Nanling County, situated on the southern bank of the Yangtze River’s middle and lower reaches in China, and has not yet carried out hydrogeochemical geological surveys. This study is pivotal in ensuring the reliability of the drinking water supply, particularly during emergencies. Utilizing an array of analytical methods—statistical analysis, Shularev classification, Piper trilinear diagram, Gibbs diagram, ion ratio method, and mineral saturation index—this research elucidates the hydrogeochemical characteristics and principal water–salt interactions in Nanling’s shallow groundwater. Our findings, derived from the Shularev classification and Piper trilinear diagram, reveal that, in the southern mountainous and river valley plain regions, the primary hydrogeochemical type of groundwater is HCO₃-Ca. Conversely, in the northern area of Sanli Town and the adjoining plain, groundwater predominantly falls under the HCO₃-Na•Ca category, with some regions showing the characteristics of HCO₃•Cl-Ca, HCO₃•Cl-Na•Ca, and, occasionally, HCO₃•SO₄-Na•Ca. According to the Gibbs diagram analysis, the predominant source of groundwater in this region is attributed to water–rock dissolution processes occurring during groundwater runoff. The increase in Na⁺, Ca²⁺, Cl⁻, HCO₃⁻, and SO₄²⁻ concentrations in the water–rock interaction in the study area is mainly due to the dissolution of rock salt, gypsum, calcite, and dolomite, and the alternating cation adsorption occurs during the reaction. Finally, the mineral saturation index points to the ongoing dissolution of gypsum, calcite, and dolomite, until a state of precipitation–dissolution equilibrium is reached. This comprehensive study provides vital insights into the hydrogeochemical dynamics of Nanling County’s groundwater, contributing significantly to our understanding of regional water quality and its management.

The enrichment law of heavy metals and pollution assessment in the soil-crop system have become the focus of research on environmental pollution issues. Evaluating the co-pollution risk of heavy metals in the soil-crop system of the Nanyang Basin is of great significance for food safety and the governance of regional heavy metal environmental pollution. This study collected 5778 surface soil samples, 185 wheat samples, 75 corn samples, 114 peanut samples, and 374 corresponding root soil samples from each crop in the Nanyang Basin. The concentrations of arsenic (As), cadmium (Cd), chromium (Cr), mercury (Hg), and lead (Pb) were measured. The pollution index and potential ecological risk assessment methods were utilized to assess the pollution of heavy metals in the soil. The bioconcentration factor (BCF) method was employed to analyze the metal transfer dynamics. The synergistic risk of heavy metals in the soil-crop system was assessed utilizing the soil-crop comprehensive quality index (IICQ). The results revealed that most of the study areas had low levels of soil pollution, with unpolluted and lightly polluted areas predominating. The crops of wheat, corn and peanuts in the study area are generally at a safe level, with the crop pollution index less than 1, while the crop pollution index at some other points is greater than 1. Wheat, peanuts, and corn showed strong bioaccumulation capacity for Cd, with peanuts exhibiting the highest accumulation ability. The largest proportion of sampling points was categorized under unpolluted soil and crops, with peanuts being the most affected crop.

Molybdenum (Mo) is an essential plant micronutrient, and legumes may accumulate relatively high Mo because of their greater physiological demand. Field evidence for species-specific Mo transfer in naturally Mo-enriched soils remains limited. Rhizosphere soil and edible seeds/grains were collected from 18 peanut and 19 wheat fields in Xichuan County, Henan Province, China. Soil total and available Mo, grain Mo concentrations, bioaccumulation factors (BCFs), dietary intake, and target hazard quotients (THQs) were evaluated. Soil total Mo ranged from 0.58 to 6.09 mg/kg and available Mo from 0.08 to 0.88 mg/kg. Peanut seeds contained about 8-fold more Mo than wheat grains (3.36 vs. 0.40 mg/kg) and had higher BCFs (0.32–7.95 vs. 0.05–1.29). Path analysis identified total soil Mo as the dominant predictor of available Mo, while peanut seed Mo showed no significant direct association with available Mo but was strongly associated with soil pH. The maximum soil Mo geoaccumulation index (Igeo) was 2.82 (Class 3). All THQs were below 1 under national-average consumption, whereas a hypothetical high-consumption peanut scenario yielded a THQ of 2.37. These findings highlight contrasting soil-to-grain Mo relationships between the two cropping systems and the need for crop-specific dietary risk assessment.