汚染源[osengen] source of pollution
音源[ongen] sound source
禍源[kagen] source of misfortune
供給源[kyoukyuugen] source of supply
経営資源[keieishigen] management resource

源氏物語[genjimonogatari] the Tale of the Genji
源泉[gensen] source
源流[genryuu] current-limiting
語源[gogen] word root

溯る[sakanoboru] to go back
溯及[sokyuu] tracing back
溯源[sogen] returning to the origin

溯航[sokou] going upstream
溯河魚[sakkagyo] anadromous fish (fish that migrates upstream, e.g. salmon)