What is a composite sample?

A composite sample is defined as a mixture of discrete samples collected at different times or from different locations within a given area. This method allows for a more comprehensive assessment of the water quality by averaging the results of multiple samples, thereby minimizing the impact of any anomalies or fluctuations in water quality that may occur at a single point in time or location.

In environmental and water quality testing, collecting composite samples is essential because it reflects the variability of contaminants or parameters over a specified period or across a geographical area. For instance, in monitoring the concentration of a pollutant, a composite sample will help in understanding the overall exposure rather than relying on the results from a single sample that may not represent typical conditions.

The other choices highlight different sampling or preservation techniques, but they do not accurately define a composite sample. A single sample from different locations indicates samples taken at the same time rather than a mixture over time, a sample preserved at cold temperatures refers to specimen conservation methods, and a filtered sample relates to a process used to remove particulates from a sample prior to analysis. Each of these factors plays a role in water quality measurement but does not encompass the concept of a composite sample.