The remediation of soil contaminated with heavy metals is an ongoing environmental concern. Paddy soils contaminated with Cd and Zn were collected from around abandoned metals mines in Korea. ...Limestone and steel slag were mixed with the collected soil, as amendments for Cd and Zn immobilization. Sequential extraction, lettuce cultivation and five single extraction methods were carried out to assess the effects on Cd and Zn immobilization using amendments. The exchangeable fraction of Cd and Zn was decreased and Fe–Mn oxides fraction increased by stabilization using amendments. In addition, the accumulation of Cd and Zn in lettuce decreased in treated soil and indicated the Cd and Zn immobilization effect in soil by the amendments. The extractable Cd and Zn by CaCl
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and Mehlich-3 in the untreated soils were higher than that of treated soils, whereas Cd and Zn extraction by ethylenediaminetetraacetic acid (EDTA), diethylene tetramine penta-acetic acid (DTPA) and toxicity characteristic leaching procedure (TCLP) has a small or no difference between the untreated and treated soils. The extraction results by CaCl
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and Mehlich-3 methods present reasonable results for Cd and Zn immobilization in soil than EDTA, DTPA and TCLP methods. Therefore, the choice of appropriate extraction method is very important when there is the assessment of Cd and Zn immobilization efficiency.
Damages caused by landslides have been increasing because of the greater frequency of localized heavy rain. To prevent landslide disasters more efficiently, more studies in relation to predicting the ...initiation areas of debris flows that cause large-scale damage are necessary. The main purpose of this study is to develop a criterion for detecting debris flow initiation areas by using an empirical method that was chosen from several types of approaches to debris flow initiation detection. In this study, ten GIS-based geomorphological datasets were obtained from slide and debris flow initiation areas located in Seoul, Gyeonggi Province and Gangwon Province. The geomorphological characteristics of slide and debris flow occurrence areas were analyzed through a comparative analysis to identify relationships between debris flow initiation and each topographic index. An initiation criterion for debris flows based on the geomorphological characteristics was suggested using an Artificial Neural Network (ANN) model combined with a modified threshold for the relationship between slope and upslope contributing area. To validate the suitability of the initiation criterion for debris flow, sequential applications of slope failure analysis and debris flow initiation analysis were conducted on a case study site to simulate the actual debris flow events. As a result of the debris flow initiation analysis, the prediction capture rate of the debris flow initiation criterion was determined to be 88.9%. Debris flow initiation areas totaling 143,300m2 were identified among 1,935,400m2 of slope failure areas predicted in the slope failure analysis. It is efficient to apply the debris flow initiation criterion in the debris flow simulation because slope failure areas are only partly transformed into debris flows.
•We developed a new criterion to predict the debris flow initiation area.•The criterion composed of an ANN model and a modified slope-UCA threshold was in good agreement with actual cases.•We conducted sequential applications of slope failure analysis and debris flow initiation analysis to validate the criterion.
The Jangsan Formation distributed in the Taebaeksan Basin, central eastern Korea is unfossiliferous and is composed of quartz arenite. This formation is conventionally believed to be the lowermost ...stratigraphic unit of the lower Paleozoic sequence deposited on the Yeongnam massif in South Korea, corresponding to Early Cambrian in age. U–Pb dating of detrital zircon grains using a laser ablation inductively coupled mass spectrometer yields ages ranging from Archean to Middle Proterozoic (1738±67Ma to 3058±53Ma). Detrital zircons show no ages younger than 1.8Ga, suggesting that the Jangsan Formation was deposited at some time after this age, but much prior to ca. 520Ma, the depositional age of the immediately overlying Myobong Formation. This interpretation is supported by the recent report on the presence of the unconformity between the Jangsan and the Myobong formations (Kim and Lee, 2006). Zircon ages from Jangsan sandstones define two major groups: Archean-age grains with a maximum frequency at about 2.5Ga and Paleoproterozoic-age grains with maximum frequencies at about 2.1 and 1.8Ga. The observed zircon age distribution in the Jangsan sandstones may represent that of the Yeongnam massif on which the Jangsan Formation was deposited. Such an age distribution of the Yeongnam massif matches well with that the North China block, suggestive of the Yeongnam massif being a part of the Sino-Korean craton during the Precambrian.
