Recent advances in phytoremediation of arsenic-contaminated soils - In-Situ Remediation of Arsenic-Contaminated Sites - page 68

have been studied to mitigate arsenic contamination in soil-rice system (Kertulis et al ., 2005; Ma
et al ., 2008; Zhao et al ., 2010). To prevent loading of arsenic into soils from irrigating water,
which has been well recognized in South and South-east Asia, arsenic phytofiltration technique,
using arsenic hyperaccumulators or aquatic plants with substantial arsenic accumulating ability
can be taken into account for arsenic reduction in irrigation water (Rahman et al ., 2007).
In this chapter, phytoextraction and phytostabilization using As hyperaccumulators and tolerant
species in both greenhouse- and field-scale studies are discussed from different perspectives.
With prevalent hazards of arsenic in South Asia, potential phytoexclusion strategies are proposed
to mitigate arsenic contamination in a soil-rice system. Furthermore, the feasibility of using
phytofiltration to reduce continuous loading of arsenic into agricultural soils is discussed.

4.2 PHYTOEXTRACTION OF ARSENIC CONTAMINATED SOILS

As the first known arsenic hyperaccumulator, Pteris vittata L. (Chinese brake fern) exhibits great
potentials to extract arsenic efficiently from contaminated soils and concentrate > 90% of the
arsenic in the fronds with BF up to 126 and little toxicity (Ma et al ., 2001). Furthermore, the
plant grows fast and yields considerable biomass, particularly in tropical and subtropical areas.
These constitutive traits of P. vittata have attracted extensive attention regarding its application in
phytoextraction of arsenic-contaminated sites. Most studies have demonstrated effective extrac-
tion of arsenic by P. vittata in a reasonable time frame with different experiment scales (Gonzaga
et al ., 2008; Kertulis-Tartar et al ., 2006; Tu et al ., 2002). The effective decontamination of arsenic-
contaminated soil by P. vittata is largely attributed to its unique metabolism traits, through effective
mobilization of arsenic in the rhizosphere, efficient uptake by the roots and translocation to the
fronds. Following the discovery of P. vittata , additional 11 fern species belonging to Pteridaceae
family have been identified to hyperaccumulate arsenic, providing alternative plant resources
for phytoextraction of arsenic from contaminated soils ( Table 4.1 ) . As detailed in this section,
phytoextraction using P. vittata is discussed with the underlying mechanisms.

4.2.1 Efficient arsenic extraction by P. vittata
P. vittata is known for its effectiveness in arsenic phytoextraction from soils. In a greenhouse
experiment, P. vittata were grown in an arsenic-contaminated soil containing 98 mg As kg − 1 .
After 20 weeks of growth,

26% of soil arsenic from each pot (1.5 kg soil pot − 1 ) was removed

∼

Table 4.1. Arsenic hyperaccumulators identified up to date in Pteridaceae family.

Frond arsenic
concentration Soil arsenic

[mg kg − 1 dw] [mg As kg − 1 ] Species Reference

Pteris vittata 2500-22630 50-1500 Ma et al . (2001)

Pteris cretica 6200-7600 500 Zhao et al . (2002)

Pteris umbrosa
Pteris longifolia
Pteris biaurita 1770-3650 100 Srivastava et al . (2006)

Pteris quadriaurita
Pteris ryukyuensis
Pteris aspericaulis 4000 200 Wang et al. (2007)

Pteris fauriei 3275

Pteris oshimensis 1365

Pteris multifida 3942

Pityrogramma calomelanos 2270-6380 20-8800 Visoottiviseth et al . (2002)