Structural Analysis of Humic Acid in Soil at Different Corn Straw Returning Modes through Fluorescence Spectroscopy and Infrared Spectroscopy
Table 3
Typical properties of monodimensional fluorescence spectra of soil humic acids at different straw returning modes.
Treatment
Soil depth (cm)
Emission
Excitation
Synchronous-scan
527/518 nm intensity (a.u.)
300 nm intensity (a.u.)
448 nm intensity (a.u.)
380 nm intensity (a.u.)
456 nm intensity (a.u.)
I456/I380
CK
5–20
183.5
222.3
249.3
74.8
215.8
2.89
St
130.2
188.2
167.5
53.5
138.2
2.58
Ss
168.3
226.3
236.6
78.2
212.9
2.72
Smt
150.7
198.5
208.8
63.5
166.2
2.62
Sms
165.8
219.2
225.4
68.9
182.1
2.64
CK
20–40
161.5
216.5
222.4
73.6
192.2
2.61
St
143.4
197.5
185.7
60.7
155.5
2.56
Ss
179.6
235.6
245.9
85.0
230.4
2.71
Smt
164.9
221.7
223.9
68.7
183.2
2.67
Sms
155.1
205.5
221.7
73.5
190.7
2.59
Note: no straw was applied (CK), straw returning to topsoil (St), straw returning to subsoil (Ss), straw mixing with topsoil (Smt), and straw mixing with subsoil (Sms).
