• Economic and Environmental Geology
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• v.36 no.5
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• pp.349-356
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• 2003

As industrial activities are growing, pollutants found in the contaminated land are getting diverse. Some contaminated areas are subject to mixed wastes containing both organic and inorganic wastes such as hydrocarbon and heavy metals. This study concerns with the influence of the degradation of organic pollutants on the coexisting heavy metals, expecially for As. As mainly exists as two different oxidation state; As(III) and As(V) and the conversion between the two chemical forms may be induced by organic degradation in the soil contaminated by mixed wastes. We operated microcosm in an anaerobic chamber for 60 days, using sandy loam. The soils in the microcosm are artificially contaminated both by tetradecane and As, with different combination of As(III) and As(V); As(III):As(V) 1:1, As(III) only and As(V) only. Although not systematic, ratio of As(III)/As(Total) increase slightly at the later stage of experiment. Considering complicated geochemical reactions involving oxidation/reduction of organic materials, Mn/Fe oxides and As, the findings in the study seem to indicate the degradation of the organics is connected with the As speciation. That is to say, the As(V) can be reduced to As(III) either by direct or indirect influence induced by the organic degradation. Although Fe and Mn are good oxidising agent for the oxidation of As(III) to As(V), organic degradation may have suppressed reductive dissolution of the Fe and Mn oxides, causing the organic pollutants to retard the oxidation of As(III) to As(V) until the organic degradation ceases. The possible influence of organic degradation on the As speciation implies that the As in mixed wastes may be have elevated toxicity and mobility by partial conversion from As(V) to As(III).

• Economic and Environmental Geology
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• v.38 no.5 s.174
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• pp.525-534
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• 2005

Adsorption experiments for As(V) and As(III) onto the surfaces of aerobic Pseudomonas aeruginosa, which can be readily isolated from natural media, were conducted under nutrient-absent conditions. While a small amount of As(III) was adsorbed on the bacterial cell surfaces, As(V) was not effectively removed from the solution through adsorption. The result was likely due to the electrostatic repulsion between anionic compounds of aqueous As(V) and cell surfaces of f aeruginosa. However, the bacteria forming biofilm reduced a large amount of aqueous As(V) to As(III), which indicated that microorganisms in most oligotrophic, natural geologic settings can mediate the behavior of aqueous As. Biobarriers designed to remove the various heavy metals in contaminant plume may practically lead to the enhancement of toxicity and mobility of As.

• Economic and Environmental Geology
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• v.38 no.5 s.174
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• pp.571-577
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• 2005

Permeable reactive barrier using iron oxide coated sand is one of effective technologies for As(V) contaminated groundwater. However, this method is restricted to As(III), because As(III) species tends to be more weakly bound to adsorbent. In order to overcome the limitation of iron oxide coated sand application to As(III) contaminated groundwater, manganese oxide materials as promoter of As(III) removal were combined to the conventional technology in this study. For combined use of iron oxide coated sand and manganese oxide coated sand, two kinds of removal methods, sequential removal method and simultaneous removal method, were introduced. Both methods showed similar removal efficiency over $85\%$ for 6 hrs. However, the sequential method converted the As contaminated water to acid state (pH 4.5), on the contrary, the simultaneous method maintained neutral state (pH 6.0). Therefore, simultaneous As removal method was ascertained as a suitable treatment technology of As contaminated water. Moreover, for more effective As(III) remediation technique, polypropylene textile which has the characteristics of high surface area, low specific gravity and flexibility was applied as alternative material of sand. The combined use of coated polypropylenes by simultaneous method showed much more prominent and rapid remediation efficiency over $99\%$ after 6 hrs; besides, it has practical advantages in replacement or disposal of adsorbent for simple conventional removal device.

