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Heather F. Henry and Jodi R. Shann, Department of Biological
Sciences, University of Cincinnati, 731 Rieveschl Hall,
Cincinnati, OH 45221-0006, Tel: 513-556-9765, Fax:
513-556-5299
Theoretically, the processes of soil aging and ecological
restoration should lead to increased stability of both
soil contaminants and plant communities.
Over time, contaminants become fixed (sequestered)
in soil. This fixation lowers the bioavailability thereby reducing
their impact on plants or other organisms.
In the absence of phytotoxicity, the vegetative
community further enhances sequestration, prevents
erosion, and contributes to the gradual mineralization of
organic contaminants.
Concurrently, plant communities become more stable
as cover, biomass, species diversity and richness
increase. This
study investigated soil aging and plant succession on a 5
acre site used as a treatment facility for petroleum
refinery waste. The aims of this three year project were to:
1) measure plant biomass, cover, richness, and
diversity; 2) characterize edaphic and micro-climatic
variation around the site; and 3) assess soil
contamination through time. Across the site, 16 plots (37 m˛) were delineated - 12 for
study of natural succession and 4 to act as a control by
removal of vegetation.
Plant data was collected monthly over the growing
season. Two
soil cores (100cm x 2.5cm) were removed annually from each
plot, analyzed for TOC, C/N, pH and then were sequentially
extracted for metals and PAHs. Plant richness, cover, and diversity increased during the
study period. These
increases were not uniform across the site, nor were they
correlated with soil contamination data.
Sequential soil extraction suggested only a small
percentage of total contaminants were bioavailable, and no
significant changes (over three years) were detected in
total soil loading. On
this aged site, the stability of contaminants appeared to
allow succession to progress in response to microclimatic
factors. Broader
implications of these results suggest that other abandoned
waste sites may be candidates for ecological restoration
by natural succession.
Under a low risk scenario, ecological restoration
should be an allowable choice for site management.
Effects
of Contaminants on Cover of Crops and Weeds in Long-term
Field Trial
Prof. László Radics, Szent István University,
Faculty of Horticultural Sciences, Department of
Ecological and Sustainable Production Systems, Villányi
út 29-43, H-1118 Budapest, Hungary, Tel: +36-1-372-6235,
Fax: +36-1-372-6325
Dr. Imre Kádár, Research Institute for Soil Science and
Agricultural Chemistry, Herman Ottó út 15, H-1022
Budapest, Hungary, Tel/fax: +36-1-355-8491
The purpose of this work was to evaluate the
toxicity effect of some microelement/contaminants on the
soil fertility and crop growth. A long-term field trial
was set up at the Nagyhörcsök Experimental Station of
the Research Institute on loamy calcareous chernozem soil,
developed on loess. The long-term field trial was set up
in 1991. The site has in its plowlayer 20% clay, 3% humus,
3-5% CaCO3. To ensure a sufficient
macronutrient supply in the whole experiment, 100-100
kg/ha N, P2O5 and K2O are
given yearly. 13 elements/chemicals were added on 4 levels
each as soluble salts to plots once at initiation and
mixed into the plow layer. The 52 treatments are arranged
in a split-plot design with 2 replications. Element
applied were Al as AlCl3, As as NaAsO2,
Ba as BaCl2, Cd as CdSO4, Cr as K2CrO4,
Cu as CuSO4, Hg as HgCl2, Mo as (NH4)Mo7O24,
Ni as NiSO4, Pb as Pb(NO3)2,
Se as Na2SeO3, Sr as SrSO4,
and Zn as ZnSO4. Loading levels were 0, 90, 270
and 810 kg/ha. In the trial there were different cops in
each year: maize, carrot, potato, pea, red beet, spinach,
winter wheat, sunflower, sorrel, winter barley. Cover of
weeds and crops were measured and on the basis of the
cover, effects of 13 elements were set out. Greatest
poisoning effect was measurable in the case of selenium.
Damage effects of the other added elements were variable
utterly to symptom-free status.
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