tahereh mansouri; Ahmad Golchin; Mohammad Babaakbari
Abstract
Introduction: Arsenic (As) is the twentieth element in earth's crust and the contamination of soils and ground waters by it is common and disturbing. In addition to geological factors and soil parent material, human activities such as mining and smelting, coal combustion and the use of arsenic-containing ...
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Introduction: Arsenic (As) is the twentieth element in earth's crust and the contamination of soils and ground waters by it is common and disturbing. In addition to geological factors and soil parent material, human activities such as mining and smelting, coal combustion and the use of arsenic-containing compounds such as insecticides, pesticides, wood preservations and etc lead to the accumulation of high levels of this metal in the soils. Long-term exposure to As can lead to skin, bladder, lung, and prostate cancers.The presence of As in soil and water causes its transfer to different parts of the plant. Because of the crucial role of corn in human nutrition, investigation of the uptake, transport and accumulation of As in different parts of this plant is very important, thus this study was carried out with the aims of evaluating the response of corn to the presence of As in the environment and its impact on concentrations of phosphorus (P), iron (Fe), zinc (Zn) and manganese (Mn) in this plant.
Materials and Methods: Soil samples were collected and after air drying, passed through a 2 mm sieve and analyzed for some physico-chemical properties. The samples were then artificially contaminated by different levels of arsenic (0, 6, 12, 24, 48 and 96 mg/kg) using Na2HAsO4.7H2O salt and incubated for 6 months, and then planted to corn. Before planting, the concentration of available As was determined. At the end of growth period, mean height of plants was measured and then the above and below ground parts of plants were harvested, washed, dried and digested using a mixture of HNO3 and H2O2. The concentrations of As, P, Fe, Zn and Mn in plant extracts were measured. Statistical analyses of data were performed using SAS software and comparison of means carried out using Duncan's multiple range test.
Results and Discussion: The results indicated that As concentration increased both in root and in shoot with increasing As concentration. The highest As concentrations in corn root and shoot were 383.41 and 59.56 mg/kg, respectively. Arsenic accumulation in root was higher than the shoot, so that the concentrations of arsenic in the roots of plants grown at 6, 12, 24, 48 and 96 mg As/ kg of soil, were 1.88, 1.99, 3.13, 4.96 and 6.44 times higher than their concentrations in shoot, respectively. Corn was sensitive to As stress and growth of it reduced by increasing the level of soil As. Mean heights of plants grown in soils polluted with 6, 12, 24, 48 and 96 mg As/kg decreased compared to control by 10.74, 25.30, 38.99, 59.71 and 76.66%, respectively. The rate of reduction of dry weights of roots of plants grown in soils polluted with 6, 12, 24, 48 and 96 mg As/kg were 10.66, 30.20, 54.64, 81.65, 95.94 % and ones of shoot were 11.30, 27.25, 47.14, 77.66 and 95.22%, respectively, which showed corn root was more sensitive to As than shoot. Arsenic uptake by root and shoot increased with increasing the As levels to 48 and 24 mg/kg, respectively, but at higher levels of As it decreased, this showed that up to these levels, increasing arsenic concentrations in plant parts surpassed from the decreasing dry weights of them and the amount of uptake obtained by multiplying these two factors, increased. Phosphorus concentrations in root and shoot increased and decreased, respectively, with increasing soil As concentration, and this matter showed As reduced P translocation from the root to the shoot of plants. Iron and Zinc concentrations in root and shoot decreased but Manganese concentration increased with increasing soil As concentration.
Conclusions: The results of this study showed that the corn plant is very sensitive to arsenic and its growth decreased even in the presence of low concentrations of arsenic. Arsenic accumulation in root was higher than the shoot. Arsenic changed the concentration of nutrients in the soil and the corn, So that increased the available P concentration and reduced the available concentrations Fe, Zn and Mn. It also reduced the translocation of P, the concentration of Fe and Zn in the root and shoot. The statement that toxicity limits plant As uptake to safe levels was not confirmed in our study. If corn plants are exposed to a large concentration of As, they may accumulate residues which are unacceptable for animal and human consumption.
tahereh mansouri; Ahmad Golchin; Zahra Rezaei
Abstract
Introduction: Selecting the right source of nutrient in a particular cropping situation requires a consideration of economic, environmental, and social objectives. One of the objectives is to keep all nutrient losses to a minimum. Since the use of nitrogen chemical fertilizers began more than 100 years ...