► Detrital zircon U-Pb ages of the Jangsan Formation reveal no ages younger than 1.8 Ga ► Zircon ages of the Jangsan Formation differs much from that of the overlying strata ► Combined with unconformity reported the depositional age of it seemed Proterozoic ► The source region, the Yeongnam massif, was a part of the Sino-Korean craton then
Debris flows are one of the perilous landslide-related hazards due to their fast flow velocity, large impact force, and long runout, in association with poor predictability. Debris-flow barriers that ...can minimize the energy of debris flows have been widely constructed to mitigate potential damages. However, the interactions between debris flows and barriers remain poorly understood, which hampers the optimal barrier installation against debris flows. Therefore, this study examined the effect of barrier locations, in particular source-to-barrier distance, on velocity and volume of debris flows via the numerical approach based on smoothed particle hydrodynamics (SPH). A debris-flow event was simulated on a 3D terrain, in which a closed-type barrier was numerically created at predetermined locations along a debris-flow channel, varying the source-to-barrier distance from the initiation point. In all cases, the closed-type barrier significantly reduced the velocity and volume of the debris flows, compared to the cases without a barrier. When the initial volume of source debris was small, or when the flow path was short, the barriers effectively blocked the debris flow regardless of the source-to-barrier distance. However, with a long flow path, installation of the barrier closer to the initiation location appeared more effective by preventing the debris volume from growing by entrainment. Our results contribute to a better understanding of how source-to-barrier distance influences debris-flow behavior, and show that the methodology presented herein can be further used to determine optimum and efficient designs for debris-flow barriers.
To constrain the depositional age of the lowermost Nakdong Formation in the Early Cretaceous Gyeongsang Basin, SHRIMP U–Pb age determination was carried out on zircon separates. The U–Pb compositions ...of detrital zircons from the Nakdong Formation yield a wide range of ages from the Archean to the Cretaceous but show a marked contrast in age distribution according to the geographical locations within the basin. The provenance of the southern Nakdong Formation is dominantly the surrounding Yeongnam Massif, which is composed of Paleoproterozoic metamorphic rocks and Triassic to Jurassic plutonic rocks, whereas the central to northern Nakdong Formation records significant sediment derivation from the Okcheon Metamorphic Belt, which is distributed to the northwest, in addition to the contribution from the Yeongnam Massif. It is suggested that the maximum depositional age of the Nakdong Formation is ca 127 Ma, based on its youngest detrital zircon age population. The onset of its deposition at 127 Ma coincided with the tectonic inversion in East Asia from a compressional to an extensional geodynamic setting, probably due to the contemporaneous change in the drift direction of the Izanagi Plate and its subsequent oblique subduction.
The maximum depositional age of the Nakdong Formation can be limited to ca 127 Ma, based on its youngest detrital zircon age population, which corresponds to the tectonic conversion period of East Asia. The provenance of the southern Nakdong Formation is dominantly the surrounding Yeongnam Massif, whereas the central to northern Nakdong Formation records significant sediment derivation from the Okcheon Metamorphic Belt to the northwest.
