B
iot
ic
methane
ox
idat
ion
w
ith
in
an
instrumented
exper
imenta
l
1landf
i
l
l
cover
2 3 4Louis-B. Jugnia1*, Alexandre R. Cabral2, S. Aït-Benichou2 and Charles W. Greer1 5
6 7
1Biotechnology Research Institute, National Research Council of Canada, 6100,
8
Royalmount Ave., Montreal, Quebec, Canada, H4P 2R2 9
2Department of Civil Engineering, Université de Sherbrooke, 2500, boul. del'Université,
10
Sherbrooke, Quebec, Canada, J1K 2R1 11 12 13 14 15 16 17
Key words: Methanotrophs,landfill cover soil,methane, compost, methane oxidation 18
19 20 21 22
Running title: Methane oxidation within an experimentallandfill cover 23 24 25 26 27 28
*Corresponding author
29
Phone: + 1 (514) 496 0714 30
Fax : + 1 (514) 496 6265 31
Email: louis.jugnia@cnrc-nrc.gc.ca 32
Jugnia, L. B.#, Cabral, A.R., Greer, C.W. # (2008). Biotic methane oxidation within aninstrumented experimentallandfill cover. Ecological Engineering, 33(2): 102-109.
Abstract 1
An experimentallandfill cover composed of a mixture ofsand and compost was 2
installed at the St-Nicéphore landfill in Québec (Canada). The mixture was evaluated as 3
potential substrateto promote methane (CH4) oxidation by methanotrophic bacteria. One
4
ofthe objectives ofthis field project wasto assessthe efficiency ofthe coverin reducing 5
CH4emissions. Forthis, both CH4abatementandtheextentto which methanotrophic
6
bacteria developed werefollowed overtime and space in relation to environmental and 7
physico-chemical variables. Theresults obtained duringthefirst year of monitoring 8
indicatedthat precipitationandairtemperature hada greatimpact on CH4 oxidation.
9
Overthestudy period, different patternsin CH4oxidationthroughthecoversoil were
10
observed;in certain cases, oxidation was observed at various depths, althoughthe zone of 11
optimum oxidation occurred mostly nearthe surface. However,inthe second half ofthis 12
first year of monitoring, almost no oxidation was observed at depths greater than 10 cm, 13
presumably because of lack of oxygen reaching deeper zones within the cover. In the 0-14
10 cm zone high numbers and important variations of particulate methane 15
monooxygenase gene (pmoA) copy number and counts of methanotrophic bacteriawere 16
also observed. It is concluded that the adopted substrate has proved to be satisfactory in 17
sustaining and promoting growth of methanotrophic bacteria. However,the water content 18
of the soil seems to be a key factor influencing CH4 oxidation, to an extent that requires
19
further investigation. The uppermost 0–10 cm layer seems to play a critical role in CH4
20
abatement; one important challenge will be to explore this in more detail by conducting 21
more measurements withinthis zone. 22
Introduction 1
Methane (CH4) is a potent greenhouse gas. It absorbs infrared radiation more
2
effectivelythan CO2 (Crutzen, 1991) andits atmosphericconcentrationisincreasing at a
3
rate of 0.6% per year(IPCC, 2001). This increase has beenlinkedto globalclimate 4
change.Itis nowestimated thatas muchas 70% of CH4emissionsare dueto human
5
activities,andas muchas 19% oftheincreasecan beattributedtolandfillemissions 6
(IPCC, 2001). Therefore, management practices thatcould helpreduceemissionsfrom 7
landfillsare of greatimportancein connection withtheatmospheric CH4 budget. Gas
8
extraction systems, which are now widely adoptedinthe developed world, are considered 9
the principal means ofachieving suchreductions. However, CH4reductioncanalso be
10
regulated by methanotrophic bacteriathat developintheaerobic zone ofthelandfill 11
cover. Itis well establishedthat methanotrophs are capable of efficiently converting CH4
12
to CO2 and biomass (Conrad, 1996). If atechnology – and a methodology -is developed
13
to harnessthisability of methanotrophs,itcould beappliedtoimprove CH4emission
14
abatement from landfills. However, the quantitative significance of the reduction, which 15
depends ontheavailability of CH4(Pawlowskaand Stepniewski, 2006),as wellas on
16
several environmental factors, needs to be determinedinthe field. 17
Composted organics promote good microbial growth and appearto make an effective 18
mediumforlandfillcover(Humerand Lechner, 2001),asit offersa good mixture of 19
porosity, water holding capacity, pH, and nutrient supply (Hilger and Humer, 2003). Both 20
field observations at landfills and results from laboratory studies have demonstrated that 21
