The Study On The Effect Of The Citric Acid, Iron Oxide Interaction To The Copper And Cadmium In The Soil

Tongling located at middle and lower reaches of the Yangtze River where there is an iron and copper metallogenic belt, and the area is rich in iron, copper, sulfur and gold mine. As a mining area, long time of mining related activities left large amounts of tailings, which have brought serious environmental problems of heavy metals.While the biotoxicity of heavy metal not only relates to the concentration but also to the morphological in further. Different morphological can cause different environmental effects, affect the toxicity, migration and the circulation in nature of heavy metals. Exchangeable fractions and carbonate bound bring more harmful to humans and the environment; Fe-Mn oxides bound and organic are more stable, but can release when external conditions changed; Residual is known as unavailable state, which is not easily released.Nowadays, according to the and biotoxicity of, there are two way to remand the soils contaminated caused by heavy metals: (1) To change the speciation of, made they fix up to soil so as to reduce the mobility and bioavailability;(2) To increase the activity of heavy metals to made they easily absorbed by plants, then heavy metals can be move out.Due to the importance of the morphological in the heavy metals pollution of soil, we have investigating the state of the copper and cadmium of the garden soil form Xinqiao in Tongling and the change of the state which in different environment include that the different PH, content of the citric acid and the goethite, and the interaction of the citric acid and the goethite. We can conclude that:1.The content of the copper and cadmium in the soil are far more than background values, in which, the copper is dominated by the residue form and the cadmium is by the exchange form. Both of which are more harmful to the organism and environment.2.The organically combined form and the carbonate form content of the copper and cadmium are positively correlated with the PH.3. Every state of copper in the soil content is almost constant in the different citric acid content and which is the highest in the 3 mol/kg. we can conclude that the role of copper is passivation; every state of cadmium changes are obvious, and in which the organic combination state and the residue state convention to the other three states.4.Every state of the copper and the cadmium in the soil are influenced by the PH when added the acid, however the varies will be slacked down because of the complexation of the citric acid.5. For copper, the goethite showed the passivation effects which made the content of the bioavialiable state decreased and the residual state increased; while for cadmium the of the exchange state and the organic combination state are decreased, both of the content of the carbonate and the iron manganese oxide state are higher than normal and the residue is lower than normal.6. The adsorption will be enhanced by the goethite-citric acid compound colloid which from the citric acid and goethite interaction.