Element Composition Of Peat Deposits In Flat Frost Mound Bogs Of The Pyakupur River (northern Taiga Of West Siberia)
Abstract
A. G. Lim, S. V. Loiko, T. V. Raudina, I. I. Volkova, V. P. Seredina
The content and the profile distribution of the element composition of the 1 meter high peat deposits in flat frost mound bogs are investigated. The botanical composition of peat is described. The results of the botanical composition analysis of peat showed that deposits consist mainly of sphagnum mosses, lichens, shrubs, green mosses, pine wood, as well as pine and birch bark. A good correlation between the degree of peat decomposition and the brightness of dry peat measured by the CIE L*a*b* color model is revealed. As a result of the study of peat samples’ color, it has been found that this parameter can be used as an express method for the rapid assessment of peat degree decomposition. The highest concentration of the organic carbon occurs at the base of the peat deposit (64.4±0.2%). The nitrogen concentration in permafrost peat is higher than in thawed (1.0 ± 0.2% and 0.7 ± 0.1%, respectively, the difference is significant at p = 0.001). The C / N ratio decreases from 72 ± 16 in 0-40 cm in the thawed layer to 50 ± 10 in the frozen part (40-100 cm). Within the bottom low boundary of the seasonally thawed layer, a local increase in the N concentration was detected, as well as an almost 2-fold decrease in the C/N ratio. It is most likely related to the high increase in the rate of microbial activity on the border between the thawed layer and the permafrost peat. It was revealed that most of the elements are concentrated in the upper (thawed) part of the peat deposit. Among them, only Na, Mg, Ca, Zn, Ba, As and Sb have a significant difference. Despite the fact that significant differences according to non-parametric U-criterion Mann-Whitney test were identified only for 7 elements, the distribution of the rest along elements the frozen and thawed peat layer is similar in nature. So for Na, Mg, Al, P, K, Ca, Ti, Fe, Zn, Ba, Li, B, V, Cr, Mn, Co, Ni, Cu, Ga, As, Rb, Sr, Y, Zr, Nb, Mo, Cd, Sb, Cs, the upper quartiles of concentrations in the seasonally thawed layer are 1.2 - 6.9 times higher than in the permafrost peat, and for C, N, Al, Ba, B, V, Co, Cu , Zr, Nb, Mo it is 1,0 - 0,6 times lower, respectively. Generally, according to the element composition, it is safe to say that the differences stem from the botanical composition. In general, according to the elemental composition it can be said that the differences are primarily due to the botanical composition. The active layer comprises mainly sphagnum mosses and lichens, the woody peat already appears in the lower permafrost part of the deposit. A correlation between the brightness of peat and the total content of ash elements (R2 = 0.65, excluding 1 sample) was revealed within the active layer. Taking into account the fact that the brightness correlates with the degree of decomposition, it may be concluded that higher upper quartile of the concentrations of elements in the active layer relates to the slower peat accumulation rate for the last 3 thousand years and, correspondingly, a large accumulation of dust components from the atmosphere by the peat layers.<