Study On Economic Cost-benefit Analysis Of The Crops' Losses By Acid Precipitation Based On GIS

Without the pollutants in the atmosphere,the precipitation acidity is made up of H₂CO₃ caused by CO₂.The range of pH is from 5.6 to 9.0.Therefore,the precipitation whose pH is below 5.6 is called acid rain.In the 1950s,the English Chemist R.A.Smith found that there are sulphuric acid and sulphate in the atmosphere of Manchester during analyzing the compomnents in precipitation.After deeper research,he first used Acid Rain in his book Atmosphere and Precipitation:The beginning of Chemical Climatology in 1872.The precursor of acid rain is SO₂ and NO_x,while the contribution rate of SO₂ to global acid precipitation is 60%～70%.With the high-speed development of economic in Asia,the consumption of fossil fuel is growing higher and higher.The discharge amount of SO₂ and NO_x is larger than South Amercia and Europe which is in the top place of five continents.China is the third acid rain zone while the former are South Amercia and Europe and the area is becoming larger and larger.The area of acid rain zone is rapidly growing.Hunan province is located in the middle acid rain zone of China in which the phenomenon is the worst.The frequency of acid precipitation comes to 90%in Zhuzhou,Changsha,Xiangtan and so on.According to the analyzing of acid rain samples,the positive ions in it are H⁺,Ca²⁺,NH₄⁺,Na⁺,K⁺,Mg²⁺ while the negative ions are SO₄^2-,NO₃^-,Cl^-,HCO₃^-.In this research,PLS(Partial Least Squares) is selected to establish the dose-loss equation of crops in different cities in Hunan province caused by acid precipitation. The method is a effective means of solving the relativity among independent variables proposed by S.Wold and C.Albano in 1983.It can not only filter the variables much simply,but also retain all variables in the final model.In addition,it can be also used in the situation in which the number of samples is less than variables.In a word, modeling used the PLS is more reliable than other means.In this research,the values of precipitation ions and the crops' loss are selected to establish the equation.The ions such as pH,Ca²⁺,NH₄⁺,Na⁺,K⁺,Mg²⁺,SO₄^2-,NO₃^-,Cl^-are considered as variables respectively noted x₁,x₂,……,x₉ while the loss is considered the objective function noted y.The equation of dose-loss caused by acid precipitation is set up by using the method of PLS1.Geographical Information System(GIS) is a system whose function is to save, manage,analyze,display and apply the geographical informations,which is also the universal technology of analyzing and processing giant geographical data.GIS is widely applied to the making of thematic map,the establishment of environmental geographical information system,environmental monitoring,environmental impact assessment,etc.Spatial Analysis is a technology to analyze spatial data based on the characteristics of location and form of geographical targets whose aim is to refine and transport the spatial information.The theory of spatial interpolation in GIS is that the characteristics are similar as the locations are adjacency.The method is used to transform the data of discrete points to continuous numbers.The gebraeuchlich methods are IDW(Inverse Distance Weighted),GPI(Global Polynomial Interpolation), LPI(Local Polynomial Interpolation),RBF(Radial Basis Function),etc.In this research,IDW is selected to interpolate and analyze according to the data analysis. The pictures of precipitation ions are gained by spatial interpolation in different cities of Hunan province.The conclusion are as follows:(1)The place in which the concentration of SO₄^2- is the lowest is located in southern Hunan which Yongzhou city is given the first place.The concentration in other places is above 12mg/L.(2) The place in which the concentration of NO₃^-is the highest is located in estern Hunan which Changsha,Zhuzhou and Xiangtan are given the first places.(3) The places in which the concentration of Ca²⁺ is the highest are Changsha, Yueyang and Loudi cities.(4) The place in which the concentration of NH₄⁺ is the highest are Yueyang, Changsha and Zhuzhou cities where the concentration of SO₄^2- is the highest. Although NH₄⁺ neutralizes certain SO₄^2-,the value of pH is still high.Therefore, the relative concentration between NH₄⁺ and SO₄^2- is not the crucial factores resolve the value of pH in Hunan province.The grid of 40km×40km is established in the software MapInfo.The spatial overlay finished in the software of ArcGIS.In ArcGIS,the predicted map of concentration of precipitation is generated through interpolation.The predicted maps, grid and administrative maps are overlaied to gain the gridding map.The concentration of precipitation ions in each city is extracted and the concentration in each grid is gained.The function of Field Calculator in ArcGIS is used to obtain the crops' loss caused by acid precipitation.In sum,the research is modeling on natural precipitation which breakthrough the economic loss study based on simulant acid precipitation.Apart from this,the crops' loss caused by acid precipitation is gained through the software of ArcGIS.