Carbon dioxide in cave atmospheres: new results in Belgium and comparison with some other countries

I

|J</

5rc

EARTH SURFACE PROCESSES AND LANDFORMS' VOL' 1O'

I7}I87

(1985)

CARBON

DIOXIDE

IN

CAVE ATMOSPHERES.

NEW

RESULTS

IN

BELGIUM

AND

COMPARISON

WITH

SOME

OTHER COUNTRIES

CAMILLE EK'

Laboratoire de Géomorphologie et de Géologie du Quarernaire, I)niaersité de Lièle, Place du 20'Août,7, 8-4000 Liège' tselgium ÀND

MICHEL GEWELTI

Centre d'Etüe de l,Energie Nucléaire (CENISCK), Mesures Bas-Nioequx, Boeretang,2æ, B-24A0 Mol, Belgiun-r

Receiued l5 December 1983 Ret:ised 24 MaY 1984

ABSTRACT

More than 600 measurements of the carbon dioxide content of cav€ air in Belgium lead up to the conclusiotr that the maiu factors of

is

distributlo"

uii,

(l)

a flow originaüng from the biomass and diffusing in the soil and the voids of bedrock;

iZj

_"

tr*0,

discernible io

r..y

tiiU air only,io go dôwa by density; (3) in some caves, draughts caused, for instaoce, by a

swift underground strealn.

Results in-Belgium are càmpared with published and unpublished data.from other countries, sbowiog tbat

Co,

is often less abundant

ii

cold climati caves and io caves of semi-arid regions (iafluence of the biomass).

ip*i"flrt.Dtion

is paid to human coûtamitration during analÿses: tbe influence of people passiog through the cave

o."iUy

tÀe operator, but aiso tbe influence of the operator himseif are discussed, and the use of special precautions (incluâing a ôOr-absorbing mask) in defioed critical situations is stresed.

KEy woRDS carbon dioxide caves Human contamination seasonal variarions

INTRODUCTION

Carbon dioxide

is

ol

paramount

importance

in

lirnestone solution.

Although

the

action

of

other

acids is neither igaored nor unàerestimated here, it is obvious, at least in temperate and cold regions, that carbonic gas is

in

most cases the

prime

mover aDd the

main

agent

of

carbonate dissolution.

Carbon dioxide in water comes either directly

from

the air or from the metabolism of the

biomass-and in

this

case

also,

oftdn

througb

a

gaseous

phase-hence the primordial interest

of

knowing

the

CO.

concentrations and movements

in

the limestone environments, Particularly

in

cave air,

in

soil

air

and

in

the lowermost atmosphere.

More

than 600 measurements

of

carbon

dioxide

have been carried

out in

Belgium,

all of

them carefully

located

in

space, time and weather conditions. 'ÿ/e

try

here to summarize

in

a few pages the main results

of

these analyses and

to

compare them

with

some other studies of carbonic gas

all

over the

world.

'Cbcf dc travaux.

t Rcscarch fi5si5rrn1 National Fund for Scicntific Rcsearch (F.N.R.S., Belgiun)'

019',7 _-933't

_lïs

I 02017

3-t

ssoi.50

':r.1 ,.):r : a:.\ ,;::i r,r _{1 ::i :::: ri .1j

,]

.ri 174 C. EK AND M. GEWELT

METHODS

AND

TECHNIQUES

M e t hods

of

me asureînent

A1l

our

recent measurements are done

with

a gas pump detector

(Bendix-Gastec).

The Gastec detector tubes (2

LL

or

2 L) give a direct reading of the CO, conceutration in the air

(ppm/vol).*

Before, an electrolytic field device had been used

(Koepf,

1952;

Hilger,

1963; Delecour, 1965; Ek

et al.,l961;Delecour et

al.,196g).

This system, based on the electrolysis of a NaCl solution which had absorbed

CO,

is more precise (

t

0.1 mg

Co2ll

i'e-

_-

60 ppm: Ek, 1981) but heavier and slower. Thus,

for

field invesrigation, the Gastec pump sysrem is more useful: it is very light and only 2 or 3 minutes are needed for one measurement. The minimal precision,

guaranteed

by

the manufacturer,

is

t

25 per cent

but

it

seems

that

the effective precision is better and the

reproducibility

of measurements

is

+

10 per cent (Ek et a1.,198

l).

When

*e

.*pr.si

the results in ppm/vol, we

refer

to

the Gastec detector measurements.

For

older measurements done

*ith

the electrolytic

metiod,

we keep the expression of the results in mg COr/1. The equivaleuce depending among other things

or

temperature

is

about

0.18

mg/l:

100

ppm/vol in

TpN

conditions.

Precaut ion dur ing the meosurements

With

respect to

the

human breathing

out CO,

(about 4&103 ppm:

Miotke

1974),itis

very

imporrant

to avoid human exhaiation during the measurements. A carboo dioxiàe absorber system has been systematically used when measuremeDts have been

carried out in

fissures,

joints,

and confiaed atmosphere..This system, described

in Figure

l,

is composed of a plexiglas _{surrounding wall in the}

_form

_{of a}

y

_branch,

_with

_{two valves}

of

large diameter (

_-

2'5 cm). The

inlet

valve opens to the cave air, and the air breathed in and out is ejected

through the outlet valve into a stainless steel reservoir filled with soda lime. The exhaled

CO,

is then

abàrbed

by this soda lime.

A

rubber mouth

piece-coming from

a

snorkel-is

fixed to the plexiglas-surrounding wall

and a nose

clip

obliges the operator to breathe by the mouth. The rubber mout-h piece

cÀbined

with the nose

clip is more

comfortable

than

the'total'

nose and mouth mask we used before. TÀe necessity of using this

CO,

absorber system is evident and

will

be demonstrated later. In the same way, we do

not

use acetylene (carbide

lamp), but only electric light during

analyses.

