Is this a meaningful question?
Shouldn't it rather be - at what concentration is a particular receptor
(human, rose bush, nematode worm, gas pipe) likely to be harmed?
ISO & BS 10175 defines contamination as the presence of potentially harmful
substances at [above natural background concentrations]as a result of human
Hence there is not threshold at which soils become defined as
Statistical techniques can be used to determine whether average
concentrations in a site are above the natural background concentration,
e.g. depending on the confidence required more that 2SDs or 3SDs above the
natural mean concentration.
Whether the contamination is harmful is a separate question and depends on
the soil function and receptors of interest. Humans are resistant to
elevated zinc concentrations but not all soil biota are. Grass is more
resistant than other plants. There cannot be a single threshold value that
defines "contamination" on the basis that it might cause harm.
If harm results it is "pollution". See also the 10th report of the Royal
Commission on Environmental Pollution published in 1984.
Which is why the statutory definition of "contaminated land" really
describes "polluted land". So much less confusion if that had been the term
M A Smith Environmental Consultancy
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From: Contaminated Land Management Discussion List
[mailto:[log in to unmask]] On Behalf Of Steve
Sent: 16 October 2014 15:10
To: [log in to unmask]
Subject: Threshold values for metals in soils
A colleague of mine is looking at overland flow on grassland after biosolid
application and wishes to obtain information on threshold values for metals
in soils before they are classified as contaminated.
The threshold criteria he is interested in is linked to human health risk.
Can anyone offer advice on sources of information for this. Thanks.
Dr Steve Thornton
Groundwater Protection and Restoration Group Kroto Research Institute North
Campus University of Sheffield Broad Lane Sheffield S3 7HQ UK
Tel : 44 (0) 114 222 5744
Mobile : 07855 074692
Fax : 44 (0) 114 222 5701