Application of an insoluble polyacrylate polymer to copper-contaminated soil enhances plant growth and soil quality

We investigated whether an insoluble polyacrylate polymer could be used to improve the quality of a copper-contaminated soil. Growth of annual medic (Medicago polymorpha L.) was stimulated in the polymer-amended soil, such that total biomass produced was three times that of plants from unamended soil. Roots of plants cultivated in the polymer-amended soil had a concentration of copper that was 73% of that in plants from the unamended soil. Biological N-2 fixation was enhanced in the polymer-amended soil. Soil enzymatic activities at the end of the experiment were correlated with plant growth and copper concentration of plants grown in soils with different levels of copper, which were achieved by mixing the contaminated soil with varying proportions of a soil of low copper content. Shoot dry weight was positively correlated with acid phosphatase, beta-glucosidase, beta-galactosidase and urease, whereas copper concentration in the roots of the annual medic was negatively correlated with acid phosphatase, beta-galactosidase, cellulase and urease. The results are consistent with soil remediation by the polyacrylate polymer. Soil quality as inferred from plant growth, biological N-2 fixation and soil enzymatic activities improved as a result of the remediation process.