Investigating the carcinogenic and non-carcinogenic health hazards of heavy metal ions in Spinacia oleracea grown in agricultural soil treated with biochar and humic acid.

This study addressed the bioaccumulation and human health risk among the consumption of Spinacia oleracea grown in agricultural soil treated with humic acid (189-2310 ppm) and biochars (0.00-5.10%.wt). The biochars came from two local feedstocks of rice-husk (RH) and sugar-beet-pulp (SBP) pyrolyzed at temperatures 300 and 600 °C. Total concentrations of Cu, Cd, and Ni found in both the soil and biomass/biochar exceeded global safety thresholds. The bioaccumulation levels of HMs in spinach leaves varied, with Fe reaching the highest concentration at 765.27 mg kg-1 and Cd having the lowest concentration at 3.31 mg kg-1. Overall, the concentrations of Zn, Cd, Pb, and Ni in spinach leaves exceeded the safety threshold limits, so that its consumption is not recommended. The assessment of hazard quotient (HI) for the HMs indicated potential health hazards for humans (HI > 1) from consuming the edible parts of spinach. The biochar application rates of 4.35%wt and 0.00%.wt resulted in the highest (3.69) and lowest (3.15) HI values, respectively. The cumulative carcinogenic risk (TCR) ranged from 0.0085 to 0.0119, exceeding the cancer risk threshold. Introducing 5.10%wt biomass/biochar resulted in a 36% rise in TCR compared to the control. The utilization of humic acid alongside HMs-polluted biochars results in elevated levels of HMs bioaccumulation exceeding the allowable thresholds in crops (with a maximum increase of 49% at 2000 ppm humic acid in comparison to 189 ppm). Consequently, this raised the HI by 46% and the TCR by 22%. This study demonstrated that the utilization of HMs-polluted biochars could potentially pose supplementary health hazards. Moreover, it is evident that the utilization of HMs-polluted biochars in treating metal-contaminated soil does not effectively stabilize or reduce pollution.

Adsorption optimization and modeling of Hg2+ ions from aqueous solutions using response surface methodology by SNPs-CS bionanocomposite produced from rice husk agro-industrial waste as a novel environmentally-friendly bionanoadsorbent.

In the present research, extraction of silica (SiO2) from rice husk (RH) was optimized and silica nanoparticles (SNPs) was produced using it and functionalized by chitosan (CS) functional groups to obtain CS functionalized SNPs (SNPs-CS) bionanocomposite for the first time. The physical and chemical characteristics of the produced materials were examined using structural analyses. The results of structural analyses confirmed the fine structure of the produced materials. The SNPs-CS bionanocomposite was applied to effectively remove Hg2+ ions from aqueous solutions as an environmentally-friendly bionanoadsorbent and optimization and modeling of the adsorption conditions was explored using designed experiments by Design-Expert software with central composite design (CCD) and response surface methodology (RSM). Optimum adsorption conditions were obtained as solution pH of 6, SNPs-CS dosage of 0.1 g L-1 and Hg2+ ions concentration of 100 mg L-1 by removal efficiency of 85% and desirability function of 0.876. The results of adsorption kinetic showed a better fit of the pseudo-second-order model with experimental data, indicating the chemisorption of the adsorption process. The better fit of the Langmuir model with experimental data was confirmed by the results of adsorption isotherms, demonstrating monolayer adsorption on the homogeneous surface. The adsorption thermodynamic results illustrated the exothermicity and spontaneity of the adsorption reaction. The results of SNPs-CS recovery depicted its excellent recovery ability of removal efficiency with more than 90% after five consecutive adsorption and desorption cycles, which proved high potential of the produced bionanocomposite for industrial applications.

Binary toxicity of engineered silica nanoparticles (nSiO2) and arsenic (III) to zebrafish (Danio rerio): application of response surface methodology.

Increasing production and use of engineered nanoparticles (NPs) leads to their release into the aquatic environments where they can interact with other hazardous contaminants, such as heavy metals, and threaten aquatic organisms. This study considers the ecotoxicity of arsenic (III) and silica nanoparticles (nSiO2), individually and simultaneously, to the zebrafish (Danio rerio) using response surface methodology (RSM) under central composite design (CCD). The results revealed that in the treatments within the concentration range of 1 to 5 mg L-1 arsenic and 1-100 mg L-1 nSiO2, no mortality was observed after 96 h. The optimal conditions for achieving the lowest effect of simultaneous toxicity in the concentration range of nSiO2 and arsenic were 100 and 7 mg L-1, respectively. Accordingly, the desirable function of the predicted model was found to be 0.78. According to these results, arsenic is toxic for zebrafish. Importantly, exposure to nSiO2 alone did not cause acute toxicity in the studied species, while arsenic toxicity decreased by increasing the concentration of nSiO2.

