Hamidreza BEHRAVAN; REZA KHORASANI; Amir Fotovat; Abdol Amir Moezei; Mehdi Taghavi
Abstract
Introduction: Sugarcane cultivation has been revived in Khuzestan province of Iran since the 1960s and due to good results, it gradually began to grow from north to south of this region. Currently, sugarcane is cultivated in more than 100,000 hectares of the provinceand almost 25% of the country needs ...
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Introduction: Sugarcane cultivation has been revived in Khuzestan province of Iran since the 1960s and due to good results, it gradually began to grow from north to south of this region. Currently, sugarcane is cultivated in more than 100,000 hectares of the provinceand almost 25% of the country needs for sugar arebeing produced in this region. Sugarcane fields of Khuzestan province are mainly rich in lime percentage and poor in organic matter and phosphorus. Soil pH in this region of the country also is about 8-8.5 and phosphorus uptake by plants and phosphorus fertilizer efficiency in these soils (alkaline and calcareous soils) are expected to be low. The optimum use of phosphorus fertilizer and proper phosphorus uptake is essential for the quantitative and qualitative function of sugarcane plants. Due to the very low mobility of phosphorus in the soil, its uptake by plants such as sugar cane is affected by number of soil and plant factors (especially plant root characteristics). Changes in these factors can lead to a reduction or increase of P uptake by the crop.
Materials and Methods: Because of the role of organic compounds in the improvement of mobility and phosphorus uptake, the use of organic material has been considered in many types of research. Organic compounds can play a direct and indirect role in plant factors and in phosphorous uptake improvement. In this regard, a greenhouse pot experiment was conducted in 2016-2017 at Farabi Agro Industry Co, 35 km south of Ahvaz, Iran (48º 36' E, 30º 59' N). This research carried out by using three levels of humic acid (immersion of settes in three concentrations of 0, 0.3 and 0.5% of humic acid) as well as three levels of phosphorus fertilizer (triple super phosphate) 0, 50 % and 100% of the recommended amount in the region (250 kg/ha) in two different harvesting periods (45 and 90 days after planting). The experiment set up as a factorial, based on complete randomized design with three replicates. In this experiment, the effects of different levels of phosphorous fertilizers and humic acid on aerial part (shoot height, shoot dry weight), underground part (root length, root dry weight and root hair length), and also root CEC of sugar cane plant in two harvest times were studied. Finally, uptake and influx of phosphorus in different treatments were investigated.
Results and Discussion: As the results show, although the range of the changes was different, the use of humic acid could improve almost all of these factors. Shoot height, shoot dry weight in humic acid treatments showed a significant increase in both harvests compared to non-used humic acid treatments and also in phosphorus fertilizer treatments as the fertilizer levels rose. These results show that humic acid can increase the uptake of phosphorus from the soil reservoir (treatments without phosphorus fertilizer) and source of soil and phosphorus fertilizer (phosphorus fertilizer treatments). The underground plant parts have also shown similar results. Root length and root dry weights have also been shown positive results in humic acid treatments. Therefore, an increase in phosphorus uptake in non-use phosphorous fertilizer treatments or phosphorous fertilizer treatments, along with humic acid, relative to non-humic acid treatments could be explained. The humic acid application seems to increase the uptake capacity of phosphorus from soil and fertilizer sources by increasing root length and root dry weight. In addition, the use of humic acid in alkaline soil can increase the solubility of phosphorus in water and therefore the phosphorus uptake by the roots of the plant could be increased. Based on the results, using humic acid due to improved phosphorus fertilizer use efficiency, phosphorous uptake by plant is expected to be increased and hence the fertilizer use would be reduced. Phosphorus influx results had not the same direction with uptake and application of phosphorus fertilizer. P influx results showed an inverse relationship with root length. In other words, phosphorus uptake was more dependent on the root growth.
Conclusion: This study showed that it is possible to use humic acid in the practical form during the cultivating of sugarcane setts, but it seems that further research is needed to examine other important points such as the use of humic acid during plant growth season and other its application forms, such as spraying or application in irrigation water.
Mohammad Taghi Kouhiyan Afzal; Ahmad Farrokhian Firouzi; Mehdi Taghavi
Abstract
Introduction: Nowadays pollution of sand columns and water resources with hexavalent chromium is enhancing due to the increase of industrial and agricultural activities. In recent years nanoscale zerovalent iron particles (nZVIP) have been used according to special properties comprising of high surface ...
