الفهرس 
INTRODUCTION
Cement By-passOnly 14 pages are availabe for public view
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Abstract
Soil pollution has become a serious environmental problem in every country of the world due to industrialization. Cement by-pass and lime mud are major byproducts of cement industry and sugar industry, respectively, which accumulate daily in huge amounts. If these byproducts materials are wisely re-used or even disposed, they will not become pollutants for the environment. This study aims to evaluate the use these industrial byproducts in 1) improving the properties and nutrients status of the desert sandy soil, 2) reclaiming the sodic and saline-sodic soils, and 3) remediating of the heavy metal contaminated soils.
1. Use of Cement By-pass in Improving Some Properties and Nutrient Status of Sandy Soils
1.1. Alfalfa experiment
A field experiment was conducted in Assiut cement company farm to study the effects of cement by-pass additions at 0, 2.5, 5 and 7.5% (2.5 % = 23.8 kg by-pass/plot, 5 % = 47.6 kg by-pass /plot and 7.5 % = 71.4 kg by-pass /plot) to the sandy desert soils with and without applying farmyard manure (FYM) on the growth, yield and nutrient contents of alfalfa plants. The experiment was designed as a randomized complete block in split plots with three replications where the farmyard manure (without and with FYM) was assigned to the main plots and the by-pass level was in the sub-plots. The area of each soil plot was 2 m x 2 m (4 m2). The soil of each plot was leached using a specific volume of water every other day for 21 days. Alfalfa seeds were sown on April 8, 2009 at 15 g /plot. Farmyard manure was added at 4 ton/fed after 30 days from sowing. Nitrogen, phosphorus and potassium fertilizers were added to the soil at the recommended levels as ammonium nitrate, superphosphate and potassium sulfate, respectively. All agriculture practices were done as usual. Four alfalfa cuts were taken until Nov. 24, 2009.
The results of this study could be summarized in the following:
By-pass additions to the sandy desert soil resulted in significant decreases in soil pH before cultivation and significant increases in the available soil P, K, Fe and Cu before and after alfalfa planting. The interaction effect of by-pass and FYM application caused significant increases in the total soil N as well as available soil K and Cu but insignificant increases in the available soil P, Fe, Mn and Zn. Additions of by-pass to the sandy desert soil at a level of 7.5% showed the highest increase in the total green yield and total dry matter of alfalfa plants of 121.4 and 106.2 %, respectively, compared to the control. The best addition level of by-pass to the sandy desert soil to obtain good growth and yield of alfalfa was 7.5% with or without FYM application.
1.2. Sorghum experiment
Another field experiment was carried out in Assiut cement company farm to evaluate the effects of addition cement by-pass at levels of 0, 1, 2, 3% (1 % = 9.5 kg by-pass/plot, 2 % = 19 kg by-pass /plot and 3 % = 26.6 kg by-pass /plot) to the sandy desert soils without and with 4 ton/fed. of FYM application on the growth, yield and nutrient contents of sorghum plants. The experiment was prepared and designed as in alfalfa. The area of each soil plot was 2 m x 2 m (4 m2) and consisted of 3 rows with intra-row spacing of 30 cm. Sorghum seeds were sown at 12 kg/fed. on April 8, 2009 where 5-6 grains were added in each hill. Plants were thinned to 3 plants/hill after 4 weeks of planting. Nitrogen, phosphorus and potassium fertilizers were added to the soil at the recommended levels as ammonium nitrate, superphosphate, potassium sulfate and micronutrients. All agriculture practices were done as usual. Sorghum plants were harvested on July 20, 2009.
The results of this study could be summarized in the following:
By-pass additions to the sandy desert soil showed significant increases in available soil K and Fe. But it showed significant decreases in the available soil Mn after the soil was cultivated by sorghum. The interaction effect of by-pass and FYM application gave significant increases in the available soil K and Zn. Significant increases in the plant height after 58 and 82 days and in the total green yield and total dry matter of sorghum plants were recorded with by-pass addition. Applying the by-pass to the sandy soil at 2 % level caused increases of 111.5 and 90.8 % in the total green yield and total dry matter, respectively, of sorghum plants compared to the control. Contents of K and Cu in sorghum plants were significantly increased with by-pass additions.
