Συγκριτική Αξιολόγηση Μεθόδων Απορρύπανσης Της Ακόρεστης Ζώνης Εδάφους Μολυσμένου Με Κηροζίνη

Abstract

Soil contamination by industrial and urban wastes is nowadays one of the most important pollution problems worldwide. The petroleum hydrocarbons are included in the list of toxic pollutants that have contaminated extensive areas all over the world. An inevitable consequence of liquid pollutants release on the ground is their transport by a variety of mechanisms (e.g. gravity flow, dissolution, volatilization, dispersion, sorption, etc) in the unsaturated zone of soil, and subsequent pollution of the underlying aquifers. Conventional methods of ex-situ soil remediation are the soil excavation and its transportation in appropriate places (e.g. incinerator, bio-piles, etc). During the last years, there is a growing interest for the development and application of low-cost and sustainable (low environmental impact) in-situ soil remediation technologies.In the present work, two relatively new in-situ remediation technologies, bioventing and steam injection, were tested on the vadose zone of a low permeability and fractured glacial till sediment that was contaminated by jet fuel. The experimental site is situated in an abandoned military airport (Kluczewo) in North-Western Poland. The area was polluted extensively by jet fuel over a long period . The geological characterization revealed the existence of vertical desiccation fractures at the upper layers and horizontal/sub-horizontal tectonic fractures at the deeper ones, and a relatively low permeability and heterogeneous micro-porous matrix. The same geologic conditions dominate in a major part of the subsurface in Northern and Central Europe. Due to the multi-scale heterogeneities, ranging from the pore-scale to the field-scale, and the creation of preferential flow paths in such soils, it is very difficult to design successful remediation strategies based on vertical wells. For this reason, in both field experiments (bioventing and steam injection), the soil was stimulated by opening hydraulic fractures which acted as horizontal wells of fluid injection/extraction, and enhanced the influence radius of remediation. The main goal of the work is to evaluate, under field conditions, steam injection and bioventing as sustainable and efficient technologies for the removal of petroleum hydrocarbons from highly heterogeneous soils.In order to determine the efficiency of each remediation method, soil samples were collected from twelve wells and seven depths, and placed inside specific flasks pre-filled with dichloromethane (DCM). After the accelerated extraction of nonaqueous phase liquid (NAPL) from the soil and its dissolution in DCM, the composition and concentration of hydrocarbons (NAPL) was performed by using GC-MS and GC-FID. In order to clarify the main NAPL removal mechanisms and ΚΕΦΑΛΑΙΟ 2