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   

Effect of NAPL exposure on the wettability and two‐phase flow in a single rock fracture          下载免费PDF全文

Hang Bok Lee  Byung‐Woo Kim 《水文研究》2015,29(23):4919-4931

Surface‐wetting properties are an important cause of changing the groundwater and two‐phase fluid flows. Various factors affecting the surface wettability were investigated in a parallel‐walled glass fracture with non‐aqueous phase liquid (NAPL) (gasoline, diesel, trichloroethylene, and creosote) wetted surfaces. First, the effect of the duration of NAPL exposure on wettability change was considered at pre‐wet fracture surfaces using the various NAPL species, and the result showed that the surface became hydrophobic after the exposure time of NAPL exceeded 2000 min. Second, the initial wetting state of the surface affected the timing when the wettability change begins as well as the extent of the wettability change in an NAPL‐wetted rock fractures. Under the dry condition, the wettability change was completed within a very short time of exposure to NAPL (~5 min), and then it finally reached the intermediate and weakly NAPL wetting (contact angle of 118°). Under the pre‐wet condition, a relatively long time of exposure (~5000 min) was needed to observe the obvious change of the surface wettability, which was changed up to strongly NAPL wetting (contact angle of 142°). Third, the wettability changed by NAPL exposure was stable and maintained for a long time, regardless of water flushing rate and temperature. Finally, the wettability change by the exposure of NAPL on parallel fracture surfaces was evaluated at various groundwater flow velocities. Result showed that groundwater flow velocity has an important impact upon measured contact angle. Although fracture surfaces were exposed to NAPL at the low groundwater flow velocity, the wettability was not changed from hydrophilic to hydrophobic when the contact time between NAPL and mineral surfaces was not sufficient owing to the pulse‐type movement of NAPL. This implies that the variation of exposure pattern due to groundwater flow on the wettability change can be an important factor affecting the wettability change of fracture surface and migration behaviour at natural fractured rock aquifers in case of NAPL spill. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Solute dynamics across the stream‐to‐riparian continuum under different flood waves     

Dongsheng Liu  Jian Zhao  Woo‐Hyun Jeon  Jin‐Yong Lee 《水文研究》2019,33(20):2627-2641

To enhance the understanding of solute dynamics within the stream‐to‐riparian continuum during flood event‐driven water fluctuation (i.e., flood wave), a variable saturated groundwater flow and solute transport model were developed and calibrated against in situ measurements of the Inbuk stream, Korea, where seasonal flooding prevails. The solute dynamics were further investigated for flood waves (varying by amplitude [A], duration [T], roundness [r], and skewness [t_p]) that were parameterised by real‐time stream stage fluctuations. We found that the solute transferred faster and farther in the riparian zone, especially within the phreatic zone, above which in the variable saturated zone the concentration required a significantly longer time, particularly at higher altitudes, to return to the initial state. By comparison, solute transferred shallowly in the streambed where the solute plume exhibited an exponential growth trend from the centre to the bank. The dynamic changes of solute flux and mass along the stream–aquifer interface and stream concentration were linked to the shape of flood wave. As the flood wave became higher (A↗), wider (T↗), rounder (r↘), and less skewed (t_p↗), the maximum solute storage in aquifer increased. Maximum stream concentration (C_str?max) not only presented a positive linear relationship with A or t_p but also showed a negative logarithmic trend with increasing T or r. The sensitivity of C_{str_max} to A was approximately two times that of t_p, and between these values, the r was slightly more sensitive than T. C_str?max linearly increased as hydraulic conductivity increased and logarithmically increased as longitudinal dispersivity increased. The former relationship was more sensitive than the latter.  相似文献   

Spatial Landslide Hazard Prediction Using Rainfall Probability and a Logistic Regression Model     

Saro Lee  Joong-Sun Won  Seong Woo Jeon  Inhye Park  Moung Jin Lee 《Mathematical Geosciences》2015,47(5):565-589

