A C I D SULPHATE S O I L S

I 1 R E S E A R C H P A P E R S

Publication 18 - vol. II

ACID SULPHATE SOILS

Proceedings of the International Symposium on Acid Sulphate Soils 13-20 August 1972, Wageningen, The Netherlands

I I N T R O D U C T O R Y P A P E R S A N D B I B L I O G R A P H Y

I1 RESEARCH PAPERS

Edited by: H. DOST

INTERNATIONAL INSTITUTE FOR LAND RECLAMATION AND IMPROVEMENT P.O. BOX 45 WAGENINGEN THE NETHERLANDS 1973

C O N T E N T S

Papers concerning the formation of’ pi4r i t i c s o i l materials and acid sulphate soils

J.P.ANDRIESSE, N.van BREEMEN, and W.A.BLOKHUIS: The influence of mudlobsters (Thallasina anomala) on the development of acid sulphate soils in mangrove swamps in Sarawak (East Yalaysia)

C.BLOOMFIELD: Acidification and ochre formation in pyritic soils

P.BUURMAN, N.van BREEMEN, and A.G.JONGMANS: A fossil acid sulphate soil in ice-pushed Tertiary deposits near Uelsen

A.HARDAN: Rate of calcium carbonate accumulation by biological sulphate reduction

V.A.JACQ: Biological reduction in the spermosphere and the rhizo- sphere of rice in some acid sulphate soils of Senegal

J.VIEILLEFON: Sur quelques transformations sédimentologiques et minéralogiques dans les sols sulfatés acides du Sénégal

B.VERHOEVEN: Acid sulphate soils in the Wieringermeerpolder, a good 40 years after reclamation

Papers concentrating on the i d e n t i f i c a t i o n of p y r i t e s and the determination of p o t e n t i a l a c i d i % y

R.F.ALLBROOK: The identification of acid sulphate soils in North-west Malaysia

J.BALDENSPERGER: The use of a respirometric method for the evaluation of sulfur oxidation in soils

N.van BREEMEN, MANOP TANDATEMIYA, and SOPON CHANCHAREONSOOK: A detailed survey on the actual and potential soil acidity at the Bang Pakong Land Development Centre, Thailand

D.van DAM, L.J.PONS: Some micromorphological observations on pyrite and reaction products related with its oxidation

.T.N.B.POELMAN: S o i l material rich in pyrite in non-coastal areas

1 1

40

52

7 6

82

99

1 I 4

131

I41

159

I 6 9

197

Papers on physiography, cZassi f icat ion and mapping

J.H.BENZLER: Probleme bei der Kartierung von "Maibolt" und "Pulvererde" - besonderen Formen der sulfatsauren BÖden - in den Marschgebieten Niedersachsen (BRD)

C.J.GRANT: Acid sulphate soils in Hong Kong

C.ROQUER0 DE LABURU and J.GARCIA-CASAL: Suelos de sulfatos Ccidos del "Banhado do Taim", Rio Grande do Sul, El Brasil

C.J.W.WESTERVELD, A.F.van HOLST: Detailed soil survey and its application in areas with actual and potential acid sulphate soils in The Netherlands

C.WALLENBURG: Cat clay and potential cat clay in inland polders

Papers dea Zing w i th soi Z proper t i e s r e la t ed t o extreme a c i d i f i c a t i o n

W.GEBHARDT: Cation exchange and anion adsorption properties of some acid soils in the Central German Mountain range

P.J.GOUS, W.J.FoLSCHER: Growth and nutrition of wheat on acidified mineral soil. Root development and seed formation in relation to KC1-soluble Al and Mn

P.S.FOUCHE, W.J.FoLSCHER: Growth and nutrition of wheat on acidified mineral soil. Effect of CaC12-soil treatment on yield and nutrient uptake

W.SCHELTEMA: Al-clay - a solution to mechanical stability in a heavy clay soil? An orientative study in relation to lowland rice yields and dry crops perspective

Papers t h u t concentrate mainZy on the sub jec t s of reclamation, improuemcnt, management and use o f acid sulphate s o i l s

P.M.DRIESSEN: Pyrite-containing sediments of Southern Kalimantan, Indonesia

2 1 1

2 1 5

229

2 4 3

264

287

302

310

3 1 9

3 4 5

G O M BEYE: Acidification of mangrove soils after empoldering in Lower Casamance. Effects of the type of reclamation system used 359

in potential acid sulphate soils and subsoils in The Netherlands 373 A.F.van HOLST, C.J.W.WESTERVELD: Corrosion of concrete foundations

K.KANAPATHY Reclamation and improvement of acid sulphate soils in West Malaysia

F.N.PONNAMPERIJMA, TASNEE ATTANANDANA, and GORA BEYE: Amelioration of three sulphate soils for lowland rice

3 8 3

3 9 1

Most t a b l e s and al2 f i g u r e s are p r i n t e d a t t he end o f the re l evan t papers

R E S E A R C H P A P E R S

F O R M A T I O N O F P Y R I T I C

S O I L 8# ATE RIALS A N D

A C I D S U L P H A T E S O I L S

THE INFLUENCE OF MUD LOBSTERS (THALASSINA A N W L A ) ON THE DEVELOPMENT OF ACID SULPHATE SOILS I N MANGROVE SWAMPS I N SARAWAK (EAST-MALAYSIA)

J . P . Andriesse Royal Tropical I n s t i t u t e , Department of AgricuZtural Research Ams t e r d m ili. van Breemen & W.A. BZokhuis Agricul tural Universi ty , Department o f Soil Science and GeoZogy Wageningen, The Netherlands

Introduction

Extensive swamps with mangrove and nipah (Nipa fruticans) vegetation occur in

deltaic and estuarine areas along the west coast of Sarawak (West Borneo).

Andriesse and Sim (I) indicated that potentially acid soil, present at depth in these swamps, is brought to the surface by the mud lobster (Thalassina anomala)

which occurs prolifically in such areas. The lobsters build large mounds out of

subsoil material, which acidifies strongly upon aeration and oxidation. The exis-

tence of such acid soil material forms a threat to agricultural development. If the land is to be used for irrigated crops, a thick layer of acid soil will be

spread over the surface of the land upon levelling.

The present paper deals with detailed field studies on the occurrence of these

specific soils, and with laboratory investigations on the nature of the soil

materials involved and the soil forming processes taking place.

Environmental conditions

The locality studied forms part of the Sarawak River Delta (Fig.1). The Delta is

built up of deposits brought down mainly by the Sarawak River. Some material from

locally occurring outcrops of andesitic rocks and quartz sandstones, forming

monadnocks in this otherwise flat, swampy area, contribute to the deposits in a

very minor way.

