What is a disadvantage of composite sampling?

Composite sampling involves collecting multiple samples over a period and combining them into a single sample for analysis. This method can be advantageous for obtaining an average concentration of constituents over time; however, it comes with specific limitations.

One significant disadvantage is that composite sampling may fail to detect intermittent peaks or excursions in contaminant levels. For example, if a contaminant spikes due to a specific event or temporary condition, this peak can be diluted when combined with other lower-concentration samples. As a result, the analysis may not accurately represent the true conditions or contaminant levels at the time of the spike, leading to an incomplete understanding of the water quality. This effect is particularly critical in wastewater treatment scenarios where fluctuations in pollutant concentrations are common.

In contrast, other options describe characteristics that either support the utility of composite sampling or do not adequately address its limitations. For instance, while composite sampling may be efficient or quick, these qualities do not negate its primary disadvantage related to detecting significant variations in contaminant levels.