Changes of air environmental factors in Zengpiyan cave site and its influence on the cultural layers
The Zengpiyan cave site is a significant Neolithic cave site in Southern China,yielding complete human skeletal fossils as well as artifacts related to the diet and tools of ancient human inhabitants. This cave site provides essential evidence for understanding human activities in Southern China between 12,000 and 7,000 years ago. The cave system at the site consists of three distinct areas:the main cave,the water cave,and the low cave. The main cave retains an intact original cultural layer,featuring clear stratigraphic sequences. Cultural layers,representing the area where artifacts are preserved within the cave site,embody the most important cultural content of the site. Previous research on karst caves has shown that temperature,relative humidity,and carbon dioxide (CO2) concentrations inside the cave exhibit markedly different temporal and spatial variations compared to the outside environment. These factors influence the formation and degradation of carbonate deposits such as stalactites.To understand the temporal and spatial variations of air environmental factors within the Zengpiyan cave site and their influence on the weathering of cultural layers,this study acts as a crucial supplement and extension to the environmental research on the Zengpiyan cave site,with a particular emphasis on the microenvironment of the cultural layers of the cave. The study specifically examines environmental factors such as cave temperature,relative humidity,and CO2 concentrations. A hydrological year-long observation was conducted in Zengpiyan cave with the use of various air monitoring devices,along with the sampling and analysis of cultural layer deposits from different excavation units.The results reveal that the air environmental factors inside the cave exhibit three distinct seasonal stages:in winter,both temperature and humidity are low with large fluctuations,and CO2 does not accumulate at the cave floor. In contrast,summer,brings high temperature and humidity with small and stable variations,resulting in CO2 accumulation at the cave floor. Spring and autumn serve as transitional phases between winter and summer. Spatially,temperature and humidity show a gradual variation with the increase of cave depth. CO2 concentrations exhibited a banded distribution with high-concentrations in the eastern section of the cave,suggesting that the water cave plays a significantly role in evevating the CO2 levels within the main cave. The primary source of CO2 in the cave is the overlying soil,with rainfall events identified as critical triggers for peak CO2 levels within the cave. A comprehensive analysis suggests that ventilation effects are the main factors influencing the temporal and spatial variations of air within the cave. Additionally,cave morphology and tourism activities are also recognized as significant contributors to the air environment within the cave. Observing and combining X-ray diffraction analysis,it was found that there are significant differences in the degree of weathering of cultural layers near the entrance of the cave,water cave connections,cave middle sections,cave bottoms,and the upper and lower parts of the exploration area,which are related to the spatiotemporal changes of air environmental factors. For example,there are more dissolution cavities in the upper cultural layer at the cave floor,mainly due to the accumulation of water vapor in the upper part,which condenses and dissolves,transporting easily soluble components away from the cultural layer. In contrast,the cultural layer at the cave entrance is characterized by loose and powdery cementation,which is associated with the significant temperature fluctuations and frequent cycles of drying and wetting at the entrance.This study has documented the temporal and spatial variations of the main air environmental factors at the Zengpiyan cave site,which is characterized by a shallow,wide-open entrance. It has also explored the potential influencing factors and their impact on the weathering of cultural layers. These findings provide a scientific basis for the improved preservation and utilization of cave sites.
cave sitesair environmentweathering of cultural layerCO2Zengpiyan
万方数据
维普
