Soil science
E. Mirparizi; M. Barani Motlagh; S.A. Movahedi Naeini; R. Ghorbani Nasrabadi; S. Bakhtiary
Abstract
Introduction: Iron deficiency is one of the most common nutritional problems of plants in arid and semi-arid soils especially in calcareous soils. Iron is essential to many cellular activities, required for optimum growth and development, however it is insoluble in aerated soils at neutral or basic pH, ...
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Introduction: Iron deficiency is one of the most common nutritional problems of plants in arid and semi-arid soils especially in calcareous soils. Iron is essential to many cellular activities, required for optimum growth and development, however it is insoluble in aerated soils at neutral or basic pH, therefore, iron deficiency is common in these soils. The problem is usually solved by using iron synthetic chelates which is a very expensive option. There is, therefore, a need for cheaper and more effective alternatives to traditional Fe fertilizers. Several reports have shown that application of Fe factory by-product to soil tends to raise the availability of Fe and reduce Fe deficiency in plants. Application of organic compounds to soil may improve the solubility of the minerals containing micronutrients and correct their deficiencies in alkaline and calcareous soils. A large amount of slag is produced annually at the Sarcheshmeh Copper Complex, Kerman Province, Iran. So far, the copper slag, however, has not been tested as an Fe fertilizer in calcareous soils. Since about 53.8% of slag obtained from copper concentrate melting is composed of iron oxides, we, thus, examined the effect of copper slag along with organic compounds on the level of upper leaf iron, photosynthetic pigments, SPAD index, the activity of plant enzymes and the level of active iron in the upper leaves of sorghum by performing a factorial experiment in a completely randomized design.Materials and Methods: In order to study the effect of copper slag (one of by-products of melting copper concentrate in Sarcheshmeh Copper Complex, Kerman Province) and organic compounds (cow manure and pistachio skin) on total leaf iron content, photosynthetic pigments (chlorophyll a, chlorophyll b, total chlorophyll), antioxidant enzymes activity (Guiacol Peroxidase, Glutathione peroxidase) and concentration of active iron of young leaves developed of sorghum, a pot experiment was conducted in the greenhouse with three replicates per treatment. We applied experimental treatments including 5 levels of organic matter (pistachio skin, cow manure at 2 and 4 wt. % and control sample), and 11 levels of iron (copper slag, copper slag with sulfur, copper slag with sulfur and thiobacillus, acidic slag (each 2 levels each), sequesterine, foliar application of EDTA, and control sample) to a soil sample with low iron content. At the end of the incubation period, sorghum bicolor was cultured in the above treatments. Ten seeds were sown in each pot. Seedlings were thinned to 4 when they were about 10 cm high. During the growth period, pots were irrigated with distilled water as needed. Before harvesting, SPAD, the concentration of photosynthetic pigments, level of active iron and activity of plant enzymes were also measured in fresh plant samples. Furthermore, the concentration of Fe in the leaves was measured. Analysis of variance was performed using software SAS and significant differences were determined based on LSD (Least Significant Difference Test) at p < 0.05 level.Results and Discussion: The interaction between slag treatments and organic compounds showed that treatments of 4 wt. % of cow manure with slag of 4 times of recommended soil test value (C4S4, and 4 wt. % of cow manure with slag of 4 times of recommended soil test value with sulfur and thiobacillus (C4S4S°T), had significant effects on increasing photosynthetic pigments pigments (chlorophyll a, chlorophyll b, total chlorophyll), SPAD index, activity of plant enzymes (Guiacol peroxidase, Glutathione peroxidase) and active iron. The highest active iron level in the young leaves developed (54.06 mg / kg) was observed in (C4S4S°T) treatment which showed a significant increase compared to the control treatment (17.14). Increased concentration of active iron was also observed due to application of treatments (slag, organic compounds and the interaction between treatments) in sorghum young leaves. The photosynthetic pigments (chlorophyll a, chlorophyll b, total chlorophyll), SPAD index and activity of plant enzymes (Guiacol peroxidase, Glutathione peroxidase) were more correlated with active iron in young leaves developed compared to total iron concentration in these leaves. This indicates that active iron can be used as an index to detect iron deficiency.Conclusion: The higher level of active iron in the young leaves developed was more associated with physiological indices of sorghum as compared with total Fe concentration in these leaves. Therefore, this parameter can be used as an index to detect iron deficiency. In this study, increasing the level of slag consumed and consequently increasing Fe concentration in the leaf resulted in a significant increase in chlorophyll a, chlorophyll b, total chlorophyll, carotenoids and activation of the plant enzymes.
