Irrigation
F. Saberinia; M.B. Farhangi; N. Yaghmaeian Mahabadi; R. Shokati; N. Ghorbanzadeh
Abstract
Introduction Overuse of antibiotics and their entry into the environment is a global concern today. Much of the antibiotics taken by animals and humans are excreted unchanged and found in their feces which enter the environment through livestock waste and municipal wastewater disposal. Uncontrolled ...
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Introduction Overuse of antibiotics and their entry into the environment is a global concern today. Much of the antibiotics taken by animals and humans are excreted unchanged and found in their feces which enter the environment through livestock waste and municipal wastewater disposal. Uncontrolled release and continuous introduction of antibiotics to the environment induced antibiotic resistance in microorganisms living in other habitats which pose a potential hazard to existing aquatic ecosystems and animals. Rivers act as the main sink for the effluents that distribute antibiotics and antibiotic resistant microorganisms in the environment. This study aimed to investigate the antibiotic resistant index (ARI) in Goharrood River. Seasonal variations and source of contamination, focusing on urban surface wastewater of Rasht, were investigated through sampling of river water and sediment in different points along the river during four seasons of a year.Materials and MethodsThe water and sediment of the river were sampled at three points along the river (focused on river course in Rasht city), in autumn, 2016 and in winter, spring and summer, 2017. The number of antibiotic resistant heterotrophic and coliform bacteria were counted via colony count method in the antibiotic supplemented 100 µg/mL Nutrient Agar and Eosine-Methylene Blue agar media respectively. Cephalexin, gentamicin, doxycycline, ciprofloxacin, and trimethoprim antibiotics were tested in this study. ARI was calculated by dividing number of bacteria colonies (heterotrophic and coliform bacteria) in plates supplemented with antibiotics to the number of colonies in control plate (without antibiotic). Escherichia coli as an indicator coliform bacterium was isolated from water and sediment samples (12 strains; 4 season and 3 sampling points) and their resistant pattern to these antibiotic was also tested by disk diffusion (Kirby-Bauer) method in Mueller-Hinton agar medium. The inhibition zone (ZOI) of E. coli growth was measured and its sensitivity/resistant was assessed based on CLSI standard protocol. The calculated ARI of heterotrophic and coliform bacteria of water and sediment of the River and the determined ZOI of E. coli isolated from water and sediment were analyzed by repeated measures of factorial arrangement in a completely randomized design format by SAS software package. Factors included sampling point at 3 levels (before entering river to the Rasht city; A, in the Rasht city; B, and after river exit from the Rasht city; C), and antibiotics at 5 levels (cephalexin, gentamicin, doxycycline, ciprofloxacin, and trimethoprim) as main plot and sampling time at 4 levels (autumn, winter, spring, and summer) as sub-plot.Results and Discussion The highest ARI value of water heterotrophic bacteria was obtained to cephalexin at the sampling point C. Mean ARI of water heterotrophic bacteria to all antibiotics (regardless of type of antibiotic) at three points of A, B and C was 3.77, 4.54 and 7.53%, respectively. The highest ARI levels of heterotrophic and coliform bacteria in water were obtained in the summer season. In fact, the change of seasons and clearly the summer season controlled the ARI in water bacteria rather than the type of antibiotics. So that in this season 30.78% of water heterotrophic bacteria were resistant to ciprofloxacin antibiotic and about half (50.78) of the river water coliforms were resistant to cephalexin. Although ARI for heterotrophic and coliform bacteria was lower in sediment rather than that in water, the highest ARI levels of heterotrophic and coliform bacteria in sediment were obtained against cephalexin in autumn and winter, respectively. In general, the mean ARI in water and sediment bacteria was as follows: cephalexin > gentamicin > ciprofloxacine > doxycycline > trimethoprim. The lowest ZOI value for E. coli was obtained against cephalexin. Therefore, in all three sampling points, isolated E. coli bacteria from water and sediment were resistant to cephalexin. In the study of the sampling time and sampling point interaction, it was also seen that the lowest ZOI of E. coli was in autumn and at sampling point C. Therefore, it seems that E. coli has become resistant to antibiotics when river crosses the city.Conclusion According to the results of this study, Goharrood river is contaminated with antibiotic-resistant, especially cephalexin resistant bacteria and it may distribute pollution downstream. If the river water is used in aquaculture and irrigation of downstream agriculture fields, the antibiotic resistant bacteria may be spread in the other ecosystems and finally may enter the human food chain.
