Thomas R S, Ibrahim S A
Department of Radiological Health Sciences, Colorado State University, Fort Collins 80523.
Health Phys. 1995 Mar;68(3):311-9. doi: 10.1097/00004032-199503000-00002.
Xanthoparmelia spp. lichens were used to study the spatial distribution of plutonium concentrations in nonvascular plants surrounding the Rocky Flats nuclear weapons facility with respect to distance, direction, age, and washing. Plutonium concentrations in lichens were inversely related to distance from the initial contamination site with a directional component which corroborated wind-borne transport as the primary means of dispersion. Ultrasonic washing and the relative age of the lichen proved to be significant only at p = 0.21 and p = 0.96, respectively. Isotopic ratios of 239,240Pu to 238Pu were highly variable at low activities but remained consistent at 62.6 for samples with high total plutonium activity. Correlation of Xanthoparmelia spp. lichen 239,240Pu concentrations to surface soil concentrations showed a direct relationship (r = 0.767; p < 0.001). The correlation was supported by soil retention studies which revealed a lichen soil content ranging from 11 to 18% on a dry mass basis with a possible particle size selectivity in the different concentration ratios adjacent to and away from the initial contamination site. Results suggest that further study into the in situ biomonitoring of surface soil by Xanthoparmelia spp. lichens is promising.
黄盘衣属地衣被用于研究洛基弗拉茨核武器设施周边非维管植物中钚浓度的空间分布，涉及距离、方向、年龄和清洗情况。地衣中的钚浓度与距初始污染地点的距离呈负相关，且存在方向性因素，这证实了风媒传播是主要的扩散方式。超声清洗和地衣的相对年龄分别仅在p = 0.21和p = 0.96时具有显著意义。在低活度下，239,240Pu与238Pu的同位素比率变化很大，但对于总钚活度高的样品，该比率保持在62.6不变。黄盘衣属地衣中239,240Pu浓度与表层土壤浓度的相关性显示出直接关系（r = 0.767；p < 0.001）。土壤保留研究支持了这种相关性，该研究表明，以干质量计，地衣中的土壤含量在11%至18%之间，在初始污染地点附近和远离该地点的不同浓度比率中可能存在粒径选择性。结果表明，对黄盘衣属地衣对表层土壤进行原位生物监测的进一步研究具有前景。