The Sarawak River sediments have a silty clay texture and originate predominantly

from weathered shales and quartz sandstones and subordinately from material wea-

thered from andesitic rocktypes. Andriesse (2) has shown that these weathered rock

materials are Poor in calcium, magnesium, and iron, and moderately rich in potas-

sium. He suggested that after deposition the materials are enriched with magnesi-

um and calcium from sea-water.

The delta probably started to form after the last Glacial period when the sea

level was about 3-6 m higher than at present ( 2 ) . During the Holocene the deposi-

tional level dropped gradually following a retreat of the sea. A considerable part of the Delta is formed by quite recent deposits, which have accumulated ap-

proximately 0-1.5 m above present high tide level. Remnants of the original depo-

sitional level are still present as slightly raised shields (partly eroded), si-

tuated above the present deposits.

The natural drainage of the delta is effected by an intricate pattern of creeks

and river branches which cut up the area into numerous large and small "islands"

(Fig,l). The centres of the larger islands are commonly formed by remnants of

the above mentioned shields, which are drained by a radial drainage system. The

internal drainage of the soils is not very effective and the watertable does not

appreciably follow the tidal fluctuations, which nlay have amplitudes of more than

3 m.

The climate of the area is typical for Humid Tropical Lowlands. The mean annual rainfall is approximately 4000 mm, well distributed over the months. Although

there is a wet season of approximately 4 months, during which up to 75Z of the

rain falls, there is no month in the year with a precipitation of less than 100 mm.

This would indicate that the soils are continuously wet throughout the year (12).

The temperatures are always between 20 OC and 35 O C . During the wet period flood- ing with fresh to slightly brackish water occurs locally when the Sarawak river

is at full bank discharge capacity. In the dry season the salinity level of the river water is much higher. Groundwater in most of the delta area is weakly saline

to saline, depending on the time of the year and the distance Erom the river or

tidal creeks.

The vegetation is typical for a transition from a pure mangrove forest to a fresh-

water swamp forest. The highest parts of the land, with lowest salinity (: 0.5

mhos/cm), are dominated by nibong (Oncosperma filamentosa) palms, while the lo-

west parts, with highest salt levels (> 30 mmhos/cm), viz near river branches and

creeks, carry an Avicennia-Sonneratia association or a Bruguera-Rhizophora asso-

ciation.The largest part of the area, at intermediate elevations and salinity le-

vels, is covered by nipah (Nipa fruticans), either as a monostand or in combina-

tion with the Bruguiera-Rhizophora association with locally a considerable mixing

of Heritiera littoralis (2).

In essence only two natural soil types are present in the area, namely

1 . Pendam series, soils occupying the slightly raised "shields";

2. Rajang series, soils occupying the present depositional plain and considered

12

to be younger than the Pendam series. Variations within these series are caused

by complex patterns in salinity, organic matter content, and drainage.

The influence of human and soil faunal activities has further complicated these

patterns.

Representative profiles of the two soil series are given in Appendix 1 .

Areas occupied by the Rajang series often show strong microrelief caused by the

occurrence of mud lobster mounds. These lobsters, which live in communities,

channel into the soft subsoil, thereby consuming most of the soil material, from

which they extract energy-supplying proteins and carbohydrates occurring in the

organic materials (mainly debris from nipah palms). The material passing out of

the digestive system (soft mud intensively mixed with comminuted organic debris

and often dark gray to black coloured due to the presence of Fes) is deposited

around one of the several more or less vertical pipes with a diameter between

5 and 20 cm. A mound is built up by successive mud-flows in a manner not unlike

that in which a stratovolcano is formed. Several lobsters may be responsible for

the building of one mound. The lobsters appear to occur prolifically in areas of

intermediate salinity. Lobsters commonly channel to a depth of about 120 cm and

build mounds as high as 1.5 m, with a diameter at the base of about 1 to 2 m.

A description of a typical lobster mound is given in Appendix 1 .

Review of earlier investigations

It was noted during a reconnaissance soil survey that the lobster mounds contai-

ned considerable quantities of yellow coloured soil resembling the jarosite-rich

material which is usually found in acid sulphate soils. Therefore, when detailed

investigations were needed for a planned irrigation project in the area, atten-

tion was focussed on these mounds, which cover approximately 40% of the land surface (2).

soil samples were taken in representative areas along straight lines at fixed

intervals and at depths of 0-15 cm, 30-45 cm, and 60-75 cm below the surface, regardless of whether lobster mounds were present or absent.

In order to investigate possible relationships between the chemical characteri-

stics of the soils and their position relative to lobster mounds, the sample lo- cations were classified as follows:

a) on top of lobster mound

b) on slope of mound

13

c) at foot of mound

d) in between mounds

e) no mounds present

pH (water) measurements were carried out soon after sampling under fieldmoist

condition (samples sealed in plastic bags). Subsequently the samples were sub-

jected to slow air-drying and periodical rewetting for one month, followed by

a final drying for about 8 hours in the sun, after which the pH (water) was

measured again.

Fig.2 (b and c) shows the influence of drying on the pH. While under field con-

ditions, subsoils tend to be generally neutral and topsoils slightly acid; in The dried samples subsoils have become most acid. Although the average pH for the

dried subsoils is just above 4, values between 2 and 3 were observed frequently. Thus potentially acid material is present at depth over large parts of the area.

This was confirmed by the total sulphur contents of the samples (Fig.2 a): the

subsoil samples show the highest values.

The low pH values of dried soils indicate that reclamation may be risky. To eva-

luate the risk factor, the pH-values after drying were categorized into the

following groups:

a) higher than 4.5 no risk b) 4 . 5 - 3 . 5 small risk c) less than 3 . 5 considerable risk

d) higher than 4 .5 but drop of at least

1 unit after drying possible risk

The important role which lobster mounds play in the development of acidity in these soils is illustrated by the data of Table I.

In 75% of the cases, the tops of the lobster mounds contain potentially strongly

acid material, while in locations where no mounds are present this material is

only found in 9% of the samples in question. Further investigations showed that

the 9% refers mainly to the area of the older Pendam series (now under cultiva-

tion) where lobster mounds may once have been present.

Van der Kevie ( I O ) estimated from data supplied by Andriesse and Sim (2), that

after the levelling of all lobster mounds in the investigated area, half the

land surface would be covered with a layer of at least 4 cm of extremely acid soil, 12 percent with an acid layer of I O cm and 4 percent with a layer of acid soil of nearly 25 cm.

