Date of Award

1995

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

John L. Kovar

Abstract

Reactions of soil arsenic with arsenic addition and the effects of soil arsenic on canola were studied because of a lack of information on this subject. The reactions of different pools of soil arsenic to arsenic addition were studied. The effects of soil arsenic and arsenic form and concentration in solution on canola growth and nutrient uptake were also investigated and an attempt to model arsenic uptake with a mechanistic computer model was made. In a solution study, rate of inorganic arsenic did not appear to effect arsenic accumulation in roots and shoots of canola. However, shoot and root arsenic concentrations increased with organic arsenic rates. Arsenic accumulated in the plant roots in both inorganic and organic treatments. Shoot dry weights were reduced when exposed to organic arsenic forms. Root length and dry weight were affected by all forms of arsenic. Shoot calcium and phosphorus levels increased while shoot zinc decreased with increasing arsenic rate. In a soil study, soil solution arsenic increased curvilinearly, while resin-exchangeable solid-phase arsenic approached a maximum with arsenic addition. Initial solution arsenic concentration and DTPA-extractable manganese were correlated with the change of solution arsenic concentration due to arsenic addition. The relation between total diffusible and solution arsenic was described with nonlinear regression and was different for each soil. In a growth chamber study, canola was sensitive to soil arsenic. A mechanistic computer model was used to predict arsenic uptake by canola. Using this model, root growth rate and root radius were found to have the most influence on arsenic uptake. Plant arsenic levels increased significantly with increasing arsenic rate. However, arsenic tended to remain in the plant roots. This study indicates that canola is sensitive to arsenic and that the form and concentration of arsenic affect toxicity. Furthermore, arsenic addition causes solution As to increase curvilinearly while resin-exchangeable solid-phase arsenic approaches a maximum. These changes in the soil As phases can lead to an increased bioavailability of the arsenic in the soil which can lead to increased uptake by plants that can be predicted using a mechanistic computer model.

Pages

102

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