M.K. Widomski1, A. Musz-Pomorska1, W. Stępniewski1, R. Horn2
1) Lublin University of Technology, Faculty of Environmental Engineering, Lublin, PL; 2) Institute for Plant Nutrition and Soil Science, CAU Kiel, Kiel, DE
MODELING OF BENZENE PROPAGATION THROUGH CRACKED COMPACTED CLAY LINER OF MUNICIPAL WASTE LANDFILL
One of the most important impacts of municipal waste landfills on the natural environment is posed by the leachate percolation through the bottom sealing liner. Landfill leachate contains numerous organic pollutants significantly affecting quality of groundwater and soil. Isolation of landfills from the environment may be performed by compacted clay liners, utilizing clay substrates of various plasticity and meeting the actual statutory requirements. But, high-plasticity clays usually present a very high expansivity, thus, they are prone to swelling, shrinkage and cracking. The cyclic drying and watering of clays causes, after several cycles, the irreversible increase in their hydraulic conductivity and decrease in the sealing capabilities of compacted clay liners, triggering the increased migration of pollutants from waste body to the natural environment. This paper presents the results of numerical simulation of benzene migration, pollutant usually observed in landfill leachate, through the bottom compacted clay liner of municipal waste landfill. Our calculations were performed in FEFLOW, DHI software for several tested clay specimens of different plasticity, compacted according to PN-B-04481:1988 and ASTM D698–12e2 and subjected to several cycles of shrinkage and swelling. The plasticity of tested clay materials was determined by standard methods and classified according to Unified Soil Classification System, ASTM D2487–11. Saturated hydraulic conductivity of compacted tested clay materials was measured by the laboratory H-4145 falling head permeameters for compacted soils by Humboldt Mfg. Co. meeting the requirements of ASTM D5856–95. Saturated hydraulic conductivity of the tested substrates after three cycles of drying and rewetting was measured by the falling and constant head laboratory permeameter by former IMUZ, Poland. Water retention curve parameters were determined in the range of 0-15 bar by sand box and pressure chambers with ceramic plates by Soil Moisture, USA. The obtained results showed influence of shrinkage and swelling of clays on leachate seepage, triggering benzene migration, through the cracked compacted bottom liner.
Keywords: pollutant migration, clay materials, compacted mineral liners, municipal landfill leachate