Formation Of Acid Rain And Reaearch Of The Dissolved Laws Of Heavy Metals In Dust Fall In Simulated Acid Rain

The formation of acid rain is a process of complex atmospheric chemistry and physics. The past research of acid rain emphasized on artificial acid contamination and neglected the natural factors at a certain extent. From the development of definition of acid rain we can see that natural factors are also very important. This must need data of sigal atmospheric particles. So we should develop methods of researching sigal atmospheric particles. Considering the sigal acid and anti-acid particles,this paper discussed a method of analyzing the process of acid rain through chemical transform of sigal particles. And it also researched the mathematic relationship between acid matter and anti-acid matter. In order to study the influence and harm of acid rain,this paper choose atmospheric dustfall as object,and study the dissolved law of heavy metal in dustfall under simulated acid rain from the angle of speciation analysis. From this step of research we can find the contaminated character of heavy metal in dustfall under the condition of simulated acid rain. We can also forecast the latency harm of acid rain,and supply a scientific proof of the study of the harm of acid rain.Through the research of the character of causing acid of SO₂ and NO_X,we can find that they almost have the same law of causing acid. Both of them have the strong capacity of causing acid. When their dissolved concentrations are more than 10mg/L,the acidity of the water become strong evidently.and the pH value drop to between 3 and 4. When SO₂'s dissolved concentration is about 65mg/L,the pH value of the water drops to below 3. And when it comes to NO_X,the dissolved concentration is 40mg/L. So NO_X has the stronger capacity of causing acid; When both of them are at low dissolved concentrations,the pH value of water drops evidently. As the congcentration increasing, the dropping tendency of the pH value becomes gently. When there is some oxidant in the water,the ability of causing acid of both of SO₂ and NO_X will be strengthened obviously.Through the research of character of anti-acid of CaCO₃ and CaO,we find that both of them have the strong ability of anti-acid. Comparely, the experiment of anti-acid efficiency of CaCO₃ preferably revealed the mathematic relationship between dissolved Ca²⁺ and the pH value in the water. And the result is that the reaction speed will become slowness when the pH value near to neutral, and the pH value will become stable.Through the research of contaminated character of heavy metal in dustfall,we find that there are different proportion of heavy metal speciations in different diameter of dustfall. Element Zn and Mn are mainly existing as exchangeable fraction, reducible fraction and residue fraction; Element Cr is mainly existing as oxidisable fraction and residue fraction; Element Pb is almost existing as residue fraction, and a small part of it is existing as reducible fraction; Element Fe is mainly existing as reducible fraction and residue fraction; Element Cu and Ni are existing as a certain proportion of all the four speciations. In a short word, the contamination of Pb and Cr are lightest comparatively,and the contamination of Cu,ZnmNi,Mn and Fe are existing at industrial area and utility area at different extentThrough the reseach of dissolved law of heavy metal in dustfall under mixed simulated acid rain,we find: the more stronger of the acidity of the water,the higher of the dissolved ratio of heavy metal in acid solution of different pH value. Element Cu,Ni,Cr and Mn in small diameter dustfall are more easily be dissolved; the dissolved ratios of Zn in different diameter have a very small difference. In both diameter dustfall,the increases of dissolved Pb and Cr are prominent as the pH value decreasing. The change of dissolved ratios of Cu,Zn and Fe is very small at different pH values. The dissolved heavy metals have differences when there is different proportion of sulfur and nitrogen in simulated acid rain. Analysis as whole, The dissolved heavy metals will increase when there is more and more nitrogen in the simulated acid rain. So we can get a conclusion that the acidity of the simulated acid rain will be strong as the concentration of the nitrogen increased, and the quantity of the dissolved heavy metals will be increased.