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العنوان
Remedation of polluted soil with some heavy metals using compost and apatite mineral =
المؤلف
Taher, Jamal Suliman Mohamad.
هيئة الاعداد
مشرف / ماهر جورجى نسيم
مشرف / ماجدة ابوالمجد حسين
مناقش / حسين احمد عبدالحميد زيد
مناقش / محمدى ابراهيم الخرباوي
باحث / جمال سليمان محمد طاهر
الموضوع
Soil- Science.
تاريخ النشر
2011.
عدد الصفحات
v, 87, 4 p. :
اللغة
الإنجليزية
الدرجة
الدكتوراه
التخصص
العلوم الزراعية والبيولوجية
تاريخ الإجازة
1/1/2011
مكان الإجازة
جامعة الاسكندريه - كلية الزراعة ساباباشا - الاراضى والكيمياء الزراعية
الفهرس
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Abstract

The risk of soils contamination with excess metals may exist because of atmospheric deposition near industrial areas, the use of urban or industrial wastes in agriculture, and the use of pesticides or fertilizers that contain considerable amounts of metals. There is a growing concern about the possibility of soil contamination resulting in uptake by plants and affecting food safety. Lead occurs naturally in all soils in concentration ranging from 1 to 200 mg kg-1, but rarely at levels that are considered to be toxic. However, increases of anthropogenic sources of pb in the environment have caused the Pb loading rate in soil to exceed its natural removal rate by approximately 20-fold. Also, cadmium (Cd) is one of the most toxic pollutants in the surface soil layer. A part of agricultural soils, all over the world are slightly to moderately contaminated by Cd due to industrial pollution, metal mining, manufacture and disposal as well as some agricultural practices such as extended use of superphosphate fertilizers, pesticides, sewage sludge and smelters dust spreading leads to dispersion of Cd.
Minerals apatite have been used to immobilize heavy metals in situ from aqueous solutions and contaminated soils, compost is used also in agriculture for bioremediation the polluted soils. The objectives of the current investigation are to:
1) Investigate the effectiveness of Rock phosphate (RP), hydroxyapatite (HA) and compost on the extractability of Pb and Cd from contaminated soil and,
2) Investigate the influence of the studied sorbents (rock phosphate, hydroxyapatite and compost) under polluted and non-polluted soil conditions on growth and chemical composition of corn plant.
3) Characterize the mechanism and reaction of the tested sorbents with lead and cadmium, the removal of aqueous Pb and Cd was studied. To achieve these objectives aqueous sorption experiments, soil extraction experiments and pot experiments were carried out and the most important results can be summarized as follows:
1. Lead and Cadmium Removal from Aqueous Solution
1.1. Effect of sorbent amount
- With increasing the sorbent rate, the percentage removal of Pb or Cd ion increases steadily but only up to certain values. For RP, the percentage removal increased from 95.37% to 99.94% for Pb ion and from 11.0 to 88.55% for Cd ion. For HA, the percentage removal increased from 88.15 to 98.12% for Pb ion and from 40.50 to 99.66 % for Cd ion. Finally for compost, the percentage removal increased from 96.90 to 99.51% for Pb ion and from 60.11 to 97.43 % when sorbent rate was increased from 0.23 g to 3.68 g.
- The metal ion sorption was Pb > Cd, using the three tested sorbents.
- The order of sorbents efficiency was compost > HA > PR for Cd ion removal and PR > compost > HA for Pb ion removal.
- The average values of removal percentage over the different rates of sorbents for Cd ion were 86.16, 81.52 and 66.34 for compost, HA and RP respectively. For Pb ion, the corresponding average removal percentage values were 98.97, 95.63 and 98.19 for RP, HA and compost respectively.
1.2. Effect of Pb and cadmium initial concentration
- With increasing the initial concentration of metal ions from 10 to 500 mg/L, the amount of metal uptake per unit weight of the sorbent (mg/g) increased, whereas the percentage sorption decreased for Cd ions only with the tested sorbents.
- The extent of Pb ion sorption increased from 2.07 to 108.02 mg/g for RP and 1.988 to 106.69 mg/g for HA and 2.15 mg/g to 108.48 mg/g for compost when the initial concentration was increased from 10 mg/L to 500 mg/L. The corresponding values for Cd ion sorption were 2.12 mg/g to 24.57 mg/g for HA, 2.12 to 43.48 mg/g for compost and 2.16 mg/g to 75.71 mg/g for RP.
