Release of Substances from Secondary Materials in Field Conditions

Abstract

The objective of this investigation was to determine the concentrations in the seepage water from recycled building materials under field conditions and the influence of the passage through the soil on these concentrations. Using suction cups and lysimeter determinations seepage water was collected from locations with recycled materials and tested for the inorganic parameters: pH, conductivity, sulfate, copper, nickel, arsenic, chromium, and vanadium. The sulfates in the seepage water originate, in particular, from gypsum-containing components of the building materials, and to a lesser degree from brick materials. Increased pH values of up to pH 12 and increased conductivity occur to greater degrees in seepage water from concrete-containing materials due to the release of Ca(OH)2. In the building material layer the lower availability of CO2 means that the carbonatization of the leached calcium hydroxide is delayed. As the pH values increase, more copper and nickel is released due to the formation of water-soluble complexes with ammonia. At some locations the seepage water concentrations of copper, arsenic, and chromium increased likewise with increasing pH values due to the amphoteric character of these heavy metals. The formation of water-soluble compounds under reductive conditions within the water-saturated pieces of building materials means that there is an increased release of arsenic and vanadium into the seepage water. During the passage through the soil the carbonization and oxidizing conditions mean that the concentration of most parameters decreased. The most common contamination of the seepage water is through increased sulfate concentrations.