2. Use of Sulfuric Acid Treated Cement By-pass and Lime Mud in the Reclamation of Saline-Sodic and Sodic Soils
2.1. Evaluation of sulfuric acid treated cement by-pass and lime mud
Soluble calcium in the lime mud treated with sulfuric acid was higher than that of the commercial gypsum and the by-pass treated with sulfuric acid. These materials can be ranked according to its content of soluble Ca in the order of lime mud treated with sulfuric acid > commercial gypsum > by-pass treated with sulfuric acid. In addition, the lime mud treated with sulfuric acid showed a lower pH value compared to the by-pass treated with sulfuric acid or to the commercial gypsum. Soluble potassium in the by-pass treated with sulfuric acid was much higher than that of the lime mud treated with sulfuric acid or that of the commercial gypsum. Moreover, both lime mud and by-pass treated with sulfuric acid contained higher levels of soluble sulfate compared to the commercial gypsum. However, the commercial gypsum was little higher in the gypsum requirements compared to sulfuric acid treated by-pass or lime mud. So, both sulfuric acid treated by-pass and lime mud can be used in the reclamation of saline-sodic and sodic soils.
2.2. Effect of sulfuric acid treated cement by-pass on the reclamation of the saline-sodic soil
A field experiment was carried out on a saline-sodic soil located at Dairut city to study the addition effect of the 25% H2SO4 treated cement by-pass on improving the properties of this soil. The sulfuric acid treated by-pass and the commercial gypsum were added to soil plots (each soil plot has an area of 2x2 m2) at a level of 50% of the gypsum requirement (4 ton/fed.) and mixed with the upper 15 cm of the surface soil layer on 1 March, 2008. On that date, three cycles of leaching-drying periods were started. Each cycle period included 4 weeks of leaching with water at a rate of two irrigations every week followed by two weeks of irrigation cessation.
The results of this study could be summarized in the following:
The application of sulfuric acid treated by-pass and commercial gypsum treatments to the saline-sodic soil resulted in significant decreases in the pH, ESP, SAR and the soluble sodium of the saturated soil paste extract values compared to the control treatment. In addition, these treatments with performing the reclamation program caused significant increases in the ECe, soluble Ca, Mg and K of the saturated soil paste extract compared to the control.
2.3. Effect of cement by-pass and lime mud additions on the properties of the reclaimed sodic soil and growth of wheat plants
A pot experiment was conducted to evaluate the use of sulfuric acid treated cement by-pass and lime mud in the reclamation of sodic soils. An artificial sodic soil was prepared in the laboratory by treating a clay soil with sodium bicarbonate through an alkalinization process. Each treatment had four replications. A randomized complete block design using a factorial arrangement of treatments was used with four replications. Plastic pots containing 3 kg of this sodic soil were used in this experiment. Nine treatments including control, by-pass, acid treated by-pass, by-pass + S, by-pass + FYM, lime mud, acid treated lime mud, LM + S and LM + FYM were evaluated. The treated soils were incubated in the Lab. for 30 days with keeping their moisture contents at the field capacity level. Then, all soils in the pots were subjected to five leaching-drying cycles for 100 days. Wheat seeds were planted, irrigated with tap water, and thinned to 30 plants/pot after germination. Nitrogen, phosphorus and potassium fertilizers were added to the soil at the recommended levels. The plants in this experiment were harvested after 64 days from planting.
