GeolCarp_Vol50_No5_389

GEOLOGICA CARPATHICA, 50, 5, BRATISLAVA, OCTOBER 1999

389394

MICROBIAL ACTIVITY IN SOILS UNDER THE INFLUENCE

OF PYRITE WEATHERING

MARIANA VÝBOHOVÁ, ALEXANDRA IMONOVIÈOVÁ, PAVEL DLAPA and

MIKULÁ MADARAS

Department of Soil Science, Faculty of Science, Comenius University, Mlynská dolina, 842 15 Bratislava, Slovak Republic

(Manuscript received February 12, 1998; accepted in revised form December 9, 1998)

Abstract: The chemical and microbial characteristics of soils at seven research sites four affected by an acid

sulphate weathering and three intact, undisturbed have been investigated. The extremely low soil pH, the increased

electrical conductivity and high exchangeable aluminium contents are characteristic features of the affected soils.

These chemical changes were accompanied by the inhibition of the soil respiration and enzyme activities denoted the

microbial activity in soils. The small microbial biomass and the abundance of bacteria and microscopic fungi indi-

cated the worsening of living conditions for the soil microorganisms. In spite of this some representatives of micro-

scopic fungi (Deuteromycotina) isolated from the damaged soils gave evidence of their adaptability to the extreme

conditions.

Key words: acid sulphate weathering, soil acidification, microscopic fungi, respiration and enzyme activity changes.

Introduction

The quartzite quarring has been practiced on the obov hill

near Banská tiavnica since the year 1956. The waste materi-

al containing pyrite has been accumulated on a dump pile

next to the quarry. The weathering of pyrite leads to the pro-

duction of extremely acid and mineralized water solutions

within the dump pile. The acid solution with high concentra-

tions of iron and sulphatic ions has damaged soils and the

vegetation downslope. The soil acidification, the precipita-

tion of the characteristic secondary minerals, the destruction

of the soil structure, and consequently the absence of the

plant cover and the strong erosion of topsoils are the degra-

dational features on the slope of obov hill.

The first symptoms of the damage appeared in 1978. The

area of about 15 ha is influenced at present. The geological,

chemical and biological aspects of the affected territory has

been studied by a number of authors (Holub et al. 1991; Holub

et al. 1993; Kriáni et al. 1994a; Kriáni et al. 1994b; Forgáè

et al. 1995; imonovièová et al. 1996; imonovièová et al.

1997; Dlapa et al. 1997; ucha et al. 1997). The processes of

the acid sulphate weathering in the volcanic complex in

Vtáènik Mts. was described by Èurlík & Forgáè (1983).

The aim of this paper is to compare the microbiological

characteristics of the original topsoils with those affected by

the acid and mineralized water originating from the pyrite

oxidation. The soil microbial characteristics, like the soil res-

piration or enzyme activities, inform about the microbial ac-

tivity in the soils. In addition, the microbial biomass, the

abundance of bacteria and microscopic fungi, the occurrence

of microscopic fungi species and genera testify to the quality

of the soil environment.

Material and methods

The obov hill is situated NE of Banská tiavnica town in

the tiavnické vrchy region. The soils are Eutric Cambisol

(FAO) with transitions to Planosol, in depressions. Detailed

mapping of soils was done in the area affected by the water

leaking out from the dump pile. Seven sampling sites were

studied four influenced (P1, P2, P3, P4) and three without

degradational features (N5, N6, N7). The samples were taken

from the topsoils (020 cm) for the chemical and the micro-

biological analyses.

Soil samples were air-dried and fraction < 2 mm was taken

for chemical analyses. Soil pH values (H

O, 1 M KCl) and

exchangeable Al were determined using a soil : solution ratio

of 1 : 2.5. Total organic carbon was measured by oxidation

with K

and titration of non-reduced chromate.

Electrical conductivity was determined in the saturation soil

extracts, after allowing the pastes to stand for 24 h.

The microbiological investigation was realized with the

fresh soil samples. The soil fraction < 2 mm was used for

laboratory experiments.

The microbiological analyses include:

the CO

-evolution (the soil respiration) basal and po-

tential after adding 1 % of glucose (Kopèanová et al. 1990);

the enzyme activities: carboxymethylcellulase (CMC),

xylanase and saccharase (Schinner et al. 1993);

the amount of carbon in microbial biomass (C

bio

)

(Schinner et al. 1993);

the abundance of bacteria and microscopic fungi (Ko-

pèanová et al. 1990);

the composition of microscopic fungi species and gen-

era (Fassatiová 1979).

390 VÝBOHOVÁ, IMONOVIÈOVÁ, DLAPA and MADARAS

The number of repeated samplings (310) was chosen in

accordance with the methods used. The arithmetical means

and the mean deviations have been calculated and illustrated

in the Figs. 14.

