No abstract

No abstract

No abstract

Understanding the impact of climate change on runoff is essential for effective water resource management and planning. In this study, the regional climate model (RCM) RegCM4.5 was used to dynamically downscale near-future climate projections from two global climate models to a 50-km horizontal resolution over the upper reaches of the Yangtze River (UYRB). Based on the bias-corrected climate projection results, the impacts of climate change on mid-twenty-first century precipitation and temperature in the UYRB were assessed. Then, through the coupling of a large-scale hydrological model with RegCM4.5, the impacts of climate change on river flows at the outlets of the UYRB were assessed. According to the projections, the eastern UYRB will tend to be warm-dry in the near-future relative to the reference period, whereas the western UYRB will tend to be warm-humid. Precipitation will decreases at a rate of 19.05–19.25 mm/10 a, and the multiyear average annual precipitation will vary between − 0.5 and 0.5 mm/day. Temperature is projected to increases significantly at a rate of 0.38–0.52 °C/10 a, and the projected multiyear average air temperature increase is approximately 1.3–1.5 ℃. The contribution of snowmelt runoff to the annual runoff in the UYBR is only approximately 4%, whereas that to the spring runoff is approximately 9.2%. Affected by climate warming, the annual average snowmelt runoff in the basin will be reduced by 36–39%, whereas the total annual runoff will be reduced by 4.1–5%, and the extreme runoff will be slightly reduced. Areas of projected decreased runoff depth are mainly concentrated in the southeast region of the basin. The decrease in precipitation is driving this decrease in the southeast, whereas the decreased runoff depth in the northwest is mainly driven by the increase in evaporation.

Concentrations of potentially toxic metals including Cd, Cu, Pb, Cr, U, Th in surface water and sediment samples collected from a river were analyzed to assess the contaminations, distribution characteristics, and sources of these metals. The contents of the metals were lower than the standard levels set by World Health Organization (WHO) for drinking water. However, U and Th contents were far beyond the background values of surface water. The concentrations of Cd, Cr, and U in sediments were higher than the background values and the Probable Effect Level (PEL) of sediment quality guidelines (SQGs) which may result in high potential harmful biological effects to aquatic ecosystems. Based on the contamination factor (CF), geo-accumulation index (Igeo), and potential ecological risk index (RI), Cd, Cr, and U were considered to be the metals that mainly contribute to the contamination of sediments. The calculation results also indicated that the sites adjacent to the uranium ore field were highly polluted. Results of cluster analysis, principal component analysis, and correlation analysis revealed that Cr, Pb, U, and Th were highly correlated with each other. These metals mainly originated from both anthropogenic sources and natural processes, especially emissions from uranium mining and quarrying, whereas Cd mostly came from anthropogenic sources (agricultural activities) of the upper reaches of the river.

rock composition and assessment of melting processes and age of crystallization. The combination of such analyses will contribute to geochemical or thermomechanical modeling that will constrain mantle origin and melting processes leading to the formation of these basalts.

By choosing exogenous Chlorella vulgaris and native Chlorella vulgaris which were screened from karst areas as study objects, and making comparison of the utilization of Ca 2? and HCO 3 -in typical karst water by Chlorella vulgaris of two different origins in a closed system, the relationship between Chlorella vulgaris cell numbers and the utilization rate of Ca 2? and HCO 3 -and the pH value change are studied. The results show that the native Chlorella vulgaris have higher Ca 2? and HCO 3 -use ratio than exogenous Chlorella vulgaris, while exogenous Chlorella vulgaris utilized more Ca 2? than native Chlorella vulgaris, but utilized the same amount of HCO 3-. In addition, exogenous Chlorella vulgaris can form CaCO 3 -rich sediment in the form of extracellular crystal, but native Chlorella vulgaris cannot. Furthermore, the pH value change in the closed system revealed that both algae utilized the dissolved carbon dioxide as photosynthetic carbon source and made use of HCO 3 -. Exogenous Chlorella vulgaris can absorb 26.3 % Ca 2? and 29.6 % HCO 3 -of the karst water, and native Chlorella vulgaris makes use of 42.1 % Ca 2? and 40.6 % HCO 3 -. As a primary producer in the food chain, the two kinds of aquatic algae transform HCO 3 -into organic matter and take them into the ecological system which shows the net carbon sink effect.

No abstract