Glass transition behavior in a feat humic acid and an aquatic fulvic acid

This paper presents the results of a thermal investigation of the physical and chemical properties constituting the macromolecular structure of natura l organic matter (NOM). It presents new evidence of glass transition phenom ena in a peat humic acid and a stream-derived fulvic acid as identified thr ough use of temperature-modulated differential scanning calorimetry (TMDSC) and thermal mechanical analysis (TMA). Identification of glass transition temperatures (T(g)s) in both soil- and stream-derived humic materials sugge sts a general macromolecular structure for humic and fulvic materials in NO M. Quantified T(g)s are found to be related to their elemental and chemical functional group composition, where a more aromatic peat humic acid posses ses higher glass transition temperatures than Suwannee River fulvic acid. T heory of glass transition behavior is used as a backdrop to explore the pot ential use of thermal analysis techniques for quantifying other thermodynam ic parameters of NOM, including specific heat capacity, compressibility, an d thermal expansion coefficient. Use of this information is then discussed in terms of its application to developing and verifying molecular simulatio n modeling of NOM structures.