2016考研英语阅读每日精选：湿地可长期吸收硝酸盐

考研网

在考研英语中，阅读分数可谓是占到了总分的半壁江山，正所谓“得阅读者得考研”。对于备考2016考研的同学们，在平时的复习中一定要拓展阅读思路，各类话题都要关注，这样才能在整体上提升考研英语阅读水平!新东方在线分享《2016考研英语阅读精选》，一起来学习吧!
    　　湿地可长期吸收硝酸盐
    Wetlands created 20 years ago between tile-drained agricultural fields and
the Embarras River were recently revisited for a new two-year University of
Illinois research project. Results show an overall 62 percent nitrate removal
rate and little emission1 of nitrous oxide2, a potent3greenhouse gas. "Slowing
down the rate of flow of the water by intercepting4 it in the wetland is what
helps to remove the nitrate," says Mark David, a University of Illinois
biogeochemist in the College of Agricultural, Consumer and Environmental
Sciences. "The vegetation that grows in the wetland doesn't make much of a
difference because the grasses don't take up much nitrogen. It's just about
slowing the water down and allowing the microbes in the sediment5 to eliminate
the nitrate. It goes back into the air as harmless nitrogen gas."
    David was involved with research on these same wetlands from 1994-98 but
didn't take any measurements after that. He has spent much of his career
studying the runoff from tile-drained fields and methods to reduce losses of
nitrate and phosphorus. The runoff, particularly nitrate, from fields in the
upper Mississippi River basin, is believed to be the major cause of the hypoxia
in the Gulf6 of Mexico.
    "The USDA requested proposals on the effectiveness of wetlands and woodchip
bioreactors to reduce nitrate losses from fields, but was also concerned about
greenhouse gas emissions7," says David. Working with graduate student and lead
author Tyler Groh, "We found the greenhouse gas emissions were really quite low.
Nitrous oxide was not a problem. The other good news is that this research
confirms that wetlands really do work to reduce nitrate runoff, and they work
long term."
    David says that, along with fertilizer management, cover crops, and
bioreactors, wetlands are an integral part of the Illinois Nutrient8 Loss
Reduction Strategy. Building a wetland costs about the same as installing a
bioreactor.
    One of the reasons David prefers wetlands to help solve the nitrogen
pollution problem is that they work reasonably well in the winter when the water
temperatures are low.