The results of this study can be summarized in the following:
a. Soil pH
All by-pass and lime mud (LM) treatments showed significant decreases in soil pH values compared to the control, except by-pass + FYM and LM treatments. Effectiveness of by-pass and lime mud treatments in reducing the pH of this sodic soil was in the order of acid treated LM > acid treated By-pass > LM + S = LM + FYM > By-pass + S > By-pass > By-pass + FYM > lime mud.
b. Electrical conductivity of the saturated soil paste extract (ECe)
All by-pass treatments and lime mud treated with sulfuric acid resulted in significant reductions in the ECe of the sodic soil compared to control treatment. The treatments can be ranked according to the ECe reduction of this sodic soil in the order of acid treated By-pass > acid treated LM > By-pass + S > By-pass + FYM > By-pass > LM + S > lime mud > LM + FYM.
c. Exchangeable sodium and exchangeable sodium percentage (ESP)
All by-pass and lime mud treatments caused significant decreases in the exchangeable sodium and in the ESP of the sodic soil compared to the control. By-pass and lime mud treatments applied to this sodic soil showed reductions in the exchangeable Na in the order of acid treated LM > acid treated By-pass > By-pass + S > By-pass > By-pass + FYM > LM + S > LM + FYM > LM.
d. Sodium adsorption ratio (SAR)
Additions of all by-pass and lime mud treatments (except lime mud alone) to the sodic soil and performing the reclamation program resulted in significant reductions in SAR values compared to the control. Effectiveness of by-pass and lime mud treatments in reducing SAR values was in the order of acid treated By-pass > acid treated lime mud > By-pass + S > By-pass + FYM >By-pass > LM + FYM > LM + S > lime mud.
e. Soluble cations and anions in the saturated soil paste extract
Sulfuric acid treated by-pass, sulfuric acid treated lime mud and lime mud + FYM treatments caused significant increases in the soluble calcium of the sodic soil compared to the control, with an increasing order of acid treated By-pass > acid treated LM > LM+FYM.
Also, acid treated by-pass, acid treated LM and LM + S treatments resulted in significant increases in the soluble magnesium compared to the control treatment. The treatments showed increases in the soluble Mg in the order of acid treated By-pass > acid treated LM > LM + S > LM + FYM > LM > By-pass + S > By-pass.
Significant reductions in the soluble sodium were observed in all by-pass treatments as well as acid treated LM and LM + S added to this soil Therefore, treatments of by-pass and lime mud showed decreases in the soluble sodium in the order of acid treated By-pass > acid treated LM > By-pass + S > By-pass + FYM > By-pass > LM + S.
All by-pass and lime mud treatments, except lime mud alone and LM + S added to the sodic soil resulted in significant increases in the soluble potassium. The increases in the soluble potassium were in the order of By-pass + FYM > By-pass > By-pass + S > LM + FYM > by-pass +H > acid treated LM > LM + S > LM.
f. Available phosphorus and potassium
Additions of by-pass + FYM, lime mud alone, LM + FYM and LM + S to this sodic soil caused significant increases in the available P, while by-pass alone and acid treated LM treatments showed non-significant increases in the available P. So, these treatments resulted in increases in the available P in the following order LM + FYM > By-pass + FYM > lime mud > LM + S > By-pass > acid treated LM.
All by-pass treatments as well as LM+FYM treatment used in the reclamation of the sodic soil resulted in significant increases in the available K with an increase order of By-pass + FYM > By-pass > By-pass + S >LM + FYM > acid treated By-pass.
g. Total fresh and dry matter yields of wheat
Significant increases in the total fresh yield of wheat plants grown on the sodic soil were observed with all treatments of by-pass and lime mud except LM+FYM treatment used in the reclamation of this sodic soil compared to the control. Effectiveness of these treatments on the total fresh yield increase was in the order of acid treated By-pass > By-pass + S > acid treated LM > By-pass > LM + S > By-pass + FYM > lime mud > LM + FYM. Moreover, acid treated by-pass, by-pass + S, by-pass, acid treated LM and LM + S treatments showed significant increases in the total dry yield of wheat plants grown on the sodic soil with an increasing order of By-pass + S > acid treated LM > acid treated By-pass > By-pass > LM + S.
h. Phosphorus and potassium contents of wheat
Lime mud + FYM treatment showed a significant increase in the phosphorus content of wheat plants grown on the sodic soil, but LM + S treatment resulted in a non significant increase in P content of wheat. On the other hand, by-pass + S treatment caused a significant decrease in P content of wheat plants. Acid treated lime mud, acid treated by-pass, by-pass and LM+FYM treatments caused significant increases in the potassium content of wheat plants. However, other treatments showed non significant decreases in K content of wheat. Therefore, these treatments resulted in increases in the potassium content of wheat plants in the order of acid treated LM > By-pass > acid treated By-pass > LM + FYM > By-pass + S > LM > By-pass + FYM > LM + S.