RESULTS

AND

DISCUSSION FOR

BELGIAN

CAVES

.Fusures uersus larger passages

Cave

air

generally contains more carbon dioxide than the open atmosphere. Under temperate conditions,

the

CO,

Pressure

in

the caves is generally _{two to} twenty times higher

tharrin

open air,

.o-.ii*.,

more. In the caves, the

first differentiation to

appear

to

the air-analyst is grossly related

to

the

width of

the cavity: the fissures generally

display

a higher

CO,

content than larger passages, namely galleries and chambers.

In

the

Trou

Joney, at

Comblain,

a very shallow cave, values

of

7'8 and tb.6 mg COr;1

at

(approximately 4300 and 5900

ppm)

measurqd

in

ûssures

in July

1966 were

3

or

4

times

higher than the nài,r"r

displayed

by

the passageways (Ek er

a/.,

1968). Similar observations were carried out

in

Poland (Ek el a1.,1969).In

Brialmont

Cave and

in

Ste-Anne Cave, both at

Tilff,

fissures have a higber

CO,

content

üan

the respective passages

of

these caves (see

Figure

3).

In Rochefort

Cave, the

pCO,

is

diminishing from

rhe fissures to the

bulk of

the

atmosphere

of

a large chamber,

_{The Hell, both in May}

_{and September (Figure 2). The strong gradient}

_of

pCO, at

the

outlet

of

the fissure seems

to

indicate

that

the carbon

dioxide

diffuses

from

the crack

into

the

chamber (Delecour

et

a1.,1968;

Ek,

1969).

Some fissures do

uot

display a high

pCOr.

But, ahtrough not universal, tbe distinction between fissures and

rTo _{convert the CO, cooceotration (in ppm}

by volume) into partial pressure (pCO, in atoosphere), rhe following expression can bc used:

pco2 (in "t*.y =

pp-

co'l-!P1Pot'-r'')

'

76&106

where: Pahos.

:

baroneuic presstue (in rrm Hg)

Pw

= lvater vapor prEssurc (in mm

figi

t75

CARBON DIOX1DE IN CAVE ATMOSPHERES

BUBBER F MôurxptEce INLET VALVE SODA LIME PLEXIGLASS SUBFIOUNOING WALL OUTLET VALV€ sÈrRal SPRING BBEATHING IN BBEATHING OUT

5

tocm

æ

APPROXIMATE SCALE

l

I

t

Figure 1. COr-absorbing device used in confrned

tt*'

_{lti;:ti*ï;::rtJ"lhe}

op€rator Pass€s thtoush soda lime before being

Figurc 2. Co, ütraüons ir the air of .Thc Hell,, a large chambcr in Rocbefort Cavc. Cross-section showing sampling locatioûs and

Co,

mea:rursrDeûts of May 12, lg66 and

#;;;;

,'3-,-isi-9

rl"difi"d

from Dclecour et al'' 1968)

larger passages is very general,

particularly in

shallow

or not too

deep cave§'

In

Belgjlm.' most

accessible

fissures are in the upper part o[the galleries

an;

p"rræt',

*a

thus'

as

for

fluids' there is likely to be a possible

connection between tbe

soil

and the

""r..

rirrlî,ot"üty

t*pt"ios'

for

instance'

that the gradient of Co2

THE I{EIL- CHAMBEF IN FOCHEFOFT CAVE

a

Focx deorls

i'16

c. EK AND M. cEtilELT

litÏî

tLïi"[lild

the main passases is steeper in Brialmont cave (a _{very shallow cave) rhan in sre-Anne,}

Flow of

carbon dioxide

_from

_{the surfoce soil}

As shown

in

Figure 2' the maximum

_pco,

_{is observed,}

_in

_{the cave}

considered, _{in a fissure connected}

_with

;ïj::ïj.r:iïil:io..ol

doiine.

ni,

_r"",,

_and

the;,;;;;

_{gradient,n"*,}

","ir,

ngure rrom the

The observations _indicate

_that

_co,

is coming through the cracks

from

the soil,

from

which biogenic

co,

originates' This is corroborated _uy

_*ui.r

_uo"lysis

(Ek, i96gr

;;,.ations

of 32 underground _{seepage lvaters} allowed the calcuiation of

pCo,

tr"o

"titptere

in

equilibrium

witn

these waters:

_riis

_{pressure is r0 to 30}

Iîî.|,i::ïi:::.":ï'pbo,

i'

op'o

ui.

rt

i,

ir,

_ri

s"r-;-;;!.i","uy

_not

_t*"

oruoa..g,ouoa

_{rivers, but}

_it

Asim,ai.oo.,u,,ll',T.:id:iiTrJ:tr"i?üri."ïHî#,ii,ï;:::riru*:;:*J:;;

abundance in caves' Yet

in

1937,

Ad;;;;;

_swinnerton

_h;r;;;*,

that the

co,

coutenr in rhe

so,

is 25 to

90 _{times the amounr}

_{of CO,}

_*r.aü

fou"d in

the armosphere. Since then' a great

_numbeiof

_co,

_{..urrrr.*e,ts}

have been done in the _{soil atmosphere, in varied edaphic}

environments'

_A

_{lot of}

_parametett

_(toiiivp.,

temperature, rvater content,-level

_of

_biologic

_activity,

_etc)

are

involved in the

co'

production _ln

_toit-

_üJe

references oo ,hu,

_-"u.r

_{can be found for}

exampre in:

Atkinson

(197't);Bakaiowicz(1979tBôgli(19;r'is76),.o"r.r

r,'i.tt-iiiiiî.,,,,oor",o/.(r983);Garimov(r966);Haas

;Ïï:,i'i,iïô:'

(1e'77);

uioit.