organiccoversoils havea highcapacityto mitigate CH4emissions(Borjessonetal.,
22
1998b; Humer and Lechner, 2001), and the CH4 oxidation potential in mineral soils can
be enhanced by adding organic material, e.g. sewage sludge (Kightley et al., 1995) and 1
compost (Humer and Lechner, 2001; Barlaz et al., 2004; Maurice and Lagerkvist, 2004). 2
Research so farindicatesthat compost should be capable of oxidizing CH4 at ratestwoto
3
threetimes higherthanthat of mineralsoils(Wilshusenetal., 2004). However, use of 4
compost alone, or other high organic contents material may not constitute anideal 5
substrate:the materialcan undergosignificantcompaction overtimeandcan become 6
easily saturated, causing a reduction in oxygen diffusion into the cover to promote CH4
7
oxidation. 8
It seemslogicalthat alandfill cover could be designedto promote optimum growth of 9
methane oxidizing bacteria and thus enhance biological oxidation of CH4. Various
10
landfill covers or biofilter designs, using different configurations and substrates to 11
support growth of methanotrophs have been evaluatedelsewhere (Hilgerand Humer, 12
2003; Gebert and Groengroeft, 2006). However, results from efficiency tests under field 13
conditions are mostly available for covers or biofilters working under temperate climatic 14
conditions. Tothe best of our knowledge, no such attemptshave been made so far under 15
thecold Nordicconditions. Thistype ofcover,referredto hereasa passive methane 16
oxidation barriers (PMOB), might provide an alternative method of emission abatement 17
for oldsites, whereflaring or energyrecoveryis not economicallyfeasible, or as a 18
complementary strategy to gas collection systems. Indeed, it has been reported that even 19
atsites with gascollectionsystems,significantamounts of biogascanstillescapeas 20
fugitive emissions (e.g. Spokas et al., 2006; Börjesson et al., 2007). In order to evaluate 21
the potential of PMOBin Nordic climatic conditions,this multidisciplinary project 22
consideredthe geotechnical, hydraulic, physico-chemical,environmental,climaticand 23
microbiological aspects in assessing the efficiency of landfill cover materials that would 1
act as a PMOB. Some oftheseissues are addressed herein. 2
Within the framework of this multidisciplinary project, 3 PMOBs were designed and 3
constructed at the St-Nicéphore landfill, Quebec, Canada, a waste disposal facility 4
covering approximately 65 hectaresthatreceives mainly domestic waste. The cover 5
includesalayerconstituted ofa mix ofcompostandsandassubstrate. Both methane 6
abatement through the designed PMOB and the extent to which methanotrophic bacteria 7
developedinresponsetotheflow of CH4werefollowed overtimeandspaceandin
8
relation to environmental and physico-chemical variables. This paper reports the results 9
obtained overthe first year of monitoring. 10
11
Material and methods 12
Description of the field experimental plots 13
Three experimental plots measuring 2.75 m(W) x 9.75 m(L) were constructed 14
during the summer of 2006. Each of the plots included an 80-cm thick layer of substrate 15
underlain by a 10-cmthicktransitionallayer consisting of 6.4-mm net gravel and a 20-cm 16
thick gas distribution layer (GDL) consisting of 12.7-mm net gravel. In this paper, only 17
details pertaining to one of the plots, PMOB-1, are presented. This plot was fed directly 18
by biogas coming fromthe 3.5-year old buried waste mass (Figure 1). Giventhe factthat 19
the substrate layer thickness was fixed at 80-cm, a 200-cm thick GDL was necessary in 20
orderto reachthe waste mass, atthis particularlocation ofthelandfill. 21
The substratelayer consists of a mixture of sand and compost, composed of 5 22
volumes of compost (before sieving) and 1 volume of coarse sand (D10 = 0.07 mm; D85 =
0.8 mm; Cu= 4.3). The 2-year old compost, was provided by alocal producerthat 1
composted a mix of municipal sewage sludge and sludge from pulp and paper and agr i-2
foodindustries. Thesand-compost mixture was sieved usinganindustrial meshsothat 3
the end product would contain particles no greaterthan 12 mm. The organic matter 4
content of the mixture was 17.8% (g_volatile matter/g_dry soil). Respirometry tests were
5
performedaccordingtothe BNQ 0413-205-art 9.5standard(BNQ, 1997) on duplicate 6
samples ofthe mixture. The following results were obtained: 268 and 230 mgO2/kg.v.s.h
-7
1.