3. Use of Cement By-pass in the Remediation of Heavy Metal Contaminated Soils
3.1. Batch experiment
Adsorption of Cd, Cu, Ni and Pb on cement by-pass was studied, in a batch experiment of four replications, by adding 25 ml of solutions containing concentrations of 10, 20, 30, 40, 50, 100 and 200 mg l1 of these heavy metal cations to 1 g of cement by-pass samples. The respective metal cations were applied as Cd (NO3)2, Cu (NO3)2, Ni (NO3)2 and Pb (NO3)2 forms that were diluted in distilled water containing 10 mM Ca (NO3)2 as a background. The suspensions were shaken for 24 h at room temperature, and then centrifuged. The supernatant liquids obtained after centrifugation were analyzed for the remaining heavy-metal cations in the solutions using the atomic absorption.
The results of this experiment could be summarized in the following:
a. Competitive adsorption isotherms
The adsorption data of Pb and Cd on cement by-pass were generally well correlated to the Langmuir model while, those of Pb, Cu, Cd and Ni were well described by the Freundlich one. According to the Langmuir maximum adsorption capacity by cement by-pass, the studied heavy metals could be ranked in the order of Cu > Ni > Pb > Cd. In addition, the bonding energy coefficients of Ni, Cu and Pb were much lower than that of Cd.
b. Distribution coefficients (Kd) and relative adsorption selectivity
Overall initial concentrations of these studied metals, the highest Kd values were found for Cd and followed by those of Cu and Ni that showed intermediate Kd values. However, low Kd values were pronounced for Pb. This implies that Cd and especially Cu are the most strongly sorbed metals by cement by-pass, whereas Ni and Pb are the least sorbed ones. The Kd value of Cd, Cu and Ni increased with increasing the initial metal concentration added to cement by-pass, while, the Kd value of Pb decreased with increasing the added initial metal concentration to cement by-pass. This indicates that Pb, Cu, Cd and Ni are strongly sorbed metals by cement byproduct.
c. Removal of Pb, Cu, Cd and Ni from solutions by cement by-pass
The sorbed amount of Pb, Cu, Ni and Cd by cement by-pass increased with increasing the initial concentration. The sorbed amount of Pb, Cu, Ni and Cd by cement by-pass ranged from 1.21 to 22.75 mmol/kg, from 3.93 to 78.64 mmol/kg, from 2.22 to 44.47 mmol/kg and from 4.24 to 85.05 mmol/kg, respectively, with an adsorption percentage ranged from 100 to 94.3 %, 99.9 to 100 %, 99.9 to 100 % and 99.6 to 99.9 at the minimum and the maximum initial concentration, respectively.
3.2. Effects of cement by-pass on the soluble and exchangeable forms of Zn, Cd, Cu and Pb in two contaminated soils
A laboratory experiment was carried out to study the addition effects of cement by-pass at levels of 1 and 2% to two contaminated soils (Arab El-Madabegh at Assiut city and El-Gabal El-Asfar at Cairo city) on water soluble and exchangeable forms of Zn, Cu, Pb and Cd.
The results of this experiment could be summarized in the following:
a. El-Gabal El-Asfar contaminated soil
Additions of cement by-pass to El-Gabal El-Asfar soil showed a significant decrease in the soluble Zn but significant increases in the soluble Cu and Cd of the soil. Moreover, significant increases in the exchangeable Zn, Cu, Pb and Cd were found with increasing the by-pass level. Adding the by-pass to this soil at the level of 2% showed increases in the exchangeable form of Zn, Cu, Pb and Cd to reach 634, 74, 14 and 77 %, respectively, compared to the control. However, by-pass additions to this soil at a level of 2% caused decreases in the soluble Zn of 77.3 %, compared to the control.
b. Arab El-Madabegh contaminated soil
The application of cement by-pass to Arab El-Madabegh contaminated soil showed significant decreases in the soluble Zn and a significant increase in the soluble Cu compared to the control treatment. Cement by-pass caused increases in the exchangeable Zn, Cu, Pb and Cd of this soil at 1 and 2% by-pass levels.
