| Water environment pollution is a major environmental problem faced by the social and economic development.The heavy metal pollution in the water is the key point of prevention because of its serious impact on the water environment.On January 15,2012,there was a serious accidents of cadmium pollution in Longjiang River,about 20 tons of cadmium was discharged into Longjiang River,and the ecological environment caused serious damage.Heavy metal cadmium as the main research object in this study,from the itself characteristics and environment conditions,studying the characteristics of water body and the external influence factors on the impact in the form of heavy metal migration and distribution;Through laboratory tests,the migration and pollution characteristics of heavy metals under different environmental conditions and emergency treatment conditions were studied.The migration model of heavy metal cadmium pollution in Longjiang River was constructed based on a large number of measured data.Aiming at the shortcomings of the karst area routine river water quality monitoring,puts forward the biological monitoring technology applied to water quality monitoring,and establish the diatoms biological database,and visual display.The main research results of this paper are as follows:(ⅰ)The Ca2+ and HCO-3 are mainly ions in Longjiang River,and the rive belongs to the calcium carbonate group Ⅲ type water;Under Water quality standards,the floating Cd2+ percentage of Longjiang River water is more than 70%.Under the pollution condition,the percentage of the floating Cd2+ ions in the water is more than 80%.(ⅱ)After the cadmium pollution in the longjiang river,the mainly ion was floating Cd2+ ions in the water.PH has obvious effect on the morphology of Cd2+ions.The effect of the ratio of mud to water on Cd2+ was significant,and the adsorption process was mainly in the first 30min.The changes of water temperature and sediment particle size had no significant effect on the adsorption of Cd2+ in Longjiang River.(ⅲ)The pH of water has significant influence on coagulation effect.When water pH<8,cadmium removal rate as the PAC(polyaluminium chloride)dosing quantity increases,but the effect is not significant,when the pH>8,heavy metal removal rate increased with the increase of PAC dosing quantity increase,increase obviously;In the range of pH value from 7 to 9,Cd attenuation coefficient(y)has a good correlation with PAC(x)investment.The equation of correlation is:y =-0.0004x2 + 0.0690 x-0.2479.(ⅳ)The cadmium content in Longjiang River increased with the increase of flow velocity and decreased with the increase of pH value.The cadmium content in sediments was the lowest in the high water period and the highest in the dry water period.The main factors influencing cadmium in sediments were pH during the normal period and the wet period,and pH value and organic matter content were the main factors influencing cadmium in the dry period.(ⅴ)Cadmium in the sediments of longjiang river is mainly composed of ferromanganese oxides.The form of heavy metal cadmium is related to heavy metal content in sediments and is affected by pH value of water,pH value of sediment and organic matter in sediments.Different forms of heavy metal cadmium in sediments can be converted to each other.(ⅵ)The visualized model of cadmium pollution was developed,and the simulation value of the model was compared with the measured value of the cadmium pollution accident in longjiang river in 2012,which verified the rationality and feasibility of the model.(ⅶ)There was a significant positive correlation between diatoms and heavy metals.Benthic diatoms can well reflect changes in heavy metals and water pollution. |
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