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Meteorological responses to Mt. Baekdu volcanic eruption over east asia in an offline global climate-chemistry model: A pilot study     

Byung-Kwon Moon  Daeok Youn  Rokjin J. Park  Sang-Wook Yeh  Won-Mo Kim  Young-Ho Kim  Jaein I. Jeong  Jung-Hun Woo  Eul Gyu Im  Chang-Keun Song 《Asia-Pacific Journal of Atmospheric Sciences》2011,47(4):345-351

We examine the meteorological responses due to the probable eruption of Mt. Baekdu using an off-line Climate-Chemistry model that is composed of the National Center for Atmospheric Research (NCAR) Climate Atmosphere Model version 3 (CAM3) and a global chemistry transport model (GEOS-Chem). Using the aerosol dataset from the GEOS-Chem driven by GEOS-5 meteorology, experiment and control simulations of the climate model are performed and their meteorological differences between the two simulations are analyzed. The magnitudes of volcanic eruption and column injection height were presumably set to 1/200 of the Mt. Pinatubo eruption and 9 km, respectively. Significant temperature drop in the lower troposphere (850 hPa), which is mainly due to a direct effect of prescribed volcanic aerosols from Mt. Baekdu, has been simulated up to about ?4 K. The upper atmosphere (150 hPa) right above the volcano, however, shows significant warming due to the absorption of the infrared radiation by volcanic aerosols. As a result of the volcanic eruption in the climate model, wave-like patterns are shown in both the geopotential height and horizontal wind. The changes in the lower atmospheric temperature are well associated with the modification of the atmospheric circulation through the hydrostatic balance. In spite of limitations in our current simulations due to several underlying assumptions, our results could give a clue to understanding the meteorological impacts from Mt. Baekdu eruptions that are currently attracting considerable public attention.  相似文献   

Efficiency of the modal shift and environmental policy on the Korean railroad   总被引：1，自引：1，他引：0  

Hyoung-Gi Kim  Chang-Yeoul Choi  Jung-Wouk Woo  Yongrok Choi  Kyonghwan Kim  Desheng Dash Wu 《Stochastic Environmental Research and Risk Assessment (SERRA)》2011,25(3):305-322

The Kyoto Protocol calls for industrialized nations to cut greenhouse gas emissions by 5% from 1990 levels by 2008–2012, so developed countries are presenting various policies to reduce greenhouse gas that is produced in transport fields. One of those polices is a modal shift that changes from road freight to sea, inland waterways and railroad transportation that is eco-friendly. The increase of road freight brings road congestion, accidents, logistic costs, air pollution and greenhouse gases. Railroads are superior to the other modes of transportation in mass transportability, high speed, timeliness, safety and environmental-friendliness, but the railway industry has been pushed behind in competition. Korean railroads were used by passengers and for freight transport popularly until the middle of the 20th century. However, because of the sudden change of logistics environments, having time efficiency being most important, railroads lost logistic competitive power against the transportation by truck. This paper intends to examine the modal shift to railroad transportation, which enjoys high interest as environmentally-friendly logistics, i.e., the modal shift strategy. Efficiency analysis is conducted using DEA and exploratory factors are identified for the modal shift of the companies. This paper also proposes an alternative plan for green logistics and environmentally-friendly logistics, by analyzing the characteristics of the railroad cargo transportation system and the conditions of local railroad cargo transportation.  相似文献   

Stabilization of arsenic-contaminated mine tailings using natural and calcined oyster shells   总被引：1，自引：0，他引：1  

Deok Hyun Moon  Kyoung-Woong Kim  In-Ho Yoon  Dennis G. Grubb  Dae-Yewn Shin  Kyung Hoon Cheong  Hyung-Il Choi  Yong Sik Ok  Jeong-Hun Park 《Environmental Earth Sciences》2011,64(3):597-605

