Geothermal resources are the vital renewable energy for resolving energy crisis and environmental deterioration. Understanding hydrogeochemical processes, genesis mechanisms and scaling trends is crucial for securing the sustainable utilization of geothermal resources. In this study, fourteen geothermal waters were collected for hydrochemical and δ²H–δ¹⁸O isotopic analyses in northwestern Sichuan, SW China to clarify hydrogeochemical processes, genesis mechanisms, and scaling trends. Geothermal waters were recharged via atmospheric precipitation. Three different types of geothermal waters were identified using a piper diagram. Class 1 geothermal water with HCO₃–Na and HCO₃–SO₄–Na types formed in the contact zone with Yanshanian intrusions and heated by residual radioactive heat. The hydrochemical processes were sodium/potassium silicate dissolution and positive cation–exchange. Class 2 geothermal water with HCO₃–Ca and HCO₃–Ca–Mg type was carbonate–type and heated by geothermal gradient. The dissolution of carbonate minerals dominated the hydrochemical process. Class 3 geothermal water with the SO₄–Ca–Mg type was determined within deep faults. The dissolution of carbonatite and gypsum minerals and the oxidation of sulfides played a vital role in the hydrochemical process. The reservoir temperatures of geothermal waters followed the orders of Class 1 (74.9–137.6 °C) > Class 3 (85.9–100 °C) > Class 2 (38.7–93.5 °C). Calcium carbonate scaling should be paid attention to in Class1 and Class 3 geothermal water, and calcium sulfate scaling merely occurs in Class 3 geothermal water. This study provides vital information for geothermal exploitation in western Sichuan and other similar areas.

Soil environmental protection has become a pressing issue for sustainable development. This study collected 153 topsoil samples from a typical agricultural area to evaluate the contamination characteristics of heavy metal(loid)s (HMs), identify their potential sources, and assess the associated ecological and human health risks. The results showed that the mean concentration of HMs was in the order of Zn > Cr > Ni > Pb > Cu > As > Cd > Hg; all HMs were below their background levels, except Cd. The geo-accumulation index (Igeo) and improved Nemerow index (INI) revealed that the overall pollution level was considered as no or slight contamination, while HMs posed low ecological risk according to the ecological hazard factor (E_i) and potential ecological risk index (PERI). In addition, three main sources were identified through the positive matrix factorization (PMF) model: natural source (48.2%; contributed As, Ni, Cu, Pb, and Zn), coal burning and waste disposal (24%; contributed Hg and Cd), and agricultural activities (27.8%; contributed Cr). The human health risk (HHR) assessment model and Monte Carlo simulation were applied to evaluate human health risks, and the results suggested that children faced higher health risks than adults, with 45.83% of samples exceeding the non-carcinogenic acceptable limit. As and Cr were the main contributors to non-carcinogenic and carcinogenic risks, respectively. The findings contributed to the local environmental management and sustainable development of agriculture.

Potentially toxic element (PTE) contamination in topsoil poses non-negligible risks to both the ecological environment and public safety. This study integrated multiple methods to conduct geochemical analyses and assess the presence of PTEs in topsoils of an urban area. The findings show that the average concentrations of PTEs were as follows: 8.21 mg/kg for As, 0.23 mg/kg for Cd, 92.26 mg/kg for Cr, 0.22 mg/kg for Hg, 35.99 mg/kg for Pb, 37.83 mg/kg for Cu, 42.85 mg/kg for Ni, and 111.99 mg/kg for Zn. Zn exhibited the highest mean concentration among PTEs in the topsoil, followed by Cr and Ni, while all PTEs exceeded their background levels. Utilizing the positive matrix factorization (PMF) model, four distinct sources of PTEs were quantitatively determined: F1, representing industrial emissions, had the highest contribution rate (30.73%) and mainly provided Cr and Ni; F2, representing agricultural activities, ranked second with a contribution rate of 23.31%. The Nemerow geo-accumulation index (NI) varied between 0.26 and 2.07 (mean = 0.73), with over 88% of the samples classified as slightly polluted; the potential ecological risk index (PERI) was in the range of 119.98–511.07 (mean = 158.95), with more than 95% classified within the low-to-moderate ecological risk range; and the soil environmental capacity index (PI) ranged from 0.47 to 1.40, with an average value of 1.0. These results suggest that the pollution level of and potential ecological risk posed by PTEs are low overall, reflecting a robust soil carrying capacity and minimal adverse effects on the ecosystem. In addition, the hazards of PTEs to public health were quantified based on the human health risk assessment framework. The potential health risks posed by PTEs fell into the acceptable range for both children and adults. Notably, elevated risk values were predominantly observed in the southern portion of the study area, with arsenic (As) being the principal contributor.