1 4

TABLE 1

RELATIONSHIP BETWEEN LOBSTER MOUNDS AND THE DEVELOPMENT OF ACIDITY

(after Andriesse and Sim (2)

percentage of all topsoil samples location pH-values (after drying) as follows:

(0-15 cm) > 4 . 5 4.5-3.5 3.5 > 4 . 5 (drop of at

frequency of occurrence of topsoils with

least 1 unit)

30 on top of 4.5% 18 % 75 % 1.5%

I O on slope of 20 % 40 % 35.5% 4.7% mound

mound 13.5 at foot of 36.4% 30 % 22.7% 10.9%

mound 12.7 in between 38.1% 16.7% 28.5% 16.7%

mounds 34 no mounds 54 % 30 % 9 Z 7 %

pres ent

Results of the present work

Subsequent to the studies by Andriesse and Sim (2), which were mainly concerned with soil evaluation problems, detailed studies on various chemical and minera-

logical aspects of the soils were conducted.

Detailed descriptions were made of two soil profiles (one Rajang and one Pendam

Soil), and of four lobster mounds. Two profiles and one representative lobster

mound were selected for further study. The soil descriptions are given in Appen- dix I .

In addition,]& mud samples for EH-pH determination and extraction of the inter-

stitial water, 10 groundwater samples taken from augerholes, and 3 surface water

samples were collected at various locations.

Particulars on sample treatment and analytical techniques are given in Appendix 2.

Chemical and mineralogical investigations

The Rajang Soil is very Poorly drained and permanently reduced below 60 cm. Except

for brown mottles and a weak angular blocky structure in the upper 60 cm, signs .

15

TABLE 2 . SOME CHEMICAL, PHYSICAL, AND MINERALOGICAL DATA

S-MINERALS++++) SAMPLE PH org. GRANULOMETRIC COMPOSITION+++) SILT FRACTION CLAY FRACTION

+++) PROFILE depth (cm) No. fresh” dry’” c+++) 50 pm Stot pyrite jarosite pyrite jarosite

RAJANG

LOBSTER MOUND

PENDAM

L\

O - 20 I 6 . 5 20 - 6 0 2 6 . 4 90 - 120 3 6 . 9

fresh mud 4 6 . 5 o - 7.5 i 2.7

7 . 5 - 30 6 3 . 4 30 - 7 5 7 3.9

centre below 8 6 . 4 surface

O - 15 9 4 . 4 20 - 3 0 10 4 .0 30 - 45 I 1 3 . 5 80 - 120 12 5.7

6 . 5 3.2

6 . 3 4.7

5 . 9 4 . 2

3.4 9 . 0

3.1 6 . 3

3 . 8 6.1

3.6 7.6

3 . 5 9.7

3 .5 6.7

3 . 8 4.1

2 . 8 7 . 2

2 . 9 8 .1

4 8 . 2 5 1 . 5

51.1 4 8 . 8

52 .9 4 7 . 0

3 9 . 6 5 9 . 5

41.6 5 8 . 0

3 9 . 3 6 0 . 2

32 .1 6 6 . 4

32 .7 65 .7

33.9 65.7

4 2 . 3 5 7 . 3

44.9 5 3 . 8

4 8 . 5 5 0 . 3

0 . 3

0.1

0.1

0 . 5

0 . 4

0 . 5

1.5

1.6

0 .4

0 . 4

I .3

I . 2

0.15 tr tr 0 . 4 9 ++ I . 6 6 +++ tr

2 . 3 2 ++ tr 1 . 2 0 tr

0 . 9 5 tr tr

0.90 tr tr tr 2 . 3 4 ++ tr tr

+ + +

o. 12 tr 0.13 tr 1.97 ++ 2.88 +++

tr

measured in a 1 : l soil water suspension just after sampling (Soils Laboratory of Semcngak Agricultural Research St., Sarawak)

measured in a 1 : l O water extract, two years after sampling (the soils were oven-dried immediately after sampling) expressed as percentages, on oven-dry basis identified optically and by X-ray diffraction; tr = trace, + = some, ++ = much, +++ = very much

’ ,

++)

+++) ++++)

of profile development are absent. Under field conditions, the pH is near neutral

(see Table 2), although in the subsoil total S (mainly as pyrite) is fairly

high. The pH-drop upon drying is small. The samples were oven-dried immediately

after sampling. Slow air-drying might have resulted in stronger acidification.

The lobster mound is mottled throughout with abundant pale yellow jarosite,

especially on the surface. Under field conditions the pH is low (2.7 to 3 . 9 ) ,

except for the fresh mud and the part below the land surface level (pH 6.5)

which, however, become very acid upon drying. These two potentially acid samples

have high total S contents. Organic matter is high, especially in the unoxidized

samples, and this probably reflects the fecal character of the material.

The Pendam soil has a permanently reduced horizon at shallower depth than the

Rajang profile. The upper 30 cms, however, appear more strongly oxidized and the

first mineral horizon is homogeneously brown, probably as a result of intensive

biological mixing.

High worm activity was also observed in other Pendam profiles. A t depth much

Pyrite is present and drying results in severe acidification.

In the Rajang soil the exchange complex (see Table 3) is dominated by Ca and Mg.

The relatively high figures for adsorbed Na show the influence of brackish water

of marine origin.

The other samples ( 4 to 12) have low contents of exchangeable bases and high va-

lues for the exchange acidity. A l s o the effective CEC's (CEC at the actual pH of

the (dried) sample) are much lower. The exchange complex of the acid samples is

saturated with aluminium (4 -11 me/100 g), assumed to be present in tri-

valent form and ferric iron (1 -7 me/IOO g). The samples that acidify upon dry- ing (Nos. 4 , 8, 1 1 , and 12) undoubtedly had much lower values for the exchange

acidity before drying. The sharp drop in the MgO and Ca0 contents upon oxidation

of the fresh mud (Cf. Table 4 , Samples 4 and 5) must be attributed to the release

and subsequent leaching of exchangeable Ca and Mg.

Although the CEC for the < 2 p m fraction is highest for the Rajang samples,

which also have the highest clay contents, the CEC values for the whole soil at pH 8.2 are highest in samples from the lobster mound. This probably reflects

the high Organic matter content of these samples. A l s o the pH dependent fraction

of the CEC is relatively large in the organic rich samples, as follows from the

difference in CEC at PH 8.2 and at pH 4 . 8 .

