scope:

This Technical Report describes the procedure to screen soil samples to detect Cr(VI) using test-kits based on water extraction of Cr(VI) in soil. The test-kit approach in this method is designed to quickly screen soil samples using calibration to indicate the concentration level. A batch test at a liquid to solid ratio of 10 l/kg, designated by ISO/TS 21268‑2, has been used in Japan for over 30 years to evaluate the risk of Cr(VI) contamination in soil. The Cr(VI) detection by a ready-to-use test-kit method follows ISO/TS 21268‑2.

This screening technique is applicable in laboratories but can also be applied for site screening in the field. The standard system detection covers the range mg/kg to % for Cr(VI).

This method is expected as a screening technique because of the significant colour change given by 1,5-diphenylcarbazide in the existence of Cr(VI).

The method may be especially useful in quickly detecting Cr(VI) where a site is assumed to have no Cr(VI) contamination. As with other screening techniques, it is advisable to confirm a certain percentage of both positive and negative test results in another technique, especially when the detected level is near or above a regulatory action limit or when the presence of background or interfering materials is suspected.

Basically, laboratory analysis requires longer time and higher costs than those of test-kit detection. If the same survey time and the costs are allowed with test-kit screening work and conventional investigation methods including laboratory analysis, the former way can work on more inspection spots than the latter. However, test-kit detection should carefully be adopted for site investigation because the recovery of Cr(VI) from soil into water dependent on soil matrices changes the performance of test-kit detection.