Abstract Recent years have witnessed more attention paid to the health effects of the natural radionuclide 226Ra, and a series of research carried out on the detection methods of 226Ra at home and abroad. The common 226Ra detection methods are emanation scintillation, gamma spectrometry, liquid scintillation counting, alpha spectrometry and alpha counting. Emanation scintillation is mature enough as a classical method, while gamma spectrometry and liquid scintillation counting proceed fast. Due to the radiation of 226Ra, these detection methods still have the problems such as the requirement for large samples, long detection periods, complicated steps, high detection limits and low recovery rates. This paper reviews the five methods above and summarize their advantages and disadvantages, so as to provide the reference for selecting and optimizing the detection methods for different samples as well as perfecting the standard method in China.

Objective: To quantitatively compare five occupational health risk assessment models in assessing silica dust hazard risk in small open pits, so as to provide the reference for the research of occupational health risk assessment methodology Methods : Seven small open pits were selected as the evaluation sites. The models from Singapore, the United Kingdom's Control of Substances Hazardous to Health Essentials ( COSHH Essentials ), Australia, Romania, and the International Council on Mining and Metals ( ICMM ) were applied to assessing the occupational health risk of the workers exposed to silica dust. The risk ratios ( RRs ) were calculated, and the parallelism, accuracy and correlation of the evaluation results of the five models were compared. Results : The RRs of the Singaporean model, COSHH model, Romanian model, Australian model and ICMM model were 0.8, 1.0, 0.4, 0.6 and 0.8, respectively. The Singaporean model and the Australian model were able to distinguish transport drivers from sprinkler drivers in the health risk exposed to silica dust, which was consistent with the actual risk of the two posts. Except for COSHH model, the RRs of the other four models were positively correlated ( P<0.05 ); the RRs were all positively correlated with concentration ratios ( CRs ) ( P<0.05 ), and the correlation coefficient between RRs and CRs of the Singaporean model was the largest (0.801). Conclusion Among the five models, the Singaporean model can more accurately evaluate the hazard risk of silica dust in posts of open pits, and has a good correlation with the other models.

Objective To establish a rapid,high-efficiency and clean way to monitor and pretreat the radioactivity in foods.Methods Food samples,20 kg each of cabbage,crucian,shrimp,pork and 20 L of milk,were collected around Qinshan nuclear power plant,totaling 10 samples for each food.Each type of foods was arranged in two groups each with 10 samples.Samples were pretreated using traditional ashing method (TAM) and microwave ashing method (WAM) separately.HDEHP were used for 90Sr separation and measurement.Calculations were made for the time spent on food pretreatment.The ash-fresh ratio and the recovery rate of 90Sr by the two different method were calculated,with the quality of ash being evaluated.Results The mean time spent on pretreatment was cabbage 20 h,crucian 54 h,shrimp 46 h,pork 58 h and milk 74 h for TAM group,and cabbage 8.5 h,crucian 26 h,shrimp 23 h,pork 26 h and milk 30 h for WAM group,respectively.The time spent by WAM was half the time less than by TAM,especially for animal edible product.The ash-fresh ratios from WAM group were higher than from TAM group.The recovery rates of 90Sr from WAM group in the analytical process were all above 75％,higher than from TAM group.Ashes produced by WAM were hoary,uniform,carbon residue-free and fully ashed.Conclusions WAM pretreatment can pretreat food rapidly,efficiently,cleanly with less loss and better ashing effect.These can meet the requirement of rapid pretreatment of radioactivity in food.

Methods:the samples were absorbed by solvent desorption silica gel tube and desorbed by methanol. Desorption fluid in the injector at 350 ℃ in the presence of an organic alkali tetramethylamine hydroxide (TMAH, 25% methanol) , allowed quantitative analysis of acrylic acid as its corresponding methyl derivative by gas chromatography.Results:calibration curve of the method was linear within the range 0-258.4 mg/L and showed good linearity with r=0.999 4. The determination limit of the method was 0.9 mg/L, and the minimum detection concentration was 0.06 mg/m 3 (collect 15 L air) . The relative standard deviation ( RSD) was 2.2%-2.7% ( n=5) . Recoveries were between 96.9-101.6%. Conclusion:the results prove on-line methylation gas chromatography is an accurate, simple and high sensitive method for determining acrylic acid in workplace air.

Objective:A method to determine acrylic acid in workplace air was developed by silanization-gas chromatography.Methods:In March 2020, chloroacetic acid in air were absorbed by silica gel tube, the samples were dried, then were desorbed and silanized by acetonitrile: N, O-bis (trimethylsilane) trifluoroacetamide (2∶1, V/V) at room temperature, allowed quantitative analysis of chloroacetic acid as its silanization product by gas chromatography.Results:Calibration curve of the method was linear within the range 0-162.8 μg/ml and showed good linearity with linear equation: y=0.011 8 x, r=0.999 7. The determination limit of the method was 0.8 μg/ml, and the minimum detection concentration was 0.05 mg/m 3 (collect 15 L air) . The relative standard deviation ( RSD) was 0.5%-1.3% ( n=5) . Recoveries were between 98.6%-101.2%. Conclusion:The results prove silanization-gas chromatography is an accurate, simple and high sensitive method for determining chloroacetic acid in workplace air.

