The use of mid-infrared diffuse reflectance spectroscopy for acid sulfate soil analysis

José M Soriano-Disla; Leslie J Janik; Sean T Forrester; Sonia F Grocke; Robert W Fitzpatrick; Michael J McLaughlin

doi:10.1016/j.scitotenv.2018.07.383

The use of mid-infrared diffuse reflectance spectroscopy for acid sulfate soil analysis

Sci Total Environ. 2019 Jan 1:646:1489-1502. doi: 10.1016/j.scitotenv.2018.07.383. Epub 2018 Jul 29.

Authors

José M Soriano-Disla¹, Leslie J Janik², Sean T Forrester³, Sonia F Grocke³, Robert W Fitzpatrick⁴, Michael J McLaughlin⁵

Affiliations

¹ Sustainable Use, Management and Reclamation of Soil and Water Research Group (GARSA), Universidad Politécnica de Cartagena, Paseo Alfonso XIII 48, 30203 Cartagena, Spain.
² CSIRO Environmental Contaminant Mitigation and Technologies Program, CSIRO Land and Water, Waite Campus, Waite Road, Urrbrae 5064, South Australia, Australia; School of Agriculture, Food and Wine, University of Adelaide, Waite Campus, Waite Road, Urrbrae 5064, South Australia, Australia. Electronic address: Les.Janik@csiro.au.
³ CSIRO Environmental Contaminant Mitigation and Technologies Program, CSIRO Land and Water, Waite Campus, Waite Road, Urrbrae 5064, South Australia, Australia.
⁴ Acid Sulfate Soils Centre (ASSC), The University of Adelaide, South Australia 5005, Australia.
⁵ School of Agriculture, Food and Wine, University of Adelaide, Waite Campus, Waite Road, Urrbrae 5064, South Australia, Australia.

PMID: 30235634
DOI: 10.1016/j.scitotenv.2018.07.383

Abstract

Good management of sulfide minerals and sulfuric acid in Acid Sulfate Soils (ASS) requires cost-effective rapid analytical data for their characterisation. However, the determination of properties in ASS samples using traditional laboratory techniques is expensive and time consuming. Excessive delays in analysis risks sample changes from oxidation. Mid-infrared (MIR) spectroscopy with multivariate regression offers a quicker and cheaper surrogate. This manuscript reports the prediction of some of the following key soil parameters in ASS characterisation using benchtop (Perkin Elmer) and handheld (ExoScan) diffuse reflectance MIR Fourier transform (DRIFT) spectrometers: Total Organic Carbon (TOC), Titratable Actual Acidity (TAA), Extractable Sulfate Sulfur (ESS), Reduced Inorganic Sulfur (RIS), Retained Acidity (RA), Acid Neutralising Capacity (ANC), and Lime Calculation (LC). Three sets of representative ASS soil profiles, comprising 132 samples from hyposulfidic, hypersulfidic and sulfuric materials, and covering a wide range of environments in South Australia were scanned under laboratory conditions. These were combined with reference laboratory data in partial least squares regression (PLSR) calibration models. The calibrations were validated by leave-one-out cross validation, with a further test set available for validation. Predictions with coefficient of determination (R²) > 0.75, were obtained for TOC (0.95), TAA (0.88), RIS (0.86), LC (0.76) and ANC (0.76), but models for ESS (0.66) and RA (0.41) were less satisfactory. The handheld spectrometer performed similarly to the benchtop spectrometer in terms of PLSR prediction accuracies with the potential for in-field sampling. Results thus confirmed the possibility of using MIR spectroscopy for the rapid and cost-effective characterisation of ASS.

Keywords: Acid sulfate soils; Attenuated total reflectance; Diffuse reflectance; Mid-infrared; Partial least squares regression; Pyrite.