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Radiation and Radioactivity
Published in Reginald L. Campbell, Roland E. Langford, Terry L. McArthur, Fundamentals of Hazardous Materials Incidents, 2020
Reginald L. Campbell, Roland E. Langford, Terry L. McArthur
Another source of radiation is the ground. Rocks and soils everywhere contain radioactive materials such as potassium–40 (one of the isotopes of natural potassium), uranium, and radium. One product of the decay of uranium is the gas radon, which is found in the air and in groundwater and may supply as much as one half the total radiation exposure to the population of the U.S. Terrestrial sources, including radon, produce about 2.4 millisieverts (240 millirems) each year, with radon alone responsible for about 2 millisieverts (200 millirems).
Nuclear Terrorism
Published in Robert A. Burke, Counter-Terrorism for Emergency Responders, 2017
Radioactive half-life is a term used to express the time it takes for half of the atoms of a given sample of an isotope to decay. Half-life can range from fractions of a millionth of a second to billions of years. No matter what the half-life, some small amounts of nuclei would still remain. It remains theoretically possible that given enough time, all of the atoms would eventually decay. Potassium-40, a radioisotope, has a half-life of 12,500 years. During the first 12,500 years, half of the potassium-40 decays, which means that 50% of the potassium-40 still exists. During the next 12,500 years, that will be reduced by half. The remaining potassium-40 after 25,000 years will be 25%. Each additional 12,500 years will reduce the remaining amount by half. Other radioisotope half-lives include uranium-235 (235U) (704 million years), uranium-238 (238U) (4,470 million years), thorium-232 (232Th) (14,010 million years), and rubidium-87 (87Rb) (48,800 million years). Potassium is an element that has three naturally occurring isotopes: potassium-39 (39K), potassium-40 (40K), and potassium-41 (41K). Potassium-39 and -41 are stable isotopes and comprise 99.99% of all isotopes of potassium. Potassium-40 exists in only 0.01% of all isotopes of potassium but emits radiation and is considered a radioisotope of potassium. These percentages of potassium isotopes are constant in all encounters with potassium. So, since the human body has approximately 150–200 g of potassium, 15–20 mg exists as the radioisotope potassium-40. There is also radioactivity in the air we breathe. Radiation from the sun causes atmospheric nitrogen to produce the carbon radioisotope, carbon-14 (14C) and radioactive hydrogen (tritium, 3H) through a nuclear reaction. Carbon-14 enters the Earth's carbon pool and is fixed by photosynthesis in green plants, which are then consumed by humans and animals. Human exposure also occurs by eating the animals that have eaten the carbon-14 present in the plants. Throughout our lifetimes, we absorb and excrete carbon-14 to the point that it reaches an equilibrium level. The half-life of carbon-14 is 5,730 years, so we do not notice any decay during our life. Once we die and do not absorb any more carbon-14, the amount of its decay in the body can be measured and the age is determined, based upon the amount of decay that has taken place. The age of objects and people can be determined by a method that is often referred to as carbon-14 dating. Most background radiation comes from naturally occurring radon-222 (222Rn) and radon-220 (220Rn). These radioactive gases seep from rocks that contain uranium and thorium and account for 50%–80% of the background radiation exposure. The average individual exposure from background radiation is 360 mrem/year.
Introduction
Published in Vladimir A. Dobrushkin, Applied Differential Equations, 2018
A particle moves along the abscissa so that its velocity at any time t⩾0 is given by v(t)=4/t2+1. Assuming that it is initially at π, show that it will never pass x=2. The slope of a family of curves at any point (x,y) of the plane is given by 1+2x. Derive a differential equation of the family and solve it.The graph of a nonnegative function has the property that the length of the arc between any two points on the graph is equal to the area of the region under the arc. Find a differential equation for the curve.Geological dating of rocks is done using potassium- 40 rather than carbon- 14 because potassium has a longer half-life, 1.28×109 years (the half-life is the time required for the quantity to be reduced by one half). The potassium decays to argon, which remains trapped in the rocks and can be measured. Derive the differential equation that the amount of potassium obeysProve that the equation y'=(ax+b)/(cx+d) has at least one solution of the form y=kx if and only if (b-c)2+4ad⩾0.Which straight lines through the origin are solutions of the following differential equations?
Freshening of seawater in the Mahim Bay, Mumbai, India: Insight from an environmental isotope study
Published in Journal of Operational Oceanography, 2021
Jacob Noble, Tirumalesh Keesari
Researchers of National Institute of Oceanography, Mumbai measured the salinity, dissolved oxygen, nutrients (, , -P etc.) and phytoplankton in the coastal waters, 1 day after the appearance of low salinity water in the Mahim Bay, and hypothesised that the discharge of Mithi River because of the overflow of Vihar and Powai lakes situated on the upstream of the catchment and the surface runoff from the nearby areas, were the causes for the occurrence of low salinity water in the Bay (NIO 2006). Singhal et al. (2007) partially supported this hypothesis based on the measurement of radionuclides such as total uranium (U) and potassium-40 (40K) in coastal water. These measurements gave values similar to the rainwater, indicating that the discharge of freshwater dominated by rainwater as the cause for the freshening of seawater in Mahim Bay.
Assessment of natural radioactivity in rice and their associated population dose estimation
Published in Radiation Effects and Defects in Solids, 2018
Ashikun Nahar, Khandoker Asaduzzaman, M. Moinul Islam, Md. Mashiur Rahman, Mahfuza Begum
There is a global interest in human radiation exposure due to radionuclide intake from food. It is estimated that about one-eighth of the total radiation exposure can be attributed via the consumption of foods (14). Potassium (40K), thorium (232Th), uranium (238U) and their numerous progeny are the common radionuclides available in food and water (4). All types of food including rice contain a detectable amount of natural radioactivity which successively relocate into the human body via the ingestion pathway. Like other foodstuffs, the natural radioactivity in rice may give rise internal radiation exposure. Among the types of food that are commonly consumed worldwide is rice. Rice (Oryza Sativa) is the staple food for a large part of the world's human population, especially in Asia. In Bangladesh, the majority of the people are taking rice in their basic daily diet, therefore the consumption of rice is treated as the most important pathways for the transfer of radionuclides into humans (4). Hence, studies on the radioactivity levels in different types/brands of rice grown and consumed by the people of Bangladesh have been performed with a view to estimating the public exposure.
Radiological toxicity of some fish and meat tissues consumed in southwestern Nigeria
Published in Human and Ecological Risk Assessment: An International Journal, 2018
Oladele Samuel Ajayi, Emmanuel Oluwanifesii Fatile, Chidiebere Goodluck Dike
The activity concentrations of natural radionuclides in fish and meat which are the major sources of protein diet to the people living in the study area have been determined. On the average 40K was found to be the highest in all the meat organs and fish tissues considered in this work. Potassium-40 levels obtained are in agreement with values obtained in other studies by Adamu et al. (2013) and Tchikossa et al. (2013). Generally, the level of radioactivity is relatively low in all the samples and within the limits of internationally acceptable values. Therefore, the food types in this study are safe for human consumption. Although they are safe, a community based awareness program on the issue of environmental contamination, its health impacts, and possible prevention, is advisable.