Papers by Keyword: Soil

Abstract: The carbon cycle is quantitatively altered by the anthropogenic activities, especially by the carbon dioxide emissions. The soil has a fundamental role in this circuit, due the fact that, on the one side, it deposits the organic and non-organic carbon and on the other side, it holds the vegetation, which, through photosynthesis process, extracts carbon dioxide from the atmosphere and transforms it in organic matter. Therefore, the role of the soil in terrestrial sequestration is acknowledged. In this paper it is analyzed the terrestrial carbon sequestration potential in Mehedinţi County (Romania).

Abstract: The distribution of residual pesticides in soil and rice grain was studied in rice farming area covered in Samchuk district, Suphanburi province, Thailand. The 19 samples of soil and rice grain were collected by random sampling in 2015 covered 7 sub-districts. The residual carbofuran and glyphosate in soil and rice grain was quantitative determined based on standard method. It was found that the concentration of carbofuran was found in the range of ND-0.0512 µg/kg and ND-0.0865 µg/kg for soil and rice grain, respectively. Glyphosate was found in the range of ND-0.2632 µg/kg and ND-0.2244 µg/kg for soil and rice grain, respectively. The residual levels of carbofuran and glyphosate in soil and rice grain depended on a spray period time, their decomposition and their concentration usage. The residual levels of carbofuran and glyphosate did not significantly quantitative correlation between soil and rice grain for this study area.

Abstract: Landfills are one of the groundwater pollution sources in Rwanda. Physical and chemical analyses of water samples were carried out to assure the magnitude of Nduba Landfill on ground water quality. Laboratory tests were conducted to get the results which helped us to study the assessment of leachate effect and to propose mitigation measures of Nduba landfill. The results showed that most of water were contaminated, where concentration of most physical and chemical parameters were above acceptable standard levels required by local and international standards for potable. The analytical results of leachates samples (Cu: 38.5 mg/L, Mn: 13.075mg/l, Zn:15mg/l, TP:4525mg/l, pH:8.52µS/cm, COD:7100mg/l, BOD:182.1mg/l, TN:5mg/l and Fe: 43.025 mg/L) showed that heavy metals are leached out from the MSW. The analytical results of groundwater from the wells located in the vicinity of Nduba landfill site (Cu: 2 mg/L, Zn:3.5-5.5mg/l, SO₄^2-: 250-275mg/l, NO₃^-: 55-67.5mg/l,NH₄⁺:1.5-2.25mg/l, COD: 39-53.4mg/l, Fe: 1.75-4.25 mg/L, Turbidity: 4.03-4.32NTU, pH:5.31-5.73µS/cm, Temperature: 21°C and BOD:20.7-21.6mg/l) compared to the World Health Organization standard (Cu:0.1mg/L,Fe:0.3mg/L,Zn:5mg/l,SO₄^2-:200mg/l,NO₃^-:50mg/l,NH₄⁺:1.5mg/l,Turbidity:<5.0 NTU and pH:6.5-9.2µS/cm) revealed that groundwater from the wells located in the vicinity of Nduba landfill site requires further physical chemical treatment to ensure their suitability for human consumption as the levels of some water quality parameters exceeded the EPA guidelines for drinking water. Designing a sanitary landfill was recommended to avoid effects of leachate on environment.

Abstract: Giving the current trend of recycling and reutilization residues, sludge reuse has become an environmental, social and economic necessity. A possible destination would be the utilization of sludge as part of cover layer in solid waste landfills. This paper aimed at investigating the geotechnical implications of the addition of domestic sanitized sewage sludge on clayey-silty sand. The sludge was sanitized with hydrated lime, in the proportion of 25% lime and 75% sludge, and held for 90 days in an agricultural greenhouse for its total stabilization. Then, geotechnical tests were conducted using pure soil, pure sanitized sewage sludge and mixtures of these two materials. Three mixtures were tested: 50% soil and 50% sludge, 66% soil and 33% sludge and 90% soil and 10% sludge. The results showed that the sanitized sludge is a coarse-grained material and, its Atterberg’s limits showed the lack of plasticity. Generally, the greater the sludge percentage in the mixture, the bigger the decrease on the shear strength parameters, it also leaves them lighter and more permeable. At the end, the conclusions were that the 10% sludge and 90% soil mixture has shown geotechnical characteristics that allow its utilization as daily and intermediate cover layers. The sludge and the 50% sludge mixture have shown geotechnical properties adequate for their utilization as component in draining sub-layer in final cover layer.