X-ray diffraction of the clay separates revealed the presence of trioctaedral

1 7

I

m

TABLE 3 . EXCHANGEABLE CATIONS AND CEC (me/lOO g)

CEC SAMPLE Ca I Na exch. Fe 'I effec- p~ p~ fraction

NO. Mg K acidity tive 6.8 8 . 2

smectite(s), kaolinite, illite, chlorite, an interlayer clay mineral, and small

amounts (5 to 10%) of quartz. A l l first order peaks of the clay minerals were

broad, indicating poor crystallinity. Pyrite was detected in Samples 3 and 8,

and jarosite in Samples 5, 6 , 7, and 9 (Table 2).

Optical and X-ray diffraction studies of the silt fraction showed, besides py-

rite and jarosite') as indicated in Table 2, mainly quartz, with small amounts

of illite, kaolinite and weathered potash feldspar.

Apart from the sulphur minerals, quantitative differences in the mineralogical

composition of the clay and silt fractions of the different samples could not be

detected.

Results of elemental analyses are given in Table 4. The data on the clay fracti- ons were used to calculate a normative mineralogical composition according to the

goethite norm ( 1 2 ) , applying a chlorite variant with a chlorite having as formula

unit 1/10 (3SiO2.A1~O~.2Fe0.3MgO).4Hz0.

The results (Table 5) are in good agreement with the X-ray diffraction data, except for the calculated chlorite content, which appears to be too low.

Apart from the goethite contents and the amounts of kaolinite and montmorillonite

in the Rajang soil, the normative composition of the samples of any one profile

i s rather uniform. Clear differences exist between the montmorillonite contents

Of samples from different locations: Rajang 19-27%, Pendam 16-18%, and the lob-

ster mound 13-16%. These trends are in agreement with the data on the CEC of the

clay fraction (Table 3 ) , which are 26 to 27 me/100 g for the Rajang samples, 20-22

for the Pendam profile, and 15-19 me/IOO g for the lobster mound. An attempt to

calculate the composition of the sand and silt fractions according to the epinorm

(13) met with difficulties. Data on the distribution of total sulphur over the clay and the non-clay fraction were not available. At the outset it was assumed

that all sulphur occurs in the sand and silt fractions either as pyrite (Samples

1,2,3,4,8,]1, and 1 2 ) or as jarosite (all other samples). However, except for the samples 1 7 2 , 3 , and 1 1 , insufficient iron was present to accomodate the sulphur.

A s it i s very unlikely that considerable amounts of other sulphur minerals (e.g.

elemental s ) are Present (cf. 4), the calculations showed that at least part of the pyrite (in Samples 4, 8, and 12) and most (in Samples 5, and 6 ) or some (in Samples 7, 9, and 10) O f the jarosite occurs in the clay fraction. This i s lar-

gely in accordance with the X-ray diffraction data (see Table 2).

So it appears that the calculated goethite contents in the clay fractions of Sam-

+) Subsequent x-ray diffraction studies have shown that the jarosite mineral in question is in fact natro-jarosite NaFe3(~0,,)2(~~)6

19

TABLE 4. ELEMENTAL ANALYSIS OE THE FINE EARTH (

ples 5 and 6 are too high, because most of the ferric iron is present in jarosi-

te. Due to lack of data, both on the S-content of the clay and on the degree of

substitution by hydronium and by sodium for potassium in the jarosite, no attempts

were made to refine the calculations.

Studies on the composition of interstitial waters

Data on the composition of the soil solution can be useful in soil investigations

because (a) as a result of the large mass ratio between solid and dissolved mat-

ter in any soil-water system, the composition of the aqueous phase is a very sen-

sitive indicator for many processes involving mineral transformations, and (b)

equilibrium studies may reveal control mechanisms for the levels of various ele-

ments in the soil solution.

The analytical results for 26 water samples from various locations within the

studied area are given in Table 6. waters from Rajan soils and from lobster mounds are very saline as a result of seawater influence. The groundwaters from

the Pendam area are fresh to slightly brackish.

Seawater can be regarded as a starting point when compositional variations resul-

ting from various processes are being considered. Assuming that only the chlori-

de concentration is affected by dilution and is not influenced by interactions

with minerals, it is possible to calculate the degree of dilution with respect

to seawater, according to:

D = ( C l ) (brackets denote concentrations). seawater ' s amp 1 e If the change in composition of ground- and surface water were only a matter of dilution with pure

X , written as:

("sample

would be equal to

water, the "concentration factor" for any dissolved component

") seawater

. Concentration factors higher than 1 indicate that the con- centration Of the component in question is increased relative to diluted seawater

because Of dissolution from the solid phase. Concentration factors lower than

one are evidence of the removal of a component, e.g. by precipitation.

Concentration factors for a number of ions in five groups of samples were calcula-

ted (on the basis of standard seawater, Sample 27 in Table 6), averaged, put in order of an increasing degree of Sob-release, and plotted in F i g . 3 . In the fresh

mud of the lobster mounds, the concentrations of Na, K, Mg and Ca are very simi- lar to those expected from simple dilution of seawater. This indicates that little

2 1

TABLE 5 . NORMATIVE COMPOSITION OF THE CLAY FRACTIONS (GOETHITE NORM)

SAMPLE Excess NO. Q M s Chl Mm Kaol Go Ru S t r H2O

1 6 . 4 31.5 1 .3 26 .8 27 .7 5 . 9 0 . 7 0 . 4 6 . 8

2 6 . 9 32.6 1 .7 25 .8 27.6 4 .5 0 . 7 0.1 7 . 9

3 9.8 32.9 2 . 2 1 9 . 2 3 1 . 3 3 . 5 0 . 7 0.1 8.9

4 1 1 . 1 31.0 1 . 3 13.2 3 6 . 4 5 . 5 0.8 0 . 4 2 .8

5 1 1 . 2 31.5 1.0 1 5 . 0 32 .3 8.1 0 . 8 0 . 4 1 2 . 0

6 10.2 3 2 . 6 1.0 1 4 . 8 32 .1 8 . 1 0.8 0 . 4 1 2 . 5

7 10.0 3 2 . 4 1.0 1 6 . 0 3 5 . 3 4 . 0 0.9 0 . 4 11.8

8 10.0 32.2 1 . 3 15.8 33 .5 5.1 0.8 1 . 3 + ) 1 6 . 7

Y 1 0 . 2 3 2 . 9 1 . 3 1 6 . 0 3 6 . 3 2 . 1 0 .9 0.1 6 . 1

I O 8.7 3 3 . 3 1.0 1 7 . 6 35.5 2.7 0 .9 0.1 6.1

I I 9.5 3 3 . 8 1.0 1 6 . 0 3 5 . 5 2 .9 0 . 9 0.1 7 . 6

12 10.0 34.1 1.3 16 .6 34 .4 2 .7 0.8 0.1 10.6

Q = quartz Ka01 = kaolinite

Ms = muscovite (illite) Go = goethite

Chl= chlorite Ru = rutile

Mm = montmorillonite Str = strengite

+) see second note of Table 4 .

