Lead in the soil is determined from an air-dried 3-gram sample which is shaken with 30 milliliters of 1 M nitric acid (HNO3) for 1 hour. The mixture is centrifuged and the supernatant is analyzed for lead via inductively coupled plasma optical emission spectrometer (ICP-OES). Results are reported in parts per million (ppm) lead (Pb) in the soil. This method does not measure total lead. It measures the fraction that is environmentally available, which is potentially harmful to humans when ingested.