Evaluation of pre-treatment procedures for improved interpretation of mid infrared spectra of soil organic matter

Abstract This study evaluated the effectiveness of dry ashing of soils and subsequent spectral subtraction procedure in comparison with alternative chemical methods in accentuating organics for diffuse reflectance infrared Fourier transform (DRIFT) spectroscopic analysis of soil organic matter composition. Chemical oxidation of soil with sodium hypochlorite (NaOCl) and demineralisation by hydrofluoric acid (HF) treatment were assessed as possible alternatives to the dry ashing method. Surface samples (0–10 cm) of four contrasting soils i.e., Ferralsol, Luvisol, Vertisol and Solonetz were used in the study. We observed the spectral changes before and after pre-treatments using DRIFT spectroscopy of bulk soils and their respective four separated density fractions (  2.6 g cm − 3 ). Dry ashing of soils altered the absorption bands of gibbsite and goethite in the Ferralsol; however, phyllosilicate bands in the Luvisol, Vertisol and Solonetz remained largely unaffected. The organic bands were incompletely removed by the dry ashing method and shifts in some major organic bands were also noticed. Thus the accuracy of the dry ashed spectral subtraction was limited due to the mineral and organic bands alteration. The NaOCl treatment oxidised labile organic carbon (OC) (e.g., aliphatics) without any mineral alteration, but the rest of the OC fractions remained largely unaffected. Therefore, the result of spectral subtraction of the NaOCl treated samples from original spectra was ambiguous. The HF treatment removed minerals efficiently from both bulk soils and density fractions, which noticeably highlighted the organic bands with little or no mineral interferences in the spectra of the treated samples. HF treatment also removed a small portion of the total OC that was associated with minerals. We conclude that HF treatment was more effective than dry ashing and NaOCl oxidation to accentuate organics in the soil DRIFT spectra, since it provided mineral interference free spectra with in general least affected organic bands. Thus, HF treatment of soil offers a potential pre-treatment method for improved spectroscopic characterisation of soil organic matter.

[1]  H. Gerke,et al.  Chapter Three – Characterization of Organic Matter Composition of Soil and Flow Path Surfaces Based on Physicochemical Principles—A Review , 2013 .

[2]  N. Comerford,et al.  Aggregation and Aggregate Carbon in a Forested Southeastern Coastal Plain Spodosol , 2007 .

[3]  H. Collins,et al.  Chemical Differences in Soil Organic Matter Fractions Determined by Diffuse‐Reflectance Mid‐Infrared Spectroscopy , 2011 .

[4]  M. Kleber,et al.  Stabilization of Soil Organic Matter: Association with Minerals or Chemical Recalcitrance? , 2006 .

[5]  S. Sohi,et al.  The chemical composition of measurable soil organic matter pools , 2005 .

[6]  C. Johnson,et al.  Applicability of solid-state 13C CP/MAS NMR analysis in Spodosols: chemical removal of magnetic materials , 1999 .

[7]  K. Shepherd,et al.  Generic Prediction of Soil Organic Carbon in Alfisols Using Diffuse Reflectance Fourier-Transform Mid-Infrared Spectroscopy , 2011 .

[8]  Zhihong Xu,et al.  Hydrofluoric acid pre-treatment for improving 13C CPMAS NMR spectral quality of forest soils in south-east Queensland, Australia , 2002 .

[9]  Keith D. Shepherd,et al.  The prediction of soil carbon fractions using mid-infrared-partial least square analysis , 2007 .

[10]  J. Lehmann,et al.  Organic Carbon Chemistry in Soils Observed by Synchrotron-Based Spectroscopy , 2010 .

[11]  Keith W. Goyne,et al.  Soil Chemical Insights Provided through Vibrational Spectroscopy , 2014 .

[12]  Abad Chabbi,et al.  Stabilisation of HF soluble and HCl resistant organic matter in sloping tropical soils under slash and burn agriculture , 2008 .

[13]  T. Müller,et al.  Use of specific peaks obtained by diffuse reflectance Fourier transform mid‐infrared spectroscopy to study the composition of organic matter in a Haplic Chernozem , 2012 .

[14]  P. Sollins,et al.  Sequential density fractionation across soils of contrasting mineralogy: evidence for both microbial- and mineral-controlled soil organic matter stabilization , 2009 .

[15]  G. Cadisch,et al.  Combining a coupled FTIR-EGA system and in situ DRIFTS for studying soil organic matter in arable soils , 2012 .

[16]  P. Leinweber,et al.  Shifts in soil organic matter composition following treatment with sodium hypochlorite and hydrofluoric acid , 2009 .

[17]  J. Skjemstad,et al.  The removal of magnetic materials from surface soils , 1994 .

[18]  Paul N. Nelson,et al.  Soil organic matter , 2000 .

[19]  A. Francez,et al.  FTIR spectroscopy can be used as a screening tool for organic matter quality in regenerating cutover peatlands , 2008 .

[20]  J. M. Soriano-Disla,et al.  Total Petroleum Hydrocarbon Concentration Prediction in Soils Using Diffuse Reflectance Infrared Spectroscopy , 2013 .

[21]  R. McDowell,et al.  Influence of soil constituents on soil phosphorus sorption and desorption , 2001 .

