• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.25 no.1
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• pp.89-94
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• 2015

Objectives: The objective of this study was to determine characteristics of workers' exposures to airborne total and hexavalent chromium by job title in electroplating processes. Methods: Total Cr was determined through a modified method based on NIOSH Method 7024. Airborne hexavalent Cr, Cr(VI), was sampled and extracted according to NIOSH Method 7600 and analyzed at 520 nm using an ion chromatograph/visible detector. Results: The geometric mean(GM) of total Cr concentrations from all factories was $11.2{\mu}g/m^3$(GSD=4.9). The GM of Cr(VI) concentrations from all factories was $2.84{\mu}g/m$ (GSD=5.2), and the concentrations among factories were significantly different (p<0.05). The Cr(VI) levels were lower than total Cr levels. Total Cr exposure levels were highest among buffing workers ($21.6{\mu}g/m^3$), but Cr(VI) levels were highest among plating workers($4.15{\mu}g/m^3$). The concentrations of Cr(VI) and total Cr from plating tasks was highly correlated(r=0.91). Conclusions: In the electroplating industry, plating workers were mainly exposed to Cr(VI), but others were not. Oxidation-reduction states of Cr and job titles should be considered in the exposure or risk assessments of chrome electroplating factories.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.8 no.2
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• pp.209-223
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• 1998

The aim of this study was to evaluate welders' exposure to hexavalent chromium (Cr(VI)) and nickel (Ni) during welding operations in a Korean shipyard. The airborne Cr(VI) and Ni concentrations were measured during metal inert gas (MIG) welding on mild and stainless steel, and manual metal arc (MMA) welding on mild steel. The geometric mean (GM) of Cr(VI) concentrations inside the welding helmet during MIG welding on mild steel were $0.0018mg/m^3$ inside a ship section, and $0.0015-0.0026mg/m^3$ at the welding shops. All of the personal breathing zone air samples were below the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value ($TLV^{(R)}$) of $0.01mg/m^3$. Conversely, eighty-eight percent(21 of 24) of the personal breathing zone air samples exceeded the National Institute for Occupational Safety and Health (NIOSH) recommended exposure limit of $0.001mg/m^3$. Ni was not detected on 20 of 23 air samples collected during MIG welding on mild steel. The three Ni samples above the limit of detection ranged from 0.015 to $0.044mg/m^3$. The GM of Cr(VI) concentrations during MMA welding on mild steel were $0.0013mg/m^3$, but Ni was not detected in the air samples during this operation. It is assumed that the airborne Cr(VI) and Ni during mild steel welding were derived from the base metals which contained about 0.03% Cr and 0.03% Ni. The GM of airborne total Cr, Cr(VI) and Ni concentrations during MIG welding on stainless steel were 4.02, 0.13 and $0.86mg/m^3$, respectively, and the levels of Cr(VI) and Ni were above the ACGIH-$TLV^{(R)}$. Cr(VI) comprised about 35.5% of the total chromium(Cr) from MIG welding on mild steel, and about 8.4% of total Cr from MIG welding on stainless steel. The ratios of Cr(VI) to total Cr were significantly different among welding shops. It was concluded that welders were exposed to high levels of Cr(VI) and Ni during welding on stainless steel, and were exposed to low levels of Cr(VI) even during welding on mild steel.

• Bulletin of the Korean Chemical Society
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• v.30 no.6
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• pp.1252-1256
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• 2009

A simple, selective and sensitive fluorescence quenching method was developed to the determination Cr(VI). The method is based on the oxidation of $I^-\;to\;{{I_3}^-}$ by Cr(VI) in sulfuric acid solution followed by immediate formation of ion association compound between I3 − and rhodamine 6G in Tween-80 micellar media at room temperature. The influence of several surfactants on rhodamine 6G fluorescence signal was studied; particular attention was paid in the aggregation behavior of rhodamine 6G–Tween-80 system. The experimental parameters (e.g., type of surfactant, reagent concentration) were studied and the optimal conditions were established. The linear calibration graph was obtained in the range 2.0 - 100.0 ng m$L^{-1}$ Cr(VI). The detection limit of the method was 0.37 ng m$L^{-1}$. The relative standard deviation (R.S.D.) is less than 5% (n = 5). The efficiency of the method for the determination of Cr(VI) in the presence of Cr(III) in the sample was investigated. The method was applied successfully to the determination of Cr(VI) and total Cr in water, and liver tissue samples.