8
The substrate layer was placed in four 20 cm layers and compacted with a vibrating 9
plateto obtainlayers withanaverage density of 838.8 kg/m³(or 85% ofthe optimum 10
Proctorstandard). The wallsaroundeach ofthecells werethermallyshieldedfromthe 11
outside environment by 15 cm thick polystyrene panels. The goal was to prevent lateral 12
migration of moisture duetothermal gradients. 13
Environmental, physico-chemical and microbiological variables 14
Probes for measurement of water content (θ), suction (ψ),temperature and gas 15
concentration wereinstalled atfour separate downgradient points and at 4 different 16
depths(6inthecase of gas probes)in each profile(Figure 1b). Meteorological data, 17
including precipitation and atmospheric pressure, were recorded continuously by a 18
weather station installed near the exprimental plot. Suction data is neither presented nor 19
discussedinthe present paper. Thetemperature(HOBO U12,from Onset)and water 20
content (ECH2O EC-5, from Decagon) probes were connectedto dataloggers.
21
On a weekly basis, vertical concentration profiles of CH4 and O2 in the pore volume
22
ofthe PMOB were manually obtained. Forthis, gassamples werecollectedfrom gas 23
probesinstalled permanently at 6 different depths withinthe PMOB (Figure 1b). Samples 1
were analysed in situ using a portableinfrared gas analyzer (Columbus Instruments). Gas 2
emissionsatthesurface oftheexperimental plot werealso measured usinga dynamic 3
chamber, as described by Fécil et al. (Fécil et al., 2003). 4
Samples were collected from the uppermost part of the substrate (0-10, 10-20, 20-30 5
and 30-40 cm) using PVC coringtubes (internal diameter = 5 cm). The cores were kept at 6
4ºC until analyzed in the laboratory within 24-hours. The analyses included pH 7
(determinedin distilled water 1:3 v/v) (Page et al., 1982), counts of methanotrophs using 8
the most probable number method, and quantitative detection of methanotrophs by 9
targetingthe particulate methane monooxygenase gene(pmoA) using quantitative-PCR 10
(Q-PCR). For methanotrophcounts,soilslurries wereserially dilutedin 96-well plates 11
(microliter) containing ammonium mineral salts medium. The plates wereincubated for 4 12
weeks at 25ºCin gastightjars containing 18% CH4in air.
13
Q-PCR is a relatively novel methodological approach to quantifying bacterial 14
abundanceintheenvironment. This methodis usedto determinetheconcentration of 15
target DNAin environmentalextracts. Inthis study, pmoA wasthetarget gene sinceitis 16
presentinalmostall known methanotrophs, withthe possibleexception of members of 17
the genus Methylocella, which are generally isolated from acidic environments (Dedysh 18
et al., 1998; Dedysh et al., 2000; Dunfield et al., 2003; Theisen et al., 2005). For Q-PCR 19
analysis,total DNA wasextracted directlyfrom oursamples using mechanicalshaking 20
and an enzymaticlysis procedure as describedin Fortin et al (2004). Genomic DNA was 21
then purified usinga MicroSpincolumn containning polyvinylpolypyrrolidone(PVPP) 22
(Berthelet et al., 1996). Total genomic DNA was quantified by staining with pico green 23
dye using a Spectrafluor fluorometer (Tecan) and lambda phage DNA as a standard. Q-1
PCR was performed on DNAtemplate usingthe pmoA primer set A189/mb661. 2
3
Results and discussion 4
Throughout the present study, with the exception of the period between late July and 5
early August 2006,the barometric pressure (pbar) ranged from 99.34to 102.90 kPa (mean
6
± SD = 101.12 ± 0.69 kPa; Figure 2) and fluctuated daily. This fluctuation was mainly 7
oppositetothe windspeed withasignificant negative correlation(r = - 0.5, p < 0.05) 8
found between these two variables. Nastev et al (2001), Czepiel et al. (2003) and Gebert 9
and Gröengröeft (2006) found an inverse linear relationship between landfill CH4
10
emissions and pbar. Accordingly, it can be expectedthat the fluctuation observed during
11
this study affectedthe outward flow of biogas. However, since gas sampling and surface 12
measurements of gas emissions were performed on a weekly basis, whereas 13
meteorological data was recorded on an hourly basis, a clear relationship between 14
outward gas flow and meteorological data could not be establishedinthe present study. 15
Besides external controllingfactorssuch as barometric pressure, windspeed and 16
engineered controls (gas collection system), the water content of the cover soil has been 17
identified as animportant factor controlling CH4 emissions fromlandfills (Bogner, 1992;
18
Bogneretal., 1995; Kjeldsen, 1996). The watercontent ofthesoil depends mainly on 19
atmospheric precipitation and onthe capacity ofthe materialto retain or release moisture. 20
