Objective As an important monitoring target for gaseous effluents from nuclear facilities, the radioactive inert gas ⁸⁵Kr requires accurate measurement, which is crucial for nuclear safety and radiation protection. This study organized an inter-laboratory comparison activity for ⁸⁵Kr gamma-ray spectrometry measurements, with the aims of identifying potential problems in ⁸⁵Kr measurement and improving detection capabilities and proficiency. Methods Four laboratories participated in this comparison. Each laboratory employed gamma-ray spectrometry to measure the comparison samples, and the results were evaluated using the E_n value. Results The measurement results from all participating institutions were acceptable, with the maximum E_n value being 0.73. The results demonstrate that despite the low gamma-ray branching ratio of ⁸⁵Kr and its susceptibility to interference from the 511 keV positron annihilation peak, gamma-ray spectrometry can achieve reliable activity measurements of ⁸⁵Kr. Conclusion The comparison for ⁸⁵Kr gamma-ray spectrometry tested the capabilities of the participating laboratories in ⁸⁵Kr measurement. It promoted technical exchange and experience sharing among laboratories, laying a foundation for future comparisons involving more complex radioactive inert gases.

Objective:To investigate the relationship between artificial radionuclide 137Cs and stable cesium (Cs) in wild edible fungi and seek potential correlations. Methods:A total of 30 samples, including the caps (with gills) and stipes of wild edible fungi, were collected from the northeastern region of China. The measurement and analysis of 137Cs were conducted following recommended procedures in GB/T 16145-2022, and stable Cs was determined using inductively coupled plasma mass spectrometry (ICP-MS). Then, the correlation analysis of data on 137Cs and stable Cs was performed using SPSS 11.5 software, and scatter plots were prepared using the Origin 21.0 software. Results:The fungi caps exhibited a specific activity of 137Cs ranging from 0.52 to 55.9 Bq/kg (dry weight) and a stable Cs content from 0.069 mg/kg to 16.2 mg/kg (dry weight). The stipes showed a specific activity of 137Cs ranging from 0.53 Bq/kg to 101 Bq/kg (dry weight) and a stable Cs content from 0.075 to 11.5 mg/kg (dry weight). These data revealed a significant correlation between the specific activity of 137Cs and the stable cesium content in all samples including caps and stipes, with correlation coefficients r of 0.956, 0.912, and 0.931, respectively, and all significant levels P < 0.01. The ratios of the specific activity of 137Cs to stable Cs content varied from 2.09 Bq/kg to 20.1 Bq/kg (dry weight), with an average of 10.7 Bq/kg (dry weight). Conclusions:Wild edible fungi fail to distinguish between 137Cs and stable cesium when absorbing Cs elements from their growing substrates. Furthermore, there is a strong correlation between the specific activity of 137Cs and stable Cs content. In the case of exogenous 137Cs contamination, the ratio of the specific activity of 137Cs and stable Cs content will significantly change. Therefore, an increase in the ratio can be used as a reference for identifying 137Cs contamination events.

Objective:To understand the activity concentrations of varying chemical forms of 131I in nuclear medicine workplaces and assess the internal irradiation doses of 131I to workers. Methods:A high-volume air sampler was used for air sampling of 131I. Glass fiber filters, activated carbon filters, and iodine cartridges, which were connected in series, were employed to collect aerosol iodine, gaseous inorganic iodine, and gaseous organic iodine, respectively. A method for analyzing the activity of 131I unevenly distributed in the iodine cartridge was developed, and an HPGe γ spectrometer was used to determine the activity of 131I in samples collected from the nuclear medicine workplaces of 15 hospitals. Results:The concentrations of aerosol iodine, inorganic iodine, and organic iodine in 15 hospitals were determined at 0.19-206.67, 0.27-138.45, and 2.35-3 821.11 Bq/m 3, respectively, with arithmetic means of 22.04, 12.79 and 365.08 Bq/m 3, respectively. The maximum annual committed effective doses of varied forms of 131I inhaled by workers were determined at 0.19, 0.19, and 3.81 mSv, respectively, with a maximum total committed effective dose of 4.13 mSv. Conclusions:Gaseous organic iodine is identified as the primary form of 131I in the air within nuclear medicine workplaces. Therefore, it is necessary to highlight the monitoring and protection of gaseous organic iodine.