Abstract: The use of chemical pretreatment with 10mM EDTA to enhance the arsenic microbial mobilization was evaluated in this study. The bioleaching involved the use of the indigenous sedimentary and soil heterotrophic microorganisms, whose leaching media contained 2mM EDTA. The main objectives of using the chemical pretreatment was the removal of metal surface coatings from the iron minerals, such as Cu and Zn, which inhibited the iron microbial dissolution in the soil and sediment environment and thus increasing the mobilization of the retained As. To examine the effect of the chemical pretreatment and the biological leaching on the mobilization of Cu, Zn, and As, batch and column tests were conducted within the laboratory experiments. The removal of As and Zn from the soil and sediment was greatly enhanced by the co-treatment in the batch solution conditions than in the column percolate conditions and had negative effect only for Cu. In the batch tests, the heterotrophic bioleaching of the soil and sediment was found to have a pronounced positive effect on the extraction of As and Zn.

Abstract: Washing tests using a typical chelating agent (Na₂EDTA) and two reducing organic acids (oxalic and ascorbic acid) were conducted to remediate soil contaminated by heavy metals at a former metal smelter. Removal efficiencies of arsenic, cadmium, copper and lead under Na₂EDTA washing enhanced by reducing organic acid were tested with washing time and steps. Results showed that the addition of reducing acid increased the overall removal efficiencies of metals in some extent. The combination of Na₂EDTA and oxalic acid was effective in removing arsenic and copper, while the combination of Na₂EDTA and ascorbic acid was more effective in removing cadmium and lead. Washing process included the rapid desorption (20~60 min) and the rate-limited dissolution. Most available contents of metals were extracted within an hour. Multi-step washing was more effective than single washing. However, secondary washing was sufficient for remediation. So the washing conditions should be identified prudently.

Abstract: The article deals with the measuring results of the specific conductance of multicomponent systems which consist of more than three materials of various characteristics. As it was shown the electrical conductivity of systems composed of soil, slag and water depends in a lesser degree on the amount of slag and in a greater degree on slag’s chemical composition. The value of specific conductance decreases when the amount of slag increases for basic slag, and increases for acid slag. For a system, which includes gravel particles coated with organic substances, the value of specific conductance correlates with the electric properties of the materials used, namely the function of chemical composition of the musticomponent system. Thus, there is a possibility to design a mathematical model for forecasting electric properties of multicomponent systems, which is based on an objective characteristic, namely, chemical structure of the materials used.

Abstract: The paper presents a reasonably advanced constitutive law for soil – a hybrid of the Modified Cam Clay and a new RU development. The Modified Cam Clay model is an isotropic hardening elasto – plastic model originated by Burland in 1967 [1] within the critical state soil mechanics. This model describes realistically mechanical soil behaviour in normal consolidation states. The other one is designed to ensure more adequate soil responses to reloading paths, particularly in the range of small strains. The RU+MCC model has been implemented in the FEM computer code Z_SOIL.pc. To test the influence of the small strain nonlinearity on soil – structure interaction as well as to exhibit the ability of the proposed model to simulate realistically this effect, a comparative study based on the FEM solution has been carried out. As a benchmark a trial loading test of strip footing was used.

Abstract: There was performed test of ecotoxicity with using earthworm Eisenia Fetida as chief representative of terrestrial organisms in the study. Soil matrix LUFA 2.3 was selected as a model of natural soil environment. Tested FEAs were follows: Sthamex F-15, Moussol-APS F-15 and Finiflam F-15. For experimental purposes, laboratory installation for infiltration was designed and compiled. Infiltration of three FEAs solutions was done before the ecotoxicity testing. Contaminated soil after infiltration was tested for semi-chronic ecotoxicity and reproduction ecotoxicity then. Introductory results indicates differences between each FEA, caused by various composition. Sthamex F-15 was determined as the most ecotoxic agent at all. Whilst Moussol-APS F-15 was evaluated as the agent with least ecotoxicity effect.

Abstract: The testing results obtained during investigation of 3D mat are presented in the article. The spatial mat is designed to provide a cheap, efficient and durable soil stabilization on slopes. The testing was focused on development of suitable methods to be used when assessing foil properties on-site. The tested samples were extracted from mats that were used for soil stabilization at the location of mine Nástup Tušimice (Company Severočeské doly, Czech Republic) and exposed to external environment and weathering for 2 years. The performance of the mats was compared with reference samples from unused mats stored for 2 years in laboratory conditions. The testing revealed that deterioration of the material is negligible over the period of 2 years.