IN-SITU INVESTIGATION OF SOIL ORGANIC-MATTER AGGREGATES USING INFRARED MICROSCOPY

Infrared (IR) microscopy in combination with X-ray microdiffraction wa s used as a direct (in situ) method to study the nature of organic (an d mineral) components within the organic aggregates from four Chernoze mic and one Podzolic-like soils from Alberta. These methods utilized t hin section peels or individual aggregates and have the capability of point analysis in area of about 50-100 mu m in diameter. We compared t he conventional IR spectra of soil organic matter [humic acids (HA)] w ith those of in situ IR spectra obtained directly from aggregates. Res ults showed that the band at 1720 cm(-1) observed in humic acid was no t present in the in situ IR spectra and instead the bands at 1735 and 1785 cm(-1) correlated to esters were observed. This indicates that sa ponification of esters occurred during the alkaline extraction of humi c acid. In situ IR spectra from an unimpregnated sample also showed a strong band around 1524 cm(-1) (correlated to amide II). X-ray microdi ffraction analysis showed the presence of quartz and phyllosilicates i n the aggregates. The method described in this study appeared to be su ited to the direct investigation of soil organic matter and may provid e the methodology necessary to assess the quality of organic matter.