• Title/Summary/Keyword: POM-C

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Influence of Drying Temperature and Duration on the Quantification of Particulate Organic Matter

  • Lee, Jin-Ho;Doolittle, James J.;Lee, Do-Kyoung;Malo, Douglas D.
    • Korean Journal of Environmental Agriculture
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    • v.25 no.4
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    • pp.289-296
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    • 2006
  • Various drying conditions, temperatures (40 to $80^{\circ}C$) and durations (overnight to 72 hrs), for the particulate organic matter (POM) fraction after wet-sieving size fractionation have been applied for determination of POM contents in the weight loss-on-ignition method. In this study, we investigated the optimum drying condition for POM fraction in quantification of POM and/or mineral-associated organic matter (MOM; usually indirectly estimated). The influence of the drying conditions on quantifying POM was dependent upon soil properties, especially the amount of soil organic components. In relatively high organic soils (total carbon > 40 g/kg in this study), the POM values were significantly higher (overestimated) with drying at $55^{\circ}C$ than those values at $105^{\circ}C$, which were, for example, 173.2 and 137.3 mg/kg, respectively, in a soil studied. However, drying at $55^{\circ}C$ for longer than 48 hrs of periods produced consistent POM values even though the values were much higher than those at $105^{\circ}C$. Thus, indirect estimates of MOM (MOM = SOM-POM) also tended to be significantly impacted by the dry conditions. Therefore, we suggest POM fractions should be dried at $105^{\circ}C$ for 24 hrs as determining POM and MOM contents. If the POM traction is needed to be dried at a lower temperature (e.g. $55^{\circ}C$) with a specific reason, at least 48 hrs of drying period is necessary to obtain consistent POM values, and a moisture correction factor should be determined to adjust the values back to a $105^{\circ}C$ weight basis.

Orientation Control of Polyoxometalate Nanoparticles in Organic- Inorganic Hybrid LB Films

  • Lee, Burm-Jong;Kim, Hee-Sang;Park, Dong-Ho;Nam, Sang-Hee;Yunghee Oh
    • KIEE International Transactions on Electrophysics and Applications
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    • v.4C no.1
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    • pp.26-30
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    • 2004
  • Orientation control of a polyoxometalate (POM) nanoparticle in its two-dimensional arrangement was attempted by Langmuir-Blodgett (LB) technique. For their uniorientation, two carboxyl groups were introduced on one side of the POM particle, and hydrophobic long chains were attached by esterification with the carboxyl groups (C18-POM). The C18-POM layer spread on water surface showed stability against surface pressure up to 60 mN/m. The pattern of the C18-POM isotherm was quite different from stearyl alcohol (C18-OH), while the POM itself did not show any development of surface pressure on water surface. The AFM images of C18-POM LB films showed some microcrystalline structures that were noticed as dot structures by Brewster angle microscopy. The microimages for C18-POM did not completely spread out as a monolayer on the water surface. The XPS spectra indicated the presence of POM structures and stearyl ester bonds formed from about 65% of the total carboxyls. The XRD spectra showed that the unioriented POMs were not positioned with the same lattice distance but rather in a wavy surface state.

Effects of Electron Beam Irradiation on Tribological and Physico-chemical Properties of Polyoxymethylene (POM-C) copolymer

  • Rahman, Md. Shahinur;Yang, Jong-Keun;Shaislamov, Ulugbek;Lyakhov, Konstantin;Kim, Min-Seok;Lee, Heon-Ju
    • Proceedings of the Korean Vacuum Society Conference
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    • 2016.02a
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    • pp.153-153
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    • 2016
  • Polyoxymethylene copolymer (POM-C) is an attractive and widely used engineering thermoplastic across many industrial sectors owing to outstanding physical, mechanical, self-lubricating and chemical properties. In this research work, the POM-C blocks were irradiated with 1 MeV electron beam energy in five doses (100, 200, 300, 500 and 700 KGy) in vacuum condition at room temperature. The tribological and physico-chemical properties of electron beam irradiated POM-C blocks have been analyzed using Pin on disk tribometer, Raman spectroscopy, SEM-EDS, Optical microscopy, 3D Nano surface profiler system and Contact angle analyzer. Electron beam irradiation at a dose of 100 kGy resulted in a decrease of the friction coefficient and wear loss of POM-C block due to well suited cross-linking, carbonization, free radicals formation and energetic electrons-atoms collisions (physical interaction). It also shows lowest surface roughness and highest water contact angle among all unirradiated and irradiated POM-C blocks. The irradiation doses at 200, 300, 500 and 700 kGy resulted in increase of the friction coefficient as compared to unirradiated POM-C block due to severe chain scission, chemical and physical structural degradation. The electron beam irradiation transferred the wear of unirradiated POM-C block from the abrasive wear, adhesive wear and scraping to mild scraping for the 1 MeV, 100 kGy irradiated POM-C block which is concluded from SEM-EDS and Optical microscopic observations. The degree of improvement for tribological attribute relies on the electron beam irradiation condition (energy and dose rate).