(r'gz+l;

_Ni"od

_{(re75);pa;",,.,}

rrgzgl;

n",Jir.j,i+, \,ste,

rstsl,Russer

Seasonal euolution

The biogenic _{origin of most}

_co,

induces a seasonal _{variation of its pressure. This}

was _{shown by Ek (1979)}

but

was already suggested

n

_yy-'i

_,L

_ilotl'

_rrr.

first crear

uJrtutirti""lly

_{significaut coDfirmation of this}

lact

was _{given by Gewelt and}

_Ek

_(lggii

ltr§trualry slgnlncaut co

Figure 3 shows the differences _{beiween the}

_pco,

figures ofJanuary and _{september obtained in two fissures,}

in

a wet passage' January.and _september

"";;;'.;"d

,;r*rr.i;1,

the

minimum

aud maximum varues in

i:i:lii:iiÏ'ï.o3§:HÏï,if

ir","

ptàces,

tn"to,

_p.É,,,,,.,

_observed

in January are arways ress

-i:iffliiï'Jîi::ïïiffi'.t;utiu§te-Anne

cave and _{Briarmont cave}

_in

_{re82 and}

re83. Most

of

The seasonal evolution

_of

_the p-assag"rr"y,

_{i. lu*trated}

in Figure 4, which shows that

in Brialmont

cave, lying a few metres beneath the soil

t"rriâiil.

_co.

_content;f

_,Ë;;

begins to

io"r"u*

io

iîro.

"oa

disprays a

maximum

extendilg

through

_tle

_wtrote

_sumi.r,

_*i.r.",

in

ste-Àni"

_{cave, lying some eighty to one hundred}

iili:iî:hl:î#"ï"Jffilf:::',

the increase in

co,

p,*,,."

_i,,ro*

_{ana rJaasio}

_iui

_*"io

pu,sases to a

In

the fissures' the

fact

tÀat the

_{flow of}

_co,

_{is coming}

_from

_the

soii is obvious

if

one considers

that

the

maximum

pressure

_{of CO,}

_{is earlier}

in Brialmont

Cave

ilaa

beneath

_in

_{Ste-Anne Cave,}

_but

_moreover the

maximum is displayed _{earlËr in}

_tn"

_nrr*À

_oithe

uppe, leu"r

orn.i"r-onr

cave,

Fl

and F2, than in the cracks

F3 and F4 of

the lower level

_of

_{the same}

""r"

1o.

Figure 5).

The

_{diffusion of CO,}

_{is schematicatty}

iliustrated by

Figure 6.

Vertical

_{dffireruiarion}

In

a single room or

lulltry.:lt pco,

is frequently higher near the roof

-than near the ground.

In

this case, there is no static density

equilibrium

_{(éô.ir o.nr"itu"ï}

"it;;;;;

gradienr is an

invÀe

density gradient. This

kind

of vertical

distribution

".

tàot

iir'

Ek et

ar.rrôoa,

rxàjmay

be

related;it.,

_*rtu

_remperarure,

with

air

blow'

or with

_{humidity. Th.}

_fl;;rrirg

_{rro,,_tÀ.}

_*it

i, p.irrrp,

wanner and above

a,

richer in

Co,

which

_{explains the high}

_pco,

_obsetueà

"""r

,rr"

ceiling.

rni,

pn.io*enon

of soil

co,

coming from

thJ

fractured

upper zoue _{is ciearlÿ}

_,no*o

_i,

_flgur"

Z.

C.ARBON DIOXIDE IN CAVE ATMOSPHERES

Ficure 3. CO. titradons in Ste-Anne Cave. Cross-section of the main passage, 340 m east of tie entrancc, showing sampling locatioos

,oà

obs"rred values in January and September. Squares refer

to

CO, measurements, triaDgles to temp€rature and moisture

measurements. The cross-section is somewhat schematize4 all points being not really in a vertical plane (after Gewelt and Ek" 1985)

For

example

in

the Comblain-au-Pont cave (Figure 7), the

pCO,

increases from the entrance to the bottom.

Nearby the

entrance

of

the cave,

the CO,

content corresponds

to

the

normal

open

air

vaiue (330 ppm),

afterwards the

pCO,

increases to the bottom.

An

inversion was found in the little chamber situated 3'5 m over

the bottom: the higher

CO,

content

in

this

zone

may be due

to

the diffusion

or

also

to

the

confined

morphology of

the

little

chamber (Delecour et

al.,

1968;

Ek

et

a/.,

1968)-The

general downwards increasing

CO,

gradieut can be due

to

an accumulation

by

gravity.

This

phenomenon can also be reinforced by a thermal inversion which catches

tle

air near the bottom. Referring

to

the Figure 8 where the temperature variations (in " C) and relative humidity (percentage) are shown duriug one year

in

Ste-Anne and Briaimont caves,

it

can be seen that there is a thermal inversiou

in

the main passage

of

Brialmont cave rhe whole year long. The cold air is always caught near the bottom of the gallery (G6) and the

warner air is

located near

the roof (G7). This thermal

inversion

is

more

important during

the summer (difference of 2.5'C) and is accompanied by a

CO,

stratification which can be seen in Figure 4

(G6-G7)

and

Figure 5 (F1-F2,

F3-F4)

(Gewelt and

Ek,

1985). The thermal inversion blocks the CO2 and the colder air in

thè lower passage.

A

measurement done at

mid-heig}t

(September 30, 1982), between G6 and G7 shows

that

the richer

CO,

layer is not only located near the bottom

but

also in the half of the height of the gallery. Thus the downwards

CO,

increasing gradient

is

related

with a gravity stratification,

accentuated

by a

thermic inversion. This may be a normal situation

in

caves where

air

circulation (and

ventilation)

are reduced and where stratificaüon is possible. Vertical caves are

probably

a better

trap for

COr.

t17 J u u J cc U |-3 U dl F I

I

_U I

StE ANNE CAVE-CFOSS SECTION AT THE

.LITTLE

_OPPOSITION" c ITTLE OPPOSIT .LABOfIATOFY. UNDEBGFIOUNO FIIVEF R2 Fil 28oo-7ooo o I CO2 M€ASUREMENTS(pPmlvol.) liJSiUS:{??,?%??"" ÿ Td.Tw MEASUÊEMENTS

178

C. EK AND M. C]:WELT

GALLEFIIES

SEASONAL

_CO2

_VABTATTONS

tN

29 26

30

!à

I

9zo

02

22

2go2 !.

