Gabor, Baker, McKnight, and Miller
312
200
0
1000
Fluorescence (arb. units)
2000
3000
4000
5000
6000
250
300
350
F max
λ em (nm)
400
450
500
Figure 9.3. Fluorescence emission spectrum of an aqueous extract of soil at an excitation wavelength
of 254 nm. The broad humic peak (300–500 nm) can be seen between the two sharp Rayleigh scattering peaks. The shaded regions represent the areas used to calculate the HIX EM . The index is calculated by dividing the area under the upper region (435–480 nm) by the area under the lower region
(330–345 nm) and is associated with the degree of humification in the sample. F max indicates the peak
emission intensity. (From Zsolnay et al., 1999.)
0
0
2
4
6
8
Humification Index
10
12
14
16
1
2
Stand. Relative Fluorescence (mg g
–1 )
fumigated mineral soils
Muck Soil
Fulvic Acids
fumigated muck
all o.d soils
f.f.
f.f.
Mineral Soils
a.d.
a.d.
3
4
5
6
7
Figure 9.4. Comparison of the standard relative fluorescence intensity (in units of quinine sulfate
dihydrate equivalent) to HIX EM . Muck soils and mineral soils were treated by air drying, oven drying, and fumigation and then extracted aqueously for fluorescence analysis. The fulvic acid fraction
of each soil was obtained with NaOH pyrophosphate. This plot shows the different signals from the
field fresh (f.f), air dried (a.d.), oven dried (o.d.), and fumigated samples, indicating drying processes
release different fractions of organic matter. (From Zsolnay et al., 1999.)
312
200
0
1000
Fluorescence (arb. units)
2000
3000
4000
5000
6000
250
300
350
F max
λ em (nm)
400
450
500
Figure 9.3. Fluorescence emission spectrum of an aqueous extract of soil at an excitation wavelength
of 254 nm. The broad humic peak (300–500 nm) can be seen between the two sharp Rayleigh scattering peaks. The shaded regions represent the areas used to calculate the HIX EM . The index is calculated by dividing the area under the upper region (435–480 nm) by the area under the lower region
(330–345 nm) and is associated with the degree of humification in the sample. F max indicates the peak
emission intensity. (From Zsolnay et al., 1999.)
0
0
2
4
6
8
Humification Index
10
12
14
16
1
2
Stand. Relative Fluorescence (mg g
–1 )
fumigated mineral soils
Muck Soil
Fulvic Acids
fumigated muck
all o.d soils
f.f.
f.f.
Mineral Soils
a.d.
a.d.
3
4
5
6
7
Figure 9.4. Comparison of the standard relative fluorescence intensity (in units of quinine sulfate
dihydrate equivalent) to HIX EM . Muck soils and mineral soils were treated by air drying, oven drying, and fumigation and then extracted aqueously for fluorescence analysis. The fulvic acid fraction
of each soil was obtained with NaOH pyrophosphate. This plot shows the different signals from the
field fresh (f.f), air dried (a.d.), oven dried (o.d.), and fumigated samples, indicating drying processes
release different fractions of organic matter. (From Zsolnay et al., 1999.)