Region 1: New England
Lead-Safe Yard Program Sampling and Analysis
Analysis of residential soils for lead content is performed on-site by a chemist from the EPA Region 1 Lab along with a Certified Industrial Hygienist from the Bowdoin Street Community Health Center. Four areas of each residential yard are evaluated. Soil is tested around the house dripline, play areas for children, any areas of bare soil, and other areas that may present a potential source of lead contamination to the property residents.
Soil lead measurements are made with a Niton Model 702 XRF Spectrum Analyzer. The 702 is a field portable multi-element, multi-functional x-ray fluorescence analyzer (FPXRF) equipped with a 10mCi cadmium-109 source and a high resolution Silicon-Pin detector. The hand held, battery powered FPXRF is capable of in-situ analysis. This instrument is factory calibrated and software compensated for normal deterioration of the source. Quality control procedures used assure that the instrument is performing properly during the survey. The detection limit for this instrument is approximately 100 ppm for lead in soil.
Soil lead measurements are taken in-situ during the screening phase provided that the surface is not wet. Large nonrepresentative debris, including rocks, pebbles, leaves and roots, are removed from the soil surface prior to sampling. The area is smoothed enough to allow good contact between the FPXRF and the ground surface. Sample locations depend upon the size and shape of the region of interest. A line pattern is used when the area is linear (e.g. dripline). In-situ measurements are taken at 5 to 10 foot intervals along the line depending upon the length of the building. Target patterns are used for sampling larger, nonlinear areas of potential exposure (e.g. play areas). A large "X" is transcribed to cover rectangular spaces. In-situ measurements are taken at 5 to 10 foot intervals along each line of the "X" unless the field technician determines that additional (or less) resolution is required. Selected samples are also collected and analyzed by a second analytical method (i.e. ICP) to confirm the field XRF results.