Contaminants’ Trigger Concentrations for Soil

Contaminants’ Trigger Concentrations for Soil

Contaminant	Planned Use	Trigger Values (mg / kg air-dried soil)
Group A (may pose hazards to health)		Threshold	Action
Arsenic	Domestic gardens, allotments	10	-
Arsenic	Parks, playing fields, open space	40	-
Cadmium	Domestic gardens, allotments	3	-
Cadmium	Parks, playing fields, open space	15	-
Chromium (hexavalent)(1)	Domestic gardens, allotments	25	-
Chromium (hexavalent)(1)	Parks, playing fields, open space	No Limit	No Limit
Chromium (total)	Domestic gardens, allotments	600	-
Chromium (total)	Parks, playing fields, open space	1,000	-
Lead	Domestic gardens, allotments	500	-
Lead	Parks, playing fields, open space	2,000	-
Mercury	Domestic gardens, allotments	1	-
Mercury	Parks, playing fields, open space	20	-
Selenium	Domestic gardens, allotments	3	-
Selenium	Parks, playing fields, open space	6	-
Group B (Phytotoxic - but not normally hazardous to health)		Threshold	Action
Boron (water-soluble) (3)	Any uses where plants are grown (2)(6)	3	-
Copper (4)(5)	Any uses where plants are grown (2)(6)	130	-
Nickel (4)(5)	Any uses where plants are grown (2)(6)	70	-
Zinc (4)(5)	Any uses where plants are grown (2)(6)	300	-
Group C - (Organic contaminants)		Threshold	Action
Polyaromatic hydrocarbons (7)(8)	Domestic gardens, allotments, play areas	50	500
Polyaromatic hydrocarbons (7)(8)	Landscaped areas, buildings, hard cover	1,000	10,000
Phenols	Domestic gardens, allotments,	5	200
Phenols	Landscaped areas, buildings, hard cover	5	1,000
Cyanide (free)	Domestic gardens, allotments, landscaped areas	25	500
Cyanide (free)	Buildings, hard cover	100	500
Cyanide (complex)	Domestic gardens, allotments	250	1,000
	Landscaped areas	250	5,000
	Buildings, hard cover	250	No Limit
Thiocyanate	All proposed uses	50	No Limit
Sulphate	Domestic gardens, allotments, landscaped areas	2,000	10,000
	Buildings (9)	2,000	50,000
	Hard cover	2,000	No Limit
Sulphide	All proposed uses	250	1,000
Sulphur	All proposed uses	5,000	20,000
Acidity	Domestic gardens, allotments, landscaped areas	pH<5	pH<3
Acidity	Buildings, hard cover	No Limit	No Limit

Notes:-

No limit - The contaminant does not expose a particular hazard for this use.

1. Soluble hexavalent Chromium extracted by 0.1m HCL at 37 ^o; solution adjusted to pH 1.0 if alkaline substances present.

2. Pure rainwater is slightly acidic, with a pH of about 6.5 (due to dissolved Carbon Dioxide). The soil pH value is assumed to be about 6.5, and should be maintained at this value. If the pH falls the toxic effects of uptake of these elements will be increased.

3. Determined by the standard ADAS method (soluble in hot water).

4. Total concentration (extractable by HN0₃/HCl0₄).

5. The phytotoxic effects of Copper, Nickel and Zinc may be additive. The trigger values given here are those applicable to the 'worst-case', phytotoxic effects may occur at these concentrations on acid sandy soils. In neutral (pH=7) or alkaline soils, phytotoxic effects are unlikely at these concentrations.

6. Grass is more resistant than most other plants to phytotoxic effects, hence its growth may not be adversely affected at these conditions.

7. Used as a marker for Coal Tar. See CIRIA, 1988 Annex 1.

8. See CIRIA, 1988 for details of analytical methods.

9. See BRE Digest 250 : 'Concrete in sulphate-bearing soils and groundwater.

Source: Interdepartmental Committee on the Redevelopment of Contaminated Land (ICRCL).