During this study, precipitation varied between 0 and 1.12 mm d-1 with a mean ± SD =
21
0.06 ± 0.17 mm d-1, whereas the air temperature ranged from 2.3 ºC to 22.7 ºC, with a
mean equal to 12.86 ± 5.09 ºC. Both variables fluctuated with time, but the trend in air 1
temperature showed a gradual decrease as Fall approached (Figure 2). 2
The volumetric water content (θ) of the substrate varied from 51% to 64% and was 3
obviouslysensitiveto precipitation. Near thesurface ofthe PMOB, wheresignificant 4
variations in the water content occurred, values ofθ were close to the lower range (θ = 5
52%) only ontwo occasions, July 20 and September 25. Both occasions correspondedto 6
periods of high temperature (Figure 2) and prolonged absence of precipitation. 7
Otherwise, most of the water content profiles exhibited variable trends that were related 8
to episodic events of precipitation spread out over a variable number of days during the 9
study. For example, changes observed in the water content profiles on August 2, 10
September 5 and October 2matched with periods of significant precipitation (Figures 2 11
and 3). Furthermore, from October 2 until the end ofthe study,the water content 12
remained highinthe uppermost part ofthe cover(Figure 3), whiletheairtemperature 13
remained relativelylow at ~ 8ºC (Figure 2). 14
As expected, the temperature profiles (Figure 3) exhibited variations with depth and 15
time,the highestthermal amplitude (25to 10ºC) being associated withthe uppermost part 16
of the cover, which is most affected by weather conditions. At 82 cm below the surface, 17
thetemperature varied from ~22ºC duringthe hottest periodto ~15ºCin October. 18
Temperature has a directimpact on biological reactions, such asthe oxidation of CH4 by
19
methanotrophs;it has beenshownthat CH4consumption by methanotrophsincreases
20
withtemperature (Whalen et al., 1990; Czepiel et al., 1996; Gebert et al., 2003; Borjesson 21
et al., 2004; Park et al., 2005; Jugnia et al., 2006), when the CH4 concentration, among
22
other factors,is notlimiting (Pawlowska and Stepniewski, 2006). 23
With the exception of the CH4 concentration measured onJuly 20, concentrations of
1
CH4atthe bottom ofthe PMOB(82cm) were generallycloseto 55%(Figure 4),a
2
common valuefor CH4concentrationin biogasfrom landfills(Bogner et al., 1995;
3
Borjesson et al., 2001; Kallistova et al., 2005). Thisindicatesthatthe supply of CH4 was
4
notalimitingfactor duringthestudy period. The decreasein CH4concentrationasit
5
diffusedthroughthesand-compostsubstrateexhibited different patterns overtime. As 6
shownin Figure 4, duringthefirstfivesamplingcampaigns(July 20to Sept 1),the 7
concentration of CH4inthe upper most gas probe(at 10cm) decreasedto muchlower
8
values(from below detectabletoapproximately 18%)thanthe 55%foundatthe base. 9
The abatement was gradualthroughoutthe profileforthefirst two sampling dates. 10
However, for the other dates, the oxidation front (indicated by the steep decline in CH4
11
concentration) seemsto belocated between 30 and 20 cm fromthe surface(Figure 4). 12
In a controlledlaboratory environment, Berger et al.(2005) observed an upward 13
displacement of the oxidation zone as infiltration was supplied to their test cell. 14
Furthermore,factorssuchastemperature, moisturecontentandavailability of O2 may
15
influencethe depth of optimum oxidation, whichcan varysignificantly. Forexample, 16
Whalen et al. (1990) foundthatthis zone is situated between 3 and 12 cm, while 17
Visvanathan et al. (1999) located it between 15 and 40 cm. Humer and Lechner (2001) 18
found in their field test, where sewage sludge and MSW compost was used as substrate, 19
that the zone of maximum CH4 oxidation extended from 40 and 90 cm. The conditions
20
under which these covers were placed, as well as climatic and other limiting conditions, 21
such as precipitation, pH, O2 supply, etc., affect oxidationrates and, ultimately,the
22
location ofthe optimal oxidation zone. 23
The pH ofthe soil was not alimiting factorinthis study, asit varied only slightly (7.0 1
to 7.3; mean ± SD = 7.2 ± 0.1) overtimeand depththroughoutthe monitoring period 2
(Figure 5). Growth of methanotrophs is generally optimal in this pH range (Whittenbury 3
et al., 1970; Dunfield et al., 1993; Hütsch et al., 1994; Bender and Conrad, 1995), which 4
indicatesthat fluctuations observed fortheactivity and abundance of methanotrophs were 5
governed by other factors. The oxygen supply below 10 cm varied from below detectable 6
to 9.7% duringthefirstfivesamplingcampaigns, but duringthesubsequentsampling 7
(September 5 onwards),the O2concentrationremained verylow(~ 1%) below 30cm.
