Effects of consolidated tailings water on red-osier dogwood (Cornus stolonifera Michx) seedlings.

As part of their tailings management, the oil sand industries plan on producing consolidated (composite) tailings (CT), in which an inorganic coagulant aid (gypsum) is added to create a non-segregating deposit. The water associated with this treatment contains potentially phytotoxic levels of sodium, sulfate, chloride, boron, aluminum, fluoride and strontium. Since CT water is expected to saturate deposits in the reclamation areas, it may affect successful reclamation of these sites. Red-osier dogwood (Cornus stolonifera Michx) was demonstrated to be relatively salt resistant and to have high potential for the reclamation of mining areas. In the present study, we used red-osier dogwood to examine the effects of CT water on the accumulation of ions within plant tissue, growth, gas exchange, water potentials and chlorophyll concentration. CT water reduced shoot lengths and dry weights in treated plants. The roots of treated plants accumulated higher concentrations of sodium and chloride than did shoots. The accumulation of sodium and chloride was accompanied by an increase in magnesium and calcium and a decrease in potassium in the roots, while the levels of potassium increased in the leaves. CT water altered gas exchange and water potentials in seedlings, and resulted in a decrease in chlorophyll's a and b. The results suggest that the mechanisms of salt resistance in red-osier dogwood seedlings involve the restriction of sodium transport from roots to shoots.