Objective To investigate the causes of the abnormally elevated gross α and gross β activity concentrations in the water of Nanbei Lake located near the Qinshan Nuclear Power Plant. Methods Water and sediment samples were measured according to GB/T 5750.13-2023 Standard Examination Methods for Drinking Water. Results The gross α activity concentration in Nanbei Lake water was (0.135 ± 0.0108) Bq/L, and the gross β activity concentration was 0.345 ± 0.036 Bq/L, which were several times higher than those recorded during the same period in previous years. The spike recovery rates for Nanbei Lake water (gross α: 85.7% ± 4.7%; gross β: 101.8% ± 4.1%) showed no significant differences from those for tap water (gross α: 83.2% ± 3.6%; gross β: 105.1% ± 5.2%). Gross α activity concentration exhibited a positive correlation with sediment addition (r = 0.996), as did gross β activity concentration (r = 0.998). The gross α and gross β activity concentrations in sediments from Nanbei Lake were significantly higher than those in sediments from surrounding water bodies. The gross α (529 ± 41)Bq/L and gross β (927 ± 83)Bq/L activity concentrations in the residue retained on a 0.45 μm filter after filtering Nanbei Lake water were similar to those in the sediments of Nanbei Lake (gross α: (516 ± 35) Bq/L; gross β: (965 ± 68) Bq/L). Conclusion The elevated gross α and gross β activity concentrations in Nanbei Lake water could be attributed to dredging activities, which resuspended sediments into the water column, combined with the inherently high activity concentrations in the sediments.

Objective: To establish an ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method based on solid-phase extraction column purification for simultaneous determination of cyromazine and melamine in poultry eggs and meat. Methods: Eggs, quail eggs, and chicken were collected from markets. After homogenization, the sample was extracted with 0.5% formic acid in acetonitrile, subjected to solid-phase extraction using an MCX cartridge, and eluted with 5% ammonia in methanol. The eluate was collected, evaporated to near dryness under nitrogen, and reconstituted in a 10% aqueous methanol solution. Separated using TSK gel Amide-80 column (2.0 mm×150 mm, 5 μm), cyromazine and melamine were simultaneously detected in positive ion multiple reaction monitoring mode via tandem mass spectrometry, with quantification achieved by isotope dilution internal standard methods. Efficiency was enhanced and matrix interference minimized by optimizing conditions such as sample extraction, solid-phase extraction cartridge selection, and instrumental parameters. Calibration curves were constructed, and detection limits, quantification limits, spiked recoveries, and relative standard deviations for (RSD) of cyromazine and melamine were calculated. Results: After method optimization, matrix effects for cyromazine and melamine ranged from 0.97 to 1.04, indicating no significant matrix suppression or enhancement. Both cyromazine and melamine exhibited excellent linearity within the concentration range of 1.0-200.0 ng/mL, with correlation coefficients ≥0.999 5. The limits of detection were 0.3 μg/kg for cyromazine and 0.5 μg/kg for melamine, the quantification limits were 1.0 and 1.5 μg/kg, respectively. At spiked levels of 1.0, 20.0, and 150.0 μg/kg, the average recoveries ranged from 78.6% to 103.1%, with RSD between 3.5% and 6.3%. Among 95 samples tested, cyromazine was detected in 6 samples and melamine in 5 samples; neither cyromazine nor melamine was detected in chicken samples. Conclusion The UPLC-MS/MS method established in this study enables simultaneous detection and accurate quantification of cyromazine and melamine in poultry eggs and meat.