Influence of extractable soil manganese on oxidation capacity of different soils in Korea

We examined the relationship between soil oxidation capacity and extractable soil manganese, iron oxides, and other soil properties. The Korean soils examined in this study exhibited low to medium Cr oxidation capacities, oxidizing 0.00–0.47 mmol/kg, except for TG-4 soils, which had the highest capacity for oxidizing added Cr(III) [>1.01 mmol/kg of oxidized Cr(VI)]. TG and US soils, with high Mn contents, had relatively high oxidation capacities. The Mn amounts extracted by dithionite-citrate-bicarbonate (DCB) (Mn^d), NH₂OH·HCl (Mn^h), and hydroquinone (Mn^r) were generally very similar, except for the YS1 soils, and were well correlated. Only small proportions of either total Mn or DCB-extractable Mn were extracted by NH₂OH·HCl and hydroquinone in the YS1 soils, suggesting inclusion of NH₂OH·HCl and hydroquinone-resistant Mn oxides, because these extractants are weaker reductants than DCB. No Cr oxidation test results were closely related to total Mn concentrations, but Mn^d, Mn^h, and Mn^r showed a relatively high correlation with the Cr tests (r = 0.655–0.851; P < 0.01). The concentrations of Mn^d and Mn^h were better correlated with the Cr oxidation tests than was the Mn^r concentration, suggesting that the oxidation capacity of our soil samples can be better explained by Mn^d and Mn^h than by Mn^r. The first component in principal components analysis indicated that extractable soil Mn was a main factor controlling net Cr oxidation in the soils. Total soil Mn, Fe oxides, and the clay fraction are crucial for predicting the mobility of pollutants and heavy metals in soils. The second principal component indicated that the presence of Fe oxides in soils had a significant relationship with the clay fraction and total Mn oxide, and was also related to heavy-metal concentrations (Zn, Cd, and Cu, but not Pb).     

Growth dynamics of the deep-water Asian eelgrass, <Emphasis Type="Italic">Zostera asiatica</Emphasis>, in the eastern coastal waters of Korea

Among the seagrasses that occur along the coast of Korea, Zostera asiatica inhabits the deepest depth; however, to date, there is limited information on its ecology. This study presents the first quantitative data on the seasonal growth dynamics of Z. asiatica in Korea. We measured seasonal growth and morphological characteristics, as well as environmental factors, including underwater irradiance, water temperature, salinity and nutrient concentrations of the water column and sediment pore water, bimonthly from July 2012 to May 2015. Underwater irradiance showed clear seasonal trends, increasing in the spring and summer and decreasing in the fall and winter, ranging from 2.4 ± 0.2 mol photons m^-2 d^-1 in November 2012 to 12.8 ± 1.3 mol photons m^-2 d^-1 in July 2014. Water temperature also followed a strong seasonal trend similar to underwater irradiance, ranging from 9.8 ± 0.1°C in January 2013 to 20.5 ± 0.2°C in September 2013. Nutrient availability fluctuated substantially, but there was no evidence of distinct seasonal variations. Shoot density, biomass, leaf productivity, and morphological characteristics of Z. asiatica exhibited significant seasonal variations: maximum values of these variables occurred in summer, and the minima were recorded in winter. Total shoot density was highest (218.8 ± 18.8 shoots m^-2) in July 2012 and lowest (106.3 ± 6.3 shoots m^-2) in January 2013. Total biomass ranged from 182.6 ± 16.9 g dry weight (DW) m^-2 in January 2015 to 310.9 ± 6.4 g DW m^-2 in July 2014.Areal leaf production was highest (4.9 ± 0.0 g DW m^-2 d^-1) in July 2012 and lowest (1.4 ± 0.2 g DW m^-2 d^-1) in January 2013. The optimum water temperature for the growth of Z. asiatica was between 16-19°C. Growth of Z. asiatica was more strongly correlated with underwater irradiance than water temperature, suggesting that light is the most important factor determining seasonality of Z. asiatica at the study site.     

