Effects of soil and plant on arsenic accumulation by arsenic hyperaccumulator Pteris vittata L.

摘要

Phytoextraction using Pteris vittata L., an arsenic hyperaccumulator plant, could be potentially applied to remediate arsenic-contaminated sites worldwide. Pteris vittata grew well and took up large amounts of arsenic in six arsenic-contaminated soils with different properties and different sources of arsenic contamination. However, efficiency of the ferns in continually taking up arsenic from the soils decreased with time, and varied with growing season. The arsenic concentrations in different chemical fractions before and after plant uptake showed that P. vittata took up arsenic from the most available and also from the less available pools in all soils. The change in arsenic availability in the rhizosphere was evaluated by comparing P. vittata with a non-arsenic-hyperaccumulator Nephrolepis exaltata. As expected, P. vittata removed more arsenic from the soil than the non-arsenic-hyperaccumulator fern. Besides the efficient detoxification mechanisms of P. vittata, its more extensive and finer root systems, and its greater capacity to change the soil pH and produce root exudates in the rhizosphere likely contributed to the difference. Furthermore, the experiments with P. vittata of different physiological ages revealed that younger plants (because of their higher metabolic and growth rate) were more efficient than older plants in taking up arsenic. Therefore, younger plants are recommended for phytoremediation. Comparing two arsenic hyperaccumulators in the genus Pteris showed that arsenic hyperaccumulator ferns differed in their ability to take up arsenic when growing under the same soils and environmental conditions. The concentrations of arsenic in both plants increased with the soil arsenic concentration, however, P. vittata performed better, regardless of the arsenic level in soils. After 4 weeks of growth, P. biaurita showed signs of stress and probably would not have survived longer under those conditions, while P. vittata showed no toxicity symptom. Our results showed that, in implementing an arsenic phytoextraction project, many aspects related to the plant must be considered.