Characteristics of metal contamination in paddy soils from three industrial cities in South Korea

Paddy soil contamination is directly linked to human dietary exposure to toxic chemicals via crop consumption. In Korea, rice paddy fields are often located around industrial complexes, a major anthropogenic source of metals. In this study, rice paddy soils were collected from 50 sites in three industrial cities to investigate the contamination characteristics and ecological risk of metals in the soils. The cities studied and their major industries are as follows: Ulsan (petrochemical, nonferrous, automobile, and shipbuilding), Pohang (iron and steel), and Gwangyang (iron and steel, nonmetallic, and petrochemical). Thirteen metals (Al, As, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, V, and Zn) were analyzed using inductively coupled plasma–optical emission spectrometry (ICP–OES). The mean concentration of Cd (1.98 mg/kg) exceeded the soil quality guideline of Canada (1.4 mg/kg), whereas concentrations of other metals were under the standards of both Korea and Canada. Generally, levels of metal concentrations decreased with increasing distance from industrial complexes. Among the three cities, Pohang showed high concentrations of Zn (142.2 mg/kg), and Ulsan and Gwangyang showed high concentrations of Cr (33.9 mg/kg) and Ba (126.4 mg/kg), respectively. These contamination patterns were influenced by the different major industries of each city, which was clearly demonstrated by the principal component analysis results. Pollution indices suggested that As, Cd, Pb, and Zn were enriched in the paddy soils via anthropogenic activities. Comprehensive potential ecological risk indices were at considerable levels for most sites, especially because of major contributions from As and Cd, which can pose potential ecological threats.

     

Submerged arc plasma system combined with ozone oxidation for the treatment of wastewater containing non-degradable organic compounds

• Submerged arc plasma was introduced in terms of wastewater treatment. • Ozone oxidation was coupled with submerged arc plasma system. • Ozone was converted into O and O₂ by submerged arc plasma. • Decomposition rate was accelerated by submerged arc plasma. • Introduction of ozone led to significant increase in mineralization. Submerged arc plasma technology was assessed for the removal of phenols from wastewater. The OH radicals generated from the boundary between the plasma and waste solution were considered as a significant factor on the degradation reaction. In this study, the effects of highly energetic electrons released from the submerged arc plasma were mainly studied. The highly energetic electrons directly broke the strong chemical bond and locally increased the reaction temperatures in solution. The effects of the submerged-arc plasma on the decomposition of phenol are discussed in terms of the input energy and initial concentration. The single use of submerged arc plasma easily decomposed the phenol but did not increase the mineralization efficiency. Therefore, the submerged arc plasma, coupled with the ozone injection, was investigated. The submerged arc plasma combined with ozone injection had a synergic effect, which led to significant improvements in mineralization with only a small increase in input energy. The decomposition mechanism of phenol by the submerged arc plasma with the ozone was analyzed.     

Assessment of soil washing for heavy metal contaminated paddy soil using FeCl3 washing solutions

Environmental Geochemistry and Health - In this study, soil washing is applied for the remediation of heavy-metal (Pb, Cu and Zn) contaminated paddy soil located near an abandoned mine area. FeCl3...     

As(III) adsorption onto Fe-impregnated food waste biochar: experimental investigation,modeling, and optimization using response surface methodology

Biochar derived from food waste was modified with Fe to enhance its adsorption capacity for As(III), which is the most toxic form of As. The synthesis of Fe-impregnated food waste biochar (Fe-FWB) was optimized using response surface methodology (RSM), and the pyrolysis time (1.0, 2.5, and 4.0 h), temperature (300, 450, and 600 °C), and Fe concentration (0.1, 0.3, and 0.5 M) were set as independent variables. The pyrolysis temperature and Fe concentration significantly influenced the As(III) removal, but the effect of pyrolysis time was insignificant. The optimum conditions for the synthesis of Fe-FWB were 1 h and 300 °C with a 0.42-M Fe concentration. Both physical and chemical properties of the optimized Fe-FWB were studied. They were also used for kinetic, equilibrium, thermodynamic, pH, and competing anion studies. Kinetic adsorption experiments demonstrated that the pseudo-second-order model had a superior fit for As(III) adsorption than the pseudo-first-order model. The maximum adsorption capacity derived from the Langmuir model was 119.5 mg/g, which surpassed that of other adsorbents published in the literature. Maximum As(III) adsorption occurred at an elevated pH in the range from 3 to 11 owing to the presence of As(III) as H₂AsO₃^? above a pH of 9.2. A slight reduction in As(III) adsorption was observed in the existence of bicarbonate, hydrogen phosphate, nitrate, and sulfate even at a high concentration of 10 mM. This study demonstrates that aqueous solutions can be treated using Fe-FWB, which is an affordable and readily available resource for As(III) removal.

