Landfill Cover Material Research Articles

Evolution of solidified municipal sludge used as landfill cover material under wet–dry cycles: mechanical characteristics, microstructural, and seepage properties

Evolution of solidified municipal sludge used as landfill cover material under wet–dry cycles: mechanical characteristics, microstructural, and seepage properties

Performance of fibre-reinforced landfill mined soil like fraction as an environment friendly fill material

Landfill mining is emerging as an effective strategy towards mitigation of the problems associated with legacy landfills. About 40–80% of the landfill mined waste is soil-like fraction (landfill mined soil like fraction, LMSF) that is obtained after removing the combustibles and recyclables. However, due to its lower calorific value and presence of organic content, LMSF has not found many applications except landfill cover material and filling of low-lying areas. In this context, the present study explores the strength properties of LMSF with and without fibres (coir and polypropylene fibres) through unconfined compression, direct shear, UU triaxial, cyclic UU triaxial, indirect tension and bending strength tests. Overall, the shear strength properties of LMSF are similar to sand with some cohesion. Further, the performance of LMSF with optimum fibre proportion (2% for coir fibres and 1.5% for polypropylene fibres) is quite superior under monotonic and cyclic compressive loading conditions, as well as indirect tension and flexural loading conditions. An assessment of 1 m replacement of soft soil with LMSF with/without fibre reinforcement infers substantial increase in the allowable bearing pressure of LMSF. Overall, though LMSF may need assessment/pre-treatment (as required) due to presence of organic content and any possible heavy metal concentration, utilization of LMSF would encourage the adoption of landfill mining process. The current research insights contribute in the direction of achieving sustainable infrastructure development by reduction in the landfill area that would reduce the depletion of conventionally utilized natural resources for fill applications such as sand and gravel, and contribute positively towards environment.

Utilization of incineration ash as a construction material: A review

Municipal solid waste incineration (MSWI) which requires burning waste under controlled conditions is not new to India. The first plant was commissioned in the 1980 s. The obtained incineration residue comprises bottom ash (BA) and fly ash (FA), which require disposal in an environment-friendly manner. The BA primarily comprises SiO2. The study looked into the possibility of the usage of MSWI FA and BA as construction material. About 2.5% of generated ash is FA, while about 7.5% is BA. Each year, FA production exceeds 500 million tons, while BA production is expected at 1.5 billion tons. The presence of heavy metals, further calls for their eco-friendly management owing to the impacts they may have on the different forms of life. Despite having high strength it contains harmful substances, and it can be used in buildings. It is concluded that FA is rarely utilized in highway construction owing to the associated threat of heavy metals leaching, however, there is ample scope for its usage in cement manufacturing, cement concrete aggregate, ceramic and fertilizers, or as a soil improver. On the contrary, it has been reported that BA can be utilized in highway construction as it possesses strong mechanical characteristics and minimal leaching threat of heavy metals with certain pretreatment, it can also be used in cement concrete aggregates, ceramics, bricks, and as landfill cover material.

Effect of Bamboo biochar on strength and water retention properties of low plastic clay and silty sand

Biochar is a carbon-rich stable product derived from the thermochemical decomposition of biomass. The properties of biochar vary with types of feedstock, heating rate, pyrolysis temperature, etc. Consequently, the mechanical and hydrological properties of biochar amended soil (BAS) also differ with types of biochar and soils. However, the effect of bamboo biochar (BB) amendment on soil strength and water retention properties is missing in the previous literature. Bamboo biomass was pyrolysed at 600 °C to produce biochar. BB and soils (low plastic clay (CL) and silty sand (SM)) were mixed to prepare BAS. The samples were prepared by mixing BB in five ratios, i.e., 0%, 1%, 2%, 3.5% and 5% of dry soil weight. The biochar application has increased optimum moisture content, alkalinity (pH) and Atterberg limits, whereas, reduced maximum dry density and specific gravity of both the soils (CL and SM). The unconfined compressive strength (UCS) of CL soil was noted to increase by 10.5% with 2% biochar content and decreased after that, whereas the UCS of SM soil was found to decrease continuously with the biochar content increment. Therefore, the unconfined compressive strength (UCS) result showed that biochar application has contrary effects on both soils. The measured gravimetric water content (GWC) of BAS was increased with biochar increment in both soils. However, GWC increased more in CL than in SM soil at the same biochar content. The microstructural analysis showed that the biochar amendment filled the pore space of the soil matrix, resulting in an increase in UCS and GWC values. The increased water retention capacity and strength (UCS) of biochar amended CL soil provides evidence that it could be used as a landfill cover material.

