Phytostabilization of arsenic - In-Situ Remediation of Arsenic-Contaminated Sites - page 53

Figure 3.1. Phytostabilization of pollutants (X). Accumulation in plant roots and precipitation onto soil
particles in the rhizosphere immobilizes the pollutants, preventing translocation to the shoots and leaching
to the surrounding surface and groundwater.

gL − 1 (Commission Directive 2003/40/EC). No worldwide standards for As in food are
currently available. Instead, the European Food Safety Authority (EFSA) has established an
inorganic As exposure dosage of 0.3-8

to 10 µ

gAskg − 1 bodyweight per day (EFSA, 2009).
A variety of environmental factors (e.g., pH, redox potential, adsorption reactions, and bio-
logical activity) influence the concentrations and speciation of soluble As in soils (Bhumbla
and Keefer, 1994). The most common transformation pathways of As in soils are illustrated in
Figure 3.3 . With increased biological activity, the amount of organic As species increases. For
example, approximately two thirds of the As in a water sample from the Salton Sea in California
was in the form of dimethylarsinic acid due to the activity of phytoplankton (Andreae and Klumpp,
1979).
Arsenate and arsenite are the dominant As species in soils and waters. The redox potential
is the most influential factor in arsenate-arsenite speciation under normal pH ranges in soil.
With increasing redox potential, As transformation shifts toward an increased amount of arsenate
(p E > 10), while arsenite dominates under low redox potential conditions (p E < 6) (Sadiq, 1997).

µ