揽瓜阁俱乐部第二期 Day9 2020.06.23
【自然科学-环境】 Asia’s hunger for sand is harmful to farming and the environment （854字 精读 必做篇）
The miners usually prefer to work under cover of darkness. This dredger is more brazen. It is not yet sunset when the boat’s crew begin hoovering sand up from the riverbed and pumping it onto a nearby bank, where it will be collected and sold. At least seven barges are doing the same thing on this stretch of the Red River, about an hour’s drive from Hanoi, the capital of Vietnam. Such teams often work without the right permits, but the rewards outweigh the risk. Whereas the average Vietnamese makes $269 a month, miners can earn between $700 and $1,000 for every boatload they scoop up. The teams working here have deposited so much sand on the bank that dunes have formed.
There has probably never been a better time to be in the sand business. The world uses nearly 50bn tonnes of sand and gravel a year—almost twice as much as a decade ago. No other natural resource is extracted and traded on such an epic scale, bar water.
Demand is greatest in Asia, where cities are growing fast (sand is the biggest ingredient in concrete, asphalt and glass). China got through more cement between 2011 and 2013 than America did in the entire 20th century (the use of cement is highly correlated with that of sand). Since the 1960s Singapore—the world’s largest importer of sand—has expanded its territory by almost a quarter, mainly by dumping it into the sea. The OECD thinks the construction industry’s demand for sand and gravel will double over the next 40 years. Little wonder then that the price of sand is rocketing. In Vietnam in 2017 it quadrupled in just one year.
In the popular imagination, sand is synonymous with limitlessness. In reality it is a scarce commodity, for which builders are now scrabbling. Not just any old grains will do. The United Arab Emirates is carpeted in dunes, but imports sand nonetheless because the kind buffeted by desert winds is too fine to be made into cement. Sand shaped by water is coarser and so binds better. Extraction from coastlines and rivers is therefore surging. But according to the United Nations Environment Programme (UNEP), Asians are scooping up sand faster than it can naturally replenish itself. In Indonesia some two dozen small islands have vanished since 2005. Vietnam expects to run out of sand this year.
All this has an environmental cost. Removing sand from riverbeds deprives fish of places to live, feed and spawn. It is thought to have contributed to the extinction of the Yangzi river dolphin. Moreover, according to WWF, a conservation group, as much as 90% of the sediment that once flowed through the Mekong, Yangzi and Ganges rivers is trapped behind dams or purloined by miners, thereby robbing their deltas both of the nutrients that make them fecund and of the replenishment that counters coastal erosion. As sea levels rise with climate change, saltwater is surging up rivers in Australia, Cambodia, Sri Lanka and Vietnam, among other places, and crop yields are falling in the areas affected. Vietnam’s agriculture ministry has warned that seawater may travel as far as 110km up the Mekong this winter. The last time that happened, in 2016, 1,600 square kilometres of land were ruined, resulting in losses of $237m. Locals have already reported seeing dead fish floating on the water.
Nguyen Van Thoan, a farmer whose pomelo orchard lies not far downstream from the barges scouring the Red River, says that 30 years ago a kilometre of land stood between his house and the river. Today only 20 metres separates them. He blames sand-miners. So do the 6,000 fishermen who have had to abandon their coastal villages in the Indian state of Kerala in recent years, after extraction and erosion left them vulnerable to flooding.
Curbing sand-mining is difficult because so much of it is unregulated. Only about two-fifths of the sand extracted worldwide every year is thought to be traded legally, according to the Global Initiative Against Transnational Organised Crime. In Shanghai miners on the Yangzi evade the authorities by hacking transponders, which broadcast the positions of ships, and cloning their co-ordinates. It is preferable, of course, to co-opt officials. Ministers in several state governments in India have been accused of abetting or protecting illegal sand-mining. “Everybody has their finger in the pie,” says Sumaira Abdulali of Awaaz Foundation, a charity in Mumbai. She says she has been attacked twice for her efforts to stop the diggers.
Ms Abdulali is nonetheless “a bit hopeful”. Scientists are experimenting with alternatives to concrete and cement. Architects are trying to find ways to use such materials more sparingly. Even the odd government is taking action. In 2018, Maharashtra passed regulations requiring contractors to use plastic waste as filler when building or repairing roads. Singapore is creating a new patch of land by draining it of water rather than piling it with sand. Kiran Pereira of SandStories.org, which promotes awareness of the issue, says “there are plenty of solutions” if only governments would find the will to implement them. Time to pull heads from the sand.
Source: The Economist
【自然科学-环境】 Stiffer Roads Could Drive Down Carbon Emissions （327字 2分16秒 精听 必做篇）
先做精听再核对原文哦~
When you walk on a sandy beach, it takes more energy than striding down a sidewalk—because the weight of your body pushes into the sand. Turns out, the same thing is true for vehicles, driving on roads.
"The weight of vehicles creates a very shallow indentation or deflection in the pavement. And makes it such that it's continuously driving up a very shallow hill."
Jeremy Gregory, a sustainability scientist at MIT. His team modeled how much energy could be saved—and greenhouse gases avoided—by simply hardening the nation's roads and highways.
And they found that stiffening 10 percent of the nation's roads every year could prevent 440 megatons of carbon dioxide equivalent emissions over the next five decades—enough to offset half a percent of projected transportation sector emissions over that same time period.
To put those emissions savings into context—that amount is equivalent to how much CO2 you'd spare the planet by keeping a billion barrels of oil in the ground. Or by growing seven billion trees, for a decade.
The results are in the Transportation Research Record.
As for how to stiffen roads? Gregory says you could mix small amounts of synthetic fibers or carbon nanotubes into paving materials. Or you could pave with cement-based concrete, which is stiffer than asphalt. (It's worth noting the research was funded in part by the Portland Cement Association.)
This system could also be a way to shave carbon emissions without some of the usual hurdles.
"Usually when it comes to reducing emissions in the transportation sector, you're talking about changing policies related to vehicles and also driver behavior, which involves millions and millions of people. As opposed to changing the way we design or maintain of our pavements. That's just on the order of thousands of people who are working in transportation agencies."
And when it comes to retrofitting our streets and highways—those agencies are where you might say the rubber meets the road.
Source: Scientific American
【笔记格式要求】
精读笔记格式要求： 1.总结文章中心大意 2.总结分论点或每段段落大意 3.摘抄印象深刻或者觉得优美的句子 4.总结文章中的生词 5.记录阅读时间、总结时间、总时间
精听笔记格式要求： 1.逐句听写整篇文章 2.对照原文修改听写稿，标记出错原因 3.总结文章中心大意 4.总结精听过程中的生词 5.记录听写时间、总结时间、总时间
这里也给大家两点学习小建议哦~ 精读：如遇到读不懂的复杂句，建议找出句子主干，分析句子成分，也可以尝试翻译句子来帮助理解~ 精听：建议每句不要反复纠结听，如果听 5 遍都没听出来，那就跳过，等完成后再回听总结原因，时间宝贵，不要过于执着哦~
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发表于 2020-6-22 20:26:34
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