朝鲜平南盆地祥原超群的沉积时代与拉伸纪早期碳同位素负漂移

朝鲜平南盆地与东华北克拉通(中朝克拉通)中新元古代盆地的对比存在争议,准确厘定相关沉积建造的沉积时限是解决这些争议的关键。朝鲜平南盆地的地层主体为祥原超群,从下往上依次为直岘群、祠堂隅群、默川群、灭恶山群和燕滩群。直岘群是祥原超群的最下部层位,大部分由陆源碎屑岩组成。从平南盆地"北部型"和"南部型"直岘群碎屑岩中分选锆石,测得LA-ICP-MS U-Pb年龄,限定祥原超群沉积时代晚于1100Ma,并且得出所谓的"北部型"和"南部型"地层没有时代和物源差异。鉴于默川群的基性岩床时代为~900Ma,祥原超群的沉积时代为新元古代早期(1000~900Ma),燕滩群的时代可能稍晚。这说明平南盆地与华北徐淮盆地和旅大盆地等同时。祥原超群碳酸盐岩样品的δ~(13)C值数据表明,默川群时期碳同位素发生了负漂移(δ~(13)C值为-6‰~-5‰)。鉴于侵入到默川群的基性岩床的时代为~900Ma,我们认为该碳同位素(δ~(13)C值)负漂移略早于~900Ma,可能与同一时期的岩浆活动有关。     

Assessment of shallow landslide susceptibility using the transient infiltration flow model and GIS-based probabilistic approach

This study proposes a probabilistic analysis method for modeling rainfall-induced shallow landslide susceptibility by combining a transient infiltration flow model and Monte Carlo simulations. The spatiotemporal change in pore water pressure over time caused by rainfall infiltration is one of the most important factors causing landslides. Therefore, the transient infiltration hydrogeological model was adopted to estimate the pore water pressure within the hill slope and to analyze landslide susceptibility. In addition, because of the inherent uncertainty and variability caused by complex geological conditions and the limited number of available soil samples over a large area, this study utilized probabilistic analysis based on Monte Carlo simulations to account for the variability in the input parameters. The analysis was performed in a geographic information system (GIS) environment because GIS can deal efficiently with a large volume of spatial data. To evaluate its effectiveness, the proposed analysis method was applied to a study area that had experienced a large number of landslides in July 2006. For the susceptibility analysis, a spatial database of input parameters and a landslide inventory map were constructed in a GIS environment. The results of the landslide susceptibility assessment were compared with the landslide inventory, and the proposed approach demonstrated good predictive performance. In addition, the probabilistic method exhibited better performance than the deterministic alternative. Thus, analysis methods that account for uncertainties in input parameters are more appropriate for analysis of an extensive area, for which uncertainties may significantly affect the predictions because of the large area and limited data.     

朝鲜半岛冠帽地块的基底属性:来自银德洞变质侵入杂岩的锆石U-Pb年代学和岩石地球化学证据

地体基底建造的甄别和表征是联结华北克拉通与朝鲜半岛早期演化历史的基本纽带。针对朝鲜半岛前寒武纪基底建造研究方面的薄弱环节,本文表征了冠帽地块清津地区银德洞出露的变质深成侵入杂岩。3个代表性样品的SIMS锆石U-Pb定年结果显示,早期中性片麻岩记录的岩浆侵入年龄为约2.53 Ga,晚期钾长花岗质片麻岩记录的岩浆侵入年龄为约2.51 Ga,表明银德洞变质杂岩形成于新太古代晚期。参考变质杂岩的岩石地球化学特征,其原岩组成可能包括石英闪长岩和钾长花岗岩,大体上可与全球典型的岩浆型紫苏花岗岩系列相类比。结合3个样品变化较大的锆石εH f(t)值(-1.7~+10.5),我们推测银德洞变质侵入杂岩可能形成于玄武质下地壳岩石的部分熔融及其后的结晶分异作用,代表了活动大陆边缘岩浆弧环境下的典型产物。银德洞变质杂岩归属于新太古代岩浆弧根部岩浆岩建造的研究认识,不仅为判定冠帽地块与华北克拉通东部的吉南和龙地块以及辽北清原地块之间的亲缘性提供了岩石学证据,而且暗示这些地块在新太古代共同处在一个类似于安第斯活动大陆边缘的构造环境。