21.   This all occurs naturally, but the researchers say that in recent years the problem has gotten worse as the amount of agricultural runoff has increased.

22.   This land would be useful for cleaning polluted agricultural runoff and storing water for later release into the Everglades.

23.   White truffles are exquisitely sensitive to pollution, so agricultural runoff, highways and development must be kept far from the truffle bed.

24.   With that muddy water, contaminated by industrial discharge, agricultural runoff, clear-cut logging and urban development, they are trying to operate a fish hatchery.

25.   A senior USDA official last year suggested the EPA does not have authority to regulate agricultural runoff, a position later disavowed by Agriculture Secretary Dan Glickman.

26.   Lake Chapala has survived a number of previous threats, including being choked by water lilies that feed on fertilizers and agricultural runoff.