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Introduction: Selecting the right source of nutrient in a particular cropping situation requires a consideration of economic, environmental, and social objectives. One of the objectives is to keep all nutrient losses to a minimum. Since the use of nitrogen chemical fertilizers began more than 100 years ago, it has been recognized that it can be lost as gaseous ammonia when an ammonical fertilizer is applied to calcareous soil. A process by which nitrogen exit from the soil in form of ammonia and enter to the atmosphere is called volatilization. Agricultural practices (use of chemical and animal fertilizers) are known as major sources of ammonia volatilization into the atmosphere. Nitrogen losses not only economically but also in terms of environment pollution is important. Ammonia volatilization is one way of the nitrogen losses from agricultural and non-agricultural ecosystems. A variety of soil chemical properties interact with environmental conditions at the site of the fertilizer application to determine the extent of NH3 loss. This article study some of the major factors that contribute to NH3 loss from N fertilizer. The aims of this study were to evaluate the impacts of concentrations of soil calcium carbonate (experiment 1), plant residue application (experiment 2), nitrogen fertilizer rate and source on volatilization of ammonia from soil.
Materials and Methods: Two factorial experiment with 36 treatments, three replications and 108 experimental unit for 25 days at a constant temperature of 30 ° C were conducted using a completely randomized design. The experimental treatments were three concentrations of soil calcium carbonate (20, 27 and 35% in experiment 1), three alfalfa plant residue application rates (0, 2.5 and 5% w/w in experiment 2), three rates of nitrogen (0, 200 and 400 kg/ha), four sources of nitrogen (urea, ammonium nitrate, ammonium sulfate and urea- sulfuric acid). Fertilizers were added to soil samples in form of solution and the moisture of soils was brought to field capacity. Samples were placed into special jars and amount of nitrogen volatilization were measured.
Results and Discussion: The results showed that ammonia volatilization from soil increased as the concentration of soil calcium carbonate, rates of nitrogen and alfalfa plant residues application increased. In first experiment the highest amount of nitrogen volatilization rate, as ammonia (33.21 µgr N/gr soil) was measured from 400kgN/ha soil for urea fertilizer and 35 percent calcium carbonate. Also the lowest amount (11.99 µgrN/gr soil) was obtained from 20 percent calcium carbonate without application of any nitrogen fertilizer. In this experiment, with an increase in the amount of soil calcium carbonate by 15%, the amount of volatilized nitrogen in the form of ammonia were six times. By increasing the amount of soil calcium carbonate of from 20 to 27% the amount of nitrogen losses as ammonia slightly increased but with a further increase of calcium carbonate (from 27 to 35%) the amount of nitrogen losses increased a lot and this increase was higher than the initial increase. The presence of calcium carbonate in the soil increase soil pH and ammonia volatilization. In second experiment the highest amount of nitrogen volatilization rate, as ammonia (32.28 µgr N/gr soil) was measured from 400kgN/ha soil for urea- acid sulfuric fertilizer and 5 percent of plant residues. Also the lowest amount (0.33 µgrN/gr soil) was obtained from soil without application of any nitrogen fertilizer and plant residues. The most of nitrogen losses in the form of ammonia in the amount of 15.34 micrograms per gram of soil was obtained from level of 5% of alfalfa residue. With the 2.5 percent increase in the alfalfa residue rate, ammonia volatilization from soil increased in rate of 3.24 micrograms per gram of soil and by increasing it from 2.5 to 5%, nitrogen volatilization increased in the amount of 8.88 micrograms per gram of soil.
