上海地区酸雨类型格局转变研究

采用STARS（Sequential 〖WTBX〗t〖WTBZ〗 test analysis of regime shifts），以降水中SO2-4、NO-3以及SO2-4/NO-3为指标，研究了上海地区酸雨类型在1991～2006年的格局转变规律。上海地区降水中SO2-4含量在1991～2006年具有两种格局，2004年发生转变；转变前的SO2-4含量平均12670 mg/L，转变后SO2-4含量大幅度降低，平均6525 mg/L；降水中NO-3含量存在3种格局，两次转变；1996年转变前的NO-3浓度相对较低，平均1842 mg/L；此次转变后升高，平均2622 mg/L；2005年再次发生转变，使得NO-3含量下降，平均1998 mg/L；与NO-3含量的格局类似，SO2-4/NO-3也存在着3种格局，两次转变；1995年转变前，SO2-4/NO-3平均7316；此次格局转变后，SO2-4/NO-3降为5666；2000年的格局转变中SO2-4/NO-3降为3635。表明NO-3对酸雨的贡献逐渐增加，SO2-4对酸雨的贡献逐渐减弱，酸雨类型逐渐由硫酸型酸雨过渡成硫酸和硝酸混合型酸雨，并逐渐接近硝酸型酸雨。上海地区酸雨类型格局在1991～2006年发生5次格局转变，其格局转变指数（RSI）在1995、1996，2000，2004和2005年分别为0826、0260、0959，1378和0066。〖

REGIME SHIFT OF ACID RAIN TYPE IN AREA OF SHANGHAI

At present，acid rain has aroused great concerns of people,but little previous research has been completed on regime shift of acid rain type.Based on the content of SO2-4,NO-3 and SO2-4/NO-3 in the rain of Shanghai,the regime shifts of acid rain type from 1991 to 2006,were studied by adopting the STARS（sequential 〖WTBX〗t〖WTBZ〗 test analysis of regime shifts）.There were two regimes of the SO2-4 content;one shift happened in 2004.Before the shift,it was 12.670 mg/L on average;after that,it decreased sharply to 6.525 mg/L.Whereas,there were three regimes,two shifts,of the NO-3 content.Before the first regime shift in 1996,it was 1.842 mg/L on average,after that,it increased to 2.622 mg/L on average till the second shift in 2005,then it decreased again to below 2.000 mg/L on average.Similar to the regime of NO-3 content,there were also three regimes of SO2-4/NO-3,shift twice.Before the first shift in 1995,SO2-4/NO-3 was 7.316;after that,it decreased to 5.666 till the second shift in 2000,then it decreased further to 3.635 on average.These indicated that during 1991～2006 in area of Shanghai,the contribution of NO-3 to acid rain increased,while the contribution of SO2-4 to acid rain decreased.The acid rain types were turning from sulfuric acid rain to sulfuric and nitric acid rain complex type,approaching the nitric acid rain type.Altogether,there were 5 regime shifts of acid rain type during 1991～2006 in area of Shanghai.The regime shift indices (RSI) were 0.826,0.260,0.959，1.378 and 0.066 in 1995,1996,2000,2004 and 2005,accordingly.〖