A study on utilization of landfill mined soil like fraction for sustainable reduction in swelling and cracking potential for expansive and marine soils

Landfill mined soil like fraction (LMSF) is derived from mining of legacy landfill waste after removal of larger fraction such as construction debris, clothes, plastics and other recyclables, and accounts for significant proportion of the total legacy landfill waste. LMSF has found applications as landfill cover material; however, owing to its large quantity in many cities, there is a need to explore more applications for its utilization. In this context the present study explores the role of LMSF (filler replacement) with/without ultrafine slag, US (primary admixture) and lime, L (activator) in controlling the shrinkage and cracking of marine and expansive soils during drying. The ratio of the area of crack and shrinkage to total area of specimen, defined as crack and shrinkage intensity factor (CSIF), has been utilized for quantification of the cracking and shrinkage characteristics of soils with/without stabilization. Further, the effect of soil stabilization on the swelling potential (viz., free swell index and swelling pressure) has been evaluated for the soils. In the present study, complete crack mitigation for expansive soil has been achieved for the combination: 40%LMSF (<425 μm) + 50% expansive soil + 8%US + 2%L, while for the marine soil it has been achieved for combination: 40% LMSF (<425 μm/<2 mm) + 50% marine soil + 8.5%US + 1.5%L. The study findings are useful in the context of utilizing LMSF with sustainable admixtures for reducing cracking and swelling potential of soils for various infrastructure applications such as natural and stabilized slopes, embankment, canal bed and ponds.

Adsorption of the emerging pollutants on Buena Vista landfill cover material and implications on regional aquatic pollution

The occurrence of emerging pollutants in water represents a health risk for humans and the ecosystem. It has been shown that pollutant–soil interactions are determinants in preventing contamination of water sources by leachates from landfills. In this work, batch experiments were conducted to study the soil sorption process of amoxicillin (AMX), acetaminophen (ACP), levonorgestrel (LNG), and chlorothalonil (CTL) in four different soil layers used as cover material in Buena Vista landfill located in the municipality of La Union (Antioquia, Colombia). All soil layers were characterized using FT-IR, XRF and BET experimental techniques. In addition, pH and ionic strength effects on the adsorption process were also evaluated. The % of removal follows the order CTL > LNG > AMX > ACP in all soil layers. ACP y AMX adsorption was best described by pseudo-second-order kinetics, while LNG and CTL adsorption was best fitted by the pseudo-first-order kinetic model. Pollutant adsorptions were found to be favored at pH 6.3. Increasing the solution ionic strength decreases the adsorption of pollutants in all evaluated soil layers. The adsorption process was governed by hydrophilic and hydrophobic interactions. Polar molecules such as AMX and ACP remain in the aqueous phase while nonpolar LNG and CTL interact with clay minerals in the soil surface, presumably through van der Waals forces. Based on our findings, a cover material with both hydrophilic and lipophilic characteristics operating close to neutral, and with low ionic content, is advised for the Buena Vista landfill to improve its role as a barrier in decreasing potential pollutants contaminating groundwater sources.

Geostability of Dewatered Sludge as Landfill Cover Material

&lt;p&gt;Dewatered sludge is the main by-product from wastewater treatment and it contains various types of hazardous substances which can cause environmental pollution. The alternative utilization of sludge waste is for covering the landfill or as liner for the landfill. Landfill cover is a critical component to protect the surrounding environment from leachate contamination produced by landfills and it has specific characteristics. This study analyzes the optimum water content, permeability coefficient, and stability of the material consisting of a mixture of dewatered sludge, bentonite, and quicklime. The test results show that the optimum water content in the three composite variables meet the requirements; the highest optimum value was 28%, a mixture with a ratio of 84% sludge, 15% bentonite, and 1% quicklime. The results also show that mixing sewage sludge with bentonite significantly reduces the permeability value with a ratio of 80% sludge, and 20% bentonite produces the lowest permeability coefficient of 1.979 x 10-7 and this has reached the hydraulic conductivity limit of 1 x 10-7. The shear strength and safety factor results test show that V3 had the best results, with a cohesion value of 22.40 kPa, a shear angle of 31.97°, and a safety factor of 5.297. The addition of bentonite tends to reduce the value of the safety factor. This safety factor can reach a high value because of the ratio of the total shear resistance to the working soil shear stress.&lt;/p&gt;&#x0D;

