Factors controlling groundwater chemistry in an agricultural area with complex topographic and land use patterns in mid‐western South Korea

Shallow and bedrock groundwater from granitic aquifers were investigated for the hydrogeochemistry of major and minor constituents in an agricultural area. Nitrate concentrations were observed up to 49 mg/l as NO₃‐N, with 22% of samples exceeding the drinking water standard, which could pose a significant threat because most residents rely on groundwater as their drinking water source. Principal component analysis revealed three principal components (PCs): (1) nitrate contamination, contributed by major cations, Cl^?, SO and NO , (2) reduction processes positively involving Fe, Mn and B, and negatively involving dissolved oxygen and NO and (3) natural mineralization, involving HCO and F^?. Cluster analysis, performed on the PC scores, resulted in seven sample groups, which were successfully identified by total depth, elevation and land use. The nitrate‐contaminated groups had mixed land uses, with locally concentrated residential areas. Uncontaminated groundwater groups were found in the natural environment, including high‐altitude spring water and bedrock groundwater with a higher degree of natural mineralization. Shallow groundwater groups in paddy fields in lowlands were affected by reducing environments, of which one group was characterized by high Fe, Mn and B, and negligible nitrate. Groundwater with intermediate nitrate and lower Cl^? and SO was found primarily in hilly terrains with orchards and vegetable gardens, indicating lower contaminant loadings than lowland areas. Higher concentrations of F^? and nitrate were observed in the nitrate‐contaminated water, which seemed unlikely to be explained by groundwater mixing. The strong acidity generated from nitrification may infiltrate deeper into the aquifer, induce accelerated weathering of bedrock and result in the coexistence of F^? and nitrate, which may be an evidence of intense nitrate loading, leading to soil acidification. Multivariate statistical analysis successfully delineated hydrochemical characteristics of groundwater attained by natural and anthropogenic processes in an agriculturally stressed area with complex topographic land use patterns. Copyright © 2009 John Wiley & Sons, Ltd.     

Changes in topography and surface sediments by the Saemangeum dyke in an estuarine complex,west coast of Korea

The effects of a giant offshore dyke, Saemangeum, have been of special interest on both scientific and environmental aspects. Without any rival worldwide with regard to the ample scale and estuarine setting, the Saemangeum dyke and its vicinity (Saemangeum Area) should be an unprecedented experimental site for monitoring the consequence of the estuarine developments with dykes. In order to unravel geologic changes caused by the Saemangeum dyke, we collected a number of surface sediment samples and bathymetric profiles from a full coverage of the Saemangeum Area, and compared topography and sediment phase on the inter-annual (2002–2006, post-construction) and decadal (1982–2002, between pre- and post-construction) timescales.     

Monitoring of suspended sediment variation using Landsat and MODIS in the Saemangeum coastal area of Korea

Suspended sediment concentration (SS) is an important indicator of marine environmental changes due to natural causes such as tides, tidal currents, and river discharges, as well as human activities such as construction in coastal regions. In the Saemangeum area on the west coast of Korea, construction of a huge tidal dyke for land reclamation has strongly influenced the coastal environment. This study used remotely sensed data to analyze the SS changes in coastal waters caused by the dyke construction. Landsat and MODIS satellite images were used for the spatial analysis of finer patterns and for the detailed temporal analysis, respectively. Forty Landsat scenes and 105 monthly composite MODIS images observed during 1985-2010 were employed, and four field campaigns (from 2005 to 2006) were performed to verify the image-derived SS. The results of the satellite data analyses showed that the seawater was clear before the dyke construction, with SS values lower than 20 g/m(3). These values increased continuously as the dyke construction progressed. The maximum SS values appeared just before completion of the fourth dyke. Values decreased to below 5 g/m(3) after dyke construction. These changes indicated tidal current modification. Some eddies and plumes were observed in the images generated from Landsat data. Landsat and MODIS can reveal that coastal water turbidity was greatly reduced after completion of the construction.     