E. Hashempour; M.B. Farhangi; N. Ghorbanzadeh; M. Fazeli Sangani
Abstract
Introduction: Due to the increasing development of edible oil processing industries, large amounts of wastewater and solid wastes (SW) are inevitable in these industries. Organic wastes can be used as soil conditioners in agriculture due to the high content of organic matter and nutrient loads. Phosphorus ...
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Introduction: Due to the increasing development of edible oil processing industries, large amounts of wastewater and solid wastes (SW) are inevitable in these industries. Organic wastes can be used as soil conditioners in agriculture due to the high content of organic matter and nutrient loads. Phosphorus solubilizing bacteria including Bacillus spp., Pseudomonads and Rhizobium spp. can release phosphorus from insoluble organic and mineral sources in soil. Most soils in the semi-arid regions, including southern parts of Guilan province, have low organic matter content and do not support plant cultivation due to the low fertility and instability of soils. Hence, industrial wastes can be applied as a suitable and low-cost source of organic materials and nutrients in these soils. As phosphorus is one of the most important essential nutrients in plant nutrition which is also present in oil refinery soild wastes and P solubilizing bacteria can release phosphorus from the organic phase of the wastes and make it available in the soil solution, this study aimed to investigate the available phosphorus (Pava) content of soil after simultaneous addition of olive refinery-solid wastes and P solubilizing Bacillus spp.
Materials and Methods: the solid waste obtained from Ganje Rudbar oil refinery plant (located in Rudbar, Guilan province) and a soil sample was collected from a surface layer (0-30 cm) of a pasture, located in Lowshan area (Guilan province). A native strain of Bacillus sp. was isolated from the sampled soil based on its P-solubilizing ability in Sperber medium. An indicator strain, Bacillus persicus was also included in the experiments. P-solubilizing ability of the indicator strain was also evaluated in Sperber medium. The experiment was conducted in a completely randomized design based on factorial arrangement and three replications. Factors included three levels of solid waste (0, 2 and 4%), three levels of inoculated bacteria (no bacteria, native Bacillus sp. and Bacillus persicus) and eleven sampling times (0, 2, 7, 14, 28, 42, 56, 86, 116, 146, and 176 days). Different levels of solid waste were added to the soil, inoculated with bacteria (106 cell/g), and incubated at laboratory condition (~25 ºC) for six months. The moisture content of the soil mixtures fixed around 0.7 FC and kept constant during the incubation period. Sampling was done at desired times. The pH, organic carbon (OC), soil Basal Respiration (BR), available phosphorus concentration (Pava), and phosphatase enzyme activity were measured in soil samples. Data analysis and means comparison were done by Duncans’ test using SAS software package.
Results and Discussion: The studied soil was loam in texture, and had slightly alkaline pH, moderate Pava, and low OC content. The studied solid waste contained considerable OC and total P load. The effect of solid waste (SW), bacteria, sampling time and their interactions were significant on most of the measured characteristics (p < 0.05). SW application decreased soil pH and mixtures inoculated with native Bacillus sp. had lower pH values compared to those inoculated with Bacillus persicus, probably due to the greater effect of Bacillus spp. on SW decomposition compared with B. persicus. The highest average BR was attained in mixtures contained 4% SW which was 1.24 and 1.73 times greater than that in mixtures contained 2 and 0% SW, respectively. While the effect of SW on soil BR was obvious, bacteria inoculation had different impact on soil organic material decomposition and the lowest BR was measured in soil (0% SW) inoculated with Bacillus persicus. OC content of mixtures increased with SW application. The highest OC level (3.21 g 100g-1) was obtained in uninoculated mixture contained 4% SW, which was significantly greater than OC levels in mixtures inoculated with bacteria (p < 0.05). The lowest OC level (3.21 g 100g-1) was observed in uninoculated soil (0% SW). SW application significantly increased Pava. The greatest Pava concentration (142.77 mg Kg-1) was attained in uninoculated mixture contained 4% SW which was not significantly different from Pava concentration in 4% SW-mixture inoculated with native Bacillus sp. (P > 0.05). In control treatments (0% SW), Bacillus persicus was efficient in P release from soil native organic carbon and/or phosphate minerals. However, among the soils contained 2% SW, those inoculated with native Bacillus sp. had the highest Pava concentration. The average Pava concentration in the 4% SW-mixtures was 136.33 mg Kg-1 which was 3.5 times greater than that in control treatment (0% SW). Although soil Pava was related to phosphatase enzyme, this enzyme activity was not affected by treatments. In the P-releasing trend, it was found that 4% SW-mixtures had the highest Pava concentration after 6 months of incubation, and bacteria inoculation made the P-release trend to be flatter compared to control.