[22]  R. Schneider,et al.  Effects of organic and inorganic amendments on soil organic matter properties , 2009 .

[23]  J. Fuhrer,et al.  Sodium hypochlorite separates an older soil organic matter fraction than acid hydrolysis , 2007 .

[24]  B. Sreedhar,et al.  In situ FTIR study on the dehydration of natural goethite , 2006 .

[25]  B. Chefetz,et al.  Dissolved organic carbon fractions formed during composting of municipal solid waste : Properties and significance , 1998 .

[26]  I. Kögel‐Knabner,et al.  Stabilization of organic matter by soil minerals — investigations of density and particle‐size fractions from two acid forest soils , 2002 .

[27]  J. Madejová,et al.  FTIR techniques in clay mineral studies , 2003 .

[28]  M. Egli,et al.  Soil organic matter formation along a chronosequence in the Morteratsch proglacial area (Upper Engadine, Switzerland). , 2010 .

[29]  W. Haeberli,et al.  Comparison of different methods of obtaining a resilient organic matter fraction in Alpine soils , 2008 .

[30]  R. Conant,et al.  Diffuse-Reflectance Fourier-Transform Mid-Infrared Spectroscopy as a Method of Characterizing Changes in Soil Organic Matter , 2013 .

[31]  H. Gerke,et al.  Interpretation of infrared spectra for OM characterization of soil structural surfaces of Bt‐horizons , 2016 .

[32]  R. Spaccini,et al.  Molecular characterization of compost at increasing stages of maturity. 1. Chemical fractionation and infrared spectroscopy. , 2007, Journal of agricultural and food chemistry.

[33]  K. Reddy,et al.  Biogeochemistry of Wetlands , 2011 .

[34]  R. Bol,et al.  Molecular dynamics of organic matter in a cultivated soil. , 2002 .

[35]  J. Reeves.  Mid-infrared spectral interpretation of soils: Is it practical or accurate? , 2012 .

[36]  Sanjai J. Parikh,et al.  Soil organic matter functional group composition in relation to organic carbon, nitrogen, and phosphorus fractions in organically managed tomato fields , 2015 .

[37]  M. Kleber,et al.  Review: organic matter removal from soils using hydrogen peroxide, sodium hypochlorite, and disodium peroxodisulfate , 2005 .

[38]  M. Kleber,et al.  Sodium hypochlorite oxidation reduces soil organic matter concentrations without affecting inorganic soil constituents , 2005 .

[39]  I. Kögel‐Knabner,et al.  Alteration of soil organic matter following treatment with hydrofluoric acid (HF) , 2006 .

[40]  H. Knicker,et al.  Organic matter in constructed soils from a coal mining area in southern Brazil , 2006 .

[41]  I. Kögel‐Knabner,et al.  Improvement of 13C and 15N CPMAS NMR spectra of bulk soils, particle size fractions and organic material by treatment with 10% hydrofluoric acid , 1997 .

[42]  R. Lal,et al.  Soil Carbon Sequestration Impacts on Global Climate Change and Food Security , 2004, Science.

[43]  R. Ellerbrock,et al.  Soil organic matter characterization of temperate peatland soil with FTIR‐spectroscopy: effects of mire type and drainage intensity , 2015 .

[44]  T. Nguyen,et al.  Diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy in soil studies , 1991 .

[45]  Balwant Singh,et al.  Organo-mineral interactions in contrasting soils under natural vegetation , 2014, Front. Environ. Sci..

[46]  G. Gee,et al.  Particle-size Analysis , 2018, SSSA Book Series.

[47]  Xueming Yang.  An extension to ``Mid-infrared spectral interpretation of soils: Is it practical or accurate?'' , 2014 .

[48]  P. Leinweber,et al.  Differential thermal analysis, thermogravimetry and pyrolysis-field ionisation mass spectrometry of soil organic matter in particle-size fractions and bulk soil samples , 1992 .

[49]  R. Frost,et al.  Infrared spectroscopy of goethite dehydroxylation: III. FT-IR microscopy of in situ study of the thermal transformation of goethite to hematite. , 2002, Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy.

[50]  Ena Smidt,et al.  The applicability of Fourier transform infrared (FT-IR) spectroscopy in waste management. , 2007, Waste management.

[51]  R. Frost,et al.  The behavior of hydroxyl units of synthetic goethite and its dehydroxylated product hematite. , 2001, Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy.

[52]  A. Mentler,et al.  FTIR‐spectroscopic characterization of humic acids and humin fractions obtained by advanced NaOH, Na4P2O7, and Na2CO3 extraction procedures , 2007 .

[53]  J. U. Anderson.  An Improved Pretreatment for Mineralogical Analysis of Samples Containing Organic Matter1 , 1961 .

[54]  I. Kögel‐Knabner,et al.  The effect of 10% HF treatment on the resolution of CPMAS 13C NMR spectra and on the quality of organic matter in Ferralsols , 2003 .

[55]  P. Sollins,et al.  Organic C and N stabilization in a forest soil: Evidence from sequential density fractionation , 2006 .

[56]  H. Gerke,et al.  Long‐term effects of crop rotation and fertilization on soil organic matter composition , 2007 .

[57]  I. Kögel‐Knabner,et al.  Composition and radiocarbon age of HF-resistant soil organic matter in a Podzol and a Cambisol , 2007 .