The Application of Artificial Neural Networks to Landslide Susceptibility Mapping at Janghung, Korea

The purpose of this study was to develop techniques for landslide susceptibility using artificial neural networks and then to apply these to the selected study area at Janghung in Korea. Landslide locations were identified from interpretation of satellite images and field survey data, and a spatial database of the topography, soil, forest, and land use. Thirteen landslide-related factors were extracted from the spatial database. These factors were then used with an artificial neural network to analyze landslide susceptibility. Each factor's weight was determined by the back-propagation training method. Five different training sets were applied to analyze and verify the effect of training. Then the landslide susceptibility indices were calculated using the back-propagation weights, and susceptibility maps were constructed from Geographic Information System (GIS) data for the five cases. Landslide locations were used to verify results of the landslide susceptibility maps and to compare them. The artificial neural network proved to be an effective tool for analyzing landslide susceptibility.     

Protective effects of Ecklonia cava extract on the toxicity and oxidative stress induced by hair dye in in-vitro and in-vivo models

Oxidative hair dyes containing p-phenylenediamine(PPD) are reported to induce an allergic reaction by promoting oxidative stress when absorbed through the skin. Despite the associated risk, these hair dyes remain popular owing to their convenience and sharpness of color. This makes it important to minimize the cytotoxicity and oxidative stress induced by PPD-containing hair dyes. Ecklonia cava extract has been evaluated in different studies for its protective effects against external stress in fibroblasts and keratinocytes. Our study was aimed at using in-vitro and in-vivo models to investigate the extract's effects on cytotoxicity of and oxidative stress induced by PPD-containing hair dyes. Analysis of CIEL*a*b* Color space was first used to determine the range of E. cava extract that would not interfere with the coloring ability of the dye upon addition. Subsequently, the set ranges of E. cava extract(5% and 7%) were added to the hair dye and their toxicity assessed by evaluating the viability of fibroblasts and keratinocytes. The effects on developmental phenotypes and induction of oxidative stress by hair dye were evaluated and compared with those of hair dyes containing different contents of E. cava extract using an in-vivo zebrafish model. Our results showed that E. cava extract in hair dye could significantly decrease the cytotoxicity and levels of oxidative stress caused by hair dyes containing PPD in both in-vitro and in-vivo models.These results suggest that the addition of 7% E. cava extract to 250 μg/mL hair dye does not interfere with the coloring ability of the dye while showing significant protective effects against the hair dye. The study proposes that the use of E. cava extract as an adduct to hair dyes containing PPD reduces the cytotoxicity and oxidative stress induced by these hair dyes.     

Spatial variations of small phytoplankton contributions in the Northern Bering Sea and the Southern Chukchi Sea

Phytoplankton size classes (hereafter, PSCs) were derived from satellite ocean color data using a present phytoplankton abundance-based optical algorithm in the northern Bering and southern Chukchi Seas to characterize the spatial and seasonal variations of the different PSC and investigate the contributions of small phytoplankton to the total phytoplankton biomass. The comparison results showed that the phytoplankton abundance-based method approach could reasonably classify the three PSCs (pico-, nano-, and micro phytoplankton). The satellite maps of the dominant PSCs were derived using long-term satellite ocean color data. The general spatial distribution showed that the large (micro-) phytoplankton were dominant in the coastal waters and the west side of the Bering strait, while the small size (nano- or pico-) phytoplankton were dominant in the open ocean waters. Nano- and microphytoplankton were dominant in May and October in most of the study area, while pico-phytoplankton were dominant in the summer months in the open ocean waters. The annual variation in small phytoplankton dominance had a strong positive relationship with the annual mean sea surface temperature (SST), which is consistent with the increasing dominance of small phytoplankton biomass as water temperature increases. Microphytoplankton have an apparent increasing trend in the southeastern Chukchi Sea but slightly decreasing trends in Chirikov and St. Lawrence Island Polynya (SLIP). In contrast, there were increasing trends in picophytoplankton in Chirikov and SLIP, which seems to be related to increasing annual SST. It is crucial to monitor changes in dominant groups of phytoplankton community in the Bering and Chukchi Seas as important biological hotspots responding to the recent changes in environmental conditions.     