3.3. Addition effects of washed and non-washed cement by-pass to a contaminated soil subjected to water saturation and leaching-drying regimes on yield and heavy metal contents of corn plants as well as soil labile form of some heavy metals
A greenhouse experiment was conducted to study the effect of cement by-pass additions to Arab El-Madabegh contaminated soil on the labile form of Zn, Cu, Ni, Cd and Pb and their concentrations in the shoots of corn plants (Zea mays) grown on this soil. Plastic pots were filled with 1 kg of this soil. The experiment consisted of seven treatments including an untreated soil (control), three levels of non-washed cement by-pass (0.5, 1 and 2%), and three levels of washed cement by-pass (0.5, 1 and 2%). Before cultivation, the treated soil samples in the pots were subjected to two leaching regimes (water saturation without leaching and 5 leaching-drying cycles). For three months. Then, corn plants were grown on this soil for 80 days.
a. Fresh and dry weight of shoots and roots of corn plants
Additions of 0.5 % of washed and 2 % of non-washed by-pass to this contaminated soil subjected to the water saturation regime resulted in significant decreases in the fresh weight of corn shoots compared to the control. Significant decreases in the dry weight of corn shoots were also recorded with adding 0.5 % of washed and 2 % of non-washed by-pass to this soil under the water saturation regime. However, a significant reduction in the fresh weight of the corn roots was recorded when the washed by-pass was added at the level of 0.5 % to this soil under this regime.
On the other hand, under leaching-drying regime, non-significant increase in both fresh and dry weights of corn shoots were found due to the addition of 0.5 and 1 % of the non-washed by-pass to this contaminated soil. Also, using the non-washed by-pass at 2 % level under this regime showed non- significant increases in the fresh and dry weights of corn shoots.
b. Heavy metals in corn plants
Additions of both washed and non-washed cement by-pass at all levels to this contaminated soil that was subjected to 5 leaching-drying cycles showed significant decreases in Pb concentration in corn shoots. A significant decrease in Pb concentration in corn roots was recorded with adding the non-washed by-pass at 1% level, but a significant increase in Pb concentration in corn roots was found with applying 0.5 % of non-washed by-pass to this soil under this leaching-drying regime. However, significant increases in Zn concentration in corn roots grown on this contaminated soil subjected to the leaching-drying regime were found with adding 0.5, 1 and 2% of washed by-pass as well as 1 and 2% of non-washed by-pass. Washed by-pass additions at a level of 0.5 % to this soil under the leaching-drying regime also showed a significant increase in the concentration of Cu in the corn shoots. There was a significant decrease, however, in Cd concentration in corn roots with adding 0.5 and 2% of washed by-pass as well as 1% of non-washed by-pass to this soil subjected to the leaching-drying regime. The application of washed and non-washed by-pass at levels of 0.5, 1 and 2 % to this soil under the leaching-drying regime also caused significant decreases in Ni concentration in the corn shoots. Significant reductions in Ni concentration in corn roots grown on this soil which subjected to this regime were also recorded at 1 and 2% levels of washed by-pass and 1 % level of non-washed by-pass. Significant increase in Ni concentration in the roots was found with adding 2 % of non-washed by-pass to the soil under this regime.
