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Are City Fruit Trees Safe?
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K. Ruby Blume
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Last Updated on April, 15 2009 at 09:00 AM
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The Urban Homesteader heads to the library to learn if Oakland's urban orchards suffer from an abundance of toxic chemicals in the soil and the groundwater.
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An Apple Tree Blossoming in an Urban Garden by K. Ruby Blume/Inst. of Urban Homesteading
Dear Sparky Beegirl, What is the situation with Oakland groundwater contamination and various types of fruit or nut trees? My understanding is that there can be specific contamination “plumes” from say, leaking gas station storage, old trolley sits, etc. But there is also more widespread contamination from a hundred plus years of lawn care chemicals, factory dumps, runoff, construction contaminants, which flow in a south-westerly downhill direction toward the bay from the hills. (at least in North Oakland.) I would think that fruit tree roots would go down deep enough to suck up contaminated water? -- Len Rafael
Dear Len:
I did several hours of research to try to answer your question and it was amazing how difficult it was to get definitive answers about the groundwater in the Bay Area. Apparently, there is no comprehensive groundwater monitoring program in California. This, from the Natural Resources Defense Council: “The status of California's groundwater resources is monitored by an array of different agencies (both state and federal) with little, if any, coordination among them.”
The format in which the information about groundwater quality is presented can be deceptive in that agencies assess the quality of the water relative to certain standards (which may or may not be appropriate), rather than relative to its natural state or to previous measurements, thus obscuring the degree to which the water's composition has been altered and providing no data trends.
You are completely right about contamination plumes and build-up of various toxins in the groundwater. In an urban environment, these can be heavy metals leached from city dumps, waste from septic tanks and sewage treatment centers, gasoline and other wastes leaked from underground storage tanks.
I looked for information on specific hotspots in Oakland, but found nothing. In terms of your specific neighborhood, I would talk to older locals to find out the history of your neighborhood.
The good news is that the interaction between your fruit trees and the groundwater is minimal, probably non-existent. Groundwater typically percolates through the strata 30 to 100 feet deep. Fruit and nut trees, while they may have anchoring roots that go 10 to 15 feet into the soil get most of their water and nutrients from lateral roots in the upper 2 to 4 feet of the soil.
So, in terms of worrying about toxins and your urban orchard the issues are going to have to do with surface water, heavy metal build up in the top soil and air pollution.
Since surface water doesn’t travel that far you should mostly be concerned if you are directly downhill from a park or golf course where they use heavy pesticides, herbicides or fertilizers. And unless your home was built right on top of an industrial site (unlikely for any houses built before 1950, and for older houses city records will give you the answer), the most likely contaminant with be lead in the soil from years of lead paint flaking from the buildings. You can find out more about lead and lead testing here.
The best remedy for lead in the soil (as well as any other toxic build up from pesticides and lawn care products) is heavily amending with compost and mulch or, in extreme cases, building raised beds.
Toxins from air pollution are unavoidable, but since we are breathing the air every day, eating fruits or vegetables exposed to the same amount as we are on a daily basis is going to be no worse. There are no studies that show a significant build up in fruit from air pollution.
There are toxins in our food. Studies have shown that even 25% of organic produce tests positive for residual pesticides, including DDT which has been banned since the 1970s.
My personal opinion is that we are much better off eating food from our own organic urban farm than eating conventional food from the agricultural belt. The real contamination of food and groundwater stems from the agricultural industry itself. Widespread use of pesticides, herbicides and chemical fertilizers have lead to contamination of both groundwater and topsoil. The amount and toxicity of what people use on their lawns in the city is negligible in comparison.
If you have questions for Sparky Beegirl, write to editors@theoakbook.com |
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OAKLAND
THE GOOD LIFE
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