Figures on Pls. III were taken on Scanning Electron Mi-

croscopy (SEM) model Tesla BS 301 by J. Blahutiaková (In-

stitute of Experimental Phytopathology and Entomology,

Slovak Academy of Sciences, Ivanka pri Dunaji). Before

that, the samples were air-dried and coated with gold.

Results and discussion

The chemical properties of investigated topsoils reveal

degradation processes as follows from Table 1. A drop in the

soil pH to about 3 is typical. The soil buffering mechanisms

are insufficient and almost ineffective because acid water en-

tering the soil profiles contains high concentrations of iron and

sulphatic ions (in contrast to acid rains with only very low

concentrations of salts). The salinity of saturated soil extracts

increases due to the dissolution of secondary minerals which

are formed during the interaction of acid water with the origi-

nal soil. Exchangeable base cations (Ca

, Mg

, and K

) are

displaced by Al

(Dlapa et al. 1997). The low nutrient status

and aluminium toxicity will cause the inhibition of all bio-

logical activities.

way from the plant or litter bioorganic compounds to the col-

loidal humic substances is very complex involving a number

of degradative and condensation reactions. These reactions

involve numerous enzymes, since non-enzymatic reactions in

soils are very slow (Lähdesmäki & Piispanen 1988). The first

components to be removed, by the combined action of mi-

crobes and leaching, are water-soluble compounds, such as

sodium and potassium salts and sugars. After these, more

complex substances such as starch and proteins are attacked.

Whereas many of these components can be decomposed dur-

ing a few months, more complex structural ones, such as lig-

nin or keratin, may persist in soils for several years (Gray &

Williams 1971). The enzyme activities saccharase, xyla-

nase and carboxymethylcellulase (CMC) from the carbon

cycle of organic matter circulation in the natural environ-

ment, were clearly detected. It has been observed that the

highest saccharase and xylanase activities (5 170.48 694.6

µg GLC· g

-1

dry soil · (3 h)

-1

and 648.03 522.5 µg GLC · g

-1

dry soil · (24 h)

-1

) are at the places N5N7, that is at the plac-

es without degradational attributes (Fig. 2). The saccharase

Fig. 2. Saccharase, xylanase and carboxymethylcellulase activities.

Fig. 1. Basal and potential respiration of microorganisms.

Table 1: Basic analytical data of the studied soils (P1P4 influ-

enced, N5N7 not influenced by acid sulphate weathering).

Sample No.

pH (H

pH (KCl)

µS . cm

-1

mg . kg

-1

3.0

2.8

2.61300

727

3.1

2.8

1.4

1000

506

3.1

2.9

1.7

2500

585

3.3

3.2

2.2

3600

832

6.0

5.0

2.1

300

N65.4

4.5

3.2

500

6.1

5.2

2.6

400

EC electrical conductivity of saturated soil extract

Al exchangeable aluminium (1M KCl).

The study of carbon cycling is necessary to understand the

functioning of the ecosystems. The carbon fluxes from the

soil and litter compartments to the atmosphere (collectively

referred to as soil respiration) are major pathways of the car-

bon cycle (Redmann 1978). The evolution of CO

is an indi-

cator of intensified processes of organic matter decomposi-

tion in the environments (Kubicka 1973). The carbon dioxide

output of soil samples reflects the overall metabolic activity

of the microflora in soil (Gray & Williams 1971). The high-

est values of CO

-evolution (112.0 and 73.8 mg CO

· kg

-1

soil · (24 h)

-1

) were measured at the chemically undisturbed

places N6 and N7 (Fig. 1). The potential soil respiration (the

respiration after adding of glucose as the source of energy)

was more intensive than the basal soil respiration in all sam-

ples (Fig. 1). Such results testify to the fact, that the quanti-

ties of available nutrients had a direct and the greatest influ-

ence on the activity of microorganisms.

The soil microorganisms play a very important role in the

decomposition of dead organic matter. The chemical path-

200

400

600

800

1000

Sample No.

mg CO

/ kg soil / 24 h

BASAL RESPIRATION
POTENTIAL RESPIRATION

1000

2000

3000

4000

5000

6000

7000

8000

9000

Sample No.

mg GLC / g soil

CMC (after 24 h)

xylanase (24 h)

saccharase (3 h)

GLC - glucose equivalent

392 VÝBOHOVÁ, IMONOVIÈOVÁ, DLAPA and MADARAS

and xylanase activities were explicitly different between the

groups of the unaffected and the affected topsoils. Their mea-

sured values were higher than those of CMC activity. Low

CMC activities were observed at all places (37.4303.9 µg

GLC · g

-1

dry soil · (24 h)

-1

). The differences between the

studied groups of undamaged and devastated soils were not

ascertained (Fig. 2). It is known that the decomposition of

cellulose is rather slow in the soil, whereas, sugars, carbohy-

drate polymers as well as starch, pectin, and hemicellulose

decompose more rapidly (Lähdesmäki & Piispanen 1988).

