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Vehicle pollution 译者：Elizabath DRIVING an electric car confers a badge of greenery, or so the marketing departments of their makers would have you believe. Yet a report which analyses the life cycle of car emissions (ie, all the way from those created by the mining of materials for batteries, via the ones from the production of fuel and the generation of electricity, to the muck that actually comes out of the exhaust) presents a rather different picture. A battery-powered car recharged with electricity generated by coal-fired power stations, it found, is likely to cause more than three times as many deaths from pollution as a conventional petrol-driven vehicle. Even a battery car running on the average mix of electrical power generated in America is much more hazardous than the conventional alternative. 驾驶一辆电动汽车认为是清洁环保的，或者说电动汽车的制造商会以这样说辞来销售。然而，有一家报告分析了汽车排放物的整个周期，结果却不是人们所想的那样（整个过程包括从制造电池产生的污染，经过生产燃料、电能产生的污染到汽车尾气排出的废气）。电动汽车的充电需要火电厂发电提供电能，这种充电方式造成的污染致死人数是传统燃油汽车的三倍还多。在美国，即使电动汽车是混合电能供应也比传统燃油汽车的更加致命。 Christopher Tessum, Jason Hill and Julian Marshall of the University of Minnesota have just published this study in the Proceedings of the National Academy of Sciences. They estimate how levels of fine particulate matter and ground-level ozone—two important constituents of air pollution, which kills more than 100,000 people a year in America—would change if each of 11 ways of powering a car were to be responsible for 10% of the vehicle-miles expected to be driven in America in 2020. 来自明尼苏达大学的克里斯托弗特塞姆、杰森希尔和朱利安马绍尔将他们的研究发表在《美国国家科学院院刊》。他们估计在美国如果使用这十一种供能方式的汽车在2020年行驶里程占到总的车辆行驶里程的10%，细颗粒物和地表臭氧区的等级将会发生变化——细颗粒物和地表臭氧是造成空气污染的两种主要成分，在美国每年有10万人死于空气污染。 It was no surprise that electric cars whose batteries were topped up from wind, solar or hydroelectric sources came out cleanest, causing 231 putative deaths over the course of a year, compared with 878 for petrol cars. Electric cars recharged with power from natural-gas-fired stations were also a lot less lethal than petrol-driven ones, with 439 deaths. But if those same electric cars were recharged ultimately by coal, they would be responsible, according to the model, for just over 3,000 deaths. 电动汽车的电池由风能、太阳能、水力发电充电是最清洁的，这一点并不令人感到惊讶，假定这种情况造成的污染会导致每年有231人死亡，而燃油汽车的数字是878.给电动汽车充电使用的是天然气发电站的话，造成死亡的人数为439人，同样远远少于燃油汽车的。但如果那些电动汽车采用火电发电充电的话，根据预测，死亡人数将会超过3000. Biofuels also caused more health problems than petrol. But diesel, which is generating concern about pollution in parts of Europe, where it is a more popular fuel than in America, was marginally cleaner than petrol. This is because the Minnesota model assumes for all cars that present and future emission-control technologies will be more widely used in 2020, especially particulate filters which have a marked effect on cleaning diesel exhausts. Diesel cars also have better fuel economy than petrol-driven ones. 采用生物燃料充电的话也会优于驾驶燃油汽车。但是柴油在欧洲的部分地区引起了关于污染的担忧，柴油在欧洲要比在美国受欢迎，柴油要稍稍好于汽油。这是因为克里斯托弗特塞姆、杰森希尔和朱利安马绍尔的研究假定对所有汽车来说，现在的或是未来的排放控制技术在2020年会被广泛的使用，尤其是颗粒过滤技术在降低柴油尾气污染方面有着显著的作用。柴油汽车会比汽油汽车拥有更好的燃料燃烧效率。 Overall, the research shows that electric cars are cleaner than those that rely on internal-combustion engines only if the power used to charge them is also clean. That is hardly a surprise, but the magnitude of the difference is. How green electric cars really are, then, will depend mainly on where they are driven. In France, which obtains more than half its power from nuclear stations, they look like a good bet. In China—which is keen on electric cars, but produces some 80% of its electricity from coal—rather less so. 总之，研究显示只有在给电动汽车充电的能源也是清洁的情况下电动汽车要比那些依靠内燃机的汽车更加清洁。这很难算作是惊喜，但是这很重要。电动汽车会有多环保，这可能决定于电动汽车在哪里驾驶。在法国，一半的电能来自于核能，这看起来是一个不错的方法。中国正在大力推进电动汽车，但是80%的电动汽车的电能来自于火电厂发电，还不如不用电动汽车呢。 From the print edition: Science and technology |
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