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RISS 인기검색어
- 검색키워드
- 저자 : Jeffrey S Owen (검색결과 30 건)
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Stable Nitrogen Isotopes in a Forested Watershed in Taiwan
Owen, Jeffrey S. Institute of Forest Science 2013 Journal of Forest Science Vol.29 No.2
Differences in rates and patterns of nitrogen cycling have been correlated with nitrogen stable isotope measurements in forest ecosystems of tropical and temperate regions, but limited similar work has been conducted in sub-tropical forests. This study investigated patterns in stable N isotopic composition in a subtropical forest in Taiwan by sampling three soil profiles and overstory and understory foliage. Soil ${\delta}^{15}N$ in the forest floor ranged from -1.8 to -1.8‰. Mineral soils had higher ${\delta}^{15}N$ (4.1 to 6.0‰). Foliage ${\delta}^{15}N$ in overstory trees ranged from -6.6 to -2.0‰, and understory foliage ${\delta}^{15}N$ ranged from -5.0 to -1.2‰. There was a weak correlation between foliar % N and ${\delta}^{15}N$ ($r^2=0.214$). Compared to results from similar surveys in tropical and temperate forests, foliar ${\delta}^{15}N$ values were generally lower. These results help highlight the need for improved knowledge regarding the relationships between patterns in N stable isotopes and processes affecting rates of N cycling, especially as related to wider scale patterns in forest ecosystems within the east-Asia region.
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Owen, Jeffrey S.,Pyo, Sunyeon,Kang, Guyoung Korean Society of Soil and Groundwater Environment 2015 지하수토양환경 Vol.20 No.5
Biocatalytic degradation of total petroleum hydrocarbons (TPHs) in contaminated soil by hemoglobin and hydrogen peroxide is an effective soil remediation method. This study used a laboratory soil reactor experiment to evaluate the effectiveness of a nonspecific biocatalytic reaction with hemoglobin and H<sub>2</sub>O<sub>2</sub> for treating TPH-contaminated soil. We also quantified changes in the soil microbial community using real-time PCR analysis during the experimental treatment. The results show that the measured rate constant for the reaction with added hemoglobin was 0.051/day, about 3.5 times higher than the constant for the reaction with only H<sub>2</sub>O<sub>2</sub> (0.014/day). After four weeks of treatment, 76% of the initial soil TPH concentration was removed with hemoglobin and hydrogen peroxide treatment. The removal of initial soil TPH concentration was 26% when only hydrogen peroxide was used. The soil microbial community, based on 16S rRNA gene copy number, was higher (7.1 × 10<sup>6</sup> copy number/g of bacteria, and 7.4 × 10<sup>5</sup> copy number/g of Archaea, respectively) in the hemoglobin catalyzed treatment. Our results show that TPH treatment in contaminated soil using hemoglobin catalyzed oxidation led to the enhanced removal effectiveness and was non-toxic to the native soil microbial community in the initial soil.
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Stable Nitrogen Isotopes in a Forested Watershed in Taiwan
Jeffrey S. Owen 강원대학교 산림과학연구소 2013 Journal of Forest Science Vol.29 No.2
Differences in rates and patterns of nitrogen cycling have been correlated with nitrogen stable isotope measurements in forest ecosystems of tropical and temperate regions, but limited similar work has been conducted in sub-tropical forests. This study investigated patterns in stable N isotopic composition in a subtropical forest in Taiwan by sampling three soil profiles and overstory and understory foliage. Soil δ15N in the forest floor ranged from - 1.8 to 1.8‰. Mineral soils had higher δ15N (4.1 to 6.0‰). Foliage δ15N in overstory trees ranged from -6.6 to -2.0‰, and understory foliage δ15N ranged from -5.0 to -1.2‰. There was a weak correlation between foliar % N and δ15N (r2=0.214). Compared to results from similar surveys in tropical and temperate forests, foliar δ15N values were generally lower. These results help highlight the need for improved knowledge regarding the relationships between patterns in N stable isotopes and processes affecting rates of N cycling, especially as related to wider scale patterns in forest ecosystems within the east-Asia region.
