The use of volcanic soil as mineral landfill liner--III. Heavy metals retention capacity.

The volcanic soil of Southern Chile was tested for its heavy metal retention capacity. The maximum uptakes for CrO4(2-) (CrVI), Cu(2+), Zn(2+) and Pb(2+) were determined to be 2.74, 5.32, 5.86 and 7.44 mg g(-1), respectively. At a slightly alkaline pH value (7.5), it seems that a precipitation-adsorption process was responsible for the Cu(2+) and Zn(2+) uptake onto volcanic soil. All the determined values are of the same order of magnitude as natural zeolites heavy metals adsorption capacities. In addition, the heavy metals diffusion model through a 1 m volcanic soil mineral liner shows breakthrough times of 21.6, 10.2 and 8.9 years, for Pb(2+), Zn(2+) and Cu(2+), respectively, confirming the trend obtained in the adsorption isotherms. The natural volcanic soil of Southern Chile is an interesting material for possible use as landfill mineral basal sealing. It has an appropriate sealing potential (average Kf value of 5.85 x 10(-9) m s(-1)) and a heavy metals retention capacity comparable with natural zeolites. About two-thirds of the agricultural land in Chile (approximately 0.4 million km2) is derived from volcanic ash, suggesting an important soil volume for future landfill projects, that could be obtained in sufficient quantities from urban building activities.     

Improving the adsorption capacity and solid structure of natural volcanic soil using a foaming-sintering process based on recycled polyethylene terephthalate (PET).

The volcanic soils of southern Chile have demonstrated a high capacity to adsorb environmental pollutants, but for an industrial application, a stable solid material is necessary. The objective of this work was to produce a stable ceramic material through a process involving volcanic soil-polyurethane foam produced with recycled polyethylene terephthalate (PET)-polyols, and further thermal treatment. The selected foam formulation with 35.4% volcanic soil (< 63 microm) seems to be the most suitable for thermal treatment, with temperature steps at 700, 850, 1000 and 1200 degrees C. The porous ceramic material obtained has a stable solid form and an improved chlorophenols adsorption capacity (comparable to natural zeolites) that makes it suitable for advanced wastewater treatment and landfill leachate depuration.     

Effectiveness of compacted soil liner as a gas barrier layer in the landfill final cover system

A compacted soil liner (CSL) has been widely used as a single barrier layer or a part of composite barrier layer in the landfill final cover system to prevent water infiltration into solid wastes for its acceptable hydraulic permeability. This study was conducted to test whether the CSL was also effective in prohibiting landfill gas emissions. For this purpose, three different compaction methods (i.e., reduced, standard, and modified Proctor methods) were used to prepare the soil specimens, with nitrogen as gas, and with water and heptane as liquid permeants. Measured gas permeability ranged from 2.03x10(-10) to 4.96x10(-9)cm(2), which was a magnitude of two or three orders greater than hydraulic permeability (9.60x10(-13) to 1.05x10(-11)cm(2)). The difference between gas and hydraulic permeabilities can be explained by gas slippage, which makes gas more permeable, and by soil-water interaction, which impedes water flow and then makes water less permeable. This explanation was also supported by the result that a liquid permeability measured with heptane as a non-polar liquid was similar to the intrinsic gas permeability. The data demonstrate that hydraulic requirement for the CSL is not enough to control the gas emissions from a landfill.     

Water regime of mechanical-biological pretreated waste materials under fast-growing trees.

In this study mechanical-biological pre-treated waste material (MBP) was tested for suitability to serve as an alternative surface layer in combination with fast-growing and water-consumptive trees for final covers at landfill sites. The aim was to quantify evapotranspiration and seepage losses by numerical model simulations for two sites in Germany. In addition, the leaf area index (LAI) of six tree species over the growing season as the driving parameter for transpiration calculations was determined experimentally. The maximum LAI varied between 3.8 and 6.1 m2 m(-2) for poplar and willow clones, respectively. The evapotranspiration calculations revealed that the use of MBP waste material for re-cultivation enhanced evapotranspiration by 40 mm year(-1) (10%) over an 11 year calculation period compared to a standard mineral soil. Between 82% (for LAI(max) = 3.8) and 87% (for LAI(max) = 6.1) of the average annual precipitation (506 mm) could be retained from the surface layer assuming eastern German climate conditions, compared with a retention efficiency between 79 and 82% for a mineral soil. Although a MBP layer in conjunction with water-consumptive trees can reduce vertical water losses as compared to mineral substrates, the effect is not sufficient to meet legal regulations.     

