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Otters at the top of the food chain and feeding largely on fish are likely to be especially vulnerable to the effects of bioaccumulating pollutants. This research reports the first data on mercury levels found in hairs of river otters (Lutra lutra) from Iran. Between June and December 2007, we collected museum and recent collections of river otter hair. These samples were collected from several provinces of three major regions of Iran. The mean of mercury concentration for all samples (recent and museum) was 5.819±1.557 mg/kg with 95% confidence interval for the mean. The concentrations of Total Hg (THg) in hair ranged from 0.293 to 12.382 mg/kg. No significant variation among the sample regions existed. A comparison of THg concentrations between two decades (1986-1996 and 1996-2006) showed that these differences were significant (p

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Mercury levels in hepatopancreas, muscle and exoskeleton tissues of male and female green tiger prawn, P.semisulcatus, from the Persian Gulf were compared. Significantly higher levels (p<0.05) of mercury in female prawn and hepatopancreas tissue were encountered (p<0.05). Significantly higher concentration (p<0.05) of the mercury was also observed in summer than in winter season. This variation could result in internal biological cycle of the organism or variation in bioavailability of mercury in environment.

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In this study, the human health risk of mercury due to consumption of croaker (Otolithes ruber) in Mahshahr, the Persian Gulf, , was evaluated using atomic absorbtion spectrophotometer)and cold vapor techniques to measure the mercury concentration in muscle samples of 30 fresh croakers . A. Result showed the average concentration of mercury in croaker  muscle was 0.354±0.09 µg/ g of fresh wet weight, which was less than the allowable amount for human consumption determined by the international organizations such as USFDA and WHO, but more than the allowable amount for human consumption determined by MAFF and the USEPA. HQ Index was above 1 (1.18). In addition, the calculations indicated that daily and weekly mercury uptake for the Iranian consumers, according to Statistical Yearbook of Iran Fisheries organization (the amount consumed per capita),  is lower than the guideline values (PTWI and PTDI) provided by WHO, USFDA and more than USEPA. Therefore, the consumption of the croaker might be associated with some threat to the consumer’s health particularly pregnant women, fetuses and children from mercury but consumption permitted rate of 20gper dayand138 gper week is recommended for other people.

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This study reports the incidence of histological alterations in morphometric changes in the liver and ovary of Acanthopagrus latus collected from an urban stream impaired by anthropogenic activities and from a clean site (reference). Mercury concentration was determined using a standard cold vapor atomic absorption. The results showed that mercury concentration at the creek waters, and specially sediments along Mahshahr coast, was higher than in the other marine environment, and in Zangi was lower than in the other sites of sampling. Several liver lesions were identified, including enlarged and lateral nuclei, nuclear degeneration and vacuolation, oncotic, apoptic, focal, massive, centrilobular and periportal  necrosis, atrophy, lipidosis, hydropic and cloudy swelling, oval cell proliferation, cirrhosis, hemorrhage, macrophage aggregates, bile stagnation, dilation of sinusoid, intracellular edema, and dark granules. Ovary histology revealed some changes in higher concentrations such as increase in the number of pre-vitellogenic oocytes, oocyte atresia, and adhesion in the ovaries of females that were sampled from the sites with high concentration of mercury. In this study, existence of mercury in Mahshahr coast is demonstrated and high incidence of histological alterations in the liver and ovary of A. latus is an evidence of the poor environmental quality of creek waters. Hence, histopathological changes were induced by the mercury adversely affected the proper functioning of these organs in these fish.

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MeHg and total mercury concentrations were determined in the muscle tissues of four fish species (Cyprinus carpio, Rutilus frisii, Carassius auratus and Esox lucius) from Anzali wetland (Guilan, Iran). Fish with the highest amount of MeHg was selected to determine the thermodynamic parameters of MeHg extraction. The extractions process was performed in the range of temperatures 331.15 to 367.15 K and at atmospheric pressure. Results show the extraction of MeHg from SH groups of sulfhydryl proteins was an endothermic process with a positive value for entropy and Gibbs free energy changes at the room temperature. Significant difference was found between MeHg content at T=367.15 K and other temperatures. Correlation coefficients results showed that the mercury concentration in muscle tissue was significantly related to the length and weight of fish (p≤0.01). Also, thermodynamic parameters of methylmercury extractions had significant correlation (p≤0.05) with length and weight of the six fish specimen.