Heavy metal concentrations in Caspian pond turtle (Mauremys caspica) in Zarivar International Wetland, Kurdistan Province of Iran.

In the present study, the cadmium, lead, and zinc levels in the blood and shell of Caspian pond turtles (Mauremys caspica) were investigated at five stations in Zarivar International Wetland in Kurdistan Province. All specimens were released at their capture locations within 2 h of capture. Water samples were collected at each station. Heavy metal concentrations were determined using an atomic absorption spectrometer. The mean cadmium, lead, and zinc concentrations were 0.04, 32.10, and 11.45 mg/l in blood samples; 1.82, 16.91, and 89.22 mg/l in shell samples; 0.005, 1.30, and 0.07 mg/l in water samples, respectively. In this study, the highest metal adsorption was zinc and was observed in shell. According to the results of this study, the shell of the Caspian Pond Turtle can be used to estimate the concentration of heavy metals. Our results suggest that Caspian pond turtle can be used as a biological indicator to estimate heavy metals.

In silico modeling of the antagonistic effect of mercuric chloride and silver nanoparticles on the mortality rate of zebrafish (Danio rerio) based on response surface methodology.

In this study, in silico modeling was designed to examine the antagonistic effect of mercuric chloride (HgCl2) and silver nanoparticles (AgNPs) on the mortality rate of zebrafish (Danio rerio) based on response surface methodology (RSM). Adult zebrafish (Danio rerio) with an average weight of 0.75 ± 0.16 g were used in this study. An interaction between HgCl2 and AgNPs was evaluated using DLS, TEM, and EDX mapping. In addition, RSM was applied to determine and predict the mortality rate of zebrafish induced by HgCl2 in the presence of non-lethal concentrations of AgNPs and to optimize dependent and independent variables. Following exposure to HgCl2, in vitro observations showed an increase in the hydrodynamic size of AgNPs and the formation of irregular nanoparticles. EDX mapping analysis also demonstrated the deposition of Hg ions on the surface of AgNPs, indicating the interaction between HgCl2 and AgNPs (i.e., the amalgamation of Hg and AgNPs). Moreover, in silico and in vivo findings illustrated that the mortality rate of zebrafish increased significantly in a concentration-dependent manner; however, the mortality rate reduced greatly in the presence of AgNPs during 96-h exposure. Statistically significant correlation and regression were also observed for the mortality rate between the actual and predicted values based on the ANOVA results, showing that the proposed model fits well. The most critical conditions of mortality rate were occurred by HgCl2 concentration of 0.23 mg L-1 and AgNP concentration of 0.04 mg L-1 that yielding maximum fish mortality rate of 96.541%. Additionally, the obtained value for model desirability was equal to 1.000 (i.e., the highest possible value). In conclusion, this statistical model could accurately describe the relationship between independent and dependent variables, and consequently boost substantially the experimental design of ecotoxicological studies by reducing the number of model organisms, toxic and chemical substances, time, and budget.

Effects of lead ions on germination, initial growth, and physiological characteristics of Lolium perenne L. species and its bioaccumulation potential.

The present study was conducted to investigate the responses of Lolium perenne L. species to lead ions. To do this, the effects of lead ions at five levels: control (blank), 250, 500, 750, and 1000 mg/kg or mg/L (depending on germination in the soil or petri dish) on the germination, initial growth, and physiological characteristics of Lolium perenne were investigated. The results showed that the difference between various lead concentrations was statistically significant at 1% confidence level in all of the germination, vegetative, and physiological characteristics. In addition, the results of translocation and stress factors indicated that there was a significant difference between the control treatment and the concentrations of 250, 500, 750, and 1000 mg/L of lead ions. Results show that the mean value of stress, which was 0.3196 in the control value, reached 0.4154 at the concentrations 1000 mg/L. Different levels of lead ions had significant effect on the estimated characteristics including germination percentage, seed vigor, germination index, chlorophyll a, chlorophyll b, carotenoids, root, and shoot. The average germination percentage in the control was 46.66%, which decreased by 5% at the highest lead concentration. In addition, the average of seed vigor, which was 34.06 in the control conditions, decreased to 0.72 at the highest lead concentration. Also, the chlorophyll a dropped from 0.5261 mg/g in the control conditions to 0.3149 mg/g. On the other hand, increase in lead ion concentration affected the physiological characteristics of Lolium perenne species. Results suggest that Lolium perenne is capable of accumulating lead and is well tolerant to lead in soil. Therefore, it is concluded that it can be used for sowing on lands which are polluted to this heavy metal (up to the concentration of 1000 mg/kg).

Colorimetric and naked eye detection of trace Hg2+ ions in the environmental water samples based on plasmonic response of sodium alginate impregnated by silver nanoparticles.

