Human activities are making the globe saltier, specifically in our soils, fresh water and air, according to a study released this week in the journal Nature Reviews Earth & Environment.
Salt pollution isn’t some flashy threat to our existence — like, say, a meteor hitting Earth — but the issue is gravely overlooked and is a “sleeping giant”, said Sujay Kaushal, lead author of the study. Over the past 50 years, salt have increased in streams and rivers as people have begun using and producing more salts. The team found that across the globe, about 2.5 billion acres of soil — an area about the size of the United States — have become saltier.
Most people think of salt as the white specks we put in our food or the salt in the oceans, chemically known as sodium chloride (NaCl). That sodium salt can also be found in detergents (去污剂), other household products and more, but there are many different salts, including calcium, magnesium and other ions used in additional products — and they’re all increasing in places where they don’t normally occur.
Salt is a natural and necessary component of Earth. The compound is brought to the surface slowly over long geological time scales, through natural processes such as weathering of sedimentary (沉积而成的) rocks. When exposed at the surface, the salt can mix with water, be transported into water or go into the air. Living organisms, from plants to people, take up small portions to help regulate daily functions. Excess salt hitches a ride with water molecules, entering soil and the oceans. But human activities have altered this normal salt cycle in recent decades, the team found. Agriculture, mining, construction, water and road treatment, and other industrial activities are increasing the salt in our ground, freshwater systems and air.
Before this study, scientists didn’t really know how much humans were changing salt concentrations around the globe. But the “magnitude to which we have altered one of Earth’s natural cycles is alarming,” said ecologist Bill Hintz, who was not involved in the research. He agreed with the study’s authors that these changes to the salt cycle are an existential threat to freshwater supplies.
【小题1】The underlined word “flashy” in Paragraph 2 can best be replaced by ________.| A．instant | B．serious | C．damaged | D．unsolved |
| A．People can only have access to sodium salt in daily life. |
| B．People intend to have a limited insight into salt. |
| C．Additional products are supposed to be banned. |
| D．Salts are increasing in the world scale. |
| A．Forming as a compound — weathering of sedimentary rocks — consumed by living organisms |
| B．Coming into being in Earth naturally — being brought to the surface — combining with water — entering soil and oceans |
| C．Coming into being in Earth naturally — being transported to water and air — increased by human activities |
| D．Forming as a compound — removing excessive salt — entering soil and oceans |
| A．Inefficient. | B．Unreliable. | C．Brain-washing. | D．Ground-breaking. |
