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  3. On 28 March, scientists got a whiff of something strange in the air off a pier in San Diego, California. The atmosphere had sudd

On 28 March, scientists got a whiff of something strange in the air off a pier in San Diego, California. The atmosphere had sudd

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问题     On 28 March, scientists got a whiff of something strange in the air off a pier in San Diego, California. The atmosphere had suddenly become flush with radioactive sulfur(a light-yellow non-metallic solid)atoms. That sulfur, it turns out, had traveled across the Pacific from a nuclear power plant in Fukushima, Japan, that was shaken by the 11 March earthquake and the tsunami and aftershocks that followed. Now the same team has studied those radioactive winds to come up with the first estimate of damage to the plant’s cores at the height of the disaster.
    To cool fuel rods and spent fuel while stanching a total meltdown, responders pumped several hundred tons of seawater into three reactors at the Fukushima Dai-ichi nuclear power plant. The white-hot rods fizzled off steam, which had to go somewhere. So workers vented it into the air.
    Meanwhile, across the Pacific, atmospheric scientist Antra Priyadarshi of the University of California, San Diego(UCSD), remembered a study she had read a while back: Following underwater nuclear bomb tests in the 1950s and 60s, physicists noticed that a heavy form of sulfur—sulfur-35—had mushroomed. Nuclear reactions spit out lots of fast and therefore "hot" particles called neutrons, which can then bang into abundant chloride ions in saltwater, converting them to sulfur-35. Priyadarshi and her colleagues were already tracking tiny traces of radioactive sulfur to study how layers of air mix in the atmosphere, so all they had to do was wait.
    They didn’t have to wait long. The sulfur was already swirling over Fukushima, where it had combined with oxygen to form sulfur dioxide gases and fine particles of sulfates called aerosols. Soon, strong winds pushed them west. Sulfur-35 does occur naturally—cosmic rays zap argon atoms in the upper atmosphere, or stratosphere, to make radioactive sulfur. But little of it makes its way down to the lowest slice of atmosphere, called the marine boundary layer. On a normal day, Priyadarshi sees between 180 and 475 sulfur-35 atoms as sulfates per cubic meter of air, but on the 28th, her team recorded about 1500. "No one has ever seen such a high percentage of the stratospheric air coming into the marine-bound layer," she says.
    The UCSD team ran a computer simulation to trace the path of the gases and aerosols from Fukushima to the West Coast. Most sulfur -35 atoms likely dispersed or rained down into the sea before hitting San Diego, but Priyadarshi estimates that about 0.7% completed the trip, too few to become harmful. Based on the simulation, about 365 times the normal levels of radioactive sulfates had gathered over Fukushima during the disaster.
    Now that Fukushima’s reactors have cooled back down, the biggest challenge facing scientists will be to contain radioactive elements that escaped during the disaster. Mark Thiemens, the study co-author, an atmospheric scientist who is also at UCSD, will be working with Japanese researchers to follow sulfur-35’s path through soil and streams near Fukushima to find where even more harmful elements may have hidden.
Priyadarshi’s comment on sulfur-35’s appearing into the marine boundary layer implies that
选项 A、natural sulfur-35 can also be found in the air above the sea.
B、the nuclear accident in Japan was its direct maker.
C、man-made sulfur-35 can exist in all layers of atmosphere.
D、natural sulfur-35 usually exist in all layers but the marine boundary one.
答案B
解析 推理判断题。根据题干关键词the marine boundary layer定位到第四段第四、五句。由这两句可知，硫一35确实是自然形成的——大气层上部或平流层的宇宙射线轰击氩原子产生放射性硫。但几乎没有放射性硫到达被我们称为海洋边界层的大气最低层。由此可推断，日本核事故应是导致硫一35出现在海洋边界层的直接原因，因此[B]正确。[A]与原文意思相反；[C]中人造硫一35在原文中并未讨论，故排除；[D]的说法过于绝对，原文只说天然硫一35存在于大气层上部，故排除。
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