MOLECULAR WEIGHT COMPOSITION OF HUMIC ACIDS IN URBAN SOILS (THE NORTHERN ADMINISTRATIVE DISTRICT OF MOSCOW CITY TAKEN AS AN EXAMPLE)
2019
A. I. Filatova | V. G. Mamontov | P. Yu. Panova
The article provides research results and comparative analysis of humic acids in sod-podzolic soil of the Experimental Forest of the Russian State Agrarian University (protected area) and urban soils located in the Timiryazev district of Moscow. Humic acids of the zonal sod-podzolic soil of the Experimental Forest include four fractions with varying molecular weight: the 1st fraction – ≥ 23 440 unified atomic mass units (amu), the 2nd one – 13 340 amu, the 3rd one – 5 500 amu and the 4th one – 2 460 amu. The fraction with a molecular weight of 5 500 amu and a relative content of 38 % dominates among them, while the share of low-molecular fractions (< 20 000 amu) accounts for 70 % of the total mass of humic acids. When weight-average molecular mass of humic acids is 17 530 amu, the average molecular mass of the low-molecular fractions is 9 960 amu. Humic acids of urbanozems differ in molecular weight composition from humic acids of sod-podzolic soil. In most cases it consists of 5–6, less commonly of 3, fractions with molecular weight from 1 780 to ≥ 23 440 amu. The share of medium- and high-molecular fractions fluctuates from 31–37 % to 47–50 % of the total mass of humic acids. The characteristic feature of humic acids of urbanozems is the presence in their composition of low-molecular fractions with such molecular weights, which are not found in humic acids of sod-podzolic soil. Thus, humic acids of urbanozems are characterized by higher weight-average molecular mass ranging from 17 680 to 19 980 amu, as well as by higher weigh-average molecular mass of the low-molecular fractions which vary from 10 680 to 13 650 amu.
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