ملخص رسالة الدكتوراه مقدمة من الدكتور/محروس يوسف محمد

Title
Mobility of Heavy Metals in Some Contaminated Egyptian Soils Treated with Certain Organic Materials

By

Mahrous Yousef Mohamed Awad
B.Sc. (Soil Science), Azhar University (1994)
M.Sc. (Soil Science), Minuifya University (2001)

Thesis

Submitted in Partial Fulfillment of the
Requirements For the Degree of

DOCTOR OF PHILOSOPHY

In

Soil Science
Department of Soils and Water,
Faculty of Agriculture,
Assiut University,
Assiut, Egypt
2007

SUMMARY AND CONCLUSIONS
Three contaminated soils at Helwan, El-Gabal El-Asfar (Cairo governorate) and Arab El-Madabeg (Assiut governorate) were chosen to study effects of certain organic materials on the mobility of some heavy metals (Pb, Cu, Zn and Mn) in some Egyption contaminated soils. These organic materials include ethyllyen diamine tetra acetic acid (EDTA) as a synthetic organic material as well as poultry litter extract (PLE), vinase (V) and humic acid (HA) solutions as natural organic materials compared to H2O as a control. This study was carried out in three experiments as follows:
I. Leaching Effects Using Some Organic Materials on the Mobility of Soil Heavy Metals.
An experiment was carried out in PVC columns to study the leaching effect using the investigated organic materials on the mobility of Pb, Cu, Zn, and Mn in the studied soils. Each organic material was applied at three levels (2, 4 and 6mmol/kg for EDTA; 25, 50 and 75g/L for PLE; 1:2, 1:1dilution of vinase to water as well as pure vinase; 0.013, 0.019 and 0.025% for HA) for two leaching periods (4 and 8 weeks). The control treatment for each soil had soil columns treated with distilled water. Each treatment for each soil column had 4 replications (2 replications for each leaching period)
The results could be summarized as follow:
1. Leaching the studied soils with different organic materials at various levels of application resulted in increases in the mobility of soil Pb Cu, Zn, and Mn in the studied soils.
2. The magnitude of soil Pb, Cu, Zn, and Mn mobility varied depending upon the organic material type, its application level and the soil type as well as the time period of leaching
3. The highest mobility values of these metals were recorded with the highest application level of all investigated organic materials.
4. It was observed highly significant differences between concentrations of these metals in the deepest layer (L3) and the upper two layers (L1 and L2) of all studied soil columns due to additions of organic materials compared to the control treatment.
5. The results indicated that, under all used organic materials and their levels of application, concentrations of these metals increased with column depth.
6. The studied organic materials differed in their efficiency in moving these metals from the top to the bottom of the soil columns. EDTA was found the most effective organic materials, especially its highest level, in increasing the mobility of Pb Cu, Zn, and Mn and reducing their levels in the upper 2 layers of all studied soil columns.
7. Significant higher levels of metals were mobilized using all investigated organic materials in all studied soil columns after 8 week than after 4 weeks of leaching.
8. The highest level of EDTA significantly decreased soil Pb Cu, Zn and Mn in the upper 10 cm layer after 8 weeks of leaching from 46.0 to 29.2 mg/kg, from 36.0 to 27.1 mg/kg, from 198.0 to 147.9 mg/kg, and from 283.0 to 232.9 mg/kg, respectively, for Helwan soil. The respective reduction values in soil Pb Cu, Zn, and Mn of this layer using this highest level of EDTA after 8 weeks of leaching were from 248.0 to 185.3 mg/kg, from 185.4 to 144.5 mg/kg, from 583.6 to 485.4 mg/kg, and from 315.0 to 275.2 mg/kg for El-Gabal El-Asfar soil. For El-Madabeg soil, the respective reduction values of the respective metals in this layer were from 85.5 to 59.8 mg/kg, from 37.7 to 24.3 mg/kg, from 138.2 to 98.8 mg/kg, and from 232.0 to 173.0 mg/kg after 8 weeks of leaching.
