Abstract: Aspects of Lead in West Dallas, Texas, Soils

James L. Carter Ph.D., Norai Ibrahim

Detailed geochemical study of thirty-eight 30 cm long soil cores taken within a 1600 m radius of the RSR secondary lead smelter, West Dallas, Texas, reveals total lead values up to 35,100 ppm with the highest values occurring within 650 m of the smelter. The soil lead is 90 percent or more readily mobile in cold 2N nitric acid, and shows an exponential-like decrease with distance from the smelter. Lead isopleth maps show that wind played an important role in dispersing the lead in a NNE direction from the smelter to a distance exceeding 1600 m. Migration of lead down the soil profile generally shows a rapid decrease with depth. However, some cores have complex multiple lead-rich layers suggesting bioturbation and desiccation "cracking" of the soil to be important physical processes for vertical redistribution of the lead. Some soil cores from previously remediated areas reveal surface recontamination with lead as high as 1300 ppm. One core has 12 cm of lead-free soil on top of a normal soil profile with lead values as high as 18,000 ppm in the organic-rich surface layer of the buried soil. The data also reveal that as much as one-half of the soil cores with lead levels higher than 500 ppm, at the cm-scale, will be miscategorized as non-toxic by using the average soil sampling method.

AAPG Search and Discovery Article #90960©1995 AAPG Southwest Section Meeting, Dallas, Texas