Hexavalent Chromium Pollution Research Articles

Teaching the properties of chromium's oxidation states with a case study method

The purpose of this study was to investigate how a mixed-method case study affects pre-service science teachers' awareness of hexavalent chromium pollution and content knowledge about the properties of chromium's different oxidation states. The study was conducted in Turkey with 55 sophomores during the fall semester of 2013–2014. The students were taught using a case study about chromium's properties, the qualitative and quantitative analysis methods used with chromium compounds, the effects of chromium compounds on human health, and the chemical techniques that can be used to remove hexavalent chromium from wastewater. Open-ended questions were applied to determine the students' pre- and post-knowledge before and after instruction. An open-ended questionnaire and semi-structured interviews showed that the case study had a positive effect on all participants in terms of increasing their awareness of the hazardous effects of hexavalent chromium. Pair sample and independent samplet-test results revealed that the presenting and the audience groups significantly increased their content knowledge after instruction. On the other hand, while there was no statistically significant difference between the groups on verbal questions, there was a difference between the presenting and the audience groups on calculative questions. This finding shows that the mixed-method case instruction might not have affected all subjects in the same way.

Discrete Choice Experiment for Groundwater Valuation: Case of the Asopos River Basin, Greece

This paper contributes to the limited literature on the estimation of the total economic value of groundwater using a discrete choice experiment (DCE). An outline of theory and methodology is provided for the organization and application of experiments in the water sector, along with important references on optimizing outcomes and on utilizing previous valuation approaches into the design. The case study area was Viotia, Greece, and in particular the Asopos River basin aquifer, which has been in the center of international attention for the past 10 years, mainly owing to hexavalent chromium pollution. The research results give valuable insight to the respondents’ social profile and to issues valued most in cases of groundwater remediation, and perhaps more importantly to the willingness to pay for various remediation scenarios. In addition, the paper addresses other issues related to DCE, including econometric model appropriateness, selection, and comparisons; treatment of protest responses; and modeling of heterogeneity. The elicited values can be effectively used in policy making, natural resource damage assessment, and remediation planning.

東京都立公園のクロム鉱滓処理地におけるCr(VI)汚染

東京都立公園のクロム鉱滓処理地におけるCr(VI)汚染

Spatial distribution and the extent of heavy metal and hexavalent chromium pollution in agricultural soils from Jajmau, India

This study quantifies the extent of heavy metal pollution in the agricultural soils (57 samples) from Jajmau, Kanpur, India. Heavy metal concentrations (mg/kg) in agricultural soils, frequently irrigated with treated tannery effluent, are significantly higher: Cr 118–3142, Cr(VI): 2–87, Mn 341–821, Ni 24–47, Zn 78–427, V 73–110, Cd 2–13, Pb 15–69. Sludge embedded soil, mainly comprising of tannery sludge disposed in open ground, contains ~40,500 mg/kg Cr [and 1,400 mg/kg Cr(VI)], Zn (884), Cu (300), Cd (192), Pb (180) and Ni (68 mg/kg). Results show ~65 % of the total chromium is easily leachable from these soils under acidic conditions. Pollution assessment suggests that agricultural soils are highly polluted with Cr, Cu, Cd, Pb and Zn. Spatial distribution maps of heavy metals identifies specific areas that are heavily contaminated with Cr, Cu, Zn, Cd, Pb and Cr(VI), mostly along the length of the major canal constructed to distribute the treated tannery effluents. Principal component (PC) and cluster analysis suggest two principal components (or two clusters) that explain 83 % of data variability. PC1 positively correlates with Cr, Cu, Zn, Cr(VI), Pb, Cd and OM, which is attributed to anthropogenic activities, i.e. irrigation by treated tanneries effluent, open dumping of Cr sludge. PC2 strongly correlates with Fe, Ni, Co, V and Mn, which is attributed to weathering of parental materials. This study clearly reveals significant metal pollution including Cr(VI) pollution in Jajmau, which can lead to widespread soil and groundwater contamination.

Hexavalent chromium pollution caused by dumped chromium slag at the urban park in Tokyo

In January 2013, a high concentration of hexavalent chromium was detected in the meltwater at an urban park in Tokyo. A chromate manufacturing plant operated at this location until 1972. The highest concentration value showed was in excess of up to 740 times the Japanese regulation value (0.05 mg L−1). Although 40 years have passed since dumping, highly polluted groundwater is still found today. Heavy rain or snowfall is a trigger for the outbreak of Cr(VI) pollution in this area.

