• Nuclear Engineering and Technology
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• 제34권5호
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• pp.517-531
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• 2002

The speciation and solubility of Am, Np, Pu and U have been analyzed by means of the geochemical code MUGREM, under the chemical conditions of domestic deep groundwater, in order to support the preliminary safety assessment for a Korean HLW disposal concept. Under the conditions of groundwaters studied, the stable solid phase is AmOHC $O_3$(s) or Am(OH)$_3$(s), soddyite((U $O_2$)$_2$ $SiO_2$.2$H_2O$) or N $a_2$ $U_2$ $O_{7}$ (c), Np(OH)$_4$(am), and Pu(OH)$_4$(am) for Am, U, Np, and Pu, respectively. The dominating aqueous species are as follows: the complexes of Am(III), Am(OH)$_2$$^{+}$ and Am(C $O_3$)$_2$$^{[-10]}$ , the complexes of U(VI), U $O_2$(OH)$_3$$^{[-10]}$ and U $O_2$(C $O_3$)$_3$$^{4-}$, the complexes of Np(IV), Np(OH)$_4$(aq) and Np(OH)$_3$C $O_3$, and the complexes of Pu(IV), Pu(OH)$_4$(aq) and Pu(OH)$_3$C $O_3$$^{[-10]}$ . The calculated solubilities exist between 1.9E-10 and 1.3E-9 mol/L for Am, between 5.6E-6 and 1.2E-4 mol/L for U, between 3.1E-9 and 1.3E-8 mol/L for Np, and between 6.6E-10 and 2.4E-10 mol/L for Pu, depending on groundwater conditions. The present solubilities of each actinide agree well with the results of other studies obtained under similar conditions.s.

• ALGAE
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• 제35권2호
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• pp.167-176
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• 2020

Iodine exists as a trace element in seawater, with total iodine being generally constant at about 0.45-0.55 μM. Almost all of this iodine occurs in two main forms: iodate and iodide. Iodate is the thermodynamically stable form under normal seawater conditions, and thus should be the only iodine-containing species in the water column. However, iodate concentrations are found to vary considerably, being generally greater at depth and lower at the surface, while iodide concentrations follow the reverse pattern, being anomalously accumulated in the euphotic zone and decreasing with depth. The fact that iodide concentrations follow a depth dependence corresponding to the euphotic zone suggests that biological activity is the source of the reduced iodine. Nonetheless, the nature and source of iodate reduction activity remains controversial. Here, using a combination of field and laboratory studies, we examine some of the questions raised in our and other previous studies, and seek further correlations between changes in iodine speciation and the presence of marine macro- and microalgae. The present results indicate that microalgal growth per se does not seem to be responsible for the reduction of iodate to iodide. However, there is some support for the hypothesis that iodate reduction can occur due to release of cellular reducing agents that accompany cell senescence during phytoplankton bloom declines. In addition, support is given to the concept that macroalgal species such as giant kelp (Macrocystis pyrifera) can take up both iodide and iodate from seawater (albeit on a slower time scale). We propose a mechanism whereby iodate is reduced to iodide at the cell surface by cell surface reductases and is taken up directly as such without reentering the bulk solution.

• Ocean and Polar Research
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• 제32권3호
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• pp.177-186
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• 2010

