沙漠研究 22-1, 49 -52 (2012 )"DT X / ICAL 1"

Journal of Arid Land Studies－Refereed Paper－Characterization of Humic Substances in Sediment
on Joumine Reservoir in Tunisia
Atsushi KAWACHI*1), Parida YAMADA1), Mitsuteru IRIE1) and Hiroko ISODA1)
Abstract: In arid and semi-arid land, the rehabilitation of reservoirs such as sediment dredging is necessary in order to utilize thewater resource sustainably, but it has not been carried out due to its high cost of operation in developing countries. Thus, valorizationof the sediment to generate income which will be used to cover the cost of operation is discussed. In this study, the content andcharacteristics of humic substances in the sediment were examined as a first step toward the utilization of the sediment as a material forsoil amelioration. Humic acid and fulvic acid (JS-FA) in the sediment of Joumine reservoir located in the northern part of Tunisia
were extracted according to the standard method of International Humic Substance Society. The volume of the extracted material as
humic acid was so small that it was not possible to detect. On the other hand, the content of extracted fulvic acid was approximately
0.5% of the organic matter content of the sediment. Then, in order to confirm whether the extracted material is fulvic acid or not, theabsorption spectrum was determined by measuring FT-IR spectroscopy and was compared with the spectra of fulvic acids of peat(CP-FA) and weathered coal (WC-FA). Results show that the spectrum of JS-FA was similar to the spectra of CP-FA and WC-FA,
confirming that JS-FA was fulvic acid. Additionally, the FAs extracted from the sediment collected in August and December 2010
had different characteristics compared to the FA from the sediment in the Japanese reservoir.
Key Words: FTIR, Fulvic acid, Reservoir, Sediment, Semi-arid land

1. Introduction
Tunisia, one of the North African countries, is an area
where there is a big environmental gradient because thedistance from its north which has a Mediterranean climate to
the south area with an arid climate is 400 km long. In thisregion, a great variety of living species can be found. It has
been reported that some plants exposure to produce usefulcompounds caused by environmental stresses such as solarradiations, temperature, saline-alkali soil and the others.
Some of the olives, aromatic, medicinal plants, and halophytes
have already been cultivated as commercial products.
Considering sustainable utilization of bio-resource, water
resource management is one of the essential points in theregion.
Generally, agriculture in arid and semi-arid regions isdependent on groundwater for irrigation or water resources.
In Tunisia, however, water transfer systems consist of pipe lines
and canals constructed to transfer surface water from themountain area in the north to the coastal urban area andfarming area where the demand for water is high. Thus, theratio of water supply from surface water and groundwater is
50/50 in this country (Irie et al., 2009)
Currently, the population in Tunisia is increasing, so it isassumed that in addition to the agricultural water scarcity, thedaily life water supply is also getting scarce. However 97%* Corresponding Author: kawachi.atsushi.fp@u.tsukuba.ac.jp
1-1-1, Tennodai, Tsukuba, Ibaraki, Japan, 305-8572
1) Alliance for Research on North Africa, University of Tsukuba JAPANof available surface water in Tunisia has already been used orplanned to exploit. It is so difficult to exploit new resource of
surface water as it is also necessary that the present reservoirs
will be operated sustainably.
In general, the storage capacity of reservoir is decreasing
year by year because of sedimentation. Many reservoirs in
Tunisia have the same problem (Ben Mammou and Laouti,2007), so the rehabilitation of these reservoirs by for example,
dredging operation is necessary. However, the North Africancountries, including Tunisia, cannot perform the reservoirs
rehabilitation because of financial difficulties. As a measure
to be taken, it is suggested that the cost associated with theoperation will be covered by the proceeds from valorizing andutilizing the sediment in reservoirs.
This research, from this view point, focused its attention on
humic substances (HS) in the sediment. Fulvic acid (FA),which is one of the HS, is approved as a food product, and its
anti-allergy property has also already been reported (Yamada etal., 2007). It was also reported that HS renders persistentorganic chloride harmless and ameliorates saline-alkali soilwhich is a problem in arid and semi-arid land (Fukushima,2007).
On the other hand, as part of the research on HS in
sediment on reservoir, Toyoda et al. (2009) reported on theutilization of HS from reservoir in Japan. However, thenumber of research on HS in the reservoir is not more than theresearch devoted on freshwater lake and brackish lagoon.
It is thought that HS originates from the organic matter
supplied by plant debris from the upstream basin (externalsource) and phytoplankton in reservoir (internal source). The
characteristics are different because of the differences inclimate, natural circumstances and social surroundings.
However there is no previous research on HS in sediment ofreservoir in semi-arid and arid land.
This paper investigated the characteristics of HS as a firststep to utilize the sediment from water reservoir in semi-arid
and arid lands with the objective for an efficient water
management and utilization of bio-resource.

