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Free cyanide effects on environment

Information needed on any effect residual free cyanide left after a gas work site 'cleanup' may have on the food chain or those living in close proximity. Simple answers required as I have no scientific basis to work from.

Audrey A [last name deleted for privacy by Editor]
- Masterton, New Zealand
2003

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Audrey, I am not familiar with "gas work site cleanup" so I can't visualize what you may be talking about. Cyanide is both a very powerful and fast acting poison and a well recognized part of the food chain, thus making an attempt to answer generalized questions like yours tricky. We would need a much more detailed description of what you saw or thought you saw before anyone would be able to guess if there was any remaining danger. Sorry. Ted Mooney, P.E. Striving to live Aloha finishing.com - Pine Beach, New Jersey 2003 A digestion analysis for total cyanide will give you an absolute answer. CN forms an extremely tight bond with iron that can only be broken by boiling it in sulfuric acid and collecting the fumes, Therefore, an analysis for amenable CN is a very practical analysis since you have 0.0 to worry about from the CN tied up with iron. Unless the spill was massive or your soil has no iron, you probably have little to worry about. James Watts - Navarre, Florida 2003

My question re spent oxide relates to the land behind my house which was once the site of a gas works - where gas for heating, cooking etc was manufactured from coal/coke then piped to houses/businesses. Remediation took place some years ago but I am informed that A small amount of spent oxide remained mixed with the top 300 mm of soil. The ground leading to my property slopes towards me and then carries on. I am concerned that in the event of rain some run off (which does occur as water pools where it cannot find an exit once the ground is saturated) may carry with it contamination. I grow my own vegetables and fruit, keep hens and want to be able to relax that all is as it should be. There were a number of other contaminants as well. The land (which covers quite a large area) has been left idle since the remediation. I have suggested that the Council plant it in native trees to encourage bird life etc but I think they have their head in the sand about it and wish that I did too. The consultants report (of which I have a copy) says "It is not always possible to ensure that all areas of contamination are removed, hence some control should be put over the long term use.... the most 'sensitive' land use in terms of exposure is residential...it is recommended that this use is prohibited."

I don't know if you will welcome this information but I must tell you that it was heartening to find your response to my question. The web sure shrinks the world doesn't it?

Thanks for your interest (a social worker without any scientific bent whatsoever).

Audrey A [last name deleted for privacy by Editor]
- Masterton, New Zealand
2003

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If the site remediators and the town were unable to offer further insight, Audrey, it is unfortunately a little unrealistic to think someone from another continent will be able to accurately assess the dangers from an Internet posting :-)

But I doubt that there is any cyanide danger after these years! That doesn't mean it wasn't once very dangerous, but cyanide is a naturally occurring biodegradable material. I don't know, however, if a gas operation like this would involve the very common persistent industrial contaminants trichlorethylene and hexavalent chromium. And whether there are waste products from putting mercaptan into gas, etc., is something you would probably need to find out from a gas site rather than a metal finishing site. Sorry, and good luck.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2003

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January 14, 2009

Audrey

I work in the contaminated land industry and specialise in former gasworks, both investigating and remediating. Cyanide is a common component of a waste product known as Spent Oxide, which can be identified by a blue-white colouration.

In order to remove impurities such as hydrogen sulfide, carbon dioxide and hydrogen cyanide from the gas, the gas was passed through ferric oxide. 'Spent' oxide was often revivified on the ground surface or disposed of on-site.

The principal contaminants involved may include free sulfur, sulphate, sulfide, cyanides and thiocyanate. Complex cyanides may generate free cyanide under strong alkaline conditions or during combustion of complex cyanides. Hydrogen cyanide may be generated from free cyanide.

As mentioned by a previous response, the most dangerous Cyanide compounds (free cyanides) become locked with other elements making them more stable chemically and less of a risk.

The main issue here seems to be your vegetable patch and any contact you may have with the soil in your garden. But I would not worry too much as your situation is a common one, gasworks were (and still are) often surrounded by packed residential areas. Unless your house was built on top of the former gasworks land, it is unlikely you will have spent oxide concentrations within the soil of your garden to present any serious risk.

The main things you need to establish are:
-When was the site remediated?
-What was / is the land used for post remediation?
-What were the findings of the site investigation (contamination distribution, surface water drainage and flows? etc).

I am not sure how the legal systems work in NZ, but over here the land owner of the former gasworks is under legal obligation to ensure their land does not pose a risk to adjacent properties or land users. If you feel you are at risk, you should have a right to contact the land owners, where they should prove to you all previous risks have been dealt with.

I would be happy to help more if I can.


Best Regards,

Jay Bray
- Cardiff UK