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Title: The use of radio-nuclides (unsupported 210Pb, 7Be and 137Cs) in air, rain and undisturbed soil as environmental tools
Author: Choubedar, Feraidoun
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2000
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Soil inventories of atmospherically derived 210Pb (radioactive half lives 22.3 years) were used to determine deposition patterns of atmospherically derived aerosols averaged over decades at low altitude sites (51-6° N, 0.6° W) and quantify the enhancement in aerosol deposition by aerodynamically rough canopies (forest) relative to short vegetation (grass). 210Pb and 7Be (radioactive half life 53.4 days) in surface air and rain (55.6° N, 3.9° W) were measured to determine the concentration of these radionuclide isotopes in the environment. Non-destructive gamma-spectrometry was used for all 3 parts using high purity germanium (HPGe) detectors. From the soil samples 137Cs (radioactive half life 30.2 years) are being measured and reported. The average inventories to the canopies compared to the short vegetation for 210Pb and 137Cs for Geescroft forest were 25.7% and 60.8% higher than the open field inventories, respectively; the corresponding values for Broadbalk forest were 30.9% and 68.9% for 210Pb and 137Cs, respectively. Although these two forests are not far from each other and have the same altitude, the excess inventories for Broadbalk forest are larger than Geescroft forest and this could be due to the fact that this forest is acting as an edge, because of its width. The averaged flux for Rothamsted forest soils for 210Pb was determined as 211 ± 6 Bq m-2 y-1 per metre of rainfall, and for the soil and vegetation in the open area 167 ± 6 Bq m-2 y-1 per metre of rainfall. The annual average concentrations in surface air were 0.19 ± 0.06 and 2.71 ± 0.66 mBq m-3 for 210Pb and 7Be, respectively. The annual fluxes of 210Pb and 7Be in rain were determined as 68 ± 10 and 787 ± 29 Bq m-2 y-1 per metre of rainfall, respectively. There was a seasonal variation for 7Be concentrations in air and rain giving spring high. The highest concentrations for 210Pb were obtained when the air mass origin was from continent. From the air and rain data for 210Pb and 7Be, similar washout scavenging ratios (Ws) were obtained, indicating they are scavenged from the atmosphere with a similar rate. The dry deposition of 210Pb and 7Be carrier aerosols were estimated as 41 ± 13% and 35 ± 9% of the total deposition for 210Pb and 7Be, respectively.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available