الفهرس 
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Abstract
5. Summary
The current investigation was conducted aiming at investigating bioremediation as a safe environmental way for cleaning up soil from the elevated concentrations of heavy metals i.e. Fe, Mn, Zn, Cu, Cd, Co, Ni and Pb as well as As as the final waste remaining in soil after decomposition of its bearing pesticides. Fulfilling these purposes required carrying out a survey study involved six soil sites polluted with heavy metals due to different anthropogenic sources. Soils of four of them (Al-Gabal Al-Asfar, Arab Abou- Saed, Bahr Al-Baqar and Namoul) are polluted due to irrigation with waste waters (sewage and/ or industrial) while soil of the fifth site (Toukh) are polluted with the car exhausts due to the heavy traffic density on Cairo- Alexanderia Agricultural Highway whereas the soils of the sixth site (Shobra- Al-khema) complex.are polluted with emissions of smelters and factories chemnies.
Representative surface soil samples were collected from the polluted soils and determined for their total and DTPA-extractable contents of the heavy metals under study. Likewise, plant samples were collected from the maize plants grown on the aforementioned polluted soil sites to draw a picture about the relation that might be found between the heavy metal contents of these plants and the corresponding contents of these metal ions in soils and also to evaluate the suitability of usage maize plants for heavy metals phytoextraction.
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Geranium plants, that are well known to by heavy metals, were grown on the polluted soils extended up to about two months, to in accumulation of heavy metals in the different plan stem-leaves).The experimental work of this involved also a trial towards increasing bioavail heavy metals in soils through treating the soils amendments i.e. elemental sulfur at a rate of 0. compost at a rate of 2% and EDTA-Na2 at a rate o .These amendments are through to facilitate and e and accumulation of heavy metals by geranium sp.) plants which were grown on the polluted soils.
Also the experimental work dealt with suitability of maize plants for accumulation of As found in soil, irrigation water and ground water as remaining in soil and water after the rapid decomp arsenical herbicides. In this concentration, an a uncontaminated, soil sample taken from Cruden was artificially contaminated with As, whereon a was conducted using seedlings of maize (Zea may previously grown on a compost under greenhouse c the plants were sampled at the stages of V13, maturity. A similar experiment was conducted and were harvested at 5 different reproductive stage plants that were harvested at seed maturity. A thir was carried out on prolonged sub-surface irrigatio the conditions found under high water table. In thi
eraccumulate for a period estigate the parts (roots-investigation bility of the ith different %, the Nile 1 mg/kg soil hance uptake Pelargonium
investigating hich may be a final waste sition of the ditional, but ay, Scotland experiment cv. Alarik) nditions and nthesis and plant shoots beside the experiment to simulate experiment
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also maize was grown on soil under one level of applied As(25 mg kg-i soil) and kept subirrigated for 3 successive days with deionized water at V13, anthesis and maturity stages. Shoots and grains were collected at seed maturity. Maize plants were further grown on uncontaminated soil subirrigated during the aforementioned stages for 3 days with water having As at a concentration of 1 mg As then shoots and grains were collected also after seed maturity.
A fourth experiment was conducted in a way similar to that followed in executing the first experiment to investigate genotypic differences in As accumulation in shoots and grains. In this experiment two Egyptian maize varieties (single cross30 K6 and single cross 3084) along with a British variety (Alarik) were allowed to grown under one level of contamination (25 mg kg-i soil) and shoots and grains were collected after seed maturity. The experimental work involved also investigating the arsenate, arsenite and DMA influxes and toxicity in six maize varieties obtained from Egypt.
The most important obtained results could be summarized in the following:
The water used for irrigating the soils under study were characterized by the presence of the nutritive heavy metals i.e. Fe, Mn, Zn and Cu in concentrations obviously higher than those of the non-nutritive ones i.e. Co, Cd, Ni and Pb. Total concentrations of most these metal ions in Al-Gabal Al-Asfar, Arab Abou-Saed, Bahr Al-Baqar irrigation waters exceeded the maximum concentrations for water used continuously on all soils
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Summary
which means that these heavy metals will c reduction due to toxicities.
Total and DTPA-extractable contents of the s metals markedly exceeded the corresponding one contaminated soils.
What can be considered available concentrations metals i.e. DTPA-extractable contents, generally co their corresponding total contents, however these differed in their relations to the different soil
CaCO3, clay content, organic matter %....etc.
