Surface Waters (Dangerous Substances) (Classification) Regulations (Northern Ireland) 1998

regulations 3(1) and 4(4)

SCHEDULE 1 Criteria for Classification DS1

The criteria for the classification DS1 are that the annual mean concentration of each substance listed in column (1) of Table 1 in samples taken from the sampling point for the waters in question in accordance with regulation 4 does not exceed the relevant limit specified in column (2) of that Table.

TABLE 1

(1)	(2)	(3)
Substance	Concentration in microgrammes per litre (annual mean)	Reference method of measurement
(1) The accuracy and precision of the method must be plus or minus 50% at a concentration which represents twice the value of the limit of determination. (2) The accuracy and precision of the method must be plus or minus 30%.
Aldrin Dieldrin Endrin Isodrin	0.01 0.01 0.005 0.005	Gas chromatography with electron capture detection after extraction by means of an appropriate solvent with a limit of determination of 2.5 ng/1(1).
Cadmium and its compounds	5 (total cadmium: both soluble and insoluble forms)	Atomic absorption spectrophotometry after preservation and suitable treatment of the sample. The limit of determination is .25 µg/litre(2).
Carbon tetrachloride	12	Gas chromatography. The limit of determination is 0.1 µg/litre(1).
Chloroform	12	Gas chromatography. The limit of determination is 0.1 µg/1itre(1).
DDT (all isomers)	0.025	Gas chromatography with electron capture detection after extraction by means of a suitable solvent. The limit of determination for total DDT is approximately 4 ng/l, depending on the number of extraneous substances present in the sample(1).
para-para-DDT	0.01	Gas chromatography with electron capture detection after extraction by means of a suitable solvent. The limit of determination for total DDT is approximately 4 ng/l, depending on the number of extraneous substances present in the sample(1).
Hexachlorobenzene	0.03	Gas chromatography with electron capture after extraction by means of an appropriate solvent. The limit of determination shall be within the range 1 to 10 ng/1 depending on the number of extraneous substances present in the sample(1).
Hexachlorobutadiene	0.1	Gas chromatography with electron capture detection after extraction by means of an appropriate solvent. The limit of determination shall be within the range 1 to 10 ng/1, depending on the number of extraneous substances present in the sample(1).
Hexachlorocyclohexane (all isomers)	0.1	Gas chromatography with electron capture detection after extraction by means of an appropriate solvent. The limit of determination shall be within the range 1 to 10 ng/1 depending on the number of extraneous substances present in the sample(1).
Mercury and its compounds	1 (total mercury: both soluble and insoluble forms)	Flameless atomic absorption spectrophotometry after suitable pre-treatment of the sample which takes account in particular of pre-oxidation of the mercury and of successive reduction of the mercury ions Hg(II). The limit of detection must be 0.1 µg/litre(2).
Pentachlorophenol and its compounds	2	High pressure liquid chromatography or gas chromatography with electron capture detection after extraction by means of a suitable solvent. The limit of determination is 0.1 µg/litre(1).