9. Generally, the investigated organic materials had the order of EDTA > Vinase > PLE > HA in mobilizing soil Pb Cu, Zn, and Mn in all studied soils. Vinase is also effective in mobilizing Pb Cu, and Zn of El-Madabeg soil, especially after 8 weeks of leaching. On the mean basis, it mobilized 17.8, 24.0 and 17.2% of Pb Cu, and Zn, respectively, of the upper layer of this soil after 8 weeks of leaching compared with 20.7, 27.9 and 21.9%, respectively, of these metals in this layer after 8 weeks of leaching with EDTA.
10. All investigated organic materials showed almost similar ability in mobilizing soil Pb and somewhat soil Cu in the upper layer of Helwan soil. On the average basis, EDTA, vinase, PLE and HA decreased Pb in the upper layer of Helwan soil by 32.3, 26.8, 22.0 and 18.7%, respectively, after 8 weeks of leaching.
11. Very low relative decreases in soil Mn of the upper layer in all studied soils occurred using PLE, vinase and HA compared with those of EDTA. For example, PLE, vinase and HA caused average relative reductions in Mn of the upper layer of Helwan soil of 4.0, 5.1 and 3.3%, respectively, compared with 16.5% for EDTA after 8 weeks of leaching.
12. Although soil Zn and Mn contents increase in the rank of El-Gabal El-Asfar soil > Helwan soil > El-Madabeg soil, the relative reduction values of these two metals in the upper layer as well as their relative increase ones in the deepest layerdue to the leaching using the organic materials had the order of El-Madabeg soil > Helwan soil > El-Gabal El-Asfar soil. Moreover, soil Pb and Cu contents increase in the order of El-Gabal El-Asfar soil > El-Madabeg soil > Helwan soil. However, the mean relative decrease of soil Pb in the upper layer and its relative increase in the deepest one after leaching with organic materials followed the sequence of Helwan soil > El-Madabeg soil > El-Gabal El-Asfar soil and those of soil Cu showed the rank of El-Madabeg soil > Helwan soil >El-Gabal El-Asfar soil.
13. EDTA was also the most effective organic material in leaching soil Pb Cu, Zn, and Mn out the soil columns. However, other organic materials removed traces of these metals out the studied soil columns.
14. The EC values and OM content of the studied soils treated with the investigated organic materials increased in the order vinase > EDTA > PLE > HA. However, leaching the studied soils with these organic materials caused reductions in the soil pH. Vinase was the most effective one and HA was the least one in reducing soil pH
II. Transformations of Heavy Metals Among Their Chemical Forms.
An incubation experiment was conducted to study the transformation and the redistribution of the studied soil metals among their chemical forms induced by addition of the investigated organic materials. It aimed to show the soil forms of heavy metals that involved in this mobility. So, this experiment was carried out using the studied soils that were incubated for 16 weeks with the highest level of each organic material. After incubation, a sequential extraction procedure was employed on the incubated soil samples. The studied chemical forms of metals were the exchangeable (EXCH), carbonate bound (C-bound), Mn oxide bound (MnO), organically bound (O-bound), poorly crystalline Fe oxide bound (PCFeO), crystalline Fe oxide bound (CFeO) and residual forms.
The results could be summarized as follow:
1. All investigated organic materials significantly increased levels of the exchangeable form of Pb, Cu, Zn and Mn in all studied soils compared to the control treatment. The magnitude of these increases depended upon the soil type, metal content and the type of organic material.
2. EDTA was the most effective organic material in increasing exchangeable levels of these metals in all studied soils followed by vinase and then PLE. On the other hand, humic acid was the least effective one in that matter in all studied soils. The low efficiency of PLE and HA in mobilizing the metals and inducing metal transformations may be attributed to the relatively short period used in these experiments as well as their relatively low application levels.