Fig. 1. Location of sediment sample collection on Joumine reservoir.

2. Materials and methods

Table 1. General characteristics of the sediment collected in Dec. 2010.

2.1. Study siteIn this paper, humic substances from sediment of Jouminereservoir, located in the north of Tunisia, were extracted andanalyzed. The upstream watershed area of Joumine reservoir
is 418 km2 and the reservoir capacity is 130 million m3 which
ranks 5th in water storage capacity among all the water
reservoirs in Tunisia.
Salinity of the water in the reservoir is lower than the otherreservoirs in Tunisia that the water in the Joumine is utilized not
only for drinking and irrigation but also to dilute the water fromother reservoirs which contain relatively higher salinity.
This reservoir has been in use since 1986. The mean
residence time is about 2 years. It is longer than the residence
time of reservoirs in Japan, which is at most 1 year or less.
Also water current in the reservoir is low so that the sediment
easily accumulates in the bottom.
2.2. Sample collection
In August and December 2010, sediments were collectedfrom the bed of the central part of the reservoir by using an
Ekman-Birge bottom sampler (RIGO CO., LTD.). Collection
point is shown in Figure 1. The collected sample was packed
into plastic bags in the field, then brought to Japan by air andkept in 4°C prior to analyses.
The depth of sampling location is about 25 meters.
Vertical profiles of the water quality has been measured inAugust and December 2010 and it was confirmed that thewater in the points where the depth is more than 10 meters, theconcentration of dissolved oxygen is low and this is caused bythermal stratification in summer (Irie et al., 2011). In addition,
it was reported that the low oxygen concentration occurs for 6months, from April to October.
2.3. Physicochemical parameters
In the laboratory, after the sediment sample was dried in an(×106) [m]
4.094
4.093

Sample collection point

4.092
4.091
4.090

Depth (m)4.089

5 10 15 20 25 30 35 40 45 50

5.48

5.50

pH (H2O)EC (H2O)
moisture
IL (1 h at 750 °C)

5.52

5.54 (×105) [m]8.60.444 mS/cm
59.4 %, as received
18.4 dry%oven at 60°C for 48 h, the pH (1:2.5, H2O) and electric
conductivity (EC; 1:5, H2O) were measured byMulti-Parameter PCTestr 35 (OAKTON Instruments).
Moisture and ignition loss (IL) were determined by thefollowing procedure: The weighed sample of sediment wasplaced in dry and weighed porcelain crucible, the crucible andits content were dried in an oven at 105°C for 24 h. Afterbeing allowed to cool in a desiccator, the crucible wasreweighed. The percentage of moisture was calculated using
equation 1:
Moisture [%] = (w0 - w105) / w0 ×100
(1)
where w0 is the initial weight of the sample and w105 is theweight of the sample after being heated at 105°C. Similarly,
to determine the IL, weighed samples of the sediment in dry
weighed crucible were placed in a muffle furnace at 750°C for
1 h. The IL was calculated using equation 2:IL [%] = (w105 - w750) / w105 ×100
(2)
where w750 is the weight of the sample after being burned at750°C.
2.4. Isolation of humic substances
Humic acid (HA) and fulvic acid (FA) in the sediment wereextracted according to the standard method of International
Humic Substance Society (IHSS).
2.5. FT-IR spectroscopy
Spectra were recorded on a Fourier-Transformed Infrared(FT-IR) spectrophotometer (JASCO Corp., FT/IR-300E, Rev.
1.00). The KBr pellets were made from 1 mg HS and 95 mg
KBr. The spectra resolution was 4 cm-1. A pellet consistingof only KBr was used as the reference material.

