泥炭记录的晚全新世大气铅沉降及其环境意义

Atmospheric Lead Deposition Recorded in Two Types of Mires and Its Implication for Palaeoenvironment from Dunhua Basin,Jilin Province in China

选择长白山地区2种不同类型的泥炭沼泽,进行了典型剖面的大气铅沉降研究。植物残体和泥炭性质表明老白山泥炭地已经发育到贫营养阶段,而大桥泥炭地还处于富营养状态。两地泥炭记录的总铅含量和沉降速率与中国其他地区在同一个数量级上。老白山泥炭记录的大气铅在总铅中占主导地位,大气铅与富集因子呈明显的正相关(r=0.874,n=16,p<0.01),且在16世纪中叶、18世纪初和20世纪出现峰值。大桥泥炭记录的铅可能存在再迁移和再沉降现象,但是相对较弱,因此,它也可以被用来重建当时的大气沉降。

Two peat profiles respectively form Laobaishan mire （44° 06′N, 128° 03′E） and Daqiao mire （43° 17′N, 128° 22′E） from Changbai Mountains in northeast China, were investigated to reconstruct atmospheric de-position since 2120 B.P., and decide whether Pb inventories in minerotrophic mires are mobile. The plant mac-rofossil types and characteristics of peat samples indicate Laobaishan mire has developed into ombrotrophic bog, and Daqiao mire is still in minerotrophic status. The largest concentration, accumulation rates of Pb in Laobaishan and Daqiao are 22.23-38.46 ug/g and 8.8-16.33 mg/（m2？y） respectively, and are in the same order of magnitude as the other places in the world. A positive correlation between lithogenic Pb and ash content （r=0.799,n=16,p〈0.01） in Laobaishan profile indicate lithogenic Pb mainly from rock weathering underlying peat deposits. Atmospheric Pb is dominant in total Pb deposition that suggests cumulative Pb is most from atmo-spheric deposition. High enrichment factors of Pb in Laobaishan profile occurred in the middle of 16th century, the early of 18th century and 20th century. They are in good agreement with little ice age during the middle of sixteen centuries, volcano eruption happened in Changbai Mountains in 1702 and human activities in the 20th century. Pb content and accumulation rate recorded in Daqiao mires are the most value in the downmost layer. This corresponds with atmospheric soil dust flux very well. Moreover, the Pb enrichment factor is the greatest at the subsurface.