3. The PCFeO was the dominant form of Pb, Cu and Zn in El-Madabeg soil, the dominant one of Cu, Zn and Mn in Helwan soil, and the dominant one of Pb in El-Gabal El-Asfar soil. On the other hand, the O-bound was the dominant form of Cu, Zn, and Mn in El-Gabal El-Asfar soil, the CFeO was the dominant form of Pb in Helwan soil, and the MnO was the dominant one of Mn in El-Madabeg soil.
4. Lead increases in the EXCH, O-bound and MnO forms in Helwan soil induced by EDTA, PLE and HA were recorded on the expense of decreasing C-bound, PCFeO, CFeO, and residual forms. However, El-Madabeg soil treated with EDTA showed Pb increases in EXCH, O-bound, and C-bound forms on the cost of decreasing MnO, PCFeO, CFeO and residual forms.
5. Vinase in El-Gabal El-Asfar and El-Madabeg soils caused Pb levels to transform from MnO, O-bound, PcFeO and residual forms to the EXCH and C-bound form. However, in Helwan soil, it induced Pb increase in EXCH, MnO and O-bound forms transformed from the C-bound, CFeO and residual forms. Low Pb increases occurred in the EXCH and PCFeO forms in El-Madabeg soils treated with PLE and HA on the charge of decreasing the C-bound, MnO, O-bound and residual forms.
6. EDTA induced Cu increases in the EXCH, C-bound and MnO forms of all studied soils transformed from the O-bound, PCFeO, CFeO and residual forms. Vinase also caused Cu and Zn of the PCFeO, CFeO and residual forms of Helwan and El-Madabeg soils to transform to the EXCH, C-bound and MnO forms. Moreover, it increased Cu and Zn of EXCH, C-bound as well as PCFeO and CFeO forms of El-Gabal El-Asfar soil on the expense of O-bound and residual forms. PLE and HA showed low Cu increases in the EXCH and C-bound forms on the cost of decreasing the O-bound and residual forms in El-Gabal El-Asfar soil, the MnO, O-bound, CFeO and residual forms in Helwan soil, and CFeO and residual forms in El-Madabeg soil.
7. Increases in Zn levels of the EXCH form induced by EDTA in all studied soils were recorded mainly on the charge of decreasing the PCFeO, O-bound and residual forms. Low Zn transformation caused by PLE were also from the O-bound, PCFeO and CFeO forms to the EXCH and C-bound forms in Helwan soil, from C-bound, CFeO and residual forms to the EXCH, O-bound and PCFeO forms in El-Gabal El-Asfar soil, and from MnO and residual forms to the EXCH form in EL-Madabeg soil.
8. EDTA and vinase caused Mn to transform from the MnO, PCFeO, O-bound, CFeO and residual forms to the EXCH and C-bound forms in Helwan and El-Madabeg soils and from O-bound, PCFeO and residual forms to the EXCH and C-bound forms in El-Gabal El-Asfar soil. However, PLE induced low Mn increases in the C-bound and EXCH forms on the cost of decreasing other forms in Helwan soil and on the expense of MnO and residual forms in El-Madabeg soil. PLE also caused low Mn transformations in El-Gabal El-Asfar soil from the O-bound, residual and PCFeO forms to the C-bound, EXCH and MnO forms.
9. Lead percentages that were transformed in Helwan, El-Gabal El-Asfar and El-Madabeg soils were 10.12, 10.82 and 25.88%, respectively, by EDTA, 5.52, 2.41 and 13.52%, respectively, by vinase, 5.09, 1.78 and 4.15%, respectively, by PLE and 4.09, 1.08 and 4.66%, respectively, by HA.
10. Levels of Cu that were redistributed among various forms of Helwan, El-Gabal El-Asfar and El-Mdabeg soils were 15.81, 30.6 and 38.51%, respectively, by EDTA, 8.53, 26.76 and 20.9%, respectively, by vinase, 9.26, 11.50 and 6.04%, respectively, by PLE and 14.88, 8.62 and 13.27%, respectively, by HA.
11. Zinc levels that were transformed in Helwan, El-Gabal El-Asfar, El Madabeg soils were 29.86, 33.39 and 44.22%, respectively, by EDTA, 7.54, 7.42 and 8.07%, respectively, by vinase, 6.09, 3.92 and 1.61% by PLE, and 3.77, 4.00 and 1.62%, respectively, by HA.