• Korean Journal of Microbiology
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• v.33 no.2
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• pp.125-130
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• 1997

Microbial reduction of hexava1ent(VI) to trivalent(lII) chromium is regarded as one of the mechanisms that confers resistance to bacteria. In order to verify this hypothesis, we compared Cr(VI) resistance with Cr(VI) reduction among 20 phenotypically distinct environmental isolates from Cr-contaminated and uncontaminated soils. With glucose as an electron donor, Cr(VI) reduction by washed cell suspensions ranged from 0.014 to 0.305 mM Cr(VI) reduced $h^1$. Cr(VI) resistance of the isolates were measured by growth inhibitions on a liquid medium containing 2 mM Cr(VI) based on their decrease of $A_{630}1$ as compared to the controls without Cr(VI). The isolates had a broad range of resistance from no inhibition to 93.4% inhibition of their growth. Upon correlation analysis, there was no significant relationship between those two phenomena. At a population level, a comparison of % resistant viable counts among the Cr-contaminated and uncontaminated soils showed 19.1 % and 0.4% of their total viable counts, respectively. The difference of % resistance between two site,. strongly suggested that the Cr(VI) present in the soils influences natural selection for resistant phenotypes. However, it is unlikely that the Cr(VI) resistance is dependent solely on the reduction as judged by the correlation analysis.

• Korean Journal of Soil Science and Fertilizer
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• v.44 no.5
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• pp.727-733
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• 2011

A new Korean standard for the determination of Cr(VI) in soils has been officially published as ES 07408.1 in 2009. This analytical method is based on the hot alkaline digestion and colorimetric detection prescribed by U.S. EPA method 3060A and 7196A. The hot alkaline digestion accomplished using 0.28 M $Na_2CO_3$ and 0.5 M NaOH solution (pH 13.4) at $90{\sim}95^{\circ}C$ determines total Cr(VI) in soils extracting all forms of Cr(VI), including water-soluble, adsorbed, precipitated, and mineral-bound chromates. This aggressive alkaline digestion, however, proved to be problematic for certain soils which contain large amounts of soluble humic substances or active manganese oxides. Cr(III) could be oxidized to Cr(VI) by manganese oxides during the strong alkaline extraction, resulting in overestimation (positive error) of Cr(VI). In contrast, Cr(VI) reduction by dissolved humic matter or Fe(II) could occur during the neutralization and acidic colorimetric detection procedure, resulting in underestimation (negative error) of Cr(VI). Futhermore, dissolved humic matter hampered the colorimetric detection of Cr(VI) using UV/Vis spectrophotometer due to the strong coloration of the filtrate, resulting in overestimation (positive error) of Cr(VI). Without understanding the mechanisms of Cr(VI) and Cr(III) transformation during the analysis it could be difficult to operate the experiment in laboratory and to evaluate the Cr(VI) results. For this reason, in this paper we described the theoretical principles and limitations of Cr(VI) analysis and provided useful guidelines for laboratory work and Cr(VI) data analysis.

• Journal of Environmental Health Sciences
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• v.28 no.1
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• pp.41-49
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• 2002

Recently, pilot studies showed an evidence of reduction of airborne hexavalent chromium, Cr(VI), on PVC filter during air sampling and storage. However, the information on this in the field was limited. Thus, we studied the reduction behaviors of airborne Cr(VI) on PVC filters during sampling and storage at three field electroplating operations. Regression between sampling time and the reduction (ratio of Cr(VI) to total Cr concentrations) was not statistically significant (p>0.05). However, the reductions in samples collected for 240 ～ 340 minutes were significantly higher than those for 30 - 60 minutes. On the other hand, another experiment showed a good correlation (r=0.96) between sampling time and the reduction without an exceptional value. Storage temperature was not a factor affecting the reduction of Cr(VI) collected on PVC filter. The loss of Cr(VI) samples stored in alkali solution (2% NaOH/3% Na$_2$CO$_3$) was significantly lower than that stored in vial according to NIOSH method (p<0.05). Thus, dipping Cr(VI) samples into alkali solution was a storage method to minimize tile reduction.