The paleogeographic configuration of continental blocks around East Gondwana during the Neoproterozoic–early Cambrian is controversial. This study reports the U–Pb ages of detrital zircons and Nd ...isotopic composition of the Neoproterozoic–early Cambrian succession developed on the Precambrian basement in South Korea, which formed the southeastern portion of the Sino-Korean block (SKB) in its present configuration. Three stratigraphic units are addressed in this study: the Neoproterozoic Jangsan, early Cambrian Myeonsan, and early–middle Cambrian Myobong Formations. Both the Jangsan (white to pink quartz sandstone) and Myeonsan (dark gray ilmenite-rich sandstone/shale) formations are barren and are unconformably and conformably overlain, respectively, by the dark gray, fossiliferous fine-grained Myobong Formations. The Jangsan and Myeonsan Formations contain zircons with Archean–Paleoproterozoic ages, indicative of detritus derived from the local Precambrian basement. In contrast, the Myobong Formation is dominated by Mesoproterozoic to Neoproterozoic zircons, which are not represented in the local Precambrian basement. The Sm–Nd model ages of the Myobong Formation are younger than those of the underlying strata, indicative of significant changes in provenance during the deposition of this formation. Comparison with coeval sediment having Gondwana signatures in the southern margin of the SKB and the Tethyan Himalayan terrane strongly suggests that the Myobong Formation was derived from orogens in East Gondwana. The results of this study reveal that the timing of the Myobong Formation deposition marks the onset of a sedimentation episode on the southeastern margin of the SKB, which was related to the emergence of a vast source province in East Gondwana, possibly aided by the Cambrian transgression onto the SKB. In comparison with the published literature, we argue for the paleogeographic continuity of the SKB with the northern margin of East Gondwana, possibly between northwestern Australia and northeastern India during the Neoproterozoic–early Cambrian.
•Cambrian paleogeography of the Sino-Korean block (SKB) is controversial.•We investigated detrital zircon U–Pb ages from the SE part of the SKB.•Locally-sourced zircons are present in the Neoproterozoic–earliest Cambrian strata.•The late early Cambrian strata contain East Gondwana-derived detrital zircons.•In Cambrian the SKB was connected with the northern margin of East Gondwana.
This study developed a deep learning based technique for the assessment of landslide susceptibility through a one-dimensional convolutional network (1D-CNN) and Bayesian optimisation in Southern ...Yangyang Province, South Korea. A total of 219 slide inventories and 17 slide conditioning variables were obtained for modelling. The data showed a complex scenario. Some past slides have spread over steep lands, while others have spread through flat terrain. Random forest (RF) served to keep only important factors for further analysis as a pre-processing measure. To select CNN hyperparameters, Bayesian optimization was used. Three methods contributed to overcoming the overfitting issue owing to small training data in our research. The selection of key factors by RF helped first of all to reduce information dimensionality. Second, the CNN model with 1D convolutions was intended to considerably decrease the number of its parameters. Third, a high rate of drop-out (0.66) helped reduce the CNN parameters. Overall accuracy, area under the receiver operating characteristics curve (AUROC) and 5-fold cross-validation were used to evaluate the models. CNN performance was compared to ANN and SVM. CNN achieved the highest accuracy on testing dataset (83.11%) and AUROC (0.880, 0.893, using testing and 5-fold CV, respectively). Bayesian optimization enhanced CNN accuracy by~3% (compared with default configuration). CNN could outperform ANN and SVM owing to its complicated architecture and handling of spatial correlations through convolution and pooling operations. In complex situations where some variables make a non-linear contribution to the occurrence of landslides, the method suggested could thus help develop landslide susceptibility maps.
•1D-CNN was used for landslide susceptibility mapping.•The proposed model was compared with feedforward neural networks and SVM.•Random Forest was used to identify significant landslide conditioning factors.•Bayesian optimization was applied to improve the model accuracy.•Model validation was accomplished using AUROC and 5-fold cross validation.