22

or no mineral-solution interactions involving these ions have taken place. How-

ever sulphate is much lower and bicarbonate is correspondingly higher as a res-

ult of sulphate reduction according to:

so:- + ZCH~O (organic matter) = ZHCO; + H ~ S

The Rajang waters are very similar, except that sulphate reduction is of minor

importance.

In the interior of lobster mounds, SO:-- concentrations are distinctly higher

as a result of pyrite oxidation. The increase in dissolved sulphate is balanced

mainly by Ca2+, MgZf and K', which were released by weathering of minerals and/or by exchange reactions with the adsorption complex.

The relative increase in SO:- is much stronger in the Pendam samples. The Pendam

subsoils are unoxidized, and pyrite oxidation, as evidenced by the composition of

the interstitial solution, indicates possible influence of water from the surface

soil.

The relatively slight increase in the concentrations of dissolved silica suggests

that silicate weathering is of little signicifance for the buffering of acid.

Much higher concentrations were found in acid sulphate soils in Thailand, where

HL,S~OL, generally occurs in equilibrium with amorphous silica (about 2 mmoles/l)

(Van Breemen, unpublished data). The situation appears to be different in the ana-

lysed Sarawak profiles, where it is probably mainly cation exchange reactions

that are effective in the inactivation of the sulphuric acid. To evaluate possi-

ble mineral equilibria, the analysed concentrations of the dissolved constituents

were converted into activities of uncomplexed species by means of a computer-pro-

gramme (Van Breemen, 1972).

In

standard free energies of formation (A G o ) of ferric oxide and of jarosite, assu- f med to be in equilibrium with the solution (cf.6).

The interpretation of E -measurement for ferric-ferrous equilibria can be criti-

cized on theoretical grounds (16, 5). However, experience with many samples from Thailand indicated that this approach gives meaningful results in terms of (a)

the degree Of supersaturation or undersaturation with respect to jarosite and (b)

the reactivity Of ferric oxides (Van Breemen, unpublished data). In the Pendam

with pH-EH data, ionic activities were used to calculate apparent

H

subsoils and in the fresh mud of the lobster mounds, the apparent A G: is close to A G: goethite (Table 7).

23

N r.

TABLE 6. COMPOSITION OF WATER SAMPLES (CONCENTRATIONS IN mnoles/l)

Depth +) EH +++) conduct. corr. mmhos/cm (cm) Type PH C 1 HCO, SO+ HkSiO+ K Na Ca Mg Fe Al Mn

SAMPLE DESCRIPTION

- I. 2. 3. 4. 5.

6.

7.

8.

9.

10.

1 1 .

12.

RAJANG I O

do. I O

do. ++)

do. ++) ::i do.") small pool O

RAJANG / PENDAM intermediate 40

do. 10

do. O

LOBSTER MOUND fresh mud O

do.

do.

-lo. do. 90

13. do. do. 80 14. do. do. 80

15. PENDAM'+)coconut 30

16. do.") do. 40 17. do.++) do. I05 IE. do.++) ditch O

LEW

GRW

LEW

GRW

SFW

GRW

GRW

GRW

LEW

LEW

LEW

LEW

LEW

LEW

GRW

LEW

LEW

SFW

-0.104 6.44 302 14.8 10.7 0.33 5.69 256 6.77 30.7 0.58 - - 6.55 289 2.94 14.4 0.28 5.61 246 6.43 28.4 0,007 -

0.163 6.23 199 2.21 10.2 0.24 3.85 171 4.22 18.8 0.010 - - 6.75 193 3.57 9.32 0.25 3.85 167 3.96 18.2 0.005 - - 7.15 174 4.79 6.87 0.22 3.47 150 3.39 16.1 - -

- 6.65 36.9 1.98 0.48 0.26 0.89 31.4 0.70 3.04 0.042 - - 6.25 53.9 6.94 0.88 0.235 1.89 49.3 0.97 4.46 0.272 - - 6.50 26.9 3.40 1.20 0.31 1.85 24.7 0.60 2.30 0.190 -

-0.156 6.57205 16.0 4.72 0.29 4.10 169 4.20 19.9 0.28 - -0.213 6.91 256 16.3 6.22 0.34 5.15 217 5.69 25.1 0.096 - 0.393 3.93 282 - 19.0 0.65 5.54 241 7.06 29.4 0.30 - 0.376 4.25 160 - 28.9 1.54 4.40 139 8.19 27.0 1.50 - 0.298 4.85229 2.0 15.7 0.46 4.58 199 5.80 23.6 0.225 - 0.525 3.22 235 - 17.7 1.03 4.64 200 6.99 24.9 0.42 -

0.087 -1.67 0.022 -1.97 0.017 +0.36

0.029 -0.85 - -1.88

- -1.15 - -0.19 - +0.05

0.032 -3.90

0.017 -2.90 0.063 -2.46 0.31 -3.72 0.17 -2.4

0.131 -1.19

- 4.10 0.161 - 0.47 0.205 0.028 0.154 0.248 0.119 0.113 0.079 0.005 +0.86 0.290 3.70 0.957 - 1.04 0.32 0.122 1.21 0.324 0.314 0.094 - 0.014 +9.06 0.075 5.85 4.18 2.26 5.18 0.38 0.560 10.2 0.764 2.19 0.021 - 0.017 -0.47

- 3.65 1 1 . 1 - 0.65 0.14 0.222 8.62 0.28 1.20 0.085 0.190 x) -0.43

31 .O 29.4

20. I 18.5

4.5 7.4 3.6

21.2

22.4 29.4 15.0 22.0

0.15 0.38 I .68 I .60

TABLE 6 . ( c o n t . )

19. do.

20. do.

21. do.

22. do.

23. d o .

24. do.

25. do.

26. do.

