1. David A. Ussiri and Chris E. Johnson; Syracuse University
Chemical and spectroscopic properties of humic substances from soils and streams of a northeastern forest ecosystem
David A. Ussiri and Chris E. Johnson; Syracuse University

2. Introduction
Organic matter regulates ecosystem processes in both soils and natural waters
Forms complexes with metals
Transport of contaminants in soils and natural waters
Acid base chemistry of soils and natural waters

3. Objectives
To characterize organic matter extracted from soils, soil solution and stream water
Examine the changing composition of OM as water moves from soils to stream

4. Methods Soil solution and stream water:
Soil solution was collected from six tension-free lysimeter sites in W5 and bulked according to horizons
Stream solution was collected above W5 weir
Concentrated soil solution and stream water samples were freeze-dried and analyzed by 13-C CPMAS NMR
Fulvic acid was extracted from genetic horizons sampled in summer 1998 in W5

5. SOIL: extract with 0.5M NaOH
Solution
Fulvic acid
Displace with
0.1 NaOH
Purify and
and freeze-dry
Solution: Fulvic
acid fraction
Pass through acid washed XAD-8 resin
Precipitate:
Humic acid fraction
Acidify and
centrifuge

6. Dissolved organic carbon fractions in soil solution and stream water
Results
Dissolved organic carbon fractions in soil solution and stream water
Source
pHw
DOC (mol L-1)
Hydrophobic
Hydrophilic
acid
base
neutral Oa
4.19
878 51
4.0
4.5 40
0.1 Bh
4.45
883 37
0.2 63 Bs
5.10
800 23
3.9 68
4.4
Stream
5.33 75 36
6.4
1.7 29 27

7. Peak Assignments in 13C CPMAS NMR
Ketone
C=O
COOH/
Amide
O-Alkyl-C
(Carbohydrates)
Aromatic C
Alkyl-C

8. Bulk Stream DOC Bulk soil solution DOC Chemical shifts (ppm) -40 40 8040 80
120
160
200
240
Bulk Stream DOC
Bulk soil solution DOC

9. Soil fulvic acid
Soil solution

11. Conclusions
DOC collected under the Oa horizon had higher concentration of hydrophobic compounds, while the DOC from in the mineral horizons was higher in hydrophilic compounds. Stream DOC was less acidic than the soil solutions.

12. Conclusions
NMR analysis showed that soil solutions had higher fractions of O-alkyl C and lower alkyl C compared to stream water DOC
OC isolated from stream water differed in structural composition from OC in soil solution and soil fulvic acid.

13. Why Isn’t Stream DOC like Soil Solution DOC?
Selective immobilization in deep mineral soil (below Bs lysimeters).
Importance of riparian-zone soils.
In-stream consumption of DOC.