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Purpose: This exploratory study evaluates the potential of Nanothermal analysis (NTA) coupled with Atomic force microscopy (AFM) of soil samples for understanding physicochemical processes in soil and for linking nanospatial and microspatial distribution of thermal characteristics with macroscopic properties of soil samples. Materials and Methods: Soil and reference samples were investigated by Differential scanning calorimetry and AFM-NTA. NTA was conducted on 16 points of each ...Purpose: This exploratory study evaluates the potential of Nanothermal analysis (NTA) coupled with Atomic force microscopy (AFM) of soil samples for understanding physicochemical processes in soil and for linking nanospatial and microspatial distribution of thermal characteristics with macroscopic properties of soil samples. Materials and Methods: Soil and reference samples were investigated by Differential scanning calorimetry and AFM-NTA. NTA was conducted on 16 points of each AFM image in two subsequent heating cycles (55-120O C and 55-300O C, respectively). Thermograms were subdivided into characteristic types, and their spatial distribution was compared between sample replicates and materials. Results and Discussion. Thermogram types consisted of partly structured expansion and compression phases suggesting material-specific thermal profiles. The distribution of curve types reflected sample-dependent nanoscale and microscale heterogeneity. Indications for water molecule bridge (WAMB) transitions were found by NTA in peat and soil. Organic materials generally revealed strong expansion and irreversible compression phases, latter probably due to collapse of pore and aggregate structures. In contrast to charcoal and manure, peat shows strong expansion below 120O C and compression only above 120O C. Conclusions: All investigated samples are heterogeneous on the nanoscale and microscale with respect to thermal behaviour. AFM-nanothermal analysis allows distinguishing numerous different materials on nanometer and micrometer scale in soil samples. The material-dependent characteristics will help to understand and learn more about the nanoscale distribution of different materials and properties. Related to the macroscopic thermal behavior, this will allow studying links between properties of biogeochemical interfaces and processes governed by them.» weiterlesen» einklappen

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