Soil science
Fatemeh Nooralivand; A. Farrokhian Firouzi
Abstract
Introduction Wind erosion is one of the important processes of soil degradation in arid and semi-arid regions. Increased soil surface resistance is a key factor to prevent wind erosion. Mulch can increase the resistance of soil surface against erosive agents by creating a coating on the soil surface. ...
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Introduction Wind erosion is one of the important processes of soil degradation in arid and semi-arid regions. Increased soil surface resistance is a key factor to prevent wind erosion. Mulch can increase the resistance of soil surface against erosive agents by creating a coating on the soil surface. The effectiveness of mulch on wind erosion control is on the quantity, type, and durability of the used in dust sources of Iran for stabilizing soil surface against wind erosion. In recent decades, petroleum mulch has been broadly used for stabilizing soil surface against wind erosion in dust sources of Iran. Bio-polymers (e.g. cellulose hydrogel and biochar) and naturally accessible materials (e.g. nanoclay) as environment-friendly mulches can be an alternative to chemical polymers and petroleum mulches. In arid and semi-arid regions, wetting-drying cycles play a crucial role in soil aggregate formation and strength. However, there have been limited studies assessing the impact of wetting-drying cycles on the durability of applied mulches. The main objective of this study was to assess the effectiveness of different types of mulches, including inorganic montmorillonite nanoclay, chemical polyvinyl acetate polymer, and biological biochar and cellulose hydrogel, at various time intervals. The study aimed to improve the physical and mechanical properties of soil, as well as control wind erosion in a loamy sand soil using a wind tunnel. Additionally, the durability of these mulches was evaluated over time after subjecting them to four wetting-drying cycles.Materials and Methods A factorial experiment was conducted based on completely randomized design with three replications. The factors including mulch type (four levels: nanoclay montmorillonite, polyvinyl acetate polymer, biochar and cellulose hydrogel), mulch concentration (Nanoclay montmorillonite: 0, 16 and 32, Polyvinyl Acetate polymer: 0, 8, and 16, biochar and cellulose hydrogel: 0, 65 and 200 g/m2) and duration (21, 42, 63 and 126 days). The soil used in the wind tunnel experiments was collected from a dust source in the southeast of Ahvaz (Site Number 4). Trays measuring 50×30×5 cm were filled with this soil. The soil surface was then uniformly sprayed with an emulsion of Nanoclay and Polyvinyl Acetate. Additionally, biochar and cellulose hydrogel were mixed uniformly with the soil. Water was sprayed on the soil surface to maintain a constant moisture content of 75% of field capacity. After a specified period, soil properties such as mean weight diameter of aggregates, fractal dimension, penetration resistance, and shear strength were measured. The trays were then placed in a wind tunnel, and a wind erosion test was conducted at a wind speed of 20 m/s for a duration of 5 minutes. The amount of soil loss was measured using the weight method. Then, at each time, the best treatment from each mulch (in terms of reducing wind erosion) was selected and subjected to wet and dry cycles (four cycles).Results and Discussion The results showed a significant interaction effects (p<0.01) of mulch type, mulch concentration and time factors on soil aggregate stability and fractal dimension, penetration resistance, shear strength were significant (p<0.01). Soil loss decreased in soils amended with biochar and cellulose hydrogel and increased in the case of montmorillonite and polyvinyl acetate polymer over the time. The amount of soil loss in soil amended with cellulose hydrogel decreased by 99.3%. The highest amount of soil penetration resistance and shear strength was observed in cellulose hydrogel mulch at the fourth time which were equal to 1038 and 123 kPa, respectively. Over time, the mean weight diameter of aggregates increased in the soil treated with cellulose and biochar hydrogels, but decreased in the polyvinyl acetate and montmorillonite nanoclay treatments. There was a negative correlation between aggregate stability and the fractal dimension of aggregates. In terms of soil loss, at the fourth measurement time, soils modified with cellulose hydrogels, biochar, polyvinyl acetate, and montmorillonite nanoclay experienced reductions of 99%, 71%, 84%, and 85% respectively, compared to the control. After four wet and dry cycles, the soil loss further decreased by 98%, 64%, 76%, and 81% in the respective treatments, compared to the control.Conclusion In general, it can be concluded that cellulose hydrogel presented the greatest effect on reducing soil loss and controlling wind erosion. In the soils amended with biochar and cellulose hydrogel, the effect of mulches on reducing soil loss increased over the time. However, the opposite results were found in the case of polyvinyl acetate and montmorillonite nanoclay polymers. Therefore, biochar and cellulose hydrogel in the long term and polyvinyl acetate polymer and montmorillonite nanoclay in the short term can control wind erosion. Wet and dry cycles at all durations increased soil loss. But their effect remained on soil loss reduction until the end of the fourth cycle. The results revealed that environmentally friendly biopolymers synthesized from biomass components can be considered as sustainable sources to reduce wind erosion. Bio-polymers are a new window into the use of sustainable biomaterials instead of synthetics in wind erosion control.
