Spectral assessment of soil properties : standoff quantification of soil organic matter content in surface mineral soils and Alaskan peat

Abstract

Characterization of soil properties typically requires time-intensive, ground-based sampling. Therefore, technologies that allow for rapid assessment of particular attributes would be greatly beneficial. One example is Fourier transform infrared (FTIR) spectroscopy, which uses an infrared spectrum to qualitatively identify a variety of compounds in solid, liquid, or gaseous samples. This study investigated the infrared reflectance signatures of peat and mineral soil samples with varying amounts of organic matter and coupled FTIR spectroscopy with a thermogravimetric analyzer (TGA) to more accurately identify and quantify soil organic matter (SOM). Clear differences were observed between the soil and peat FTIR spectral profiles. When compared to traditional analysis by loss on ignition, the coupled TGA-FTIR method resulted in an underestimation of the percent SOM for peat samples and an overestimation of the percent SOM in mineral soil samples. These results may have been influenced by low sample mass and moisture present in the sample. In total, our project results show that FTIR measurements provide a rapid yet qualitative means of assessing sample organic matter versus mineral content, but the TGA-FTIR measurement capability needs more refinement before it can be used for qualitative SOM measurements.