西南地区酸雨形成大气化学过程

通过野外观测、实验室实验和数值模拟研究了西南地区酸雨形成大气化学过程.新认识如下:①人为排放引起的酸雨及空气污染,目前尚未明显波及到西藏高原;②在重污染区SO_2污染严重,不管降水云是否酸性或污染,降水总是酸性、受污染的,云下洗脱痕量气体及颗粒物起重要作用,氧化剂是降水酸化的控制剂;③在典型农村地区,降水化学组成依赖于降水云的化学组成,即依赖于云化学,酸化过程中SO_2是控制剂;④该地区主要氧化剂是H_2O_2,高度越高,云水中H_2O_2含量越高;⑤该地区是硫酸型酸雨,硝酸含量有上升趋势,在考虑降水酸度时有机酸贡献不可忽视;⑥降水中很多元素来自颗粒物,颗粒物缓冲参数化并耦合到云下洗脱模型中,大大缩小了观测与数值模拟的降水酸度之差.

Atmospheric Chemical Process for the Formation of Acid Precipitation in Southwestern China.

The atmospheric chemical process for the formation of acid precipitation in southwestern China was studied by field experiments, laboratory experiments and numerical simulation. The findings are as follows: 1. acid rain or air pollution resulting from anthropocentric emis-sion has not significantly affected Tibetan Plateau; 2. SO2 episodes always happened over heavy polluted areas, especially industrial areas or big cities, so the below-cloud scavenging of trace gases and particulates plays an important role for the formation of acid precipitation, no matter how the precipitating cloud is polluted or acidic or not, the oxdant is controlling reagent for the acidification of the precipitation in these areas; 3. The chemical composition of precipitation in typical rural area is dependent on that of precipitation cloud, i. e. dependent on cloud chemistry, where SO2 is the control reagent; 4. The major oxidant in this subtropical area is H2O2. The higher the altitude tlie higher the concentration of H2O2 in cloud water would be. 5. Acid rain in this area is sulfuric acid type, nitric acid content has an increasing trend and the organic acid must be accounted for acidity of the precipitation. 6. No simple relationship was found among H+, NH4+ Ca+2 Mg+2, SO4-2 and NO3- in precipitation. Many elements in precipitation were contributed from atmospheric particulates. Parameterizing buffering of particulate and coupling it tp belowcloud scavenging model, the acidity gap of rain between field measurement and simulation, was much narrowed.