Characteristics of Cadmium Concentration and Transport of Pueraria thornsonii in Farmland with Different Cadmium Pollution Degrees

Abstract

This study aimed to elucidate the cadmium (Cd) concentration and transport characteristics of Pueraria thornsonii in farmland with different Cd pollution degrees, so as to provide a reference basis for phytoremediation of Cd-contaminated farmland. The multi-point experiments in farmland with different Cd pollution degrees[ω(Cd) 0.32-38.08 mg·kg-1] were conducted, and the biomass (dry weight), Cd content, accumulation, concentration, and transport of Cd in P. thornsonii tissues under the main growing period were assessed. According to the results, for P. thornsonii, the tuber dry weight ranged from 5.04 to 11.98 t·hm-2, biomass ranged from 13.21 to 29.07 t·hm-2, and Cd accumulation ranged from 15.74 to 106.03 g·hm-2in the study area. The pattern of Cd uptake by P. thornsonii showed that the main vine>leaf>lateral branches>basal part of sti>tuber. The Cd content in P. thornsonii tissues considerably increased with soil Cd content (P<0.05), whereas the biomass decreased significantly (P<0.05). The Cd concentration and transport factor of aboveground parts in P. thornsonii showed a trend of initially falling, then increasing and decreasing again, whereas the Cd enrichment and transport coefficient of tubers gradually decreased. Correlation analysis revealed that the amount of Cd in the soil was a major predictor of Cd accumulation in P. thornsonii. Under light to moderate Cd contamination, the commercial portion of P. thornsonii (arrowroot)[ω(Cd) 0.03-0.22 mg·kg-1] was less than the standard limit for medicinal plants (≤ 0.30 mg·kg-1). In P. thornsonii from moderately contaminated areas, the Cd concentration and transport factor of aboveground parts were 2.43-7.97 and 3.02-9.81, respectively. This indicates that P. thornsonii is a prospective plant ideal for remediating Cd-contaminated soil because of its high capacity to transfer and enrich Cd.