In-situ removal of odorous NH3 and H2S by loess modified with biologically stabilized leachate

The loess regions distribute widely in Northwestern China, North America and Eastern Europe. For these regions, landfill is a suitable technology for solid waste treatment. However, as a landfill cover material, loess is not very effective in controlling the emission of malodorous gases. The present study modified loess with biologically stabilized leachate, and investigated the capacities and mechanisms of the modified loess to remove odorous NH3 and H2S. The removal rates of NH3 and H2S at different acclimation time, targeted gas concentrations and temperatures were measured. It was found that the NH3 removal rate of the modified loess was up to 0.08 μmol/(g·hr), which was 1.8 times that of the virgin loess. The H2S removal rate of the modified loess was up to 1.74 μmol/(g·hr), which was 1.25 times that of the virgin loess. The half-meter loess layer modified by biologically stabilized leachate achieved nearly 100% removal of H2S. The improvement of NH3 and H2S removal ability was mainly due to the enrichment of relevant microorganisms. This work proposed a novel method for in-situ control of malodorous pollutants in landfills in the loess regions, and proved that the in-situ removal of NH3 and H2S using the loess modified with biologically stabilized leachate is feasible and cost-effective.

Selection of Landfill Cover Materials Based on Data Envelopment Analysis (DEA)—A Case Study on Four Typical Covering Materials

Against the background of sustainable development, landfill covers can consist of a range of materials, from clay to geocomposite and polymer composites. Given engineering and environmental requirements, we analyzed the performance and sustainability of four sanitary landfill cover materials, namely clay, HDPE, PVC, and GCL. Within the principles of environmentally sustainable design, we constructed a material selection index based on the performance as well as the economic and environmental impacts of the materials. In addition, using a data envelopment analysis (DEA) model with an analytic hierarchical process (AHP) preference cone, we developed a C2WH model to evaluate the performance of the selected materials. Through the calculation, we found that the comprehensive indexes of the four covering materials were E1 = 0.2600, E2 = 0.5757, E3 = 0.7815, and E4 = 1.0000, respectively. Our results indicated that the investigated materials could be ranked according to performance as follows: GCL &gt; PVC &gt; HDPE &gt; clay. Thus, our results showed that GCL, with the highest efficiency value, was the optimal cover of the investigated materials. The multiobjective decision model developed in our study can be used as a technical reference and offers support for the selection of eco-friendly landfill cover materials.

Shear strength, water permeability and microstructure of modified municipal sludge based on industrial solid waste containing calcium used as landfill cover materials

In order to prepare a new type of landfill covering material for closure, we used industrial calcium-containing waste (slag, desulfurised gypsum and fly ash) to modify the municipal dewatered sludge. Shear, infiltration and rainfall infiltration model tests were performed to obtain the shear strength parameters of the modified sludge, the hydraulic conductivity during the wet-dry cycle, and the service performance against rainfall breakdown to evaluate the service performance of the modified sludge cover (MSC). Comprehensive characterisation of the modified sludge was analysed by XRD, FTIR and SEM-EDS to revealed the mineral structure, microstructure, and modification mechanism of the sludge. The MSC samples had high shear strength and shown the characteristics of evolving from plasticity to brittleness. After curing for 14 d, the values of cohesion c and internal friction angle φ reached 150.75–384.69 kPa and 37.60–57.29°, respectively. The MSC exhibited excellent anti-seepage service performance under dry and wet cycle conditions. Compared with traditional compacted clay, its hydraulic conductivity dropped by an order of magnitude, and after six wet and dry cycles, the hydraulic conductivity of the modified sludge reached stability at 1.4–7.2 × 10−7 cm/s. The 60-cm-thick MSC layer can completely withstand the impact of long-term rainfall during the rainy season in the middle reaches of the Yangtze River in China. Analysis results also show that the modification mechanism of the sludge could be ascribed to the generation of dense blocks and clusters of C-S-H and C-A-S-H gels originated from SiO2, Al2O3, and CaO phases in industrial calcium-containing waste and sludge by the activation of the alkali.

