Characteristics of biomass burning aerosol and its impact on regional air quality in the summer of 2003 at Gwangju, Korea   总被引：1，自引：0，他引：1  

S.Y. Ryu  B.G. Kwon  Y.J. Kim  H.H. Kim  K.J. Chun 《Atmospheric Research》2007,84(4):362-373

The main objective of this study is to investigate the chemical characteristics of biomass burning aerosol and its impact on regional air quality during an agricultural waste burning period in early summer in the rural areas of Korea. A 12-h integrated intensive sampling of biomass burning aerosol in the fine and coarse modes was conducted on 2–20 June 2003 in Gwangju, Korea. The collected samples were analyzed for concentrations of mass, ionic, elemental, and carbonaceous species. Average concentrations of fine and coarse mass were measured to be 67.9 and 18.7 μg m^− 3 during the biomass burning period, 41.9 and 18.8 μg m^− 3 during the haze period, and 35.6 and 13.3 μg m^− 3 during the normal period, respectively. An exceptionally high PM_2.5 concentration of 110.3 μg m^− 3 with a PM_2.5/PM₁₀ ratio of 0.79 was observed on 6 June 2003 during the biomass burning period. The potassium ratio method was used to identify biomass burning samples. The average ratio of potassium in the fine mode to the coarse mode (FK/CK) was 23.8 during the biomass burning period, 6.0 during the haze period, and 4.7 during the normal period, respectively. A FK/CK ratio above 9.2 was considered a criterion for biomass burning event in this study. Particulate matter from the open field burning of agricultural waste has an adverse impact on visibility, human health, and regional air quality.  相似文献   

SHRIMP U–Pb zircon ages of pyroclastic rocks in the Bansong Group, Taebaeksan Basin, South Korea and their implication for the Mesozoic tectonics     

Raehee Han  Jin-Han Ree  Deung-Lyong Cho  Sung-Tack Kwon  Richard Armstrong 《Gondwana Research》2006,9(1-2):106

The Bansong Group (Daedong Supergroup) in the Korean peninsula has long been considered to be an important time marker for two well-known orogenies, in that it was deposited after the Songnim orogeny (Permian–Triassic collision of the North and South China blocks) but was deformed during the Early to Middle Jurassic Daebo tectonic event. Here we present a new interpretation on the origin of the Bansong Group and associated faults on the basis of structural and geochronological data. SHRIMP (Sensitive High-Resolution Ion MicroProbe) U–Pb zircon age determination of two felsic pyroclastic rocks from the Bansong Group formed in the foreland basin of the Gongsuweon thrust in the Taebaeksan Basin yielded ages of 186.3 ± 1.5 and 187.2 ± 1.5 Ma, respectively, indicating the deposition of the Bansong Group during the late Early Jurassic. Inherited zircon component indicates ca. 1.9 Ga source material for the volcanic rocks, agreeing with known basement ages.The Bansong Group represents syntectonic sedimentation during the late Early Jurassic in a compressional regime. During the Daebo tectonic event, the northeast-trending regional folds and thrusts including the Deokpori (Gakdong) and Gongsuweon thrusts with a southeast vergence developed in the Taebaeksan Basin. This is ascribed to deformation in a continental-arc setting due to the northwesterly orthogonal convergence of the Izanagi plate on the Asiatic margin, which occurred immediately after the juxtaposition of the Taebaeksan Basin against the Okcheon Basin in the late stage of the Songnim orogeny. Thus, the Deokpori thrust is not a continental transform fault between the North and South China blocks, but an “intracontinental” thrust that developed after their juxtaposition.  相似文献   

Interactions of biopolymers with silica surfaces: Force measurements and electronic structure calculation studies     

Kideok D. Kwon  Virginia Vadillo-Rodriguez  James D. Kubicki 《Geochimica et cosmochimica acta》2006,70(15):3803-3819

