This is the fourth six-month progress report on a reconnaissance geochemical survey of the State of Missouri. The survey was initiated in July, 1969, to provide epidemiologists of the Environmental Health Center of the University of Missouri with data on the variability in the geochemical environment throughout the State. It is a pilot program in that it is the first attempt to provide information of this kind for so large an area (69,420 sq. mi.), and it is expected that the approaches being developed will be applicable to other reconnaissance investigations designed for similar purposes. The general approach--common to all four phases of the program (rocks, soils, vegetation, and water)--now appears to have taken a final form. The approach to sampling has been described in a following section of the present report. The principal task remaining in the reconnaissance geochemical survey is to follow the general approach through to completion. Some special investigations of selected small areas have been completed (Connor, Shacklette, and Erdman, 1971; Connor, Erdman, Sims, and Ebens, 1971), others are underway, and still others may be started--depending on local situations, or problems, that are identified by us or brought to our attention by others. One important purpose of the reconnaissance survey is to provide background data on the general geochemical setting which may allow more meaningful assessments of local geochemical conditions.
