ZHANG Xingfeng, the Ph.D candidate of soil ecology and ecological engineering group of South China Botanical Garden (SCBG), under the guidance of the supervisor of Prof. XIA Hanping, carried out a pot experiment in the greenhouse to evaluate the phytoremediation abilities of four forage grasses, Pennisetum americanum × P. purpureum, Paspalum atratum cv. Reyan No. 11, Stylosanthes guianensis cv.Reyan Ⅱ and Silphium perfoliatum with respect to soil Cd and Zn pollution. The results showed that shoot Cd extraction amounts were 624, 179, 21 and 15 µg/plant for P. americanum × P. purpureum, P. atratum cv. Reyan No. 11, S. guianensis cv.Reyan Ⅱ and S. perfoliatum, respectively at soil Cd concentration of 8 mg/kg. The shoot Zn extraction amount for P. americanum × P. purpureum was 8,189 µg/plant, while the other three grasses were severely intoxicated at the soil Zn concentration of 600 mg/kg. Based on the data of the present experiment, to decrease soil Cd from the concentration of 8 to 1 mg/kg, P. americanum × P. purpureum and P. atratum would need only 12 and 32 years, respectively, while S. guianensis and S. perfoliatum would need up to 95 and 476 years, respectively. To decrease soil Zn from the concentration of 600 to 200 mg/kg, P. americanum × P. purpureum would need 40 years only, but the other three grasses would be severely intoxicated and could not be used to remediate soil.

The results indicate that P. americanum × P. purpureum and P. atratum could be useful for phytoextraction of either or both Cd and Zn pollution; S. perfoliatum could be regarded as a candidate species for phytostabilization of Cd contamination; while S. guianensis had no remediation capability. These results have been published online in Bioresource Technology, a prestigious journal in the field of agricultural engineering.