【作者】 马琳；

【导师】 王韬； 陈建民；

【作者基本信息】 复旦大学 ， 环境工程， 2011， 硕士

【摘要】 酸性降水带来的生态破坏和经济损失,已经引起了人们的高度重视,酸沉降及其降水化学组成一直是国内外研究的重点。上海是世界上大气污染严重的城市之一,为了研究上海市大气降水的区域污染特征,本论文于2009年5月～2010年4月在复旦大学内(代表城区)和崇明东滩湿地(代表清洁背景点)设立雨水采样点,共收集有效样品109个。测定了样品的pH值、电导率、主要水溶性离子(S042-、N03-, F-、C1-、NH4+、Na+、K+、Ca2+、Mg2+)和有机酸(CH3C00-、HCOO-、C2O42-)组分的浓度,对比分析两站点的降水酸度、离子组成、浓度水平、时空变化、污染特征,并利用相关性分析、富集因子法、不同源的贡献及后向气流轨迹的方法对上海市大气降水做源解析。结果表明,复旦降水的pH值变化范围是3.92～6.82,年均值是4.54,酸雨频率80.6%,37.3%的降水为强酸性；崇明站点降水的pH值变化范围是4.02～7.70,年均值是5.24,酸雨频率50%,整体呈弱酸性水平。复旦和崇明降水中电导率的加权均值分别是31.37、17.49μS/cm,冬季均最高而夏秋较低。崇明整体空气质量良好,大气中污染物浓度较城区低。电导率和降水离子总浓度呈显著的负相关。复旦和崇明降水中离子加权总浓度分别为434.11、283.88μeq/L。SO42-、N03-和Ca2+、NH4+离子之和分别占复旦和崇明降水离子总浓度的72.56%和42.26%,是降水中最主要的酸性和碱性成分,其加权浓度分别为SO42-120.10/52.27μeq/L, NO3- 50.62/21.39μeq/L, Ca2+80.61/27.13μeq/L, NH4+63.66/33.36μeq/L。上海已成为世界上酸雨污染严重的城市之一,能源消耗和机动车带来的SO2和NOχ的大量排放是降水中SO42-、NO3-浓度升高的原因。Mg2+、K+, Cl-和Na+的浓度冬季最高秋季次之；SO42-、NO3、NH4+和Ca2+表现出冬季浓度高而秋季最低的特征。复旦和崇明降水中SO42-/NO3-当量比的加权均值分别为2.62和2.44,低于我国平均水平6.24。降水表现出燃煤型向煤油混合型污染转变的趋势。NH4+、nss-Ca2+和nss-Mg2+的中和因子的加权均值分别为NH4+0.43/0.50, nss-Ca2+ 0.50/0.45、nss-Mg2+0.09/0.10。不论是上海城区还是崇明湿地,NH4+和Ca2+都是降水中最主要的中和酸性物质的离子,Mg2+的中和作用较弱。复旦降水中Ca2+的中和作用更为明显,而崇明则是NH4+强于Ca2+。相关性分析表明,复旦大气中中主要是CaSO4、Ca(NO3)2等成分,崇明大气中则主要以(NH4)2SO4、NH4HSO4、NH4NO3等颗粒物的形式存在。复旦和崇明降水中有机酸(甲酸、乙酸和草酸)总量分别为3.01,3.64μeq/L,分别占阴离子总浓度的1.35%、2.49%。甲酸、乙酸主要来源于人为源或生物源的直接释放,草酸则来自于二次有机气溶胶。源解析表明,复旦和崇明降水中的SO42-、NO3-、NH4+和大部分Ca2+主要来自于人为污染,Na+和大部分Cl-来自于海洋,复旦降水中的大部分Mg2+来源于地壳源而崇明降水中主要来源于海洋。复旦降水中的K+大部分来自于人为源和地壳源,崇明降水中的K+主要由地壳源贡献。复旦降水中的离子成分主要受人为污染源的影响,其次为海洋源、地壳源；崇明降水中海洋源与人为源对离子浓度的贡献相当,地壳源最少。后向气流轨迹分析表明崇明降水主要受海洋风向的影响,东北、西南方向的污染物质的中长途输送和长三角地区人为排放造成的区域污染是造成崇明东滩酸雨最主要的原因。来自东亚、台湾地区的人为污染的影响也不容忽视。更多还原

