湖北省金罗家考古遗址土壤中多环芳烃的分布和植硅体的分析及其意义

Distribution of polycyclic aromatic hydrocarbons and phytolith analysis of archaeological soil of Jinluojia site in Hubei province

湖北金罗家遗址剖面总厚度为171 cm,平均10 cm采集一个样品,共采集17个样品。考古遗址年代顺序主要根据考古器物（如陶片、瓷片、砖瓦块等）颜色、图案、花纹和形态类型等与已确定年代的考古器物特征进行对比分析,进而确定不同文化层的时代顺序。文章对考古土壤中多环芳烃的分布、植硅体类型和炭屑进行了研究,并对多环芳烃可能来源、植硅体组合和炭屑及其意义进行了分析。结果显示,在最下部的生土层样品未检测到多环芳烃,古文化层土壤样品均检测出了多环芳烃,不同文化层土壤中的多环芳烃的分布特征也是不同的,在个别文化层土壤中的多环芳烃还表现出一些异常。利用多环芳烃来源地球化学参数甲基菲/菲（MPh/Ph）和荧蒽/芘（Fl/Py）的比值对金罗家遗址考古遗址土壤中的多环芳烃的来源进行了初步判断,考古土壤多环芳烃的MPh/Ph值范围主要在0.34~0.89之间（除F13样品值为1.30外）,Fl/Py值范围主要在1.92~5.88之间（除F8样品值为10.82外）,说明多环芳烃的来源主要是热成因。而荧蒽/菲、苯并蒽/菲和苯并芘/菲等可以作为与陆生植物和化石燃料的燃烧有关芳烃的产物的标志,这些多环芳烃可能与人类活动有一定的关系,说明考古遗址土壤中的多环芳烃记录能够反映生活在该遗址上一些人类社会经济发展和活动的信息。因此,多环芳烃是人类活动的良好指示物。同时,在整个剖面土壤中还检测出大量的且种类多样的植硅体和炭屑,植硅体类型主要有：方型、长方型、扇型、哑铃型、鞍型、齿型、帽型、棒型和尖型等。植硅体组合能够恢复当地的古植被,也可以反映古人类在选择和利用植物有关的生活和生产活动。其古植被生长是与古气候变化相适应的,在西周时期文化层,以C3植物为主;东周时期文化层,以C4植物为主;唐宋时期文化层,以C3植物为主,明清时期文化层,以C4植物为主。炭屑是植物有机体不完全燃烧的产物,炭屑分析是研究历史上人类活动的方法之一。在金罗家遗址样品炭屑分析中,从不同古文化堆积层的变化背景中分离出了因人口增长或火灾造成的2个炭屑高峰值,第一个峰值为东周时期,另一峰值为明清时期,这两个峰值与自西周（1 000 BC）以来历史记载的该地区2个人口繁盛和经济发达时间基本相符。在对考古土壤中的多环芳烃、木本型植硅体和炭屑对比分析中,它们的变化规律存在着较好的一致性。这些说明生活在遗址的人类利用和改造自然环境的时候,自然环境也可能影响着人类社会的发展。

Hubei province is one of Chu culture origins and ancient culture cradles in the maddle of the Yangtze river.Jinluojia site is 20 km southwest from Jinluojia Village,Songbu Town,Macheng County of Hubei province,with culture layer thickness from 13cm to 59 cm.The total thickness of sampling profile in the west wall of 2005MJTG1 Jinluojia site is 171 cm.The profile is divided into out six layers according to the color and character of the deposit from top to bottom.Archaeological ware typologic information,such as pottery remnants,porcelain and tile shards,have provided a time sequence for the site with confirming age sequence.Sam-ples for lipid analysis were taken by the following method： First,the outer layer of the earth was discarded.The inside part was then sampled by grooving the revealing profile from bottom to top a 5 cm interval.Seventeen samples were collected with their weights ranging from 500 g to 1000 g.Samples were dried in the open air immediately,after being ground to 100 meshes approximately 120 g of each sample.In this study,the distribution pattern of polycyclic aromatic hydrocarbons（PAHs） and phytolith analysis were in-vestigated.The origin of PAHs,the significance of phytolith assemblages,and charcoal scraps were analyzed.The results showed that PAHs could be identified in every ancient cultural layer,with their distribution pattern varying while ancient cultural layers vary.The content of PAHs in soils of several ancient cultural layers displays distinct anomaly.Most soil samples from Jiuluojia archaeo-logical site show a MPh/P value ranging from 0.34 to 0.89,inferring a dominance of pyrogenic origin for the PAHs identified from the soil.The Fl/Py ratio for all the soil samples analyzed ranges from 1.92 to 10.82,suggesting a combustion origin.According to the geochemical parameters of PAHs,the fluoranthene/phenanthrene,pyrene/phenanthrene and benzofluoranthene/phenanthrene ratios indicate that PAHs in soils of ancient cultural layers were mainly of combustion origin,which were produced by the combustion of woods and other higher plants in the ancient human＇s activities and production.Therefore,PAHs can be viewed as a good indicator of human activities.The abundant and various phytolith types and charcoal remnants were observed.Most phytoliths were square-shape,long-square shape,fan-shape,dumbbell,saddle,trapezoid,rondel,elongate types and point-shape,and so on.Phyto-lith assemblages could resume the paleoecological environment and reflect the life and productive activities of the ancients.The phytoliths analysis shows the paleoclimate have been warm and wet in Xizhou and early Dongzhou Dynasty.It might have become cool and dry in late Dongzhou Dynasty,warm and wet in Tang-Song Dynasty and cool and dry with climate fluctuations in Ming-Qing Dynasty.Paleovegetations might have changed along with paleoclimate changes which in different culture layer in ar-chaeological site.C3 plants were dominant in Xizhou,which C4 plants were more abundant than C3 plants in Dongzhou.The main vegetations were C3 plants in Tang-Song period,while in Ming-Qing C4 plants dominated.The charcoal fragment analysis is one of the methods for studying the historical human activities.Two charcoal fragment peak values were recognized in this study which were interpreted to be due to population growth or fire disaster.