Acid rain has been a well-known environmental problem for decades and can lead to acidification of surface waters and soils. Besides, rapid economic growth and increased energy demand have resulted in severe air pollution problems through-out China, particularly in and near the large cities.  The statistical reports show that acid precipitation has affected about 30% of China and those seriously affected areas are mainly located in the economically developed regions in the east, the south and the center of China.

Prof. HAN Guilin from Institute of Geochemistry, Chinese Academy of Science (IGCAS) and her colleague Prof. WANG Hua from Xihua University reported the severe acid rain over Chengdu, based on the continuing sampling rain samples throughout the whole 2008. Their main concluding remarks include: 1) the concentrations of NO3− in Chengdu city were higher than in the most polluted cities abroad, which indicated Chengdu has been a severe polluted city over the world. 2)The high fuel consumption from urbanization and the rapid increase of vehicles resulted in the high emission of SO2 and NOx, which were the precursor of the high concentration of acidic ions NO3− and SO42−. That was the main reason of the severe acid rain in Chengdu. 3) The high concentrations of alkaline ions (mainly Ca2+, NH4+) in Chengdu city atmosphere have played an important role to neutralize the acidity of rainwater and the pH value has increased by 0.7 units since 1989.  However, it is worth noting that the emission of NOx from the automobile exhaust is increased and becoming the important precursor of acid rain now.

The research results titled "Chemical composition of rainwater and anthropogenic influences in Chengdu, Southwest China." was published in Atmospheric Research (2011, 99(2): 190-196 ).

This work was supported jointly by the Innovation Program of Chinese Academy of Sciences (No. KZCX2-YWQN109) and the Chinese National Natural Science Foundation (No. 40721002, 40973088)

(Provided by WU Qixin)