SAN MARTIN
– It was talk straight from the horse’s mouth – but there still
weren’t a lot of answers.
SAN MARTIN – It was talk straight from the horse’s mouth – but there still weren’t a lot of answers.
During an irrigation seminar Wednesday in San Martin, a Texas-based scientist said to be a leading researcher on perchlorate and its effect on plants walked roughly three-dozen farmers, residents and government officials from Santa Clara and San Benito counties through his work.
The presentation by Texas Tech researcher Andrew Jackson featured a scattering of individual, tentative conclusions on perchlorate’s uptake into plants. But as in the past, answers to the broader questions asked since the perchlorate contamination was discovered in South County – “Is it safe to eat fruit with perchlorate?” and “What level harms humans?” – still seemed scarce.
“What does that mean?” asked one audience member during a discussion of studies on perchlorate concentrations in soybean leaves, which involved a different measurement technique than is usually quoted for water. “Shouldn’t that convert in a way we can understand?”
Although at least one farmer present characterized the meeting as a positive effort, it still served as a demonstration of government officials’ assertions that there’s a lack of solid knowledge about perchlorate’s effects.
The perchlorate issue is just too new, and the data too raw, to draw the kind of comfortable, solid and broad conclusions that citizens, farmers and researchers alike yearn for, Jackson said.
“The plant issue is a very, very new issue,” he said.
With charts and graphs, Jackson shared preliminary conclusions from research conducted in Texas and Nevada on natural vegetation near perchlorate-tainted streams, as well as studies on selected food crops raised hydroponically or in sand with water tainted at much higher levels – sometimes exponential – than are generally found in tests in South County.
The conclusions were fairly specific. For example, studies found perchlorate concentrations in soybean leaves, roots and seed covers but not the seeds themselves – yet the chemical still appears to affect germination.
The research suggested the leafy vegetation seems to have a large accumulation potential for perchlorate. Scientists don’t expect to find perchlorate in large concentration in fruits, but there’s little data to support that, Jackson said.
Meanwhile, Scotts Valley-based consultant Marc Buchanan noted in an earlier presentation that the way plants absorb minerals and nutrients – such as perchlorate – from the soil involves a complex maze of many different factors. Water saturation, nutrient supplies, root structures and types, light, temperature and oxygen and carbon dioxide levels can all play a role.
Research suggests perchlorate is very mobile underground and can flow fairly easily to plant roots because perchlorate ions are fairly large and both the ions and clay particles have negative charges and tend to repel each other, Buchanan said.
“It’s very mobile – it moves in water,” he said. “They flow easily to plant roots.”
Younger roots also seem to have a greater capacity and potentially more ability to draw up perchlorate than a plant at harvest, he said.
Federal officials said there aren’t set standards for the amount of perchlorate allowed in irrigation water. Jackson said it will come down to a manpower and funding issue. It takes a while to accumulate data and it’s harder to test plants than water, he said – and meanwhile, there are other contaminants that scientists know even less about.
Kip Brundage, a Gilroy hay farmer and president of the Santa Clara County Farm Bureau, said in an interview that no South County agricultural products have been halted by the contamination issue.
“Yes we’re worried, but no, we’re not panicking about it, because nobody knows what’sgood is good and bad is bad … ,” he said about perchlorate.
Brundage noted that some states have advisory levels that allow up to 18 ppb of perchlorate in water – much greater than the 4 ppb “action level” in California and the brunt of South Valley contamination levels discovered so far.
“We’re just more environmentally sensitive here I guess,” he said.
Although public perception doesn’t seem to be an issue affecting sales yet, it’s still a concern, he said.
“The pendulum always seems to swing real far one way before it comes back,” he said.
The seminar, which also featured other presentations on irrigation and techniques on managing hazardous waste, was sponsored by the Santa Clara and San Benito county water districts, those counties’ agriculture departments and the University of California Cooperative Extension.
