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Digging in the dirt with Yakov Pachepsky

Soil scientist Yakov Pachepsky researches the transport and flow of elements and particulates in landscapes across the world. (photo: Carrie Madren)

"What do you see?" quizzes Yakov Pachepsky, as we walk along a dirt path through spring corn fields. I venture an answer involving the slight slope of the land, where rainwater must flow during downpours — a good observation, replies Pachepsky, a soil scientist who has been researching the transport and flow of elements and particulates in landscapes across the world.

People think of soil as a sieve, but it's not: water travels through natural conduits to waterways, explains Pachepsky. For nearly 20 years, Pachepsky, 62, has conducted research at the Environmental Microbial and Food Safety Laboratory at the Beltsville Agricultural Research Center, one of the Agricultural Research Service centers under the USDA. His research helps engineers and others to develop better practices that keep pathogens out of our water and off food crops, keeping us safe from unnecessary illnesses.

Much of his time is spent creating models or interpreting data, looking for patterns or making it useful for environmental and other professionals to better understand how pollutants move through landscapes. In his quiet, wood-paneled office, in a building set on the pastoral, rolling hills of Beltsville, is an impressive wall of awards, including the 2007 Don and Betty Kirkham Soil Physics Award — the most prestigious soil physics award in the world.

He briskly maneuvers a maze of stairs and hallways to reach his two labs — each filled with measuring instruments and powerful blenders that churn soil samples.

During field experiments, of which he conducts about 10 each year, Pachepsky — who has dark hair and a salt-and-pepper beard — likes to crack the occasional joke while chatting with colleagues. He supplies them with doughnuts and blows a trainer's whistle to communicate with his team during rainfall simulations.

One of Pachepsky's experiments looks at how microbes settle in underwater sediments — in reservoirs, pipes, creeks, and ponds — and how these pathogens can affect our water if disturbed. "They can sit for hundreds of years," he says, without disturbance. Pathogens from crop irrigation or applications can survive in leafy greens and make us ill — a series of events made famous in the 2006 outbreak of E.coli in spinach.

In another experiment, he looks at how a creek's sediment is disturbed after an influx of water from an irrigation truck. Every few weeks, Pachepsky drives up to Cove Mountain, Pennsylvania, to gather data from a larger-scale watershed, about 18 miles by four miles, to study how farm management affects water quality over a larger area.

He likes the scenic drive to Cove Mountain because "it's important for scientists to stay physically close to their subject matter," and "you need to see the soil yourself," he says.

Investigating landscapes wasn't always his career goal. Born in the Ukraine and raised in Crimea, Pachepsky was finishing up his Ph.D. in applied mathematics and physics in Moscow when he needed a job close to the city. A friend tipped him off to a new soil institute within the USSR Academy of Sciences that would hire mathematicians, even those — like Pachepsky — who didn't know soil. Pachepsky learned on the job by working for world renowned soil scientist Victor Kovda, and eventually earned his doctoral degree in soil science.

His first research focused on the salinity in soils in the arid and semi-arid deserts of the former Soviet Union. "If you don't use water wisely, it will cause salinization," he explains. Salinization occurs when salts rise to the surface, killing plants and ruining drinking water. "There are ways to fight it, but fighting it typically involves using even more water."

From 1978 to '80, Pachepsky and a team of scientists created an enormous model that halted construction of a multi-million-dollar project that would have carried water 1,600 miles from Siberia to Central Asia; their model showed that salinity levels in the planned trench would be unpredictable. No paper came out of the three-year research, but their efforts saved many lives, he says.

Pachepsky came to the U.S. in 1992, part of a mass migration of scientists who felt that "the Soviet Union didn't support science," says Pachepssky.

"He's one of the few people who's reached the pinnacle of his career in one country — the former Soviet Union — and now has reached the pinnacle here," says microbiologist Dan Shelton, lab chief at the Environmental Microbial and Food Safety Lab and Pachepsky's boss.

The best part of his work, Pachepsky says, is seeing patterns emerge from numbers (for instance, in how water and soil exchange pollutants), and using those to make predictions, such as how pathogens will move after a big rainstorm, and what that movement depends on. Building models helps to package gained knowledge, he says, \so that people who don't have the expert knowledge — engineers, environmental assessment people — can use it."