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The aim of this study was to measure the level of Arsenic, Cadmium, Nickel and Mercury in gill, muscle and hepatopancrease tissue of Aras dam Astacus leptoductylus and compare of them concentration in different body tissues. For this purpose, 271 samples of Astacus leptoductylus were randomly collected in Aras dam from December 1 to December 31, 2017 and transferred to the laboratory. After that tissue samples processed for injection in atomic absorption for apparatus for measuring the level of Arsenic, Cadmium, Nickel and Mercury. For measuring the protein, ash and moisture content of the samples AOAC method was conducted. The results showed that Arsenic, Cadmium, Nickel and Mercury were present in the Astacus leptoductylus samples and the highest level of these metals was in the muscle and the lowest in the gills. The highest level of metals existing in Astacus leptoductylus muscle was related to Cadmium (0.338± 79 0.79 ppb), and also Nickel (0.285±0.066 ppb) was in the second rank. The level of Arsenic and Mercury in muscle were ranked third and fourth. However, it was found that the total moisture content of the gills was higher than muscle and hepatopancrease tissue. On the other hand, the results of correlation between metals of different tissues of Astacus leptoductylus showed that the correlation between Cadmium and Nickel was higher than Arsenic and Nickel. The level of total protein and ash in Astacus leptoductylus muscles was higher than other tissues. The present study showed that analyzed Arsenic, Cadmium, Nickel and Mercury level were in the muscle, gill, and hepatopancrease tissue samples of the Aras dam A. leptoductylus in detectable concentrations, and Nickel and Mercury in the samples were lower than the WHO standard. As a result, the levels of metals in the Astacus leptoductylus samples collected from Aras dam were safe and reliable and therefore there is no problem.

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Mercury is one of the most harmful pollutants in the environment, which in the event of ingestion into the human body, it is not metabolized and severe nervous, respiratory and metabolic disorders will occur due to the formation of stable complexes with biological molecules. Therefore, the development of precise, fast and inexpensive methods for mercury detection in the environment is of great importance. Carbon quantum dot is a new fluorescent substance with unique physical and chemical properties which is taken into consideration for diagnostic applications, especially for heavy metals detection at low concentrations. In this study, carbon dots with blue fluorescent emission were synthesized using the pyrolysis method and characterized. Fluorescent emission intensity of synthesized carbon dots was decreased significantly in interacting with mercury. Then for providing an easy-to-use mercury detection method, carbon dot was encapsulated in sodium alginate hydrogel. Quenching fluorescent intensity of encapsulated carbon dots in the hydrogel structure was evaluated in the presence of mercury and 1micromolar detection limit was obtained. Encapsulating carbon dots in hydrogel structure not only extend the use of carbon dot as a mercury sensor but also can be used as an adsorbent for mercury pollutant from the environment.
 