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Annual Change and C:N:P ratio in Particulate Organic Matter in Chinhae Bay, Korea (한국진해만 입자유기물 함량과 C:N:P 비의 연변화)

  • LEE, PIL-YONG;KANG, CHANG-KEUN;PARK, JONG-SOO;PARK, JOO-SUCK
    • 한국해양학회지
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    • v.29 no.2
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    • pp.107-118
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    • 1994
  • An investigation of the annual change and C:N:P ratio in particulate organic matter (POM) in Chinhae Bay, a semi-enclosed bay of the southern coast of Korean Peninsula, was carried out for a period of 12 months between January and December, 1993. The concentrations of POM have a broad range: 198∼4,416 ugC/l, 24∼792 ugN/l and 4.5∼69.0 ugP/l, Marked seasonal changes of POM, particularly particulate organic carbon (POC) and nitrogen (PON), were observed in the surface water. Generally, the concentration of POM peaks in summer. The C:N:P composition ratio of particulate organic matter, which is high in summer, also shows a seasonal change. The C:N assimilation ratio is constant at 6.53, which is consistent with the Redfield ratio. The significant linear relationship between POM and chlorophyll-a in the surface water during the survey period (except for January and February) and the C:N ratio suggest that the concentration of POM is controlled by phytoplankton biomass. POM peaks in summer, a period characterized by high freshwater input and the strong stratification, as a result of the intense proliferation of phytoplankton by a large amount of nutrient loading from the tributaries. On the other hand, the high C:P and N:P ratios in summer indicate that P is limited for phytoplankton growth owing to N-enrichment from a high input of freshwater with a high dissolved inorganic N:P ratio.

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The Distribution of DOM and POM and the Composition of Stable Carbon Isotopes in Streams of Agricultural and Forest Watershed Located in the Han River System (한강수계 농경지역 하천과 삼림지역 하천에서 DOM과 POM의 분포 및 안정탄소동위원소 조성비)

  • Kim, Jai-Ku;Kim, Bom-Chul;Jung, Sung-Min;Jang, Chang-Won;Shin, Myoung-Sun;Lee, Yun-Kyoung
    • Korean Journal of Ecology and Environment
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    • v.40 no.1
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    • pp.93-102
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    • 2007
  • The runoff characteristics of organic matter in turbid water were investigated in eleven tributary streams of the Han River system, Korea. The flow-weighted event mean concentrations of organic matter ranged from 1.5 to 3.2 mg $L^{-1}$ of DOM and 2.2 of 29.1 mg $L^{-1}$ of POM, respectively. The SUVA value which reflects the proportion of humic substance in organic matters was higher during the rainfall season, meaning that the runoff of refractory form increase in this period. Stable carbon isotope ratios of both POM and DOM were different among streams, which reflect the sources of organic matter. DOM isotope ratios were less depleted of $^{13}C$ than that of POM by approximately 1 to $2%_{\circ}$ ${\delta}^{13}C$ of the several turbid streams (the Mandae Stream, the Jawoon Stream, and the Daegi stream) were heavier than those of clear streams. ${\delta}^{13}C$ values in the turbid upstream tributaries were similar to those of downstream reaches (such as the Soyang River, the Sum River, and the Seo River). From the ${\delta}^{13}C$ analysis of POM it could be calculated that $C_4$ pathway contributed approximately 15.9 to 23.6% of organic matter in several turbid upstream sites, and over 20% in the three sites of large downstream reaches. On the contrary it contributed only 9.1 to 12.8% in clear streams of forest watersheds. In the Soyang River, $C_4$ pathway organic matter contributed 8.8% of the DOM pool.

Stable carbon isotope signatures of zooplankton in some reservoirs in Korea

  • Lee, Jeayong;Lee, Yunkyoung;Jang, Changwon;Owen, Jeffrey S.;Kim, Jai-Ku;Eum, Jaesung;Jung, Sungmin;Kim, Bomchul
    • Journal of Ecology and Environment
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    • v.36 no.3
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    • pp.183-191
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    • 2013
  • Dissolved organic carbon (DOC) concentrations and zooplankton and particulate organic matter (POM) ${\delta}^{13}C$ values were measured in five reservoirs in Korea. Zooplankton ${\delta}^{13}C$ and POM ${\delta}^{13}C$ showed large range from -33‰ to -22‰ and a significant difference among the reservoirs. One eutrophic reservoir, Lake Masan, showed unique characteristics with the highest zooplankton density, the highest ${\delta}^{13}C$, and the highest DOC. Zooplankton ${\delta}^{13}C$ was similar to POM ${\delta}^{13}C$, implying that zooplankton occupies substantial portion of POM or that zooplankton isotopic composition is related to selective grazing and assimilation of food sources from bulk POM. Except Lake Masan zooplankton ${\delta}^{13}C$ values were negatively correlated to DOC concentration in four reservoirs with mostly forest land use. This pattern can be probably attributed to intensive agricultural land use in the watershed of Lake Masan compared to the mostly forest land use in the other watersheds. Understanding the relationship between zooplankton ${\delta}^{13}C$ values and the origin of organic matter associated with watershed characteristics will be valuable to better understand trophic relationships in reservoirs in the summer monsoon region.