8
From September onwards the water content and temperature within the PMOB began to 9
decrease with depth. The high water contentthroughthe depth profile acted as a physical 10
barrier to O2 penetration (Boeckx and Van Cleemput, 1996; Czepiel et al., 1996;
11
Christophersenetal., 2000; Kallistovaetal., 2007). Studies of CH4 oxidation kinetics
12
have shownthatthe oxidation rate plummets whenthe gaseous O2concentrationislower
13
than ~ 3%(Czepiel et al., 1996; Stein and Hettiaratchi, 2001; Gebert et al., 2003). 14
Accordingly, the temperature and water content within the substrate might have 15
simultaneously affected CH4 oxidation duringthis study.
16
Starting on September 5, and withthe exception ofthe profile obtained on September 17
11,thereductionin CH4concentrationsstartedto be negligible below 10cmfromthe
18
surface. Surprisingly, surface emissions of CH4 below the detection limit were obtained
19
during this same period. In general, the low reductions in CH4 concentrations across the
20
profile should be accompanied by high surface fluxes; it can thus be hypothesized that, 21
during this period, a significant proportion of the CH4 was oxidized within the first 10
22
cm of the PMOB. Although this interpretation should be taken with caution (gas 23
measurements were not performed within the 0 to 10 cm superficial layer), this 1
hypothesis is substantiated by Q-PCR analyses, which showed that the number of copies 2
of the pmoA gene decreased 10 folds between the 0–10 and 10–20 cm sublayers (Figure 3
5). Similar to the observation by Kolb et al. (2003) that cell numbers determined by Q-4
PCRanalysisinspikedsoilsamplesshoweda good match withthe numbers ofadded 5
cells,thistrend paralleledthat observed with methanotrophcountsthat were highestin 6
the upper most sublayer (Figure 5). Somestudies (Jones and Nedwell, 1993; Bender and 7
Conrad, 1995; Borjessonetal., 1998b; Kallistovaetal., 2007)reportedacorrelation 8
between CH4 oxidizing activity andthe number of cultivable methanotrophs.
9
On average, the number of methanotrophs (range = 1.50 x 106 to 1.83 x 108 CFU g-1
10
DW(dry weight ofsoil); mean ± SD = 3.40 ± 2.68 x 107 CFU g-1 DW) decreased 11
somewhat with depth,from 7.83 ± 5.42 108 CFU g-1 DW nearthesurface(0-10cm)
12
where –itis hypothesized- CH4 oxidation mainly occurred. A similarly high population of
13
methanotrophs(1.8 x 106to 3.2 x 107cells per g) was detected inthe upperlayer ofa 14
mature compost material (Jäckel et al., 2005), whereas population sizes ofn x 106 cells g
-15
1 soil were detected previouslyin wetlandandlandfill soils usingthe MPN method (Jones
16
and Nedwell, 1993; Svenning et al., 2003; Kallistova et al., 2007). 17
Temporal evolution of depth profiles of methanotrophs counts could be divided into 18
two phases:thelag phase and the growth phaseitself (Figure 5). Thelag phase followed 19
the construction andincludedthe firstthree sampling campaigns, with abundance profiles 20
more orlessidentical. Thelength ofthelag phasein a mediumto whichthe cells require 21
adaptation varies withthe history oftheculture(Dean, 1957). Usually,theincreasein 22
total mass precedes any division,the majorityofthe cells swellingtowardsthe end ofthe 23
lag period. Therefore, any measuredincrease ofthe CH4 oxidation activity duringthislag
1
phase was dueto anincrease ofthe activity of the resident population ratherthanthe size 2
ofthe methanotrophic population. Kightleyet al(1995)reportedthat underlaboratory 3
conditions(19ºC),ittook 1 monthtoestablishthesteadystateconditions neededfor 4
growing methanotrophs in a soil column. Our results indicated that the establishment of 5
methanotrophs probablytakes muchlonger under field conditions. This observation 6
corroboratesareportfroma previousstudyin alandfillcoversoil by Borjessonetal. 7
(1998a). Duringthesecond phase, whichextendedfrom August untilthe beginning of 8
October 2006, counts of methanotrophsincreased withtime, particularly atthe surface,to 9
reachthe maximum values observed duringthis study. 10
11
Conclusions 12
Fromthe results presented,the substrate (or soil) usedto constructthe PMOB 13
(mixture of sand and compost), was able to sustain and promote growth of 14
methanotrophic bacteria. However,the water content ofthe soil seemsto be a key factor 15
influencing deep CH4 oxidation,the extent of which requires a better understanding. The
16
uppermost 0-10cmlayer appearsto bethe mostimportantlayerin CH4 consumption, and
17
the next challenge will be to explore this in more detail by conducting more 18 measurements withinthis zone. 19 20 Acknowledgements 21
The Authors are gratefulforthetechnicalsupport of S. Sanschagrinfor Q-PCR 22
analysis, and wishto acknowledgethe financial support provided bythe National Science 23
and Engineering Research Council of Canada (NSERC), BIOCAP Canada, the 1
Biotechnology Research Institute (NRC) and Waste Management Canada under strategic 2
grant # GHG 322418-0 3
Bibliography 1
Barlaz, M.A., Green, R.B., Chanton, J.P., Goldsmith, C.D., Hater, G.R., 2004. Evaluation 2
ofa biologicallyactivecoverfor mitigation oflandfill gasemissions. Environ. 3
Sci. Technol. 38, 4891-4899. 4
Bender, M., Conrad, R., 1995. Effect of CH4, concentrations and soil conditions on the
5
induction of CH4 oxidation activity. Soil Biol. Bioch. 27, 1517-1527.
