What is the definition of a composite sample?

• A. A mixture of many discrete samples forming an average concentration for the area
• B. A single sample from one spot
• C. A sample sorted by size
• D. A sample measured by infrared

Answer: (A)

A composite sample represents an average concentration across an area by combining multiple discrete samples. In environmental sampling, you take several grab samples from different locations or times and pool them into one combined sample, which smooths out local variations and yields a single value that reflects the overall conditions of the area. This matches the idea of mixing many discrete samples to form an average concentration for the area.

A single sample from one spot would not capture spatial variability and is simply a grab sample. A sample sorted by size pertains to separating material by particle size, not combining samples from multiple locations. A sample measured by infrared describes the measurement technique, not how the sample was collected or combined.