This study compares the landslide susceptibility maps from four application models, namely, (1) the bivariate model of the Dempster–Shafer based evidential belief function (EBF); (2) integration of ...the EBF in the knowledge-based analytical hierarchy process (AHP) as a pairwise comparison model processed by using all available causative factors; (3) integration of the EBF in the knowledge-based AHP as a pairwise comparison model by using high nominated causative factor weights only; and (4) integrated EBF in the logistic regression (LR) as a multivariate model by using nominated causative factor weights only. These models were tested in Pohang and Gyeongju Cities (South Korea) by using the geographic information system GIS platform. In the first step, a landslide inventory map consisting of 296 landslide locations were prepared from various data sources. Then, a total of 15 landslide causative factors (slope angle, slope aspect, curvature, surface roughness, altitude, distance from drainages, stream power index, topographic wetness index, wood age, wood diameter, wood type, forest density, soil thickness, soil texture, and soil drainage) were extracted from the database and then converted into a raster. Final susceptibility maps exhibit close results from the two models. Models 1 and 3 predicted 82.3% and 80% of testing data during the analysis, respectively. Thus, Models 1 and 3 show better performance than LR. These resultant maps can be used to extend the capability of bivariate statistical based model, by finding the relationship between each single conditioning factor and landslide locations, moreover, the proposed ensemble model can be used to show the inter-relationships importance between each conditioning factors, without the need to refer to the multivariate statistic. The research outcome may provide powerful tools for natural hazard assessment and land use planning.
•Used an ensemble EBF based AHP and LR for spatial prediction of landslide hazard•Tested the efficiency when subjectivity of knowledge based approaches is reduced•EBF determined the pre-processed relationship between causative factors.•Tested the efficiency of AHP and LR to find the effective causative failure factors•EBF based AHP can be used for landslide hazard prediction in medium scale areas.
Many studies have examined the application of soil amendments, including pH change-induced immobilizers, adsorbents, and organic materials, for soil remediation. This study evaluated the effects of ...various amendments on trace element stabilization and phytotoxicity, depending on the initial soil pH in acid, neutral, and alkali conditions. As in all types of soils, Fe and Ca were well stabilized on adsorption sites. There was an effect from pH control or adsorption mechanisms on the stabilization of cationic trace elements from inorganic amendments in acidic and neutral soil. Furthermore, acid mine drainage sludge has shown great potential for stabilizing most trace elements. In a phytotoxicity test, the ratio of the bioavailable fraction to the pseudo-total fraction significantly affected the uptake of trace elements by bok choy. While inorganic amendments efficiently decreased the bioavailability of trace elements, significant effects from organic amendments were not noticeable due to the short-term cultivation period. Therefore, the application of organic amendments for stabilizing trace elements in agricultural soil requires further study.
•Estimation of IDF curves for rainfall data comprises a classical task in hydrology.•Stationary assumption can be inadequate and lead to poor quantile estimates.•We model annual maximum series ...conditioned on the daily rainfall.•The Bayesian beta model is used to produce nonstationary IDF curves for Korea.•Model provides future climate IDF curves based on climate change scenarios.
The estimation of intensity-duration-frequency (IDF) curves for rainfall data comprises a classical task in hydrology studies to support a variety of water resources projects, including urban drainage and the design of flood control structures. In a changing climate, however, traditional approaches based on historical records of rainfall and on the stationary assumption can be inadequate and lead to poor estimates of rainfall intensity quantiles. Climate change scenarios built on General Circulation Models offer a way to access and estimate future changes in spatial and temporal rainfall patterns at the daily scale at the utmost, which is not as fine temporal resolution as required (e.g. hours) to directly estimate IDF curves. In this paper we propose a novel methodology based on a four-parameter beta distribution to estimate IDF curves conditioned on the observed (or simulated) daily rainfall, which becomes the time-varying upper bound of the updated nonstationary beta distribution. The inference is conducted in a Bayesian framework that provides a better way to take into account the uncertainty in the model parameters when building the IDF curves. The proposed model is tested using rainfall data from four stations located in South Korea and projected climate change Representative Concentration Pathways (RCPs) scenarios 6 and 8.5 from the Met Office Hadley Centre HadGEM3-RA model. The results show that the developed model fits the historical data as good as the traditional Generalized Extreme Value (GEV) distribution but is able to produce future IDF curves that significantly differ from the historically based IDF curves. The proposed model predicts for the stations and RCPs scenarios analysed in this work an increase in the intensity of extreme rainfalls of short duration with long return periods.
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