What is a single sample taken without considering the time of day or rate of flow called?

A single sample taken without considering the time of day or rate of flow is referred to as a "grab" sample. This method involves collecting a single sample at one specific moment in time, which means it captures the characteristics of the water at that particular instant. Grab samples are commonly used in various environmental assessments because they can provide immediate insight into the water quality at that moment, although they may not represent fluctuations over time or the overall quality of the water source.

In contrast, composite samples involve aggregating multiple grab samples taken over a period of time or under various conditions to create a more representative analysis. This approach accounts for variations in water quality that may occur due to changes in flow, temperature, or other factors.

Understanding this distinction is essential for interpreting water quality data accurately, as grab sampling provides a snapshot while composite sampling offers a broader picture over time.