Mechanical Characteristics and Micro-Mechanism of Modified Dredged Sludge Based on Calcium-Containing Solid Waste Used as Landfill Cover Materials

In order to prepare a new type of landfill covering material for closure, we used industrial calcium-containing waste (construction rubbish, slag, desulfurized gypsum and fly ash) to modify the dredged urban sludge. Shrink, unconfined compression, shear and infiltration tests were performed to obtain the volume shrinkage, compressive strength, shear strength and permeability coefficient of the modified sludge, as well as the permeability coefficient under the action of wet and dry cycles. Comprehensive characterization of the modified sludge using X-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy with energy dispersive spectroscopy detection methods, resulted in the hydration products, molecular groups and microstructure characteristics of the modified sludge and revealed the modification mechanism of calcium-containing waste to sludge. After natural curing for 28 d, the volume shrinkage rate of the modified sludge sample was 2.6~8.3%, the unconfined compressive strength was 7.9~14.5 MPa, the cohesion force c was 179~329 kPa, and the internal friction angle φ was 42.59~53.60°. After six wet and dry cycles, there were no cracks in the modified sludge; the permeability coefficient of the modified sludge reached stability at 0.84–11.1 × 10−7 cm/s; and the permeability coefficient of MS7 sample was less than 1 × 10−7 cm/s, which met the engineering anti-seepage requirements of the landfill closure cover. The industrial calcium-containing waste by alkali formed C–S–H and C–A–S–H gelled geopolymer, which filled the gaps between soil particles to form a strong soil cement skeleton. Therefore, the mix ratio of sludge:construction waste:slag:fly ash:desulfurized gypsum was 50:22:15:8:5. Calcium-containing solid waste modified sludge can be used as a cover material for landfill closure.

Carbon isotopic characterisation and oxidation of UK landfill methane emissions by atmospheric measurements.

Biological oxidation of methane in landfill cover material can be calculated from the carbon isotopic signature (δ13CCH4) of emitted CH4. Enhanced microbial consumption of methane in the aerobic portion of the landfill cover is indicated by a shift to heavier (less depleted) isotopic values in the residual methane emitted to air. This study was conducted at four landfill sites in southwest England. Measurement of CH4 using a mobile vehicle mounted instrument at the four sites was coupled with Flexfoil bag sampling of ambient air for high-precision isotope analysis. Gas well collection systems were sampled to estimate landfill oxidised proportion. Closed or active status, seasonal variation, cap stripping and site closure impact on landfill isotopic signature were also assessed. The δ13CCH4 values ranged from -60 to -54‰, with an average value of -57±2‰. Methane emissions from active cells are more depleted in 13C than closed sites. Methane oxidation, estimated from the isotope fractionation, ranged from 2.6 to 38.2%, with mean values of 9.5% for active and 16.2% for closed landfills, indicating that oxidised proportion is highly site specific.

Applicability of Recycled Soil Mixed with Bentonite and Polymer as a Waste Landfill Liner

Waste landfill liner has been developed with a variety of materials, but the landfill liner and cover material have not been developed in consideration of the local conditions. In order to build a cost effective municipal solid waste (MSW) landfill site, it is necessary to develop technology that utilizes materials suitable for local characteristics as liner. The purpose of this study is to develop an amended compacted clay liner (CCL) by proportionally mixing construction waste soil called “recycled soil” with small amount bentonite powder as well as polymer powder. Permeability and strength characteristics of recycled soil-bentonite mixture were analyzed through laboratory test and then compare this mixture with characteristics of marine clay-bentonite mixture. The characteristics of strength and permeability were analyzed by applying different mixing ratios with adjustment of polymer and bentonite ratios in consideration of its proportion of bentonite’s weight to improve economic efficiency and increase the strength of recycled soil-bentonite mixture. Finally, the proper mixing ratio of recycled soil-4% bentonite-0.28% polymer mixture was determined considering economical efficiency. The mixture was confirmed to be suitable as lining material based on the results of dry shrinkage test, free swelling test, and soil contamination test. In this study, it is proposed the mixing ratio of recycled soil, bentonite, and polymer as a minimum ratio that satisfies the standard of hydraulic conductivity(1 × 10−7 cm/sec) on the waste management law and unconfined compressive strength (500 kPa) on the specification of construction of waste landfill liner.