--.,

qi

; <

H

30

28 25

c>ur

<t

=oS

)

21

29

04 N?

6-_.o

<ît

)=

28 ?', @ 2 1 Figure 4. Sۉsonal _{cvolution of the CO, couteat}

of _{the main passagcs of} Ste-A

underground river; G: dry Dassq"*.- ,É^r:a-r

.

^oo" aad Brialoont Caves.

un _{derground river; G: d.y}

Àoe"*"i

t."ain J - ri._.

_{àXïffj.,.rËfi}

_Bi!) R: wet passage: the

In

Figure g

_it

_{can also}

be seen _{rhat the relative}

_humidity

in Ste_A 100 _{per cent)-}

_rhis

shorr ranse

_{mry u,}

"or..r"t"d

;il;,;il:î*."ï;ï:

;"3rir:î::lrî:rïï,rg:i;

with

the presence

_of

_an

_undergt'"'a

l,.r-

.Driqqlrc

;;i.,

_"îrLg*s

arso

to

ttre

saiuration

_of

_{the cave}

::ff::li:*x"'fi:iî:îi',î:1ji*fffi'.î{#rjiîyi:ll*me

variab,e (rrom

_er

_,"

_16r;;;

Horizontal gradient

Éf.iiiilâiffi*î1:iÎklïH,î,l#v

observed in horizontar caves.

rhis

was shown _{ror the nrst rime}

more

abund*,

,L*",a,

_{,h;",a"î#ffiiîJ[]ï..."*fi::î:i""",:,::1ii*H**"mes}

_{more and}

The same phenomenon' _but

above

ii.

ârir"",

;;

_tfu;

R#fir"nu.p.

_{cave, is snorun}

in

Figure 9.

co^

contents

_of

_{air 20 cm above}

_*"æt

_{tr'"iî.crllr.,}

rro*

tÀ.

;;;Ë0.

_{exurgence. The}

wa."r is in equ,ibrium.

Ëi!,i*,:*Jiï::i*

*r"'

iu"

J,"i*.rges

rrom

th.

,;;;;

enteis

in tn"

".o,,iüre

passage or rhe

Htiîî*Ïi1ï,",','ff

:jï,i,

_iîjff

ffiî:î.'.',ïï;ilg

j;*l;*iisr,'î#*H;*"H",m

An

example

_{combining tn"}

_t*o

_r""ü"

&orirooor

_{gradient and}

_co,

_supply

by _{underground river to} caye

SEASONAL

CO2

VABIATIONS

lN

FISSUHES

CARBON DIOXIDE IN CAVE ATMOSPHERES _1'79

Figure 5. Seasonal evolution of the C0, conæot of the ûssures of Ste-A.nne and Brialmont Caves. Eacb liae is the mean of the measured values in two adjacent ûssures (modiûed from Gewelt and Ek, 1985)

air) has been found in Ste-Anne cave by Gewelt and Ek (1985). Referring to Figure 10 where 27 measurements

carried

out

on January

7,

1983 along the

main

passage

of

Ste-Anne cave are reported, an increase

of

COz concentration in cave atmosphere from the entrance to the end ofthe cave can be observed. Linear regression 3

is calculated with all the measures. The correlation coefficiert, r

₌

0'96 is very high and gives evidence of the existence of a positive linear relatiou between

CO,

content and distance from the entrance. This phenomenon

can frrst be correlated

with

the decrease of the ventilation towards the end of the cave. However,

it

can be seen

in Figure

l0

that trrvo measurement clusters are distinguishable and that they are separated by a threshold

of

about 800- 1000 ppm. This first group of measurements is located near the entraoce aud corresponds to the

dry

part ofthe

cave. The

pCO,

increases

from

300 (free

air) to

1500 ppm

at

160 m

from

the entrance. The

correlation

coefficient

(linear

regression

l)

is

r

:

0'83.

For

the

second

group

of

measurements (linear regression 2), r

₌

0.89 and the

CO,

concentrations are higher towards the sump (end of the cave).

It

is very

interesting to see that the threshold between the two groups of measurements corresponds to the vanishing

of

the underground river

into

the lower passage of the cave. Tbe CO, content is maximum (3200 ppm) upstream then decreases downstream and, when

the underground river

disappears

in

the

lower gallery, the CO,

concentration falls

down

about 80G-1000ppm and then continues

to

decrease up

to

the entrance.

One might assume that the progressive lowering of CO, content of the air dowDstream shows variations

of

equilibrium between air and water. There is no doubt that the underground river is a purveyor of

CO, for

the

21

29 04 26 30

2A 2sO2

22

29û2

30 29 26 30

2A

q ü

Ë

tËi

q

r

E

à

s

q f>-)

180 C. EK AND M. GEIilELT MAX

''l'nll

o

§ii$

#l/

r/il

coz

Figure

_6'

_schematic

cross-section _{of ste-Aare}

_ad

_{Briata:,*ffi"iIlmî*diffusion}

of carbon dioxide, ."

r.""",o

b, ,h.

Figurc 7. Cross-scction _from .The

Shaft, of Comb&ria_au_p.",

*-ll

e'rarcc

"

;i:i.(Hffl#:,",?