Pull-off forces were measured between a silica colloid attached to an atomic force microscope (AFM) cantilever and three homopolymer surfaces representing constituents of extracellular polymeric substances (EPS). The pull-off forces were −0.84 (±0.16), −0.68 (±0.15), and −2.37 (±0.31) nN as measured in water for dextran, phosphorylated dextran, and poly-l-lysine, respectively. Molecular orbital and density functional theory methods (DFT) were applied to analyze the measured pull-off forces using dimer clusters representing interactions between the three polymers and silica surfaces. Binding energies for each dimer were calculated with basis set superposition error (BSSE) and interpolated using corrections for silica surface hydroxyl density and silica charge density. The binding energies were compared with the normalized pull-off forces with the effective silica surface area contacting the polymer surfaces. The predicted binding energies at a −0.064 C/m² silica surface charge density corresponding to circum-neutral pH were −0.055, −0.029, and −0.338 × 10⁻¹⁸ J/nm² for the dimers corresponding to the silica surface with dextran, phosphorylated dextran, and poly-l-lysine, respectively. Polarizable continuum model (PCM) calculations with different solvents, silanol vibrational frequency calculations, and orbital interaction analysis based on natural bonding orbital (NBO) showed that phosphate groups formed stronger H-bonds with neutral silanols than hydroxyl and amino functional groups of polymers, implying that phosphate containing polymers would play important roles in EPS binding to silica surfaces.  相似文献   

Statistical Methods for Jointly Estimating the Decay Constant of ⁴⁰K and the Age of a Dating Standard     

Jaimyoung Kwon  Kyoungwon Min  Peter J. Bickel  Paul R. Renne 《Mathematical Geology》2002,34(4):457-474

To simultaneously evaluate the decay constant of ⁴⁰K () and the age of a standard (t _std) using isotopic data from geologic materials, we applied a series of statistical methods. The problem of estimating the most probable intercept of many nonlinear curves in and t _std space is formulated by an errors-in-variables nonlinear regression model. Then a maximum likelihood method is applied to the model for a point estimate, which is equivalent to the nonlinear least square method when measurement error distributions are Gaussian. Uncertainties and confidence regions of the estimates can be approximated using three methods: the asymptotic normal approximation, the parametric bootstrap method and Bonferroni confidence regions. Five pairs of published data for samples with ages from 2 ka to 4.5 Ga were used to estimate and the age of Fish Canyon sanidine (t _FCs). The statistical procedure yields most probable estimates of (5.4755 ± 0.0170 × 10^–10 (1)/year) and t _FCs (28.269 ± 0.0661 (1) Ma) which are in between previously published values. These results indicate the power of our approach to provide improved constraints on these parameters, although the preliminary nature of some of the input data require further review before the values can be adopted.  相似文献   

Origin and depositional environment of fine-grained sediments since the last glacial maximum in the southeastern Yellow Sea: evidence from rare earth elements     

In Kwon Um  Man Sik Choi  Gwang Soo Lee  Tae Soo Chang 《Geo-Marine Letters》2015,35(6):421-431

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Unexpected nationwide nitrate declines in groundwater of Korea          下载免费PDF全文

Jin‐Yong Lee  Kideok D. Kwon  Yu‐Chul Park  Woo‐Hyun Jeon 《水文研究》2017,31(26):4693-4704

Elevated levels of nitrate in groundwater are an important concern for health and the environment. The overapplication of nitrogen fertilizer to croplands is one of the major sources of high nitrate content in groundwater. In this study, we analyse the nitrate concentrations in Korean groundwater based on data from groundwater quality monitoring wells (n = 1,022–2,072), which were sampled twice annually over a recent 13‐year analysis period (2001–2013). We report that groundwater nitrate levels are decreasing, despite steadily increasing groundwater use. The maximum nitrate concentration decreased from 168.91 to 48.11 mg/L, whereas the mean values also show a gradual decreasing trend. Non‐parametric Mann–Kendall tests on nitrate concentrations also confirm the decreasing trend. The nitrate decrease is more clearly evident in agricultural groundwater as compared to domestic and drinking groundwaters. This decrease of nitrate in groundwater coincides with a large decline in nitrogen fertilizer application due to reduced cropland areas, more sustainable agricultural practices, and progressive improvement of sewage disposal services. This study proposes that the long‐term adoption of best practices in agriculture has had a positive impact on groundwater nitrate control.  相似文献   

