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Understanding the spatial and temporal variations of CO2 column concentration (CO2-CCs) is crucial for tackling climate change and promoting sustainable human development. This study provides an in-depth analysis of CO2 dynamics in the Yellow River Basin, an area significantly affected by both natural and anthropogenic factors. Using data from the Orbiting Carbon Observatory 2 (OCO-2) and the Fourier transformation spectrometer (FTS) of the GOSAT satellite remote sensing sensors, supplemented with ground station data from the Waliguan station, we scrutinized the CO2 levels in the region from 2013 to 2022. The regional CO2-CC displayed a 12-month cyclical variation and a continuous upward trend, escalating by approximately 4.26% over the 10-year period. Spatiotemporal differences were evident in the monthly variation of CO2-CC, with peak and minimum values occurring in May and August respectively. Geographically, the highest CO2-CC was found in the central part of the basin, while the lowest was in the northern part of Inner Mongolia. This study underscores the increased significance of the region's CO2-CC, which showed an increase from 17.0 ppm at the start of the period to 21.0 ppm by the end, representing an overall growth of between 4.35 and 5.25%. The findings highlight the urgency of targeted measures to mitigate CO2 emissions and adapt to their consequences in the Yellow River Basin, contributing to the global efforts against climate change and towards sustainable development. [ABSTRACT FROM AUTHOR]

Hulun Lake is located in the Hulun Buir Grassland in Inner Mongolia and is an important component of the northern ecological barrier of China. Fluctuations in its area directly affect the stability of the surrounding ecological environments. In this study, Hulun Lake was taken as the study object, and meteorological data, water body area, water level, reservoir capacity, runoff volume, and social statistical data were used to study the dynamic changes in Hulun Lake and the critical driving forces. We constructed a balance analysis equation, determined the role of groundwater in the water cycle, and examined the minimum ecological water demand of Hulun Lake. The results of the analyses revealed that during the last 55 years, the variation trends of the water level, area, and reservoir capacity were generally consistent and could be divided into six stages. The increased temperature decreased precipitation, and increased evaporation resulted in decreased water flow from the major rivers supplying the lake, which was the main cause of the decrease in the water level and area of Hulun Lake. Groundwater was involved in the water cycle of Hulun Lake. After deducting the seepage and surface drainage, we found that the groundwater recharge volume was around 792 million m3 yearly. Based on the environmental, ecological, and production functions of Hulun Lake, the minimum ecological water demand is 11.272 billion m3. [ABSTRACT FROM AUTHOR]

Lakes are important water resources in Inner Mongolia and play essential roles in flood storage, water source maintenance, aquaculture, water volume regulation, and the regional ecological balance. However, most lakes in Inner Mongolia have undergone significant shrinkage over the past few decades. In order to quantify the lake changes in Inner Mongolia and analyze the factors associated with these changes, information about 546 lakes in seven years (1990, 1995, 2000, 2005, 2010, 2015, and 2018) was retrieved using 30 m resolution Landsat images taken of the entire region over 29 years (1989–2018). In addition, water census data from 2010 and 1:250,000 geological maps were used as references. The analysis revealed that the lakes in Inner Mongolia exhibited rapidly decreasing trends during the past three decades, with both the area and the number of lakes decreasing to a minimum by 2010. The number of lakes with areas of >1 km2 decreased from 384 in 1990 to 301 in 2018; the total area of lakes with individual areas of >1 km2 decreased from 4905.74 km2 in 1990 to 4187.45 km2 in 2018. With respect to the lake distribution among different geomorphological units, the analysis revealed that the lake shrinkage was most pronounced on the West Liaohe Plain, followed by the northern Inner Mongolian Plateau. Furthermore, in relation to different climatic zones, lake shrinkage primarily occurred in the mid-temperate semi-arid zone, wherein the lake area decreased by 776.6 km2. We hypothesize that the changes in the lake number and area in Inner Mongolia resulted from the combined effects of natural conditions and anthropogenic disturbances; possibly, lake shrinkage was mainly driven by the rising temperature and decreasing precipitation, along with water regulation projects, agricultural irrigation, mining development, and population growth that also had non-negligible effects on the lakes. [ABSTRACT FROM AUTHOR]