title: An investigation of the behaviour and distribution of radionuclides in the urban environment of Glasgow
Creators: name: Emery, Catherine
Publisher: name: University of Glasgow
Year: 2003

description: The densely populated nature of urban areas makes them an important area of study with respect to environmental contamination, but these areas have often not received the attention they deserve. This thesis describes a study of the distribution of natural and manmade radionuclides within the City of Glasgow. The environment within Glasgow will not only contain natural radionuclides (which are ubiquitous in the environment), but it will also receive direct input of anthropogenic radionuclides from atmospheric fallout (weapons testing, satellite burn-up and Chernobyl) and possible point sources of both anthropogenic and natural radionuclides may arise from universities, research establishments and hospitals within the city. This initial investigation of the behaviour and distribution of radionuclides in the urban environment of Glasgow incorporates a city-wide investigation of radionuclide activities in a range of environmental materials and a more detailed study of radionuclide distributions and inventories in soil cores from a park within the city. The city-wide investigation included sampling sites both close to, and remote from possible point sources of radionuclides and, over the three sampling times in July 2000 (Peurou, 2000), November 2000 and April 2001, found that specific activities generally decreased in the order grass&gt; street dust &gt; soil. The variability in the specific activities also decreased in this order. The ranges observed in specific activities were 197-2115 (Bq kg-1), 225-479 (Bq kg-1) and 189-1000 (Bq kg-1), in grass, soil and street dust, respectively. Some of this variation has been attributed to environmental management of selected sites. 137Cs specific activities ranged from 1.2-22.5 (Bq kg' ) in grass, 2.4-85.1 (Bq kg-1) in soil and from below the detection limit to 211 (Bq kg-1) in street dust. The 137Cs street dust data population showed a broadly exponential trend with 2 outliers being observed, both near potential point sources of 137Cs. 7Be, a cosmic ray- produced radionuclide, was detected in grass with specific activities in the range 46-530 (Bq kg-1) and in street dust in the range 44-595 (Bq kg-1). Considerable variation was observed both spatially and temporally, despite having a uniform atmospheric production rate and fairly uniform rainfall over the study area. The highest specific activities of 226Ra , a daughter nuclide of 238U, were observed in soil (11.9-44.4 Bq kg-1), with fairly consistent results being observed both spatially and temporally. 131I was detected in the Clyde Estuary, down stream of a hospital with a nuclear medicine facility. This, and the 137Cs outliers in street dust, highlighted that this survey was sensitive enough to detect radionuclides that may be linked to a point source. From the investigation of three cores of contrasting soil types from Pollok Park, a reference site for the city-wide investigation, the coniferous soil was found to have the lowest pH and highest organic content with a 210Pb inventory which was comparable to other 210Pb inventories in the literature for Central Scotland. The deciduous soil, which also had a low pH and high organic content, had a 210Pb inventory approximately a factor of three lower than the coniferous soil. An exponential decrease in unsupported 210Pb specific activities with increasing depth in both the coniferous and deciduous soils could be attributed either to 210Pb accumulation of the soils or to downward migration of the 210Pb. However, the depth distributions of 239,240Pu in both cases were inconsistent with the apparent 210Pb accumulation rates, indicating that the presence of natural and manmade radionuclides at depth in these profiles is almost certainly due to downward migration. The grassland soil, which had a much higher pH and lower organic content than both the forest soils, had a 210Pb inventory comparable with the deciduous soil core. The grassland core exhibited a profile indicative of mixing, and accumulation of this soil is unlikely. All three cores suggest the downward movement of 137Cs. Plutonium was found to be associated with the organic phase of the forest soils but considerable revision of the BCR sequential extraction technique would be needed in future for use on such organic soils.