Gabor, Baker, McKnight, and Miller
310
the potential to use spectroscopy on the original water sample to determine the chemical
character of the humic material.
Kalbitz and Geyer (2001) further tested the humification index for the effect of DOC
concentration and spectrometer type (a LS 50B luminescence spectrometer by Perkin
Elmer and a SFM 25 spectrometer by BIO-TEK Instruments). They confirmed that
(a) 65
55
45
35
25
C/N ratio
15
5
(b)
1.35
1.20
1.05
0.09
IR absorptation at 1620 cm
–1
0.75
(c) 1.5
1.4
1.3
r = 0.89
1.2
Humification index (FA)
1.0
0.9
0.8
0.9
0.8
1.0
Humification index of the water sample
1.2
1.3
0.8
0.9
0.8
1.0
Humification index of the water sample
1.2
1.3
0.8
0.9
0.8
1.0
Humification index of the water sample
1.2
1.3
r = 0.66
r = 0.48
Figure 9.2. Correlations of humification index (HIX SYN ) for whole water (x-axis) with the (a) C/N
ratio of the sample, (b) humification index of the fulvic acid fraction, and (c) IR absorption at
1620 cm
–1
. The whole water HIX SYN is calculated as (ex 390/em 408)/(ex 355/em 373) and the fulvic
acid HIX SYN graphed here is calculated as (ex 400/em 418)/(ex 360/ em 378) using synchronous scans
with an 18 nm offset. (From Kalbitz et al. [2000] with minor modifications.)