Study On Release Of Cadmium From River Sediments After Emergency Treatment Of Cadmium Pollution Incidents

Coagulation can effectively remove cadmium from contaminated water under alkaline conditions, but it can generate a lot of floc. This study focused on the secrity of sediment containing cadmium-floc in Longjiang river generated when treated with flocculating constituent after cadmium pollution incidents. Combined with labor simulation and actual field monitor studies, the paper explored the principle of cadmium release from cadmium-floc, and thus be helpful to safe disposal of river sediments containing cadmium.The results showed that cadmium concentration of river water increased with the decrease of water pH under the conditions of mud sediment, sand sediment and stone sediment. Compared with conditions of mud sediment, Cadmium concentration was lifted larger under conditions of sand sediment and stone sediment. In the simulated flood experiment, cadmium concentration of river water under stone sediment conditions was1.1times greater than standard. However, as a result of cadmium adsorption by suspended mud, cadmium concentration of mud sediment river water did not exceed the standard under flood conditions. Actual field monitor studies in Longjiang river showed that cadmium concentration of water in portions of mid sedimentary river was2.1greater than standard at the very day of the first flood but decreased to below standard with time going. This may because this portion is made up of stone sediment and the cadmium-foc has been transpored to downstream. As well as water in portion of downward sedimentary river, water in both sides of portion of sedimentary river contained more cadmium than standard (but not greater than1times) in the beginning4(more than4days for downward sedimentary river) days after the first flood. Longjiang river cadmium level went to below standard with the join of Rongjiang river. After the second flood, water of portions of both sediment and downward river went below the standard. After the two flood, Longjiang river was nearly safe. However, the final fate of cadmium-floc has to be studied in the future. The present study provided basis for safe disposal of heavy metal contained sediment after cadmium pollution incidents.