Maximum acceptable concentrations of Cd, Ni, Cr and Hg in agricultural soils depending on pH of the soil
1999
Nikolov, N. | Zlatareva, E. (N. Poushkarov Institute for Soil Science and Agroecology, BG-1080 Sofia (Bulgaria))
Maximum acceptable concentrations of the total content of Cd, Ni, Cr, and Hg depending on pH of the soil have been developed for the agricultural soils of Bulgaria using the results of pot experiments and field studies. The maximum acceptable concentrations af Cd in soil at pH 7 and pH 6 is 3.0 mg/kg soil and 1.5 mg/kg soil respectively. The maximum acceptable concentration of Ni at pH 7 and pH 6 are 70 mg Ni/kg soil and 60 mg Ni/kg soil respectively. Bioavailability of Cr is not as high as bioavailability of Cd and Ni, but Cr is phytotoxic. The maximum acceptable concentrations of Cr at pH 7 and pH 6 are 200 mg Cr/kg soil and 190 mg Cr/kg soil and 150 mg Cr/kg soil respectively. As a result the maximum acceptable concentration of Hg remains 1 mg Hg/kg soil for the whole range of pH 4- pH7. The increase of the bioavailability of Cd, Ni and Cr with decreasing pH is explained by their transformation into ionic form by the soil acidity related to the permanent changes of the soil.
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