• Korean Chemical Engineering Research
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• v.44 no.6
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• pp.644-649
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• 2006

In this paper, the Cr(VI) adsorption behaviors of activated carbons (ACs) treated by various ozone treatment conditions were studied. The surface properties of the ACs studied were determined by pH, acid-base, and FT-IR measurements. $N_2$ adsorption isotherm characteristics at 77K were confirmed by BET equation, Boer's t-plot method, and Horvath-Kawazoe's slit pore model. Also, the total Cr adsorption amount onto the ACs was measured by ICP-AES. As a result, the ozone treatment led to an increase of oxygen-containing polar functional groups and total acidity as well. Meanwhile, the specific surface areas or micropore volumes were slightly decreased after the ozone treatment due to the micropore filling or blocking. Nevertheless, the total Cr adsorption of ACs was increased with increasing of the ozone treatment time, attributed to the good interaction between Cr ions and polar functional groups on the ACs.

• Asian Journal of Atmospheric Environment
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• v.10 no.4
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• pp.208-216
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• 2016

This paper reports the results of a field evaluation which used sampling and analytical methods to determine the levels of airborne hexavalent chromium Cr(VI) in major industrial complexes in Korea over a seven year period (2007-2013). Cr(VI) concentrations were determined using cellulose filter sampling and ion chromatography analysis. In order to validate the analytical performance of these methods, studies were also carried out to investigate data quality control (QC) parameters, such as the method detection limit (MDL), repeatability, and recovery efficiencies. The average concentrations of Cr(VI) for the nine industrial complexes in Korea were in the range of 0.09 to $1.40ng/m^3$, which is similar to of the concentrations in other industrial areas around the world. The impacts of Cr(VI) emissions from industrial areas on Cr(VI) concentrations in neighboring-residential areas were considerably low, and the dispersion of Cr(VI) from industrial areas to residential areas was estimated to be 'not-significant'. Cr(VI) levels were not affected by seasonal variation, which suggests that chromium was emitted continuously from the industrial sources throughout the year. The concentration of Cr(VI) measured accounted for 0.7 to 9.4 percent of the total chromium level, which is a low percentage compared to those in other urban areas around the world. This is the first report in an international journal of a field study conducted in Korea to determine the concentration of Cr(VI) in the ambient air of industrial and residential areas.

• Carbon letters
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• v.9 no.1
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• pp.23-27
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• 2008

The adsorption and reduction of Cr (VI) to Cr (III) by surface modified activated carbon (AC) in an aqueous solution was studied. The effects of surface modifications on the properties of the carbons were investigated by the analysis of specific surface area, carbon surface pH, acid/base surface values and functional groups. In order to understand the Cr(VI) adsorption and reduction ratio from Cr(VI) to Cr(III), the Cr adsorption capacity of AC was also measured and discussed by using inductively coupled plasma and UV spectrophotometer. The modifications bring about substantial variation in the chemical properties whereas the physical properties such as specific surface area, pore volume and pore size distribution nearly were not changed. Total Cr adsorption efficiency of as-received activated carbon (R-AC) and nitric acid treated activated carbon (N1-AC and N2-AC) were recorded on 98.2, 99.7 and 100%. Cr(III) reduction efficiency of R-AC increased largely from 0.4% to 28.3% compared to N1-AC and N2-AC.

• Advances in environmental research
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• v.6 no.2
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• pp.95-111
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• 2017

The valorization of swine manure samples, i.e., de-watered cake (SMc) and solid digestate (SMd), in products with beneficial value, i.e., low cost activated carbons (ACs), is studied. For this purpose slow pyrolysis and steam activation at three different duration times are applied. Additionally, the obtained ACs are characterized and tested towards removal of Cr(VI) from aqueous solutions. It is revealed that BET surface area varies in the range of $236-267m^2/g$ for ACs prepared from SMc sample and in the range of $411-432m^2/g$ for ACs prepared from SMd sample. Despite the low determined surface area of prepared ACs, a high total Cr removal capacity is observed occurring through a "coupled adsorption-reduction" mechanism. Higher Cr(VI) removal capacity is demonstrated for ACs having higher surface area ($q_m$ is 140.9 mg/g according Langmuir modelling). Cr(VI) removal is found to be pH dependent with a maximum at pH 1. However at that pH significant amounts of Cr remain in the solution as Cr(III). At pH 2 lower amount of Cr(VI) is removed compensated by a higher removal of Cr(III) resulting in a higher amount of adsorbed $Cr_{tot}$. Therefore adsorption at pH 2 is found to be appropriate. The removal capacity of the studied ACs towards Cr(VI) is almost independent of activation time.