Combined Determination Method And Accumulation Of ²¹⁰Pb And ²¹⁰Po In Seafood

Background210Pb(T1/2=22.3 a,highly toxicity)and its daughter 210Po(T1/2=138.4 d,extreme toxicity)are decay chain radionuclides of 238U.Due to the accumulation of 210Pb and 210Po in seafood samples,the radiation dose caused by these two nuclides account for 80%of that caused by the ingestion of uranium-and thorium-series radionuclides.Therefore,210Pb and 210Po were considered as the most important contributors for internal exposure monitoring and critical nuclide for National Monitoring for Radioactivity in Foods.The traditional 210Pb and 210Po analysis method are time comnsuming because of a long waiting time and tedious analytical procedure.Owing to big difference in their half-life,the concentration of 210Pb and time interval between sampling and analysis will affect the accuracy of 210Po results.With the rapid development of new materials and new technologies,combined the selectivity of target radionuclides from crown ether extraction chromatography and the discrimination of α/βradionuclides from liquid scintillation counter,The establishment of rapid and combined analysis methods for 210Pb and 210Po in seafood samples is of great significance.It has been reported that 210Pb and 210Pb are enriched in marine seafoods.However,their bioaccumulation and distribution mechanisms in the seafood have not been fully understood,and it’s a hot topic in this research field.The research on the accumulation,distribution and related biomarkers of 210Po and 210Pb in different marine products is of great impaotance,which can provide important basic data for the construction of a reference marine biota for 210Po and 210Pb bioaccumulation model,which may helpful to obtain early warning signals of radionuclide risk,and which could evaluating and predicting the ecological risks of radionuclides and ensuring marine ecological security.ObjectivesThis work aims to establish a simultaneous method for the determiantion of 210Pb and 210Po in marine products,which could provide technical reserves for analysis of natural radionuclides in food;investigate the level of 210Pb and 210Po and 210Po/210Pb ratio in different marine organs by analysis of maine biota collected from Chinese coast in Fujian using proposed method,and The correlation between 210Pb or 210Po activity concentrations in marine organisms and oxidative stress biomarkers were preliminarily discussed.This study could provide new ideas and scientific basis for the application of related biomarkers in marine ecological environment monitoring.MethodsThe influencing factors for the measurement of α/β radionuclides by Liquid scintillation counter(pure a/(3 emitter,quenching level,type and volume of scintillation cocktail)and the influencing factors for the separation of Po and Pb by crown ether extraction chromatography(column volume,column medium and acidity,eluent/desorption solvent and dosage,flow rate);Establishing a joint analysis procedure for 210Pb and 210Po in marine products.The accuracy of the method was verified by using China coastal marine products and reference materials(IAEA-447).The 210Po and 210Pb activity concentrations and 210Po/210Pb ratio in different organs of marine products collected in Chinese coast were investigated.The accumulation and distribution of 210Po and 210Pb in selected organisms were clarified.The annual effective dose and lifetime cancer risk of residents due to ingesting marine seafoods were estimated,and compared with the reported data in other Chinese seafood and those collected from other countries.Correlation between 210Po and 210Pb concentrations and biomarkers of oxidative stress biomarkers H2O2,malondialdehyde and total superoxide dismutase(T-SOD)in the organs were analyzed,and the possible correlation were preliminarily explored.ResultsBy optimizing the influencing factors of liquid scintillation counter for measuring α/βnuclides(209Po and 40K as pure α/β nuclides,2 mL 0.1 mol/L nitric acid as medium and 18 mL Gold AB scintillator as cocktail),PSA value were determined.Under this value,the liquid scintillation has the lowest spillover for α/β nuclides discrimination.0.5 g dried seafood samples were digested by microwave,and converted into 2 mol/L hydrochloric acid medium.After adding a pre-conditioned crown ether extraction chromatographic column,20 mL 2 mol/L hydrochloric acid solution was used to remove 210Bi and other interfering ions.Then 210Pb and 210Pb were eluted by 25 mL 0.1 mol/L HNO3 and 20 mL 0.1 mol/L ammonium oxalate solution,respectively.The 210Pb and 210Pb activity concentrations were determined by liquid scintillation counter using optimized PSA value.The recovery of 210Pb and 210Po were 70%and 85%,respectively,and the analysis of each batch of samples can be completed within 2 days.The 210Pb and 210Po activity concentrations of IAEA-447 reference substance were consistent with the standard values by this method.The activity concentration of 210Po in China’s coastal marine products is consistent With the classical alpha spectrometry method.The detection limits of 210Po and 210Pb for 0.5 g dried seafood samples were 0.30 Bq/kg and 0.77 Bq/kg,respectively.The relative expanded uncertainty of 210Po and 210Pb analysis results was 7.4%(k=2,95%confidence interval).The activity concentrations for 210Po in the investiged 8 species of seafood ranged from 0.74±0.08 to 12.6±1.0 Bq/kg and from 0.80 Bq/kg to 11.7± 1.1 Bq/kg for 210Pb.Overall,the order of 210Po activity concentration in edible part of different marine products is mollusk>crustacean>algae samples.210Pb activity concentration has no obvious regularity.The average 210Po activity concentration in the stomach,heart,liver,gonad and intestine of sea fish was significantly higher than that in other samples(P<0.05).The average 210Pb activity concentration in the fish head,fin,scale and gill samples was significantly higher(P<0.05)than that in other samples.The 210Po/210Pb ratios in the stomach,liver,gonad and intestine of sea fish were significantly higher than 1,while those in the bone,gill,head,scale and fin of fish were generally lower than 1.The 210Pb activity in crustacean and mollusc marine products had no obvious regularity,and was lower than the 210Po activity concentration.The annual effective ingestion doses for all age groups ranged from 82.8 to 255 μSv/a.The effective dose caused by 210Pb and 210Po was lower than the legal dose limit of 1 mSv per year for public recommended by International Atomic Energy Agency and The Food and Agriculture Organization.The lifetime cancer risks varied in the range of 6.04×10-6 to 1.24×10-4.H2O2 content in muscle tissue of Razor clam(Lamarck)samples increased with the increase of 210Po activity concentration in marine products,a positive correlation between the 210Po activity concentration and the H2O2 content in the muscle tissues of clam samples(R=0.682,P<0.05)was observed.It indicates that H2O2 in muscle tissue of Razor clam(Lamarck)has the potential as a biomarker for monitoring marine 210Po pollution.There was no correlation between 210Po activity concentration in liver and spleen of Carassius auratus or shrimp samples and H2O2 content,malondialdehyde content and T-SOD activity(P>0.05),while there was a significant correlation between H2O2 content and malondialdehyde content(R=0.986,P0.05).There was no correlation between 210Pb activity concentration and H2O2 content,malondialdehyde content and T-SOD activity in muscle tissue of Razor clam(Lamarck),Shrimp and liver/spleen of Carassius auratus(P>0.05).ConclusionThe conjoint analysis method of 210Pb and 210Po in marine products was successfully established in this study.The accumulation and distribution of 210Pb and 210Po in different marine products and the significant positive correlation between 210Po activity concentration and H2O2 content in Razor clam samples(Lamarck)were clarified using this method,which could provide new ideas and scientific basis for the application of 210Pb and 210Po in marine ecological environment monitoring.