Marzieh tavanaei; somayeh bakhtiari; mehran shirvani
Abstract
Introduction: Heavy metals contamination due to natural and anthropogenic sources is a global environmental concern. Lead (Pb) is one of the very toxic heavy metals. Industrial production processes and their emissions, mining operation, smelting, combustion sources and solid waste incinerators are the ...
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Introduction: Heavy metals contamination due to natural and anthropogenic sources is a global environmental concern. Lead (Pb) is one of the very toxic heavy metals. Industrial production processes and their emissions, mining operation, smelting, combustion sources and solid waste incinerators are the primary sources of lead. This heavy metal has aberrant effects on the environment and living organisms. Hence, proper treatment of lead from soil and industrial wastewaters is very important. In order to remove toxic heavy metals from contaminated water systems, conventional methods such as chemical precipitation, coagulation, ion exchange, solvent extraction and filtration, evaporation and membrane methods are being used. These conventional methods generally have high costs and technical problems. Therefore, biosorption processes, in which microorganisms are used as sorbents, have been considered as economical and environmentally friendly options for removal of heavy metals from aqueous solution. Clay minerals are another group of sorbents used in removal of heavy metals from polluted environments. Furthermore, bacterial cells can be attached on clay mineral surfaces and form bacteria-mineral composites. These composites adsorb heavy metals and convert them into forms with low mobility and bioavailability. Pseudomonas putida is a unique microorganism with a high tendency to sorb and/or degrade certain environmental pollutants. Palygorskite and sepiolite are the fibrous clay minerals of arid and semiarid regions; their structures consist of ribbons and channels. These fibrous minerals have various applications in industry and the environment because of its large surface area and high adsorption capacity. The present study was conducted in order to determine the ability of Pseudomonas putida (P168), and its composites with palygorskite and sepiolite in lead sorption.
Materials and Methods: The bacterial strain used in the present study was Pseudomonas putida (P168) grown and maintained on Nutrient Broth (NB). The population of living and non-viable bacteria in suspension was determined by an optical microscope. The minerals used in this study were palygorskite from Florida (the Source Clay Minerals Repository, Purdue University, IN) and sepiolite from Yazd (Iran). The clay samples were ground and passed through 0.05 mm (mesh #270) sieve. The clays were then saturated with calcium chloride (0.5 M) and washed free of salts. Batch experiments were performed to measure Pb sorption by Pseudomonas putida. For this purpose, 10-ml aliquots of bacterial suspension (7.24×107 cells ml-1) were added to10 ml solutions containing Pb with concentration ranged from15-110 mg L-1. The mixtures were gently shaken at 30 ◦C for 24 h and centrifuged at 3000 rpm for 20 min. The concentration of Pb in the supernatants was finally measured by atomic absorption spectrometer. The percentage of sorbed Pb was determined by subtracting the amount of unabsorbed Pb from that initially added. Various hybrids of P. putida and clays were also exposed to solution of 0.5 mM Pb in 0.01 M KNO3 to determine the role of composites in sorption of Pb. Langmuir and Freundlich adsorption isotherms were chosen to describe the biosorption equilibrium data. GraphPad Prism 5.0 was used for determining the isothermal parameters using non-linear regression analysis. Data were analyzed with the Statistical Analysis System (SAS). Experimental design was factorial in form of complete randomized block.
Results and Discussion: Pseudomonas putida showed a considerable capacity to sorb Pb ions. Lead sorption isotherms were sufficiently fitted with the Langmuir and Freundlich models. The Pb sorption isotherms by P. putida were L-type showing a high affinity of P. putida for Pb ions. Lead sorption capacity (qmax) of P. putida was estimated to be 582.4 mg g-1 and its Langmuir constant (KL) was found to be 0.11 mg L-1. The experimental data of lead sorption (7.5-55.5 mg L-1 initial concentration) by P.putida (P168) demonstrated that about 31.5% to 78.4% of the intial concentration of Pb was taken up by these bacteria. Sorption of Pb decreased with the increase of bacteria in the bacteria-clay composites, which may be due to the occupation of adsorption sites on the clay surface by the bacteria. Composites of bacteria-sepiolite were more effective than bacteria-palygorskite in Pb sorption due to the larger channel dimensions, greater surface area, and more functional groups of sepiolite than palygorskite. LSD test showed that there were significant differences between the hybrid sorbents with different ratios and single bacterial cells in Pb sorption.
Conclusion: The results showed that P. putida and its composites with palygorskite and sepiolite clays exhibited a high potential for the removal of Pb from aqueous solutions.
