• Journal of Soil and Groundwater Environment
• /
• v.20 no.5
• /
• pp.1-10
• /
• 2015

FeS, as a natural reduced iron mineral, has been recognized to be a viable reactive material for As(III) sequestration in natural and engineered systems. In this study, FeS-coated sand packed columns were tested to evaluate the As(III) removal capacities under anaerobic conditions at pH 5, 7 and 9. The column obtained As(III) removal capacity was then compared with the capacity result obtained from batch reactors. In the comparison, two different approaches were used. The first approach was used the total As(III) removal capacity which method was proved to be useful for interpreting pH 5 system. The second approach was used to consider sorption non-linearity and proved to be useful for interpreting the pH 9. The results demonstrated that a mechanistic understanding of the different removal processes at different pH conditions is important to interpret the column experimental results. At pH 5, where the precipitation of arsenic sulfide plays the major role in the removal of arsenic, the column shows a greater removal efficiency than the batch system due to the continuous dissolution of sulfide and precipitation of arsenic sulfide. At pH 9, where adsorption mainly governs the arsenic removal, the sorption nonlinearity should be considered in the estimation of the column capacity. This study highlighted the importance of understanding reaction mechanism to predict column performance using batch-obtained experimental results.

• Journal of Soil and Groundwater Environment
• /
• v.27 no.1
• /
• pp.25-30
• /
• 2022

Mackinawite (FeS), as a ubiquitous reduced iron mineral, is known as a key controller of redox reactions in anaerobic subsurface environment. The reaction of FeS with redox-sensitive toxic element such as arsenic is substantially affected by pH conditions of the given environments. In this study, the interaction of As(V) with FeS was studied under strict anaerobic conditions with various pH conditions. The pH-dependent arsenic removal tests were conducted under wide ranges of pH conditions and X-ray absorption spectroscopy (XAS) was applied to investigate the reaction mechanisms under pH 5, 7, and 9. The removal efficiency of FeS for As(V) showed the higher removal of As(V) under low pH conditions and its removal efficiency decreased with increasing pH, and no As(V) reduction was observed in 1 g/L FeS solution. However, XAS analysis indicated the reduction of As(V) to As(III) occurred during reaction between FeS and As(V). The reduced form of As(III) was particularly identified as an arsenic sulfide mineral (As₂S₃) in all pH conditions (pH 5, 7, and 9). As₂S₃ precipitation was more pronounced in pH 5 where the solubility of FeS is higher than in other pH conditions. The linear combination fitting results of XAS demonstrated that As(V) removal mechanism is concerted processes of As₂S₃ precipitation and surface complexation of both arsenic species.

• Journal of the Mineralogical Society of Korea
• /
• v.22 no.4
• /
• pp.331-342
• /
• 2009

Groundwater samples were collected from the bedrock aquifers related with Okcheon metasedimentary rocks. Arsenic (As) concentrations in the samples varied between 0.0051 and 0.887 mg/L, with an average of 0.0248. Cations and anions of groundwaters had no relationship with As contents as well as with spatial distribution of geology in the area. Pyrite, chalcopyrite and arsenopyrite in the core samples of the monitoring wells were identified in thin section, X-ray diffraction (XRD) and electron probe microscope analysis (EPMA). It was suggested that these minerals are responsible for the As in groundwater. The groundwater showed saturations with respect to calcite $(CaCO_3)$, dolomite (CaMg$(CO_3)_2$) and Magnesite $(MgCO_3)$. $HAsO_4{^{2-}}$ activities in the groundwater samples were close to $Ca_3(AsO_4)_2(c)$ and $Mn_3(AsO_4)_2(c)$ solubility isotherms, indicating that the maximum As contents in groundwater are secondly controlled by the precipitation and dissolution of carbonate minerals due to alkaline and oxic nature of the groundwater (pe+pH>10).

• Journal of Soil and Groundwater Environment
• /
• v.23 no.5
• /
• pp.17-25
• /
• 2018

The Boroo area in Mongolia is known to have been contaminated with heavy metals due to irregular gold mining activities and the release of mercury from gold extraction process. Soil and mine tailings were collected to analyze contamination patterns of heavy metals in the Boroo area. Analyses revealed that mercury, arsenic and cadmium concentrations exceeded the regulatory standard of the nation (Mongolia National Standard). In case of mercury, about 80% of the survey area was over the limit and the concentration distribution heavily influenced by influx of mercury through water transport. Soil contamination by arsenic was most severe that the concentration exceeded the regulatory limit in almost entire survey area, showing peak concentrations at nearby streams and river along with ore processing facilities. For cadmium, about 20% of the survey area was over the limit with the concentration distribution similar to that of arsenic.

• Journal of Soil and Groundwater Environment
• /
• v.21 no.6
• /
• pp.14-21
• /
• 2016

This study evaluated the applicability of stabilization of arsenic (As)-contaminated soil with iron (Fe) oxides at the former Janghang smelter site. Three Fe oxides (magnetite, goethite, and hematite) were tested as stabilizing agents to one soil sample collected from the study site. Amendment of 5% of magnetite, goethite, or hematite for one week showed the 64, 58, and 36% of reduction of the SBRC (Solubility/Bioavailability Research Consortium)-extractable (bioaccessible) As, respectively. Duration of stabilization more than one week did not show an additional reduction in SBRC-extractable As. Amendment of 5% of magnetite, which showed the highest As stabilization efficiency, was applied to 24 soil samples collected from the same site for one week, and 72% of reduction in the bioaccessible As was observed. The potential carcinogenic human health risk at the study site caused by As was $1.7{\times}10^{-5}$, which could be reduced to $8.1{\times}10^{-6}$ by the amendment of 5% magnetite for one week.