A large amount of energy within the soil is accumulated in

the form of humic substances, plant tissue residues, and as

microbial biomass, too. The microbial biomass is important

in the cycling of matter and energy and it determines the

character and the intensity of biological processes within the

soil (Bernát et al. 1984). The amount of carbon in microbial

biomass (C

bio

7.214.3 mg · (100 g)

-1

dry soil, Fig. 3) and the

abundance of bacteria (0.01.4 · 10

CFU · g

-1

dry soil,

Plate II: Fig. 1. Penicillium sp., (Deuteromycotina), 1600

. Fig. 2.

Penicillium vulpinum, (Deuteromycotina), 40

. Fig. 3. Chaetomium

sp., (Ascomycotina), 90

Fig. 4. Bacteria and microfungi abundances.

Fig. 3. The amount of carbon in microbial biomass.

100

120

Sample No.

g / 100 g

oil

P1 P2 P3 P4 N5 N6 N7

Sample No.

10000 CFU / g soil (bacteria)

10000 CFU / g soil (microfungi)

bacteria

microfungi

MICROBIAL ACTIVITY IN SOILS UNDER THE INFLUENCE OF PYRITE WEATHERING 393

Table 2: Species and genera of soil micromycetes observed in the

studied soils.

Micromycetes

Sample No.

P1 P2 P3 P4 P5 P6 P7

ZYGOMYCOTINA

Absidia sp.

Mucor sp.

Zygorhynchus sp.

DEUTEROMYCOTINA

Acremonium sp.

Aspergillus sp.

Aureobasidium sp.

Cladosporium cladosporioides

Cladosporium macrocarpum

Geotrichum sp.

Paecilomyces sp.

Paecilomyces lilacinus

Penicillium sp.

Penicillium vulpinum

Verticillium sp.

ASCOMYCOTINA

Chaetomium sp.

Fig. 4) determined at the affected places (P1P4) were of

lower values in comparison with those at unaffected places

bio

43.7101.3 mg· (100g)

-1

dry soil, the bacteria abun-

dance 18.433.6 · 10

CFU · g

-1

dry soil). The abundance of

microscopic fungi (Fig. 4) was comparable in all samples

(0.8 6.3 · 10

CFU · g

-1

dry soil). The sensitivity of micro-

scopic fungi to decreased soil pH is lower than the sensitivity

of bacteria (Holub et al. 1993).

Fifteen genera and species of microfungi were isolated and

identified in the studied topsoils (Table 2, Pls. III). The high-

est number of genera and species was isolated at the places N5

(6), N6 (6), and N7 (8). The representatives of classes ZYGO-

MYCOTINA (Absidia sp. Tiegh., Mucor sp. P. Micheli ex St.-

Amans, Zygorhynchus sp. Vuill.), DEUTEROMYCOTINA

(Acremonium sp. Link ex Fresen., Aspergillus sp. P. Micheli

ex Fresen., Aureobasidium sp. Viala ex Boyer, Cladosporium

cladosporioides (Fresen.) N.F. de Vries, Cladosporium mac-

rocarpum Preuss, Geotrichum sp. Link ex Léman, Paecilo-

myces sp. Bainier, Paecilomyces lilacinus (Thom) Samson,

Penicillium sp. Link ex Fresen., Penicillium vulpinum

(Cooke et Massee) Seifert et Samson, Verticillium sp. Nees

ex Link) and ASCOMYCOTINA (Chaetomium sp. Kunze ex

Fresen.) were determined. The representatives of the class

Zygomycotina exist in the topsoils and they require sufficient

amounts of easily decomposable organic substances. Their

absence reflects the insufficiency of soil organic matter and

the deterioration of decomposing processes at the places P2

and P3. Penicillium sp. and Cladosporium cladosporioides

of the class Deuteromycotina were found at almost all af-

fected places. The survival of the representatives of DEU-

TEROMYCOTINA under the physiologically extreme con-

ditions confirms their high adaptability to the adverse soil

environment.

Conclusions

The observed degradation processes represent the extreme

case of soil acidification. It has been found that the chemical

deterioration within the investigated soils (extremely low

pH, high contents of exchangeable aluminium) was accom-

panied by significant changes in the soils microbiological

properties. The inhibition of the microbial activity, as the soil

respiration or the enzyme activities, was observed in the soils

influenced by the acid sulphate weathering. The microbial

biomass, the abundance of microorganisms, as well as the di-

versity of microscopic fungi genera were reduced in the af-

fected soils, too. Only tolerant groups of microorganisms

survive in the chemically degraded soils on the slope of

obov hill.

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