• The Korean Journal of Pesticide Science
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• v.15 no.4
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• pp.417-433
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• 2011

The study tested QuEChERS (quick, easy, cheap, effective, rugged and safe) sample preparation and HPLC-MS/ MS analysis for measurement of pesticide residues in fruit and vegetable. 240 kinds of pesticides spiked at three levels of 90, 45, 9 ng/g in lettuce and apple. For QuEChERS sample preparation, graphitized carbon black (GCB) was used for only lettuce in dispersive-SPE as absorbent. Matrix-matched standard calibration was used for quantitative analysis of HPLC-MS/MS. 218 pesticides (91%) in apple and 207 pesticides (86%) in lettuce showed recoveries in the range of 70~120% with $RSD{\leq}20%$. The lowest calibrated level (LCL) were 4.5 ng/g for 192 pesticides, 9 ng/g for 42 pesticides, 45 ng/g for 3 pesticides and 3 pesticides were not detected at all concentration levels. The results showed that the QuEChERS sample preparation and HPLC-MS/MS analysis can be applied to multi-residue analysis of pesticides in vegetables and fruits.

• Microbiology and Biotechnology Letters
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• v.35 no.2
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• pp.150-157
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• 2007

The advanced bioremediation of diesel-contaminated soil through the exploration of bacterial interaction with plants was studied. A diesel-degrading rhizobacterium, Rhodococcus sp.412, and a plant species, Zea mays, having tolerant against diesel was selected. Zea mays was seeded in uncontaminated soil or diesel-contaminated soil with or without Rhodococcus sp. 412. After cultivating for 30 days, the growth of Zea mays in the contaminated soil inoculated with Rhodococcus sp. 412 was better than that in the contaminated soil without the bacterium. The residual diesel concentrations were lowered by seeding Zea mays or inoculating Rhodococctis sp. 412. These results Indicate that the simultaneous use of Zea mays and Rhodococcus sp. 412 can give beneficial effect to the remediation of oil-contaminated soil. Bacterial community was characterized using a 16S rDNA PCR and denaturing gradient gel electrophoresis (DGGE) fingerprinting method. The similarities of DGGE fingerprints were $20.8{\sim}39.9%$ between the uncontaminated soil and diesel contaminated soil. The similarities of DGGE fingerprints were $21.9%{\sim}53.6%$ between the uncontaminated soil samples, and $31.6%{\sim}50.0%$ between the diesel-contaminated soil samples. This results indicated that the structure of bacterial community was significantly influence by diesel contamination.

• Journal of agricultural medicine and community health
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• v.36 no.4
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• pp.218-226
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• 2011

Objectives: Paraquat (PQ) is a widely used ionic pesticide that is fatal when ingested accidentally or for suicidal purposes. It is thought that chronic exposure of PQ is related with the development of Parkinson's disease, but epidemiological studies have not yet confirmed that theory. This study attempted to estimate the possibility of environmental PQ exposure through soil and water. Materials and Methods: We analyzed the amount of decomposed PQ solution in wet soil after exposure to ultraviolet light. An artificial rainfall condition was simulated over soil sprayed with PQ to measure the amount of eluted PQ. In addition, PQ was diluted in water from three differently rated rivers and the changes in PQ concentration were measured after ultraviolet exposure over one month. High performance liquid chromatography/ultra violet detection was used to analyze the concentrations of PQ. Results: In the method we used, the recovery rate of PQ showed a precision rate less than 5%, an accuracy greater than 88%, and the calibration equation was y=5538.8x-440.01($R^2$=0.9985). There were no significant differences in the concentrations of PQ obtained from the three specimens over a 1-week period. From the PQ-sprayed soil, the artificial rainfall conditions showed no PQ elution over a 1-month period, and there was no significant differences in PQ concentrations according to ultraviolet exposure among the three samples. Conclusions: PQ remains well adsorbed naturally in soil. However, it may still exist in an integrated state for a long time in the hydrosphere, so the possibility of PQ exposure through drinking water cannot be disqualified.