To characterize the genomes of different emm-type group A Streptococcus (GAS), their virulence genes and drug resistance profiles in Tianjin City from 2011 to 2024. After PCR, a total of 42 strains with different years and emm types were selected for whole genome sequencing and multi-locus sequence typing (MLST), and the core genomes were used to generate a phylogenetic tree, after which the virulence genes and resistance genes were identified and analyzed, followed by the drug susceptibility test. In this study, the GAS strains were dominated by emm1 (50.0%) and emm12 (40.4%), and the MLST phenotypes were categorized into six types: ST36 (40.4%), ST1274 (26.1%), ST28 (23.8%), ST921 (4.7%), ST46 (2.3%), and ST403 (2.3%). There was a high consistency between their emm-types and ST types. A total of 68 virulence genes were detected in the genomes of 42 GAS strains, involving functional genes encoding exotoxin, bacterial adhesion, extracellular enzymes, etc. The virulence genes they carried were significantly different between emm1-type and emm12-type strains, such as speA. At the same time, the carrying rates of some virulence genes in the same emm-type strains changed with time, such as hyl. The resistance genes were basically the same among different emm-type strains except for the vanSE gene detected in all emm12 strains. The results of drug sensitivity showed that the GAS strains isolated in Tianjin City from 2011 to 2024 were sensitive to penicillin, cefazolin, chloramphenicol, vancomycin, and levofloxacin, while the resistance rates to erythromycin, azithromycin, clarithromycin, and clindamycin ranged from 88.5% to 100.0%, and there was a certain degree of consistency between the resistance phenotypes and the detected resistance genes. Overall, the main emm types and evolutionary features of GAS in Tianjin City from 2011 to 2024 were consistent with the dominant types in China, and the carrying rate of virulence genes and drug resistance genes differed significantly among different emm-type strains, and there were continuous evolution and variation in the prevalence of virulence genes in GAS.

Objective:To investigate the relationship between artificial radionuclide 137Cs and stable cesium (Cs) in wild edible fungi and seek potential correlations. Methods:A total of 30 samples, including the caps (with gills) and stipes of wild edible fungi, were collected from the northeastern region of China. The measurement and analysis of 137Cs were conducted following recommended procedures in GB/T 16145-2022, and stable Cs was determined using inductively coupled plasma mass spectrometry (ICP-MS). Then, the correlation analysis of data on 137Cs and stable Cs was performed using SPSS 11.5 software, and scatter plots were prepared using the Origin 21.0 software. Results:The fungi caps exhibited a specific activity of 137Cs ranging from 0.52 to 55.9 Bq/kg (dry weight) and a stable Cs content from 0.069 mg/kg to 16.2 mg/kg (dry weight). The stipes showed a specific activity of 137Cs ranging from 0.53 Bq/kg to 101 Bq/kg (dry weight) and a stable Cs content from 0.075 to 11.5 mg/kg (dry weight). These data revealed a significant correlation between the specific activity of 137Cs and the stable cesium content in all samples including caps and stipes, with correlation coefficients r of 0.956, 0.912, and 0.931, respectively, and all significant levels P < 0.01. The ratios of the specific activity of 137Cs to stable Cs content varied from 2.09 Bq/kg to 20.1 Bq/kg (dry weight), with an average of 10.7 Bq/kg (dry weight). Conclusions:Wild edible fungi fail to distinguish between 137Cs and stable cesium when absorbing Cs elements from their growing substrates. Furthermore, there is a strong correlation between the specific activity of 137Cs and stable Cs content. In the case of exogenous 137Cs contamination, the ratio of the specific activity of 137Cs and stable Cs content will significantly change. Therefore, an increase in the ratio can be used as a reference for identifying 137Cs contamination events.