The maize plants grown on the polluted soils dif abilities to accumulate the studied metal ions from another, from a site to another and from plant organ
The concentrations of the studied metal showed significant correlations with their correspon extractable contents. Likewise, concentrations of th roots were significantly correlated with their conc leaves. Such significant correlations may make us concentrations of heavy metals in plant can be co function of their available contents in soil. •
The highest transport factors (concentration plant leaves to concentration of element in plant recorded for Mn, Zn and Pb indicating high tran these heavy metals from roots to leaves and also maize plants could be suitable for the phytoextract heavy metals in soil. However, the concentrations o
use growth
died heavy of the un-
of the heavy related with eavy metals ariables i.e.
ered in their element to o another.
ns in roots ing DTPA-se metals in ntrations in deduce that sidered as a
f element in roots) were location of uggest that on of these Mn, Zn and
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Pb in maize stern and leaves were much lower than the total concentration in soil. Accordingly maize plants are not considered hyperaccumulators for these heavy metals but can be used in the induced phytoremediation process of Mn, Zn and Pb.
Geranium (Pelargonium zonale plants
hyperaccumulated Mn, Zn, Cu, Co, Cd, Ni and Pb in their stems and leaves. Although geranium plants have demonstrated successful Cd phytoextraction but the results revealed that phytoextraction of the other heavy metals needs long time-periods to make the decontamination more acceptable, economically and environmentally.
Application of elemental sulfur at a rate of 0.5% or compost at a rate of 2% to the polluted soils enhanced the accumulation of heavy metals in geranium plants. Treating the soil with 1 mg EDTA Nat kg -1 enhanced heavy metal accumulation in plants above the enhancement effect of sulfur or compost treatments but significant reductions in geranium dry-weights were accompanied by EDTA treatment, and therefore the extractable amounts of heavy metals removed from soil by geranium shoots decreased.
The use of crops in long-term bioremediation could have more economic values during the phytoextraction process if the concentration of the contaminants in their biomass is below critical levels for livestock consumption. However, one should be cautious of using such investigated soils for cropping because their high content of metals might result in toxicity to all but
adopted plants.
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Phytoremediation of As (as a final waste product remaining in soil after the biological degradation of the organic herbicide) from soils artificially contaminated with As at the rates of 25 and 50 mg As kg’’ revealed that As uptake stimulated plant growth during different stages of maize development until the 20th day after silking. Reductions in shoot dry weight have been noticed after that which were in correlation with soil As. On the other hand, arsenic concentrations increased significantly in maize shoot and grain with the increase in the level of soil As and these increases were more detected after the 20th day after silking.
Sub-irrigating the contaminated soils with deionised water for 3 successive days decreased As concentrations in shoot and grain while sub-irrigating the uncontaminated soils had no significant effect on As concentrations in shoots and grains . Prolonged sub-surface irrigation with contaminated water decreased significantly shoots dry-weight during V 13 and anthesis with no significant effect during seed maturity; on the other hand, As concentrations increased significantly in both shoots and grains. These increases were more considerable when sub-surface irrigation took place during anthesis stage than during V13 while the increase became relatively low when flooding took place after seed maturity.
There were no significant genotypic differences in grain and the concentrations of arsenic in grains were always below the maximum acceptable level (2 mg/kg for As in feedstuffs of animals) proposed by the European Union (European
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1
Commission, 2003). The influx of arsenate, arsenite and dimethyl arsenic acid (DMA) were studied in 7-d-old excised maize roots (Zea mays L.), and then related to arsenate, arsenite and DMA toxicity. Arsenate, arsenite and DMA influx was all found concentration dependent with significant genotypic differences for arsenite and DMA. Arsenate influx in phosphate starved plants best fitted the four-parameter Michaelis-Menten model corresponding to an additive high and low affinity uptake system, while the uptake phosphate replete plants followed the two parameter model of ’Michaelis —Menten’ kinetics. Arsenite influx was well described by the two parameter model of `Michaelis —Menten’ kinetics. DMA influx was comprised of linear phase and hyperbolic phase. DMA influx was much lower than that for arsenite and arsenate. Arsenate and DMA influx decreased when phosphate was given as a pre-treatment as opposed to phosphate starved plants. The +P treatment tended to decrease influx by 50% for arsenate while this figure was 90% for DMA. Arsenite influx increasing slightly at higher arsenite concentrations in P starved plants but at lower arsenite concentrations, there was little or no difference in arsenite uptake. Low toxicity were found for DMA on maize compared with arsenate and arsenite and the relative toxicity of arsenic species was As (V) > As (III) >> DMA.