Potential use of lateritic and marine clay soils as landfill liners to retain heavy metals

The potential of a lateritic soil and a marine clay, typical of those found in hot and humid climatic regions, was assessed for use as a landfill liner material. A series of tests were conducted - physical and chemical, batch adsorption, column, hydraulic conductivity, etc., - to evaluate the heavy metal sorption capacity, chemical compatibility of hydraulic conductivity, and transport parameters of the soils. Experimental results showed that the marine clay had better adsorption capacity than that of the lateritic soil and that its hydraulic conductivity was an order of magnitude lower. In addition, the hydraulic conductivities of both soils when permeated with low concentration heavy metal solutions were below 1x10(-7)cm/s. When permeated with Cr, Pb, Cd, Zn, and Ni solutions, the retardation factors of the lateritic soil and the marine clay ranged from 10 to 98 and 37 to 165, respectively, while the diffusion coefficients ranged from 1.0x10(-5) to 7.5x10(-6) and 3.0 to 9.14x10(-7)cm2/s, respectively. For both soils, Cr and Pb were retained relatively well, while Cd, Zn, and Ni were more mobile. The marine clay had higher retardation factors and lower diffusion coefficients, and its hydraulic conductivity was more compatible with Cr solution, than that of the lateritic soil. In general, the properties of the marine clay indicate that it has significant advantages over the lateritic soil as landfill liner material.     

Assessing the use of poplar tree systems as a landfill evapotranspiration barrier with the SHAW model.

The use of poplar tree systems (PTS) as evapotranspiration barriers on decommissioned landfills is gaining attention as an option for leachate management. This study involved field-testing the Simultaneous Heat and Water (SHAW) model for its ability to reliably estimate poplar transpiration, volumetric soil water content, and soil temperature at a landfill located in southern Ontario, Canada. The model was then used to estimate deep drainage and to ascertain the influence of a young PTS on the soil water balance of the landfill cover. The SHAW model tended to underestimate poplar transpiration [mean difference (MD) ranged from 0.33 to 3.55 mm on a daily total basis] and overestimate volumetric soil water content by up to 0.10 m3 m(-3). The model estimated soil temperature very well, particularly in the upper 1 m of the landfill cover (MD ranged from -0.1 to 1.6 x degrees C in this layer). The SHAW model simulations showed that deep drainage decreased appreciably with the presence of a young PTS largely through increased interception of rainfall, and that PTS have a good potential to act as effective evapotranspiration barriers in northern temperate climate zones.     

Atmospheric emissions and attenuation of non-methane organic compounds in cover soils at a French landfill

In addition to methane (CH(4)) and carbon dioxide (CO(2)), landfill gas may contain more than 200 non-methane organic compounds (NMOCs) including C(2+)-alkanes, aromatics, and halogenated hydrocarbons. Although the trace components make up less than 1% v/v of typical landfill gas, they may exert a disproportionate environmental burden. The objective of this work was to study the dynamics of CH(4) and NMOCs in the landfill cover soils overlying two types of gas collection systems: a conventional gas collection system with vertical wells and an innovative horizontal gas collection layer consisting of permeable gravel with a geomembrane above it. The 47 NMOCs quantified in the landfill gas samples included primarily alkanes (C(2)-C(10)), alkenes (C(2)-C(4)), halogenated hydrocarbons (including (hydro)chlorofluorocarbons ((H)CFCs)), and aromatic hydrocarbons (BTEXs). In general, both CH(4) and NMOC fluxes were all very small with positive and negative fluxes. The highest percentages of positive fluxes in this study (considering all quantified species) were observed at the hotspots, located mainly along cell perimeters of the conventional cell. The capacity of the cover soil for NMOC oxidation was investigated in microcosms incubated with CH(4) and oxygen (O(2)). The cover soil showed a relatively high capacity for CH(4) oxidation and simultaneous co-oxidation of the halogenated aliphatic compounds, especially at the conventional cell. Fully substituted carbons (TeCM, PCE, CFC-11, CFC-12, CFC-113, HFC-134a, and HCFC-141b) were not degraded in the presence of CH(4) and O(2). Benzene and toluene were also degraded with relative high rates. This study demonstrates that landfill soil covers show a significant potential for CH(4) oxidation and co-oxidation of NMOCs.     

