大气颗粒物中溴和碘的物种及形成机理

Atmospheric bromine cycling is important due to its well-known ozone depletion capabilities.Iodine speciation in aerosols is thought to control the recycling behaviour of iodine between the particle and gas phase and may also influence climate through new aerosol formation.Field observations have increasingly found very little iodate and significant amounts of iodide and soluble organically bound iodine(SOI) in aerosols. Aerosol samples will be taken with a 8 stage cascade impactor and a virtual impactor (PM10,PM2.5) from the different regions,such as near the coast area,rice paddies area,dry land area and heavily polluted city,and all samples are analysed for total iodine and bromine,and tatal soluble iodine and bromine by inductively coupled plasma mass spectrometry (ICP-MS) and iodine and bromine speciation are determined by coupling an ion chromatography unit to the ICP-MS.Modes of bromine and iodine occurrence in aerosols,such as,water-soluble,ion exchangeable,carbonate,Fe-Mn oxides,organic fraction and residue,were investigated by using sequential chemical extraction. The aim of this study is to investigate iodine and bromine speciation,including the organic fraction,in aerosols from different station above,in an attempt to further clarify which iodine and bromine speciation is significant amounts in different region aerosols.Correlations between SOI and I-1,and Efs in aerosols near the coast area are calculated,during the day and during the night,in an attempt to futher clarify the mechanism of iodine cycling. In order to explain the source of Br and I in aerosols, the enrichment factors (EFs) are calculated by considering Na,Al and K.

大气环境中溴循环对臭氧的损耗有重要影响，碘物种可通过形成新气溶胶粒子而影响气候变化。在近海岸地区的场地观测发现，颗粒物中碘酸盐的含量很低，而碘化物和有机碘的含量较丰富。为此，本研究拟采集近海岸地区、水淹田地区、旱地地区和重污染城市地区中大气颗粒物样品（包括分级样品、PM10和PM2.5样品）；以微波消解ICP-MS测定颗粒物中元素Br和I，运用逐级化学提取法研究大气颗粒物中Br和I的赋存状态，包括水溶态、离子交换态、碳酸盐结合态、铁锰氧化物结合态、有机结合态和残留态，以IC-ICP-MS测定颗粒物中水溶态Br和I物种（碘的物种:I-,IO3-和SOI等）。着重观测不同地区大气颗粒物中Br和I物种及形态的分布规律，获取总有机溴、碘的数据；研究近海岸地区昼夜间碘物种中溶解性有机碘与碘离子的相关性以及富集因子的差异；计算Br和I的富集因子，研究Br和I的来源（海洋源、矿物尘和生物质源）。

建立了UHPLC-ICPMS在线测定溴碘砷物种的分析方法。该方法分离时间短、线性关系好、检出限低、加标回收率高和精密度高。可应用于环境等样品中溴碘物种的痕量分析，实现了快速分离和准确测定，5分钟可完成样品的准确测定。.分别采集了中国中东部地区11个城市的降雪样品、上海市雨季中颗粒物样品和降雨样品和上海市雾霾季节的颗粒物样品。测定了雪样中的约23种元素、10种离子和溴碘砷的物种；测定了颗粒物样品和雨水样品中的溴碘等约20种元素、12种离子和有机碳等。.在大气颗粒物和降雪样品中，溴碘砷的有机物种含量大于无机物种含量，有机物种含量大于50%，且在无机物种中，低价态物种远高于高价态物种。大气颗粒物和降雪样品中地壳元素含量远大于污染元素含量，污染元素主要来源于化石燃料燃烧、交通污染和工业排放；在空间和时间上，溴碘砷等约20元素的总浓度与时间上和空间上的AQI具有很高的相关性，相关系数大于0.9，环境介质中元素含量反映当地污染程度的结论。在上海的雨季，溴碘砷等约20元素和12种离子的浓度均为雨中低于雨前和雨后，与降雨量及AQI等都有很高的相关性，采样期间，各元素的湿沉降通量约占总沉降通量（干沉降通量+湿沉降通量）的8-70%的结论。在上海雾霾季节，上海市大气颗粒物中OC在细颗粒物中的总质量浓度均稍高于粗颗粒物中的总质量浓度，IC在细颗粒物中总质量浓度与在粗颗粒物中总质量浓度相当。.在国家大气环境质量国控点——上海师大站点，我们已积累了不同大气介质中元素、离子和物种形态等的一年半的数据，希望积累三年的数据。特别是在该国控点，实时发布空气质量的数据，这些数据与大气介质中元素、离子和物种形态等数据进行关联，进行分析，这是一件很有意义的事情和工作，应该有有意义的发现。