Non-Controlled Emission of Light Hydrocarbons (C2-C6) to the Atmosphere From Arico's Landfill, Tenerife, Canary Islands, Spain

Light hydrocarbons play a significant role in the atmospheric chemistry because some of them act as precursors of photochemical smog production. Landfill gas is constituted by a large number of hydrocarbons and their oxidation products, as well as others organic compounds. In order to control the migration and emission of landfill gas through the landfill surface and adjacent rock, gas control systems are in use. However, significant amount of non-controlled emission of major and trace landfill gas components could be emitted to the atmosphere in a diffuse form. In this study, we estimate the "non-controlled" emission rate of light hydrocarbons (L.H.) from Arico's landfill situated in the island of Tenerife. Arico's landfill has an extension of 0.35 Km², and 1,170 tons of urban solid waste, which contains an average of 48% of organic matter, is daily deposited. A surface gas efflux survey is being carried out in the Arico's landfill. Diffuse CO₂ efflux measurements are being performed by means of a portable NDIR sensor according with the accumulation chamber method. CO₂ efflux reach values of 1,014 gm^-2d^-1. At each sampling site, landfill gas samples are also collected at 40 cm depth using a metallic probe and analyzed within 24 hours for CO₂, C₂H₆, C₃H₈, C₄H₁₀, C₅H₁₂ and C₆H₁₄ concentrations by means of a VARIAN microGC QUAD. The highest observed C₂H₆, C₃H₈, C₄H₁₀, C₅H₁₂ and C₆H₁₄ concentrations to date were 946.4, 285.1, 29.9, 32.5 and 14.2 ppmv, respectively. On the contrary, CO₂ content reach levels up to 36%. Light hydrocarbons fluxes were estimated by multiplying CO₂ efflux times (L.H.)i/CO₂ ratios at each sampling site, respectively. Observed maximum L.H. degassing rates are 2,523, 760, 1713, 259 and 241 mgm^-2d^-1, respectively. Spatial distribution analysis of this date suggest clearly a non-uniform pattern of degassing at landfills. These findings suggest important environmental and engineering implications related with "controlled" and "non-controlled" emission of landfill gases.