Wet landfill decomposition rate determination using methane yield results for excavated waste samples

An increasing number of landfills are operated to accelerate waste decomposition through liquids addition (e.g., leachate recirculation) as a wet landfill. Landfill design and regulation often depend on utilizing landfill gas production models that require an estimate of a first-order gas generation rate constant, k. Consequently, several studies have estimated k using collected gas volumes from operating wet landfills. Research was conducted to examine an alternative approach in which k is estimated not from collected landfill gas but from solid waste samples collected over time and analyzed for remaining gas yield. To achieve this goal, waste samples were collected from 1990 through 2007 at two full-scale landfills in Florida that practiced liquids addition. Methane yields were measured from waste samples collected over time, including periods before and after leachate recirculation, and the results were applied to a first-order decay model to estimate rate constants for each of the sites. An initial, intensive processing step was conducted to exclude non-biodegradable components from the methane yield testing procedure. The resulting rate constants for the two landfills examined were 0.47 yr(-1) and 0.21 yr(-1). These results expectedly exceeded the United States Environmental Protection Agency's rate constants for dry and conventional landfills (0.02-0.05 yr(-1)), but they are comparable to wet landfill rate constants derived using landfill gas data (0.1-0.3 yr(-1)).     

Environmental impact assessment on the construction and operation of municipal solid waste sanitary landfills in developing countries: China case study

An inventory of material and energy consumption during the construction and operation (C&O) of a typical sanitary landfill site in China was calculated based on Chinese industrial standards for landfill management and design reports. The environmental impacts of landfill C&O were evaluated through life cycle assessment (LCA). The amounts of materials and energy used during this type of undertaking in China are comparable to those in developed countries, except that the consumption of concrete and asphalt is significantly higher in China. A comparison of the normalized impact potential between landfill C&O and the total landfilling technology implies that the contribution of C&O to overall landfill emissions is not negligible. The non-toxic impacts induced by C&O can be attributed mainly to the consumption of diesel used for daily operation, while the toxic impacts are primarily due to the use of mineral materials. To test the influences of different landfill C&O approaches on environmental impacts, six baseline alternatives were assessed through sensitivity analysis. If geomembranes and geonets were utilized to replace daily and intermediate soil covers and gravel drainage systems, respectively, the environmental burdens of C&O could be mitigated by between 2% and 27%. During the LCA of landfill C&O, the research scope or system boundary has to be declared when referring to material consumption values taken from the literature; for example, the misapplication of data could lead to an underestimation of diesel consumption by 60–80%.     

Kinetics of microbial landfill methane oxidation in biofilters

A methane oxidizing biofilter system fitted to the passive venting system of a harbor sludge landfill in Germany was characterized with respect to the the methanotrophic population, methane oxidizing capacity, and reaction kinetics. Methanotrophic cell counts stabilized on a high level with 1.3 x 10(8) to 7.1 x 10(9) cells g dw(-1) about one year after first biofilter operation, and a maximum of 1.2 x 10(11) cells g dw(-1). Potential methane oxidizing activity varied between 5.3 and 10.7 microg h(-1) g dw(-1). Cell numbers correlated well with methane oxidation activities. Extrapolation of potential activities gave methane removal rates between 35 and 109 g CH4 h(-1) m(-3), calculated for 30 degrees C. Optimum temperature was 38 degrees C for freshly sampled biofilter material and 22 degrees C for a methanotrophic enrichment culture grown at 10 degrees C incubation temperature. Substrate kinetics revealed the presence of a low-affinity methane oxidizing community with a high Vmax of 1.78 micromol CH4 h(-1) g ww(-1) and a high K(M) of 15.1 microM. K(MO2) for methane oxidation was 58 microM. No substantial methane oxidizing activity was detected below 1.7-2.6 vol.-% O2 in the gaseous phase. Methane deprivation led to a decrease in methane oxidation activity within 5-9 weeks but could still be detected after 25 weeks of substrate deprivation and was fully restored within 3 weeks of continuous methane supply. Very high salt loads are leached from the novel biofilter material, expanded clay, yielding electric conductivity values of up to 15 mS cm(-1) in the leachate. Values > 6 mS cm(-1) were shown to depress methane consumption. Water retention characteristics of the material proved to be favourable for methane oxidizing systems with a gas permeable volume of 78% of bulk volume at field capacity water content. Correspondingly, no influence of water content on methane oxidation activity could be detected at water contents between 2.5 and 20 vol.-%.     