Objective:To understand the activity concentrations of varying chemical forms of 131I in nuclear medicine workplaces and assess the internal irradiation doses of 131I to workers. Methods:A high-volume air sampler was used for air sampling of 131I. Glass fiber filters, activated carbon filters, and iodine cartridges, which were connected in series, were employed to collect aerosol iodine, gaseous inorganic iodine, and gaseous organic iodine, respectively. A method for analyzing the activity of 131I unevenly distributed in the iodine cartridge was developed, and an HPGe γ spectrometer was used to determine the activity of 131I in samples collected from the nuclear medicine workplaces of 15 hospitals. Results:The concentrations of aerosol iodine, inorganic iodine, and organic iodine in 15 hospitals were determined at 0.19-206.67, 0.27-138.45, and 2.35-3 821.11 Bq/m 3, respectively, with arithmetic means of 22.04, 12.79 and 365.08 Bq/m 3, respectively. The maximum annual committed effective doses of varied forms of 131I inhaled by workers were determined at 0.19, 0.19, and 3.81 mSv, respectively, with a maximum total committed effective dose of 4.13 mSv. Conclusions:Gaseous organic iodine is identified as the primary form of 131I in the air within nuclear medicine workplaces. Therefore, it is necessary to highlight the monitoring and protection of gaseous organic iodine.

To characterize the genomes of different emm-type group A Streptococcus (GAS), their virulence genes and drug resistance profiles in Tianjin City from 2011 to 2024. After PCR, a total of 42 strains with different years and emm types were selected for whole genome sequencing and multi-locus sequence typing (MLST), and the core genomes were used to generate a phylogenetic tree, after which the virulence genes and resistance genes were identified and analyzed, followed by the drug susceptibility test. In this study, the GAS strains were dominated by emm1 (50.0%) and emm12 (40.4%), and the MLST phenotypes were categorized into six types: ST36 (40.4%), ST1274 (26.1%), ST28 (23.8%), ST921 (4.7%), ST46 (2.3%), and ST403 (2.3%). There was a high consistency between their emm-types and ST types. A total of 68 virulence genes were detected in the genomes of 42 GAS strains, involving functional genes encoding exotoxin, bacterial adhesion, extracellular enzymes, etc. The virulence genes they carried were significantly different between emm1-type and emm12-type strains, such as speA. At the same time, the carrying rates of some virulence genes in the same emm-type strains changed with time, such as hyl. The resistance genes were basically the same among different emm-type strains except for the vanSE gene detected in all emm12 strains. The results of drug sensitivity showed that the GAS strains isolated in Tianjin City from 2011 to 2024 were sensitive to penicillin, cefazolin, chloramphenicol, vancomycin, and levofloxacin, while the resistance rates to erythromycin, azithromycin, clarithromycin, and clindamycin ranged from 88.5% to 100.0%, and there was a certain degree of consistency between the resistance phenotypes and the detected resistance genes. Overall, the main emm types and evolutionary features of GAS in Tianjin City from 2011 to 2024 were consistent with the dominant types in China, and the carrying rate of virulence genes and drug resistance genes differed significantly among different emm-type strains, and there were continuous evolution and variation in the prevalence of virulence genes in GAS.

