The sediment from presedimentation systems can be kept if samples are collected _________.

• A. Through core sampling
• B. Randomly throughout the basin as grab samples
• C. As composite sampling throughout the basin
• D. And vacuum sealed in glass containers

Answer: (A)

Preserving sediment integrity during sampling relies on keeping the vertical layering intact. A core sample captures a continuous column of sediment, preserving the depth relationships and deposition history in one piece. This minimizes disturbance and prevents mixing of different layers, so analyses reflect what’s actually present at each depth.

In contrast, grabbing random surface material (grab samples) or combining material across the basin (composite samples) would mix layers and erase depth information, giving a biased view of sediment characteristics. Vacuum sealing after collection helps keep the sample stable, but it doesn’t address the disturbance that can occur during collection itself.