• Journal of The Korean Society of Agricultural Engineers
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• v.48 no.3
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• pp.3-8
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• 2006

The fractions of nitrogen were investigated in the soils of reclaimed and natural tidelands of southwest coastal area of Korea. The content of total-N varied to ranged form 619 to 5,534 mg/kg dry weight with a mean value of 1,857 mg/kg. The order of different fractions of nitrogen was as follows: Acid non-extractable-N > uncounted-N > acid extractable-N > ammonia-N > nitrate-N. The content of ammonia-N, acid extractable-N, and acid non-extractable-N showed highly negative correlations with pH. The content of acid extractable-N and ammonia-N showed highly positive correlation with clay content.

• Korean Journal of Soil Science and Fertilizer
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• v.44 no.6
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• pp.1314-1319
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• 2011

This study was carried out to investigate the surface soil organic carbon fractions affecting by different land use types, including needle-leaf forest (FN), broad-leaf forest (FB), pasture, annual upland cropping land (upland), and paddy rice land (paddy). We chose seven regions across Korean inland, considering sea level altitude, and measured soil organic carbon content and physico-chemical properties such as bulk density at a depth of 0~15 cm using core samples in April for the each land use type. In addition, labile organic carbon fractions in soil including light fraction and hot water extractable carbon were investigated. From this study, organic carbon storage (Mg C per ha) in the upper 15-cm soils was highest in FB (37.8), and decreased in the order of pasture (29.1), FN (28.8), paddy (21.9), and upland crop (19.9). In forest, more than 20% of soil organic carbon existed as light fraction, the free organic matter. Hot-water extractable carbon contents of soils in five land use types were lower than 7% of their soil organic carbon content.

• Applied Biological Chemistry
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• v.45 no.3
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• pp.152-156
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• 2002

Soils near abandoned zinc mines were known to be contaminated with arsenic-rich mining by-products. To examine the potential impacts of arsenic- contaminated soils on plant growth, surface soils were subjected to sequential extraction. Results revealed that 54% and 74% total As and 74% total extractable As were bound to iron hydrous oxide, and water soluble fraction was below detection limit. Arsenic faction extracted using the Koran standard method(dissolution of metals via treatment of 1 N HCI) was strongly correlated with the Fe-bound As fraction ($r^2=0.884**$). Arsenic level in rice plant roots was the highest with a maximum value of 154.9 mg/kg, whereas it was below 0.6 mg/kg in grains. Arsenic level in rice plant roots was strongly correlated with those of Al-bound As ($r^2=0.821**$) and 1N HCI-extractable As levels ($r^2=0.801**$).

• Korean Journal of Pharmacognosy
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• v.10 no.3
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• pp.119-124
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• 1979

Both wild peony and cultivated peony demonstrated a slight effect and tranquilizer of anti-convulsion on the strychinine and picrotoxine but the wild plant was more effective. The methanol extract of cultivated peony root demonstrated a weak effect of muscle loosening but its mixture with water extractable fraction did not have this effect in contrast to the case wild type whose methanol extract mixture with water extractable fraction still retained a strong anti-convulsional muscle loosening effect. Therefore, it is concluded that wild peony root has more analgesic and muscle loosening effect than the cultivated counterpart has.

• Korean Journal of Soil Science and Fertilizer
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• v.41 no.3
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• pp.184-189
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• 2008

To assess the relationship between Cd fraction in paddy soils and Cd in polished rice, soils and rice were analyzed at the 3 Cd contaminated paddy fields near closed mines. Major Cd fractions of A field were organically bound (62.6%) and Fe-Mn oxide bound (25.3%) forms. In case of B field, major Cd fractions of B1 field were carbonate bound (46.3%) and Fe-Mn oxide bound (31.6%) form whereas B2 field were residual (54.3%) and carbonate bound (21.8%) form, respectively. It showed a huge difference of Cd fraction each other. 0.1M HCl extractable Cd in soil was positively correlated with Cd in rice. Specially, the ratios of 0.1M HCl extractable Cd against total Cd content in soils were 13.7%, 2.6%, and 0.45% in A, B1, and B2 fields, respectively. These ratio were largely affected with Cd uptake to rice grain. Also, exchangable, Fe-Mn oxide bound, and carbonate bound form, which are partially bioavailable Cd fraction to the plant, were positively correlated with Cd in rice while organically bound and residual form was not correlated. Multiple regression equation was developed with Rice Cd = -0.02861 + 0.07456 FR 1(exchangeable) + 0.00252 FR 2(carbonate bound) + 0.001075 FR 3(Fe Mn oxide bound) - 0.00095 FR 4(organically bound) - 0.00348 FR 5(residual) ($R^2=0.7893^{***}$) considering Cd fraction in soils.

• YAKHAK HOEJI
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• v.33 no.1
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• pp.46-53
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• 1989

The extractable organic matter was extraced from airborne particulates collected in Seoul during 1986. It was fractionated to several fracrtions and mutagenicities of them were tested in Salmonella thyphimurium TA98 by Ames method. The neutral fraction showed the highest indirect acting mutagenicity while the highest direct acting mutagenicity was observed in the acidic fraction. Indirect acting mutagenicity of airborne particulate was attributed to its neutral fraction about 88% in average, to acidic about 10% in average and to basic fraction about 2% in average. Direct acting mutagenicity of airborne particulate was attributed to its neutral fraction about 70%, to acidic fraction about 29% and to basic fraction about 1%. Among five subfractions of neutral fraction, the proportion of mutagenicity of polynuclear aromatic hydrocarbon subfraction was 13.2% in indirect acting mutagenicity and 5.0% in direct acting mutagenicity.

