SOURCES OF TRACE ELEMENTS IN TIRE MONOFILL LEACHATE AS DETERMINED BY ACCELERATED AGING OF ROCK DEBRIS

Tire monofill uses daily and weekly coverage to keep tire shreds from receiving excessive sun shine heating and atmospheric oxidation. Rock debris at site from previous coal mining activities is the convenient source. Different rock debris was crushed to pass 30# and then transferred into a cotton-mesh thimble and then placed into a Soxhlet extractor. The flask of the extractor was filled with 100 ml of simulated rain containing Cl^- and SO₄^2- . The extraction was performed at 105^o. The extracted solution was evaporated down to incipient dryness for ICP-MS analyses to determine trace element concentrations. The rock debris samples were analyzed before and after the extraction.

Elemental concentration in leachate samples were also evaporated down to incipient dryness. The precipitates were sent for the same kind of analyses. So trace element levels in simulated leachate and collected leachate from the monofill can be compared. In addition, trace elements from the liner of the monofill, tire shreds, and precipitation collected as snow were also determined for comparison.

The analytical and experimental studies indicate that the covering materials are the main source of trace elements in the monofill leachate. Pyrite and marcasite in rock debris, particularly black shale and weathered coal, appear to be the principal mineral source as evidenced by ESEM and sulfur analysis.