12. Levels of Mn that were transformed in Helwan, El-Gabal El-Asfar and El-Madabeg soils were 19.03, 44.91 and 37.42%, respectively, by EDTA, 19.80, 29.00 and 34.46, respectively, by vinase, 10.01, 18.07 and 16.02%, respectively, by PLE, and 1.17, 22.98 and 5.46%, respectively, by HA.
III. Dry Matter Yield and Heavy Metal Uptake by Amaranthus Tricolor Plants.
A pot experiment was conducted in the greenhouse to study the ability of Amaranthus tricolor plants to absorb and accumulate heavy metals from soils in the presence of the added organic materials under study. The plants were irrigated in the begaining for 2 weeks by deionized water and then, irrigated at the field capacity level 8 times during the growth period (one irrigation/week) using the highest level of organic material solution which was used in the leaching experiment. However, the plants treated with the highest level of both EDTA and vinase in all soils were died. So, the lowest level of both materials (2mmol EDTA/kg and 1:2 dilution of vinase to distilled water) was used instead.
The results could be summarized as follow:
1. The organic materials added to all studied soils, except EDTA in El-Gabal El-Asfar soil, significantly increased the dry matter yield of the tested plants compared to the control treatment. The soils could be ranked according to the magnitude of dry matter yield of the plants due to the application of the organic materials in the order of El-Gabal El-Asfar soil > El Madabeg soil > Helwan soil.
2. The application of organic materials to the studied soils significantly resulted in increases in the uptake of Pb, Cu, Zn and Mn by amaranthus plants compared to the control treatment. The magnitude of the uptake increase of these metals varied depending upon the investigated organic material and the soil type.
3. Vinase gave the highest increase in the uptake of Pb by plants grown on Helwan and El-Madabeg soils, whereas PLE induced the highest one in El-Gabal El-Asfar soil. Moreover, EDTA was the most effective organic material in increasing Cu uptake by the plants in Helwan soil, whereas, vinase was the most effective one in both El-Gabal El-Asfar and El-Madabeg soil.
4. The highest amounts of Zn taken up by amaranthus plants were recorded with the application of EDTA to Helwan soil, vinase to El-Gabal El-Asfar soil, and the poultry litter extract to El-Madabeg soil. In addition, vinase was the effective organic material in increasing Mn uptake by plants in all studied soils.
5. Humic acid was found the least effective organic material in enhancing the uptake of all studied metals by the plants grown on Helwan soil as well as the uptake of Cu, Zn and Mn by the plants grown on El-Madabeg soil. Meanwhile, EDTA induced the lowest amounts of all metals taken by the plants grown on El-Gabal El-Asfar soil as well as Pb taken up from El-Madabeg soil.

It could be concluded from the obtained results that organic materials play an important role in mobilizing the heavy metals in soils. The pH of the soil is not the only factor that controls the mobility of these metals in soils. These materials may contain soluble organic acids and other soluble organics that form soluble organic complexes with these metals resulting in their mobility in the soils and transformations from other non-mobile soil forms to mobile ones.
Addition of these organic materials or their disposal on heavy metal contaminated soils, especially near sewage planes and industrial areas can cause hazard problems with respect of environmental pollution. The soluble organic complexes of these metals can contaminate the surface water and the groundwater resources as well as enhancing the plants and crops that are grown on these contaminated soils to absorb and take up high amounts of these hazardous heavy metals. These contaminated water resources and plants may cause heath problems for Human, animals and livestocks. Therefore, it should be recommended to dispose any organic material far from the sites that have heavy metal contaminated soils. The organic wastes such as sewage sludge should be separated from industrial ones during their disposal and treatments.