The alluvial plain in the middle and lower reaches of the Yellow River is an important agricultural production base that affects groundwater quality. Groundwater quality in the region is related to the residential and production uses of water by local residents. Samples of shallow groundwater and river water were collected from the right bank of the middle and lower reaches of the Yellow River to determine the evolution and causes of hydrochemical characteristics, and the relationship between the hydrochemical evolution of river water and groundwater was explored. The results showed that the shallow groundwater in the area received lateral recharge from the Yellow River water. The closer to the Yellow River the groundwater was, the higher the SO₄²⁻, Cl⁻, and Na⁺ concentrations and the lower the HCO₃⁻ and Mg²⁺ concentrations were. Agriculture and aquaculture has influenced and complicated the hydrochemical types of shallow groundwater in recent decades. The groundwater in the area was jointly affected by water–rock interactions and evaporation concentrations; a strong cation exchange effect was detected. Arsenic exceeded the limit in some shallow groundwater, which was mainly distributed in the Yellow River alluvial plain and caused by the reductive sedimentary environment of the Yellow River alluvial plain. The “three nitrogen”, NH₄⁺-N, NO₂⁻-N, and NO₃⁻-N, demonstrated sporadic local excesses in shallow groundwater, which were related to human activities, such as aquaculture.

This study focuses on energy consumption, carbon emissions, and productive land use. Adopting a carbon footprint methodology based on the ecological footprint framework, it accounts for the carbon ecological footprint and carbon carrying capacity of the nine provinces and regions in the Yellow River Basin from 2010 to 2021. By introducing indicators such as carbon deficit/surplus, carbon ecological footprint per 10,000 yuan GDP, and the Carbon Ecological Carrying Capacity Index (ECI), the study assesses the development of the regional carbon system and analyzes its level of sustainability. A carbon ecological footprint model for the nine provinces and regions was established to analyze temporal trends and spatiotemporal distribution patterns. Furthermore, the driving factors of the carbon ecological footprints were examined using the logarithmic mean Divisia index (LMDI) decomposition method. The results indicate that the per capita carbon ecological footprint in the nine provinces and regions remained relatively stable overall, though some provinces, such as the Inner Mongolia Autonomous Region, exhibited an upward trend. Qinghai Province and the Inner Mongolia Autonomous Region had the highest per capita carbon ecological footprints, while Henan and Sichuan Provinces were at comparatively lower levels. In terms of carbon carrying capacity, Shandong and Gansu Provinces showed the most significant increases in per capita carbon carrying capacity, whereas the Ningxia Hui Autonomous Region experienced a slight fluctuating decline. Most areas in Qinghai and Sichuan Provinces were in a state of carbon surplus, while the remaining regions were in carbon deficit. The carbon ecological footprint per 10,000 yuan GDP across the nine provinces and regions showed an overall decreasing trend, indicating improved efficiency in carbon resource utilization. The Carbon Sustainable Development Index (CSI) varied notably among provinces: Qinghai Province recorded the highest and most stable index; Sichuan Province ranked above Henan Province, which, despite a lower index, still demonstrated an overall upward trend.

1. Drought is a widespread and long-lasting climatic hazard that threatens agricultural production, ecosystems, and socioeconomic development. According to the processes affected, drought is common...