The effects of exposure to heavy metals (HMs) in rice on human health have become a global public health concern, particularly in countries where rice is consumed as a staple food. The concentrations of HMs, including cadmium (Cd), arsenic (As), lead (Pb), and copper (Cu), in commercial rice samples (n = 170) were analyzed to estimate the HM exposure of consumers in Nepal. The geometric mean concentrations of Cd, As, Pb, and Cu in commercial rice were 15.5 ± 16.0, 43.4 ± 19.6, 16.0 ± 14.0, and 1066 ± 1210 μg/kg, respectively, all below the maximum allowable concentrations (MACs) recommended by FAO/WHO. Generally, the average estimated daily intakes (EDIs) of Cd, As, Pb, and Cu were all below the oral reference doses (RfDs). However, young age groups were exposed to high levels of HMs, and the average EDI of As and the P99.9 EDIs of Cu and Cd were above the corresponding RfDs. The mean hazard index and total carcinogenic risk were 1.13 and 1.04 × 10⁻³ respectively, suggesting a potential non-carcinogenic risk (NCR) and a carcinogenic risk (CR) via rice consumption. Arsenic contributed the most strongly to NCR and Cd to CR. Overall, although the HM levels in rice were generally safe, the Nepalese population may be exposed to an elevated health risk from rice consumption.

Rivers are an important mediator between human activities and the natural environment. They provide multiple functions, including irrigation, transportation, food supply, recreation, and water supply. Therefore, evaluations of water quality and pollution sources are of great significance for ecological restoration and management of rivers. In this study, the improved “vušekriterijumska optimizacija i kompromisno rješenje” (VIKOR in Serbian; in English: Multicriteria Optimization and Compromise Solution), and a geodetector were used to analyze the water quality characteristics and pollution sources of the Maotiao River Basin (Gizhou province, SW China). The results showed that the water quality of the Maotiao River Basin deteriorated significantly during the summer drought period, as was evident in the reservoirs and lakes. It improved in the wet season (i.e., during the summer period) due to runoff dilution. Water quality decreased along the river’s course, from upstream to downstream sections. The results of the geographic detector analysis showed that agricultural areas were the primary factor affecting the spatial distribution of water quality in the river basin. In July, August, and November 2020, the influence of agricultural land was 0.72, 0.60, or 0.80, respectively, and the interactions among urban, industrial, agricultural, and forested areas explained 99.2%, 83.2%, or 99.9% of the spatial differentiation of water quality, respectively. Due to the influence of spatial scale, settlements have a small influence on the spatial distribution of water quality. Their impact factors were 0.38, −0.24, and −0.05, respectively. Notably, the negative relationship of water quality and forested areas reflects that topography, types of landscapes, and soil thickness have considerable influences on the Maotiao River Basin’s water quality. Based on the findings, we infer that good farmland water conservancy projects and comprehensive management of different types of landscapes, such as forests, agriculture, and urban area and water bodies, are of great significance for improving water quality.

With the continuous improvement of surface water environmental quality in China, sediment has gradually become the focus of research on internal pollution in reservoirs. To investigate the forms, distribution, and migration patterns of phosphorus in karst canyon reservoir sediments, we employed an improved sequential graded extraction method to determine phosphorus content in the sediments of the Wanfeng Reservoir. We studied the spatial distribution characteristics and release risk of phosphorus form in the sediments. The results showed that the total phosphorus (TP) content ranged from 79.37 to 438.04 mg·kg⁻¹, while inorganic phosphorus (IP) content ranged from 77.32 to 424.64 mg·kg⁻¹. Iron–aluminum-bound inorganic phosphorus (Fe/Al-Pi) accounted for 36.41% and was found to be the dominant form of IP. Organic phosphorus (OP) content ranged from 1.84 to 13.59 mg·kg⁻¹, with weakly adsorbed organic phosphorus (H₂O-Po) being the dominant form of OP. Potentially active inorganic phosphorus (NaHCO₃-Pi) showed a highly significant positive correlation (p < 0.01) with Fe/Al-Pi, residual phosphorus (Res-P), and TP. This indicates that potentially active phosphorus (NaHCO₃-P) is a significant potential source of phosphorus (P) in the reservoir. Biologically active phosphorus (BAP) content ranged from 66.97 to 201.46 mg·kg⁻¹, with BAP/TP ratios ranging from 55.6% to 59.6%. The risk of phosphorus release from Wanfeng Reservoir sediments is high. The release of various forms of phosphorus from sediments is one of the important factors leading to the deterioration of water quality in the reservoir area in the future. To effectively manage water ecology in karst canyon reservoirs, it is essential to reduce the risk of endogenous phosphorus release.

This study investigated spring water in the core area and buffer zone of the Shibing Dolomite Karst World Heritage Site using one-year monthly monitoring, hydrochemistry, nitrate dual isotopes, and the MixSIAR model. The buffer zone spring exhibits shallow fissure-conduit flow with rapid hydrological response, anthropogenic nitrate dominance (>62%), nitrification as the main process, and limited denitrification. Its nitrate concentration shows seasonal peaks. In contrast, the core area spring is recharged by deep fissure water, with natural nitrate sources (>80%), stable nitrate levels (5–7.4 mg/L), and potential local denitrification. Nitrogen export in the buffer zone increases 4.5 times in the rainy season (NO₃⁻ accounting for 93% of TN). The core area shows higher TN export flux per unit area (3.34 vs. 0.4 g/m²/a) and greater DON proportion. Nitrogen export far exceeds that from rocky desertified areas, suggesting that dissolved nitrogen leaching drives karst rocky desertification evolution.