Conclusion: The application of oil refinery plant-solid waste improved the basal respiration of the studied soil and increased available phosphorus concentration. The comparison of applied solid waste levels showed that the inoculation of soil with Bacillus bacteria had a positive effect on available phosphorus concentration only at 2% solid waste level.
Samira Abduolrahimi; Nasrin Ghorbanzadeh; Akbar Forghani; Mohammad Bagher Farhangi
Abstract
Introduction: Cadmium is considered to be one of the heavy metals with the highest toxicity, because it has high activity and a relative high dissolution rate in water and in living tissues. In recent years, due to the high volume of natural resources pollution and the inefficiency of conventional physicochemical ...
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Introduction: Cadmium is considered to be one of the heavy metals with the highest toxicity, because it has high activity and a relative high dissolution rate in water and in living tissues. In recent years, due to the high volume of natural resources pollution and the inefficiency of conventional physicochemical methods for refining these resources and the occurrence of environmental crisis, bioremediation process has been at the forefront. Microbially induced calcite precipitation (MICCP) has been considered as a novel solution for these problems, and several bacterial species have been already utilized for MICCP. MICCP based degradation of urea occurs through the ureolytic pathway. Urease (urea amidohydrolase) is an enzyme that hydrolyzes urea into one mole of carbonate and two moles of ammonia per mole of urea. In this aspect, microbial mineral precipitation products such as calcite can strongly adsorb heavy metals on their surfaces and incorporate heavy metal ions into their crystal structure. Some studies have reported MICCP-based sequestration of soluble Cd via coprecipitation with calcite was useful for Cd bioremediation. Several bacterial species have been utilized for MICCP. The endospore forming bacteria Sporosarcina pasteurii have been shown to produce high levels of urease and have therefore been extensively studied. Sporosarcina pasteurii has attracted significant attention for its unique feature of calcium carbonate precipitation, which can be easily controlled. So, In the present study the ability of Sporosarcina pasteurii bacterium has been investigated in the remediation of Cd(II) in Cd-contaminated sandy soil based on MICCP method.
Materials and Methods: Sporosarcina pasteurii (PTCC 1645) was procured from Microbial Bank of Iran (Central Collection of Industrial Fungi and Bacteria, Karaj, Iran). The bacterial strain was inoculated into NB (nutrient broth) media containing 2% urea and 25 mM CaCl2 (NBU media) and then incubated at 37◦C for 6 days. The urease activity was determined at regular time intervals by measuring the amount of ammonia released from urea according to the phenol-hypochlorite assay. Minimum inhibitory concentration (MIC) test was performed to determine the lowest concentration of cadmium chloride, which prevents the growth of bacteria. Sporosarcina pasteuriiwas inoculated into NBU media supplemented with 0.5, 1,2,4,8 and 10 mmol l-1 Cd and incubated at 37◦C, 130 rpm for 50 hours. Control flasks without adding Cd were also incubated. Bacterial growth was determined in terms of optical density (OD) by measuring absorbance at a wavelength of 600 nm at regular time intervals (0, 10, 20, 30, 40 and 50 hours) and colony-forming units (CFU) were also counted. The cadmium removal in 0.5, 1 and 2 mM cadmium solutions (based on MIC) was measured.A sandy soil from a depth of 0 to 30 cm was sampled. The soil was polluted with 10, 20, 40 and 50 mg/kg of cadmium and incubated in room temperature for two weeks. After incubation time, the cadmium remediation studies were performed at 30◦C in the beakers containing 100 g of sterilized dried contaminated soils and 200 mL of overnight grown of Sporosarcina pasteurii (~ to 107cfu ml−1) in NBU media. For each treatment corresponding control were included with the same condition but without bacteria.After 7 days of incubation, urease and dehydrogenase enzymes activity and concentration of cadmium in soluble + exchangeable and carbonate fractions were measured. The concentration of cadmium in iron-manganese oxides, organic matter and residual fractions in concentration of 50 mg/kg cadmium was also determined according to the continual extraction procedure of Tessier et al. (1979).