60

do.

do. 3 0

ditch O

27. SEA WATERxx)

GRW

LEW -0.071

LEW -0.042

GRW

SFW

LEW 0.235

GRW

LEW -0.048

SFW

6.30 6 .31

6 . 0 0 18 .4

5.19 9 .02

5.55 9 .34

5.70 35 .8

4 .20 2 .09

4 .25 1.13

5.67 14.4

8.15 555

3.21 0 .535 0 .091

3 . 9 0 0.50 0 .71

0 .902 0.63 0.15

0.307 1.10 0.11

0 .39 0 .69 0.19

- 1.37 0.41 - 0.66 0.32 - 8.2 0 . 4 2

2.65 28 .4 -

0.704 5 .23

0 . 5 0 16 .7

0 . 3 1 6 6.97

0.267 7.71

0 . 6 1 1 28.2

0.117 2.17

0.038 1 .03

- 16.6

0.225 0 .826 1 .28

0.81 2 .18 0 .03

0 .64 1.18 0 .12

0 .50 1.13 0 .25

0 . 7 3 3.64 - 0.323 0 . 4 8 0 .45

0 .23 0.25 0 .19

1.91 5.3 0 .19

- x) +6.5

- 0.022 -0.03 - 0.017 -3.09

0 .060 x) -4.35

- x) - 1 . 7 3

- 0.014 +11.5 0.021 x) + 4 . 6 - 0.062 -

10.0 475 10.4 54 - - - 0.0

0 .84

2 .60

1.25

1.18

4 .2

0 . 5 2

0.37

3 .3

+)

++) Samples from described profiles +++)

LEW = expressed from mud in the laboratory; GRW = groundwater sampled from auger hole; SFW = surface water

correction (expressed as % of anion concentrations) applied t o distribute any excess positive o r negative charge proportionally over cations and anions in order to obtain electroneutrality

present in concentrations < 0 .0015 mmolel1 x) xx) according to Garrels and Thompson (9 )

- not determined

] samples from the same location, profile, o r lobster mound

N v1

This indicates a low reactivity of the ferric oxide present, which is to be ex-

pected in a sulphide-rich environment, where most of the more soluble ferric iron

has probably been reduced and precipitated as poorly soluble sulphide.

TABLE 1.

AVERAGE VALUES AND STANDARD DEVIATIONS FOR THE APPARENT A G: FenOs and

A G: jarosite (IN kcal/F.W.) FOR DIFFERENT GROUPS OF SAMPLES

sample AG: Fe203 number of s amp les AG; jarosite

fresh mud lobster mound

interior lobster mound

Rajang soils

Pendam subsoils

Pendam topsoils

goethite

amorphous Fe203

jarosite

2 -175.620.6 -811.8+0.1

4 -169.921.8 - 7 8 8 . 9 ~ 2 . 5

2 - 1 7 0 . 4 ~ 2 . 9 -799.7+_4.9

3 -178 .7+1 . l -811.3+_3.1

-161.9

- 7 9 1 . 7 ~ 1 .O+)

+) Unpublished data by van Breemen and van Schuylenborgh

Probably as a result of the formation of limonitic ferric oxide upon pyrite oxidation, the Fe203 -reactivity is somewhat higher in the lobster mounds and in

the Rajang soils ( A G o

this reactivity will probably decrease until values near to A Go been reached, as is the case in the older Pendam topsoils.

The apparent A Go's for jarosite are higher than the theoretical value of -791.7 kcal/F.W. in the interior of the lobster mounds, suggesting that the mine-

ral is stable in this environment. Under all other conditions the values are low-

er, indicating that the soil solutions are undersaturated with jarosite. However,

in the Pendam topsoil where the typical yellow jarosite mottles are absent, X-ray

diffraction showed the presence of jarosite. Both the low apparent A G o and the mode of occurrence of the mineral indicate that it is actually unstable

and is being hydrolised to form ferric oxide.

Dissolved Al was analysed in f o u r samples. The available data are few, but sug-

gest that the upper limit of dissolved A l in these soils is regulated by preci-

pitation as AlOHSOh according to log (Al3+) + log (SO

keted

soil waters in Thailand ( 8 ) .

Actual concentrations are higher, depending on the ionic strength and the degree

Of complexing (in the four samples in question, between 2 1 % and 77% of total dis- Solved Al is complexed as Also: and Al(S04);).

Finally, it can be remarked that the observed manganese concentrations are low

(see Table 6), especially in the Pendam soils.

species refer t o activities), which was found valid for acid sulphate

Conclusions

From the results obtained by field and laboratory investigations the following

conclusions can be drawn:

1 . In the studied area pyrite-rich material is originally present only at depth

in the completely reduced subsoils. The Rajang soil is the modal t V e of the

und i ij t urbed pr of i le.

Through the activity of the mud lobster (Thalassina anomala), this material

rich in pyrite and organic matter is homogenized and brought to the surface,

where oxidation causes strong acidification.

This process is probably accelerated by the increase in surface area and the

homogeneous distribution of the pyrite caused by the comminution of organic

matter in the digestive system of the mud lobster. The fresh mud is charact-

erized by strong sulphate reduction and the presence of Fes. Although the PY-

rite content of the fresh mud is higher than in the Rajang subsoil, it is

well within the range normally occurring in mangrove muds and there are no

2 .

to assume any specific role of the mud lobsters in the formation of

pyrite. However, the FeS present may contribute somewhat to the acidification

of the soil material just after exposure.

The available analytical data confirm, the field evidence that the Pendam

SOi1 has gone through a lobster mound cycle. The sulphur-bearing minerals

stil1 Present in the topsoil of the Pendam profile and the strong similarity in mineralogical and elemental composition of the lobster mound and the Pen-

dam soil can be explained in this way.

The acidifying effect of pyrite oxidation in the mud flows is well illustra-

ted by the formation of jarosite and the accompanying strong increase in dis-

solved SO:- in the soil solution upon the transformation of fresh mud (repre-

sented by Sample 4 ) into the material making up the bulk of the lobster mound

(represented by Samples 5 and 6 ) . In the course of the transformation,the total

3.

4 .

27

S-content is reduced by more than half.

5. Although strong acidification takes place, the available evidence suggests that this does not result in intensive silicate weathering. Apparently the H+-ions released are neutralized mainly by exchange reactions with available cations.

Acknowledgements

The authors are indebted to the Director of Agriculture, Sarawak Government, for his permission to use data from an internal soil report (2). The Soils Divi- sion, Department of Agriculture, Sarawak, kindly provided personnel and equipment for the field investigations.

Part of the water analyses were carried out at the Laboratory of Semongok, Agri-

cultural Research Station, Sarawak, which also provided some analytical data, no-

tably on the pH of the fresh samples. The help of Mr. E.S.Sim, Assistant Direc-

tor Agricultural Research, is greatly appreciated.

