PIXE Analysis of Soil Samples from the George Washington Bridge

Heavy metal pollution is being investigated near bridges in New York City as part of an ongoing environmental pollution project at Union College. Soils collected from around the George Washington Bridge, that crosses the Hudson River, between Washington Heights in Manhattan and northern New Jersey, were investigated for the presence of heavy metal pollution using Proton Induced X-Ray Emission Spectroscopy (PIXE). 2.2 MeV proton beams were generated in the Union College Ion-Beam Analysis Laboratory and used to bombard 21, 1-g soil pellet targets. The collected soils were sifted and pressed into targets with 10 pellets prepared from the NY side and 11 pellets prepared from the NJ side. X-ray energy spectra were generated and the results of the PIXE analysis show considerable amounts of lead present in the soil at the base of the George Washington Bridge. The lead concentration tends to decrease as distance from the bridge increases, and this trend is present on both sides of the bridge. The highest lead concentrations were determined to be directly under the span of the bridge with 1509 ± 253 ppm seen on the New York side of the bridge and 478 ± 108 ppm on the New Jersey side of the bridge.

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