Identification of groundwater recharge sources and processes in a heterogeneous alluvial aquifer: results from multi‐level monitoring of hydrochemistry and environmental isotopes in a riverside agricultural area in Korea     

Byoung‐Young Choi  Seong‐Taek Yun  Bernhard Mayer  Gi‐Tak Chae  Kyoung‐Ho Kim  Kangjoo Kim  Yong‐Kwon Koh 《水文研究》2010,24(3):317-330

We evaluated sources and pathways of groundwater recharge for a heterogeneous alluvial aquifer beneath an agricultural field, based on multi‐level monitoring of hydrochemistry and environmental isotopes of a riverside groundwater system at Buyeo, Korea. Two distinct groundwater zones were identified with depth: (1) a shallow oxic groundwater zone, characterized by elevated concentrations of NO₃^? and (2) a deeper (>10–14 m from the ground surface) sub‐oxic groundwater zone with high concentrations of dissolved Fe, silica, and HCO₃^?, but little nitrate. The change of redox zones occurred at a depth where the aquifer sediments change from an upper sandy stratum to a silty stratum with mud caps. The δ¹⁸O and δ²H values of groundwater were also different between the two zones. Hydrochemical and δ¹⁸O? δ²H data of oxic groundwater are similar to those of soil water. This illustrates that recharge of oxic groundwater mainly occurs through direct infiltration of rain and irrigation water in the sandy soil area where vegetable cropping with abundant fertilizer use is predominant. Oxic groundwater is therefore severely contaminated by agrochemical pollutants such as nitrate. In contrast, deeper sub‐oxic groundwater contains only small amounts of dissolved oxygen (DO) and NO₃^?. The ³H contents and elevated silica concentrations in sub‐oxic groundwater indicate a somewhat longer mean residence time of groundwater within this part of the aquifer. Sub‐oxic groundwater was also characterized by higher δ¹⁸O and δ²H values and lower d‐excess values, indicating significant evaporation during recharge. We suggest that recharge of sub‐oxic groundwater occurs in the areas of paddy rice fields where standing irrigation and rain water are affected by strong evaporation, and that reducing conditions develop during subsequent sub‐surface infiltration. This study illustrates the existence of two groundwater bodies with different recharge processes within an alluvial aquifer. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Uncertainty analysis for the integration of seismic and controlled source electro‐magnetic data     

Myoung Jae Kwon  Roel Snieder 《Geophysical Prospecting》2011,59(4):609-626

We study the appraisal problem for the joint inversion of seismic and controlled source electro‐magnetic (CSEM) data and utilize rock‐physics models to integrate these two disparate data sets. The appraisal problem is solved by adopting a Bayesian model and we incorporate four representative sources of uncertainty. These are uncertainties in 1) seismic wave velocity, 2) electric conductivity, 3) seismic data and 4) CSEM data. The uncertainties in porosity and water saturation are quantified by a posterior random sampling in the model space of porosity and water saturation in a marine one‐dimensional structure. We study the relative contributions from the four individual sources of uncertainty by performing several statistical experiments. The uncertainties in the seismic wave velocity and electric conductivity play a more significant role on the variation of posterior uncertainty than do the seismic and CSEM data noise. The numerical simulations also show that the uncertainty in porosity is most affected by the uncertainty in the seismic wave velocity and that the uncertainty in water saturation is most influenced by the uncertainty in electric conductivity. The framework of the uncertainty analysis presented in this study can be utilized to effectively reduce the uncertainty of the porosity and water saturation derived from the integration of seismic and CSEM data.  相似文献   

