Plant Soil Metal Relationships from Micro to Macro Scale
K. Bujtas, A.s. Knox, I. Kadar, and D.C. Adriano
INTRODUCTION
Experimental data on fate, bioavailability, and effects of metals in the
soil plant system are often derived from various culture techniques:
- pot exeriments (microcosm),
- larger soil columns or lysimeters (mesocosm), or
- field
experiments (macrocosm).
In
some studies, solution culture is used instead of soil medium. As the
different experimental techniques have various advantages and may yield
information on several aspects of the same issue, selection of the most
suitable experimental technique is important. However, there are inherent
difficulties in interpreting data on plant growth, on bioaccumulation,
and phytotoxicity of metals established using different
techniques.
Problems associated with assessment of metal phytoavailability (defined as metals taken up by plant via root uptake) and long-term risks associated with accumulation of high levels of these elements in the soils may be better interpreted if the limitations of the various experimental techniques are known.
This chapter summarizes laboratory and field investigations aimed at studying
the advantages and disadvantages of various culture techniques and theif
applicability as a measure of metal bioavailability (see Chapter 3 for
other techniques of bioavailability assessments) and as a tool in the
risk assessment of heavily contaminated soils. The experimental studies
include
1) greenhouse pot experiments in which various forms of metals origi-
nating from flue dust applications to the soil were measured using the
sequential extraction technique and the effects of metals on the growth
and their uptake into experimental plants were assessed, both in the'
presence and absence of ameliorants;
2) use of large soil columns, either under field conditions as lysimeters
, to assess movement of the metals in the soil profile or in the laboratory
for studying plant availability of the metals after addition of metal-enriched
sewage sludge to cropped, large, undisturbed soil monoliths; and
3) long-term small-plot field experiments aimed to study the effects of
13 potentially toxic elements on various crops and their potential harm
in fuIther steps of the food chain.
All these experiments involve application of several metals, separately
or in combination with the growth medium. This chapter will focus on forms,
phytoavailability, movement, and plant uptake of zinc (Zn) and chromium
(Cr) as examples of an essential, relatively mobile, and a nonessential,
more tightly bound element, respectively.
SREL Reprint #2761
Bujtas, K., A. S. Knox, I. Kadar and D. Adriano. 2003. Plant soil metal relationships from micro to macro scale. p. 175-204. In Bioavailability, Toxicity and Risk Relationships in Ecosystems, edited by R. Naidu, V. Gupta, S. Rogers, R. Kookana, N. Bolan, and D. Adriano. Science Publishers, Inc.
