Sedimentary deposits preserve geological evidence of past environmental change. During fieldwork in April 2022, we investigated and systematically sampled a well-exposed sedimentary section near Baituzhuang Village, Hualong Hui Autonomous County, Qinghai Province, in the upper Yellow River Basin of northwestern China. The section was analyzed using optically stimulated luminescence (OSL) dating, grain-size analysis, soil-color measurements, loss on ignition (LOI), and elemental geochemical analysis to determine the age and depositional characteristics of the Baituzhuang mudflow deposit and to assess its relationship with abrupt climate change during the last deglaciation. OSL ages indicate that the layer was deposited at 14–13 kyr BP, coinciding with a major climatic transition during the last deglaciation. The grain-size distribution of the Baituzhuang mudflow deposit (MFD) layer differs markedly from those of the overlying and underlying strata. The MFD layer contains a pronounced peak in sand content, a feature consistent with mudflow deposition. The soil-color data support an aqueous depositional origin for the MFD layer. In addition, LOI and elemental geochemical data show pronounced fluctuations within the MFD layer, indicating the input of exogenous material transported by the mudflow. The evidence indicates that the mudflow occurred during an abrupt transition from cold-arid to warm-humid conditions. Our results refine the reconstruction of environmental evolution in the study area since the last deglaciation. They further indicate that the mudflow event represents a rapid hydrogeomorphic response to abrupt climate change in the Upper Yellow River region, within the transitional zone between the Qinghai-Tibet Plateau and the Loess Plateau. This event provides local evidence for the sensitivity of the Upper Yellow River landscape to abrupt climatic change during the last deglaciation.
Soil erosion in hilly and gully areas of the Loess Plateau has attracted considerable attention in recent decades. However, the understanding of soil redistribution in the desert-loess critical zone, where wind and water erosion interact, remains limited. Plutonium (Pu) isotopes have received growing interest in environmental level assessments and as tracers because of their distinct geochemical characteristics and ideal tracer properties. In this study, eight soil profiles representing different land use types were collected from Jingbian County. The activity concentrations of 239+240Pu and 240Pu/239Pu atom ratios in soil samples were determined using inductively coupled plasma mass spectrometry. The soil redistribution rates under different land use patterns were assessed using Pu isotopes as tracers, and the vertical distribution of 239+240Pu activity concentration was analyzed. Additionally, the migration behavior of Pu isotopes across temporal scales was modeled using the Convection-Dispersion Equation (CDE) model. The results show the 240Pu/239Pu atom ratios (0.166–0.202) indicate that the global fallout from atmospheric nuclear weapons testing is the primary source of Pu in the study area. The 239+240Pu activity concentrations ranging from 0.002 to 0.470 mBq/g, consist with background values in China. The CDE model predictions indicate that the distribution of Pu isotopes in soil profiles will become increasingly uniform over the next 100–200 yr. Based on the Pu tracing model, the estimated soil redistribution rates vary from −3.87 to 39.74 t/(ha·yr), where positive values indicate net erosion and negative values indicate net sedimentation. Soil erosion rates follow the order: planted woodland (1.71 t/(ha·yr)) < sunflower field (28.19 t/(ha·yr)) < cornfield (29.69 t/(ha·yr)). Severe erosion occurred predominantly in cultivated areas with low vegetation cover and high elevations. In contrast, grassland and woodland were more effective in soil and water retention, mitigating erosion intensity. These findings improve the understanding of Pu isotopes behavior and soil redistribution processes in the desert-loess critical zone and provide a scientific basis for optimizing land use patterns. In practice, expanding grassland and woodland are effective measures for soil and water conservation.