A sequential extraction technique was used to study sediment phosphorus speciation and its relative importance in the intertidal flat of Keunso Bay during summer and winter for a better understanding of the phosphorus cycle and bioavailability in intertidal sediments. Loosely sorbed P contents were the lowest among the five P-pools and showed little seasonal or spatial variation. Although Fe-bound P contents were almost constant in winter, they decreased rapidly with sediment depth in summer. The dissolution of Fe oxides, used as an oxidant for the anaerobic respiration, ascribed the rapid decrease of Fe-bound P in summer. Al-bound P contents displayed little seasonal variation, but showed a large spatial variation, with higher values in the upper intertidal flat. Comprising about 50% of total P, Ca-bound P contents were the highest among the five P-pools. Ca-bound P contents were higher in winter than summer, but did not exhibit a clear spatial variation. Organic P contents were higher in summer than winter, which was associated with higher primary production and clam biomass in summer. Organic P contents were higher in the lower intertidal flat than the upper intertidal flat. In Keunso Bay, bioavailable P contents of the intertidal flat comprising about one third of total P ranged from 2.41 to 5.09 ${\mu}molg^{-1}$ in summer and 3.82 to 5.29 ${\mu}molg^{-1}$ in winter. The bioavailability of P contents was higher in the lower intertidal flat than the upper intertidal flat, which was attributed to the large clam production in the lower intertidal flat.

• 대한환경공학회지
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• 제28권5호
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• pp.472-479
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• 2006

퇴적물로부터 오염물질 용출은 상등수 수질에 많은 영향을 미친다. 본 연구에서는 pH와 산화환원전위에 따른 상등수 및 퇴적물의 인 존재형태의 변화를 관찰하였다. 상등수가 순환되어 호기성 상태를 유지하는 경우, 성층현상으로 인하여 혐기성을 띠는 경우, 퇴적물 상부에 모래 캡핑이 포설된 상태에서 혐기성을 띠는 경우 등 3가지 경우를 가정하여 상등수의 인 형태별 농도를 측정하였다. 퇴적물에서 인 용출은 상등수가 산성일 경우 증가하였으며, 캡핑은 인 용출량을 저감시키고, $PO_4-P$의 용출을 지연시키는 효과가 있는 것으로 나타났다. 상등수와 퇴적물이 혐기성일 때 상등수의 pe/pH가 인이 apatite 상태로 안정하게 존해하는 범위에서 상등수의 인농도는 감소하여 일정한 농도를 나타냈다. 세개의 칼럼에서 최종 평균 인 농도는 순환칼럼에서 0.223 mg/L, 비순환칼럼에서 0.342 mg/L, 캡핑칼럼에서 0.184 mg/L로 캡핑된 칼럼에서 가장 낮게 나타났다. 성층현상에 의해 수질이 악화될 수 있는 호소에 캡핑을 활용할 경우 퇴적물에 의해서 상등수의 인 농도를 감소할 수 있을 것으로 기대된다.

• Bulletin of the Korean Chemical Society
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• 제31권10호
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• pp.2813-2818
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• 2010

A novel method was developed for the speciation of chromium in natural water samples based on homogeneous liquid-liquid extraction and determination by flame atomic absorption spectrometry (FAAS). In this method, Cr(III) reacts with a new Schiff's base ligand to form the hydrophobic complex, which is subsequently entrapped in the sediment phase, whereas Cr(VI) remained in aqueous phase. The Cr(VI) assay is based on its reduction to Cr(III) by the addition of sodium sulfite to the sample solution. Thus, separation of Cr(III) and Cr(VI) could be realized. Homogeneous liquid-liquid extraction based on the pH-independent phase-separation process was investigated using a ternary solvent system (water-tetrabutylammonium ion ($TBA^+$)-chloroform) for the preconcentration of chromium. The phase separation phenomenon occurred by an ion-pair formation of TBA and perchlorate ion. Then sedimented phase was separated using a $100\;{\mu}L$ micro-syringe and diluted to 1.0 mL with ethanol. The sample was introduced into the flame by conventional aspiration. After the optimization of complexation and extraction conditions such as pH = 9.5, [ligand] = $1.0{\times}10^{-4}\;M$, [$TBA^+$] = $2.0{\times}10^{-2}\;M$, [$CHCl_3$] = $100.0\;{\mu}L$ and [$ClO_4$] = $2.0{\times}10{-2}\;M$, a preconcentration factor (Va/Vs) of 100 was obtained for only 10 mL of the sample. The relative standard deviation was 2.8% (n = 10). The limit of detection was sufficiently low and lie at ppb level. The proposed method was applied for the extraction and determination of chromium in natural water samples with satisfactory results.