• Journal of Soil and Groundwater Environment
• /
• v.23 no.1
• /
• pp.85-91
• /
• 2018

Arsenic (As) usually is bound to amorphous iron oxides in the soils, and it can be removed via dissolution of iron oxides. Inorganic acid and chelating agent are widely used to extract As in the soil washing. However, the overall performance is highly dependent on the state of As fractionation. In this study, oxalic acid and inorganic acids (HCl, $H_2SO_4$, and $H_3PO_4$) were applied to enhance the dissolution of iron oxides for remediation of As-contaminated soils. Oxalic acid was most effective to extract As from soils and removal of As was two times greater than other inorganic acids. Additionally, 75% of As bound to amorphous iron oxides was removed by 0.2 M oxalic acid. Arsenic removal by oxalic acid was directly proportional to the sum of labile fractions of As instead of the total concentration of As. Therefore, the oxalic acid could extract most As bound to amorphous iron oxides.

• Journal of the Korean GEO-environmental Society
• /
• v.16 no.1
• /
• pp.55-60
• /
• 2015

As the water supply system has been installed over the country, the management of drinking water could be easier and controlled by experts. This helps to supply safe water to public. However, in rural area, small scale water treatment systems or groundwater haves been used as drinking water supplier. The drinking water including groundwater contains various contaminants. Private or small scale water treatment system can be contaminated with heavy metals such as arsenic, selenium and strontium which are usually originated from natural source. Arsenic, selenium and strontium have been determined from the goundwater, small scale water treatment system in the Kyungpook area. The results have been compared with the Korean and international standards. The results were analyzed on the geological characteristics of the area. Among the total of 1,412 samples, 76 samples showed higher concentration of arsenic than WHO guideline and the Korean drinking water standard. Total 4 samples had higher contents of selenium than WHO guideline which was $10{\mu}g/L$. In the analysis of geological characteristics, arsenic was highly released from a few area and which are in order of biotite granodiorite > biotite granite > daegu formation. Selenium has been highly released from biotite granite > black shale > diluvium.

• Environmental Engineering Research
• /
• v.13 no.1
• /
• pp.33-40
• /
• 2008

Levels of arsenic in stream and reservoir waters affected by an abandoned gold mine were examined. The abandoned mine has been left without proper civil and remedial works preventing potential environmental hazards. Field and laboratory chemical analyses revealed that the stream waters downgradient from the mine area were severely contaminated with arsenic and furthermore the reservoir water, 2-3 km away from the mine, also contained substantial levels of As, far exceeding the Korean stream water standard. Relatively higher pH values (6.5-9.4) enhanced mobility of As and mainly sustained substantial As concentration in waters. Chemistries of the stream water, groundwater and reservoir water were dominated by two main factors including effects of mine effluent and anthropogenic agricultural activities. Considering that there has been a substantial As input to the reservoir and the reservoir water has been used for agricultural and domestic uses, immediate remedial works are essentially required.

• Journal of Environmental Health Sciences
• /
• v.46 no.5
• /
• pp.513-524
• /
• 2020

Objective: The main purpose of this study is to evaluate the environmental and biological exposure of local residents who consumed arsenic-contaminated drinking water for less than one year. Methods: As a part of water quality inspections for small-scale water supply facilities, surveys were conducted of residents of two villages that exceeded the arsenic threshold for drinking water. The environmental impact survey consisted of surveys on water quality, soil, and crops in the surveyed area. Biological monitoring was performed by measuring the separation of arsenic species in urine and total arsenic in hair. Results: In the results of biological monitoring, the concentrations of AsIII and AsV were 0.08 and 0.16 ㎍/L, respectively. MMA and DMA were 0.87 and 36.19 ㎍/L. There was no statistically significant difference between the group who drank arsenic-removed groundwater or water from the small-scale supply facility and the group who drank tap water, purified water, or commercial bottled water. Some of the water samples exceeded the arsenic threshold for drinking water. There were no samples in the soil or rice that exceeded the acceptable threshold. Conclusion: In the case of short-term exposure to arsenic-contaminated drinking water for less than one year, there were no significant problems of concern from the evaluation of biological monitoring after arsenic was removed.

• Proceedings of the KSEEG Conference
• /
• 2004.12a
• /
• pp.9-28
• /
• 2004

Concern about arsenic is increasing throughout the world, including areas of the United States. Elevated levels of arsenic above current drinking-water regulations in ground and surface water can be the result of purely natural phenomena, but often are due to anthropogenic activities, such as mining and agriculture. The current study correlates arsenic speciation in acid mine drainage and mining influenced water with the important water-chemistry properties Eh, pH, and iron(III) concentration. The results show that arsenic speciation is generally in equilibrium with iron chemistry in low pH AMD, which is often not the case in other natural-water matrices. High pH mine waters and groundwater do not 짐ways hold to the redox predictions as well as low pH AMD samples. The oxidation and precipitation of oxyhydroxides depletes iron from some systems, and this also affects arsenite and arsenate concentrations differently through sorption processes.