Water pollution with mercury is a global concern. Therefore, establishing a rapid and accurate detection method is urgently required. Nanosensors can be a perfect alternative to instrument detection. In order to overcome low sustainability of sensors, a new composite nanosensor of sodium alginate- silver nanoparticles (SA-AgNPs) was synthesized by solvent casting method and used in colorimetric and naked eye detection of trace Hg2+ ions in water samples. The structural features of the produced nanosensor were characterized by instrumental techniques. The obtained results confirmed the formation of AgNPs with an average size of 13.34 nm. The colorimetric sensing of Hg2+ was carried out under specific conditions (pH = 6 and reaction time of 7 min) with a linear correlation obtained between the absorbance at 402 nm and different Hg2+ ion concentrations within the range of 0.025 µM-60 µM. The synthesized composite nanosensor of SA-AgNPs detected Hg2+ ions with a detection limit (LOD) of 5.29 nM. In addition, this sensor was successfully applied to detect Hg2+ ions in the environmental water samples with recoveries within the range of 81.58% to 114.73%. The produced nanosensor exhibited good selectivity toward Hg2+ ions in the presence of several competing ions.

Toxicity assessment of arsenic on common carp (Cyprinus carpio) and development of natural sorbents to reduce the bioconcentration by RSM methodology.

The objective of the present study was firstly acute toxicity bioassay of arsenic on common carp (Cyprinus carpio) and then the development of natural sorbent beds (clinoptilolite and pumice) to reduce bioconcentration of arsenic in muscle tissue were considered in comparative evaluation. In this regard, the acute toxicity of arsenic on juvenile fish was assessed according to the OECD guideline (No. 203). Moreover, the efficacy of clinoptilolite and pumice as natural sorbents was assessed to reduce bioconcentration of arsenic in the fish muscle tissue during a 21 day by response surface methodology (RSM) under central composite design (CCD). The most important point of this study was to evaluate the interactions between independent variables (clinoptilolite and pumice as sorbents and arsenic as pollutant) and arsenic bioconcentration in fish muscle tissue as a dependent variable (response). In these regards, a total of 24 sets of experiments (12 sets for clinoptilolite and pumice separately) were designed by the software to achieve the best adsorption conditions. According to the arsenic toxicity test, results as estimated by Probit method, the 96 h LC50 was 9.48 ±â€¯1.01 mg/L. Analysis of variance (ANOVA) which was applied to modeling and optimization of response revealed that the predicted values were in relatively good agreement with the experimental data. Additionally, the obtained value for model desirability by clinoptilolite and pumice were 0.932 and 0.958, respectively. Overall, the obtained results indicate that both adsorbents reduced the bioconcentration of As (V) in the muscle tissue of common carp, but clinoptilolite was more effective.

Application of response surface methodology for optimization of lead biosorption in an aqueous solution by Aspergillus niger.

Response surface methodology was applied to optimize the removal of lead ion by Aspergillus niger in an aqueous solution. Experiments were conducted based on a rotatable central composite design (CCD) and analyzed using response surface methodology (RSM). The biosorption process was investigated as a function of three independent factors viz. initial solution pH (2.8-7.2), initial lead concentration (8-30 mg/l) and biomass dosage (1.6-6 g/l). The optimum conditions for the lead biosorption were found to be 3.44, 19.28 mg/l and 3.74 g/l, respectively, for initial solution pH, initial lead ion concentration and biomass dosage. Lead biosorption capacity on dead A. niger fungal biomass was enhanced by pretreatment using NaOH. Under these conditions, maximum biosorption capacity of the biomass for removal of lead ions was obtained to 96.21%. The desirability function was used to evaluate all the factors and response in the biosorption experiments in order to find an optimum point where the desired conditions could be obtained. The A. niger particles with clean surface and high porosity may have application as biosorbent for heavy metal removal from wastewater effluents.

Synthesis of magMCM-41 with rice husk silica as cadmium sorbent from aqueous solutions: parameters' optimization by response surface methodology.

The magnetic mesoporous silica of magMCM-41 with large surface area (695 m2 g-1) and high magnetization (10.79 emu g-1) was synthesized using extracted amorphous silica from rice husk. The synthesized materials were applied for adsorption of Cd(II) ions from aqueous solution in batch operation systems. A highly selective adsorbent was obtained by grafting 3-aminopropyltrimethoxysilane on the pores of the magMCM-41 in which the adsorption capacity of Cd(II) ions increased from 41.8 to 86 mg g-1, under the same conditions. A total of 20 sets of experiments were planned by the central composite design under response surface methodology. The effects of three independent variables pH, initial Cd(II) ion concentration and sorbent dosage were investigated on the adsorption capacity (qe) and removal efficiency (R) of cadmium. The best responses for Cd(II) adsorption capacity and removal efficiency were 493.21 mg g-1 and 60.25%, respectively, which was achieved at pH of 5.05, sorbent dosage of 0.1 g L-1 and Cd(II) concentration of 150 mg L-1. Additionally, the obtained value for desirability was equal to 0.807. The theoretical isotherm models were applied to describe the adsorption process that the Langmuir model provides the best correlation of the equilibrium data. The kinetics study revealed that data from the experiments fitted well to the pseudo-second-order equation than the pseudo-first-order equation. The thermodynamic parameters revealed that the adsorption process strongly depended on temperature and indicated the exothermic behavior and spontaneous nature of the adsorption.

