1 . Conifers (针叶树) are generally better than broad-leaved trees at purifying air from pollutants. But deciduous (落叶的) trees may be better at taking in particle-bound pollution. A new study led by the University of Gothenburg shows that the best trees for air purification depend on the type of pollutants involved.

Trees and other greener in cities provide many benefits that are important for the well-being of residents. Leaves and needled on trees filter air pollutants and reduce exposure to poisonous substance in the air. But which trees purify the air most effectively? Researchers from the University of Gothenburg have collected leaves and needle from eleven different trees growing in the same place in the Gothenburg Botanical Garden (GBG) to analyse which cub-stances they have absorbed.

“This tree collection provided a unique opportunity to test many different species of trees with similar environmental conditions and exposure to air pollutants,” said Jenny Klingberg, a researcher of the GBG

A total of 32 different pollutants were analysed, some of which are bound to articles of various sizes. Others are gaseous. This project has focused on paths (多环芳烃). In cities, traffic is the biggest source of these pollutants, which are released due to incomplete burning in engines.

“Our analysis show that different species of trees have different abilities to absorb air pollutants. Conifers generally absorb morn gaseous paths than broad-leaved trees. Another advantage of conifers is that they also act as air purifies in winter, when air pollution is usually at its highest,” said Jenny Klingberg.

“This study contributes to improving our understanding of the ability of trees to clean the air and which species are best at absorbing air pollutants,” said Jenny Klingberg. This known-edge is important for urban planning when designing sustainable cities. While trees and green-era can contribute to better air quality in cities, at the end of the day, the most important measure is to reduce emissions.

1. Which is the determining factor in choosing the most suitable tries to purify air?

A．Air quality.

B．Geographical location.

C．The height of plants.

D．The kind of pollutants.

2. Why did the researchers collect leaves and needled from GBG?

A．To compare their shapes.	B．To create a tree collection.
C．To figure out what they absorb.	D．To display them on exhibition.

3. What may cause more paths to be released?

A．Fuel vehicle’s.

B．Electric engines.

C．Traffic accidents.

D．Complete burning.

4. What is the most effective way to better air quality in cities?

A．Decreasing emissions.	B．Planting more conifers.
C．Raising public awareness.	D．Designing sustainable cities.

2 . Farms are battlefields, forcing growers to fight against greedy pests and aggressive weeds in never- ending, costly campaigns that often involve chemical weapons. Those weapons also harm innocent bystanders such as bees and fish. Now, a study chart's impressive shifts in recent decades as U. S. farmers have changed their types of pesticides. Birds and mammals have been affected less, whereas pollinators are suffering. The toxic (有毒的) impact on land plants has also increased sharply, likely because farmers are using increasing kinds of chemicals to fight weeds that have become resistant to common herbicides( 除草剂).

As a research shows, in recent decades, the amount of pesticides used in the United States has gone down by about 40% . But active ingredients have become more powerful. For example, fast-acting pesticides are very toxic. Some require as lite as 6 grams per hectare, compared with several kilograms of the older pesticides. Ralf Schulz, an ecotoxicologist, wondered whether overall toxicity in the ecosystem had changed. A few studies had looked at certain compounds and organisms, but nothing had been done on a national scale.

Schulz and colleagues started with U. S. Geological Survey data on self- reported pesticide use by U. s. farmers from 1992 to 2016. They also gathered toxicity data from the U. S. Environmental Protection Agency on those same compounds-381 in all, The good news is that total toxicity decreased more than 95%, for birds and mammals from 1992 to 2016, largely because of the phaseout (逐步停止) of older pesticides. Toxicity for fish declined by less- about one-third.

Schulz hopes more researches will help policymakers and others think more about the complexity of pest and weed control, and wild species, in order to reduce unintentional harm. The rising toxicity in plants could lead to less diverse habitat and food resources that eventually spread to animal populations, potentially causing losses. “The patterns in the U. S. pesticide use and toxicity data should be a warning for the rest of the world, much of which seems to be leaning more heavily on pesticide use rather than ecological interactions for pest control,” Schulz said.

1. What do U. S. farmers usually do to fight against pests and weeds?

A．They change land plants.	B．They use chemical weapons.
C．They harm innocent bystanders.	D．They increase kinds of pollinators.

2. How did Schulz and his coworkers carry out their study?

A．By giving examples.	B．By analyzing data,
C．By doing experiments.	D．By interviewing farmers.

3. Which of the following best describes Schulz's attitude to pesticide use?

A．Subjective.	B．Doubtful.
C．Negative.	D．Favorable.

4. What will happen if toxicity in plants continues to increase?

A．Unintentional harm will be reduced.	B．People will have less food resources.
C．Ecological interactions will increase.	D．The number of animals will decrease.