Objective:A method to determine acrylic acid in workplace air was developed by silanization-gas chromatography.Methods:In March 2020, chloroacetic acid in air were absorbed by silica gel tube, the samples were dried, then were desorbed and silanized by acetonitrile: N, O-bis (trimethylsilane) trifluoroacetamide (2∶1, V/V) at room temperature, allowed quantitative analysis of chloroacetic acid as its silanization product by gas chromatography.Results:Calibration curve of the method was linear within the range 0-162.8 μg/ml and showed good linearity with linear equation: y=0.011 8 x, r=0.999 7. The determination limit of the method was 0.8 μg/ml, and the minimum detection concentration was 0.05 mg/m 3 (collect 15 L air) . The relative standard deviation ( RSD) was 0.5%-1.3% ( n=5) . Recoveries were between 98.6%-101.2%. Conclusion:The results prove silanization-gas chromatography is an accurate, simple and high sensitive method for determining chloroacetic acid in workplace air.

Methods:the samples were absorbed by solvent desorption silica gel tube and desorbed by methanol. Desorption fluid in the injector at 350 ℃ in the presence of an organic alkali tetramethylamine hydroxide (TMAH, 25% methanol) , allowed quantitative analysis of acrylic acid as its corresponding methyl derivative by gas chromatography.Results:calibration curve of the method was linear within the range 0-258.4 mg/L and showed good linearity with r=0.999 4. The determination limit of the method was 0.9 mg/L, and the minimum detection concentration was 0.06 mg/m 3 (collect 15 L air) . The relative standard deviation ( RSD) was 2.2%-2.7% ( n=5) . Recoveries were between 96.9-101.6%. Conclusion:the results prove on-line methylation gas chromatography is an accurate, simple and high sensitive method for determining acrylic acid in workplace air.

Objective:To investigate the levels of gross radioactivity in drinking water and of 90Sr in food around Sanmen nuclear power plant (NPP) before and after operation. Methods:From 2012 to 2019, 7 drinking water monitoring sites were selected around the Sanmen NPP to collect source water, factory water and peripheral water, respectively, in order to measure and analyze the total radioactivity level in drinking water. Based on the dietary habits of local residents, 4 kinds of food such as grains, vegetables, freshwater fish and marine fish grown locally were sampled to measure and analyze the activity concentration of 90Sr. Results:Before the operation of Sanmen NPP, the total α radioactivity and total β radioactivity in drinking water around the NPP were 0.001-0.063 Bq/L and 0.019-0.210 Bq/L, respectively. After operation, the total α radioactivity and total β radioactivity were 0.001-0.084 Bq/L and 0.025-0.079 Bq/L, respectively. Both were lower than the national standard value given in the GB 5749-2006 " Sanitary standards for drinking water" . There was no significant change in the radioactivity level of source water, factory water and peripheral water during the wet and dry periods. The activity concentration of 90Sr in these four types of food ranged from 0.037 to 1.216 Bq/kg before operation and from 0.049 to 0.692 Bq/kg after operation, all lower than the standard value of " Standard for the concentration in radioactive substances in food" (GB 14882-94). Conclusions:Before and after the operation of Sanmen NPP, the total α and total β radioactivity in drinking water and 90Sr activity concentration in food are stable, below the national standard limit.

Objective:To investigate the activity concentrations of 90Sr and 137Cs in water in Hangzhou urban area. Methods:From 2012 to 2020, Qiantang River water as an important drinking water source, tap water as direct drinking water for residents, and West Lake water in tourists crowded area were selected forwater quality monitoring with respect to conctnts of 90Sr and 137Cs. The activity concentrations of 90Sr and 137Cs in water samples, as collected in wet and dry seasons resepectively, were determined by radiochemical analysis, with the 137Cs to 90Sr activity ratios obtained. Results:From 2012 to 2020, the activity concentrations of 90Sr and 137Cs in tap water were (2.0±1.1) - (7.4±0.4) mBq/L and (0.45±0.06) - (7.1±0.6) mBq/L, respectively. The 137Cs to 90Sr activity ratios ranged from 0.07 to 2.40. The activity concentrations of 90Sr and 137Cs in Qiantang River were (3.7±1.1) - (17.0±4.4) mBq/L and (0.28±0.01) - (15.0±4.5) mBq/L, respectively. The 137Cs to 90Sr activity ratios ranged from 0.03 to 0.90. The activity concentrations of 90Sr and 137Cs in West Lake water were (2.2±0.5) - (11.0±2.0) mBq/L and (0.32±0.04) - (7.9±1.9) mBq/L, respectively. The 137Cs to 90Sr activity ratios ranged from 0.05 to 1.20. Conclusions:The activity concentrations of 90Sr and 137Cs in water in Hangzhou urban area were at the background levels, lower than the concentration limits, 10 Bq/L both for 90Sr and 137Cs recommended by WHO in the 4 th edition of Guidelines for Drinking Water Quality.

Objective:To investigate and analyze the radioactivity level of 90Sr in offshore seawater and seafood therein around Sanmen nuclear power plant (NPP) and to estimate the annual committed effective dose to local population from ingestion of 90Sr in seafood from 2015 to 2019. Methods:From 2015 to 2019, the offshore seawater and 3 kinds of marine products grown locally in Sanmen and consumed by local residents were collected for measurement of the level of 90Sr radioactivity. The committed effective doses to the local population were estimated based on monitoring result and consumption data on seafood in Zhejiang offshore. Results:The radioactivity concentrations of 90Sr ranged from 2.4 to 4.1 mBq/L in the seawater, close to the natural radioacrive background level and from 6.7×10 -2 to 1.3 Bq/kg in seafood, lower than the standard values specified in the "Limited concentrations of radioactive materials in foods" (GB 14882-94). Annual committed effective dose to the local population from 90Sr attributable to consumption of seafood in Sanmen County from 2015 to 2019 were 2.2×10 -4-4.2×10 -4mSv, respectively, far lower than the worldwide committed effective dose result ing from internal exposure. Conclusions:From 2015 to 2019, the radioactivity concentration of 90Sr in seawater and seafood are stable, with neglectable dose burden to the local population.