• Journal of the Mineralogical Society of Korea
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• v.21 no.4
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• pp.425-434
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• 2008

Arsenic contamination in soil and groundwater has recently been one of the most serious environmental concerns. This arsenic contamination can be originated from natural or anthropogenic sources. It has been well known that arsenic behavior in geo-environmental is controlled by various oxides or hydroxides, such as those of iron, manganese, and aluminum, and clay minerals. Among those, particularly, iron (oxy)hydroxides are the most effective scavengers for arsenic. For this reason, this study characterized arsenic adsorption of magnetite which is a kind of iron oxide in nature. The physicochemcial features of the magnetite were investigated to evaluate adsorption of arsenite [As(III)] and arsenate [As(V)] onto magnetite. In addition to experiments on adsorption equilibria, kinetic experiments were also conducted. The point of zero charge (PZC) and specific surface area of the laboratory-synthesized magnetite used as an arsenic adsorbent were measured 6.56 and $16.6\;g/m^2$, which values seem to be relatively smaller than those of the other iron (oxy)hydroxides. From the results of equilibria experiments, arsenite was much more adsorbed onto magnetite than arsenate, indicating the affinity of arsenite on magnetite is larger than arsenate. Arsenite and arsenate showed adsorption maxima at pHs 7 and 2, respectively. In particular, adsorption of arsenate decreased with increase in pH as a result of electrical repulsion caused by anionic arsenate and negatively-charged surface of magnetite. These results indicate that the surface charge of magnetite and the chemical speciation of arsenic should be considered as the most crucial factors in controlling arsenic. The results of kinetic experiments show that arsenate was adsorbed more quickly than arsenite and adsorption of arsenic was investigated to be mostly completed within the duration of 4 hours, regardless of chemical speciation of arsenic. When the results of kinetic experiments were fitted to a variety of kinetic models proposed so far, power function and elovich model were evaluated to be the most suitable ones which can simulate adsorption kinetics of two kinds of arsenic species onto magnetite.

• Analytical Science and Technology
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• v.16 no.2
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• pp.134-142
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• 2003

Comparison of a microwave-assisted extraction with sonication extraction was performed for arsenic speciation in fish tissue with chromatographic separation and inductively coupled plasma mass spectrometry detection. The detection limits of arsenicals with ultrasonic nebulizerand cross-flow nebulizer were shown to be similar. The arsenicals investigated were arsenobetaine (AsB), arsenite [As(III)], dimethylarsine acid (DMA), monomethylarsonic acid (MMA), arsenate [As(v)], and phenylarsonic acid (PAA). Quantitative extraction of arsenicals from dogfish muscle, DORM-2, standard reference material of NRCC (National Research Council of Canada) was achieved using 50% (v/v) methanol-water in both extraction methods. Extraction efficiency of arsenobetaine in both methods is greater than 82% with RSDs on replicates of less than 5%. The concentrations of AsB determined in extract of microwave assisted extraction and sonication methods were $14.18{\pm}0.42mg\;kg^{-1}$ and $13.54 {\pm}0.84mg\;kg^{-1}$, respectively. And the concentrations of DMA were $0.45{\pm}0.06mg\;kg^{-1}$ and $0.44{\pm}0.06mg\;kg^{-1}$, respectively.

• Journal of Microbiology and Biotechnology
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• v.21 no.12
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• pp.1306-1311
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• 2011

Recombinant Rhodopseudomonas palustris, harboring the carotenoid-metabolizing gene crtI (CrtIBS), and whose color changes from greenish yellow to red in response to inorganic As(III), was cultured in transparent microplate wells illuminated with a light emitting diode (LED) array. The cells were seen to grow better under near-infrared light, when compared with cells illuminated with blue or green LEDs. The absorbance ratio of 525 to 425 nm after cultivation for 24 h, which reflects red carotenoid accumulation, increased with an increase in As(III) concentrations. The detection limit of cultures illuminated with near-infrared LED was 5 ${\mu}g$/l, which was equivalent to that of cultures in test tubes illuminated with an incandescent lamp. A near-infrared LED array, in combination with a microplate, enabled the simultaneous handling of multiple cultures, including CrtIBS and a control strain, for normalization by the illumination of those with equal photon flux densities. Thus, the introduction of a near-infrared LED array to the assay is advantageous for the monitoring of arsenic in natural water samples that may contain a number of unknown factors and, therefore, need normalization of the reporter event.