• Journal of the Korean Magnetics Society
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• v.5 no.4
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• pp.281-286
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• 1995

In order to study the effect of additives $SiO_{2}$ on the magnetic properties of hexaferrite sheet magnet, we used X-ray diffractometer, Mossbauer spectrometer, and VSM magnetometer. We have prepared $Ba_{0.25}Sr_{0.75}Fe_{12}O_{19}$ green sheets by the Dr. Blade method. Most of samples have a magnetoplurnbite crystal structure of typical M-type hexaferrite. The lattice parameters are found not to be affected by the addition of $SiO_{2}$. ${\alpha}-Fe_{2}O_{3}$ phase develops above $SiO_{2}$ 2.0 wt.%. Isomer shifts indicate that the valence of Fe ions is trivalent. Curie temperatures decrease slightly with increasing $SiO_{2}$ concentrations. It means that the $Si^{4+}$ subsitution for 12k-site $Fe^{3+}$ has an effect on the superexchange interactions Fe-O-Fe, which change the distance and the angle between cations and anions. It was suggested that ${\alpha}-Fe_{2}O_{3}$ phase results from the excessive Fe produced by subsituting $Si^{4+}$ for $Fe^{3+}$. Based upon the results of $Ba_{0.25}Sr_{0.75}Fe_{12}O_{19}$ added with $SiO_{2}$, we concluded that $H_{c}$, $M_{s}$ and $M_{r}$ depend more strongly on the microstructure chracteristics than on the cation substitution.

• Korean Journal of Microbiology
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• v.54 no.2
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• pp.105-112
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• 2018

To compare the denitrification efficiency, this study used molasses and methanol were used as external carbon sources. Specific experimental conditions were classified according to C/N ratio conditions. The batch test showed that the denitrification efficiency increased as C/N ratios of molasses and methanol rose. The most suitable C/N ratio of molasses turned out 4:1 considering the concentration of the residue chemical oxygen demand (COD) and the denitrification efficiency, which was 91.4%. Specific denitrification rate (SDNR) drawn as a kinetic factor demonstrated that molasses and methanol showed similar SDNR values as C/N ratios of molasses and methanol increased. Under the condition of C/N ratio 4:1, 0.0292 g $NO_3{^-}-N$ removal/g mixed liquor volatile suspended solid (MLVSS)/day (molasses), 0.0299 g $NO_3{^-}-N$ removal/g MLVSS/day (methanol) were found. Sludge adapted to molasses showed that Bacterium Pseudomonas sp. and Bergeylla sp. dominated through an analysis of microbial community. In addition, some bacteria were high convergences than the variety of microbial community. Accordingly, it was assumed that molasses focus on growing microorganisms specialized in denitrification and applied as a replaceable external carbon source that can enhance denitrification performance.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.11
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• pp.834-846
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• 2011

The objective of this study is to development of IDFIS system, that are consisted of hydrocyclone, rapid flocculation and inclined settler with chitosan coagulant. As the results of Jar test, a chitosan optimum dosage of 40 mg/L for river sediment, and 5 mg/L for tunnelling wastewater sediment, which these conditions leaves of residual turbidity of less than 5 NTU. Because of the effectiveness of chitosan in removing turbidity was independent on pH, the operation of IDFIS system would be simple. The synthesized turbidity was made with clay particles, river sediment, river suspended sediment, and tunnelling wastewater sediment. Results indicate that the mean overall removal efficiency of turbidity, SS, COD and TP were 98%, 99%, 85% and 95%, respectively. Chitosan is very efficient in removing turbidity in the entire turbidity range examined. IDFIS system would have possibility with compact design, because of the increase of floc size favours the floc settling speed and reduces the settling time.

• Korean Journal of Environmental Agriculture
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• v.16 no.4
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• pp.285-290
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• 1997

This study was conducted to develop labor-saving pesticide-fertilizer mixed formulation through a single application of mixed formulation of an insecticide imidacloprid coated on a slow release urea. The release of both total nitrogen and imidacloprid into water was delayed with increasing adhesive.Imidacloprid was released out 95% within 24 hours, whereas total nitrogen released in mixed formulation until 40 days was released less extent by increasing adhesive. There was no difference between pesticide-fertilizer mixed formulation and coated urea thereafter. The content of $NH_4-N$ in the soil treated with pesticide and urea seperating was higher until 10 days but gradually decreased compare to that of pesticide-fertilizer mixed formulation or coated urea. The population density of nitrate reducing bacteria and denitrifying bacteria in soil after treatment were lower in the pesticide-fertilizer mixed formulation and coated urea than those of pesticide and urea separate treatment. The residue of imidacloprid in soil was slightly higher in the treatment of pesticide alone than the pesticide-fertilizer mixed formulation and pesticide and urea seperating treatment. The population and control efficacy of small brown planthopper, Laodelphax striatellus, were not significance different among treatments.