• 식물분류학회지
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• 제35권2호
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• pp.99-114
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• 2005

한국산 땅비싸리속 식물의 종분화를 연구하기위해 염색체수, 형태적변이 및 RAPD분석을 실시하였다. 땅비싸리(2n=16) 와 좀땅비싸리(2n=32)의 염색체수는 기존의 보고와 일치하였다. 본 연구에서 큰꽃땅비싸리의 4배체(2n=32)와 6배체(2n=48)집단이 새로 조사되었다. 큰꽃땅비싸리는 가야산 부근에서 땅비싸리와 좀땅비싸리와 함께 자라고 있었다. 큰꽃땅비싸리는 이들 두 종에 비해 식물체 높이, 잎 및 꽃이 더 크며, 땅비싸리 근연종에서 중요한 분류형질인 잎과 꽃의 털에서 땅비싸리와 좀땅비싸리의 중간 형태를 보이고 있다. RAPD분석에서 큰꽃땅비싸리는 좀땅비싸리와 더 유사하였으나, 4배체와 6배체 간에 차이를 보였다. 이러한 결과는 한반도 고유종인 큰꽃땅비싸리가 공동분포지인 가야산 지역에서 땅비싸리와 좀땅비싸리 사이의 잡종현상과 함께 배수체현상에 의해 기원된 것으로 사료된다.

• 한국환경보건학회지
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• 제47권5호
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• pp.496-503
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• 2021

Background: Considering the expenses of and difficulties in arsenic speciation by high performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS), alternative measurement methods should be useful, especially for large-scale research and projects. Objectives: A measurement method was developed for arsenic speciation using HPLC-atomic fluorescence spectrometry (HPLC-AFS) as an alternative to HPLC-ICP-MS. Methods: Total arsenic and toxic arsenic species in some seafoods were determined by atomic absorption spectrometry coupled with hydride vapor generation (AAS-HVG) and HPLC-AFS, respectively. Recovery rate of arsenic species in seafood was evaluated by ultra sonication, microwave and enzyme (pepsin) for the optimal extraction method. Results: Limits of detection of HPLC-AFS for As³⁺, dimethylarsinate (DMA), monomethylarsonate (MMA) and As⁵⁺ were 0.39, 0.53, 0.60 and 0.64 ㎍/L, respectively. The average accuracy ranged from 97.5 to 108.7%, and the coefficient of variation was in the range of 1.2~16.7%. As³⁺, DMA, MMA and As⁵⁺ were detected in kelp, the sum of toxic arsenic in kelp was 40.4 mg/kg. As³⁺, DMA, MMA and As⁵⁺ were not detected in shrimp and squid, but total arsenic (iAS and oAS) content in shrimp and squid analyzed by AAS-HVG were 18.1 and 24.7 mg/kg, respectively. Conclusions: HPLC-AFS was recommendable for the quantitative analysis method of arsenic species. As toxic arsenic species are detected in seaweeds, further researches are needed for the contribution degree of seafood in arsenic exposure.

• Horticulture, Environment, and Biotechnology : HEB
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• 제59권6호
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• pp.775-786
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• 2018