• Journal of the Mineralogical Society of Korea
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• v.25 no.4
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• pp.197-210
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• 2012

Hematite has been known to be the most stable form of various iron (oxyhydr)oxides in the surface environments. In this study, its properties as an adsorbent were examined and also adsorption of arsenic onto hematite was characterized as well. The specific surface area of hematite synthesized in our laboratory appeared to be $31.8g\;m^2/g$ and its point of zero salt effect, (PZSE) determined by potentiometric titration was observed 8.5. These features of hematite may contribute to high capacity of arsenic adsorption. From several adsorption experiments undertaken at the identical solution concentrations over pH 2~12, the adsorption of As(III) (arsenite) was greater than that of As(V) (arsenate). As of pH-dependent adsorption patterns, in addition, arsenite adsorption gradually increased until pH 9.2 and then sharply decreased with pH, whereas adsorption of arsenate was greatest at pH 2.0 and steadily decreased with the increasing pH from 2 to 12. The characteristics of these pH-dependent adsorption patterns might be caused by combined effects of the variation in the chemical speciation of arsenic and the surface charge of hematite. The experimental results on adsorption kinetics show that adsorption of both arsenic species onto hematite approached equilibrium within 20 h. Additionally, the pseudo-second-order model was evaluated to be the best fit for the adsorption kinetics of arsenic onto hematite, regardless of arsenic species, and the rate constant of As(V) adsorption was investigated to be larger than that of As(III).

• Analytical Science and Technology
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• v.36 no.3
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• pp.135-142
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• 2023

The total arsenic and 6 arsenic species were investigated in 56 fish collagen products using ICP-MS (Inductively coupled plasma-mass spectrometer) and HPLC-ICP-MS(High performance liquid chromatography-Inductively coupled plasma-mass spectrometer). The mean concentrations of total arsenic and arsenic species were 40.103±81.133 ㎍/kg (N.D.~586.686) and 30.070±50.378 ㎍/kg (N.D.~313.871), respectively. The mean concentration of inorganic arsenic was 24.610±32.706 ㎍/kg (N.D.~129.331), and the As(V) (Arsenate) was the most dominant. The standards and specifications of arsenic have not been established for fish collagen products. Our study presents that arsenic levels are relatively safe compared with not only previous studies but also domestic and international standards. However, in one sample, the total arsenic concentration was 586.686 ㎍/kg, showing the inorganic was 8.119 ㎍/kg, and the DMA was 305.752 ㎍/kg, which was high than the Canadian standard for organic arsenic. In conclusion, it is necessary to monitor arsenic levels consistently and establish standards and specifications of arsenic in fish collagen products to assure consumer safety.

• Journal of Environmental Science International
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• v.24 no.8
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• pp.1015-1021
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• 2015

In order to establish the design parameters of adsorption for arsenic compounds with hydrotalcite including chlorine ion, the basic properties of adsorption and desorption as well as the oxidation of As (III) were examined in batch tests. The maximum adsorption capacities of arsenite and arsenate were 6.2 mg-As(III)/g and 103 mg-As (V)/g, respectively. Although 80.4% of maximum desorption was shown in 20% NaOH solution, 5~10% of NaOH was recommended considering operating benefits, where the proper condition of the desorption was in the range of 73% to 80%. The most suitable desorption condition was in the combination of NaCl (10~20%) and NaOH (5~10%). Within 2 minutes, As (III) was easily oxidized to As (V) with 0.0001 N KMnO4, where the maximum oxidization ratio was shown to 98.9%.

• Journal of the Korean Society of Food Science and Nutrition
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• v.41 no.5
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• pp.674-680
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• 2012

As(III) and As(V) were analyzed in bamboo salts by hydride generation ICP-AES. In order to quantify the total amount of As in bamboo salts, $AsH_3$ was producted by reacting with 6 mol/L hydrochloric acid and $NaBH_4$, which was then analyzed by hydride generation ICP-AES. As(V) was quantified simultaneously after selectively quantifying As(III). As(III) was quantified by determining the total amount of As and then correcting for the amount of As(III). To improve the reliability of the analysis we repeated the experiment several times to check the detection limit, quantification limit, and measurements of our testing methods. According to the result of our quantification analysis of As existing in bamboo salt, the range of total As content was 0.05 mg/kg~0.2 mg/kg and As(V) was over 90% of the total As.