Relationships between different scales of testing (lab, lysimeter, field)

The graph illustrates the release behaviour of Pb from mixed waste as tested by the pH dependence leaching tests, the percolation test (lab), lysimeter studies and field leachate measurements. The data transformed to the same format show the solubility controlled leaching behaviour of Pb (found to be controlled by largely by PbMoO4 and sorption onto Fe-oxide surfaces) in this complex waste mixture. The single data points in the left hand graph illustrate the leaching of individual waste streams and of the basic predominantly inorganic waste mix with an addition of 10 % by weight of individual waste streams. For comparison, the regulatory criteria (ANNEX II of the EU Landfill Directive) are given. The box given the relevant pH domain for judgment of the waste mix, the regulatory limit (upper horizontal line) and the detection limit van Pb in eluate analysis (lower horizontal line). In the right hand graph, the same criterion is inserted. As a liquid to solid ratio (L/S) relates to a time scale (by infiltration, height, density) the release con be judged. For a landfill scenario, L/S=1 may correspond to approximately 100 years of exposure. This implies Pb will not be critical against the EU-LFD criteria.