     

Determination of soil contamination sources in mining area using Zn/Cd ratios with mobile Cd

Environmental Geochemistry and Health - Paddy fields near metalliferous mining area are sometimes contaminated by tailings or mine water. In the contaminated paddy fields around the abandoned...     

Identification of iron and sulfate release processes during riverbank filtration using chemical mass balance modeling

Environmental Geochemistry and Health - Various hydrogeochemical processes can modify the quality of river water during riverbank filtration (RBF). Identifying the subsurface processes responsible...     

Exposure assessment of particulate matter and blood chromium levels in people living near a cement plant

This study evaluates the effect of air pollution caused by cement plants on nearby residential areas and performs an exposure assessment of particulate matter (PM) and total Cr, Cr⁶⁺, Pb, and Al. Further, the blood Cr levels of residents exposed to PM released by cement plants are also assessed. Nine buildings (eight residential and one elementary school building) close to cement plants were selected for this study, which were located in Pyeongtaek port, in west of Gyeonggi Province, South Korea. A total of 51 suspended particulate samples were collected at a flow rate of 2.0 L/min. Total Cr was more widely detected in residents’ houses and elementary schools. PM levels were higher at distances of 4.1 and 4.8 km than those at closer distances of 2.7 km. This was due to the influence of wind direction. The estimated mean blood level of Cr for the study participants was 3.80 μg/L, which is higher than levels estimated by other studies on Cr blood levels. Therefore, cement plants could cause an increase in total Cr and blood Cr levels in residential areas, and more continuous monitoring is necessary to better understand their impacts.     

Sensitivity analysis on the ecological bias for Seoul tuberculosis data

In ecological studies, researchers often try to convey the analysis results to individual level based on aggregate data. In order to do this correctly, the possibility of ecological bias should be studied and addressed. One of the key ideas used to address the ecological bias issue is to derive the ecological model from the individual model and to check whether the parameter of interest in the individual model is identifiable in the ecological model. However, the procedure depends on unverifiable assumptions, and we recommend checking how sensitive the results are to these unverifiable assumptions. We analyzed the tuberculosis data that was collected in Seoul in 2005 using a spatial ecological regression model for the aggregate count data with spatial correlation, and found that the deprivation index is likely to have a small positive effect on the occurrence risk of tuberculosis in individual level in Seoul. We considered this finding in various aspects by performing in depth sensitivity analyses. In particular, our findings are shown to be robust to the distribution assumptions for the individual exposure and missing binary covariate across various scenarios.     

Effects of SO<Subscript>2</Subscript> contamination on rising CO<Subscript>2</Subscript> drops under high pressure

Although the flow dynamics of pure liquid drops in other liquids has been well researched, little attention has been paid to the impacts of impurities. Hence, most of research is not directly applicable to the real world. To address this gap, we conducted numerical experiments simulating the rise of pure and contaminated drops. It was selected to study liquid CO₂ drops contaminated with SO₂ under high pressure because such mixtures mimic potential scenarios in which drops may leak from carbon capture and storage (CCS) facilities or pipelines. First, numerical simulation experiments were performed to validate our method by comparing our results with previous research on pure drops. Second, the validated numerical approach was applied to simulations of contaminated drops to investigate how contaminants affect rising drops. The results show that the SO₂ contamination caused changes in deformation, breakup phenomena, rising velocities, surrounding flow fields and drag coefficients. Most importantly, the contamination resulted in the formation of smaller “child drops”; such breakup is not observed in pure CO₂ drops. The formation of child drops in turn affects the streamlines, patterns and areas of wakes behind the contaminated drops. The addition of contaminants also enhances the dissolution rate, which is affected by the contaminant concentration and by the flow dynamics of the rising drop. Our results would improve understanding the rise of impure CO₂ drops, such as drops potentially leaked by future CCS operations.     

Sonication and grinding pre-treatments on <Emphasis Type="Italic">Gelidium amansii</Emphasis> seaweed for the extraction and characterization of Agarose

Various pretreatments methods including sonication and grinding were performed on red seaweed Gelidium amansii for the subsequent extraction of agarose. The agarose products are usually extracted from agar powder products from seaweeds. In this study, the agarose was extracted using a direct polyethylene glycol (PEG) method without the need to first process the agar from seaweed. The agar extract was frozen then thawed and mixed directly with PEG solution to precipitate the agarose. The quality of agarose obtained was evaluated through physico-chemical properties analysis which includes spectral technique (FTIR), melting and boiling point, gel strength and sulfate content. These properties were compared with a non-pretreated sample and it was found that the addition of pretreatment steps improved the quality of agarose but gave a slightly lower yield. The gel strength of pretreated samples was much higher and the sulfate content was lower compared to non-pretreated samples. The best pretreatment method was sonication which gave gel strength of 742 g cm^-2 and sulfate content of 0.63%. The extraction of agarose can be further improved with the use of different neutralizing agents. Pretreating the seaweed shows potential in improving the quality of agarose from seaweed and can be applied for future extraction of the agarose.

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