• Analytical Science and Technology
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• v.29 no.4
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• pp.179-185
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• 2016

An effective analytical method has been developed for the determination of β-blockers(atenolol, metoprolol and propranolol) and 6 β-lactams(amoxicillin, penicillin G, cefaclor, cefadroxil, cephalexin and cephradine) in water samples using two different cartridges. The samples were extracted by solid-phase extraction (SPE) with the usage of polymeric hydrophile-lipophile balance(HLB cartridges) and strong cation-exchange mixed-mode polymeric sorbent (MCX cartridges). A XDB-C₁₈ column(1.8 μm; 3.0 mm × 100 mm) was used for the sufficient chromatographic resolution. The calibration curves showed good linearity with high correlation coefficients (>0.995). The method detection limits (MDL) and the limits of quantification(LOQ) were from 1.1 to 3.9 ng/L and from 5 to 13 ng/L, respectively. The method was applied for the determination of the target compounds in tributaries and raw water of the Han River and these were found at N.D. to 0.209 μg/L.

• Journal of Life Science
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• v.29 no.11
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• pp.1294-1303
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• 2019

Perchlorate is an anionic pollutant that is very soluble and stable in water. It has been detected not only in soil/ground water but also in surface water, drinking water, food, fish, and crops. Perchlorate inhibits iodine uptake by the thyroid gland and reduces production of thyroid hormones that are primarily responsible for regulation of metabolism. Although various technologies have been developed to remove perchlorate from the environment, biodegradation is the method of choice since it is economical and environmentally friendly. However there is limited information on perchlorate biodegradation in salt environment such as salt water. Therefore this paper reviews biodegradation of perchlorate in salt water and related microorganisms. Most biodegradation research has employed heterotrophic perchlorate removal using organic compounds such as acetate as electron donors. Biodegradation research has focused on perchlorate removal from spent brine generated by ion exchange technology that is primarily employed to clean up perchlorate-contaminated ground water. Continuous removal of perchlorate at up to 10% NaCl was shown when bioreactors were inoculated with enriched salt-tolerant perchlorate-reducing bacteria. However the reactors did not show long-term stable removal of perchlorate. Microorganisms belonging to ${\beta}$- and ${\gamma}$-Proteobacteria were dominant in bioreactors used to remove perchlorate from salt water. This review will help our understanding of perchlorate removal from salt water to develop a decent biotechnology for the process.

• Korean Journal of Environmental Agriculture
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• v.40 no.3
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• pp.203-210
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• 2021

BACKGROUND: Pesticides can persist in soil due to multiannual uses. To decrease the concerns for potential carry-over of such residues from treated soil during preceding crop cultivation to non-target crops grown in rotation, an uptake study of procymidone was conducted under the actual cultivation conditions in Korea. METHODS AND RESULTS: Procymidone was sprayed twice by foliar application with recommended and double dose according to the safe use guidelines for Korean cabbage up to 14 days before harvest. Arable land was kept fallow for 4 days after harvesting Korean cabbage, and spinach was cultivated as a succeeding crop. Initial residues in soil were 5.670-14.175 mg/kg that were degraded to 3.098-4.555 mg/kg until harvest of Korean cabbage, and then persisted at 1.026-1.300 mg/kg by spinach harvest. Procymidone residues in edible part of succeeding crops from soil uptake were in range of 0.020-0.048 mg/kg for recommended dose and 0.055-0.116 mg/kg for double dose. Root concentration factor (RCF) values of procymidone at different concentration ranged from 0.053 to 0.123, and translocation factor (TF) ranged from 0.176 to 0.768 for spinach. The value of TF was higher than RCF, indicating that the capability of translocation to shoot was relatively higher than that of root uptake and accumulation. CONCLUSION: Procymidone applied on Korean cabbage can be carried-over to spinach and detected at a level similar to MRL (0.05^T mg/kg). Therefore, this study suggests a follow-up study for establishment of plant back interval (PBI) of succeeding crops reflecting the actual agricultural conditions as this study.