新疆洛浦县比孜里墓地出土彩棺的科学研究

Scientific Research of Colored Coffin Excavated from Bizili Cemetery in Luopu County of Xinjiang,China

比孜里墓地的发掘,是近年来塔里木盆地南缘一处重要的考古发现,进一步丰富了昆仑山北麓及丝绸之路南道考古资料。利用加速器质谱碳十四(AMS-^14C)测年、扫描电镜能谱(SEM-EDS)、拉曼光谱(RS)及热辅助水解甲基化-裂解气相色谱/质谱(THM-Py-GC/MS)分析技术,对来自新疆洛浦县比孜里墓地中惟一一口彩棺进行了检测分析。碳十四(AMS-^14C)年代测定结果距今年代为(1520±25)B.P,由此判断该彩棺年代为南北朝时期,与考古判断年代相一致。蓝色颜料通过采用四甲基氢氧化铵(TMAH)存在下的热辅助水解甲基化(THM)技术检测出了靛蓝(C16H10O2N2)的特征热裂解产物2-氨基苯甲酸甲酯和2-甲氨基苯甲酸甲酯,从而确定了有机染料靛蓝在绘画中的应用,彩棺所用颜料除植物染料靛蓝外,其余均为新疆地区常见的一些矿物颜料,主要有:石膏CaSO4(白色),铁红Fe2O3(红色),炭黑C(黑色),所含胶结材料主要有干性油、蛋白质类胶合物-鸡蛋清,另外还检测出了安息香树脂。这些信息的检出不仅进一步完善了该彩棺的基本信息,而且对彩棺后期的进一步研究、修缮以及保护提供了重要依据;通过THM-Py-GC/MS分析技术对彩棺所用蓝色颜料及胶结材料进行分析,表明Py-GC/MS相比气相色谱-质谱联用(GC-MS)技术不仅具有灵敏度高,样品用量少,操作方便简单,无需对样品进行复杂的前处理等优点,而且通过热辅助水解和甲基化(THM)反应,将羧基和羟基甲基化,使极性大的分子转化为极性较小的分子,从而进一步提高色谱的分离效果。因此,THM-Py-GC/MS分析技术在快速鉴别文物中天然有机材料方面具有很大的潜力。

The excavation of bizili cemetery is an important archaeological discovery in the southern margin of the Tarim Basin in recent years.Which further enriches the archaeological materials at the northern foot of Kunlun Mountain and the south of the silk road.This paper presents the study of the colored coffin from bizili cemetery in Luopu County of Xinjiang,China.The techniques applied include Carbon-14 accelerator mass spectrometry(AMS-^14C),Scanning electron microscope and energy spectrometer(SEM-EDS),Raman spectroscopy and Thermally assisted hydrolysis and methylation(THM)-Pyrolysis Gas Chromatography and Mass Spectrometry(Py-GC/MS).The results show that the colored coffin dates back to the northern and southern dynasties of ancient china[(1520±25)B.P];Characteristic markers of indigo 2-Amino-benzoic acid,methyl ester and 2-(methylamino)-benzoic acid,methyl ester were detected by Thermally assisted hydrolysis and methylation(THM)in the presence of tetramethylammonium hydroxide(TMAH),which shows blue colour was made with plant dye indigo C16H10O2N2.In addition to the plant dye indigo,the other pigments used in colored coffin are some common mineral pigments in Xinjiang,mainly includes:Gypsum(CaSO4,white),iron oxide red(Fe2O3,red),carbon black(C,black);Drying oil,protein-egg white and Gum Benzoin were determined as binding media in the colored painting.The detection of this information not only further improves the basic information of the colored coffin,but also plays an important supporting role in the further research,repair and protection of the colored coffin in the future.In addition,the analysis of blue pigment and binding medium by THM-Py-GC/MS showed that Py-GC/MS has the advantages of high sensitivity,structure information can be obtained from very small amounts of samples without any preliminary processing,and it is also easy to operate compared with gas chromatography-mass spectrometry(GC-MS).Moreover,carboxyl group and hydroxyl group were methylated by THM-Py-GC/MS with TMAH.The higher polar molecules were translated into low polarity molecules,which increased the volatility of pyrolysis products and further improved the chromatographic separation effect.Therefore,THM-Py-GC/MS has great potential in rapid identification of natural organic materials in cultural relics.