Intra-canal calcium hydroxide removal by two rotary systems: A comparative study.

AIM: The presence of calcium hydroxide (Ca(OH)2) in the root canal interferes with the apical root canal sealing and may result in periapical lesions in the long run. The present study was aimed to compare the efficacy of two rotary systems of Race and Mtwo in the removal of Ca (OH)2 aqueous-based from distobuccal canals of human maxillary molars. MATERIALS AND METHODS: A total of 44 distobuccal root canals of human maxillary molars were randomly distributed into two groups of 20 canals each and two control groups. Specimens in each group were instrumented with similar master apical rotary (MAR) and flexible files according to the manufacture's guidelines. The Ca (OH)2 paste was placed in canals using # 20 lentulo and radiographs were taken from the two dimensions. The roots were incubated for 1 week at 37°C and 100% humidity and Ca (OH)2 was removed from canals by MAR, afterward. Then, the roots were longitudinally split in halves by diamond disk and chisel without entering the root canals. Photos were taken from the canals' walls by a stereomicroscope with × 10 magnification. Next, according to a defined scoring system, photos were scored by four endodontists, so that scores 1 and 2 (nonvisible remnants or scattered remnants of Ca(OH)2) were considered as acceptable and scores 3 and 4 (distinct mass or densely-packed mass of Ca(OH)2) were regarded as nonacceptable. RESULTS: The obtained findings indicated that in coronal, middle, and apical portions of the root canal, 45, 60, and 65% of Mtwo specimens and 40, 50, and 55% of specimens prepared by the Race system acquired an acceptable score (1 and 2), respectively. Moreover, the results showed no significant difference between the two groups (P > 0.05). CONCLUSIONS: Both Mtwo and Race rotary systems with acceptable removal efficiency (score 1 and 2) were similarly able to remove Ca(OH)2.

Investigation of qualitative and quantitative of volatile organic compounds of ambient air in the Mahshahr Petrochemical Complex in 2009.

BACKGROUND: Volatile organic compounds (VOCs) are human-made chemicals widely spread in the environment and produced by petrochemical industries and petroleum refineries. The aim of this research was to evaluate the distribution of VOCs in the ambient air of Mahshahr Petrochemical Complex, Iran. METHODS: This study was a cross-sectional research performed in 2009. We used the method numbered 1501, 1500, 2000, 1003, 1005, 1010, 2555, 1300 and 1400 of the National Institute of Occupational Safety and Health (NIOSH) for the sampling and analysis of compounds in the air. A total of 204 samples were analyzed using Gas Chromatography-Mass Spectrometry (GC-MS) and a Gas Chromatography-Flame Ionization Detector (GC-FID). RESULTS: The mean of concentrations of the pollutants in the winter is less than in summer and a strong variation occurred among the sampling site, attributed to the change in meteorology. The results indicated high concentrations of benzene in most factories. In addition, a significant difference occurred between the concentrations of the compounds in the ambient air inside and outside the factories in both seasons (P<0.050). CONCLUSION: It seems that the atmospheric conditions of the workplace affect the spreading of the pollutants, causing the concentration of the pollutants in the summer to be higher than in the winter. In addition, the frequent prevailing wind speed in the region plays a major role in the distribution of the pollutants from Mahshahr Petrochemical factories.

Application of traditional cyclone with spray scrubber to remove airborne silica particles emitted from stone-crushing factories.

The traditional cyclone with spray scrubber was developed for the removal of airborne silica particles from local exhaust ventilation (LEV). The objective of this research is to evaluate the efficiency of this process for removing silica particles in LEV. After designing and installing a traditional cyclone and spray scrubber, air samples were obtained at the inlet and outlet of the apparatus. The mass of each collected sample was determined gravimetrically using EPA method. The efficiency of the cyclone with spray scrubber for the removal of dust particles from the LEV system was determined to be in the range of 92-99%. There was a high correlation between the inlet concentration of dust particles and the efficiency of the apparatus. The total pressure across the system was 772.17-1120.90 Pa. It was concluded that a traditional cyclone with a spray scrubber can effectively remove a very high percentage of the incoming silica particles from an LEV. The total pressure drop across the current process is less than the pressure drop across other treatment equipment, which means that our process can effectively remove silica particles while using less electricity than other processes.