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Jeffrey S. Owen,표선연,강구영 한국지하수토양환경학회 2015 지하수토양환경 Vol.20 No.5
Biocatalytic degradation of total petroleum hydrocarbons (TPHs) in contaminated soil by hemoglobin and hydrogen peroxide is an effective soil remediation method. This study used a laboratory soil reactor experiment to evaluate the effectiveness of a nonspecific biocatalytic reaction with hemoglobin and H2O2 for treating TPH-contaminated soil. We also quantified changes in the soil microbial community using real-time PCR analysis during the experimental treatment. The results show that the measured rate constant for the reaction with added hemoglobin was 0.051/day, about 3.5 times higher than the constant for the reaction with only H2O2 (0.014/day). After four weeks of treatment, 76% of the initial soil TPH concentration was removed with hemoglobin and hydrogen peroxide treatment. The removal of initial soil TPH concentration was 26% when only hydrogen peroxide was used. The soil microbial community, based on 16S rRNA gene copy number, was higher (7.1 × 106 copy number/g of bacteria, and 7.4 × 105 copy number/g of Archaea, respectively) in the hemoglobin catalyzed treatment. Our results show that TPH treatment in contaminated soil using hemoglobin catalyzed oxidation led to the enhanced removal effectiveness and was non-toxic to the native soil microbial community in the initial soil.
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Patterns in solute chemistry of six inlet streams to Lake Hövsgöl, Mongolia
Puntsag, Tamir,Owen, Jeffrey S.,Mitchell, Myron J.,Goulden, Clyde E.,McHale, Patrick J. The Ecological Society of Korea 2010 Journal of Ecology and Environment Vol.33 No.4
A number of characteristics of the Lake H$\ddot{o}$vsg$\ddot{o}$l watershed, such as the lake's location at the edge of the Central Asian continuous permafrost zone, provide a unique opportunity to evaluate possible anthropogenic impacts in this remote area in northern Mongolia. In this study, we compared stream solute concentrations in six sub-watersheds in the Lake H$\ddot{o}$vsg$\ddot{o}$l watershed. Water samples were collected during the summer months between 2003 and 2005. Concentrations of $Cl^-$ ranged from 9.8 to $51.3\;{\mu}mol/L$; average nitrate concentrations were very low and ranged from undetectable to $1.1\;{\mu}mol/L$ and average ${SO_4}^{2-}$ concentration at sampling stations with minimal animal grazing ranged from 66 to $294\;{\mu}mol/L$. Average dissolved organic carbon (DOC) concentrations ranged from 642 to $1,180\;{\mu}mol$ C/L. We did not find statistically significant differences in DOC concentrations among the six streams, although DOC concentrations tended to be higher in the two northernmost streams, possibly related to differences in the active layer above the permafrost. Dissolved organic nitrogen (DON) concentrations were correlated with DOC concentration, and followed the same spatial pattern as those for DOC. In streams in this remote watershed, total dissolved nitrogen was made up of mostly organic N, as has been found for other regions distant from anthropogenic N sources. Overall, these results suggest that future research on the dynamics of DOC and DON in this watershed will be especially insightful in helping to understand how changes in climate and land use patterns will affect transformations, retention, and export of dissolved organic matter within these sub-watersheds in the Lake H$\ddot{o}$vsg$\ddot{o}$l region.
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Patterns in solute chemistry of six inlet streams to Lake Hövsgöl, Mongolia
Tamir Puntsag,Jeffrey S. Owen,Myron J. Mitchell,Clyde E. Goulden,Patrick J. McHale 한국생태학회 2010 Journal of Ecology and Environment Vol.33 No.4
A number of characteristics of the Lake Hövsgöl watershed, such as the lake’s location at the edge of the Central Asian continuous permafrost zone, provide a unique opportunity to evaluate possible anthropogenic impacts in this remote area in northern Mongolia. In this study, we compared stream solute concentrations in six sub-watersheds in the Lake Hövsgöl watershed. Water samples were collected during the summer months between 2003 and 2005. Concentrations of Cl⁻ ranged from 9.8 to 51.3 μmol/L; average nitrate concentrations were very low and ranged from undetectable to 1.1 μmol/L and average SO₄²⁻ concentration at sampling stations with minimal animal grazing ranged from 66 to 294μmol/L. Average dissolved organic carbon (DOC) concentrations ranged from 642 to 1,180 μmol C/L. We did not find statistically significant differences in DOC concentrations among the six streams, although DOC concentrations tended to be higher in the two northernmost streams, possibly related to differences in the active layer above the permafrost. Dissolved organic nitrogen (DON) concentrations were correlated with DOC concentration, and followed the same spatial pattern as those for DOC. In streams in this remote watershed, total dissolved nitrogen was made up of mostly organic N, as has been found for other regions distant from anthropogenic N sources. Overall, these results suggest that future research on the dynamics of DOC and DON in this watershed will be especially insightful in helping to understand how changes in climate and land use patterns will affect transformations, retention, and export of dissolved organic matter within these sub-watersheds in the Lake Hövsgöl region.
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