To study the sources and erosion process of sediments in the Lhasa River, a systematic analysis was conducted on the grain size, minerals, and geochemical characteristics of the sediments in the main stream of the Lhasa River, as well as its tributaries, Duilonqu River and the Wululongqu River. The results show that: the average particle size of sediments in the Lhasa River is coarser (65.45% sand and 23.64% silt), and the sorting is overall poor; the skewness is mostly positive, and the kurtosis is wide, which reflects the obvious characteristics of river sand sediment. The mineral composition of the Lhasa River sediments is dominated by quartz (38.4%), K-feldspar (27.11%), and plagioclase feldspar (23.64%), followed by clay minerals, and the content of carbonate minerals is relatively low. The illite content in the clay minerals is as high as 83.4%, and the chlorite content is slightly higher than the kaolinite content. Montmorillonite content is very low. The chemical index of illite is less than 0.4, indicating that illite is mainly rich in iron and magnesium. The value of the chemical weathering index (CIA) of the sediments is low, implying that the sediments are in a state of weak and moderate chemical weathering and are dominated by physical weathering. Additionally, the chemical weathering of the sediments in the Lhasa River is not only controlled by the dry and cold climate but also affected by the rapid erosion of extensively exposed granite.

Throughthe analysis of factors affecting the hydrochemical characteristics of various water bodies in the reservoir area of Taishan Pumped Storage Power Station in Shandong Province from 2009 to 2020, this study discussed the tracing function of hydrochemical characteristics variation in detecting the water leakage. The results showed that the reservoir water and groundwater of Taishan Pumped Storage Power Station are weakly alkaline, the hydrochemical types are mainly HCO₃-Ca, and some are HCO₃-SO₄-Ca, HCO₃-SO₄-Ca-Mg and SO₄-Ca-Mg, while the chemical types of surface water in Bashangou are SO₄-Ca and SO₄-Ca-Mg. The ion ratio analysis shows that the weathering of silicate rock is the main source of chemical ions in the reservoir water, the groundwater and the surface water of Bashangou. The surface water of Bashangou is controlled by the rock weathering and atmospheric precipitation at the same time, and the atmospheric precipitation without sufficient water-rock reaction is mixed in. The hydrochemical cluster analysis shows that the water samples of the drainage gallery on the right bank and the measuring weir behind the dam come from the leakage supply of the reservoir water, and the water sources of the measuring weir in the gallery at the bottom of the reservoir, the B2 high-pressure branch gallery, the NO.6 and No.1 construction adits are from the regional groundwater. The results of hydrochemical analysis are consistent with the results of hydrogen and oxygen isotope analysis of water body.

In order to clarify the sources and their seasonal variations of organic matter in surface sediment in the Three Gorges Reservoir region, the mass fractions of total organic carbon (TOC) and total nitrogen (TN) and their δ¹³C_org and δ¹⁵N isotopes in surface sediment samples from the mainstream and tributaries of the Three Gorges Reservoir region were measured in the summer and winter of 2017. The source ranges of organic matter were determined according to δ¹³C_org and the C/N ratio, with δ¹⁵N used for auxiliary analysis, and the Bayesian mixed model was used to quantify the contributions of different sources of organic matter in the Three Gorges Reservoir region. The results showed that the mass fractions of TOC and TN in surface sediment of the Three Gorges Reservoir region were 0.79% to 1.46% and 0.07% to 0.13%, respectively. The mass fraction of TOC in summer is slightly lower than that in winter, and that of TN has no seasonal difference. The ranges of δ¹³C_org and δ¹⁵N were -26.35‰ to -24.70‰ and 2.59‰ to 5.67‰, respectively, without seasonal difference. The organic matter of surface sediment in the Three Gorges Reservoir region mainly comes from soil organic matter and river plankton in summer, and soil organic matter and aquatic vascular plants dominate in winter. The proportion of sewage organic matter takes the fourth place in summer and winter, and further analysis with δ¹⁵N reveals that there is obvious external pollution in the Three Gorges Reservoir region, which is mainly related to artificial nitrogen fertilizer and domestic sewage, without obvious seasonal variation.