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Radionuclide Transport Processes and Modeling
Published in Michael Pöschl, Leo M. L. Nollet, Radionuclide Concentrations in Food and the Environment, 2006
Apart from light rain conditions, wet deposition is likely to be much greater than dry deposition for aerosols and a few times greater for elemental iodine [28]. Rains are very efficient at driving airborne pollutants toward the ground.
Modeling Exposure
Published in Samuel C. Morris, Cancer Risk Assessment, 2020
Factors which differ in different versions of Gaussian plume models include the way they calculate plume rise, the way they handle what happens when the plume hits the ground or an inversion layer (absorbed, bounces off), and the number of stability categories used and how they are treated. A plume coming out of a smokestack rises due to its high temperature and the inertia of its current movement. The point of origin of the plume dispersion model is not the top of the stack, but the point to which the plume rises. This is called the “virtual stack height” and there are differing ideas on how it should be calculated. This is an important parameter since it, combined with the dispersion characteristics, will define where the plume will first hit the ground. The simplest versions assume the plume is 100% reflected off the ground like a mirror. A similar phenomenon is often assumed when the plume hits an inversion layer which acts as a lid on the mixing zone. Pollutants hitting the ground, however, in actuality are often adsorbed rather than reflected, especially if they are chemically reactive. Loss to the ground is called deposition. More sophisticated versions take this into account by allowing a percentage “loss” to the ground with the rest reflected. In some versions deposition is determined by assigning a “deposition velocity.” Some versions account for this “dry deposition” through one mechanism and for “wet deposition,” contaminants washed out by rain and snow, by a separate mechanism. Predicted concentrations in air are not especially sensitive to differences in accounting for deposition or in errors in deposition rate. At times, however, concern is with the material deposited rather than the air concentration. The amount of material deposited is sensitive to the method of determining deposition and to errors in deposition parameters. Unfortunately, the ability to predict deposition includes numerous uncertainties.
Evolution of radioecology in Armenia: a short review
Published in International Journal of Radiation Biology, 2022
Due to the high density of population, numerous industrial enterprises, and the close location from ANPP an impressive amount of radioecological data was generated for Yerevan, the capital of Armenia. In the 1960s some 850 urban topsoil and 50 atmospheric dry deposition samples were collected as a material for radioecological studies (Ananian 1989; Ananian and Araratyan 1990; Ananyan and Nalbandyan 2001; Nalbandyan 2005), however more informative data was obtained as a result of comprehensive urban soil survey implemented in Yerevan in 1990, 2002 and 2012. The geochemical survey of 1990 (principal investigator – Dr. V. Ananyan) reflected the radioecological situation of Yerevan, which was emerged as a result of major nuclear disasters on a global scale (viz Chernobyl accident) and atmospheric nuclear weapons testing. In 1990 the soils of Yerevan were characterized with the high variability of gross beta activity: 538–916 Bq/kg. After the partial nuclear weapon test ban of 1963 and the adoption of the Comprehensive Nuclear-Test-Ban Treaty by the UN in 1996, the gross beta activity decreased dramatically (Figure 3). Activity concertation of artificial 137Cs, 90Sr in the dry atmospheric deposition collected in Yerevan and Ararat Valley were decreased as well and reached the ‘pre-Chernobyl’ levels up to 2002 (Nalbandyan and Karapetyan 2003; Pyuskyulyan et al. 2008). This more detailed radioecological study was implemented by Dr. A. Nalbandyan with coworkers.
Distribution of 210Po in spice plants cultivated by conventional farming
Published in International Journal of Radiation Biology, 2022
One of the potential sources of 210Po in the atmosphere is 222Rn gas which diffuses into atmosphere from rocks and soil and decays to 210Po through 210Pb and 210Bi isotopes. 210Po and 210Pb return to the earth’s surface via both wet and dry deposition (Brown et al. 2011; Persson and Holm 2011), and their presence in all terrestrial foodstuff is inevitable. Concentration of 210Po in the environment is enhanced by human activities like firing coal in power stations, coal mining and use of phosphate fertilizers (Khater and Bakr 2011).
Review of mechanisms of genotoxic action of dibenzo[def,p]chrysene (formerly dibenzo[a,l]pyrene)
Published in Toxin Reviews, 2023
K. Kowalczyk, J. Roszak, Z. Sobańska, M. Stępnik
Polycyclic aromatic hydrocarbons (PAHs) are a chemically diverse group of environmental pollutants found in water, air, and soil, released by incomplete combustion of anthropogenic and natural sources. Anthropogenic sources of PAHs include vehicle exhausts, wood and fuel fossil burning, asphalt and coal-tar pitch production. PAHs consist of several hundred chemically related compounds, environmentally persistent, with various structures and varied toxicity (Chang et al.2019). They are highly lipophilic and have a relatively low solubility in water. Moreover, solubility in aqueous environment decreases with each additional ring added to PAHs (Błaszczyk and Mielżyńska-Švach 2017). The behavior of PAHs in the atmosphere depends on interactions with other pollutants, complex physicochemical reactions, and photochemical transformations, as well as wet and dry deposition. Commonly, PAHs enter the environment through various routes and are usually found as a mixture containing two or more of these compounds, e.g. soot (Abdel-Shafy and Mansour 2016, Chang et al.2019). The important route of exposure to PAHs in the general population is breathing indoor and ambient air, smoking cigarettes, eating meal containing PAHs and breathing smoke from open fireplaces. For example, the tobacco smoke includes a diversity of PAHs, such as benzo(a)pyrene (BAP), and more than 40 known or suspected human carcinogens. Some crops, such as rye, lentils, and wheat may synthesize PAHs or engross them via soil, air, or water. The environmental water can contain certain amounts of PAHs because those compounds can enter from industrial effluents and marine accidental spills during oil shipment or can leach from the soil into water. Therefore, PAHs exposure occurs on a regular basis for most people (Abdel-Shafy and Mansour 2016).