【Abstract】 Great attention has been paid on serious ecological damage and economic losses caused by acid precipitation. Study on precipitation and chemical characteristics is always one of the highlight of atmospheric wet deposition over the world. Shanghai has been a heavy air-polluted city over the world. In order to understand the regional pollution characteristics of rainwater over Shanghai, one hundred and nine rain samples were collected from May 2009 to April 2010. The two sites located at Fudan University and Chongming Dongtan wetland, standing for the urban and background station. pH value, electrical conductivity, major water-soluble ions (SO42-、NO3-、F-Cl-、NH4+、Na+、K+、Ca2+、Mg2+) and organic acid (CH3COO-、HCOO-、C2O42-) were quantitatively measure of the rainwater. The precipitation’s acidity, constituents, concentration level, temporal and spatial variation, pollution feature were analyzed comparatively between the two sites. Inter-relationship, enrichment factors, different sources and backward trajectory analysis were used to identify the potential sources of Inorganic ions.The results showed that the volume-weighted pH value of rainwater in Fudan was 4.54, with the range of 3.92-6.82. The pH value of rainwater in Chongming was 4.54, with the range of 3.92-6.82. The frequency of acid rain was 80.6% and 50% respectively. The volume-weighted electrical conductivity was 31.37 andl7.49μS/cm of rainwater in Fudan and Chongming, respectively, which indicated good air quality and low pollution in Chongming. Negative correlation was showed between electrical conductivity and total ion concentrations.The annual volume-weighted total ion concentrations of rain were 434.11 and 283.88μeq/L in Fudan and Chongming respectively. SO42-,NO3, Ca2+and NH4+ were major anions and cations, respectively. The annual volume-weighted concentrations of SO42-, NO3, Ca2+and NH4+in rain were SO42-120.10/52.27μeq/L, NO350.62/21.39μeq/L, Ca2+80.61/27.13μeq/L, NH4+63.66/33.36μeq/L, and about 72.56%,42.26% in total ion concentrations in Fudan and Chongming’s rain. The high coal/fuel consumption and the rapid increase of vehicles resulted in the high emission of SO2 and NOx caused high concentration of SO42- and NO3, which were the main reason of the severe acid rain in Shanghai. Temporal variation of Mg2+, K+, Cl- and Na+showed the seasonal trends of high concentrations in winter/autumn, while SO42-, NO3-, NH4+and Ca2+peaked in winter and lowest in autumn. The volume-weighted ratio of SO42-/NO3- was 2.62 and 2.44 of rain in Fudan and Chongming respectively, which were than the average lever,6.24, in China. This indicated the style of rain pollution was from the type of sulphur to mixture type of vitriol and nitric acid. The enrichment factors of NH4+, nss-Ca2+and nss-Mg2+of rain in Fudan and Chongming were NH4+0.43/0.50, nss-Ca2+0.50/0.45, nss-Mg2+ 0.09/0.10, respectivrly. NH4+and Ca2+were the major alkaline cations, and showed the dominant neutralization effect over Mg2+. Correlation analysis showed the main forms of the atmospheric particles in Chongming were (NH4)SO4, NH4HSO4 and NH4NO3, while SO42-and NO3- were mainly in the form of CaSO4 and Ca(NO3)2 in the particles in Fudan.The total concentrations of organic acids (mainly included formate, acetic acid and oxalic acid) were 3.01 and 3.64μeq/L of rain in Fudan and Chongming, respectively. Formate and acetic acid mainly from plant emission, while oxalic acid may from the secondary organic aerosol.Source identification indicated that SO42-, NO3-, NF4+and most Ca2+derived from anthropogenic sources, Na+and most Cl- from the sea. Mg2+mainly originated from crust and sea in Fudan and Chongming, respectively. K+ originated from mineral and anthropogenic sources in Fudan, while derived from crust in Chongming. Of all the three sources of the rain in Fudan, the anthropogenic source dominated over the total ion concentrations followed by the marine and the crustal source, while the rain in Chongming was affected by anthropogenic source and sea.Back trajectory analysis implied that the precipitation in Chongming was mostly affected by air masses from sea, in which the air masses from Northwest, Southwest China and Yangtze River Delta might bring large amounts of anthropogenic pollutions through long- and moderate-range transport, which resulted the acid rain events at Chongming Dongtan.更多还原