Construction of lysimeters for researching the leaching of potentially toxic elements from building materials

Abstract

By using recycled waste in construction, natural materials are being replaced, thus establishing a circular economy at the local level. An important aspect is also the conservation of natural resources. This is especially important in case of earthworks (embankments, backfills), which are large consumers of materials. Compared to natural aggregates and earth, geotechnical composites based on recycled materials can contain a higher total content of potentially toxic elements (heavy metals, chloride, sulphate, fluoride, organic pollutants etc.). The prerequisite for beneficial use of such composites is that the potentially toxic elements are immobilized in the composites, meaning that they are chemically inert. Potential environmental impacts, especially those associated with transfer of potentially toxic elements from new geotechnical composites into soil (aquifer respectively), are usually evaluated on laboratory scale, while their behaviour in real environment is usually poorly investigated. For this reason, there is a demand for the development of sensitive, reliable, and cost and time efficient monitoring tools for determining mass flows of potentially toxic elements from building materials, for example geotechnical composites, which are under the influence of various environmental factors. This paper presents the construction of field laboratory, based on a system of pan lysimeters. The lysimeters are used to collect leachate from geotechnical composites based on recycled materials. They are constructed in a way to be relatively low cost and at the same time large enough to representatively reflect the processes in geotechnical fills. Obtained data on the amount and quality of leachate can be used as a basis for the study of immobilization processes and for water balance. Moreover, this data will be used as input in the geochemical numerical model for the simulation of transport of potentially toxic elements released from geotechnical fills in different types of aquifers (alluvial aquifer with intergranular porosity, aquifer in consolidated rocks with fissure porosity).

Environmental Acceptability of Geotechnical Composites from Recycled Materials: Comparative Study of Laboratory and Field Investigations

“…After compaction, each compacted layer was around 10-cm-thick. Each lysimeter was covered with a 15-cm-thick layer of quartz aggregate 4/16, placed on top to prevent surface runoff and evaporation of the precipitation [25]. Uncompacted composites represent an installation that is extremely non-compliant with construction requirements and daily practice.…”