A synthesis of published and newly acquired stable and radiocarbon isotope data from soil, river, and marine particulate organic carbon (OC) from the South China Sea drainage and sedimentary basin reveals that OC derived from bedrock‐erosion (petrogenic OC) and marine productivity comprises the major contributors to bulk OC in particulate matter reaching abyssal depths, while soil‐derived OC appears negligible. Aluminum‐radiocarbon relationships of sediments suggest that soil OC initially associated with detrital terrestrial minerals is lost and replaced by marine OC during transport beyond the continental shelf. We estimate that petrogenic OC sinking to a ~30,000 km2 region of the deep northeastern South China Sea accounts for 0.6% of global petrogenic OC burial. The basin‐wide OC isotope patterns coupled with sediment trap observations highlight both the spatial variabilities of OC components as they propagate from source to sedimentary sink and the significance of petrogenic OC to deep ocean sediments.

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Cracking of wall surface crusts on salt-laden earthen remains at the site of Yar City, northwest China, is a serious concern. This widespread pathology is closely related to the drying shrinkage behavior of soil and the fundamental mechanisms should be investigated to better interpret the deterioration of these precious heritages. In this paper, tests were conducted on specimens that were initially slurries with NaCl contents of 0%, 2%, and 5%. The soil shrinkage characteristic curve (SSCC) was measured using the fluid displacement method during a slow air-drying process. The drying branch of the soil-water retention curve was also established by combining three common techniques (pressure plate, vapor equilibrium, and filter paper). The microstructure of specimens with varying water and NaCl contents was characterized through mercury intrusion porosimetry (MIP) testing. Results show that NaCl had negligible impact on the SSCC, which was composed of three shrinkage zones. With increasing NaCl content, matric suction was hardly influenced while the total suction increased significantly due to the pore fluid osmotic suction. The analysis indicated that drying shrinkage was actually a process of consolidation governed predominantly by matric suction. MIP test results were consistent with the macroscale observations for specimens that were initially slurries: that the total volume of pores decreased upon drying. In addition, pore-size distribution was unimodal and no significant difference was observed among specimens with different NaCl contents.

Sandstone grottoes, with their elaborate carvings and decorations, hold high historic, artistic and scientific values and therefore constitute an important part of China’s stone cultural heritage. Although capillary water accounts for severe pathologies at the grottoes, so far there have been limited comprehensive investigations concerned with the capillary water absorption behavior of sandstones. Aiming at three significant and famous sites in China, i.e., Yungang Grottoes (YG), Dazu Rock Carvings (DZ) and Leshan Grand Buddha (LS), capillary water absorption tests were performed on samples from local sandstones. During the test, evolution of cumulative inflow was measured and variation in the height of capillary rise over time was also monitored by combining visual observation and infrared thermography. Scanning electron microscope and mercury intrusion porosimetry were adopted to characterize the pore structure. The results indicate that all the tested sandstones had a medium capacity of water uptake. Kinetics for capillary water absorption was the highest for LS sandstone and the lowest for DZ sandstone. Differences in macroscopic properties were contributed to microstructural features such as average pore diameter and pore size distribution. An irregular shaped water front was only observed in LS sandstone due to its heterogeneity. Infrared thermography provides an efficient and nondestructive way to detect the transition zone between wet and dry portions of the sample, which was not visible to the naked eyes. A proper understanding of the interaction of the sandstones with capillary water is essential for revealing the deterioration of grottoes and the underlying mechanisms.

The Yungang Grottoes, with over 1500 years of history, have been subjected to air pollution since the last century. Field investigations have indicated that acid gases, particularly sulfur dioxide (SO2), have accumulated on the surface of the sculptures and caused various types of decay that reduce their artistic value. To shed new light on the gas–stone interaction process, artificially accelerated weathering was performed on local sandstone in the laboratory. In a specially developed test device, fresh specimens were exposed to gaseous SO2 under different relative humidity and temperature conditions. The physical, mineralogical, and chemical changes of Yungang sandstone were evaluated conjointly using destructive and non-destructive methods. The results show that after weathering, the luminosity of all specimens changed, with a slight alteration in hue toward yellow. The weight increased to various degrees during the aging cycles, which depended on both the accumulation of matter and the detachment of particles. Higher relative humidity and cyclic temperature fluctuations favored the dissolution of carbonates and the hydrolysis of feldspar in sandstone. The concentration of ions, especially dissolved Ca2+ and SO42-, increased considerably over time in the near-surface region of the specimens. A trace of newly formed gypsum was detected in some specimens at the end of the test. Knowing the synergistic impact of different climatic variables will make it possible to identify the mechanisms of the deterioration of sandstone in complex environments.