CP-FA
CP-FA

Absorbance

WC-FA
WC-FA

Dec 10-FA

Aug 10-FA

3900

3400

2400

2900

1900

1400

900

400

Wave number [cm-1]

Fig. 2. FT-IR spectra.
Table. 2. Elemental compositions of fulvic acids.

Sample name:
Fulvic acids (FAs)

C [%]

H [%]

N [%]

O [%]

Atomic ratios
H/CO/CAsh[%]

August 2010
December 2010
Ono Reservoir
Mean of the Soil
Mean of the Marine
Mean of the Peat

50.1
52.1
50.7
45.3
45.0
54.2

6.0
5.7
4.2
5.0
5.9
5.3

4.9
4.4
2.5
2.6
4.1
2.0

39.1
37.7
42.7
46.2
45.1
37.8

1.44
1.32
0.98
1.35
1.56
1.20

48.4
26.7
-2.6 Elemental analysis
The carbon, hydrogen, and nitrogen contents of the two
FAs extracted from the sediment were determined using thePerkin-Elmer 2400 CHN Elemental Analyzer. Oxygen
content was calculated for the difference of C, H, and N.
Total ash was measured as the following: FA samples dried at105°C for 24 h in dry weighed crucible was placed in a muffle
furnace at 600°C for 2 h.

3. Results and Discussion
3.1. General characteristics of sediment and content ofhumic substances
Table 1 shows the general characteristics of sediment. As
a result, we could extract FA only, its content wasapproximately 0.5% of IL. On the other hand, HA wasdetermined to be present during the extraction process, but
we could not obtain sufficient sample.
3.2. Comparing with another humic substances
Figure 2 shows the FT-IR spectra of the FAs (Aug 10 - FA

0.59
0.54
0.63
0.78
0.77
0.53

References

Hasegawa et al. (2004)
Rice and MacCarthy(1991)and Dec 10 - FA) from the sediments collected in August andDecember 2010 and the FAs in weathered coal (WC-FA) andCanadian Sphagnum peat (CP-FA) (Yamada, 2002; Yamada etal., 2007)
The spectra of the Aug 10- and Dec 10- FAs were generally
similar to WC- and CP-FAs, proving that these extracts arefulvic acid. However there were a few differences between
the Aug 10- and Dec 10-FAs. For example, the shapes of thespectra around 1700 and 1620 were different as shown in
Figure 2. And also, Dec 10-FA had the peak at 1540 but Aug
10-FA do not. Although what these differences mean is notknown yet, as previous described, water quality around the bedof the reservoir changes with season in summer (August) andwinter (December), especially, water-dissolved oxygen refers
to the process of organic matter decomposition. In otherwords, it is thought that the characteristics of FAs in reservoirchanges due to the oxygen concentration in water which isaerobic in winter and anaerobic in summer.
The results of the elemental analysis are shown in Table 2.
From the results, while the differences between the twosediments collected in August and December 2010 was notsignificant, there was a difference in the atomic ratios between
the Japanese and Tunisian reservoirs. In addition, C and O
contents of the Joumine sediments are similar to Peat. Thus, itis thought that one of the reasons for the decomposition process
is the aerobic and anaerobic conditions of the sediments.

4. Conclusion
It was confirmed that humic substances, especially fulvic
acid, is present in the sediment of reservoir in Tunisia. The
characteristics of fulvic acid in the sediment are generally
similar to the ones in weathered coal and peat. There are a
few different characteristics between the FAs extracted fromthe sediment collected in August and December 2010, andfrom the sediment in the Japanese reservoir. Although thereal cause cannot be determined, it seemed that the watercondition, especially, the aerobic and anaerobic condition in thedecomposition process, is the one of the factors.

Acknowledgement
This research was supported by the JST-JICA SATREPS
project "Valorization of Bio-resources in Semi Arid and Arid
Land for Regional Development" (representative researcher:Prof. Hiroko Isoda, University of Tsukuba, 2009-2014), and theMinistry of Education, Science, Sports and Culture,
Grant-in-Aid for Scientific Research (B), 2010, 22404009(representative researcher: Prof. Mitsuteru Irie, University ofTsukuba).
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