In what scenario is composite sampling not ideal?

Composite sampling involves combining multiple discrete samples taken over a period of time or space into a single sample for analysis. This method is particularly useful in providing an average concentration of contaminants across a given timeframe or area. However, it is not ideal in scenarios where conditions can fluctuate dramatically, such as during slug dumps in an industrial process.

Slug dumping refers to the sudden release of a concentrated volume of contaminants into a system, which can lead to spikes in pollutant concentrations that may not be accurately represented by a composite sample. If a composite sample is taken during such an event, the resulting analysis may be skewed, leading to inaccurate assessments of pollution levels and compliance with environmental regulations. Therefore, discrete sampling before, during, and after a slug dump is more appropriate to capture the variability of the contaminant concentrations accurately.

In contrast, analyzing drinking water, dealing with stable-flow processes, and collecting samples from a river typically involve more consistent conditions, making composite sampling more suitable in those scenarios, as it can provide a fair representation of the contaminant levels across a more stable environment.