Table 2. Spectral characteristics of the material.

No.	Humic acids					Fulvic acids
	A250/465	A280/465	A465/665	ΔA1/ΔA2	Δlog K	A250/465	A280/465	A465/665	ΔA1/ΔA2	Δlog K
1	7.08	5.96	4.36	1.46	0.68	16.82	12.44	5.69	1.82	0.89
2	7.94	6.85	5.46	1.53	0.76	17.35	12.57	5.46	2.06	0.87
3	7.65	6.47	4.82	1.56	0.70	17.63	12.98	7.10	1.83	0.97
4	6.68	5.60	4.70	1.56	0.67	24.3	16.92	5.00	2.12	0.95
5	7.38	5.92	5.03	1.75	0.67	19.88	14.26	7.19	1.80	1.01
6	7.77	6.29	5.09	1.62	0.70	20.21	14.36	7.16	1.72	1.04
7	6.88	5.76	4.05	1.44	0.65	12.88	9.75	5.65	1.56	0.84
8	9.03	7.73	5.41	1.53	0.80	19.48	14.03	4.98	1.82	0.94

Notes:

A_250/465, the ratio of absorbance values at λ = 250 nm and λ = 465 nm; A_280/465, the ratio of absorbance values at λ = 280 nm and λ = 465 nm; A₄₆₅/₆₆₅, the ratio of absorbance values at λ = 465 nm and λ = 665 nm; Δlog K = log K_{400 nm} − log K_{600 nm}, where K is the absorbance value at 400 nm and 600 nm; ΔA₁/ΔA₂, where: ΔA₁ = A_{290 nm} − A_{333 nm}, ΔA₂ = A_{357 nm} − A_{416 nm} (Table S3).