LEAD CONTAMINATION IN SOIL AROUND HISTORIC HOUSING: ESTABLISHING RAPID FIELD MEASUREMENT METHODS WITH X-RAY FLUORESCENCE (XRF) TO INFER LIKELY CONTAMINATION SOURCES

Testing lead levels in soil is time consuming, but extremely important for characterizing the severity of the risk and the extent of the pollution when the presence of such contaminants is known. New sampling methods and sensing devices have improved the reliability of more efficient techniques, such as X-Ray Fluorescence (XRF) hand-held devices. Previous work validated the efficacy of measuring soil lead levels using the XRF device compared with Inductively Coupled Plasma Spectrophotometer (ICP) in a series of experiments at West Point, New York, which is known to have lead pollution in the soil around homes and buildings. In our previous work, geospatial analysis of 300 sample sites within 4 square miles resulted in a “heat map” characterizing areas of most concern throughout all housing areas. Those results were useful for initial conclusions, but several areas of immediate concern had lead concentrations above Environmental Protection Agency (EPA) standards of 400 ppm, warranting further investigation.

Using the hand-held XRF instead of the ICP is attractive for both accuracy and efficiency, but in previous work the soil samples were dried, sieved, and prepared for ICP analysis before the XRF measurement was taken. The time savings was significant; after drying overnight (24 hours), the ICP measurements took 6 hours per 20 samples while the XRF took just 10 minutes per sample. The time savings could be even greater if the XRF could be used in the field and soil samples not taken back to the lab for drying and sieving. This study aims to compare field expedient XRF sampling to measuring the dried and sieved samples with the same XRF device in the lab. To make further conclusions about the sources of the contamination (hypothesized to be from leaded gasoline exhaust in pre-1980s vehicle traffic), we focused on one particular location with lead soil contamination already measuring above the EPA standard. At this location, we established a spatial grid, taking samples at 2 meters apart covering all the soil around the home, which was built in the year 1857. By analyzing over 200 samples and mapping them spatially, we also can visualize the severity and extent of the pollution to further conclude the potential sources of the lead contamination (building materials and paint, or particulate deposition from fuel combustion in vehicles).