The large-scale dredging of lake sediments generates substantial sludge, presenting both environmental challenges and opportunities for agricultural reuse. This study evaluated the effects of blended sediment on crop growth and soil heavy metal safety using sediments from Gehu Lake, China. A field experiment employing a rice-wheat rotation compared three treatments: a control (CK, no sediment), raw sediment (Sed), and blended sediment (B-Sed: 90% sediment, 5% compost, and 5% river sand), all applied at 60 t ha-1. The blended sediment significantly enhanced crop performance: Wheat and rice yields increased by similar to 26% and 52% compared with CK, without elevating grain sterility. Both sediment treatments improved soil quality, elevating soil organic matter (by 17% in Sed and 61% in B-Sed), nutrient availability, and soil structure. Concentrations of heavy metals (Cd, Pb, As, Hg, Cu, Ni, Zn, and Cr) in soils and grains remained below China's national safety standards (GB 15618-2018, GB 2762-2022). Risk assessments confirmed low environmental ecological risk. A USEPA-model-based health risk assessment indicated that the total hazard index (THI) and total carcinogenic risk (TCR) for both adults and children were within acceptable limits, with the B-Sed treatment posing the lowest risk. In conclusion, blended dredged sediment effectively enhanced soil fertility and crop yields in a rice-wheat enhance soil fertility and crop yields, supporting its sustainable reuse in agriculture.
This innovative waste management strategy examines a triad mixture of laterite soil (LS), peat soil (PS), and rice husk (RH) for managing heavy metal migration in landfill daily covers. Heavy metal contamination in groundwater presents significant environmental challenges in Malaysia, highlighting the need for effective remediation. The research evaluates the LS-PS-RH mixture's ability to mitigate leachate generation and reduce metal contamination. Laboratory assessments, including surface physical morphology and adsorption tests, were performed to determine the mixture's effectiveness. Using Central Composite Design (CCD) for optimization, optimal conditions for maximum heavy metal removal at an initial concentration of 5.76 mg/L were identified. Validation experiments confirmed the model's predictions, with error ranges of 0.54%-4.74%. Although Ni removal showed a slightly higher error at 6.75%, the model remains valid. The 50LS:40PS:10RH mixture demonstrates promise as a sustainable solution for landfill daily covers, effectively controlling heavy metal migration and ensuring environmental protection.
This study numerically investigates the three-dimensional flow characteristics within a hybrid spur dike field to evaluate how alternating impermeable (I) and pile (P) spur dikes influence channel hydraulics and sediment transport potential. Using ANSYS Fluent with the standard k - epsilon model, six geometric configurations (each maintaining identical first and last impermeable spur dikes) and three discharges were simulated to analyze the effects of permeability ratio and spatial arrangement on internal circulation and velocity distribution. Results show that impermeable spur-dike field systems generate a single compact recirculation cell extending over approximately 4-5 m, with near-bank velocity reductions exceeding 70%, leading to strong stagnation and sediment-deposition potential. In contrast, hybrid configurations (particularly the balanced 3I-2P and fully hybridized 4I-3P layouts) develop multiple smaller vortices that enhance shear-layer instability and fluid exchange between the main flow and the inner zone. The 4I-3P configuration achieved the most favorable hydraulic performance, shortening the reattachment length to 3.3 m (50% reduction relative to the impermeable case) and increasing near-bank velocities to 0.12-0.15 m s-1. These results indicate a 40%-65% improvement in momentum redistribution and a 60% reduction in stagnation area compared to impermeable layouts. Overall, the findings demonstrate that an equal or well-distributed combination of impermeable and pile spur dikes provides the optimal balance between flow conveyance and morphological stability. The proposed hybrid system offers a hydraulically efficient and sustainable approach for enhancing flood-carrying capacity and reducing sediment accumulation in long river reaches.
Cropland is a significant source of nitric oxide (NO) in rural areas. We extracted field measurement data from peer-reviewed publications and conducted a pairwise meta-analysis, with major objectives (1) to quantify the variations of NO emissions and direct emission factors (EFds) across Chinese cropland, and (2) to evaluate the impacts of various mitigation strategies on NO emissions and EFds. Cropping systems included paddy rice-winter wheat, vegetables, maize-winter wheat, orchards, and tea plantations. The dataset comprised 650 and 427 records of NO emissions and EFds, respectively, from 71 publications (2006-2026). Mean seasonal NO emissions were 0.49, 2.23, and 1.71 kg N ha-1 for paddy rice, winter wheat, and vegetables, respectively. Mean annual NO emissions were 1.33, 1.78, and 5.89 kg N ha-1 for maize-winter wheat, orchards, and tea plantations, respectively. Mean EFds were 0.16%, 0.70%, 0.79%, 0.31%, 0.17%, and 1.47% for paddy rice, winter wheat, vegetables, maize-winter wheat, orchards, and tea plantations, respectively. Tea plantations and vegetable systems were identified as major sources of NO emissions. Reducing nitrogen input rates significantly decreased NO emissions by 33% on average, but had nonsignificant effects on EFds. Organic amendments, straw retention, and the application of biochar or enhanced-efficiency fertilizers reduced NO emissions (ranging from -37% to -16%) and EFds (ranging from -49% to -13%). These findings provide a basis for effectively mitigating NO emissions from Chinese cropland.
Toxic elements (arsenic, cadmium, lead, and mercury) are public health concerns and listed as priority pollutants for their severe toxic effects, especially in children, whose biological systems are developing. The aim of this study was to determine the concentrations of toxic elements (As, Cd, Pb, and Hg) in plastic utensils using x-ray fluorescence and specific migration tests. The utensils were cleaned with an Extran detergent and analyzed using a portable XRF analyzer. Specific migration tests were conducted using water and 3% acetic acid as food simulants under two test conditions: rapid (2 h at 40 degrees C) and long (10 days at 25 degrees C), followed by inductively coupled plasma mass spectrometry analysis. A total of 54 utensils were analyzed, revealing mean concentrations of Cd, Pb, As, and Hg of 20.9, 31.3, 10.4, and 14.45 mg kg-1, respectively. Alarmingly, Cd, Hg, and Pb exceeded specific migration limits on the rapid tests by factors of 18.6, 34.5, and 5027, respectively, whereas Hg and Pb exceeded limits on the long tests by factors of 2 and 22, respectively. Statistical analyses confirmed significant associations between utensil type/color and element concentrations. The high levels of toxic elements found underscore the urgent need for coordinated action to protect health and ensure food and environmental safety.
