken and to assess volumetric contents of components such as carbon. In order to calculate the content of such components in a pedon, two methods are recommended: 1) determine relative proportion of each horizon in relation to the whole profile area, and 2) translate the relative proportion into a flat profile and use the thickness range to calculate the elemental distribution. High water contents present as ice tend to firmly cement frozen layers and turn samples to mud slurry when thawed after excavation, which renders standard means of sample collection ineffective. Bulk samples must be securely sealed to ensure proper sample recovery.  For the measure of bulk density, saran-coated clod method or known volume insertions core can be used in the unfrozen active layer. However, for the frozen soils and the permafrost layer, saran-coated clods with ice thaw into mud quickly and are useless for further measurement. Thus for frozen soils or permafrost with few coarse fragments, bulk density is measured by drilling cores. In frozen soils with rock fragments, the recommended method is to carve blocks of frozen materials and measure the dimensions. Coarse fragment content can be corrected by displacement/weight measurement in the lab.