To explore strategies for the safe utilization of farmland co-contaminated with cadmium (Cd) and lead (Pb), this field study systematically evaluated the impacts of humic acid (HA) and potassium fulvate (PF) at different application rates (0, 1500, 3000, and 4500 kg·ha⁻¹) on the growth, yield, and translocation of Cd and Pb within the soil–plant system of maize (Zea mays L.). The results showed that while HA and PF did not significantly alter total soil Cd and Pb concentrations, they markedly reduced their bioavailable fractions. This mitigation of heavy metal phytotoxicity significantly promoted maize growth and yield, with the high-dose HA treatment increasing yield by a maximum of 32.9%. Both amendments dose-dependently decreased Cd and Pb concentrations, bioconcentration factors (BCF), and translocation factors (TF) in all maize tissues, particularly in the grains. At equivalent application rates, PF was slightly more effective than HA in reducing heavy metal concentrations in the grains. Notably, a significant positive correlation was observed between Cd and Pb concentrations across all plant parts, confirming a synergistic accumulation and translocation mechanism. This synergy provides a physiological explanation for the broad-spectrum immobilization efficacy of these humic substances. In conclusion, applying HA and PF presents a dual-benefit strategy for increasing yield and reducing risks in Cd- and Pb-contaminated farmlands. This study proposes a differentiated application approach: PF is the preferred option when ensuring food-grade safety is the primary goal, whereas high-dose HA is more advantageous for maximizing yield in soils with low-to-moderate contamination risk.

Cadmium (Cd) in contaminated soil not only enters surface water via rainfall runoff but also penetrates groundwater, adversely affecting human health through the food chain. This research examined three kinds of soil from Luoping County in southwestern China, with different Cd pollution levels. Simulated rainfall and soil column leaching experiments were conducted to explore the risks and factors influencing Cd loss in surface runoff and underground leaching water at different ground slopes (6°, 12°, 18°, and 24°), rainfall intensities (30, 60, and 90 mm∙h⁻¹), and soil profile conditions. The results show that the risk of soil Cd runoff loss increased at a higher rainfall intensity or Cd pollution degree, reaching a peak at a ground slope of 18°. The main factor affecting soil Cd runoff loss was rainfall intensity followed by Cd soil pollution degree and slope. The risk of soil Cd leaching loss was mainly determined by the leaching time and soil depth. The primary factor affecting soil Cd leaching loss was leaching time, followed by soil depth. The soil organic matter (SOM) concentration and pH minimally affected soil Cd loss. The research results provide a theoretical basis for risk management and control of cadmium loss in contaminated soil, and indicate that the environment-friendly water treatment method of high concentration Cd polluted runoff deserves attention.

Potentially toxic element (PTE) co-contamination in farmland severely threatens global food safety. To identify effective remediation strategies, large-scale field trials were conducted in two karst regions of Southwest China highly co-contaminated with Cd, Pb, As, Cr, and Hg. The efficacy of seven commercial soil amendments (biochar (BC), fused calcium–magnesium phosphate (FCMP), humic acid (HA), potassium humate (KH), oyster shell powder (OS), composite passivator (PA), and quicklime (QL)) on soil physicochemical properties, PTE bioavailability, maize (Zea mays L.) yield, and plant tissue distribution was systematically evaluated. The results indicated that organic amendments, specifically BC, HA, and KH, consistently outperformed inorganic treatments. These organic materials significantly decreased the diethylenetriaminepentaacetic acid (DTPA)-extractable fractions of cationic PTEs (e.g., Cd and Pb decreased by up to 39.5% under KH treatment) without inadvertently mobilizing As, unlike the alkaline inorganic amendments. This reduction in soil bioavailability closely correlated with improved plant performance, leading to maximum increases in root biomass (up to 130% with BC) and grain yield (up to 27.6% with HA). Furthermore, BC and humic substances effectively restricted PTE accumulation in grains (Cd and Pb reduced by up to 42.1%). Tissue distribution analysis revealed a consistently low root-to-stem translocation factor (TF < 0.2), indicating that roots acted as the primary sink for absorbed PTEs. This study indicates that commercial organic amendments support the use of a superior, broad-spectrum strategy for mitigating multi-PTE risks and ensuring safe agricultural utilization in severely co-contaminated areas.

The plateau transition zone in the upper reaches of the Yangtze River serves as a critical ecological barrier for the river basin. Non-point source pollution driven by nitrogen and phosphorus inputs represents the core regulatory priority of water environmental protection in this region. Nitrogen (N) and phosphorus (P) inputs from agricultural production are the core targets of non-point source pollution prevention and control in this region. Taking Chuxiong Yi Autonomous Prefecture as the study area, this study quantitatively analyzed the spatiotemporal evolution characteristics and source composition of anthropogenic N and P inputs from 2009 to 2023, based on the Net Anthropogenic Nitrogen Input (NANI) and Net Anthropogenic Phosphorus Input (NAPI) models. The dominant driving factors of N and P inputs were identified using the Random Forest model, and the evolution trends of N and P inputs under chemical fertilizer reduction and population change scenarios were predicted via the multiple linear regression (MLR) model. The results showed that the average values of NANI and NAPI in Chuxiong Prefecture from 2009 to 2023 were (7419.3 ± 651.5) kg·km⁻²·year⁻¹ and (1768 ± 190) kg·km⁻²·year⁻¹, respectively, with an overall upward trend. The spatial distribution exhibited high heterogeneity: high values were concentrated in the central basin areas, while low values were distributed in mountainous areas. Food N input and chemical fertilizer application were the primary sources of NANI and NAPI in the study area, accounting for 51.91% and 62.85% on average, respectively. Population density, livestock and poultry breeding scale, and chemical fertilizer application rate were the key driving factors of N and P inputs. Scenario prediction results indicated that both chemical fertilizer reduction and population decline would lead to a significant decrease in N and P inputs. Overall, N and P inputs in Chuxiong Prefecture are dominated by anthropogenic activities, and their spatiotemporal differentiation is closely related to agricultural activity intensity and population distribution. Improving N and P use efficiency is the key to precise prevention and control of N and P pollution in the region.