首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
Fertilizer use has exploded, overloading plants worldwide, likely altering ecosystems for decades to centuries, scientists repor
Fertilizer use has exploded, overloading plants worldwide, likely altering ecosystems for decades to centuries, scientists repor
admin
2016-12-18
48
问题
Fertilizer use has exploded, overloading plants worldwide, likely altering ecosystems for decades to centuries, scientists report Thursday. In the journal Science, a review led by Donald Canfield of the University of Southern Denmark found that fertilizer use worldwide increased 800% from 1960 to 2000. "Given the rising costs of synthetic fertilizer production, this overuse is not only economically expensive, but also initiates a series of large-scale environmental impacts," says the review.
Fundamentally, nitrogen from fertilizers has led to an explosion in "dead zones" in seas and oceans, upsetting a cycle of nutrients balanced with growth that has lasted for billions of years, the authors find.
As well, the excess nitrogen is forming large amounts of nitrous oxide(一氧化二氮), a powerful greenhouse gas in wetlands, adding to climate change. Agriculture today produces about a quarter of the nitrous oxide in the atmosphere.
"The effects of humans have been profound. In the last few decades we have doubled the worldwide biological availability of nitrogen, an element that often limits growth of plants and algae," says Thomas Jordan of the Smithsonian Environmental Research Center in Eclgewater, Md., who was not part of the review. The review, "is a very careful analysis of the nitrogen cycle by three of the world authorities in this area," says biochemist Robert Blankenship of Washington University in St. Louis, who also was not part of the review. "The concerns they raise for how the nitrogen cycle is now significantly out of balance are important and need to be addressed by changing agricultural practices. The world’s food supply depends directly on nitrogen application in the form of fertilizer, but current practices are such that much of the applied nitrogen ends up in rivers and eventually in the ocean where it causes serious problems."
"Natural feedbacks driven by microorganisms will likely produce a new steady state over time scales of many decades," say the review authors. "However, because of the projected increase in human population through at least 2050, there will be demand for an increase in fixed nitrogen for crops to feed this population." And that will mean a lot more dead zones, they warn, like the one that blooms yearly, in 2010 about the size of New Jersey, in the Gulf of Mexico.
"Several new approaches and a much wider use of more sustainable time-honored practices, however, can decrease nitrogen use substantially," they conclude. The rising cost and environmental toll of fertilizers will increase demand for less use on farms, they add. "However, even with management, the future cycle will likely be different from the one that preceded the Industrial Revolution."
According to Robert Blankenship, the nitrogen cycle is out of balance because______.
选项
A、nitrogen is applied in the form of fertilizer
B、much nitrogen ends up in seas and oceans
C、food supply depends directly on nitrogen
D、much nitrogen is applied in agriculture
答案
B
解析
第3段倒数第2句末尾的并列句and need to be addressed by changing agricultural practices表明氮循环的不平衡是因为agricultural practices不当所致,最后一句中的but current practices are such that…可知问题在于“大多数的氮渗入了河流中,最后流入大海”,这就是导致氮循环失衡的原因。因此,本题应选B.
转载请注明原文地址:https://kaotiyun.com/show/jXF7777K
0
大学英语六级
相关试题推荐
黄龙风景区位于四川省西北部,是由众多雪峰和中国最东部的冰川组成的山谷。在这里人们可以找到高山景观和各种不同的森林生态系统,以及壮观的石灰岩构造、瀑布和温泉。黄龙风景名胜区处于三大地质构造单元的结合部,地理状况特别复杂。整个风景区总面积约1340平方千米,
随着经济的高速发展和综合国力的增强,中国在世界上影响日益增大。2008年北京举办奥运会,2010年上海举办世博会(WorldExpo),这意味着有几千年历史的中国,正以前所未有的广度和深度向世界各国开放,并从各个方面融入国际社会。在这样一个历史性的时刻,
二十四节气(24solarterms)是统称,包括十二节气(12majorsolarterms)和十二中气(12minorsolarterms),它们彼此之间相互关联。二十四节气反映了天气变化,可以指导农业耕作,也影响着人们的生活。春秋战国时
Howmanytimeshaveyouheardtheexpressionthatmostpeoplespendmoretimeplanningtheirvacationthantheydoplanningthei
"Blink"Technology[A]Tiredofallthattime-consumingswiping?Creditcardsusing"contactless"technologyallowuserstopay
A、Itshowswhereadvertisementscomein.B、Itgivesasignalforhimtoslowdown.C、Italertshimtosomethingimportant.D、It
A、Theyhadconfidenceinhisnewideas.B、Theytrustedhiscomputerexpertise.C、Theywereverykeenonnewtechnology.D、Theyb
A、Whentheyseethesteamandiceinthetank.B、Whentheyseetheactorsfillingthecontainers.C、Whentheyseetheactorsput
A、Thefoodintherestaurantwasdelicious.B、Shewasnotsatisfiedwiththerestaurant.C、Therestaurantleftagoodimpression
A、Theyproducegreenhousegasesbyburningfuels.B、Theypollutetheenvironmentbycuttingplants.C、Theyaddmoreandmorewas
随机试题
使用千斤顶时的注意事项有哪些?
以下属于固定成本的有()
其证候是其治疗方药
郁金的功效是()栀子的功效是()
某安装公司在南方沿海承担了一化工装置的安装工作,该装置施工高峰期正值夏季,相对湿度接近饱和。该公司建造了临时性管道预制厂房,采用CO2气体保护焊进行焊接工作。根据装置内管道的特点,项目部技术人员确定了管道预制程度为30%,制定了一条直管段配焊一个管件(弯头
海关可以在境内获得的数据资料为基础估定进口货物的完税价格,但下列价格不得使用的有()。
若从成长发育角度收集临床资料,则关注点在于求助者的()。
不属于陈鹤琴具体的课程编制方法是()。
设随机变量(X,Y)的概率密度函数为f(x,y)=Ae-ax2+bxy-cy2,一∞<X,y<+∞.若.求P{Y≤1|X≤1}
WorkingMothersCarefullyconductedresearchesthathavefollowedthechildrenofworkingmothershavenotbeenabletoshow
最新回复
(
0
)