Time proportional and flow proportional sampling are two types of which kind of samples?

• A. Grab sample
• B. Spot sample
• C. Composite
• D. Continuous sample

Answer: (C)

Composite sampling aims to create one representative sample by combining multiple sub-samples. Time-proportional sampling collects sub-samples at regular time intervals, so the overall final sample reflects changes that occur over time. Flow-proportional sampling collects sub-samples in amounts that correspond to the flow rate, giving more weight to periods with higher flow so the final composite represents the actual material entering or leaving the system. When these sub-samples are mixed, you get a single composite sample that captures variability and fluctuations, which a single grab or spot sample would miss. A grab or spot sample is just one moment's sample, while a continuous sample describes drawing material continuously rather than forming a single consolidated composite.