Aggregate Composition as Related to the Distribution of Different Forms of Carbon in Soils of Rostov Agglomeration

摘要

The aim of this work was to study the transformation of soil structure in the course of urban pedogenesis and to assess the relationship between the size of aggregates and the content of carbon of organic matter and of carbonates. We analyzed soils of Rostov agglomeration and compared the composition of aggregates in Calcic Chernozems and urbostratozems on buried chernozems (Urbic Technosols). We determined the aggregate composition by the Savvinov method and the carbon content on a TOC-L CPN Shimadzu spectrometer. Differences in the composition of aggregates of various genetic horizons were revealed by the Student criterion and the graphical analysis of the dependence of the percentage of structural fractions on the content of organic and inorganic carbon, smoothed by the least square method. It was found that the portion of air-dry fraction >10 mm in the urbic and buried horizons increased reliably by 30% or more as a result of a decrease in the portion of fractions 7-0.5 mm. Significant differences in the content of water-resistant fractions were observed only in the AU-[AU] pair horizons: the fraction of water-stable aggregates >3 and 2-1 mm decreased, and the contribution of aggregates 0.5-0.25 mm increased significantly in the buried horizon. This was probably related to the pre-burial urban dispersion of soil structure. The distribution of aggregates by fractions was not related to the content of organic and inorganic carbon. However, there were values of these kinds of carbon for each structural fraction, in which the intensity of structure formation decreased. It was manifested in a sharp decrease in the content of the fraction in the buried profiles relative to native ones.