Portable device could help New Yorkers know if garden soil is lead-contaminated

NEW YORK, N.Y. - A Cornell Tech-led research group is developing a portable, inexpensive device that uses radio frequency signals and machine learning for another important job: measuring lead contamination levels in soil.

The lab of Rajalakshmi Nandakumar developed SoilScanner, which sends radio waves of different frequencies from an RF transmitter, through a soil sample to an RF receiver, which reveals the effect the soil – and how much lead is in it – has on the signal.

The group was motivated by a map of lead contamination in New York City that Zhongqi Cheng’s Urban Soils Lab (USL) at Brooklyn College had produced over the course of several years. The testing of hundreds of soil samples revealed dangerously high levels of lead in many locations, most notably in northern Brooklyn.

“In recent years, especially during COVID, a lot of us got excited about having our own backyard garden, or spending more time at home,” said Nandakumar. “But if you look at instructions for how to grow tomatoes, no one actually tells you that you have to check your soil for lead. It’s all about pH levels. A lot of us, even though we interact very often with soils, are totally unaware of possible lead contamination.”

About 45% of the soil samples tested by USL had lead levels above 400 parts per million (ppm), the previous EPA recommended screening level (revised a year ago to 200 ppm for residential soils).

Testing for lead in soil generally involves either sending samples to a lab for analysis, which relies upon harsh chemicals and can be expensive, or using a portable X-ray fluorescence device, which is cost-prohibitive for many communities.

The group’s device is simple: Dirt is placed in a one-liter plastic container between the transmitter and receiving antenna. The transmitter sends short bursts of single-tone RF signals at low and high frequencies through the soil sample. The receiver’s power spectrum reading is passed to a machine-learning model for further analysis.

SoilScanner was able to detect lead contamination in natural field samples with 72% overall accuracy, and became even more accurate as the ppm value rose. It had a zero-error rate when lead levels were greater than 500 ppm. The team is working on an even smaller, less costly, battery-operated version of the device, using Wi-Fi and RFID chipsets such as those found in smartphones and computers.

“The goal of this project,” Nandakumar said, “is to make this technology cheaper and more accessible – both for people to test their own soils and for governments to plan for remediation.”

For additional information, read this Cornell Chronicle story.

Cornell University has dedicated television and audio studios available for media interviews.

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