Geotectonic framework of Permo–Triassic magmatism within the Korean Peninsula     

Sung Won Kim  Sanghoon Kwon  Hee Jae Koh  Keewook Yi  Youn-Joong Jeong  M. Santosh 《Gondwana Research》2011,20(4):865-889

This study presents sensitive high-resolution ion microprobe (SHRIMP) U–Pb zircon ages, and whole-rock chemical and isotopic (Sr-Nd) compositions of representative Triassic plutons from South Korea. The plutons from the Gyeonggi massif (Hongseong, Namyang, Yangpyeong and Odesan), the central Okcheon belt (Baeknok and Yongsan), and the Yeongnam massif (Sangju, Gimcheon, Hamyang and Macheon) yield zircon U–Pb ages of ca. 232–226 Ma, 227–226 Ma, and 240–228 Ma, respectively. Among the Triassic plutonic suite in South Korea, those within the Gyeonggi massif are dominated by granite, syenite, monzonite, monzodiorite and gabbro. Plutons within the Okcheon belt are mainly by granite to quartz monzodiorite. The Yeongnam massif mainly incorporates granite to granodiorite and minor monzodiorite intrusions. The geochemical signatures of the Triassic plutons are characterized by Ta–Nb troughs, depletion of P and Ti, and enrichment of LILE. Most plutons except Macheon monzodioritic pluton show high initial ⁸⁷Sr/⁸⁶Sr ratios (0.708248–0.714678) and strongly negative ε_Nd(T) (− 20.3 to − 7.7) values, suggesting contribution from middle to upper crust. In contrast, the Macheon monzodioritic pluton in the Yeongnam massif shows relatively low initial ⁸⁷Sr/⁸⁶Sr ratios (0.706547-0.706629) and negative ε_Nd(T) (− 4.43 to − 3.62) values. The Middle Triassic syenite–monzonite–granite–gabbro series in and around the Gyeonggi massif possess high-K calc-alkaline and shoshonitic affinity suggesting a post-collisional magmatic event following the Permo–Triassic collision between the North and South China blocks. The Triassic plutons in the Yeongnam massif and the Okcheon belt, together with a Permian Yeongdeok pluton in the Gyeongsang basin, show features typical of high- to medium-K calc-alkaline magmatism with LREE and LILE enrichments. This together with a depletion of Y and HREE suggests their formation in a subduction setting. Our results provide robust evidence to consider the Gyeonggi massif as an extension of the Qinling–Dabie–Sulu belt between the North and South China blocks in central China. The Okcheon belt and Yeongnam massif in South Korea, together with the continental margin of South China, are marked by a common Permian to Triassic magmatic episode, probably related to the paleo-Pacific slab subduction.  相似文献   

Geotechnical properties of deep oceanic sediments recovered from the hydrate occurrence regions in the Ulleung Basin, East Sea, offshore Korea   总被引：1，自引：0，他引：1  

Tae-Hyuk Kwon  Kang-Ryel Lee  Gye-Chun Cho  Joo Yong Lee 《Marine and Petroleum Geology》2011,28(10):1870-1883

This study presents comprehensive geotechnical data of the natural marine sediments cored from the hydrate occurrence regions during the Ulleung Basin Gas Hydrate Expedition 1 (UBGH1), East Sea, offshore Korea in 2007. Geotechnical soil index properties of the Ulleung Basin sediments, including grain size distribution, porosity, water content, Atterberg limits, specific gravity, and specific surface area, were experimentally determined. These soil index properties were correlated to geotechnical engineering parameters (e.g., shear strength and friction angle) by using well-known empirical relationships. By performing standard consolidation tests on both undisturbed specimens (as recovered from the original core liner after hydrate dissociation) and remolded specimens, stress-dependent mechanical and hydraulic properties (e.g., compressibility and hydraulic conductivity) were measured. The experimental results provide important engineering parameters, and demonstrate the effect of hydrate presence and consequential dissociation to index properties, engineering parameters, and innate sediment structures.  相似文献