F. Nooralivand; A. Farrokhian Firouzi; A. Kiasat; M. Chorom; A. Akbar Babaei
Abstract
Introduction: During the recent decades, the use of N fertilizers has undeniable development regardless of their effects on the soil and environment. Increasing nitrate ion concentration in soil solution and then, leaching it into groundwater causes increase nitrate concentration in the water and raise ...
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Introduction: During the recent decades, the use of N fertilizers has undeniable development regardless of their effects on the soil and environment. Increasing nitrate ion concentration in soil solution and then, leaching it into groundwater causes increase nitrate concentration in the water and raise the risk suffering from the people to some diseases. World health organization recommended maximum concentration level for nitrate and nitrite in the drinking water 50 and 3 mg/l, respectively. There are different technologies for the removal of nitrate ions from aqueous solution. The conventional methods are ion exchange, biological denitrification, reverse osmosis and chemical reduction. Using nanoscale Fe0 particles compared to other methods of nitrate omission was preferred because of; its high surface area, more reactive, lower cost and higher efficiency. More studies on the reduction of nitrate by zero-valent iron nanoparticles have been in aqueous solutions or in the soil in batch scale. Nanoparticles surface modified with poly-electrolytes, surfactants and polymers cause colloidal stability of the particles against the forces of attraction between particles and increases nanoparticle transport in porous media. The objectives of this study were to synthesize carboxymethyl cellulose stabilized zero-valent iron nanoparticles and consideration of their application for nitrate removal from sandy soil.
Materials and Methods: The nanoparticles were synthesized in a lab using borohydride reduction method and their morphological characteristics were examined via scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier Transmission Infrared Spectroscopy (FTIR). Experiments were conducted on packed sand column (40 cm length and 2.5 cm inner diameter) under conditions of different nanoparticle concentration (1, 2, and 3 g1-1)and high initial NO3- concentration (150, 250, and 350 mgl-1). Homogeneous soil column was filled with the wet packed method. CMC-NZVI suspensions of nanoparticle in aqueous solution (0.01 M CaCl2 and 0.001MKCl) were pumped into the sand column during the injection of nitrate solution. During transport experiment, the flask containing CMC-ZVIN suspension was sonicated using a 50 KH ultrasonicator (DSA100-SK2) to prevent particle agglomeration and ensure homogeneity of the suspensions. In these experiments pore water velocity was 0.16 mms-1. Nitrate and Nitrite concentrations in the samples were measured using UV-VIS.HACH DR 5000 spectrophotometer at wavelengths 220 and 530nm, respectively, and ammonium concentration was measured by Kjeldahl method. All chemicals used in this research were of chemical grades and all solutions were prepared using deionized water (DI).
Results and Discussion: Effect of nanoparticles and nitrate concentration on nitrate reduction by stabilized nanoparticle in sand column was investigated. The Results of study indicating at the first of reaction in both cases rate and amount of nitrate reduction was increased gradually. But over time, due to saturation capacity of nanoparticles at higher concentrations of nitrate, reduction speed and amount of reduction was constant approximately. The result showed that increasing dosage of nanoparticles and decreasing the influent nitrate concentration would increase percentage of nitrate reduction. Maximum percentage of reduction (82.56%) were observed at nanoparticles concentration=3 gl-1 and high initial nitrate concentration=150 mgl-1 and minimum percentage of reduction (63.94%) were observed at nanoparticles concentration=1 gl-1 and high initial nitrate concentration=150 mgl-1. After the end of experiment time, amount of observed ammonium and nitrite was a few in the drainage water of sand column. During the reaction nitrate reduction by nano-particles, H + was used and OH- was produced therefore through reaction, environment pH increased continuously. In conditions of alkaline, ammonium release in the form of N2. Therefore reduction of the amount of ammonium may due to high pH of environment reaction or fixation of ammonium in the surface colloidal of particles in porous medium. Nitrite is an intermediate product and due to the reaction conditions can be converted to ammonia or nitrogen gas. The final product of reduction would be nitrogen gas, and produced nitrite and ammonium was less than 2%.
Conclusion: The results indicate that, in all experiments (effect of nanoparticle and nitrate concentration on nitrate reduction), amount of observed ammonium and nitrite was a few in the drainage water of sand column and most of the nitrate converted to nitrogen gas. Since maximum concentration level of ammonium in drinking water is 50 times less than nitrate concentration, nitrogen gas is an ideal product in water treatment process. Carboxymethyl cellulose prevents agglomeration ZVI nanoparticles and enhanced the reactivity and transport of nanoparticle in the porous media. The findings of this research demonstrated that carboxymethyl cellulose-stabilized zero-valent iron nanoparticles have a high potential for reduction of nitrate in aqueous solutions and porous media. Therefore, it can be used as an effective method for removing nitrate from water.
