Potential of Pteris vittata L. for phytoremediation of sites co-contaminated with cadmium and arsenic: The tolerance and accumulation

Field investigation and greenhouse experiments were conducted to study the tolerance of Pteris vittata L. （Chinese brake） to cadmium （Cd） and its feasibility for remediating sites co-contaminated with Cd and arsenic （As）. The results showed that P. vittata could survive in pot soils spiked with 80 mg/kg of Cd and tolerated as great as 301 mg/kg of total Cd and 26.8 mg/kg of diethyltriaminepenta acetic acid （DTPA）-extractable Cd under field conditions. The highest concentration of Cd in fronds was 186 mg/kg under a total soil concentration of 920 mg As/kg and 98.6 mg Cd/kg in the field, whereas just 2.6 mg/kg under greenhouse conditions. Ecotypes of P. vittata were differentiated in tolerance and accumulation of Cd, and some of them could not only tolerate high concentrations of soil Cd, but also accumulated high concentrations of Cd in their fronds. Arsenic uptake and transportation by P. vittata was not inhibited at lower levels （〈20 mg/kg） of Cd addition. Compared to the treatment without addition of Cd, the frond As concentration was increased by 103.8% at 20 mg Cd/kg, with the highest level of 6434 mg/kg. The results suggested that the Cd-tolerant ecotype of P. vittata extracted effectively As and Cd from the site co-contaminated with Cd and As, and might be used to remediate and revegetate this type of site.

Elemental allelopathy by an arsenic hyperaccumulating fern,Pteris vittata L.

Aims the functional advantages of arsenic(As)hyperaccumulation by plants are poorly understood.One proposed benefit,termed ele-mental allelopathy,occurs when hyperaccumulated As is cycled from the plant back into the top layer of soil,allowing As hyperaccu-mulators to gain an advantage over intolerant species by increasing soil As concentrations([As])underneath their canopy.to date,there are no studies that detail the presence of increased soil[As]associ-ated with As hyperaccumulators.In this study,we documented vari-ation in the soil[As]associated with the Chinese brake fern,Pteris vittata L.and also compared the effects of environmentally relevant soil and solution[As]on competitor plant growth.Methods Four populations of P.vittata were identified in central Florida,USA.P.vittata tissue samples and soil samples were collected at the base of and at 3 m away from ferns in each population(n=36).Five sample locations were randomly selected from each site,and soils from the base and 3 m away from each fern were collected to examine the effects of naturally occurring soil[As]on the germination and growth of a potential competitor plant(Oxalis stricta).Solutions with increasing[As]were also used to examine the threshold for negative effects of[As]on O.stricta growth.[As]were measured using inductively coupled plasma mass spectrometry(ICP-MS).Important Findings Overall,soil[As]from the base of ferns was nearly twice that of soil 3 m away indicating that ferns hyperaccumulate As.However,ferns and their associated soil,contained different[As]depending on their col-lection site,indicating that these populations accumulate and use[As]differently.O.stricta growth decreased and germination was delayed as solution and soil[As]increased.However,the relative distance from the fern that the soil was collected from did not affect growth,which would be expected with elemental allelopathy.Our results show that P.vittata is associated with higher soil[As]and these concentrations are sufficient to inhibit growth of competitors.However,the absence of a strong inhibitory relationship associated with proximity to the fern across all locations suggests that the possible functional advantages of elemental allelopathy may depend on site specific characteristics.