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Posts Tagged ‘raised beds’

From Brent:

I would like to share some advice to all city gardeners:  Please get your soil analyzed for heavy metal contamination!

I would not recommend eating anything that has been planted into the topsoil in Halifax without having a heavy metals scan done. On the up side, container gardens or raised beds with that have imported clean topsoil and that are isolated from the ground are most likely not contaminated, but testing couldn’t hurt.

I recently moved back into Halifax and found that my back yard was quite sunny and sheltered a great spot for gardening, but a soil test revealed lead contamination at 971 ppm, way over the limit for even an industrial site and totally out of the question for food production, so now my garden is planted directly into bags of topsoil ammended with compost tea and isolated from the ground by boards. Better safe than poisoned!

I used ALS labratories in dartmouth tho do a Metals Scan it cost about $60 and i had the results in a week. They give a very detailed report but the first page is really all that’s necessary, the results from the mass spectrometer.

ALS Laboratories Group
Environmental Division

Halifax
, NS Ph: 1 902 – 481 – 0017

I compared my test results with the table below: (mg/kg = ppm)

Canadian Environmental Quality Guidelines
http://www.ccme.ca/assets/pdf/rev_soil_summary_tbl_7.0_e.pdf

and here’s some good guidelines for taking soil samples:

http://www.gov.ns.ca/agri/qe/labserv/soilsamp.shtml

Second post from Brent:

I would wager that the lead found in my soil is most likely from lead in paint, my area of town is very old, many of the houses standing were built in the early 1900’s, lead wasn’t banned in paint until 1978. Spills of leaded fuel is another likely candidate. i would suggest that all of the halifax peninsula and old parts of dartmouth are all suspect for these reasons. my tests also revealed other contaminates that are at a level for concern including arsenic, and some that could inhibit plant growth like copper.

As far as cleanup goes my research suggests that by far the best way and quickest is to remove the contaminated soil down to a level where roots could penetrate, 3 feet is a good place to start, test the soil at that level and remove more as necessary to get acceptable results, then replace with clean fill.

I have done some reading on bio-remediation it seems like for long term binding of toxins to prevent leaching, where the land would not be used for agriculture this method shows promise. heavy metals won’t disappear, they still remain there unless of course the plants are dug up removed and disposed of in an appropriate manner.

Raised beds, isolated from the existing topsoil with at least a couple layers of material that roots can not penetrate and that worms can not burrow through, or raise the beds off the ground completely would be my suggestion for a permanent solution.

Keeping a high pH can also help to keep heavy metals ‘bound’ so that they are not available for plants to absorb, of course not all plants will thrive in a high pH environment.

I have also read documents that suggest that fruit crops are the safest food that can be eaten off contaminated soils, assuming that the fruit does not touch the soil it it the least likely part of the plant to contain contaminates. for root crops, some suggest that heavy scrubbing and then deep peeling can eliminate the chance of ingestion and for leaf crops only leaves that have not touched the soil and that have been thoroughly washed may be okay for consumption.
there is research that suggests that many plants do not absorb or absorb very little heavy metals and that the main method of poisoning is by ingesting the soil itself. i know i’ve eaten plenty of soil in my time, and that washing food is no guarantee that there are no soil particles on your food.

One last note, in my yard (and probably many others) it would be advisable to not touch the soil at all with bare hands, and to avoid tracking the soil into the house via shoes, tools or even pets, where the soil can dry and become toxic dust!

One way to possibly decrease the cost of testing is to send in multiple samples at the same time, the lab may be able to give a ‘bulk’ discount.  i went through a number of tests and quotes before going ahead and they were flexible on the pricing when it started getting expensive.  maybe if a non-profit group approached them with multiple samples they might be even more flexible?  it wouldn’t hurt to ask, i dealt with  Holly Delaney at ALS  exclusively through emails, she was very helpful.

  • Holly Delaney
  • Account Manager
  • ALS Laboratories Group
  • Environmental Division
  • Halifax , NS
  • Ph:  1 902 – 481 – 0017
  • Fax: 1 902 – 481 – 0455
  • holly.delaneyalsenviro.com

Comments

Sunflowers are good for cleaning the soil.

Mushroom Culture has also proved to be amazing at cleaning soil out. Check out Paul Stamets, and Fungi Perfecti.
I wonder if there is a soils map for the peninsula. With that we might get a general idea of the areas that are know for certain toxins. If there isn’t a map now, it would be good to make one from the data people are getting on their own plots.
From Wayne Grozko:
I would caution against taking this story about heavy metals in soil to
newspapers right now, because I think we have very little data at this point
and there are a lot of unanswered questions. I think the newspapers would very
likely sensationalize the story and leave people with only the (possibly
untrue) impression that all food grown in an urban environment is more toxic
than other food, or dangerous to eat. I think the subtleties of these issues
are going to be lost in a newspaper article.

