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Technical
Note Cyanide extraction from contaminated soil:
a method comparison Soils
on sites of former manufactured gas plants are usually contaminated with iron-cyanide
complexes. We investigated the extraction of cyanide from 23 contaminated soils by three
methods, which are prescribed by the German Federal Soil Protection Act and Ordinance: the
soil-saturation extract with water, SSE, with a very narrow soil:solution ratio; the
so-called S4 water extract with a soil:solution ratio of 1:10; and 1M NH4NO3
extracts with a soil:solution ratio of 1:2.5. Highest cyanide concentrations were found in
the SSEs ranging from 0.1 to 70.5mg/l. However, percental cyanide extraction was lowest in
these extracts. Cyanide concentration and percental extraction obtained by the three
methods were correlated among the methods with squared correlation coefficients ranging
from 0.45 to 0.80. The relationship between extract pH and cyanide extraction was weak. As
the results differed among the methods, they cannot be regarded as equivalent with respect
to cyanide extraction. Due to the narrow soil:solution ratio, the longer reaction time of
48h, and the strongest similarity between soil and extract pH, we recommend the SSE method
to investigate cyanide extraction from contaminated soil. |
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