Passage 2: The Transportation Revolution
P1: When most people think or talk about dangers to our environment, they focus on general terms like “pollution, “smog,” and “acid-rain.” Also, they .often focus on the impact of supposedly man-made chemicals and compounds. But to truly understand the risks to our environment, it’s helpful to focus on the danger of specific chemicals, which are often otherwise naturally-occurring elements that have been spread harmfully by man. One of the largest threats to our environment is mercury: Hg on the periodic table of elements.
P2: At room temperature, mercury, a metal, exists as a silvery-white liquid. However, it vaporizes readily when heat is applied, and can stay suspended in the air for more than a year. The largest sources of mercury pollution in the United States are coal-fired power plants. Emissions from these plants account for 70 percent of the mercury that enters our oceans, lakes, and streams. Air currents carry these particles far from the source and are capable of polluting bodies of water thousands of miles away.
P3: Mercury particles released into the air fall into these waterways and quickly enter aquatic food chains. First, mercury attaches to sediments (fragments of organic and inorganic material that settle to the bottom of the body ofwater). Second, bacteria change the mercury into methyl mercury, a highly toxic substance. Third, phytoplankton feed on the organic matter in sediments and absorb the methyl mercury. Fourth, fish then eat the mercury-contaminated phytoplankton; the larger the fish and the longer it lives, the more concentrated the methyl mercury in its system becomes. The mercury can then move higher up the food chain when humans eat fish that have absorbed high amounts of mercury.
- TOEFL IBT Reading Practice Test 51 from The Official Guide to the TOEFL Test
- TOEFL IBT Reading Practice Test 41 from The Official Guide to the TOEFL
- TOEFL IBT Reading Practice Test 40 from The Official Guide to the TOEFL
- TOEFL IBT Reading Practice Test 39 from The Official Guide to the TOEFL Test
- Reading Practice Test 69 from The Collection of TOEFL Reading Comprehension
P4: Studies indicate that mercury levels in U.S. waterways have increased anywhere from 100 to 400 percent over the course of the last century, and no river, lake, or ocean seems immune. It Is important to note that, thanks to the U.S. Clean Air Act and efforts by industry to curb unnecessary discharges as well as better sewage treatment methods, the levels have been in slow decline since the 1970s. However, this minor decline is relatively miniscule in comparison to the major increase in the years prior.
P5: If you’ve ever experienced that “rotten egg” smell during low tide at a coastal area, you’ve seen (or smelled) méthylation in action. Méthylation is the conversion of mercury in sediments to methyl mercury by sulfate-reducing bacteria. While this méthylation is a natural process, the industrial discharge of mercury has greatly accelerated the process beyond what the ecosystem is able to absorb safely. This méthylation not only Impacts aquatic species, but also harms humans and other land-based wildlife.
p6: Most of the fish and selfish that humans eat live solely in coastal areas or frequent coastal areas and feed on the fish that live there. At the same time, most méthylation takes place in coastal areas. Therefore, methyl mercury moves up the food chain from plankton to lobster, bluefish, winter ffounder, tuna, and many other species eaten extensively by man. The methyl mercury binds to the protein in fish, residing in the muscle of the fish. This muscle is exactly what we eat: the fillet.
p7: The short-term impact of digestion of toxic methyl mercury is obviously a concern. A More troubling, however, is its long-term impact on species up and down the food chain, B In Wisconsin, scientists have studied the decline of chick production in loons (aquatic birds), C They have made a positive link to mercury concentration in eggs which exceeds the concentration found to be toxic in laboratory studies, D Through that example, the lasting impact of methyl mercury far from the source of the pollution can be seen.
p8: One of the great wonders of the Earth is the interconnectivity of all the world’s ecosystems. This Interconnectivity gives us the range and diversity of wildlife that we all enjoy and it also allowed life on the planet to endure through cataclysmic events, such as asteroid impacts and the ice ages. However, it is this very interconnectivity that makes our ecosystems so vulnerable. Mercury pollution is unfortunately one of many examples of an environmental impact far removed from the source of the pollution; understanding the process by which the pollution spreads up the food chain is one of many steps to ameliorate the impact of such pollution.
Directions: Mark your answer by filling in the oval next to your choice.
13. The word applied in the passage is closest in meaning to
14. According to paragraph 2, what accounts for 70% of toxic mercury pollution?
(A) Air currents
(C) Coal-fired power plants
(D) A silvery-white liquid
15. In paragraph 3, what does the author say about the role of phytoplankton in the spread on mercury throughout the food chain?
(A) It transforms mercury to methyl mercury.
(B) It provides the link between the methyl mercury in sediments and fish.
(C) It reduces the impact of methyl mercury on the coastal ecosystem.
(D) It concentrates the mercury making it less toxic.
16. The word concentrated in the passage is closest in meaning to
17. Which of the following can be inferred from paragraph 4 about the U.S. Clean Air Act?
(A) It was aimed to increase air pollution
(B) It existed prior to the effects of pollution on the environment were known.
(C) It was part of the reason industries reduced harmful emissions into the air.
(D) It has been unsuccessful in slowing air pollution.
18. All of the following are mentioned in the passage as reasons why mercury levels in the environment have been in slow decline since the 1970s EXCEPT
(A) the Clean Air Act
(B) reduction in sulfate-producing bacteria
(C) better sewage treatment
(D) changes in industrial practice
19. According to paragraph 6, coastal areas are the locations for most
(C) mercury pollution sources
20. The word its in the passage refers to
(A) long term impact
(B) methyl mercury
(C) food chain
21. Which of the following is mentioned in i paragraph 7 as one of the long-term impacts of methyl mercury pollution?
(A) Increase in sulfate-reducing bacteria in sediment
(B) Reduction in the number of fish in coastal areas
(C) Danger to the reproductive cycle of birds
(D) Concentrated mercury in lobsters
22. According to paragraph 8, the inter-connectivity of the Earth’s ecosystems is also
(A) the reason the ecosystems are so susceptible to pollution
(B) the cause of mercury pollution
(C) the reason methyl mercury is such a harmful substance
(D) the cure for pollution from coal-fired power plants
23. The word ameliorate in the passage is closest in meaning to
24. Look at the four squares cc that show where the following sentence could be inserted in the paragraph below.
“Thus, the harmful effects of methyl mercury are passed from adult to young and will impact the health of the species for years to come.“
The short-term impact of digestion of toxic methyl mercury is obviously a concern. A More troubling, however, is its long-term impact on species up and down the food chain, B In Wisconsin, scientists have studied the decline of chick production in loons (aquatic birds), C They have made a positive link to mercury concentration in eggs which exceeds the concentration found to be toxic in laboratory studies, D Through that example, the lasting impact of methyl mercury far from the source of the pollution can be seen.
25. Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.
Mercury pollution is one example of a type of pollution that has shor term and long-term effects far from the source of the pollution.
(A) Air currents carry Mercury particles far from the source and are capabJe of polluting bodies of water thousands of miles away.
(B) Mercury is transformed into the toxic methyl mercury and moves up the food chain to cause harm for organisms at every level all the way up to humans.
(C) Sulfate-reducing bacteria cause the “rotten egg” smell that exists at coastal areas during low tide.
(D) Mercury pollution is increasing in the United States despite the U.S. Clean Air Act and efforts of industry.
(E) The methyl mercury binds to the protein in fish, residing in the muscle.
(F) The harmful effects of methyl mercury are passed from adult to young and will impact the health of many species for years to come.