GEOCHEMISTRY OF CONTAMINATED SEDIMENTS IN THE TRI-STATE MINING DISTRICT: PROCEDURES REVISITED

Abandoned mine tailings have progressively contaminated areas surrounding former mining and smelting centers, a problem affecting many such regions worldwide, including the Tri-State Mining District of Missouri, Kansas and Oklahoma (TSMD). Studies have focused in characterizing this type of contamination and in the geochemical processes taking place. However, studies differ widely in their approach and procedures are far from being standardized, even within the TSMD. Parameters commonly varying among studies include: a) sample medium; either soil or sediment, b) depth at which the sediment sample will be collected as well as its location within the stream channel, and c) size fraction of the sample. Further variations in the reach of the data are mobility and/or bioavailability of the metal through sequential extraction which can be of one to five steps, toxicity to a particular organism (fish, bird, crayfish, etc.), and response of contaminants to a specific method of remediation, e.g., bioaccumulation in plant tissue. Limestone exposed at TSMD is expected to immobilize most metals. However, toxic levels of lead in groundwater and of cadmium in streams have been observed in areas within the TSMD. These occurrences stress the need for revisiting the paths in which metals move through this particular environment. Commonly reported variables that may lead to a more meaningful and cost-effective study will be discussed.