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The source of radioactivity in waterRadioactivity in water mainly comes from radioactive materials in rocks, soil and air. Rock, soil contains uranium, thorium, actinium three radiation systems and potassium, rubidium and other natural radionuclides, these nuclides formed by a variety of water soluble can be taken to the drinking water source, insoluble radioactive materials will also be with sediment and other solid particles into the water. Radionuclides such as tritium and radon contained in the air can also be brought into the water by rain, snow and dust.The development and utilization of radioactive mineral resources, the processing and treatment of nuclear fuel, the operation of nuclear installations and facilities, the disposal of nuclear waste, the gaseous and liquid radioactive effluents and the radionuclides released by the effluents at all stages are easy to lead to the accumulation of radioactive doses in the environment and water. In particular, nuclear leakage accidents like the Chernobyl nuclear power plant released a large amount of radioactive materials into the environment, resulting in radioactive contamination of a certain range of water, which is not edible.Radioactive contamination from a nuclear power plant in Florida recently spilled into Key Biscayne Bay in the southeastern part of the state, posing a potential threat to public safety and the drinking water supply of southern Florida, media reported.The exploitation, processing and application of fossil fuels (coal, oil, natural gas, etc.), geothermal, phosphate ore, rare earth ore and other mineral resources with high radioactive material content may emit radioactive wastes and pollute the water quality of downstream rivers.China has done an investigation on the radioactive pollution of coal to the environment, and found that the content of uranium in the waste water of a power plant and a coal preparation plant was 20 times that of ordinary water, and the content of radium was 15 times that of ordinary water. If the waste water is discharged at will, it will pollute the water environment. For example, Liaoning Province adopts non-uranium mine radioactive sewage treatment facilities, so that the radioactive mine water produced by mining can meet the safety standards after treatment.In order to let people drink good water, the relevant environmental protection departments should strengthen the investigation and detection of water environment conditions, the total radioactive substance content of drinking water for strict monitoring, to prevent general drinking water radioactive substances exceed the standard.There are radiation limits for drinking waterIf the radionuclides in water enter the human body, they will produce internal radiation, which will harm human health if exceeded a certain limit, such as causing cancer, cataract or other radioactive diseases, or have adverse effects on their offspring.So is there a national control standard for this kind of substance?Drinking water is usually tested for "total radioactivity," which measures whether the level of radioactivity in the water is above the limit. Currently, countries have set limits for the amount of radioactive particles in drinking water. For example, Japan sets the maximum concentration of iodine-131 in drinking water for infants at 100Bq per liter. Because infants are vulnerable to radioactive iodine, the acceptable level of iodine-131 in drinking water for adults is 300Bq per liter.The World Health Organization recommends a total alpha radioactivity of 0.1Bq/L and a total beta radioactivity of 1Bq/L. According to China's Hygienic Standards for Drinking Water (GB5749-2006), the limit of total alpha radioactivity is 0.5 Bq/L and the limit of total beta radioactivity is 1Bq/L.Radioactivity in drinking water is measured mainly with a low background α/β meter.According to the distribution of natural radionuclides in various sources of water in our country, when the total radionuclide specific activity in drinking water exceeds 0.5 Bq/L, it is generally necessary to measure the radionuclide uranium or radium-226, estimate the resulting dose, and then decide whether it is drinkable. In suspicion of artificial radionuclide pollution, but also for artificial radionuclide analysis and determination.