,iff**"

læsüons. pCO, incrcascs from

",ï:iÏï1ffi"-I"i'ff

üTffi

LYJ'.îiif*:i:;i..:tl*:rhisco,suppryrromthewarer

just

_{above the}

_water

_tt""

_roo;ffiui'ë

Figure

l0).

the waær

ter"t:

pôor'is

gènerally higher

Contaminations

some _{measures we have}

used

_{for constnrtion}

_{of Figures}

4 and 5 are too

hig!

because

co,

_contaminadon has been identified-

_For

_more

_det'ils

"uour

G n"t*"I*"-LiJà;

previoù

p";;G;rt

and Ek, 1985). '7HE SHAFT- ôE

co- uet-arN-aulàÀ,r

cAvE

- -N

HEtcHT _{ABovE BoTToM}

§swNrf*...i\i-CARBON DIOXIDE IN CAVE ATMOSPHERÊS

æ 25o222

290,2

§

29 2C 30

28 181 I H.o/o 95 90 85 80 75 70 65 Td oc 20 18 16 11 12 ,o

r3\i

TE

EiE2

29 (rl (D

i

-r

o É

Figurc g. Seasonal cvolution of thc rclative humid.ity asd &Epcratuæ in Sæ-Anne _?.d Brialmont cavcs. Thc hachured zooe shows the

thermal invcrsion in Brialmont cavc (after Gewelt and Ek, 1985)

Figurc 9. Evolution of CO, content of air 20 cm abovc watcr lcvcl bctwecn thc sump and the cxurgeoæ iD lbe RetnouchâmPs cave. The

r82 ppmC02 (Vot.) 3200 3000 2800 2600 2400 2200 2000 1 800 1600 1400 1200 1000 800 600 400 200 C. EK AND M. GEWELT

StE

ANNE

CAVE

CO2 _{MEASUBEMENTS ALONG THE}

PASSAGE _{(JAN. 07,I983)} MAIN_o

ar

---(.'-2

a

r,2,3: LINEAB BEGBESSION

. _{h:i6O cm} r h! lOcm + DBY PaSSAGE ++ _{UNOERGBOUND FilvEH +}

SUMP

160

24O

32O

4OO

48O

DISTANCE FÊOM THE ENTRANCE

Figure

l0'

Horizontal evolution (2)

y:

Z.e

x

+17t9.7 of

co,

(r cootent ₌ 0.89); of (3) air

_r=

in 5.3 ste-Aqne cavc. Linear

x iSor.l

_1r=b.X1 (after regressions: Gewelt and

(l)

y:

Ek,

q.l x

1985)+4g4.7

(r=

o.g3);

v/e just want to

show here some examples

_of

the

control of

_{human breathing on}

_co,

_{measurements.}

Conlamination due

to

the

operator

:

The

following

examples

_will

_{prove the necessity of carrying}

_out

_co,

measurements

_with

_{a gas absorber} system,

particularly in

confined atmosphere, like fissures

"oir"ry

narïow

galleries.

-In

₃₈₀₀

ste-Anne

_{ppm' In}

cave _the (september 26, 1982),

a

measurement done

in

a

fissure

_with

the

co,

absorber gives same fissure, after breathing

for

five _{minutes at}

_about

_I

_{m from the measurement}

site, we measured 5000 ppm.

This

represents an increase

of

32 per cent.

-In

_{absorber and}

Brialmont

_avoiding cave

(January 21,

lg82)

a

measurement

in

the fissure

Fl

was done

rapidly, without

gas breathing. The result is 1000 ppm. The

,À.

_-""r.rrement

was _{carried out after six}

exhalations

in

the ûssure and we

found

1900

pp-

_ii.".

increase

_of

90 per cent).

-In

_{system' Three} the

Trou

Joney

_pairs

(comblain-au-Pont),

_of

6ve measurements were done

with

and

without

the

co,

absorber measures have been done

iu

a

corridor

of

about

1 m2 section: the

co,

average content§ increases by 80 per cent passing

from l-18,

I-66, and

l.7J

mgcor/l

to

z.li,1.n,and

2.gg

mg/l

respectively'

_At

the

extremity of

the cave,

in

the

distal room,

co,

-concâtratious'pass

_from

_{2.03 and}

2'32

mgll

to 5'96 aod 6'46.mgl l. This represents an increase

of

lô0 per cent (measurements _{date: December}

7,

1969:

Ek,

unpublished).

Contamination due

lo

rhe cauers and

the

tourists

-In

_three Rochefort _operators cave'

in

a big chamber, the

initial

co,

concentration

in

the air is 2.30 mg/I. The presence

_of

for

five hours gives a measurement

_;f

_3.31

_mgil

_{which represents}

"o

inü."r.

of 44 per cent

(measurement _{date: September 30, 1969:}

_Ek,

_{unpublished)."}

-In

-

_caveis ste-Ann€ _{(with two} cave (May 28, 1982), a measure in

theiallery

gaie aooo ppm; 20 minutes after the passage

_of

1g carbide lamps), a

sdond

_{measurementwascarried out and 4g00 ppm was}

recorded (i.e. an increase

of

20 per cent).

-In

_of

Remouchamps _{about 20 tourists} cave, Mérenne-schoumaker (1975) has observed,

with

one of us (Ek), that the presence causes an immediate increase of

s25

mg/r

in

the

narrow gaileriË'This

represents a direct increase of the

initial

co,

content of 6 percent.

oüngiwhole

_{day in the tourist season,}

the increase

CARBON DIOXIDE IN CAYE ATMOSPHERES 183 We consider thus that the

CO,

absorber system is a real necessity for measurements in confined places.

In

another

way, the CO, production by

the cavers is

difficult

to

avoid aad we must perhaps deduct

a CO,

background. The CO, peaks are also partly correlated with a maximum of caving activity during the summer.

Therefore noise reaches a maximum

during

this period. Another

difficulty

is

that

the

CO,

concentration,

increased

by humau

CO,

does

not rapidly

decrease

to its initial

value

(Ek

et

al.,

1981).