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Due to widespread use of nanoparticles in various fields and the possibility of entering these nanoparticles into aquatic ecosystems, it is necessary to study the effects of these nanoparticles on surrounding environment. Artemia salina nauplii as a suitable biological model in ecotoxicology were exposed to different concentrations of 0.0001, 0.001, 0.005, 0.01 and 0.1 ppm mercury ions separately and simultaneously with a constant concentration of 0.1 ppm and 1 ppm titanium dioxide nanoparticles. The mortality rate of Artemia after 48 hours and the effects of these contaminants on fatty acid profile of Artemia were investigated. Artemia mortality in co-exposure treatment showed a dual effect. The mortality in the simultaneous exposure with constant concentration of 0.1ppm titanium dioxide increased compared with separate treatment of mercury. The mortality in simultaneous treatment with constant concentration of 1ppm titanium dioxide decreased compared with the separate treatment of mercury and the effect of mercury toxicity was reduced. Also, a decrease in saturated fatty acids was observed in the simultaneous exposure of mercury and titanium dioxide nanoparticles with a constant concentration of 1ppm compared with the separate treatment of mercury. The amount of monounsaturated and polyunsaturated fatty acids in the simultaneous exposure with constant concentration of 1ppm titanium dioxide was equal to control and increased compared with separate treatment of mercury. Present findings indicate the necessity of paying more attention to the potential interactions of pollutants in aquatic ecosystems and the effects of these interactions on the bioavailability and toxicity of pollutants regarding their concentration.

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This study was carried out in order to measuring Hg in some varieties of the most consumed imported and most locally cultured rice and comparing together and assess potential health risk. The correlation between Hg content of soil and rice samples, and effect of cooking and washing treatment on Hg concentration in rice, were investigated. In November 2008, locally most cultured rice and soil samples were collected from the Mazandaran province. High consumption of imported Indian rice with commercial brands collected from source, according to purposed method of standard office of Hormozgan. Advanced mercury analyzer Leco AMA 254 used to determination of Hg levels. The results showed that Hg concentration in Iranian rice (0.044 ± 0.003 µg g^-1 d.w) significantly over imported rice (0.039 ± 0.001 µg g^-1 d.w). Comparing the tolerable daily intakes (TDI) given by FAO/WHO with the mean estimated daily intakes (EDI) through rice consumption in this study was lower than TDI. In addition, results showed that no relationship was found between Hg concentration in rice and soil samples (r= 0.079, p=0.567), and cooking and washing treatment has not significant effect on mercury concentration. Finally, relationship between Hg concentration in soil and rice samples with soil parameters were studied that was not observed any correlation.

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Electrokinetic soil remediation is a promising technology that can be used for insitu treatment of fine-grained soils. In this study the numerical analyses of electro kinetic process in soil is considered. Numerical model is formulated for simulating mercury transport under an electric field using one-dimensional convection-diffusion equation that describes contaminant transport. The presented model is used for demonstrating the pH changes and mercury removal from kaolinite clay at last day. The finite difference method is used for solving the model. Computational programs were written in two ways of FTCS and Crank-Nicolson using MATLAB software. The Crank-Nicolson scheme has been more consistent with experimental results. Experimental results are used for the calibration of the model. The proposed numerical model shows good agreement with experimental results.

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Oil and gas processing activities is causes excess water consumption, which leads to excessive production of wastewater. This produced waste water contains mineral and biological compounds which can contaminate water and ground water. Vast amount of this industries’ produced wastewater in Oil-rich countries which mostly are arid countries, lead them to find more effective methods for water reuse as a new water resources. One of the most important water pollutant are heavy metals, so investigator are believe that heavy metals toxicity into environment is more than which disperse from radioactive toxicity to ground water and seas. Various physical, chemical and biological methods of waste water treatment are applied in refining and petrochemical industries. considerable amount af mercury with different operational units’ wastewater is discharge to environment from refinery units. Since mercury is not biodegradable and tend to accumulate in living organisms, we must be able to control it by using effective methods. Application of membrane filtration is new method for water and wastewater treatment industry. In this research, by application of case study on one of the nation’s gas refineries, reverse osmosis membrane system performance under different operating conditions, was studied. For this purpose effects of variable parameters, namely operating pressure (5, 7, 9 and 11 bar), pH (3, 6, 9, 11) and mercury concentration (1, 2, 4, 8 and 12 mg/l) on removal performance were studied. Considering removal performance of mercury, COD, TDS, EC, Turbidity and also membrane flow rate, optimum operating condition was obtained. Base on the results, reverse osmosis membrane performance is efficient in optimum parameters’ value, namely 7 bar pressure and pH=9 from permeate water quality and economical aspects. by increasing system pressure a significant decline in mercury and COD removal efficiency was observed. removal efficiency of mercury, COD, and TDS in 7 bar pressure condition was 91.35%, 99.55%, and 94.89% respectively and also permeat flowrate was acceptable, so 7 bar was found as optimum pressure. On the next stage af investigation, although by increasing wastewater sampel’s pH, a considerable increase in mercury and COD removal efficiency was observed, it cause a dramatic rise in TDS and turbidity in feed wastewater and also in permeate stream. More over high value of pH, namely pH=11 can make system prone to fouling. So pH=9 was choosen as a optimum pH. Finally reverse osmosis membrane performance in encountering with possible shocks and high concentration of influent mercury was investigated. Although results shows a significant decrease in membrane removal efficiency in encountering with high influent mercury concentration, reverse osmosis membrane system efficiency in mercury removal is acceptable in encountering conventional mercury concentration of refineries. reverse osmosis membrane performance is efficient in optimum parameters’ value namely 7 bar pressure and pH=9, so removal efficiency of mercury,COD, and TDS was 97.5%, 99.755 and 93.29% respectively.