A study of igneous rocks related to Zn–Pb mineralization in the Shinyemi and Gagok deposits of the Taebaeksan Basin,South Korea

The Shinyemi and Gagok deposits, located in the Taebaeksan Basin, South Korea, display Zn–Pb mineralization along a contact between Cretaceous granitoids and Cambrian–Ordovician carbonates of the Joseon Supergroup. The Shinyemi mine is one of the largest polymetallic skarn‐type magnetite deposits in South Korea and comprises Fe and Fe–Mo–Zn skarns, and Zn–Cu–Pb replacement deposits. Both deposits yield similar Cretaceous mineralization ages, and granitoids associated with the two deposits displaying similar mineral textures and compositions, are highly evolved, and were emplaced at a shallow depth. They are classified as calc‐alkaline, I‐type granites (magnetite series) and were formed in a volcanic arc. Compositional variation is less in the Shinyemi granites and aplites (e.g., SiO₂ = 74.4–76.6 wt% and 74.4–75.1 wt%, respectively) than in the Gagok granites and aplites (e.g., SiO₂ = 65.6–68.0 wt% and 74.9–76.5 wt%, respectively). Furthermore, SiO₂ vs K/Rb and SiO₂ vs Rb/Sr diagrams indicate that the Shinyemi granitoids are more evolved than the Gagok granitoids. Shinyemi granitoids had been already differentiated highly in deep depth and then intruded into shallow depth, so both granite and aplite show the highly evolved similar chemical compositions. Whereas, less differentiated Gagok granitoids were separated into two phases in the last stage at shallow depth, so granite and aplite show different compositions. The amounts of granites and aplite are similar in the Shinyemi deposit, whereas the aplite appears in an amount less than the granite in the Gagok deposit. For this reason, the Shinyemi granitoids caused not only Fe enrichment during formation of the dolomite‐hosted magnesian skarn but also was associated with Mo mineralization in the Shinyemi deposit. Zn mineralization of the Gagok deposit was mainly caused by granite rather than aplite. Our data suggest that the variation in mineralization displayed by the two deposits resulted from differences in the compositions of their associated igneous intrusions.     

Gas hydrates in the western deep-water Ulleung Basin, East Sea of Korea

Geophysical surveys and geological studies of gas hydrates in the western deep-water Ulleung Basin of the East Sea off the east coast of Korea have been carried out by the Korea Institute of Geoscience and Mineral Resources (KIGAM) since 2000. The work included a grid of 4782 km of 2D multi-channel seismic reflection lines and 11 piston cores 5–8 m long. In the piston cores, cracks generally parallel to bedding suggest significant in-situ gas. The cores showed high amounts of total organic carbon (TOC), and from the southern study area showed high residual hydrocarbon gas concentrations. The lack of higher hydrocarbons and the carbon isotope ratios indicate that the methane is primarily biogenic. The seismic data show areas of bottom-simulating reflectors (BSRs) that are associated with gas hydrates and underlying free gas. An important observation is the numerous seismic blanking zones up to 2 km across that probably reflect widespread fluid and gas venting and that are inferred to contain substantial gas hydrate. Some of the important results are: (1) BSRs are widespread, although most have low amplitudes; (2) increased P-wave velocities above some BSRs suggest distributed low to moderate concentration gas hydrate whereas a velocity decrease below the BSR suggests free gas; (3) the blanking zones are often associated with upbowing of sedimentary bedding reflectors in time sections that has been interpreted at least in part due to velocity pull-up produced by high-velocity gas hydrate. High gas hydrate concentrations are also inferred in several examples where high interval velocities are resolved within the blanking zones. Recently, gas hydrate recoveries by the piston coring and deep-drilling in 2007 support the interpretation of substantial gas hydrate in many of these structures.     

Physiological and biochemical responses of <Emphasis Type="Italic">Prorocentrum minimum</Emphasis> to high light stress

Prorocentrum minimum is a common bloomforming photosynthetic dinoflagellate found along the southern coast of Korea. To investigate the adaptive responses of P. minimum to high light stress, we measured growth rate, and generation of reactive oxidative species (ROS), superoxide dismutase (SOD), catalase (CAT), and malondialdehyde (MDA) in cultures exposed to normal (NL) and high light levels (HL). The results showed that HL (800 μmol m^?2 s^?1) inhibited growth of P. minimum, with maximal inhibition after 7–9 days. HL also increased the amount of ROS and MDA, suggesting that HL stress leads to oxidative damage and lipid peroxidation in this species. Under HL, we first detected superoxide on day 4 and H₂O₂ on day 5. We also detected SOD activity on day 5 and CAT activity on day 6. The level of lipid peroxidation, an indicator of cell death, was high on day 8. Addition of diphenyleneiodonium (DPI), an NAD(P)H inhibitor, decreased the levels of superoxide generation and lipid peroxidation. Our results indicate that the production of ROS which results from HL stress in P. minimum also induces antioxidative enzymes that counteract oxidative damage and allow P. minimum to survive.