RESULTS

AND

DISCUSSION FOR CAVES

IN

OTHER COT'NTRIES

Carbon dioxide measurements become increasingly numerous under all cümatic conditions. We shall here use the classification of

Troll

and Paffen (1964) who distinguish, beside the Cool-temperate Zones, two series

of

colder

zones-the

Polar and Subpolar Zones and the Cold-temperate Boreal

Zone-and

two series of warmer

zones-the

Warm-temperate Subtropical Zones and the Tropical Zone. The Cold

Climatic

Zones

In

the Szàpolar Zone, some

f,fty

unpublished analyses by Ek in Labrador (summer 1979), under oceanic

subpolar conditions, displayed very low values

in

soil and

in

cracks and fissures

in

dolomite.

No

true caves were found

but,

even uuder a thick soil cover or in deep cracks or just above spring waters, the

CO,

content

was always below 600 ppm.

In

the

Cold-temperate

Boreal Zone,

some

36

measurements

carried

out

in

Swedish

Lapland,

under continental boreal conditions, displayed figures never exceeding 850 ppm in fissures and 450 ppm outside the fissures

(Figure

I

l:

Ek, unpublished); 200 ppm were recorded twice close to an underground

torrent

surface: such a low value, well under the mean value of outside atmosphere, is not unusual in cold climates. The mean

of all

measurements

in

385

ppm (+

o

:

150).

Around Lake

Mistassini,

in

the Canadian boreal forest, about 20 analyses

(Ek,

1981) displayed values

reachingamaximumofl300ppminasmallcave.Themeanvaluesfoundwerell@ppminthesoil,450ppm

in the open air under forest cover 800 ppm in caves and fissures.

It

should be noted that all measuremeuts here

referred

to in cold climatic

zones

(Labrador, Lapland

and Lake Mistassini) were

carried out in July

and

August.

Although

much too scarce, these analyses of the air of cold regions show its paucity

in CO,

content. This

conciusion is strenglhened by the computations of Ford

(1971),liloo

and Marsh (1977), and Roberge (1979), all based on \r/ater analyses in limestone regions, showing that in Canada the cold regions are poor in

CO,

and

that the tundra

and

the

alpine meadows are

poorer than the

boreal forest. Concordant conclusions are

FIVEB

-..

Figure I

l.

Lower Cavc, at Bjortl.idca (Swcdish l-aplaad). Cross-scction at I 6 m from the cave eotraacc. CO, contcnt of the air in ppm (July 26, 1982)

o2

184

i}:J#,ii,i*ïîlJtJiffr:l,ilîi;:,,rements

in the

_{air of}

_{castreguard cave,}

_in

_{rhe canadian Rocky}

The Cool-temperate _Zones

under

oceanic and suboceanic climates, _{measures are available}

_in

England, Belgium, and France.

In England'

Atkinson (197

_5,

_{lg77) observes values}

rather similar

to

the ones of Belgium:

in

GB. ,cave, 33 measurements _{display^co-ntents averaging}

4100 ppm

in

g"[.ri.r

à"a

g200 _ppm

_in

_{the fissures}

with,

in those

placeq a

maximum

of

16000 ppm.

This

is concordant with the more than 600 analyses _{carried out in Belgium, where the}

range is 300-7000 in the passageways and reaches a

_{maximum of}

_{9000 in fissures}

_(this

_paper).

In France' where _{Renault (1982c) lists two to three thousana}

à*tyr"r,

tt.

co,

content is _{much varyiug and} is

often

very

_{high' In}

_{the karstic plateaux of}

the

southe-

t"ra"r.îtheMassif

_ô.ro"r,iI"

_maximum

_pco,

reaches 70 000 ppm'

A

co,

contint

of 40 000. to. 50 000

_;p-

;

_r.Jir"otty

_{reported (Renaurt,}

1982a). Lower

ranges are cited

in

relation

with

the

morphology

of'Ëaves:

"ui",

oi

medium

co,

content

(10000 to

30 000

ppm)

are generally _long

_horizontal

_câves;

.caves.

of

row

co,

content ( t 000

to

r 0 000 ppm) are ofren

horizontal too'

but more _{ventilated, and}

""1?tdjrpl"Iing

a

corÉncentration

near

to

the free

air

(300 to

1000

ppm)

are often

two€ntrance

caves,

witn

higÀ

*,

"îourutiân

(Reuault,

t9z6).

The

co,

distribution

is related

to

the cave morphology _{and the}

_circulation

_{of the}

_air,

and its evolution is

comelated

_with

_{meteorological parameters,}

such as

"-Ëru,.rüi"ro-.tri"

pressure, and

rainfall

(see,

_for

example'Renault,1968,l976, 1979,1982a,b,c;Renaüt;ràB;;";;r9gr).Despitedetaileddeveropmenrson

the causes of the high

_co,

contents, oo"

"orlâ

wish

a."t;;,iti;lïir".rrrioo

on _{possible influences of human}

Ëâ:"ü;î"ï.i"§::,',:ïi;;3.""

question

orair-water;;;;il;",

see, ror

il;;;{oq,,",,

_{res6, rese,}

under

continental _{and subcontinental climates' the}

measured _{values show cousiderable variations} as

weil

In

_{Quebec' Ek} (1981), having _{carried out some 200 aaalyses}

io

"iir""roos,

obtains a range of

co,

content

going

from

440

to

I100 ppm

in

_{the galleries and chamberr,}

_rrrr.r"",

_the

fissures display maximum values

il

sunmer (up to

2800ppm).

_A

_{crosed cave dispravs}

_higil;c6;

iiigure

rz). These figures are in accordance

_with

_{the measurements}

made

ia

pàland,

in

the silesian

upland

(Ek er al., 1969), showing, during-the snow-melt

p";oa,or

ii;;d;;

_rpirg,r-.,

₅₀₀

to u00

ppm

in

passageways

and a

maximum

of

1370 ppm

_in

_{the términal}

_ûssure

_{oi ,n"}

""r...

