Molecular Signatures of Humic Acids from Different Sources as Revealed by Ultrahigh Resolution Mass Spectrometry

Table 1

Molecular parameters of (a) humic acids from Jiufeng forest soil, (b) humic acids from Suwannee River, and (c) humic acids from leonardite derived from assigned molecular formulas^a.

Sample	Cwa	Hwa	Owa	Nwa	Swa	m/zwa	H/Cwa	O/Cwa	DBEwa	AI-modwa	MLBL%^b	CRAM%^c	NOSC
JFHA	21.63	34.60	4.62	0.04	0	368.05	1.60	0.22	5.35	0.17	75.47	8.28	−0.16
SRHA	20.07	22.16	8.19	0.54	0.01	394.22	1.10	0.42	10.02	0.38	15.33	51.91	−0.25
LEHA	23.58	19.29	8.02	0.25	0.02	434.01	0.81	0.35	15.07	0.59	7.88	18.25	−007

^aIntensity weighted average values are displayed for number of carbons (C_wa), hydrogens (H_wa), oxygens (O_wa), nitrogens (N_wa), sulfurs (S_wa), molecular weights (m/z_wa), hydrogen to carbon ratios (H/C_wa), and oxygen to carbon ratios (O/C_wa). ^b,cBoth MLB_L% and CRAM% are obtained by dividing the total intensity of the corresponding molecular formula by the total intensity of the molecular formula.