6
Berger,J., Fornés, L., Wawra, B., Zanke, U.,Jager,J., 2005. Methane oxidationina 7
landfill cover with capillary barrier. Waste Manage. 25, 369-373. 8
Berthelet, M., Whyte, L.G., Greer, C.W., 1996. Rapid, directextraction of DNAfrom 9
soils for PCR analysis using polyvinylpolypyrrolidone spin columns. FEMS 10
Microbiol. Lett. 138, 17-22. 11
BNQ, 1997: Organic Soil Conditioners - Composts - Certification Protocol (0413-205). 12
1st ed., Bureau de normalisation du Québec, 21 13
Boeckx, P., Van Cleemput, O., 1996. Methane oxidation in a neutral landfill cover soil: 14
influence of moisture content,temperature, and nitrogen-turnover. J. Environ. 15
Qual. 25, 178-183. 16
Bogner, J.E., 1992. Anaerobic burial of refuse in landfills: increased atmospheric 17
methaneandimplicationsforincreased carbonstorage. Ecological Bulletins 42, 18
98-108. 19
Bogner, J.E., Spokas, K., Burton, E., Sweeney, R., Corona, V., 1995. Landfills as 20
atmospheric methane sources and sinks. Chemosphere 31, 4119-4130. 21
Borjesson, G., Sundh,I., Tunlid, A., Frostegard, A., Svensson, B.H., 1998a. Microbial 1
oxidation of CH4 at high partial pressures in an organic landfill cover soil under
2
different moisture regimes. FEMS Microbiol. Ecol. 26, 207-217. 3
Borjesson, G., Sundh, I., Tunlid, A., Svensson, B.H., 1998b. Methane oxidationin 4
landfill cover soils, as revealed by potential oxidation measurements and 5
phospholipid fatty acid analyses. Soil. Biol. Biochem. 30, 1423-1433. 6
Borjesson, G., Chanton,J., Svensson, B.H., 2001. Methane oxidationintwo Swedish 7
landfillcovers measured withcarbon-13 tocarbon-12isotoperatios.J. Environ. 8
Qual. 30, 369-376. 9
Borjesson, G., Sundh, I., Svensson, B.H., 2004. Microbial oxidation of CH4 at different
10
temperaturesinlandfill cover soils. FEMS Microbiol. Ecol. 48, 305-312. 11
Börjesson, G., Samuelsson, J., Chanton, J., 2007. Methane Oxidation in Swedish 12
Landfills Quantified withthe Stable CarbonIsotope Techniquein Combination 13
with an Optical Method for Emitted Methane. Environ. Sci. Technol. 41, 6684 -14
6690. 15
Christophersen, M., Linderod, L., Jensen, P.E., Kjeldsen, P., 2000.Methane oxidation at 16
lowtemperaturesin soil exposedtolandfill gas. J. Environ. Qual. 29, 1989-1997. 17
Conrad, R., 1996. Soil microorganisms as controllers of atmospherictrace gases (H2, CO,
18
CH4, OCS, N2O, and NO). Microbiol. Rev. 60, 609-640.
