若尔盖草原泥炭柱中多环芳烃的沉积记录

SEDIMENTARY RECORD OF POLYCYCLIC AROMATIC HYDROCARBONS IN A PEAT CORE FROM THE ZOIGE PEAT BOG

通过^(210)Pb定年建立相应时间标尺,获得了若尔盖红原县泥炭柱中多环芳烃(PAHs)的含量和垂直分布特征。结果表明,泥炭中总PAHs的浓度为36.2～408ng/g dw,PAHs与泥炭TOC的含量具有较好的相关性。自20世纪初开始,PAHs浓度呈明显上升趋势,在1960年代初期达到峰值,其后开始下降。PAHs组成上主要以3～4环化合物为主,其中菲占总PAHs的45%,其次是荧蒽(16%)和芘(10%),体现出大气沉降来源的PAHs组成特征。PAHs成因判识指标表明,该地区泥炭中PAHs主要源自燃煤和汽车尾气排放;结合气流轨迹分析,我们认为四川盆地可能是其主要源区。泥炭中PAHs的浓度变化与泥炭TOC的含量、温度和降雨量有关。

A peat core recovered from the Zoige-Hongyuan peat bog was analyzed for polycyclic aromatic hydrocarbons （PAHs） to understand the origin and transportation of PAHs in the study area. The sedimentary sequence of PAHs was reconstructed using the ^210Pb activity method. The data indicate that the total concentration of 15 PAHs found from the peat samples ranges from 36.2ng/g to 408ng/g with the maximum concentration observed at a depth corresponding to the early 1960s. PAHs in the top of the core display the concentrations four times lower than the maximum. Phe is the most abundant PAHs,accounting for 45% of the total PAHs,followed by Flut（16%） and Pry （10%）. The other PAHs found from the peat core are less than 10%. Low molecular weight PAHs dominate the sedimentary sequence of PAHs, denoting a pathway of atmospheric transport and deposition input of PAHs into the peat bog. Based on analyses of historical air mass trajectories, we suggest that the Sichuan Basin to the southeast of the study area where air pollution is severe may be the source of the PAHs in the peat bog. Diagnostic ratios imply that the PAHs originated from coal and vehicle exhaust. PAHs started to increase in the concentration around the late 1910s with sharp increases occurring from the early 1940s to the early 1960s, and deceased afterwards. The increases in the PAH deposition would result from rapid industrializations accompanied by an extensive use of fossil fuels ; whereas the decreases could be attributed to the substitution of coal as a major energy source by natural gas, hydroelectric power or nuclear power, the decline of heavy industries and the effective measures to control the emission from fossil fuel combustions. TOC, air temperature and precipitation are inferred to be the major factors that control the concentration of PAHs deposited in the peat bog.