Acknowledgements are also due to the Soils Institute of the State University,

Utrecht, for X-ray analyses of the fine silt fractions, to the Soils Laboratory of the Royal Tropical Institute, Amsterdam, for data on the exchange characteri- stics of the soil (Mr. H.A. van Rosmalen) and to the Laboratory of the Department

of Soil Science and Geology, State Agricultural University, for chemical analy- ses (Mr. L.Th.Begheijn) and X-ray diffraction of the clay separates ( M r . R.

Schoorl).

28

REFERENCES

ANDRIESSE, J.P. 1972. Memoir I. The Soils of West Sarawak. Government

Printing Office, Kuching, Sarawak. In press.

ANDRIESSE, J.P. and SIM, E.S. 1968. Report on soil investigations in the

proposed Sungai Sarawak Padi Scheme Area. 1st Division. Report No.125.

Research Branch, Dept. of Agriculture, Sarawak pp.27.

BEGHEIJN, L.Th. and SCHUYLENBORGH, J. van. 1971. Methods for the analysis of

soils. Department of Soil science and geology. Agricultural University,

Wageningen. 156 pp.

BLOO~~IELD, c. 1972. The oxidation of iron sulphides in soils in relation to the formation of acid sulphate soils, and O f ochre deposits in field

drains. J. Soil Sci. 23, 1-16.

BOHN, H. 1971. Redox potentials. Soil Sci. 1 1 2 , 39-45.

BREEMEN, N. van, 1969.

ox characteristics of flooded soils. Neth. J.Agric.Sci. 1 7 , 256-260.

BREEMEN, N . van, 1971. Methods of analysis. I. Ground- and Surface Water

11. Sulphur fractions in soils. Laboratory information Paper No.

The effect of ill-defined ferric oxides on the red-

3 * soil Survey Division, Land Development Department. Bangkok, 23 p p .

BREEMEN, N. van, 1972.

activities in natural waters. Submitted for publication in Geochim. et Cosmochim. Acta.

GARRELS, R.M. and THOMPSON, M.E. Am. J. sci. 260, 57-66.

Use of computer programming for calculating ionic

1962. A chemical model for seawater.

31

(14) Soil Survey Staff, 1951. Soil Survey Manual. U.S. Dept. Agriculture Handbook No. 18. U.S.Dept. Agric. Washington D.C. 503 pp. With Supplement,

issued May 1962.

(15) Soil Survey Staff, 1960. Soil classification, a comprehensive system.

7th Approximation. Soil Conserv. Serv. U.S.Dept. Agric. Washington D . C .

265 pp. With Supplement, issued March 1967.

(16) STUW, W. and MORGAN, J.J. 1970. Aquatic Chemistry. Wiley Interscience.

583 pp .

32

APPENDIX I . DETAILED PROFILE DESCRIPTIONS

Profile I

Rajang series - Fluventic Halaquept

Described on 19 .12 .1969

Location: See Fig.1; approximately 40 m from river branch. Soil drainage: Poorly drained; groundwater level at approx. 40 cm depth. Soil

surface is approx. 50 cm above normal high tide level. - Relief: Macro-relief flat; micro-relief generally flat, few lobster-mounds present.

Natural vegetation: Nipah (Nipa fruticans), out about two months before date of

description.

Samples: Sample 1 : 0-20 cm

Sample 2: 20-60 cm

Sample 3: 90-120 cm

Diagnostic horizons: Ochric epipedon; cambic horizon. Profile :

0-20 cm Grayish brown to dark grayish brown (2.5YR4.5/2) and dark

gray (5Y4/1) silty clay; common, medium, distinct, diffuse,

dark yellowish brown (lOYR4/4) and reddish brown (5YR4/4) mottles; weak angular blocky; common very fine to fine Po-

res; gradual, smooth boundary to

20-60 cm

60-300+ cm

(partly described from auger samples)

Dark gray (5Y4/1) silty clay; many, coarse, prominent, sharp,

reddish brown (5YR4/4) mottles occurring as I to 2 mm thick

coatings inside large (2-10 mm diameter) root channels; very

weak, blocky structure; many, very fine biopores.

(described from auger samples)

Gray to dark gray (5~4.5/1) silty clay; locally few pockets

Of greenish gray (5GY4/l) clay and common dark gray (5y3/1)

clay associated with undecomposed organic matter ; ripening

increases with depth to about 250 cm, below which it decrea- ses.

Remark: Groundwater has a distinct smell of H ~ S .

33

Profile 2

Lobster mound

Described on 31.12.1969

Location: See Fig.l; in transitional area between Rajang and Pendam soils.

Soil drainage: The site is artificially drained by ditches, but is still very

wet. Poorly drained. Groundwater level is at approx. 20 cm below

the land surface.

Relief: Macro-relief flat; micro-relief strongly broken due to numerous lobster

mounds covering about 30% of the land surface.

Natural vegetation and land use: Young coconut trees. Some remnants of the ori-

ginal nipah (Nipa fruticans) vegetation are still present. No levelling

had taken place prior to cultivation.

Morphology of the mound: The mound has an irregular base with a diameter of ap-

prox.125 cm. Height is 75 cm. The mound contains at least five lobster

channels. One mudflow, spread downwards over the mound, was freshly

deposited.

Samples: Sample 4: fresh mudflow

Sample 5: outer skin of mound (0-7.5 cm)

Sample 6: inner skin of mound (7.5-30 cm)

Sample 7: core of mound, above level of land surface (30-75 cm) Sample 8: core of mound, below level of land surface

Profile:

Surface:

0-7 cm

7.5-30 cm

Most of the surface consists of older, dry t o moist mudflows. Grayish

brown (2.5Y5/2) t o gray (N5/0) silty clay loam; the fresh mudflow is

dark gray (5Y4/1); approximately 75% of the surface shows a thin pale

yellow (7.5Y8/4) coating of jarosite.

Outer skin (measured from surface towards core of mound). Silty

clay loam, dry, becoming moist with increasing depth; heterogeneous

material consisting of both older and relatively fresh mudflows;

matrix colours as above; much pale yellow (7.5YS/4) jarosite on ped

faces and little within peds; common, medium, distinct dark yellow-

ish brown (10YR4/6) mottles; moderate to strong angular and suban-

gular blocky; very porous; gradually to

Inner skin (measured towards core of the mound). Olive gray (5Y4/1.5)

to grayish brown (2.5Y4/2) silty clay loam; moist, becomes wet with

increasing depth; many pale yellow (5Y8/2) jarosite mottles and very

34

few, fine, distinct strong brown (7.5YR4/6) mottles on ped faces;

moderate to weak angular blocky; many large pores; gradually to Core of mound. Dark gray (5Y3.5/3) to dark grayish brown (10YK4/2)

silty clay loam; pale yellow (5Y8/4) jarosite mottles mainly assoc-

iated with large pores (rootpores, or voids associated with pieces

of decaying wood); common, distinct brown (7.5YR5/1) and dark red-

dish brown (5YR3/6) mottles; structureless and massive.