Significant reductions in Zn concentration in corn shoots were recorded at 0.5 and 1 % levels of washed by-pass added to the contaminated soil under the water saturation regime. Additions of 1 and 2% of washed by-pass as well as 1% of non-washed by-pass to this contaminated soil subjected to the saturation regime resulted in significant decreases in Ni concentration in corn shoots. Significant reductions in Ni concentration in the roots were also recorded under this saturation regime due to the addition of the all levels of washed by-pass to this soil. However, a significant increase in Cd concentration in corn roots was shown with adding 0.5 % of the non-washed by-pass to the soil under this regime.
c. Soil labile forms of heavy metals
additions of washed by-pass at levels of 0.5, 1 and 2% to this contaminated soil subjected to the leaching-drying regime and cultivated by corn plants resulted in significant reductions in the soil labile Pb, Cu and Ni, while the application of non-washed by-pass at these levels to this soil under this regime showed significant increases in the soil labile Cu compared to the control. However, under this regime, the soil labile Zn was significantly decreased with applying the non-washed by-pass at 1 and 2% levels. A significant reduction in the soil labile Cd was also recorded with adding 1 % of washed by-pass to this soil that was subjected to the leaching-drying regime, but non-significant increases were observed in the labile Cd with using this by-pass at 0.5 and 2% levels.
On the other hand, significant decrease in the soil labile Zn was observed due to the addition of the non-washed by-pass at 1 and 2% levels under the water saturation regime. The labile Ni of this contaminated soil subjected to this regime was significantly decreased due to the addition of the washed by-pass at the 2 % level. Applying non-washed by-pass at 0.5 and 2% levels as well as washed by-pass at 2 % level to this contaminated soil subjected to this regime showed significant increases in the labile Cu.
In conclusion, the following points appear to be of considerable significance:
1. Cement by-pass can improve the properties of the sandy desert soils as well as it can provide plants with some nutrients such as Ca and S.
2. Cement by-pass additions to the sandy desert soils increase their contents of available phosphorus, potassium and micronutrients.
3. Cement by-pass applications to the sandy soils at reasonable level (7.5%) increases the growth of alfalfa plants, especially when these by-pass treated soils are amended with organic manure such as farmyard manure.
4. Cement by-pass additions to the sandy desert soils at reasonable level (2%) increases the growth of sorghum, especially when these by-pass treated soils are amended with farmyard manure.
5. The use of cement by-pass treated with 25% sulfuric acid in the reclamation of the saline-sodic and sodic soils increases their soluble Ca and decreases their pH, exchangeable Na percentage (ESP) and sodium adsorption ratio (SAR) values resulting in improving the properties of these soils.
6. Applications of cement by-pass with sulfur and FYM to the sodic soils increases their soluble Ca and decreases their pH, exchangeable Na percentage (ESP) and sodium adsorption ratio (SAR) values resulting in improving their properties.
7. The use of lime mud treated with 25% sulfuric acid in the reclamation of the sodic soils increases their soluble Ca and decreases their pH, exchangeable Na percentage (ESP) and sodium adsorption ratio (SAR) values resulting in improving the properties of these soils.
8. Applications of lime mud with sulfur and FYM to the sodic soils increased their soluble Ca and decreased their pH, exchangeable Na percentage (ESP) as well as sodium adsorption ratio (SAR) values resulting in improving their properties.
9. Some heavy metals such as Cu, Cd, Pb and Ni are strongly sorbed by the cement by-pass. This implies that these metals will not pose threats to both ground water and growing plants if this by-pass is added to heavy metal contaminated soils. Will decrease the hazard of heavy metals.
10. Solubility and exchangeability of Zn, Cu, Cd, and Pb in contaminated soils was significantly decreased after cement by-pass addition. This implies that soluble and exchangeable soil forms of these soils may transform to other immobile forms due to by-pass addition.
11. The use of cement by-pass as an immobilizing substance is promising for the reduction of most mobile forms of heavy metals and thus, it may reduce their availability and toxicity for plants.
12. The concentrations of all studied heavy metals were generally greater in corn roots than these of shoots.
Therefore, it is recommended to use cement by-pass at the level of 2% in improving the properties and nutrient status of sandy soils. It is also recommended to use. 25% sulfuric acid treated cement by-pass or 25% sulfuric acid treated lime mud in the reclamation of saline-sodic and sodic soils. Moreover, cement by-pass may be used as immobilizing substance to reduce levels of heavy metals in contaminated soils as well as sewage waters and sludge.