What is the typical concentration trend of carbon dioxide (CO2) in sediments as depth increases?

• A. Consistent throughout sediment depths
• B. Increases significantly with depth
• C. Decreases as depth increases
• D. Fluctuates with sediment types

Answer: (C)

Carbon dioxide (CO2) in sediment typically exhibits a concentration trend that decreases as depth increases. This is primarily due to the biological processes occurring at or near the sediment surface. In shallow layers, organic matter decomposes, resulting in the release of CO2. However, as you move deeper into the sediment, the availability of organic material diminishes, which leads to lower rates of microbial activity and, consequently, lower concentrations of CO2.

Additionally, deeper sediment layers are often more compact and may experience different geochemical processes that can further contribute to the reduction of CO2 levels. Therefore, the observed trend is a decrease in CO2 concentration with increasing sediment depth, reflecting the relationship between biological activity, organic matter decomposition, and sedimentary processes.