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Age and origin of the source material determine the chemical structure of humic substances. In general, humic substances derived from soil and peat (which takes hundreds to thousands of years to form) have higher molecular weight, higher amounts of O and N, more carbohydrate units, and fewer polyaromatic units than humic substances derived from ...
Vertisols of the world A more detailed map of the global distribution of Vertisols. A vertisol is a Soil Order in the USDA soil taxonomy [1] and a Reference Soil Group in the World Reference Base for Soil Resources (WRB). [2] It is also defined in many other soil classification systems. In the Australian Soil Classification it is called ...
The name was coined in 1899 by Leon Marchlewski, who first purified the compound and studied some of its chemical properties. [7] F. E. Withers and F. E. Caruth first attributed the toxic properties of the cotton seed (known since the 19th c.) to gossypol in 1915, [8] and its chemical formula was established in 1927 by Earl Perry Clark (1892 ...
Due to the physical and chemical properties of some clays [4] (such as the Lias Group) large swelling occurs when water is absorbed. Conversely when the water dries up these clays contract (shrink). The presence of these clay minerals is what allows soils to have the capacity to shrink and swell.
Argillipedoturbation, sometimes referred to as self-mulching, is a process of soil mixing caused by the shrinking and swelling of the smectite clays contained in soil. [1] [2] It is an effect specific to soils of the vertisolic variety, and is triggered by the constant cycles of wetting and drying [1] It is characterized by wide (up to 2 centimetres (0.79 in)), deep (50 centimetres (20 in) or ...
Geosmin (/ dʒ i ˈ ɒ z m ɪ n / jee-OZ-min) is an irregular sesquiterpenoid with a distinct earthy or musty odor, which most people can easily smell. The geosmin odor detection threshold in humans is very low, ranging from 0.006 to 0.01 micrograms per liter in water. [1]
Mollisols of the world Mollisols are generally associated with the steppe biome. Mollisol is a soil type which has deep, high organic matter, nutrient-enriched surface soil (), typically between 60 and 80 cm (24-31 in) in depth.
[8] [9] [10] Its structure was established through analysis using nuclear magnetic resonance at Tohoku University, Harvard University and the University of Tokyo in combination with mass spectrometry, and synthetic chemical methods.