C:N:P stoichiometry of particulate and dissolved organic matter in river waters and changes during decomposition

  • Islam, Mohammad Jahidul;Jang, Changwon;Eum, Jaesung;Jung, Sung-min;Shin, Myoung-Sun;Lee, Yunkyoung;Choi, Youngsoon;Kim, Bomchul
    • Journal of Ecology and Environment
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    • v.43 no.1
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    • pp.14-21
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    • 2019
  • Background: Stoichiometry plays an important role in understanding nutrient composition and cycling processes in aquatic ecosystems. Previous studies have considered C:N:P ratios constant for both DOM (dissolved organic matter) and POM (particulate organic matter). In this study, water samples were collected in the six major rivers in Korea and were incubated for 20 days. C:N:P ratios were determined during the time course of the incubations. This allowed us to examine the changes in N and P contents of organic matter during decomposition. Results: POM and DOM showed significant differences in N and P content and the elemental ratios changed during the course of decomposition; DOM showed higher C:N and C:P ratios than POM, and the C:N and C:P ratios increased during decomposition, indicating the preferential mineralization of P over N and N over C. Conclusions: The N and P contents of organic matter in aquatic ecosystem are far from constant and vary significantly during decomposition. More detailed information on the changes in C:N:P ratios will provide improved understanding of decomposition processes and improved modeling of aquatic ecosystems.

Removal of reactive black 5 dye by using polyoxometalate-membrane

  • Topaloglu, Ali Kemal;Yildirim, Yilmaz
    • Membrane and Water Treatment
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    • v.12 no.1
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    • pp.23-35
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    • 2021
  • A POM-membrane was fabricated by immobilizing a keggin type polyoxometalate (POM) H5PV2Mo10O40 onto the surface of microporous flat-sheet polymeric polyvinylidene fluoride (PVFD) membrane using a chemical deposition method. The POM-membrane was characterized by FT-IR, SEM and EDX to confirm existing of the POM onto the membrane surface. The POM-membrane was used to remove an anionic textile dye (Reactive Black 5 named as an RB5) from aqueous phases with a cross-flow membrane filtration and a batch adsorption system. The dye removal efficiency of the POM-membrane using the cross-flow membrane filtration system and the batch adsorption system was about 88% and 98%, respectively. The influence factors such as contact time, adsorbent dosage, pH, and initial dye concentration were investigated to understand the adsorption mechanism of the RB5 dye onto the POM-membrane. To find the best fitting isotherm model, Langmuir, Freundlich, BET and Harkins-Jura isotherm models were used to analyze the experimental data. The isotherm analysis showed that the Langmuir isotherm model was found to the best fit for the adsorption data (R2 = 0.9982, qmax = 24.87 mg/g). Also, adsorption kinetic models showed the pseudo second order kinetic model was found the best model to fit the experimental data (R2 = 0.9989, q = 8.29 mg/g, C0 = 15 ppm). Moreover, after four times regeneration with HNO3 acid, the POM-membrane showed high regenerability without losing dye adsorption capacity.

A Study on Vertical Distribution and Origin of Particulate Organic Matter in Shingu Reservoir in Pre-monsoon and Post-monsoon Period - Application of Carbon and Nitrogen Stable Isotope Ratio - (하계 강우기 전.후 신구저수지 내 입자성유기물의 수직분포 및 기원 연구 - 탄소 및 질소 안정동위원소비의 활용 -)

  • Kim, Min-Seob;Lee, Yeon-Jung;Shin, Kyung-Hoon;Hwang, Soon-Jin
    • Korean Journal of Ecology and Environment
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    • v.41 no.spc
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    • pp.27-34
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    • 2008
  • The vertical distribution and origin of particulate organic matter (POM) were investigated in Shingu reservoir on 4th July (pre-monsoon) and 7th August (post-monsoon) 2006. High turbid water (120 NTU) were found at 4.5 m water depth in postmonsoon period. The average C/N ratio of POM was about 5.70 and 6.96 in surface water and bottom water, respectively in pre-monsoon period, exhibiting the close values to its ratio in phytoplankton cell. However, the average C/N ratio was 7.10 in surface water and 12.81 in bottom water in post-monsoon period. In addition, the ${\delta}^{13}C$ values of POM in pre-monsoon period ranged from -25.1%o to -26.1%o in whole water column, but the ${\delta}^{13}C$ values of POM in post-monsoon period showed relatively wide range between -23.2%o and -27.5%o. The apparently lighter values (average -27.5%o) in near bottom water (4.5 m water depth) demonstrate that POM in high turbid water in post-monsoon period may be derived from the outside terrestrial plants through heavy rainfall during the summer monsoon period. The present study suggests that carbon and nitrogen stable isotope ratios as well as C/N ratios should be useful indexes to clarify the origin of POM.