--C. EK AND M. GEWELT

SW

_NE

4300 â 2 1 Om

Figurc

l2

_{st'Lconard cavc' Montrcal (Qucbcc,}

canada).,cross-- scctioa acarby rhc far cad of thc cave.

co,

_{conænt of thc air in ppm}

-CARBON DIOXIDE IN CAVE AT}{OSPHERES

In

the caves of Kentucky, 400 to 800 ppm were generally obxrved by

Miotke

(1974) in the galleries

during

the summer; in winter, he uoted 400-600 ppm; the maximum vaiue he observed was about l300 ppm; all these observations were made

in

rather spacious caves.

In some caves of Ukraine, values ranging from 500 to 40 000 are noted by Klimchuk et al.(1981); the highest figures are attributed to the abundance of organic matter in the concerned cave, and the possible (although

not

measured) occurrence of CHo, possibly immediately oxydized in COr; the occurrence of gypsum is also noted.

Lewis (1981) has studied a cave under a cultivated area, and frequently invaded by organic matter. The

author

ascribes

to

the

latter

fact the

high CO, content-5000 to

25 000

ppm--of

the cave.

Few measurements are known to us in the caves of the mowtain climates of the cool-temperate zones.

ln

the

Swiss Alps, one

CO,

measurement was done by Forel (1865) in a cave near Saint-Maurice.

In

Bôdmerenalp

Cave, above the

Hôlloch

Cave, Bôgli (1970) finds a very poor CO, content (160 ppm), in relation to the high altitude of the cave (1670 m) and the strong wiud outside. In the galleries of the Hôlloch Cave,

CO,

contents

are

low-from

250

to

400

ppm-but,

in

confined places connected

with

the saturated zone,

Bôgli

(1970) measures 1300 ppm, the highest observed value

in

this cave. Gomparable values were also found

during

the

1973-1974

winter (Bôgli,

1975).

In the Polish Carpathians,Ek et al. ( 1969) have found in four caves, during the snow-melt, 200

to

I 100 ppm

(40

titrations)

and a maximum

of

2000

ppm in

a fissure.

In the low and middle French

_§renean

Mountains,

pCO,

exceptionally reaches 14000 ppm (Renault and

Brunet, 1981). Generally, however, the CO2 content of the air is lower in the mountain caves than in caves

of

lower

altitude (Renault,

1968).

The Warm-temperate Subtropical Zones and the Tropical Zone

In Northern Italy,

a cave of the

Ligurian

coast displays

pCO,

values ransing

from

400

to

800

ppm;

the

maximum

pCO,

(1500ppm) was observed

in

a fissure (24 measurements: Gewelt and

Ek,

1983).

In the atmosphere of the caves of Bungonia (New South Wales, Australia), considerable amounts of CO2,

biologically produced, are always present (James, 1977).

In

the

north of

Madagascar, the seasonal evolution of the carbon dioxide of soil air was studied

by

Rossi (1974). The measured values range

from

5000

to

32000ppm, this

maximumbeing

observed

in the

humic horizou, at the beginning of the rain season. Measurements carried out above that humic horizon, at the base

of

the

litter,

display a lower

CO,

content.

CONCLUSION

It

seems clearly established now that the

CO,

piesent in caves has generally a predominant organic origin.

It

is

thus less abundant,

for

instance, under

cold

climates.

Phenomena such as the climatic variations, the seasonal rhythms, the greater abundauce

in

the fissures connecting the caves

with

the soil, the varied gradients are indeed largely interconnected.

\Ye believe

that in

some cas€s, high

CO,

contents are

partly

resulting

from

humaa

perturbations. As

a consequeDc€,

the

use

of

a CO,

absorber system

is

necessary,

particularly

in

confi.ned places.

In

caves frequently visited by cavers or lourists, the human influences on CO, measurements are difficult to avoid,

but

this fact must be taken

into

account

for

the

interpretation of

the results.

Other

acids can dissolve limestone

in natural

environments.

But

the paramount importance

of CO,

is evident. Limestones, which are so largely biogenic, remain thus after their formation lænnanently involved

in

the biological cycles

of our

planet,

of which

they

form

an original and very characterisüc component.

Atmosphere and organic reactions are

not

the only origins of the carbon dioxide;

CO,

can be produced by

inorganic reactions, originate from the depth of the Earth, etc. These origins and their relative importance, as

well as

CO,

variations during the Quaternary

climatic

changes are

still

a wide-open research

field.

Stable isotopes and !aC analyses could certainly

contribute

to

this topic.

186

C. _{EK AND M. GEWELT}

This work

has been _{supported bv Research}

Ë",=-":ttiiilil'",

Fund

for

scientific _{Research (Bergium).} The authors are

gratefJ

to

ptort.,àr;.

_;;;,

_{for his}

_*"rî

"ïr"3re

commenrs.

Th.y

wish arso

to

thauk

iHi:ît"îîfii#:|i'#ï:H:;à.,i"e

à.ra

*.",,,"*.ni,

_{uiîLo-i,ique}

w,rem io,

i",

herp

with

the REFERTNCES

Adams, _{C. S. and Swinr}

atrnsÉnl

_{rl-cïiriî'".ë""o*}

A'

c'

t937' 'solubility of limestone', _{Trans. Am.}

Geoph. t)nion,pl 2, 504_50E.

.

rimesrooes',

,i,ii.n.-r^.'o3Ï*o)!i,iil*"|.ï;;li,W;;"il;#i:'.',i;e:

an imponant

*oi-r

_{org,oundwarer}

harduess in

Ar*inson, T.

c.

1s77..c."r,u",

_{a^,g_!gï;#;âî;ere}

of the unsarurated _zon, lrmestones', _J

' o{ H vdr.çlegy, _{ss, r I r}

_-l

_ij.

-*-ovnÊre ot the unsaturated zone: an important contror _of groundwater _{hardness in} Atkinson, T. C., Smari, p.