Conclusion: The loss of nitrogen as ammonia with application of nitrogen fertilizers and without application of residues was as urea> ammonium sulfate> ammonium nitrate > urea-sulfuric acid and with application of crop residues was as urea-sulfuric acid
T. Mansouri; A. Golchin; J. Fereidooni
Abstract
Introduction: Soil contamination by heavy metals is one of the most important environmental concerns in many parts of the world. The remediation of soil contaminated with heavy metals is necessary to prevent the entry of these metals into the human food chain. Phyto-extraction is an effective, cheap ...
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Introduction: Soil contamination by heavy metals is one of the most important environmental concerns in many parts of the world. The remediation of soil contaminated with heavy metals is necessary to prevent the entry of these metals into the human food chain. Phyto-extraction is an effective, cheap and environmental friendly method which uses plants for cleaning contaminated soils. The plants are used for phytoremediation should have high potential for heavy metals uptake and produce enormous amount of biomass. A major problem facing phyto-extraction method is the immobility of heavy metals in soils. Chemical phyto-extraction is a method in which different acids and chelating substances are used to enhance the mobility of heavy metals in soil and their uptake by plants. The aims of this study were: (a) to determine the potential of radish to extract Pb from contaminated soils and (b) to assess the effects of different soil amendment (EDTA and H2SO4) to enhance plant uptake of the heavy metal and (c) to study the effects of different levels of soil Pb on radish growth and Pb concentrations of above and below ground parts of this plant.
Materials and Methods: Soil samples were air dried and passed through a 2 mm sieve and analysed for some physico-chemical properties and then artificially contaminated with seven levels of lead (0, 200, 400, 600, 800 and 1000 mg/kg) using Pb(NO3)2 salt and then planted radish. During the growth period of radish and after the initiation of root growth, the plants were treated with three levels of sulfuric acid (0, 750 and 1500 mg/kg) or three levels of EDTA (0, 10 and 20 mg/kg) through irrigation water. At the end of growth period, the above and below ground parts of the plants were harvested, washed, dried and digested using a mixture of HNO3, HCl, and H2O2. The concentrations of Pb, N, P and K in plant extracts were measured. Statistical analysis of data was performed using MSTATC software and comparison of means was carried out using duncan's multiple range test.
Results and Discussion: The results showed that the effects of the type and rate of soil amendment and Pb levels of polluted soils were significant on dry weight and Pb concentrations of above and below ground parts of radish (p< 0.01). The dry weights of above and below ground parts of radish decreased as the Pb levels of polluted soils increased. By increasing the soil pollution level (1200 mg Pb/kg soil), the total dry weight of plant decreased by %47.3 which was probably due to phytotoxicity of lead and deficiency of several essential nutrients such as phosphorus. When the Pb levels of the polluted soils increased up to 400 mg/kg soil, the concentrations of Pb in above and below ground parts of the plant increased. But when the Pb levels of the polluted soils were higher than 400 mg/kg soil, the Pb concentration in above ground part of the plant decreased but in below ground part of the plant significantly increased. The decrease in Pb concentration in above ground part of radish was probably due to formation of insoluble lead complexes in soil. the use of soil amendments increased the concentrations of Pb in above and below ground parts of radish. The Application of EDTA increased the concentration of Pb in aerial part of radish more than the application of H2SO4. Also, the application of EDTA and H2SO4at low concentrations increased dry weight of plant since, the availability of micro- and macro elements enhanced and plant uptake of nutrients increased. But at the high concentrations of these amendments the increased availability of lead caused the reduced plant growth due to phytotoxicity. But the ability of the low level of sulfuric acid to absorb lead was more than EDTA. An antagonistic effect between phosphorus and lead uptake was also observed.
Conclusion: The results of the experiment showed that the Radish plant had the ability to absorb and accumulate the high concentration of lead in its tissues and so can be used for the phytoremediation of lead-contaminated soils. The EDTA application had higher potential for enhancing lead mobility and phytoavailability than H2SO4, But the ability of the low level of sulfuric acid to absorb lead was more than EDTA. The rate of amendment also had a significant effect on phyto-extraction process and the process was adversely affected by high concentrations of the amendments.