- The results for Pb and Cd ions sorption were well represented by the linearized Freundlich isotherms model using the three tested sorbents. When the Langmuir isotherm model was applied to the data of the two metals, a reasonable fit was obtained only for the equilibrium data of Cd2+. The sorption capacities of RP, HA and compost have been found to be 24.39 mg/g, 43.48 mg/g and 83.33 mg/g respectively. A comparison of these values revels that compost exhibits quite a good capacity for removing Cd from aqueous solution followed by HA and RP. These results proved that low cost materials (RP and compost) can remove Pb and Cd ions from aqueous solution.
1.3. Extractable (available) Pb and Cd:
1.3.1 Extractable Pb:
- The extracted Pb increased significantly with increasing Pb level in soil treated with RP or HA or compost (average values over sorbent rates). Also, the extractable Pb from the polluted soil decreased significantly with increasing the rate of RP or HA or Compost (average values over pollution levels in soil).
- The HA material gives the lowest amount of extracted Pb at all of soil pollution levels except at the level of 300 mg Pb/kg soil , while the RP gives the lowest amount at soil pollution level of 300 mg Pb/kg soil under the experimental conditions. It was observed that extractable Pb decreased as the sorbent materials applied increased.
- The RP and HA were very effective in lowering the extracted Pb than the compost .The capacity in decreasing extractable Pb (average values over the rate of sorbent material) ranged between 2.977 and 61.473 mg/kg soil for RP, between 1.061 and 66.827 mg/kg soil for HA and between 1.938 and 99.191 mg/kg soil for compost. The capacities of RP and HA in decreasing the extracted Pb were higher than the decreasing capacity of compost. Also, the capacity of HA in decreasing extractable Pb was higher than that of RP.
1.3.2 Extractable Cd:
The extracted Cd increased significantly with increasing Cd level in soil treated with RP or HA or compost (average values over sorbent rates). Also, the extractable Cd from the polluted soil decreased significantly with increasing the rate of RP or HA or Compost (average values over pollution levels in soil).
- The HA material gives also the lowest amount of extracted Cd at all of soil pollution than those of RP and compost, while the compost gives the lowest amounts than those of RP except at soil pollution level of 500 mg Cd/kg soil under the experimental conditions.
-The extractable Cd decreased as the sorbent materials applied increased.
-The relationships between extractable Cd and sorbent rate at each Cd pollution levels in soil were calculated for each sorbent material. A highly R2 value was obtained for the three sorbent materials.
The results strongly demonstrate that the low–cost of compost or rock phosphate suggest that this approach might have great merit for cost-effective in situ immobilization of contaminated soils.
2. Lead and cadmium availability in sorbents-amended soil.
2.1. Dry matter yield
- Increasing the pollution level of Pb and Cd in soil significantly decreased the dry matter of corn plant (average weights over all ranges of the three sorbents). Increasing the pollution level to levels 2, 3 and 4 resulted in a decrease in dry matter yield to 0.358, 0.340 and 0.318 g/plant, respectively of the dry matter yield at the low pollution level (level 1).
- Dry matter yield was increased with sorbent rate (averages over all soil pollution levels and sorbent types) significantly. The higher sorbent rate (9.2 g/kg soil) produced higher dry matter yield than the other sorbent rates.
- The relative increase in dry matter yield associated with increasing sorbent rates of 2.3, 4.6, and 9.2 g/kg soil were 15.69, 19.61 and 25.49 % respectively.
- The yield of dry matter positively correlated with sorbent rate at each soil pollution level for the three sorbents. The values of r were the highest for compost followed by RP and HA sorbents.
-The yield of dry matter of corn plants in the soil treated with compost was significantly higher than those recorded in soils treated with RP and HA. The dry matter yield values of corn plants produced with the different sorbent types following the order: Compost > RP > HA.
-The obtained data indicated that there is a possible yield increasing due to increasing the rate of compost applied to the polluted soil with Pb and Cd.
2.2. Heavy metals content in plants
2.2.1. Lead content:
-The concentration of Pb in plant tissue and Pb uptake was affected significantly by soil pollution rate, sorbent rate and sorbent type.
-The uptake of Pb was affected significantly by soil pollution level, sorbent rate and sorbent type.