VARIAYTIONS OF LEAD CONCENTRATIONS IN SOIL PROFILES NEAR AN INTERSTATE HIGHWAY IN NEW JERSEY

Concentrations of Pb from multiple soil profiles along approximately 10-meter transects perpendicular to the interstate highway 95 at Lawrenceville, New Jersey were studied by lithium metaborate fusion and nitric acid dissolution method and digestion of the pulverized soil samples with 75% of HNO₃. Concentrations of elements in the dissolved solution were analyzed with the Spectra Arcos ICP. Our preliminary result indicated that there was a lead (Pb) concentration gradient as the distant moved away from the highway and a lead concentration depth gradient as well. In addition, the modal abundance of minerals in soil samples of multiple transects measured by quantitative X-ray powder diffraction indicated there is lack of indigenous lead minerals in the soil samples. The main minerals in the soil samples are quartz (>40% on the surface), feldspar (~5%), and smectite and kaolinite clay minerals with small percentages of hematite and goethite. Lack of lead minerals in the soil samples and the relatively high Pb concentrations near the soil surface indicate that the main source of Pb is likely the dust remnants of leaded gasoline used in the past. Concentrations of Pb in an adjacent creek near the soil transects also are found to correlate with concentrations of chloride which indicates winter deicing salt might affect the mobilization of lead transport through chloride complexation. Relatively high concentration of Pb near the soil surface adjacent to the highway indicates that Pb dust can still be a health issue for motorists in a dry season.