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Mercury is a highly toxic and accumulative metal and its compounds, especially methyl mercury, are neurotoxins which cause blockage of the enzyme sites and interfere in protein synthesis. The fate of inorganic, mercury ions in nature is its turning into methyl mercury due to the aerobic action of microorganisms. Mercury is a toxic metal that causes the serious environmental problems. The main sources of mercury ions in aquatic ecosystems are divergent, chloralkali wastewater, oil refineries, power generation plants, paper and pulp manufacturing, rubber processing and fertilizers industries. Various methods have been used for removing heavy metals from aqueous environment such as reverse osmosis, chemical precipitation, ion exchange, coagulation and adsorption. Many carbon-based nanoparticles (CNTs) have been developed to remove heavy metals from aqueous media. They are promising material for numerous applications due to their unique electrical, mechanical, thermal, optical and chemical properties. In addition, CNTs are proven to be superior adsorbents for several divalent metal ions in water, because of their capability to establish (π–π) electrostatic interactions as well as for their large surface areas. Therefore, they have received considerable attention for usage in analytical chemistry and environmental remediation. Multi-walled carbon nanotubes (MWCNTs) were the first observed CNTs involving of up to several tens of graphite shells. The sorption capability of MWCNTs is related mainly to the functional groups attached on its surface. Generations of functional groups on the surface carbon nanotubes improves the reactivity and provides active sites for further chemical modifications. Many researchers have developed amino and thiol functionalization on carbon-based adsorbents and CNTs in order to increase the adsorption capacity, selectivity and removal efficiency of heavy metals and organic compounds. Among these functional groups, the thiols have an excellent binding ability to some metals such as silver, mercury, copper, nickel and zinc. In present study, multi-walled carbon nanotubes were functionalized in four stages to create thiolated multi-walled carbon nanotubes (MWCNTs-SH). The synthesized amino and thiolated MWCNTs were characterized by Fourier transform infrared spectroscopy (FT-IR) and elemental analysis (CHNS) to ensur successfully entailing the functional groups on MWCNTs surface. The efficiency of all synthesized MWCNTs in mercury removal was investigated. MWCNTs-SH was more efficient rather than other synthetized adsorbents in mercury removal from aqueous solutions. Increasing in adsorbent dosage concluded an enhanced mercury removal. Solution pH has a more effect on mercury removal. When the pH increased from 2 to 8 the removal percentage ranged from 9.8 to 92%. The data fitted by Langmuir isotherm model (R2=0.966) better than Freundlich model (R2=0.935). The obtained maximum adsorption capacity (qm) by Langmuir model was 206.64 mg/g while its experimental value was 160.90 mg/g and was higher than that reported in other literatures. Thus the prepared synthetized adsorbent has high efficiency for mercury removal from aqueous solutions.