To test the hypothesis that humic acid (HA), anaerobically digested pig slurry filtrate (APS), and their combination would differently affect the chemical speciation and extractability of metals (cadmium, copper, and zinc) and their uptake by plants, we conducted a pot experiment using wormwood in two texturally contrasting soils (sandy loam and clay loam) collected from a field near an abandoned Cu mine. Four treatments were laid out: HA at $ 23.5g\;kg^{-1}$ (HA), APS at $330mL\;kg^{-1}$ (APS), HA at $ 23.5g\;kg^{-1}$ and APS at $330mL\;kg^{-1}$ (HA + APS), and a control. Each treatment affected the chemical speciation and mobility of the metals, and thereby resulting in variable patterns of plant biomass yield and metal uptake. The APS supported plant growth by increasing nutrient availability. HA supported or hindered plant growth by impacting the soil's water and nutrient retention capacity and aeration, in a soil texture-dependent manner, while consistently enhancing the immobilization of heavy metals. Temporal increases in whole-plant dry matter yield and metal accumulation suggested that the plants were capable of metal hyperaccumulation. The results were discussed in terms of the mobility of metals and plant growth and corroborated by the $^{15}N$ recovery of soil- and plant-N pools under H and HS treatments. Therefore, for effective phytoremediation of polluted soils, an appropriate combination of plant growth promoters (APS) and chelating agents (HA) should be predetermined at the site where chemical stabilization of pollutants is desired.

• 식물분류학회지
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• 제52권4호
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• pp.226-234
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• 2022

The study aims are to examine the characteristics of artificial and natural hybrids between Viola albida var. albida (= albida, from below) and V. albida var. chaerophylloides (= chaerophylloides, from below), and to confirm if hybrids could be fertile and make populations in their native habitats. The 1st filial (= F₁, from below) leaf shape produced by artificial crossing between albida and chaerophylloides was the same as that of V. albida var. takahashii (= takahashii, from below), and F₁ bore also both chasmogamous and cleistogamous flowers. F₁ seed number was 9.6 per cleistogamous pods, which was remarkably less than the average of 38.2 for albida and chaerophylloides, but the germination rate was all similar. The leaf type of self-crossed 2nd offsprings (= F₂, from below) showed all leaf types found in the Viola albida complex, but the ratio of chaerophylloides leaf type was relatively low. Individuals whose F₂ leaf type was restored to albida produced an average of 31.4 seeds per capsule, meaning that fertility was restored. On the other hand, individuals of F₂ takahashii leaf type come to fruition a low average of 10.4 seeds per capsule, which is similar to that of takahashii. The results of crossbreeding experiment, where is their native habitats, were similar to that of laboratory. Both albida and chaerophylloids in Mt. Bulmyeong distribute extensively, but takahashii make a small population only in places where albida and chaerophylloides grow together. Summarizing the above results is suggesting that the speciation of takahashii was done by hybrid between albida and chaerophylloides, and these have been maintained with relatively small population by cleistogamous capsules.

• 한국해양학회지:바다
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• 제19권2호
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• pp.155-163
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• 2014

마산만 표층퇴적물에서 미량금속의 오염도 및 잠재적 생태계 위해도를 평가하기 위하여 미량금속(Cu, Pb, Zn, Cd, Ni)의 총 농도 및 화학적 존재형태를 분석하였다. 미량금속의 농도는 Ni을 제외한 모든 금속이 만의 내측에 위치한 마산항 주변에서 높게 나타났다. 미량금속의 화학적 존재형태 중 Cd과 Pb은 비잔류 부분이 각각 92%, 88%로 인위적 기원에 의해서 주로 공급되는 것으로 나타난 반면, Ni은 잔류 부분이 70%로 주로 자연적 기원에 의해서 공급된 것으로 나타났다. 미량금속의 오염도 및 생태계 위해도를 다양한 지수로 평가한 결과, pollution load index (PLI)는 만의 바깥쪽 정점을 제외한 모든 정점에서 1을 초과하여 인위적 오염 상태를 보였다. Ecological risk index (ERI)는 만의 내측에서 considerable 또는 moderate risk 수준이었으며, 만의 바깥쪽에서는 low risk 수준이었다. Cd의 ecological index (Ei) 값은 대부분의 정점에서 높게 나타났으며, Cd이 산가용성 부분에서 가장 높은 농도를 보여 Cd이 마산만에서 저서생물에게 잠재적으로 높은 위해도를 미칠 것으로 판단된다.