Passage V
In wetlands, the herbicides atrazine and alachlor are removed from the water by plant uptake or by adsorption onto soil particles and subsequent bacterial decomposition. Atrazine can also spontaneously break down to form deethylatrazine (DEA).
Three pairs of herbicide-free wetlands were established for a study: open water (O1, O2), submergent (S1, S2), and emergent (E1, E2), as described in Table 1. On 1 day, atrazine was added to O1, S1, and E1 and alachlor was added to O2, S2, and E2 to produce an initial herbicide concentration of 25 g/L in the water in each wetland. Atrazine, alachlor, and DEA concentrations in the water were measured at intervals over the next 120 days (see Figures 1-3).
25. According to Figure 1, 50 days after atrazine was added, its concentration in the water in S1 compared to its concentration in the water in E1 was about:
Your Answer is
Correct Answer is C
Explanation
Look at figure 1, when the abscissa days is 50, the ordinates of S1 and E1 are about 16 and 9 respectively, so S1 is 7 more than E1