Table 1.

Elemental ratios and compound classification characteristics of masses detected in extracted tDOM source using FT-ICR MS.

Classification	H:C range	O:C range	No. of m/z	% of Total
Lipid-like	1.5 to 2.0	0.0 to 0.3	494	9.2
Protein-like	1.5 to 2.2	0.3 to 0.67	673	12.6
Lignin-like	0.7 to 1.5	0.1 to 0.67	3049	57.1
Carbohydrate-like	1.5 to 2.4	0.67 to 1.2	143	2.7
Unsaturated Hydrocarbon-like	0.7 to 1.5	0.0 to 0.1	242	4.5
Condensed Aromatics	0.2 to 0.7	0.0 to 0.67	63	1.2
Other/unidentified	–	–	679	12.7

Molecular formulas were assigned to 96% (5343 m/z) of the 5543 m/zs detected. Data represent the classification, range of H:C and O:C molar ratios, the number of m/zs per classification, and proportion of total m/zs detected in positive ionization mode using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Classifications described in more detail in Hockaday et al. (2009).