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Introduction: Nowadays pollution of sand columns and water resources with hexavalent chromium is enhancing due to the increase of industrial and agricultural activities. In recent years nanoscale zerovalent iron particles (nZVIP) have been used according to special properties comprising of high surface area, high reaction sites, non-toxic, non-expensive and high potential for removal of pollutants such as hexavalent chromium from sand columns and water. The size range of Zerovalent iron nanoparticles is less than 100 nm. So they could potentially be transported into the subsurface and finally be mixed with the target pollutants. Chromium is one of the steely-grey, lustrous and toxic heavy metals with high toxicity potential. Upon chromium (VI) toxicity this element is classified as a primary contaminant. Chromium (III) compounds is not toxic and hazardous and are grouped as one of the beneficial elements for human and other animals, while the toxicity and carcinogenic properties of hexavalent chromium have been realized for a long time in all over the world. Application of polymers as nZVIP stabilizers diminishes flocculation and sedimentation of nanoparticles. So usage of such polymers may lead to decreasing of particle size, enhancing reactivity and increasing particle transport in column and continuous medium studies. The objectives of this study were: (1) synthesis and characterization of different surface modified nZVIP with some polymers including Polyacrylamide (PAM) and Guar gum (GG), (2) the removal of hexavalent chromium ions from sand columns by application of different stabilized nZVIP, (3) investigation the impacts of different experimental situations on hexavalent chromium removal from sand columns including primary nZVIP dosages and primary hexavalent chromium dosages, and (4) evaluation nZVIP transportation in sand columns.
Material and Methods: In this research, nZVIP were synthesized using chemical reduction of ferrous sulfate by sodium borohydride. Guar gum (GG) as a green and environmentally friendly coating and polyacrylamide (PAM) as an anionic and biodegradable polymer were applied for stabilizing of nanoparticles. Zeta potential values were determined by a ZetaPlus zeta-potential analyzer from Brookhaven Instruments Corporation and the measured values were gathered from a suspension containing 5 mg zero valent iron nanoparticles in 100 mL of 1 mM NaCl solution, at room temperature. The hydrodynamic diameter of nanoparticles was determined using a ZetaPlus zeta potential analyzer and the Brownian movement of particles was related to nanoscale zerovalent iron particles hydrodynamic diameter. The morphology of zerovalent iron nanoparticles was determined by scanning electron microscope (SEM). Furthermore, the size of the synthesized nanoparticles was considered using a transmission electron microscope (TEM) via image measuring software.
Results and Discussions: The results showed by increasing of nanoparticle and hexavalent chromium dosage the removal efficiency of chromium increased and decreased from sand columns, respectively. Increasing of hexavalent chromium dosage from 40 to 80 mg/L in sand columns lead to more excessive chromium ions at sand columns and diminishing of hexavalent chromium removal efficient from sand particles. When the dosage of nanoscale zerovalent iron particles raised from 1 to 3 g/L and while the concentration of Cr (VI) was on a constant value of 100 mg/L, the effective reaction sites for hexavalent chromium removal would increase and so the removal performance would enhance according to the nanoparticle dosages. The findings of the current study also revealed when ionic strength and nZVIP dosage enhanced, the transportation of nZVIP decreased in sand columns. By enhancing the concentration of nZVIP, the surface reaction sites of nZVIP increased and hence the efficiency of chromium removal raised from sand columns.
Zeta potential is a good parameter for evaluating the colloidal stability. This parameter is an index of stability that reflects the electrostatic repulsion forces between charged particles. By shifting the zeta potential values to the higher records (more negative) the magnitude of repulsion forces among the particles will increase and the stability of them will enhance as a result. In this research the achieved zeta potential records for synthesized nZVIP showed that PAM-stabilized nZVIP and non-stabilized nZVIP had the most and the least stability values respectively.
Conclusion: The final results of this study revealed that increasing dosages of synthesized zerovalent iron nanoparticles enhanced the removal efficiency of nitrate and hexavalent chromium from sand columns. When dosages of Cr (VI) increased the removal efficiency of current pollutants decreased. TEM results showed the order of particle sizes were upon to the following trend: PAM-nZVIP < GG- nZVIP < Bare- nZVIP. So PAM stabilized zerovalent iron nanoparticles and the bare nanoparticles were the smallest and largest sizes of all. The efficiency of hexavalent chromium removal and nanoparticle transormation were according to the following trend: polyacrylamide (PAM)- nZVIP> Guar gum (GG)- nZVIP> Bare- nZVIP