Objective:To understand the contamination risk, drug resistance and virulence characteristics of cooked food pathogens in Tianjin.Methods:Pathogenic bacteria were isolated and identified in cooked food sold in Tianjin from 2019 to 2021, drug susceptibility test and whole genome sequencing were conducted for the isolates, and multilocus sequence typing, drug resistance gene, phenotype and virulence gene were analyzed for the data.Results:Ten pathogenic bacteria were isolated from 245 cooked food samples collected. The ST types of 7 Salmonella strains were ST40, ST198, ST14, ST13 and ST155. The two strains of Vibrio parahaemolyticus were ST647 and ST2622 respectively. One strain of Cronobacter sakazakii was ST8 type. All the 6 isolates were drug-resistant, and 3 of them were multidrug-resistant (MDR). A total of 63 drug-resistant genes were predicted in 10 isolates. Two Salmonella strains were ampicillin-chloramphenicol-streptomycin-sulfamethoxazole-tetracycline resistant (MDR-ACSSuT), and both Salmonella strains carried gyrA double mutations (S83F, D87N) and parC mutations (S80I). Vibrio parahaemolyticus mainly carries blaCARB and tet (35) genes, while Cronobacter sakazakii carries only one resistance gene blaCSA-1. A total of 163 virulence genes were predicted from 10 isolates. Conclusions:In this study, pathogenic bacteria are repeatedly detected in quail eggs, warning that other eggs besides chicken eggs should also pay special attention to the risk of contamination. The isolates in this study are all of the prevalent ST type with widespread drug resistance, and MDR-ACSSuT strains should be paid attention to. The key role of gyrA double mutation (S83F, D87N) and parC mutation (S80I) in the development of quinolone resistance should not be ignored. T3SS (typeⅢ secretory system) and T6SS (typeⅥ secretory system) are important virulence gene clusters of Salmonella and Vibrio parahemolyticus.

Objective To develop a large-volume sample cassette in the shape of a formalin cup suitable for portable HPGe γ spectrometer, to determine the detection limits of the cassette at different detection times through fresh sample measurements, and to provide a reference for responding to and monitoring of nuclear and radiation emergencies. Methods According to the formula for calculation of detection limit described in the GB/T 16145—2022, ¹³¹I and ¹³⁷Cs were measured using the sourceless efficiency calibration software Angle and the portable HPGe γ spectrometer for the optimization of the large-volume sample cassette. Fresh salmon samples were measured using a formalin cup-shaped large-volume sample cassette. The detection times were 2, 4, 6, 8, 10, 19, 19, 22, and 24 hours. The relationship between detection time and detection limit was assessed. Results Using sample cassettes with 15 cm radius and 10 L volume, the simulated detection efficiency of the formalin cup-shaped large-volume sample cassette was 30%-46% higher and the detection limit was lower as compared with the cake-shaped large-volume sample cassette. The detection limit obtained by measuring fresh salmon samples decreased with the extension of the detection time. These results provided a reference for the detection limits of measuring fresh samples for nuclides of concern in nuclear contaminated water with different detection times. Conclusion The formalin cup-shaped large-volume sample cassette developed by combining the optimization of detection limit provides a geometry for quantitative analysis in on-site monitoring of γ nuclides in the case of emergencies. Measurement of fresh samples using the cassette with different detection times showed that 8-10 hours of detection was optimal in balancing the detection limit and the detection time.

Objective To further extend the application of coincidence summing correction factor transfer experiments through the analysis of relevant measurements. Methods The passive efficiency was simulated using BE5030 high-purity germanium (HPGe) γ-energy spectrometer equipped with LabSOCS, and the total efficiency was simulated using LabSOCS in GENIE 2000 spectrum analysis software, which was used for calculating the coincidence summing correction factor. The coincidence summing correction factor transfer experiments were performed using the measurements with the point source containing ¹³⁴Cs, ⁶⁰Co, and ¹³⁷Cs as well as the body source to obtain the coincidence summing correction factors of other HPGe γ-energy spectrometers. Results The coincidence summing correction factors for ¹³⁴Cs and ⁶⁰Co were obtained using the BE5030 γ-energy spectrum. In verification by certificate activity, the absolute value of the maximum deviation was within 3.53%. Using coincidence summing correction factor transfer experiments, these factors were transferred to other high-purity germanium γ spectrometers. In verification by certificate activity, the absolute value of the maximum deviation was within 5.86%. Conclusion The coincidence summing correction factors calculated using simulated total efficiency by calling LabSOCS in the GENIE 2000 spectrum analysis software are effective in correction, and can be used as correction factors in standard laboratories. Through coincidence summing correction factor transfer experiments, the coincidence summing correction of other high-purity germanium γ-energy spectrometers can be achieved, which broadens the application of coincidence summing correction method.