![]() ![]() Cesium-137 contamination in some Marshallese fruits was higher than in foods affected by the Fukushima and Chernobyl nuclear disasters. But fruits from Bikini Island and Rongelap Island had levels that exceeded limits set by four governments and the International Physicians for the Prevention of Nuclear War. The team found no cesium-137 contamination in fruits from Enewetak and Utirik Atolls, which are both populated. The radioisotope cesium-137 is easily absorbed by food crops, including coconuts and pandanus, both important commercial crops in the Marshall Islands. The team found unsafe radioactivity levels not just in the air, soil, and water but in the fruit, too. Long-lived radioisotopes like plutonium and americium could contaminate the ocean ecosystems for centuries, the team wrote, and could affect coral regrowth and repopulation by bacteria and sea life. The crater from the Castle Bravo explosion is at the northwestern arc of the atoll. Radiation levels for plutonium-239, plutonium-240, americium-241, and bismuth-207 were orders of magnitude higher than background levels.īetween 19, the United States detonated 23 nuclear devices at Bikini Atoll, seen here via satellite. The team collected around 130 sediment cores across the crater. Soils from Majuro Island, the location of the country’s capital and most populous city, did not have any radionuclides, the team found.Īt the bottom of Bravo Crater, which is filling with ocean water, radioisotope contamination is much worse. Soils, Sediments, and SustenanceĬoncentrations of radioisotopes in some soil samples also exceeded government limits on Bikini Island, Naen Island, and Enewetak’s Enjebi and Runit Islands. On Rongelap’s Naen Island they were nearly 3 times the limit. However, levels on Bikini Island were nearly twice the radiation exposure limit for relocation agreed on by the U.S. External gamma radiation levels were low on some islands in Enewetak Atoll and Utirik Atoll. The researchers mapped ambient radiation levels on eight islands in the four atolls. The team also collected samples from nearby “pantry islands” where locals might travel to get fruit or fish, as well as “control” islands farther away from the testing grounds for comparison. “We measured external gamma radiation, soil radioisotope concentrations, cesium-137 levels in food, and radioisotope concentrations in ocean sediment, particularly inside the Bravo Crater,” she said. Enewetak and Bikini Atolls, the sites of many nuclear tests, are toward the northwest. These findings provide a basis for sustainable forest management under global climate change.A map of the islands and atolls of the Marshall Islands. There was no obvious elevation limit for the increase in tree-ring maximum density. As the climate becomes wetter and warmer in the Tianshan Mountains, our results suggest that the radial growth of trees may benefit at elevations above 2400 m a.s.l. At low altitudes, the negative response of tree-ring maximum density to winter precipitation was strengthened, and a stable negative response to July precipitation was observed. The positive response relationship between tree-ring maximum density and the temperature in July weakened over time. In the low-altitude trees, the negative response of tree-ring width to temperature in the growing season was reduced, while the positive response to precipitation in the growing season was enhanced. Moving correlation analysis showed that the positive response of tree-ring width to precipitation in the growing season was enhanced over time at high altitudes. The tree-ring maximum density was positively correlated with temperature and the DTR of the growing season, and negatively correlated with precipitation in winter and growing season. Tree-ring width was positively correlated with precipitation in June and September of the previous year, and May of the current year. At low altitudes, tree-ring width was negatively correlated with temperature in the early growing season and the growing season. Tree-ring width was also positively correlated with precipitation in July of the previous year, and January and July of the current year, and negatively correlated with the monthly diurnal temperature range (DTR). At high altitudes, tree-ring width was positively correlated with temperature in February of the current year. Results showed that altitude affected both tree-ring width and maximum density. ![]() In this study, we collected tree-ring width and maximum density data from nine plots along an altitudinal gradient. schrenkiana) is a unique tree species to this area. ![]() The tree growth–climate relationship remains poorly understood at large spatial scales in the Tianshan Mountains, China. It is crucial, therefore, to investigate the effects of climate change on the radial growth of trees at different altitudes. The effect of global warming on alpine forests is complex. ![]()
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