• Korean Journal of Environmental Agriculture
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• v.5 no.2
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• pp.85-94
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• 1986

To study fate of carbofuran in paddy system, C-14 labelled carbofuran was applied to paddy water containing rice seedlings and time course study was made on the distribution, metabolism and chemical transformation of the systemic insecticide. Carbofuran was readily absorbed by plant root and translocated to shoots where most of the radioactivities were confined to leaf tips. The fact that gradual increases in radioactivities of both aqueous phase extracts and non-extractable fractions of plants (shoots and root) increased with incubation is taken as an evidence that reactions (phase I and II) proceed in rice plants. Carbofuran and its five metabolites were all detected by TLC in organic phase extracts of paddy plants or soil. Evidence was put forward that carbofuran and its five metabolites were all identified as aglycones of conjugates. 7-benzofuranol and 3-hydroxycarbofuran were the most abundant aglycones. Soil microbes appears to have little effects on the metabolism of carbofuran. They increased radioactivity of non-extractable fraction and reduced that of organic phase extracts of paddy soil.

• Environmental Analysis Health and Toxicology
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• v.16 no.4
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• pp.143-151
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• 2001

Six rivers were selected as preliminary screening sites to determine the test conditions of Microtox in assessing the toxicity of the sediment. In addition, a pH range of 6.0∼6.5 was established in testing pore water, aqueous extracts and organic extracts. Each extractable fraction of sediment showed different toxicities. Therefore, in order to properly examine the toxicity in the sediment, all extractable fractions of sediment samples needed to be tested with Microtox. Thus, sediment samples were additionally collected from at least 4 secondary sites within 50∼100ｍ area of the primary sampling site to reduce any variation or deviation in toxicity assessment. From all sediment toxicity data that was collected from this study, it was concluded that the Keumho river was the most polluted with the highest sediment toxicity of all the rivers analyzed and needed further detailed research on its pollution problem.

• Journal of Soil and Groundwater Environment
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• v.25 no.2
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• pp.9-15
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• 2020

This study was conducted to investigate the in situ formation of amorphous Fe oxides as a stabilization technology in As-contaminated soil. After addition of ferric nitrate and the neutralizing agent, most of extractable fractions of As in soil (i.e., SO₄^2- and PO₄^3--extractable As) was converted into As bound to amorphous Fe oxides. In addition, results of solubility bioavailability research consortium (SBRC) test indicated that a significant amount of As in untreated soil changed to a non-bioaccessible form after stabilization. The reason was attributed to the newly formed amorphous Fe oxides in the stabilized soil, which was confirmed by linear combination of fitting (LCF) using X-ray absorption spectroscopy (XAS) analysis. Interestingly, after five months of aging of the stabilized soil, ferrihydrite and schwertmannite newly formed in the soil were transformed to crystalline Fe oxides such as goethite, and further decrease in SBRC extractable fraction of As was observed. The results suggest that co-precipitated As with amorphous Fe oxides can be further immobilized with time, due to the crystallization of amorphous Fe oxides.

• Korean Journal of Environmental Agriculture
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• v.25 no.3
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• pp.236-246
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• 2006

In this study, we give insight into questionable results that can be encountered in the conventional sequential extraction of heavy metals (Cd, Cu, and Zn) from soils. Objectives of this study were to determine the extraction variability of exchangeable (EXC)-metals as using six different EXC-extractants commonly accepted, and to investigate selectivity problems with carbonates bound (CAB)-metal fraction, a buffered acetate (1.0 M NaOAc; pH 5.0) extractable-metal fraction, leading to erratic results in especially non-calcareous soils. The contents of EXC-metals were markedly varied with the different extractability of various EXC-metal extractants used. The contents of EXC-Cd fraction were ranged from 2.0 to 74.3% of total Cd content in all of the metal spiked soils studied. The contents of EXC-Zn fraction extracted with the different EXC-extractants were varied with soil types, which were from 0.4 to 3.9% of total Zn in the calcareous soils, from 7.6 to 17.9% in the acidic soil, and from 13.6 to 56.8% in the peat soil. However, the contents of EXC-Cu fraction were relatively similar among the applications of different EXC-meal extractants, 0.2 to 2.1 % of total Cu, in all soils tested. Also, these varied amounts of EXC-metal fractions, especially Cd and Zn, seriously impacted the contents of subsequent metal fractions in the procedure. Furthermore, the CAB-Cd, -Cu, and -Zn fractions extracted by the buffered acetate solution were in critical problem. That is, the buffered acetate solution dissolved not only CAB-metals but also metals that bound or occupied to subsequent fractions, especially OXD-metal fraction, in both calcareous and non-calcareous soils. The erratic results of CAB-fraction also seriously impacted the amounts of subsequent metal fractions. Therefore, the conventional sequential extraction should be reconsidered theoretically and experimentally to quantify the target metal fractions or might be progressively discarded.