Passage VI

A study was done in a large city in Asia during the spring to examine the composition of airborne dust parti­cles on 5 days of fair weather and on 5 days of dust storms. There was no precipitation on any of the study days.

Study

A device called an impactor (see Figure 1) was installed on the roof of a 4-story building in the center of the city. To collect airborne, dust particles, the impactor drew in air at a constant rate of 1.1 L/min. A series of 8 filters inside the impactor removed particles from the air. Each filter had openings of a different uniform diameter to allow for the collection of particles belonging to 1 of 8 dif­ferent size ranges, measured in micrometers (µm).

On each of the selected days, the impactor was oper­ated continuously over a period that began at 9 a.m. At 3 p.m., the impactor was turned off, and the collected parti­cles belonging to each size range were removed and then analyzed for 4 elements: silicon (Si), iron (Fe), sulfur (S), and copper (Cu). The average concentration of each element, in micrograms per cubic meter of air (µg/m3), for the fair weather days and for the dust storm days are shown in Figures 2 and 3, respectively, for each size range.

Figures 2 and 3 adapted from Renjian Zhang et al., “The Elemental Composition of Atmospheric Particles at Beijing during Asian Dust Events in Spring 2004." ©2010 by the Taiwan Association for Aerosol Research.

34. Consider the results of the study for the dust storm days. Did the larger dust particles (>2.0 μm) or the smaller dust particles (<2.0 μm) have the greater average concentrations of Si and Fe, and did the larger dust particles or the smaller dust particles have the greater average concentrations of S and Cu ?

Answer and Explanation

Your Answer is

Correct Answer is G

Explanation

Looking at the first picture of figure 3, it can be generally found that when the abscissa dust particle size range is larger, the average concentration of Si and Fe is larger;

Look at the second picture of figure 3 As shown in the figure, it can be seen that when the abscissa dust particle size range is larger, the average concentration of S and Cu is smaller;

So the G option is consistent