Characteristics Analysis Of Chemical Composition Of Wet Deposition During Sixteen Years In Shanghai City And Its Causes Research

This topic analyzes statistic results of Shanghai wet deposition monitoring data during sixteen years(1992-2007).It analyzes the variations of chemical composition of wet deposition during these years. Based on an abundance of wet deposition monitoring data of latter years, the sources of the ions are analyzed with a factor analysis method.A stepwise linear multi-variation regression model is established to predict the concentration of hydrogen ion.Based on the result of the model, combining the variations of chemical composition of wet deposition with the ions' predecessors' concentration,the causes of chemical characteristics variation and pH value decreasing of wet deposition are explained.Furthermore,a method for filtering abnormal wet deposition monitoring data is present. Main conclusions are drawn from analyzing wet deposition monitoring data during sixteen years:pH value,So₄^2-,Ca²⁺,F^- and EC value declined;No₃^-,Cl^-,Na⁺,Mg²⁺,K⁺ varied slightly;acidification frequency increased.During the year 2003 to 2004,all the ions declined in different extents;acidification frequency increased dramatically after year 2003;acidification frequency has a significant linear relationship with So₂,dust and some of the ions in wet deposition.Combining with the results of stepwise linear multi-variation regression model of H+ with the variations of chemical composition of wet deposition,it sums up that the declining of So₄^2-/No3^-,Ca²⁺/NH₄⁺ and(Ca²⁺ +NH₄⁺ )/(So₄^2- +No₃ ^-) results in the decreasing of pH value and the increasing of acidification frequency together.Moreover,according to the relationships among the wet deposition monitoring indexes,based on the monitoring data of 682 wet deposition samples,scatter-plot graphs are made.With the principal that keeping the plot in the graphs' 90%predicted interval while ticking the others out as abnormal data,the method for ticking out abnormal monitoring data is put forward,and is testified by the monitoring data of first six months in year 2008.