Natural oyster shells (NOS) and calcined oyster shells (COS) were used to immobilize arsenic (As) from contaminated mine tailings. In addition, a blend of Portland cement (PC)/cement kiln dust (CKD) was used as a stabilizing agent. The Korean Standard Test (KST) method (1 N HCl extraction) was used to evaluate the effectiveness of the treatment. The experimental results showed that COS effectively immobilized As in treated mine tailings. Specifically, an As concentration less than 1 mg L⁻¹ was obtained following COS treatment at 25 and 30 wt%. However, all the samples subjected to NOS treatments failed the Korean warning standard of 1.2 mg L⁻¹ after 28 days of curing. All of the COS-PC treatments were successful meeting the Korean warning standard after 7 days of curing. However, the PC-only treatment failed to meet the Korean warning standard. Similarly, the CKD-only treatment was failed to meet the Korean warning standard after 7 days of curing. However, the COS-CKD treatment showed that when the COS content was greater than 20 wt%, less than 1 mg L⁻¹ of As leachability was obtained. Scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM–EDX) showed needle-like and torpedo-like Ca–As phases in the COS-treated samples suggesting that As was strongly associated with Ca and O. X-ray absorption near edge structure (XANES) analyses confirmed that As(V) was prevalent in the tailings and that there were no changes in As speciation following NOS or COS treatment.  相似文献   

Current Structure and Volume Transport in the Jeju Strait Observed for a Year with Multiple ADCP Moorings     

Shin  Chang-Woong  Min  Hong Sik  Lee  Seok  Kang  Hyoun-Woo  Ku  Bonhwa  Kim  Dong Guk  Park  Joonseong  Kwon  Soonyeol  Choi  Byoung-Ju 《Ocean Science Journal》2022,57(3):365-380

Ocean Science Journal - The seasonal and spatial variation of the current structure and volume transport across the Jeju Strait (JS) is described based on an analysis of the data from five bottom...  相似文献   

Preface: Hydrogeology of cold regions     

Larry D. Hinzman  Georgia Destouni  Ming-ko Woo 《Hydrogeology Journal》2013,21(1):1-4

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Possible role of brines in the darkening and flow-like features on the Martian polar dunes based on HiRISE images     

A. Kereszturi  D. Möhlmann  Sz. Berczi  A. Horvath  A. Sik  E. Szathmary 《Planetary and Space Science》2011,59(13):1413-1427

This work identifies and describes features of the changing seasonal frost-covered surface of Mars based on HiRISE images, and analyses the possibility that ephemeral liquid brine formation produces them. Because some of these dark features show flow-like appearance, and salts on Mars are present, liquid brines might be also present, possibly accounting for the changing droplet-like features on the Phoenix lander.We observed in-situ darkening and movement of dark features (or movement of the darkening front) on seasonal frost-covered polar dunes. Darkening and brightening may happen within several meters from each other during local spring. Darkening always starts from the bottom and moves up, while brightening progresses from top and moves toward the bottom between the small dune ripples. Brightening occurs during the springtime warming on time scales of several days close to the sites of darkening; therefore, dark material falling from the air, and refreezing of bright ice on it, does not adequately explain the observations. Interpreting the observations as brine-related melting or refreezing also poses problems, but because brine may engulf salt grains or ice blocks, phase changes here could be influenced by factors other than temperature values, and could produce the observations.Analysis of absolute albedo changes indicates that the flow-like features are the darkest at their lower frontal end, sometimes darker than the dark spot from which they originate. A bright halo (white collar) also forms around these spots, possibly due to refreezing. Inside the observed larger spots an outer gray area surrounds the central darkest cores, which is about 10 cm lower than the surrounding bright CO₂ ice. At those places, most or all of the CO₂ ice deposited earlier has disappeared, and H₂O ice is present. Observations of dark flow features moving on the top of this H₂O rich layer suggest even if the flow features start as dry dune avalanches of rolling grains, their dark material heated by solar insolation is in contact with H₂O ice and may produce brines.  相似文献