Table 2 Biomolecular markers for class differentiation between the three regions (Scotland, North West England and North East England) and each site (SOM, SAP, SRC, SLM, ESA, ESB and EDB). Spectral markers were found by investigating the difference-between-mean support vectors spectra found by SVM, and linked to the biomolecules associated with each wavenumber from published literature

NEE and NW

1736

C=O stretching [lipids]

[65]

1643

C=O stretching [Amide I]

[65]

1605

v_as (COO⁻) [polysaccharides, pectin]

[65]

1546

Amide II: [protein N–H bending, C–N stretching], α-helical structure

[89]

1466

CH₂ bending in lipid

[50]

1446

aromatic ring stretch vibrations, tannins

[61]

1405

CH₃ asymmetric deformation

[65]

1385

Ring stretching vibrations mixed strongly with CH in-plane bending

[65]

1158

vC-O of proteins and carbohydrates

[65]

1034

C-O stretch, tannins

[61]

1015

ν (CO), ν (CC), δ (OCH), ring in pectin

[50]

964

C-O deoxyribose, C-C

[65]

NEE and WS

1725

C=O stretching band mode of the fatty acid ester

[65]

1662

Amide I, or fatty acid esters

[65]

1648

Amide I

[65]

1608

aromatic ring stretch vibrations, tannins

[61]

1586

Amide II

[65]

1542

Amide II

[90]

1531

Amide II

[91]

1446

aromatic ring stretch vibrations, tannins

[61]

1530

C=N adenine, cytosine

[65]

1014

phosphodiester stretching bands [symmetrical and asymmetrical]

[65]

NWE and WS

1725

C=O stretching band mode of the fatty acid ester

[65]

1678

Stretching C=O vibrations that are H-bonded [changes in the C=O stretching vibrations could be connected with destruction of old H-bonds and creation of the new ones]

[65]

1662

Amide I, or fatty acid esters

[65]

1445

lipids

[63]

1397

CH₃ symmetric deformation

[65]

SRC and others

1748

C=O stretching vibration of alkyl ester, pectin

[62]

1728

ν (C=O) ester, cutin

[62]

1678

Stretching C=O vibrations that are H-bonded [changes in the C55O stretching vibrations could be connected with destruction of old H-bonds and creation of the new ones]

[65]

1651

phenolic compounds/ cutan [aromatic and C=C functional groups]

[62]

1608

aromatic ring stretch vibrations, tannins

[61]

1542

Amide II

[90]

1455

C-O-H

[65]

1443

δ (CH₂) [lipids, fatty acids], or δ(CH) [polysaccharides, pectin]

[65]

SLM and others

1755

lipid

[51]

1735

C=O stretching, the phenolic compound ellagic acid/ the secondary metabolite quercetin

[63]

1512

ν (C-C) aromatic (conjugated with C=C phenolic compounds

[62]

1481

symmetric deformation NH₂ ⁺, glyphosate^X

[60]

1466

CH₂ bending in lipid

[50]

SOM and others

1755

lipid

[51]

1736

lipids

[63]

1481

symmetric deformation NH₂ ⁺, glyphosate^X

[60]

1466

CH₂ bending in lipid

[50]

1161

carbohydrate; stretching vibrations of hydrogen-bonding C–OH groups (found in serine, threonine and tyrosine residues of cellular proteins); cellulose

[51]

1103

ν(C–O–C) in ester

[50]

SAP and others

1755

lipid

[51]

1736

lipid

[63]

1481

symmetric deformation NH₂ ⁺, glyphosate^X

[60]

1466

CH₂ bending in lipid

[50]

1103

ν(C–O–C) in ester

[50]

ESA and others

1755

lipid

[51]

1732

lipid; fatty acid esters; hemicellulose

[51]

1647

amide I; pectin

[51]

1512

ν(C=C) in lignin, carotenoid or protein

[50]

1481

symmetric deformation NH₂ ⁺, glyphosate^X

[60]

1466

aromatic ring stretch vibrations, tannins

[61]

ESB and others

1755

lipid

[51]

1736

C=O stretching [lipids]

[65]

1481

symmetric deformation NH₂ ⁺, glyphosate^X

[60]

1466

CH₂ bending in lipid, or aromatic ring stretch vibrations, tannins

[50, 61]

EDB and others

1728

ν (C=O) ester, cutin

[62]

1446

aromatic ring stretch vibrations, tannins

[61]

1408

CH₃ deformation, ν_s (COO⁻) in pectin

[50]