Influence of feedstock type and particle size on efficiency of biochar in improving tensile crack resistance and shear strength in lean clayey soil

The development of tensile stress can cause desiccation cracks, further increasing infiltration and inducing instability in green infrastructure (slopes and landfill liners). Recent research has promoted the use of biochar (i.e., stable carbon with a life period of more than 500 years) as an eco-friendly material that can provide simultaneous benefits in reducing tensile stresses and crack development, aiming to enhance landfill cover longevity. However, there is a lack of guidelines and criteria for selecting biochar (feedstock type and particle size) as landfill cover material. This study aims to investigate the effects of biochar particle size and feedstock type on cracking of soil. Two contrasting feedstock types (i.e., pig manure-based and wood-based) have been selected for amendment on lean clay soil. Laboratory experiments were conducted to monitor the cracks. The results show that wood biochar (WB) is more efficient in crack reduction than pig manure biochar (PMB). Moreover, it has been observed that fine-grained biochar is more suspectable to cracks formation regardless of biochar type. The cohesion and internal friction angle of biochar are dependent on the surface morphology of biochar. WB has more angularity and sharp edges, which can increase interlocking in soil, thereby enhancing shear resistance and, hence, soil stability. The comprehensive study can help narrow down the selectivity of biochar and its specifications to mitigate cracks and enhance the strength of landfill cover.

Enhancement of CH4 oxidation potential in bio-based landfill cover materials

This study evaluated the efficacy of two compost materials, yard waste and leaf compost (YWLC) and biosolids compost (BSC), as bio-based landfill cover materials for oxidizing methane (CH4). A series of laboratory batch incubations were conducted to assess the CH4 oxidation potential of the composts and potential enhancement of CH4 oxidation under different conditions. Higher initial rates of CH4 oxidation were yielded in a sample of YWLC cured beyond the maturity standard at the compost site due to a reduction in raBOD and subsequent reduction in heterotrophic competition for oxygen. Results showed that the YWLC already had methanotrophic bacteria within the compost community with an initial CH4 oxidation rate of up to 95.9 μmol g(d.w.)−1 d−1. An optimum moisture content (MC) of 65 % and 50 % ww was obtained for YWLC with CH4 oxidation rates of up to 175−180 μmol g(d.w.)-1 d-1. In an assessment of long-term CH4 oxidation rates, a sample of BSC showed a long lag (60 days) to start consuming CH4; however, after this lag, it reached a CH4 oxidation rate of 160−170 μmol g(d.w.)-1 d-1, which was similar to that of the YWLC (130−140 μmol g(d.w.)-1 d-1) at the end of the 100 day experiment. While very little initial CH4 removal was detected in the BSC, different blends of BSC with YWLC were found to enhance CH4 oxidation indicating that there was a benefit to mixing the two composts. The highest long-term CH4 oxidation rates were observed in 1:1 and 1:4 (YWLC:BSC) mixing ratios (360−380 μmol g(d.w.)-1 d−1). Neither the in-situ MC, heavy metals concentrations, nutrient content, nor the in-situ population of methanotrophs were determined to be limiting variables for CH4 oxidation start-up in the BSC.

Effects of biochar content on gas diffusion coefficient of soil with different compactness and air contents.

Biochar has been found to be a potentially suitable amendment for landfill cover material and agricultural soil. The addition of biochar can improve the physical (e.g., adsorption capacity) and hydrological properties (e.g., water/gas permeability) of soil. However, no experimental study is available about the effect of biochar content (BC) on the gas diffusion coefficient (DP) of soil. The present study investigated the effect of BC on DP under different degree of compaction (DOC; 85%, 90%, and 95%) and soil air contents (SAC; 5%, 10%, and 15%). It was found that DOC and BC had negligible effects on DP when SAC was low (~ 5%). In contrast, when the SAC was relatively high (~ 15%), soil with DOC of 85% had the largest DP for BC ranging from 0 to 15% (w/w). Only when the SAC was large (~ 15%), the addition of biochar generally increased DP.

