Hyperlink 6. Why Can Spatially Close Samples Be So Different?

The nature and extent of contamination gets more complicated as time progresses and transport mechanisms change the distribution. Over the years, contaminants can be moved around by wind, flowing water, and disturbance of the soil during construction or landscaping activities. Even ecological receptors may change the pattern of contamination. For example, large and small animals and insects burrow or otherwise disturb soil. By their activities, they can take contaminated surface soil down vertically and bring cleaner subsurface soil to the surface or vice versa. It is not hard to imagine that the concentration of a small scoop of soil from one spot can differ greatly from the concentration of another small scoop taken yards, feet, or even just inches away.