A Thermogravimetric Study of Organic Matter of Representative Canadian Podzol Soils

Abstract

Differential thermogravimetric (DTG) curves of untreared peat, muck, and 10 different Podzol L-H materials showed peaks ac approximately 100" C (moisture), 280' (low-temperature band), and'170 to 390'' C thigh-t"-perarure band). The maxima at 2-80' C wcre sharp and clraracterisric-of all^surface materials investigated. The DTG curves lr'ere essentially rhe same for all of the Podzol L-fimaterials investiEated.The DTG curves for 12 orean-ic matter DreDarations exffacted from Podzol Bh, Bfh, Bhf, Bfl, and Btf hoiizons showed maxima at 100' C arrd in the 420 to 520'C region (high-temperarure band). The peaks at 280" C were virtually absent in thEse matirials. This suggcsted differences in composition between [-H and B horizon orsanic mattei-of the Podzols srudied. The variations in the positions of the hig-h-temperature bands of the B materiais were related to the nrorphological characteristics of these soils in the 6eld. From this it appeared that thermogravimetry might be a useful aid in soil classification.Addition of inorganic materials did not affect the position of the low-temperature bands but had a pronounced effect on the high-temperature bands of both L-H and B organic matter. Addition of Na caus6d the ieaks of the latter to shift to hiqher iemperatures rvhile addition of Al and Fi car:sed shifts to lou'er temperitures, INTRODUCTIOIIIn previous publications (3, 5), DTG (differential thermogravime ric) curves for organic matter originating from the I-H and Bh hdrizons of a Podzol were presented. The Jurves 5f ttte rwo materials were quite different.Above 100' C, where water was lost. the L-H material sliowed two distinct bands, a rather broad one with maximum at 280' C and a narrower one with a peak at 5200 C. The DTG curve of the Bh material, on tl-re other hand, yielded only one distinct peak at +2o" .C. The latter material shou'ed a slorv but more oi less constant iate of weighr loss berween l25o and 350" C.The distinct difference found between the DTG curves of the L-H and Bh organic matter of a single Podzol profilc raised the quesrion whether ol not this w-as characteristic of Fodzols in seneral. With this in mind. a studv was made of the thermogravimetry of i-H and B horizon organic matter of Podzols from 10 different sites'. For comparative purposes, one sample each of peat, muck, and lignite u'as included in the survey. APPARATUS A Stanton recording thermobalance of 0.1 mg sensitiviry was used and the samples were held in platinum crucibles. f constant rate of heating (5.5' Czmin) was maintained. Thermogravimetric (TG) curves were obtained by replotting thermogravirnetric iata as weight loss'(Y-axis) vs. temperature (X-axi:). ftle weight change per 2.5 minute inteffal as obtained by simple difference was plotted vs. temperature to give differential thermogravimetric (DTG) curves.

Long term change in chemical properties of preindustrial charcoal particles aged in forest and agricultural temperate soil

“…This suggests that, with cultivation, the O-rich fraction of charcoal gets saturated with Ca 2+ from liming, which catalyzes its combustion during DSC analysis. A comparable decrease in thermal stability related to the content of Fe 3+ and Al 3+ was reported for the humic fraction of podzol soil (Schnitzer et al, 1964). Over time of cultivation, the O-rich, less thermally stable fraction of charcoal decreases (Fig.…”

Application of thermal analysis techniques in soil science

“…During the 1960s, Turner and Schnitzer (1962), Schnitzer et al (1964) and Schnitzer and Hoffman (1965) pioneered the use of TG, in combination with other techniques such as infrared spectroscopy and elemental analysis, for studying podzolic soil humic substances. They detected two exothermic peaks between 200 and 500°C for all samples.…”

Changes in clay-associated organic matter quality in a C depletion sequence as measured by differential thermal analyses

“…Early studies by Schnitzer and colleagues (Turner and Schnitzer, 1962;Schnitzer et al, 1964) used thermogravimetry (TG) and derivative thermogravimetry (DTG) to examine the thermal nature of soil organic matter in podzols. Further studies have added chemical techniques to characterizing soil fractions or humic substances.…”