A mixture of sewage sludge and red gypsum as an alternative material for temporary landfill cover

This study proposed the recycling of sewage sludge (SS) and red gypsum (RG) as potential temporary landfill cover materials. Mixtures with different SS and RG compositions were prepared and tested in determining the most suitable design mix based on the resulting physical, mechanical, and geotechnical properties, namely the hydraulic conductivity, compressive strength, and plasticity. A maximum compressive strength of 524 kPa was achieved for the optimum SS:RG composition of 1:1, corresponding to Ca:Si composition of 2.5:1, which was appropriate to form the calcium silicate hydrate (CSH) gel. The SS and RG compositions did not affect the hydraulic conductivity, which was in the order 10−5 cm/s for all mixtures. Mixtures with RG greater than SS in composition exhibited plastic behaviour due to the Fe content in the RG, which helped minimize the risk of cracking. The optimum mixture had compressive strength greater than the specified minimum of 345 kPa, medium hydraulic conductivity, and moderate plasticity, thus appropriate for application as an alternative material for the temporary landfill cover in the tropics.

Odor removal by and microbial community in the enhanced landfill cover materials containing biochar-added sludge compost under different operating parameters

Odor problem has become a growing concern for municipal solid waste (MSW) operators and communities located close to landfill sites. In this study, nine laboratory-scale landfill reactors were used to simulate in-situ odor control by a novel landfill cover material consisting of biochar-added sludge compost under various operating parameters. Characterization of odor removal and microbial community in the cover layer under various operating parameters was conducted using gas chromatograph-mass spectrometry and 454 high-throughput pyrosequencing, respectively. Results showed that H2S (76.9–86.0%) and volatile organic sulfur compounds (VOSCs) (12.3–21.7%) were dominant according to their theoretical generated odor concentrations. The total odor REs calculated using the theoretical odor concentrations in the landfill reactors were different than using the measured odor values, which were ranked from high to low as: R6 > R5 > R7 > R4 > R8 > R9 > R3 > R2 > R1, showing the largest discrepancy of 25.3%. The optimum combination of operating parameters based on the theoretical odor concentration was different with that based on the measured odor concentrations. Moreover, although Firmicutes (12.21–91.48%), Proteobacteria (3.55–51.03%), and Actinobacteria (4.01–47.39%) were in general the three major bacterial phyla found in the landfill covers, the detailed bacterial communities in the cover materials of the simulated reactors varied with various operating parameters. Alicyclobacillus and Tuberibacillus showed positive correlations with the removal efficiencies (REs) of chlorinated compounds, H2S, aromatic compounds, volatile organic sulfur compounds (VOSCs), and organic acids. The correlations of Rhodanobacter, Gemmatimonas, Flavisolibacter and Sphingomonas were strongly positive with ammonia RE and relatively positive with REs of organic acids, VOSCs, and aromatic compounds. These findings are instrumental in understanding the relationship between the structure of microbial communities and odor removal performances, and in developing techniques for in-situ odor control at landfills.

Assessment of the geotechnical aspect of the use of paper mill sludge as landfill cover and bottom liner material

Assessment of the geotechnical aspect of the use of paper mill sludge as landfill cover and bottom liner material

Assessment of the ecotoxicity of phytotreatment substrate soil as landfill cover material for in-situ leachate management

Phytotreatment capping in closed landfills is a promising, cost-effective, in situ option for sustainable leachate treatment and might be synergistically coupled with energy crops to produce renewable energy (e.g.: biodiesel or bioethanol). This study proposes to use 0.30 m of soil as growing substrate for plants cultivated on the temporary cover of closed landfills. Once the leachate phytotreatment process is no longer required, 0.70 m of the same soil would be added to attain the final top cover configuration. This solution would entail saving the costs of excavation and backfilling. However, worsening of the initial soil quality due to potential contaminant transfer from the liquid to the solid matrix must be avoided because EU legislation (such as that in Italy) fixes concentration limits for contaminants in soil. In this research, samples of soil used as substrate in a lab-scale leachate phytotreatment test with sunflowers were analysed to provide chemical characterization before, during, and at the end of the experiment. The results showed that the phytotreatment activity did not increase initial contaminant concentrations. These results are reinforced by those from ecotoxicological bioassays in which Eisenia fetida (earthworms), Lepidium sativum (cress), Folsomia candida (collembola), and Caenorhabditis elegans and Steinernema carpocapsae (nematodes) were used. It was observed that, by the end of the experiment, the substrate soil did not affect the earthworms, collembola and nematode behaviour, or the growth of cress.