摘要
2009年8月至2010年7月在东亚季风区中纬度城市北京连续一年以每周3天的时间尺度同步采集近地面大气中气溶胶样品并测定了宇宙射线成因核素7Be和8种有机氯农药(OCPs)、7种多氯联苯(PCBs)的浓度。7Be浓度全年平均值为(8.39±0.49)mBq/m3,显著高于欧洲地区具有相同纬度的城市。最高值出现在9月(15.64 mBq/m3),最低值出现在5月(1.35 mBq/m3)。夏季7Be浓度值较低,春、秋季浓度值较高。对大气气溶胶中7Be进行不同季风时节的比较要比季节性的比较可更好地揭示7Be的变化规律及其来源。夏季的低值与东南季风导致的多降雨气象条件有关。秋季的高值为大气环流异常所致。OCPs和PCBs总浓度(∑OCPs和∑PCBs)呈现夏季低,秋、冬季高的现象。西风和西北风为北京市大气气溶胶中POPs浓度最高的季风时节。较高氯代PCBs(PCB153和PCB180)在冬季占主导优势。较高的PCB101和PCB118可能来自北京周边的污染源。在部分时期7Be与DDTs和δ-HCH有显著的相关性,而在春季和夏季PCB-101与7Be有很好的相关性。
Near-surface atmospheric aerosols were collected at sampling frequency of 3 d per week for one year from August 2009 to July 2010 in Beijing, which is located in the mid-latitude region of the East Asia monsoon region. The samples were analyzed for cosmogenic nuclide 7Be, eight organochlorine pesticides （OCPs）, and seven polychlorinated biphenyls （PCBs）. The annual average 7Be concentration was （8.39±0.49） mBq/m^3, with variations of 1.35 to 15.64 mBq/m^3, significantly higher than the average level in Europeancities at the same latitude. The maximum and minimum levels were observed in September and May, respectively. Autumn and spring were the seasons with high 7Be concentrations and summer and winter were the lower 7Be seasons. Comparisons of 7Be concentrations based on different monsoon phases can better reveal the variation patterns and source regions of 7Be than those based on seasonal comparisons. Enhannced wet precipitation may have caused lower 7Be oberseved in summer when southeasterly was prevailing. Higher 7Be concentrations in autumn than the annual mean is due to the abnormal atmospheric circulation in autumn 2009. Concentrations of HCHs, DDTs, PCBs followed a trend of being lower in summer and higher in autumn and winter, suggesting westerly and northwesterly can bring POPs residue to Beijing area. Higher chlorinated PCBs （PCB-153 and PCB-180） were predominant in winter. Higher PCB-101 and PCB-118 may have come from sourounding emission sources. Significant correlations were observed between the monthly average∑HCHs,∑DDTs, and∑PCBs and significant correlations of 7Be with DDTs andδ-HCH were found in some particular sampling periods.
出处
《地球化学》
CAS
CSCD
2014年第2期101-113,共13页
Geochimica
基金
国家自然科学基金(41073011
41003044
40773010)
