In this research, we attempted to identify the specific sources of the organic binding media from the Terra-cotta Army of Emperor Qinshihuang. Gas chromatography-mass spectrometry (GC-MS) was used to analyze the organic matter extracted from the pigment layer and the result shows that the main components were fatty acids and their oxidation products. Further identification using gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) obtained the Δ¹³C values of stearic acid and palmitic acid, which were similar to those of ruminants. Combined with the literature, it was speculated that the bovine glue was used as the binding media for the pigments of the Terracotta Army. After the introduction of supercritical fluid extraction (SFE) and total lipid extraction (TLE), the extraction effects of the same sample were compared between different extraction methods. The result shows that the extraction efficiency was significantly improved to capture additional components via SFE, compared with the conventional chemical-reagent extraction method. Featuring the advantages of streamlined process, short time consumption and less chemical pollution, SFE could possibly perform better for the extraction for precious archaeological materials. The successful application of fatty acid stable isotopic analysis (FASIA) to the pigment binding media on the Terra-cotta Army of Qinshihuang indicates that it is an effective measure and will have great potentials in the studies of archaeological organic residues in the future.

The stable sulfur isotope ratio of human (animal) bone collagen can be used not only to distinguish differences in individual food sources, but also to judge their migratory behaviors. Stable sulfur isotopic analysis has become more and more important with the development of bioarchaeology. Previously, its application was not common because the extremely low content of sulfur in collagen (there was no suitable standard material with low sulfur content for accurate testing), requirement of a large sample size for testing, and memory effects made the test more complicated. Failure of the accurate determination of sulfur content and its isotope ratio has been a limitation for the research on isotopic bioarchaeology. In recent years, a newly developed mass spectrometry (MS) technology has been able to determine the sulfur isotope ratio of bone collagen with a small sample size, but the difficulty in determining the sulfur content due to the lack of a low-sulfur content standard substance still exists. At present, we have not yet seen any reports on the methods specific to sulfur content and isotopic testing for archaeological bone collagen. In this study, we used an elemental analysis-isotope ratio mass spectrometry (EA-IRMS) with programmed ramping gas chromatograph (GC) for the determination of sulfur content and isotope values of collagen. Our instrumental parameter settings and testing procedure are provided in the text. Firstly, we used sulfanilamide and pasta reference material (PRM, 0.14% sulfur content) as standard substances for sulfur content determination. The standard curve established by PRM with different gradient masses was used to calibrate the international standard samples (USGS89 and USGS42) with a margin of error of lower than 0.1%, and a standard deviation of the sulfur content of the archaeological collagen samples within 0.02%. Then, we used the sulfur isotope values of the international standard samples (IAEA-S-1 and IAEA-S-2) to establish a linear regression curve by the two-point method, and corrected USGS42, whose δ³⁴S was available. The accuracy of the corrected δ³⁴S obtained was better than 0.3‰. Finally, we tested archaeological bone collagen samples and combined various factors, such as signal strength, sample mass, and instrument stability, and determined that stable isotope values obtained could be more accurate and stable when using a mass of 5 200-5 800 μg of collagen samples, with a standard deviation of δ³⁴S of lower than 0.4‰. Compared with the existing stable sulfur isotopic testing methods for collagen from various institutions around the world, the analytical method we established for the sulfur content and isotope ratio of bone collagen is also in the leading position. The application of this method in China will greatly promote the development of stable isotopic bioarchaeology, making sulfur isotopic analysis become one of the routine methods for isotopic analysis in the field of archaeology. This method is expected to better reveal the food structure and migratory behavior of ancient humans (animals) in China, and to explore important scientific and archaeological issues.

Fumigation is currently a widely used method for rapid control of insect and mold diseases in cultural relics, but it also has problems such as weak desorption and easy secondary damage to cultural relics caused by residues. Focusing on three commonly used organic fumigants, this study has established a volatility detectionsystem based on the photo-ionization detection method. Using the Fick’s law, a prediction model for the volatilization rate of fumigants per unit area was established to accurately detect the residual amounts of fumigants. The results indicate that there was a good linear relationship between the mass fraction of organic fumigants and the sensor output value. The use of photo-particle sensors of the photo-ionization detector (PID) had good detection sensitivities for three organic fumigants—citronellal, citral and citronellol, with values of 2.072,1.287 and 0.702 V/(mg/L), respectively. The calculation results of the residue volatilization rate calculation model derived from the Fick’s law show that the correlation coefficient R² between the measured and predicted volatilization rates of the three organic fumigants was close to 1, and the significant difference P value approached 0. This model could be used accurately for the calculation of residue volatilization rates. In addition, it was found that under environmental conditions of 22℃, 60% (RH) and normal atmospheric pressure, and after complete fumigation of rice paper, the residual amounts of citral, citronellol and citronellal approached 0.1,0.06 and 0.01 ng/mm² after 5 hours of desorption, and all the residual amounts approached 0 ng/mm² after 72 hours of desorption. Therefore, the PID sensor and residue volatilization rate calculation model proposed by this study could accurately detect the residual amount and volatilization rate of fumigants used for paper cultural relics in practical applications, providing important new technical support and safety protection for the detection work for the fumigation and disinfection of paper cultural relics.

In this study:silk fabrics of the Southern Song Dynasty and the Warring States Period were selected as the investigated objects; modern silk was taken as reference. The microscopic structure of the samples was observed by scanning electron microscopy, and thermogravimetric analysis was performed based on the principle of thermal analysis kinetics. The kinetic parameters of silk were calculated by applying Flynn-Wall-Ozawa, Kissinger-Akahira-Sunose and Kissinger models, and the relevant thermodynamic parameters were obtained. In this study, the thermal analysis kinetic method was introduced into the study of degradation of silk cultural relics, and the differences of the kinetic and thermodynamic parameters between modern silk and ancient silk were investigated. The thermal stability, degradation state and chemical properties of silk cultural relics were determined by the characteristic scale of activation energy, activation enthalpy and activation Gibbs free energy. This study has reference value for revealing the degradation mechanism and evaluating the degree of degradation of silk cultural relics, and also provides theoretical guidance for predicting the duration life of silk cultural relics.