Today’s ACT question of the day is an exciting science question about this graph:
Let’s pause to note the axes: concentration on the x-axis and sediment depth on y.
This graph corresponds to one of the elements in this chart:
| Depth (cm) |
Temperature (oC) |
pH | Concentration in sediment (ppm) | |||||
| SO42– | S2– | CO2 | Fe3+ | Fe2+ | O2 | |||
| 0 | 4 | 7.0 | 7.0 | 0.0 | 1.0 | 4.0 | 0.5 | 2.0 |
| 5 | 5 | 6.5 | 5.0 | 2.0 | 1.5 | 3.0 | 1.5 | 1.0 |
| 10 | 7 | 6.0 | 3.5 | 3.5 | 2.0 | 2.0 | 2.0 | 0.0 |
| 15 | 9 | 5.5 | 3.3 | 3.8 | 3.0 | 0.8 | 3.8 | 0.0 |
| 20 | 10 | 5.0 | 3.0 | 4.0 | 1.0 | 0.5 | 4.0 | 0.0 |
The thing I notice first is that the element depicted in the graph has a concentration of 1 at both 0cm and 20cm. Only CO2 matches that pattern. As a final check, CO2 has a max concentration of 3 at 15cm – this fits the graph perfectly. H, CO2, is the answer.