answer: #Person1# and #Person2# discuss direct pollutions, which are from factories, refineries waste treatment plants, and indirect pollutions which include contaminants that enter the water supply. Then they call for active participation in dealing with those problems.
documents: #Person1#: Well, no one could survive without water, but you see pollution has been making more and more water unable for drinking.
  #Person2#: Yeah. Water pollution has for a long time been a major concern among the environmental issues.
  #Person1#: But what are the sources of water pollution?
  #Person2#: They could generally be divided into two categories, direct and indirect contaminant sources.
  #Person1#: Well, direct ones are the pollution directly from factories, refineries waste treatment plants etc. , aren't they?
  #Person2#: Yeah. They are emitted directly into urban water supplies.
  #Person1#: But what about the indirect ones?
  #Person2#: Indirect sources include contaminants that enter the water supply from soils or groundwater systems and from the atmosphere via rainwater.
  #Person1#: I see. For the sake of us all, we should be an active participator in the prevention of it.
  #Person2#: Sure. It's an issue asking for everyone's participation.