_{r"ï"a wiei*ï.}

_r.

U ,,

;:F,,,'i,rJïiffi

_{î1i[iiü,{!''-,x-"':ï::î::;:.ïîïr7,ï;i'î)ïi:::.::}

Bôgli, A. 1969. Co.-.Gehalii^a"ïilin _q

_liinen

Karsruoaen und Hôhlen,. làr_

ïi:i.,ï.,i'T:i',î*:r:#â];'jrr"{ïillrïi.in}ïï;,,î".i:ii;"|

i,:,';,::::;::::;:i:}1lll

_l,,,

""':f*Tiril;..iï"'"

voa Lurt uad Kalkgehalte _{von wàssera im}

unrerirdischen _{Karst,, Z.} Geomorph. _{N. F., suppt.-.d.,26,}

*,lft;;*r-"*-ilmïfuî:*t$â#r,,*î#,,3.r,ï,ï:;:",ï,:*U:::::ïï.

*r,,*:**çg-*r,*iffifïü:',-;iri*,..,":x*:fxi:'ï":x::1*

gËig:ffi.f1+[*+]roi**,îft

,r,,:i.,:i:,:,in:

,-,,.,j;jiï:ff*lr.§':?*kî{:i#i}';g,tnr.îi:i

;:;,'a,r:r:i;Jfr:iï;ui'!"x:TJi#*#îi!t:rt:,:,

i,Ét

i#î:::danst'airdesgrottcscomparaisonerÉbcc-Bergi

,",,;;:;::::':;1,ï';ir)îrf,i.rîl;,

-

at.

yt1,.e"r',

k;;;;îü'.Zl

l'rll;rTâ.*tctreurensazcârboniquedel'aird'unecavitédueuébecragrortedcsaint-Léonard,ire

ï#i_H;J1,.":,,:::::::-:_

_--ï:,uüon

in the southera Rocky Mouotains and _{serkinl Mounta ins,, Co,,.}

r. Earth sci., E,

i!!i#,

i:ff.

;Tfï:'.êl:*"::lle.des

Fg"

ruü.

r*;::*u:sc.-aar.

(Lausa",;;;;*'^rEr

luoun*ins" can'r' _{Earth sci''E}

:.ÏËi#jlff+tjpl,Î*ffis*;;g';rll*rrEïi:i:.':*e

Faæ premièresmesures,,

Bu,, s.c

New Directions ;'-

i;;;.

Geo

Booksrôe;ffiil:

_{i,i;U*Si;1liîf-e}

deux grotres berges: ste-Anne er Briarmonr (rirCI., jn

'ît

T

'r[î:Tr'

D' w'' Thorstcnsoo' D' c" aad ]vccts, E. p. _{1983.'rrcoz ard}

r.co:

mcasuremenb _{ou soi}

latmosphere,, Radiocarbon,

,#f,ffi,;71î*g,*ire

des sors _{équaroriaux' Apprication de}

ra _{méthode respirométrique in situ,,}

Bur.

rnst. _{Asron. stat.}

ffi;sg*

:..::::

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patersoo, K. 1979. 'Field studies of limestone erosion processcs, Oxfordsbire Scarplands, England', Actes Symp. int. Erosion karstiEte, U.,r.S., Aix-en-ProveDc€, Marscille, Nîmes, mém. l, A.F.K:, 87-95.

Renault, P. 1968. 'Sur la distincüon de plusieun régions karstiques en raison de la teneur en anhydride carbonique des atmosphères de

srottes"

c.

R. Acad..sci. Par§ 26? (D), ?288-2290.

RJoault, P. 1916. 'l-e gaz carbonique danj les Brorr€s du Quercy', Butt. Comité Départ. Spéléo. Lot-, 2'.94-104' .

i.o"olt,

P. 1979. 'Mesures penodiques de la _iCO, dansàes _Éottes françaises', Acres Symp. int. Ersion karstique, U./.S., Aix-eu-Provencc, Marscille, Nîmcs, mém. l, A.F.K., 17-33.

Renault, P. and Brunet, J. 1981. 'Les variaüons de la p6O, atmosphérique dans les grortes des Pyren&s centrales-grottes de Moulis et de

Niaux (Ariège)', Colloque de §eyssras sur le karst, F.F.S.,5-18.

Renault, P. 1982a.

'k

COz dans làtmosphèrc de quilqucs cavemes du _Quercy (Départemeût du Lot-France)' , Spéléo-Dordogne,14, 3- I 15.

Renauit, P. 1982b. 'Rôle de la morphologic et du climat d,ns le tra1sfcrt du CO, au niveau de la surfacc aqüfère, 3e Colloque Hydrologie en Pays calcaire, Neuchatet-Bcsançon 1982, Ann. Sc. Unio. Besançon, Géotogie, Mém. 1,281 pp-(5 pp).

Rcnault, P. 1982c. 'CO, atmosphérique karstiquc et speléomorpbologie. Intérêt pour les speléologrres', Reo. belge de Géographie,lM, l2l-130.

Roberge, J. 19'19. Géomorphologie du Karst de Ia Haute Saumons, île d'Anticosti, Qübec, M.Sc. Thesis, Mc Master Univ., Hamilton, 211 pp.

Roques, H. I 956. 'Sur I'existence d'un gradient karsüque des pressions partielles de I'acide carbonique', C. .R. Acad. Sci. Paris,242,3100-3102.

Roques, H. 1959. 'Sur la répartiüoo du CO, dans lcs kants', lnn. Spéléol., 14,9-22.

Roques,H. 1962.'ÀppareillagespourledosagcdcCOrdaaslesmélangesBazrux.§otcdelaboratoire)', laa.Spéléo., l7(3),455-462.

Roques, H. 1963. 'Sur la répartiüon du CO, dans lcs kants (2c mémoirc)', Ann. Spélèo., lE (2), 142-184.

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