Hydrological performance of MSW incineration residues and MSW co-disposed with sludge in full-scale cells

Water flows were analysed for the filling phase and the first 4 years after closure of two types of full-scale landfill cells: 'special cells' containing mostly fly ash from municipal solid waste (MSW) incineration disposed with other special/hazardous waste, and 'biocells' (biological cells) containing co-disposed MSW and food industry sludge. The landfill cells were constructed about -1.5 m above sea level (masl) at Lomma Bay, southern Sweden. The hydrological effects of water intrusion into the special cells from surroundings and sludge moisture within the biocells were studied. HELP modelling of hydrological processes predicted delay in peaks of leachate generation from uncovered special cells following rain, which was not confirmed. Faster leachate production as a response to rainfall from special cells than from biocells was observed. It was inferred that special waste has more intensive channelling, lower water absorption and higher hydraulic conductivity than mixtures of sludge/MSW. To avoid convergence problems in modelling uncovered special cells, the use of a 5 cm deep top layer with saturated hydraulic conductivity 1.7 x 10(-3) cm s(-1), porosity 0.437, and field capacity 0.105, is suggested.     

A RE-EVALUATION OF OBJECTIONS TO TREE PLANTING ON CONTAINMENT LANDFILLS

Legislation from developed countries indicates that planting trees on containment landfills is generally forbidden. Concerns centre on the supposition that tree roots can penetrate into and through capping materials, and will thus compromise control of water ingress into waste, and allow the escape of landfill gas. An associated anxiety is that if roots penetrate a clay cap they could cause desiccation and cracking of the clay through excessive moisture abstraction. It is also considered that trees growing on the relatively shallow soil above a landfill cap could be especially prone to uprooting. However, a review of the world literature indicates that maximum depths achieved by tree roots are usually between 1–2 m. Almost 90% of a tree's roots may be found in the upper 0.6 m of soil. Tree roots are highly sensitive to environmental conditions and their downward penetration can be restricted by a number of soil factors including compaction, poor aeration and infertility. A detailed study of these factors indicates that the materials used for capping landfill sites, such as HDPE (high density polyethylene) and compacted clays, can provide an effective barrier to downward root growth. The available information also suggests that tree roots are extremely unlikely to be a primary cause of desiccation cracking in a clay cap owing to their inability to extract more than about one-quarter of the total moisture held in a clay of the density required to ensure a permeability of 1×10⁻⁹m s⁻¹. Trees growing on landfill sites with a rootable soil depth of at least 1.5 m should be at no greater risk of windthrow than most forest trees on undisturbed sites. Methods are available to assess the likelihood of windthrow. In any event, windthrow should not cause disruption of a cap, due to the inability of tree roots to penetrate HDPE, or mineral materials compacted to a bulk density of 1.8 g cm⁻³.     

The controlling of landfill leachate evapotranspiration from soil-plant systems with willow: Salix amygdalina L.

The use of willows (Salix amygdalina L) to manage landfill leachate disposal is an effective and cost-effective method due to the high transpiration ability of the willow plants. A 2-year lysimetric experiment was performed to determine an optimum leachate hydraulic loading rate to achieve high evapotranspiration but exert no harmful influence on the plants. The evapotranspiration rate of a soil-plant system planted with the willow was 1.28-5.12-fold higher than the rate measured on a soil surface lacking vegetation, suggesting that soil-willow systems with high volatilization rates are a viable landfill leachate treatment method. Of the soil-willow systems, the one with willow growing on sand amended with sewage sludge soil at an hydraulic loading rate of 1 mm day(-1) performed best, with evapotranspiration ranging from 2.25 to 3.02 mm day(-1) and a biomass yield of 8.0-9.85 Mg dry matter ha(-1). The organic fraction of the soil increased as much as 2.5% of dry matter, due to the sewage sludge input, which exerted a positive effect on the biomass yield as well as on transpiration and evaporation. It was observed that the plants in the sand-and-sewage sludge soil systems displayed higher resistance to toxic effects from the applied landfill leachate relative to plants in the sand-soil systems.     

Micrometeorological measurements of N2O and CH4 emissions from a municipal solid waste landfill.

