Which device is used to collect a composite sample by combining multiple samples over time or from different locations?

• A. A weighted bottle sampler.
• B. A Whirl-Pak bag.
• C. A sample made by combining multiple samples collected over time or from different locations.
• D. A Cubitainer.

Answer: (C)

The key idea is composite sampling, which pools several smaller samples into one to represent a whole period or area. This approach smooths out short-term fluctuations and gives an overall picture of water quality over time or across locations. The best choice describes the end product of that process—a single sample formed by combining multiple individual samples collected over time or from different sites. In practice, you collect the sub-samples and then merge them into one container to analyze as a composite sample.

The other devices serve different purposes: a weighted bottle sampler is used to collect discrete samples at specific times or depths, a Whirl-Pak bag is simply a storage container for portions, and a Cubitainer is a portable container for transporting liquids (it can hold a composite sample, but it isn’t the device that performs pooling).