Persistence of 2,4-dichlorophenol, 2,4,5-trichlorophenol, 2,3,7,8-tetrachlorodibenzo-p-dioxin, and 2,3,7,8-tetrachlorodibenzofuran in Soils of a Forest Ecosystem Treated With 2,4-D/2,4,5-T Herbicide in Eastern Canada.