
J. Jpn. Soc. Soil Phys.
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No. 3+, p. .3 /1 ,**,

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**E#ects of Drying on Bacterial Activity and Iron Formationin Acid Sulfate Soils
Kaoru UENO*, Tadashi ADACHI** and Hajime NARIOKA*** The Graduate School of Natural Science and Technology, Okayama University,-ῌ+ῌ+ Tsushima-naka, Okayama 1**ῌ2/-*, Japan** Faculty of Environmental Science and Technology, Okayama University,-ῌ+ῌ+ Tsushima-naka, Okayama 1**ῌ2/-*, Japan
Abstract
In acid sulfate soils, the heavy acidity is caused by the oxidation of sulfate, mainly pyrite (FeS,).
In the primal acidify stage chemical and bacterial acidify work together.

These bacteria(Thiobacillus ferrooxidans, Thiobacillus thiooxidans) have a huge role as a catalyst.
This studies were examined the e#ects of drying on bacterial acidiﬁcation, mainly on
Thiobacillus ferrooxidans, and the formation of iron in the soil by the incubate experimentation.
Five water content stages were set (+.-*
for water adjustment.

*.,/ kg/kg) by drying process in the incubator at -*After the treatment, these samples were contained in the each bottles andstarted to culture at -*Thiobacillus ferrooxidans propagated rapidly in the water content of Liquid Limit (LL)

Plastic

Limit (PL). Near the water content of PL, the propagation of the bacteria became slow, and they
became decline near by the water content of Shrinkage Limit (SL).
Amorphousfreeiron increased at the primal of acidiﬁcation and changed for crystallized
freeiron. Around SL, the water content that the soil pH was stable, the propagation of thebacteria became slow, and the formation of iron became stable. In the range of water content +.***.1* kg/kg (LLPL), the samples acidiﬁed strongly

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Fundamental physical and chemical
properties of sample soils(in subsoils Polder-Nakaumi, Shimane,depth ; +2/>,+* cm)&SL' HTH#MS^ -*_ `aST # b

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" 5/%% &' pH  +./>../

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Changes in water content, pH and thenumber of bacteria (live) in the periodof water adjustment.

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52

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 Fe,£ ¬ Fe-£ $9­®9¬> !6 '¹Hrº( pH /¯+,9 °?@±²!³<p(M´Fig. ,

Changes in pH in the culture period.

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Fig. -

Changes in crystallized-free-iron and amorphous-free-iron as drying (in the culture period).

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Fig. .

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Relation between crystallized-free-ironand amorphous-free-iron.

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in the culture period.

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< ?<

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53

+.-*, +.** kgῌkg

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54

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Fig. 1 Changes in the number of bacteria(live) in the culture period.

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Fig. 0 Changes in ferrous and ferric ironin the culture period.

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*=-  *t6%
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55

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Fig. 2 Relation between pH and the number ofbacteria (live) in the culture period.

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Fig. 3 Relation between the ratio of ironoxidation of soil and the number ofbacteria (live) in the culture period.

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ῌ3 X 45!"#L +.-*, +.** kgῌkgῌῌ+*f&8 pH 45

!"#L

9Z

Fig. +* Relation between pH and the ratio of
iron oxidation of soil in the culture
period.

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.X)

S [ p 3+ ¼ _,**,`

56

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7=30, PL B'9:>?@&, bc]^
_SL` B3+ 56"#d*YA

3+  56 7, *.1*kgῌkg? _PL /0.ee(#`, F/W@A'(#+ 56f#9:,( SL Bg'B#hCDd
ijklE$m0, <%n@'F#hGH'oI<.pq
#HM4 r#, st uvFJw,  xy z'{|}|~K8
N   pH @&I, .3#
Fe,, Fe-, Fe _OH`,, Fe _OH`- KLzMN
῔ῌ++



9, pH/ %&'|  RF9I

Fig. ++ Changes in the ironῌoxidize-index per
bacteria (live) in the culture period.

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

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ῒ

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7($, *.,/

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mU n _+330` :  µ¶2, pp. /0ῌ1., ·¸¹º, o»´Darrell Kirk Nordstrom, et al.,(+32,) : Acid Sulfate.ῌ ῍ ῐ ῏ ῎Weathering, SSSA Special Publication Number

12, P3Q4/0567R 8S -*T UVI/0, 

Q4, X256

+*, pp.-1ῌ/0, Soil Science Society of America,
Wisconsin.

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+332 : 

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<= 0* , +/+ῌ+/0$©ª ῌ «%e +33- : Thiobacillus ferro-ox-

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