Chloropicrin can be produced during chlorination of drinking water in the presence of nitrated organic contaminants. The half-life of chloropicrin in sandy loam soil was 8вЂ“24В h and 4.5В days, with carbon dioxide being the terminal breakdown product. Raman, in Encyclopedia of Toxicology (Third Edition), 2014 Environmental Fate and Behavior The mass attenuation ( m m) can be calculated for the sample and standard using the following equation: This procedure is repeated for a standard source. This is continued until there is no reduction in counts by the addition of more sheets. The count rate is measured and a succession of aluminum sheets of increasing thicknesses are placed between the source and the counter and the measurement repeated. The radiation source is placed in front of a GeigerвЂ“Mueller counter. Beta particle emitters can also be analyzed by the construction of an attenuation curve. Nuclides that emit alpha and beta particles can be analyzed using liquid scintillation counting and spectrometry. The spectrum can be used to identify which nuclides are present in a source and in what quantities. Radionuclides that emit gamma rays or detectable X-rays can be analyzed using gamma spectrometry. The nature and energy of the radiation emitted may be determined by several procedures depending on the type of radiation emitted.

The half-life of 53Mn is a subject of active research. This downward revision of the half-life lowers by ~В 8% ages based on 10Be alone. Several groups have remeasured or assessed the 10Be half-life, which is still вЂofficiallyвЂ™ listed as 1.5В Ma. For simplicity, in this work, we have retained the older age scale. The production rates for both ordinary chondrites ( Eugster, 1988) and achondrites ( Eugster and Michel, 1995) assume the older half-life and consequently lead to CRE ages ~В 7.5% lower than we would calculate today. In 2008, the 81Kr half-life listed in the widely used online version of the Table of Nuclides ( ) was increased from 0.213 to 0.229В Ma (see, Baglin, 2008). In the last decade, some half-lives important for CRE age calculations have been revised. While such changes may be important for understanding the dynamics of meteoroid delivery to Earth, they do not affect the relative values of the CRE ages and, hence, the characteristic shapes of CRE age distributions. It follows that all CRE ages would then shift upward by 10%. Thus, an increase of 10% in the half-life of 81Kr would decrease by 10% any value of P s based on 81Kr measurements. In all cases, the absolute production rates depend inversely on the half-life of the radionuclide of interest. The half-lives (decay constants) that appear in many of the equations used to calculate CRE ages undergo revision from time to time. Caffee, in Treatise on Geochemistry (Second Edition), 2014 1.13.2.6 The Importance of Half-Lives

What is a half life