Some of my unanswered questions are:

(1) How common is the occurrence of heavy metal contamination in back yards in
Halifax/Dartmouth? (Let’s test more places and see if there is a pattern.)
(2) What is the concentration of heavy metals in soil outside the urban area,
for example on rural farms? (What is the baseline with which we can compare?)
(3) What is the concentration of heavy metals in “clean” or “commercial” soil or
fill? (How do we know there are significant differences? Again – what is our
baseline condition?)
(4) What is the concentration of heavy metals in the foods produced on urban vs.
rural soils, on average and in specific cases where metal contamination has been
found. (In other words, how much of it actually gets into the food?)
(5) How can heavy metals be effectively removed from an urban yard using plants
(phytoremediation). Like another respondent, I have read research that suggests
that sunflowers will take up metals. My question is, then what do you do with
the sunflower plants?
(6) It’s virtually impossible to garden without touching soil (and in any case I
wouldn’t be interested in gardening if I couldn’t touch the soil). Compared with
other sources of heavy metals to our bodies, how much do we actually take in by
touching soil? And is washing the produce and washing our hands after gardening
a sufficient preventive action?

This must be a common enough issue that there are research papers out there to
be found. Now we just need a researcher 🙂

From erinn doncaster:
Here here, wayne! i totally agree that these questions addressing a)the scope of the problem and b) how we can effectively deal with it are important to answer before passing the story on to the media. i don’t think we want people to believe they should stop growing food in their backyards, so let’s figure out how to do it without giving anyone lead poisoning and pass that info on too. hooray for solutions.i was also wondering if there’s a cheaper way to get soil tested, or perhaps to test ones’ own soil?

From Greg Pemberton:

Here’s a good base with which to start though it os on a bigger scale than is useful. What is needed is a peninsula-only program that can be used as a model to push the idea out to all developed areas.

Developers are now required to harvest the type of data you are looking for when they start new developments but there is nothing requiring owners of existing housing to create the type of database you are looking for. Perhaps it could be built in to the deed transfer process that soil chemistry sampling be done and the results contributed to the peninsula database.

Another idea that would give a big start to initially ‘seed’ the database would be to have the city provide sample data for all HRM-owned properties on the peninsula. Also, get peninsula schools to do the same sampling and use it as a teaching tool for learning to interpret the results of chemical analysis and impact on enviro. ?Get something like Jacques-Whitford to sponsor the project?

This is definitely the type of idea that would be good to run by the MES program at Dal to see if it would become a student thesis topic.

These guys sound like a good place to start though their focus seems to be on water quality issues.
Soil & Water Conservation Society of Metro Halifax (SWCSMH)
From Dave Patriquin:
Dave McCall (North End Community Gardens Association) proposed a study of heavy
metals in urban soils a few years back and may have some info. on it (re:
question about costs etc.) With Brett’s tests and growing interest in community
gardens, it would seem to be a good project for a community garden association
to go after.

Crucifers like oil radish, white radish have been used by organic farmers to
clean up soils; they have deep tap roots, so pull things up from down deep,
also concentrate metals. There was a recent report suggesting use of Chinese
cabbage for soil remediation – maybe crucifers are a group to be wary of (as
urban vegetables) if the heavy metal content is not documented.
Here’s some info about crucifers and metals:

Brassicaceae (Cruciferae) Family, Plant Biotechnology, and Phytoremediation

Authors: Palmer, Constantine1; Warwick, Suzanne2; Keller, Wilf3

Source: International Journal of Phytoremediation, Volume 3, Number 3,
July-September 2001 , pp. 245-287(43)

Publisher: Taylor and Francis Ltd

Abstract:
Plants represent a natural environmentally safe way to clean or remediate
contaminated sites. Members of the Brassicaceae or Cruciferae plant family have
a key role in phytoremediation technology. Many wild crucifer species are known
to hyperaccumulate heavy metals and possess genes for resistance or tolerance
to the toxic effects of a wide range of metals. Metal uptake, sensitivity, and
sequestration have been studied extensively in Arabidopsis thaliana , and a
number of heavy metal-sensitive and ion-accumulating mutants have been
identified. This species is a likely source of genes for phytoremediation.
Within the Brassicaceae, Brassica and other crop species are likely candidates
for phytoremediation. There is a wealth of information on the agronomics of the
economically important members and biomass production can be extensive. Many of
these species are well adapted to a range of environmental conditions. Some
species are tolerant to high levels of heavy metals, and there is the potential
to select superior genotypes for phytoremediation. They are well suited to
genetic manipulation and in vitro culture techniques and are attractive
candidates for the introduction of genes aimed at phytoremediation.
Biotechnology and molecular biology are valuable tools for studies of metal
accumulation and tolerance in hyperaccumulating species and for the transfer of
relevant genes into crucifer species suitable for phytoremediation. The purpose
of this article is to review the potential use of both wild and cultivated
members of the Brassicaceae in phytoremediation.

I hope we roll this energy into getting some research together, a map of local contamination, information about what substances move into the growing plants, and what forms of bioremediation are best to use for what. Through NSPIRG perhaps we can get some funding – the next deadline is June 13th. This is truly an topic of Public Interest.

Also, it would be rad if we developed a fund to help people get their soil tested, some sort of subsidy program, perhaps developing a relationship with a lab too. If you want to rally this, please come forward. Can you imagine how beloved you’d be for either? Mmmhmmm, mm.

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