19
Crutzen, P.J., 1991. Methane sink and source. Nature 350, 380-381. 20
Czepiel, P.M., Mosher, B., Crill, P.M., Harriss, R.C., 1996. Quantifyingtheeffects of 21
oxidation onlandfill methane emissions. J. Geophys. Res. 101, 16721–16729. 22
Czepiel, P.M., Shorter,J.H., Mosher, B., Allwine, E., McManus,J.B., Harriss, R.C., 1
Kolb, C.E., Lamb, B.K., 2003. The influence of atmospheric pressure on landfill 2
methane emissions. Waste Manage. 23, 593-598. 3
Dean, A.C.R., 1957. Theadaptation of bacterialcultures duringthelag phasein media 4
containing new substrates or antibacterial agents. Proceedings of the Royal 5
Society of London. Series B, Biological Sciences, 147, 247-257. 6
Dedysh, S., Liesack, W., Khmelenina, V., Suzina, N., Trotsenko, Y., Semrau, J., Bares, 7
A., Panikov, N., Tiedje, J., 2000. Methylocella palustris gen. nov., sp. nov., a new 8
methane-oxidizing acidophilic bacterium from peat bogs,representing a novel 9
subtype of serine-pathway methanotrophs. Int. J. Syst. Evol. Microbiol. 50, 955-10
969. 11
Dedysh, S.N., Panikov, N.S., J.M. Tiedje, 1998. Acidophilic methanotrophic 12
communities from Sphagnum peat bogs. Appl. Environ. Microbiol. 64, 922-929. 13
Dunfield, P., Knowles, R., Dumont, R., Moore, T.R., 1993. Methane production and 14
consumptionintemperate and subartic peat soils: responseto temperature and pH. 15
Soil Biol. Biochem. 25, 321-326. 16
Dunfield, P.F., Khmelenina, V.N., Suzina, N.E., Trotsenko, Y.A., Dedysh, S.N., 2003. 17
Methylocellasilvestrissp. nov.,a novel methanotrophisolatedfromanacidic 18
forest cambisol. Int. J. Syst. Evol. Microbiol. 53, 1231-1239. 19
Fécil, B., Héroux, M., Guy, C., 2003: Development of a method for the measurement of 20
net methane emissions from MSWlandfills. 9th International Waste Management 21
and Landfill Symposium, October 6-10, Italy, (CD-Rom) 22
Fortin, N., Beaumier, D., Lee, K., Greer, C.W., 2004. Soil washing improves the 1
recovery of total community DNA from polluted and high organic content 2
sediments. J. Microbiol. Meth. 56, 181-191. 3
Gebert,J., Groengroeft, A., Miehlich, G., 2003. Kinetics of microbiallandfill methane 4
oxidationin biofilters. Waste Manage. 23, 609–619. 5
Gebert, J., Groengroeft, A., 2006. Passive landfill gas emission – Influence of 6
atmospheric pressure andimplications forthe operation of methane-oxidising 7
biofilters. Waste Manage. 26, 245–251. 8
Hilger, H., Humer, M., 2003. Bioticlandfillcovertreatmentsfor mitigating methane 9
emissions. Environ. Monit. Assess. 84, 71-84. 10
Humer, M., Lechner, P., 2001. Microbial methane oxidation for the reduction of landfill 11
gas emissions. J. Solid Waste Technol. Manage. 27, 146–151. 12
Hütsch, B.W., Webster, C.P., Powlson, D.S., 1994. Methane oxidationin soil as affected 13
byland-use, soil-pH and N-fertilization. Soil Biol. Biochem. 26, 1613–1622. 14
IPCC, 2001. Climate Change 2001. The scientific basis. Contributions of working Group 15
Itothe Third Assessment Report oftheIntergovernmental Panel on Climate 16
Change, Cambridge University Press, Cambridge, United Kingdom and New 17
York, NY, USA, p. 881. 18
Jäckel, U., Thummes, K., Kämpfer, P., 2005. Thermophilic methane production and 19
oxidationin compost. FEMS Microbiol. Ecol. 52, 175-184. 20
Jones, H.A., Nedwell, D.B., 1993. Methane emissionand methane oxidationinlandfill 21
cover soil. FEMS Microbiol. Ecol. 102, 185-195. 22
Jugnia, L.B., Roy, R., Pacheco-Oliver, M., Planas, D., Miguez, C.B., Greer, C.W., 2006. 1
Potential activity and diversity of methanotrophs in forest soil, peat, and 2
sediments from hydro-electric reservoir (Robert Bourassa) and lakes in the 3
Canadiantaiga. Soil Science 171, 127-137. 4
Kallistova, A.Y., Kevbrina, M.V., Nekrasova, V.K., Glagolev, M.V., Serebryanaya, M.I., 5
Nozhevnikova, A.N., 2005. Methane oxidation in landfill cover soil. 6
Microbiology 74, 608-614. 7
Kallistova, A.Y., Kevbrina, M.V., Nekrasova, V.K., Shnyrev, N.A., M. Einola,J.-K., 8
Kulomaa, M.S., Rintala, J.A., Nozhevnikova, A.N., 2007. Enumeration of 9
