U.S. Water News Online
HANOVER, N.H. -- Development of former farmland can disturb
pesticides spread nearly a century ago and contaminate nearby water
sources, according to a study by researchers at Dartmouth College.
The findings mean communities may need to take additional
precautions when the soil at former orchards and farms is disturbed
for development or new agricultural uses, Carl Renshaw, a professor
of earth sciences, said in a news release.
The problem is that pesticides spread during the early 1900s
contained both arsenic and lead, which researchers have found remain
in the top 10 inches of soil. The study results appear in the
January-February issue of the Journal of Environmental Quality.
But the study, which focused on two New Hampshire apple orchards
where the pesticide lead arsenate once was used, found that over time
these toxic metal change form and become part of the silt and organic
matter in the soil.
In that new form, the metals become more susceptible to erosion,
which can be accelerated by development.
"We continue to learn more about how past agricultural practices
are affecting our current environment," Renshaw said. "Unlike some
pesticides used today, metals like arsenic and lead in old pesticides
do not degrade over time."
The study found that when disturbed, these metals can make their
way into nearby surface water. It was unclear whether plants and
animals that feed off that water are absorbing the metals, Renshaw
"While the arsenic and lead in the soils of old orchards is
essentially immobile as long as the land is not disturbed, our work
suggests that the development of these lands can inadvertently
mobilize these metals toward bodies of water," he said.
"Communities in these areas may want to ensure additional
precautions are taken to control erosion when old orchard lands are
disturbed in order to reduce the potential for contamination of
nearby surface water," Renshaw said.
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