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作为我国北方地区酸雨最为严重的城市之一,青岛及其近岸区域酸雨的研究对揭示典型海陆人为交互作用下酸雨形成机理具有典型的示范性.本文从酸雨的现状及变化、酸雨形成机制及影响因素、雨水中致酸/碱性成分的来源人手,系统总结了青岛近岸区域酸雨的化学特征.结果表明,青岛近岸区域自1981年以来酸雨状况有所减轻,但2006年以来又有加重的趋势,并由“硫酸型”酸雨向“硫-硝混合型”酸雨转变-局地人为源SO2和NOx的排放、区域外污染物的输送以及海上浮游生物释放的二甲基硫(DMS)是该地区大气致酸物质的3条重要输入途径.大气中致酸成分前体物的浓度和排放强度、气溶胶中酸化缓冲/碱性物质的含量以及复杂多变的气象条件是该区域酸雨形成的主要控制因素-人为源和地壳源分别是大气中致酸成分和碱性成分的主要来源,海盐源硫酸盐气溶胶会对降水酸性产生一定的稀释作用.今后的研究应特别重视:(1)降水pH的动态变化及与大气颗粒物的相互作用;(2)低分子有机弱酸、重金属及与污染有机物的复合污染作用机制对酸雨的影响;(3)优化酸沉降模型,精确量化解析不同来源对雨水酸性成分的贡献;(4)雾、露、霜等其它形式的酸沉降及沉降通量.深入研究青岛近岸区域酸雨的地球化学特征,不但有助于加深对海陆人为交互作用下我国东部沿海经济发达地区大气污染与酸沉降形成机理及其生态效应的认识,还可为科学制定酸雨防控对策提供理论依据.

As one of the most seriously suffered cities from acid rain in the north of China,Qingdao and its coastal area is typical for revealing the formation mechanism of acid rain under the representative interactions among sea,land and anthropogenic activities.In this paper,the chemical characteristics of acid rain in Qingdao coastal area were systematically summarized via the current status and variation,the formation mechanisms and its affecting factors,and the origins of acid/alkaline components in rainwater.The results indicated that the acidity and frequency of acid rain had been decreasing since 1981 but enhanced again from 2006,and the type of acid rain changed from "sulfuric acid" to "sulfuric-nitric acid mixture".The emissions of SO2 and NOx from the local anthropogenic activities,long-range transport of external atmospheric pollutants,and dimethylsulfide (DMS) released from marine planktons are the three major sources of acidic substances in the air of Qingdao coastal area.Meanwhile,concentrations and emission intensity of atmospheric acidic precursors,contents of buffer or alkaline substances as well as the changeable meteorological conditions are the three primary factors that control the formation of acid rain in this region.In the rainwater,the acidic components are mainly anthropogenic,but alkaline components are from crustal sources.The aerosol originated from sea salt may exert a dilution effect on the acidity of rainwater to a certain degree.Several suggestions for further studies on acid rain in Qingdao coastal area were put forward as follows:(1) to focus on the dynamic variation of pH in rainwater and its interaction with atmospheric suspended particles;(2) to focus on the combined effects of multiple pollutants of weak organic acids with low molecular weight,heavy metals and organic pollutants in acid rain;(3) to optimize the acid deposition models for accurately analyzing the contributions of different sources of acidic components in rainwater;(4) to strengthen the studies on other forms of acid deposition such as fog,dew and frost and their fluxes.Further studies on the geochemical characteristics of acid rain in Qingdao coastal areas are not only beneficial to getting a deeper insight into the formation mechanism as well as the ecological environmental effects of air pollution and acid deposition under the interactions among sea,land and anthropogenic activities in the developed eastern China coastal areas,but could also provide theoretical basis on scientific strategies of prevention and control of acid rain.