methanotrophic bacteriainthecoversoil ofanaged municipallandfill. Microb. 10
Ecol. 54, 637–645. 11
Kightley, D., Nedwell, D.B., Cooper, M., 1995. Capacity for methane oxidationin 12
landfill cover soils measured in laboratory-scale soil microcosms. Appl. Environ. 13
Microbiol. 61, 592–601. 14
Kjeldsen, P., 1996: Landfill gas migration in soil. Landfilling of waste: Biogas., 15
Christensen, T.H., Cossu, R.,Stegmann, R., Eds., E. & FN Spon. 16
Kolb, S., Knief, C., Stubner, S., Conrad, R., 2003. Quantitative detection of 17
methanotrophsin soil by novel pmoA-targeted real-time PCR assays. Appl. Envir. 18
Microbiol. 69, 2423-2429. 19
Maurice, C., Lagerkvist, A., 2004. Assessment of methane oxidationcapacity ofsoil. 20
Waste Manage. Res. 22, 42-48. 21
Nastev, M., Therrien, R., Lefebvre, R., Gelinas, P., 2001. Gas production and migration 1
inlandfillsand geological materials.Journal of Contaminant Hydrology 1095, 2
187–211. 3
Page, A.L., Miller, R.H., Keeney, D.R., 1982. Methods of soil analysis. 2nd ed. Vol. 2, 4
Chemical and microbiological properties, Madison, Wisconsin. 5
Park, J.R., Moon, S., Ahn, Y.M., Kim, J.Y., Nam, K., 2005. Determination of 6
environmentalfactorsinfluencing methane oxidationin asandylandfill cover 7
soil. Environ. Technol. 26, 93–102. 8
Pawlowska, M., Stepniewski, W., 2006. Aninfluence of methaneconcentration onthe 9
methanotrophic activity of a model landfill cover. Ecol. Eng. 2 6, 392-395. 10
Spokas, K., Bogner, J., Chanton, J.P., Morcet, M., Aran, C., Graff, C., Moreau-Le 11
Golvan, Y., Hebe, I., 2006. Methane mass balance at three landfill sites: What is 12
the efficiency of capture by gas collection systems? Waste Manage. 26, 516–525. 13
Stein, V.B., Hettiaratchi, J.P.A., 2001. Methane oxidation in three Alberta soils: 14
Influence of soil parameters and methane flux rate. Environ. Tech. 22, 101–111. 15
Svenning, M.M., Wartiainen, I., Hestnes, A.G., Binnerup, S.J., 2003. Isolation of 16
methane oxidizing bacteria from soil by use of a soil substrate membrane system. 17
FEMS Microbiol Ecol 44, 347–354. 18
Theisen, A., Ali, M., Radajewski, S., Dumont, M., Dunfield, P.F., McDonald,I.R., 19
Dedysh, S.N., Miguez, C.B., Murrell, J., 2005. Regulation of methane oxidation 20
in the facultative methanotroph Methylocella silvestris BL2. Mol Microbiol : 58, 21
682–692. 22
Visvanathan, C., Pokhrel, D., Cheimchaisri, W., Hettiaratchi, J.P., Wu, J.S., 1999. 1
Methanothropicactivitiesintropicallandfillcoversoils: Effects oftemperature, 2
moisture content and methane concentration. Waste Manage. Res. 17, 313–323. 3
Whalen, S.C., Reeburgh, W.S., Sandbeck, K.A., 1990. Rapid methane oxidationina 4
landfill cover soil. Appl.Environ. Microbiol. 56, 3405-3411. 5
Whittenbury, R., Phillips, C., Wilkinson, T.F., 1970. Enrichment,isolation andsome 6
properties of methane utilizing bacteria. J. Gen. Microbiol. 60, 205-218. 7
Wilshusen, J.P., Hettiaratchi, J.P.A., Stein, V.B., 2004. Long-term behavior of passively 8
aerated compost methanotrophic biofilter columns. Waste Manage. 24, 643-653. 9
10 11 12
Figurelegends 1
Figure 1 – (A) Lateral cross-section of PMOB-1 and (B) profileoftheinstalled probes 2
3
Figure 2 - Temporal evolution of the barometric pressure, wind speed, precipitation and 4
airtemperature duringthe monitoring period 5
6
Figure 3 - Temporal evolution ofthe profiles oftemperature and water content withinthe 7
PMOB 8
9
Figure 4- Temporalevolution ofthe profiles of CH4and O2concentrations withinthe
10
PMOB 11
12
Figure 5 - Temporal evolution of pH, colony forming unit (CFU) of methanotrophs and 13
number of pmoA copy withinthe PMOB 14
15 16 17
.
103
102
,
101
100
• Barome
tr
irc
pressure
W
ind
speed
20
15
10
5
1.2
- - - -- 25
0
.8
0
.4
• Prec
ip
i
ta
t
ion
A
ir
tempera
tur
e
20
15
10
5
0.
0, = �
. .
. M a - i M t 1 � - .
�
.
0
,
F
igure 2
-
Tempora
l
evo
lu
t
ion
o
f
the
barome
tr
ic
pressure
,
w
ind
speed
,
prec
ip
i
ta
t
ion
and
a
ir
tempera
ture
dur
ing
the
mon
i
tor
ing
per
iod
Figure 2
Figure 5
