The radiobiogical effects on scots pine trees (pinus sylvestris) in the chernobyl exclusion zone.
Dear Editors: AS A contribution to the interesting paper by Yoschenko et al. (2011), I report here the results of a sampling performed 20 years ago in the Chernobyl exclusion zone. From 27 April to 2 May 1991, a seminar on ‘‘Radioecology and Countermeasures’’ was organized in Kiev by the Soviet Branch of the International Union of Radioecology. In the framework of the seminar, I participated in a visit to the exclusion zone with a collection of many samples (Cigna 1991). In particular, I got a pine tree less than 1 m high and a very small one (about 10 cm high) grown in an experimental field from a seed, which became irradiated at the time of the accident. Both plants were immediately transplanted in my garden in North Italy. The small pine showed at first some morphological changes with many apical branches, but after some years it started to develop regularly just as nonirradiated pine trees. In March 1996, the younger plant was about 50 cm high and the older one about 1.5 m high (Fig. 1). The growth of both plants developed regularly (Fig. 2), and at present the younger plant is now about 9 m high with a slimmer trunk, while the other older pine, which was already grown up at the time of the accident, is about 7 m high. The diameter at breast height is 17 cm for the younger plant (about 20 y old) and 23 cm for the
CHRONIC IRRADIATION OF SCOTS PINE TREES (PINUS SYLVESTRIS) IN THE CHERNOBYL EXCLUSION ZONE: DOSIMETRY AND RADIOBIOLOGICAL EFFECTS
To identify effects of chronic internal and external radiation exposure for components of terrestrial ecosystems, a comprehensive study of Scots pine trees in the Chernobyl Exclusion Zone was performed. The experimental plan included over 1,100 young trees (up to 20 y old) selected from areas with varying levels of radioactive contamination. These pine trees were planted after the 1986 Chernobyl Nuclear Power Plant accident mainly to prevent radionuclide resuspension and soil erosion. For each tree, the major morphological parameters and radioactive contamination values were identified. Cytological analyses were performed for selected trees representing all dose rate ranges. A specially developed dosimetric model capable of taking into account radiation from the incorporated radionuclides in the trees was developed for the apical meristem. The calculated dose rates for the trees in the study varied within three orders of magnitude, from close to background values in the control area (about 5 mGy y−1) to approximately 7 Gy y−1 in the Red Forest area located in the immediate vicinity of the Chernobyl Nuclear Power Plant site. Dose rate/effect relationships for morphological changes and cytogenetic defects were identified, and correlations for radiation effects occurring on the morphological and cellular level were established.
Geographic And Environmental Influence On Maya Settlement Patterns Of The Northwest Yucatan: An Explanation For The Sparsely Settled Western Cenote Zone
Most settlement pattern research and GIS analysis of the ancient Maya of the Northern Yucatan have focused on water availability in a dry landscape where cenotes are often the only water source. While water is of paramount importance, permanent settlement secondarily requires farmable soil, a resource often as precious as water in many parts of the Yucatan. The dynamics between these resources reveal areas of ideal settlement and more challenging landscapes for which the Maya developed strategies to overcome environmental conditions. A region of the southwest "Cenote Zone", however, appears to have presented the ancient Maya with insurmountably poor environmental conditions despite abundant water resources. The lack of dense population and stone architecture in this area emphasizes the lack of a simple correlation between cenotes and settlement. This thesis uses GIS analysis to identify and explore such problematic settlement areas to better understand the factors and complexities involved in the more successful settlements of neighboring regions. iv This work is dedicated to my late father, who first introduced me to the Mundo Maya through a visit to the ruins of Tikal at the age of nine, and who instilled in me strength, curiosity, and a love for exploring the world. v ACKLOWLEDGEMENTS I'd like to acknowledge Dr. Arlen Chase and Dr. Diane Chase for providing such outstanding opportunities and instruction, and for leading by example both in the field and in the classroom. Dr. John Walker for his eye-opening perspectives, GIS instruction, inspiring hard-working attitude, and patience in the field. Dr. Clifford Brown and Dr. Walter Witschey for their invaluable correspondence and for their contributions to mapping and GIS data of Maya sites.