Results and Discussion: The amount of released ammonia by ureolytic activity of Sporosarcina pasteurii increased up to fourth day and then became almost constant.Optical density in different concentrations of cadmium decreased in comparison to control treatment after 48 hours. The minimum inhibitory concentration of cadmium for bacteria growth was 2 mM as determined by colony counting after 48 hours of incubation. Cadmium removal efficacy from solutions containing 0.5, 1 and 2 mM of cadmium was 99.6, 99.8 and 99.8%, respectively. The amounts of urease and dehydrogenase activities in the presence of bacterium were significantly higher than control treatments (P≤0.05). The results of the fractionation of contaminated soils in the absence of Sporosarcina pasteurii showed the distribution of cadmium as organic matter
Samaneh Abduolrahimi; Nasrin Ghorbanzadeh; Hasan Ramezanpour; Mohammad Bagher Farhangi
Abstract
Introduction: Rapid development of industrialization, heavy metal and radionuclide contaminants from industrial activities have posed a major threat to the environment owing to their toxicity, non-biodegradability and persistent accumulation. So various ecosystems are continuously contaminated with high ...
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Introduction: Rapid development of industrialization, heavy metal and radionuclide contaminants from industrial activities have posed a major threat to the environment owing to their toxicity, non-biodegradability and persistent accumulation. So various ecosystems are continuously contaminated with high levels of high-risk chemicals with different structures and levels of toxicity. Cadmium is one of the high-risk elements that enters the environment and can accumulate in the body of fish and other aquatic organisms, plants and livestock and be transferred to the human body. Therefore, the remediation of contaminated soils with cadmium in order to protect human health is very important. One method for remediation of pollutants is immobilization of them in the soil by adsorbents. Among the absorbents, bentonite has been identified for its unique properties, including high surface area and cation exchange capacity and adsorptive affinity for organic and inorganic ions, low cost and ease of access. If the physical and chemical properties of natural bentonites are improved by a special modification process, the adequate supplies for environmental purposes can be obtained. Among the biosorbents, rice husk has also been reported to be suitable for adsorption of cadmium and other heavy metals. This research was designed with the aim of decreasing the amount of cadmium in the soluble and exchangeable phase of a polluted soil under laboratory conditions in the presence of bentonite and rice husk. Considering that biological properties of the soil are an indicator of soil health and quality, so, after application of adsorbents, biological properties and some soil ecophysiological indices were also investigated.
Materials and Methods: The experiment was done with 13 treatments and 3 replications in a completely randomized design. Treatments were bentonite (B) and modified bentonite with iron (B-Fe), manganese (B-Mn), iron and manganese together (B-Fe-Mn), rice husk (RH), modified rice husk with phosphoric acid (RH-P) in two levels (2 and 5%) and control treatment (without adding adsorbent). Modification of bentonite was done with iron chloride (FeCl3.6H2O), manganese chloride (MnCl2.6H2O) and a mixture of FeCl3.6H2O and MnCl2.6H2O. Some of the characteristics of bentonite and rice husk adsorbents including pH, electrical conductivity, cation exchange capacity and organic carbon were measured. The contaminated soil with CdCl2 was treated with adsorbents and incubated for 2 months under constant lab conditions. After the incubation time, soil biological properties such as basal respiration, substrate-induced respiration (SIR), microbial biomass carbon (MBC), activity of some enzymes and also some ecophysiological indexes were measured.
Results and Discussion: The results showed that the basal respiration, SIR, MCB, activity of phosphatase, dehydrogenase and urease were less in the control treatment. The basal respiration and phosphatase activity in RH-P 5% treatment were 2.6 and 2.25 times more than those in the control, respectively. SIR and urease activity were highest in RH-P 5% treatment. The application of adsorbents to contaminated soil reduced soluble and exchangeable cadmium fraction. The lowest amount of soluble and exchangeable fraction of cadmium was in RH-P 5% treatment that showed 2.5 times reduction in comparison to control. In other words, immobilization of cadmium from these fractions improved soil conditions and caused increasing of biological soil properties and activity of microorganisms. The metabolic quotient was higher in the control treatment, probably due to lower microbial content, and decreased by adding adsorbents. Microbial quotient in control treatment was lower than other treatments which prove again the lower biomass carbon of control treatment. Carbon availability that is the ratio of basal respiration to SID, also was more in control in comparison to other treatments, perhaps due to the suppress or inhibition of dormant or zymogenous microbes by cadmium in the control treatment which can be stimulated to growth in the SIR experiment.
Conclusions: The results of this study revealed that cadmium with concentration of 30 mg kg-1has a toxic and inhibitory effect on the microbial activity of the soil. The addition of bentonite and rice husk adsorbents in particular modified form reduced mobility of cadmium and thus improved the biological properties of the soil and also had a positive effect on ecophysiological indexes.
The use of these adsorbents can be a cost effective, succeeded, and operative management strategy for immobilization of cadmium in contaminated soils that reducing the risk of plant reclamation, washing and entry into groundwater and food cycle.
