Which statistical sampling method is used to sample small, localized areas with high contaminant concentrations and a known history?

• A. Simple random
• B. Stratified random
• C. Systematic grid
• D. Hot spot sampling

Answer: (D)

When you have small, localized areas with high contaminant concentrations and a known history, the sampling approach is to target those exact spots to quickly and efficiently characterize the most impacted zones. Hot spot sampling focuses on sampling small, localized areas where contaminants are concentrated, using prior data to guide where to sample and how intensively. This concentrates effort where it matters most, yielding information about peak levels, the extent around the hotspots, and associated risk without wasting resources on areas unlikely to be contaminated.

Simple random sampling would spread samples across the entire area without prioritizing known hotspots, risking missed peaks. Stratified random sampling divides the area into subareas but doesn’t inherently prioritize hotspots unless those zones were predefined as strata, and even then it still spreads effort across strata. Systematic grid sampling covers the area evenly in a grid, which is good for uniform conditions but not optimal when the goal is to understand high-concentration zones based on history.

So, targeting small, localized, historically known hotspots is the most appropriate approach.