DTPA: The effects of extraction techniques on Cd, Cu, Ni, and Zn extraction from dredged materials and correlations with plant metal uptake

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Abstract
Transporting dredged spoil inland for use in reconditioning adjacent waterway lands marginally suited for agricultural production may be an attractive alternative to current open water and land containment disposal practices. Levels of plants available metals in the dredged materials must be estimated to prevent excessive, detrimental additions to metals to the soil. The variability that often occurs when the widely used DTPA [diethylene triaminepentaacetic acid] extraction procedure is used for the prediction of excessive metal levels in dredged materials is demonstrated. The effects of equilibration time (2, 4, and 24 h) and soil:solution ratio (1:2, 1:5 and 1:10 and 1:20) on the quantities of Cd, Cu, Ni and Zn extracted by DTPA were studied. The best correlations between the quantities of Cu, Ni and Zn extracted and metal absorption by barley and ryegrass occurred with a 24-h equilibration time. The best estimations of plant available Cu and Zn occurred when sediments were extracted in a 1:10 soil:solution suspension, but better estimations of plant available Ni were obtained by using a 1:2 soil:solution ratio. Cd uptake was not consistently correlated with Cd extracted by DTPA solutions.