Because the real quench distance is only the minimum figure @ TDC (which is not the point of maximum risk), and there is measurable pumping loss getting those few molecules in and out of that small space, and as the clearance expands the loss is reduced.
Why is nonpoint source pollution potentially more harmful than point source pollution? a. Nonpoint source pollution disrupts the water cycle. b. Nonpoint source pollution is difficult to regulate. c. Nonpoint source pollution comes from more than one source. d. Nonpoint source pollution is more damaging to living organisms than point source pollution. Nonpoint source pollution generally results from land runoff, precipitation, atmospheric deposition, drainage, seepage or hydrologic modification.
Categories of Pollution: Nonpoint Source. Nonpoint source pollution is difficult to control because it comes from many different sources and locations. Motor oil and other oil-based chemicals can be recognized by a characteristic rainbow-colored sheen. Click on image for larger view. Most nonpoint source pollution occurs as a result of runoff. When rain or melted snow moves over and through the ground, the water absorbs and assimilates any pollutants it comes into contact with (USEPA, 2004b).