PIXE analysis of Heavy Metal in Soil Along the East River

We performed a Proton-Induced X-ray Emission (PIXE) analysis of  soil samples collected at urban parks on either side of the East River between Manhattan and Queens, NY, to search for heavy-metal pollution. Soil samples were collected in Astoria Park in Queens in 2019 and in Randall's Island Park in Manhattan in 2021. The samples were bombarded with proton beams from the 1.1-MV tandem Pelletron accelerator in the Union College Ion-Beam Analysis Laboratory and the emitted X-rays were measured using a silicon drift detector with an energy resolution of about 130 eV. All of the soil samples contained measurable concentrations of the metals Ti, Cr, Mn, Fe, Cu, Zn, and all but one contained a measurable level of Pb. Many of the samples contained lead concentrations above the EPA standard for play areas. Clear enhancements were observed in the levels of lead and zinc around the Hell Gate Bridge indicating that this railroad crossing that passes through the two parks and over the East River is the source of the heavy-metal pollution. Strong lead and zinc peaks observed in PIXE spectra taken on paint chips collected under the bridge suggest that the contamination may be from lead-based paint used on the bridge when it was constructed over a hundred years ago.