Paper Reviewed
Jia, X., Liu, T., Zhao, Y., He, Y. and Yang, M. 2016. Elevated atmospheric CO2 affected photosynthetic products in wheat seedlings and biological activity in rhizosphere soil under cadmium stress. Environmental Science and Pollution Research 23: 514-526.

Introducing their study, Jia et al. (2016) write that "heavy metal contamination of soil is a serious global problem" and that "among the heavy metals, cadmium (Cd) is widespread and is one of the most toxic pollutants of the surface soil layer," where it is "dispersed into agricultural soil as a result of the use of phosphate fertilizers, application of sewage and industrial wastewater for irrigation, atmospheric deposition from metallurgical industries, incineration of plastics and batteries and burning of fossil fuels," citing the studies of Tukaj et al. (2007) and Li et al. (2013). And faced with this current and growing challenge, the five Chinese researchers decided to see if atmospheric CO2 enrichment had any significant impact on it.

This they did in a study they conducted in the spring of 2013 at the out-of-doors CO2 enrichment chamber facility on the Weishui Campus of the Chang'an University of Xi'an, China, where they grew spring wheat (Triticum aestivum) from seed in pots lined with root bags filled with soil that they artificially contaminated with CdCl2·2H2O) solution to concentrations of 0.31 (Cd0, the control, no Cd spiked to soil); 1.31 (Cd1); 5.31 (Cd5); and 10.31 (Cd10) mg Cd kg-¹ dry soil that they incubated for 30 days, after which they placed the pots in open-top chambers maintained at either 385 ppm CO2 or 703 ppm CO2, where they were maintained at 60% field capacity by watering during the seedling growth stage.

This experiment revealed, in the words of Jia et al., that "elevated CO2 concentrations could moderate the effects of heavy metal pollution on enzyme activity and microorganism abundance in rhizosphere soils, thus improving soil fertility and the micro-ecological rhizosphere."

References
Li, T.Q., Tao, Q., Han, X. and Yang, X.E. 2013. Effects of elevated CO2 on rhizosphere characteristics of Cd/Zn hyper-accumulator Sedum alfredii. Science of the Total Environment 454-455: 510-516.

Tukaj, Z., Bascik-Remisiewicz, A., Skowronski, T. and Tukaj, C. 2007. Cadmium effect on the growth, photosynthesis, ultrastructure and phytochelatin content of green microalga Scenedesmus armatus: a study at low and elevated CO2 concentration. Environmental and Experimental Botany 60: 291-299.