Environmental Ramifications of an 120 Year Old Railroad Bridge Painted with Lead Paint.

Lead (Pb) is a prevalent soil contaminant and can be toxic to animal and plant life. The objectives of this study were to 1) determine if wind influences the transportation of Pb from a point source, 2) determine the ability of Pb to leach through a soil profile, 3) and to determine the ability of plants adjacent to a point source to take up Pb. The site studied was underneath an 120 year old railroad bridge painted with leaded paint, located on the Cal Poly San Luis Obispo, CA campus. Soil and plant samples were collected in the vicinity of the bridge. The soil and plant samples were extracted using US EPA Methods 3050 B and 1311. U.S. EPA Method 3050 B (Nitric acid digestion) was used to find the total Pb in the soil samples, while 1311 (TCLP, Acetic acid digestion) was used to find bio-available Pb. Wind had a large influence on the concentration of Pb in the vicinity of the bridge. The soil downwind of the bridge (215.65 mg Pb/kg) had significantly more lead than the soil upwind of the bridge (57.69 mg Pb/kg). Lead was found to be highly reactive with the soil and; therefore, unable to leach readily through the soil profile, as it remained in the upper soil horizons. Plants underneath the bridge and immediately adjacent to the bridge were found to contain the highest concentrations of Pb (19.42 - 22.4 mg Pb/kg) relative to upwind locations (10.46 mg Pb/kg - 16.18 mg Pb/kg). The soil Pb results from these methods when compared against the Pb extracted from the plant samples showed no correlation. This indicated the quantity of Pb in plants did not correspond to increases in bio-available Pb or total Pb in the soil. This study demonstrated that structures painted with leaded paint have the potential to introduce large quantities of Pb to nearby soils. The distribution of soil Pb is influenced by wind, with soil Pb levels being elevated downwind of the point source relative to upwind locations.