Passage V
Nutrients in seawater are removed by phytoplankton and other marine organisms. Figure 1 shows the concentrations of 3 nutrients—nitrate (NO3—), dissolved inorganic phosphorus (DIP), and silicic acid(H4SiO4)—at various depths in the Atlantic, Pacific, and Indian Oceans. Table 1 shows the average concentrations and the estimated residence times (how long an ion or molecule of a nutrient remains in the ocean) for the 3 nutrients in deep (> 3 km) Atlantic and Pacific waters. Figure 2 shows how the NO3— concentration in Pacific surface waters (< 0.3 km depth) varies with latitude.
Figure 1 adapted from J. Andrews, P. Brimblecombe, T. Jickells, and P. Liss, An Introduction to Environmental Chemistry. @1996 by Blackwell Science Ltd.
Figure 2 adapted from James Murray et al., "Physical and Biological Controls on Carbon Cycling in the Equatorial Pacific." @1994 by the American Association for the Advancement of Sclence.
27. According to Table 1, an ion of NO3— would remain in the ocean, on average, approximately how many times longer than a molecule of H4SiO4?
Your Answer is
Correct Answer is C
Explanation
Look at table 1, directly divide the residence time of NO3- by the residence time of H4SiO4 Residence time is enough. 57000÷20000=2.85, the 3 times of option C is the closest