Micrometeorological measurements of methane (CH4) and nitrous oxide (N2O) emissions were made at the decommissioned Park Road Landfill in Grimsby, Ontario, Canada between June and August 2002. The influence of precipitation, air temperature, wind speed and barometric pressure on the temporal variability of landfill biogas emissions was assessed. Gas flux measurements were obtained using a micrometeorological mass balance measurement technique [integrated horizontal flux (IHF)] in conjunction with two tunable diode laser trace gas analyser (TDLTGA) systems. This method allows for continuous, non-intrusive measurements of gas flux at high temporal resolution. Mean fluxes of N2O were negligible over the duration of the study (-0.23 to 0.02 microg m(-2) s(-1)). In contrast, mean emissions of CH4 were much greater (80.4 to 450.8 microg m(-2) s(-1)) and varied both spatially and temporally. Spatial variations in CH4 fluxes were observed between grass kill areas (biogas 'hot spots') and the densely grass-covered areas of the landfill. Temporal variations in CH4 fluxes were also observed, due at least in part to barometric pressure, wind speed and precipitation effects.     

The influence of atmospheric pressure on landfill methane emissions

Landfills are the largest source of anthropogenic methane (CH4) emissions to the atmosphere in the United States. However, few measurements of whole landfill CH4 emissions have been reported. Here, we present the results of a multi-season study of whole landfill CH4 emissions using atmospheric tracer methods at the Nashua, New Hampshire Municipal landfill in the northeastern United States. The measurement data include 12 individual emission tests, each test consisting of 5-8 plume measurements. Measured emissions were negatively correlated with surface atmospheric pressure and ranged from 7.3 to 26.5 m3 CH4 min(-1). A simple regression model of our results was used to calculate an annual emission rate of 8.4 x 10(6) m3 CH4 year(-1). These data, along with CH4 oxidation estimates based on emitted landfill gas isotopic characteristics and gas collection data, were used to estimate annual CH4 generation at this landfill. A reported gas collection rate of 7.1 x 10(6) m3 CH4 year(-1) and an estimated annual rate of CH4 oxidation by cover soils of 1.2 x 10(6) m3 CH4 year(-1) resulted in a calculated annual CH4 generation rate of 16.7 x 10(6) m3 CH4 year(-1). These results underscore the necessity of understanding a landfill's dynamic environment before assessing long-term emissions potential.     

Tree establishment and growth at Pitsea landfill site,Essex, U.K.

Investigations at an 11-year-old landfill site have shown that soil moisture was positively, and soil oxygen was negatively correlated with temperature and concentration of soil methane generated by decomposition of the underlying landfill materials. A thin (0.2 m) cover of soil-forming material over the landfill showed acute oxygen deficiency and high temperatures. The high moisture content of this cover was probably caused by upward movement of water from within the landfill across a temperature gradient. Nearly all the trees of five species on the thinnest (0.2 m) cover died, but survival and growth was markedly improved on 1.5 m additional clay cover over the landfill. This material prevented landfill gas contamination, and also contained sufficient plant-available soil moisture to negate the large soil moisture deficits the area experiences in most summers. The evidence presented shows that landfill sites are dynamic in the distribution of landfill temperature and gas emissions and the planning of tree planting schemes should take this into account.     

Simulation model for gas diffusion and methane oxidation in landfill cover soils

Landfill cover soils oxidize a considerable fraction of the methane produced by landfilled waste. Despite many efforts this oxidation is still poorly quantified. In order to reduce the uncertainties associated with methane oxidation in landfill cover soils, a simulation model was developed that incorporates Stefan-Maxwell diffusion, methane oxidation, and methanotrophic growth. The growth model was calibrated to laboratory data from an earlier study. There was an excellent agreement between the model and the experimental data. Therefore, the model is highly applicable to laboratory column studies, but it has not been validated with field data. A sensitivity analysis showed that the model is most sensitive to the parameter expressing the maximum attainable methanotrophic activity of the soil. Temperature and soil moisture are predicted to be the environmental factors affecting the methane oxidizing capacity of a landfill cover soil the most. Once validated with field data, the model will enable a year-round estimate of the methane oxidizing capacity of a landfill cover soil.     