30-75+ cm

Profile 3

Pendam series - Aeric Fluventic Tropaquept Described on 19.12.1969

15/20 - 32 cm

32-45 cm

Location: See Fig.]

soil drainage: Poorly drained; groundwater level at 40 cm below the soil surface. Relief: Macro-relief flat; micro-relief flat; land surface above high tide level.

Natural vegetation and land use: Coconut trees, 7 to 10 years old; Original ve-

getation, consisting of nibong (Oncosperma filamentosa) and nipah (Nipa

fruticans), was cleared some 20 years ago. Samples: Sample 9: 0 - 15 cm

Sample 10: 20 - 30 cm Sample 1 1 : 30 - 45 cm Sample 12: 80 - 120 cm

Diagnostic horizons: Ochric epipedon; cambic horizon

Profile:

- 2 - O c m

O - 15/20 cm Rootmat

Dark brown (IOYR3/3) silty clay loam; friable and slightly

sticky; fine to medium subangular blocky and medium to coar-

se crumby; many fine roots; common fine and medium biopores;

many earthworms; gradual, wavy boundary to

Dark gray to dark grayish brown (IOYR4/1.5) silty clay;

slightly plastic, slightly sticky; common, fine to medium,

distinct, clear, brown to dark brown (7.5YR4/4) and Yellow-

ish brown (10YR5/8) mottles along root channels and biopo-

res; weak, medium, subangular blocky; many fine, medium and

CoarSe biopores; many decaying root remnants.

(described from auger samples) Dark gray (5y&/]) silty clay; slightly plastic, sticky; few,

35

45-!30+ cm

medium, distinct, clear, strong brown (7.5YR5/6) mottles;

structureless, massive.

Olive gray (5Y5/2) and very dark gray (5Y3/1) silty clay;

many, partly decomposed plant remains; locally very mucky at

about 60 cm depth.

36

APPENDIX 2 ANALYTICAL METHODS AND FIELD DESCRIPTIONS

Soil samples

The determination of the particle size distribution, the CEC of the clay fraction,

the organic carbon, and the elemental analyses were carried out at the Depart-

ment of soil Science and Geology of the University of Agriculture, Wageningen, ac-

cording to the procedures outlined by Begheijn and van Schuylenborgh ( 3 ) .

Data on the exchange characteristics of the soil were obtained at the Soils

Laboratory of the ~~~~l Tropical Institute at Amsterdam. After washing with wa-

ter to remove water-soluble salts, the soil was saturated with Ba2+ by percola-

ting with 0.6N BaC12, washed with ethanol/water, and the adsorbed RaZ+ was re-

Placed by NH; with 1 N NH,+C1. This procedure was repeated with 0.6 N Ba2+ solu- tions buffered at pH 8.2 (TEA) and at pH 4 . 8 (acetate-acetic acid). Cations ex-

changed during the first percolation with BaC12, were analysed by atomic absorp-

tion spectrophotometry. The exchange acidity was determined titrimetrically ac-

cording to Mehlich ( 1 1 ) .

as described by Begheijn and van Schuylenborgh (op.cit.). X-ray data on the

analyses of the clay separates were carried Out

minerals in the silt- and clay fractions were obtained from Samples Sepa- rated centrifuging without the use of dispersing agents and H Z ~ Z .

37

1:5 or 1:lO dilution was made in 0.4% hydroxylamine-HCl to keep iron and mangane- se in solution.

Each sample was analysed for Na and K (flame photometry), Ca, Mg, Fe and Mn (ato-

mic absorption spectrophotometry), C1 (potentiometric titration with AgNO3, using

an Orion silver/sulphide electrode as end point detector), SO4 (turbidimetrically)

and HbSiOt, (colorimetrically with NH4 molybdate-HC1). If the pH was below 5.5, Al was determined colorimetrically with pyrocatecholviolet, applying an empiri-

cal calculation procedure to correct for Fe-interference.

For details on the water analyses see van Breemen (7).

Field descriptions

Soil and profile site descriptions were made according to the Soil Survey Manual

( 1 4 ) . The soils were classified according to the “7th Approximation” (Soil Survey

Staff ( 1 5 ) , 1967 supplement.

38

This paper deals w i th a case of acid sulphate s o i l formation inf luenced by mud lobsters bringing up s u l p h i d i c subsoil material t o the surface. I t presents and

discusses environmental, morphological and ana ly t i ca l data on the lobs t e r mounds and i n s o i l p r o f i l e s representing younger and older phases of soil formation. Special emphasis is given t o chemical composition of i n t e r s t i c i a l waters.

Resumé

L ' a r t i c l e pre'sente un cas de formation de sol sulfate' acide influence' d'une espdce de langouste remblayant l a surface avec du mate'riel sul furique provenant

-

sous-sol. ~a discussion e s t basée sur l e s données physiographiques, morpho Zo-

giques e t analytiques sur l e s monceaux de langouste e t p r o f i l s de s o l repre'sen-

t a t i f s . A t t en t ion spéciale a é t é prêtée d l a composition des eaux i n t e r s t i t i e l l e s .

Resumen

Se presenta un cas0 de desarrol lo de suelo de s u l f a t o s ácidos destacado por l a

act iv idad de langostas que acwnulan en la super f i c i e montones de t i e r r a sulfurosa sacado del fondo del suelo. Se funda l a discusión en datos ambientnles, morfoló-

gicos y ana l i t i cos sobre los montónes de langosta Y p e r f i l e s de suelo represen- t a t i v o s . Se hace hincapié en la composición del agua i n t e r s t i c i a l .

Zusamen fassung

Es w i r d e i n Fall der Bizdung su l fa t saurer Baden beschrieben, wobei der s u l f i d i s c h e Untergrund dur& cine A r t von Scha l t i e r hinauf zur Oberfläche getragen w i r d . Die repräsentat iven Bodenanhäufungen und - p r o f i l e , sowie Bodenbildung werden beschrieben und e r ö r t e r t auf Grund chemischer und minera logischer Daten, wobei

der Komposition des Porenwassers besondere Aufmerksamkeit zugewandt i s t .

-

39

J.P. Andriesse