Rice Husk Silica Adsorbent for Removal of Hexavalent Chromium Pollution from Aquatic Solutions

The present study investigates the effectiveness of a new adsorbent prepared from agricultural wastes, namely rice husk silica as well as raw rice husk and rice bran to remove Cr from aquatic solutions. +6 The raw rice husk was collected from North of Iran. But rice husk silica was prepared by burning of clean rice husk inside a muffle furnace at a temperature of 800°C for 4 hours after acid leaching. The effects of four parameters: contact time (30 to 90 min), pH values (2 to 9), adsorbents dosages (0.5 to 1.5 g/L) and initial concentration (1.0 to 15 mg/L) were investigated to remove Cr . The silica derived from rice husk showed a +6 high percentage of SiO up to 94.24%. But Carbone was the highest element in raw rice husk up to 35.92%. 2 The maximum removal efficiency (RE) of Cr was obtained by rice bran up to 98.8% at 5.0 mg/L initial +6 concentration of Cr, 60 min of contact time, pH = 2 and adsorbents dosage of 1.0 g/L. However, at the same condition the maximum RE by raw rice husk and rice husk silica were 82.3 and 88.4%, respectively. Moreover, a negative strong significant correlation between increasing of initial concentration of Cr and RE was detected +6

The Study of Sensitivity Analysis of Parameters of Groundwater Numerical Simulation

This paper used both methods of single parameter and Multi-parameter combination sensitivity analysis in groundwater numerical model parameter sensitivity analysis. With the examples of Jiaozuo, Henan province, choosing coefficient of permeability, porosity and longitudinal dispersion degree as factor, the paper analysis the main controlling factors of contaminant migration of Hexavalent chromium in groundwater. Single parameter sensitivity analysis results show that the permeability coefficient gives largest impact to the migration of hexavalent chromium. It is positively correlates with groundwater numerical model. The rest of the parameters assume the inverse correlation. Multi-parameter combination sensitivity analysis results show that the permeability coefficient has absolute advantage among various parameter combinations. Another conclusion is that longitudinal dispersion degree affects smaller on the process of hexavalent chromium pollutants migration, but the impact on the final density is bigger.

Occupational health assessment of chromite toxicity among Indian miners.

Elevated concentration of hexavalent chromium pollution and contamination has contributed a major health hazard affecting more than 2 lakh mine workers and inhabitants residing in the Sukinda chromite mine of Odisha, India. Despite people suffering from several forms of ill health, physical and mental deformities, constant exposure to toxic wastes and chronic diseases as a result of chromite mining, there is a tragic gap in the availability of 'scientific’ studies and data on the health hazards of mining in India. Occupational Safety and Health Administration, Odisha State Pollution Control Board and the Odisha Voluntary Health Association data were used to compile the possible occupational health hazards, hexavalent chromium exposure and diseases among Sukinda chromite mines workers. Studies were reviewed to determine the routes of exposure and possible mechanism of chromium induced carcinogenicity among the workers. Our studies suggest all forms of hexavalent chromium are regarded as carcinogenic to workers however the most important routes of occupational exposure to Cr (VI) are inhalation and dermal contact. This review article outlines the physical, chemical, biological and psychosocial occupational health hazards of chromite mining and associated metallurgical processes to monitor the mining environment as well as the miners exposed to these toxicants to foster a safe work environment. The authors anticipate that the outcome of this manuscript will have an impact on Indian chromite mining industry that will subsequently bring about improvements in work conditions, develop intervention experiments in occupational health and safety programs.

Kinetics of Chromate Adsorption and Desorption at Fused Quartz/Water Interfaces Studied by Second Harmonic Generation

It is now recognized that an understanding of hexavalent chromium pollution in the environment is tied to an understanding of how hexavalent chromium binds to geosorbent surfaces. We have applied the nonlinear optical laser spectroscopy surface second harmonic generation (SHG) to study the adsorption and desorption kinetics of submonolayer amounts of chromate interacting with the fused quartz/water interface at pH 7 and at room temperature. The chromate concentrations are varied between 10-6 and 10-5 M. The adsorption and desorption behavior of chromate at the fused quartz/water interface can be described by a Langmuir adsorption and a first-order chromate desorption model with an adsorption rate constant of 3(1) × 103 s-1 M-1 and a desorption rate constant of 0.9(7) × 10-3 s-1. At 300 K and pH 7, the resulting equilibrium constant for chromate binding is in good agreement with equilibrium constants obtained from Langmuir isotherm measurements carried out between pH 4 and 9. Thus, thermodynamic and kineti...

Optimal operation of bioreactor system developed for the treatment of chromate wastewater using enterobacter cloacae HO-1

The characteristics of a novel bioreactor system developed for the simultaneous treatment of toxic hexavalent chromium (chromate) and high-strength organic pollution by introducing a chromate-resistant and chromate-reducing bacterium Enterobacter cloacae strain HO-1 (HO-1, hereafter) were studied to optimize its operating condition. Based upon the growth and chromate-reducing kinetics of HO-1, a mathematical model to simulate the change of chromate removal rate per unit volume of bioreactor and that per unit cell mass under the fed-batch operation was proposed. The effects of repeated cultivation of HO-1 with ORP-controlled aeration and the cumulative chromate reduction per unit cell mass on the microbial activity were investigated to represent the kinetic expression of chromate reduction. By using the mathematical model developed through the present research, the relationship between the operating conditions and the chromate reduction rate in the bioreactor was simulated and the model was verified by comparing it with the observed data. Thus the optimal operating conditions to give the higher reduction rate and the longer operating interval with and without aerated cultivation of HO-1 are extensively discussed. This bioreactor can be used for the treatment of chromate wastewater provided that some high concentration organic wastes are available. The rate of chromate reduction in the bioreactor is as high as 10 - 15 g-Cr6+/m3h. Chromium hydroxide, products of biological chromate reduction, can be recycled as a green pigment.