Page 168 - Plant-Based Remediation Processes

Chapter 9
Phyto-transport and Assimilation of Selenium

Xiao-Zhang Yu and Ji-Dong Gu

9.1 Selenium in the Environment

Selenium (Se) is one of the most widely distributed elements in the earth’s crust and
geographic distribution of Se in the environment is extremely variable (Hansen
et al. 1998). In China, the average abundance of Se in the earth’s crust is
1
0.058 mg kg , which is slightly lower than that in other parts of the world (Xia
and Tang 1990). While there are natural sources of Se, anthropogenic inputs of Se-
containing chemicals into the environment are greater in amounts than natural
contribution (Wu 2004). This has resulted in the elevated Se levels in natural
ecosystems impacted by anthropogenic processes. Therefore, the risks derived
from industrial activities and discharges have drawn widespread concern world-
wide. Indeed, ample evidence showed that the increasing levels of Se have caused
soil, air, and water pollution as well as changes in the structures of natural
communities and ecosystems at organism levels (Ohlendorf et al. 1986; Banuelos
et al. 1996).
In nature, Se occurs in four oxidation states with the chemical forms of selenide
0
4+
6+
2
(Se ), elemental or “colloidal” Se (Se ), selenite (Se ), and selenate (Se )
(Rosenfeld and Beath 1964). The most common and soluble species are selenate
and selenite found mostly in seleniferous soils and agricultural drainage water
(Banuelos and Lin 2005), whereas elemental Se dominates in anaerobic environ-
ment (Terry et al. 2000). Selenide is the ionized form of hydrogen selenide (H 2 Se)
and unstable in aqueous solutions (Barceloux 1999). Both selenate and selenite
X.-Z. Yu (*)
The Guangxi Key Laboratory of Theory and Technology for Environmental Pollution Control,
College of Environmental Science and Engineering, Guilin University of Technology, Guilin
541004, People’s Republic of China
e-mail: yuxiaozhang@hotmail.com
J.-D. Gu
Laboratory of Environmental Toxicology, School of Biological Sciences, The University of Hong
Kong, Pokfulam Road, Hong Kong, Hong Kong SAR, People’s Republic of China

D.K. Gupta (ed.), Plant-Based Remediation Processes, Soil Biology 35, 159
DOI 10.1007/978-3-642-35564-6_9, # Springer-Verlag Berlin Heidelberg 2013