Agricultural tillage-emitted atmospheric particulate matter (PM) substantially impacts aerosol loading, with cascading effects on climate, environment, and human health. However, rural aerosol characteristics and agricultural PM emission magnitudes remain unclear across distinct agricultural regions. To determine the spatio-temporal variations and driving factors of rural aerosols, this study conducted a three-month field measurement at six monitoring sites in Northeast China in 2018, differing in crop system, farming practices, and soil type. Key data included real-time PM2.5 and PM10 concentrations, daily ambient PM2.5 samples analyzed for chemical compositions (ions, elements, and carbonaceous fractions), and vertical aerosol extinction profiles. Results revealed significant spatial heterogeneity in tillage-period PM2.5 concentrations (80–237) µg/m3, with dryland-dominated regions exhibiting the highest levels (up to (237 ± 189) µg/m3) and paddy-concentrated areas the lowest (80 ± 16) µg/m3. These spatial differences were primarily driven by meteorological conditions and tillage practices, with low humidity (∼ 10
Carex tussock wetlands, as a unique herbaceous swamp ecosystem, play a crucial ecological role in maintaining wetland ecosystem stability, biodiversity, and carbon sequestration. However, in recent years, the degradation of Carex tussock wetlands has become increasingly evident, but research on their natural degradation process under hydrological stress remains limited. This study focuses on the degradation of Carex tussock wetlands and their response patterns to hydrological conditions, using the Momoge National Nature Reserve (Jilin Province, China) as the research site. By comparing the soil physicochemical properties and morphological characteristics of degraded and non-degraded tussocks, and simulating hydrological conditions using the Mike21 hydrodynamic model, the key hydrological factors influencing the degradation of Carex tussock wetlands and their ecological response mechanisms were explored. The results showed that the severely degraded tussock areas had the lowest elevation ((135.93 ± 0.03) m), while the lightly degraded tussock areas ((136.21 ± 0.06) m) had a slightly lower elevation than the non-degraded tussock areas ((136.36 ± 0.11) m). This indicates that degraded tussock areas experienced longer flooding durations. Morphological characteristics indicated that with increasing degradation degree, tussocks gradually became shorter and smaller, and their shapes tended to become increasingly irregular. Soil physicochemical property analysis indicated that with increasing degradation degree, the contents of soil total phosphorus (TP), soil organic carbon (SOC), total nitrogen (TN), and total carbon (TC) generally showed a decreasing trend, reflecting a loss of soil carbon and nitrogen pools. However, no significant differences were observed between lightly degraded and non-degraded tussock areas. Analysis of the impact of hydrological conditions on tussock communities reveals that both flooding conditions and flow velocity significantly affect degraded and non-degraded tussock communities, with flooding depth and duration being the key hydrological factors influencing the degradation of Carex tussock wetlands. Prolonged inundation exerts detrimental effects on tussock biomass, resulting in diminished tussock stature and structural integrity, ultimately driving tussock degradation. Concurrently, flow scouring plays a dual role in both shaping tussock morphological characteristics and accelerating degradation processes through synergistic interactions with inundation stress. Additionally, the ecological feedback of degraded tussocks further exacerbate Carex wetland degradation. This study provides a theoretical basis for the protection and restoration of Carex tussock wetlands, particularly in terms of hydrological regulation strategies, offering significant practical implications.
As a key component of regional eco-hydrological processes and the terrestrial water balance, evapotranspiration (ET) plays a crucial role in regional water resources management. In this study, the spatiotemporal dynamics of ET in the Madu River Basin (MRB), an important watershed of the Three Gorges Reservoir region in China, were simulated and analyzed for the period 1981–2018 using the Soil and Water Assessment Tool (SWAT) model, together with scenario analysis, Mann-Kendall (MK) trend test, and multiple regression analysis. Results showed that: 1) the SWAT model demonstrated satisfactory performance in multi-site calibration, with Nash-Sutcliffe efficiency (NSE) and R2 values exceeding 0.80, confirming the suitability of the Moderate Resolution Imaging Spectrora-diometer (MODIS) ET dataset (MOD16A2) for SWAT calibration at the sub-basin scale. Compared with ET observations from the eddy covariance (EC) system, the ET simulation yielded R2 and NSE values of 0.82 and 0.61, respectively, verifying the reliability of the SWAT model for the MRB. 2) Mean annual ET showed a significant increasing trend (2.0 mm/yr) from 1981 to 2018, with a basin-wide mean of 642.6 mm/yr. The long-term mean values and change trends of ET before and after 2001 exhibited different patterns: the longterm mean value increased from 615.9 mm/yr before 2001 to 675.6 mm/yr after 2001; the decreasing trend (−0.0097 mm/yr) before 2001 reversed to an increasing trend (0.0025 mm/yr) after 2001. 3) Higher ET values were generally observed in sub-basins with higher elevations and fewer canyon landforms, whereas downstream areas showed comparatively smaller temporal fluctuations. ET decreased with increasing slope gradient and varied according to soil type. Multi-year mean annual ET among different land-use types followed the order: water > forest > grassland > cropland > built-up area. 4) ET was positively correlated with both air temperature and precipitation, while demonstrating an ‘evaporation paradox’ in October and a significant response to reduced precipitation. Seasonal variation and vegetation phenology jointly modulate the effects of land use on ET patterns, with cropland ET exceeding forest ET from August to December and surpassing grassland ET in winter. This study presents a practical approach for ET estimation and provides new insights into the relationships between environmental factors and the spatial and temporal distribution of ET.