Alkaline solution neutralization capacity of soil

Alkaline eluate from municipal solid waste (MSW) incineration residue deposited in landfill alkalizes waste and soil layers. From the viewpoint of accelerating stability and preventing heavy metal elution, pH of the landfill layer (waste and daily cover soil) should be controlled. On the other hand, pH of leachate from existing MSW landfill sites is usually approximately neutral. One of the reasons is that daily cover soil can neutralize alkaline solution containing Ca²⁺ as cation. However, in landfill layer where various types of wastes and reactions should be taken into consideration, the ability to neutralize alkaline solutions other than Ca(OH)₂ by soil should be evaluated. In this study, the neutralization capacities of various types of soils were measured using Ca(OH)₂ and NaOH solutions. Each soil used in this study showed approximately the same capacity to neutralize both alkaline solutions of Ca(OH)₂ and NaOH. The cation exchange capacity was less than 30% of the maximum alkali neutralization capacity obtained by the titration test. The mechanism of neutralization by the pH-dependent charge can explain the same neutralization capacities of the soils. Although further investigation on the neutralization capacity of the soils for alkaline substances other than NaOH is required, daily cover soil could serve as a buffer zone for alkaline leachates containing Ca(OH)₂ or other alkaline substances.     

Assessment of the methane oxidation capacity of compacted soils intended for use as landfill cover materials

The microbial oxidation of methane in engineered cover soils is considered a potent option for the mitigation of emissions from old landfills or sites containing wastes of low methane generation rates. A laboratory column study was conducted in order to derive design criteria that enable construction of an effective methane oxidising cover from the range of soils that are available to the landfill operator. Therefore, the methane oxidation capacity of different soils was assessed under simulated landfill conditions. Five sandy potential landfill top cover materials with varying contents of silt and clay were investigated with respect to methane oxidation and corresponding soil gas composition over a period of four months. The soils were compacted to 95% of their specific proctor density, resulting in bulk densities of 1.4-1.7 g cm⁻³, reflecting considerably unfavourable conditions for methane oxidation due to reduced air-filled porosity. The soil water content was adjusted to field capacity, resulting in water contents ranging from 16.2 to 48.5 vol.%. The investigated inlet fluxes ranged from 25 to about 100 g CH₄ m⁻² d⁻¹, covering the methane load proposed to allow for complete oxidation in landfill covers under Western European climate conditions and hence being suggested as a criterion for release from aftercare. The vertical distribution of gas concentrations, methane flux balances as well as stable carbon isotope studies allowed for clear process identifications. Higher inlet fluxes led to a reduction of the aerated zone, an increase in the absolute methane oxidation rate and a decline of the relative proportion of oxidized methane. For each material, a specific maximum oxidation rate was determined, which varied between 20 and 95 g CH₄ m⁻² d⁻¹ and which was positively correlated to the air-filled porosity of the soil. Methane oxidation efficiencies and gas profile data imply a strong link between oxidation capacity and diffusive ingress of atmospheric air. For one material with elevated levels of fine particles and high organic matter content, methane production impeded the quantification of methane oxidation potentials. Regarding the design of landfill cover layers it was concluded that the magnitude of the expected methane load, the texture and expected compaction of the cover material are key variables that need to be known. Based on these, a column study can serve as an appropriate testing system to determine the methane oxidation capacity of a soil intended as landfill cover material.     

Spatial variability of soil gas concentration and methane oxidation capacity in landfill covers

In order to devise design criteria for biocovers intended to enhance the microbial oxidation of landfill methane it is critical to understand the factors influencing gas migration and methane oxidation in landfill cover soils. On an old municipal solid waste landfill in north-western Germany soil gas concentrations (10, 40, 90 cm depth), topsoil methane oxidation capacity and soil properties were surveyed at 40 locations along a 16 m grid. As soil properties determine gas flow patterns it was hypothesized that the variability in soil gas composition and the subsequent methanotrophic activity would correspond to the variability of soil properties. Methanotrophic activity was found to be subject to high spatial variability, with values ranging between 0.17 and 9.80 g CH₄ m⁻² h⁻¹_. Considering the current gas production rate of 0.03 g CH₄ m⁻² h⁻¹, the oxidation capacity at all sampled locations clearly exceeded the flux to the cover, and can be regarded as an effective instrument for mitigating methane fluxes. The methane concentration in the cover showed a high spatial heterogeneity with values between 0.01 and 0.32 vol.% (10 cm depth), 22.52 vol.% (40 cm), and 36.85 vol.% (90 cm). The exposure to methane raised the oxidation capacity, suggested by a statistical correlation to an increase in methane concentration at 90 cm depth. Methane oxidation capacity was further affected by the methanotroph bacteria pH optimum and nutrient availability, and increased with decreasing pH towards neutrality, and increased with soluble ion concentration). Soil methane and carbon dioxide concentration increased with lower flow resistance of the cover, as represented by the soil properties of a reduced bulk density, increase in air capacity and in relative ground level.