Temporal Variations on Soil Salinity and Cation Displacement at Saemangeum and Yeongsangang Reclaimed Tidal Lands

Soil salinity at reclaimed tidal land in Korea is highly variable and depending on soil characteristics and weather conditions. The objective of this study was to evaluate the temporal changes on soil salinity and the relationships between soil salinity and salinity parameters in reclaimed tidal lands. Soil samples were periodically collected at 0 - 20 cm (surface) and 20 - 40 cm (subsurface) layer at Saemangeum (sandy loam) and Yeongsangang (silty loam) reclaimed tidal land. Electrical conductivity (EC) had a wide range from 0.0 to 34.3 dS·m-1 during the experimental period. The average soil EC was 6.4 and 3.4 dS·m-1 at Saemangeum and Yeongsangang reclaimed tidal land, respectively. Soluble sodium concentration had great variations and it was the most important single factor for temporal variations of soil EC regardless of soil textural properties. Calcium concentration was negatively correlated with soil EC and soluble sodium. Soil exchangeable sodium percentage (ESP) was estimated as a function of soil sodium adsorption ratio (SAR) and a linear regression model (ESP = 6.075 (SAR) + 0.677 for Saemangeum and ESP = 3.925 (SAR) + 0.421 for Yeongsangang reclaimed tidal soil) was suggested for predicting soil ESP from soil SAR. The characteristics of reclaimed tidal lands had different shares of saline and sodic properties during the experimental period. Saemangeum reclaimed tidal soil was highly characterized by sodium, but the effect of sodium on Yeongsangang soil was less pronounced. Our results indicate that persistent monitoring and modeling on soil salinity at reclaimed tidal soil is fundamental and the results can provide some useful information for deciding management plans for diverse utilization or to reduce salt damage for stable crop production at reclaimed tidal land.

Effect of Sub-T_g Annealing on the Corrosion Resistance of the Cu–Zr Amorphous Alloys

Despite the economy of material cost and excellent toughness of Cu-based amorphous alloys,especially CusoZrso,their poor corrosion resistance to a chloride medium limits their widespread applications.In this study,corrosion tests were performed on the CusoZrso amorphous alloy with different degrees of short-range order,which were prepared by annealing below the glass transition temperature（Tg）.It was found that the corrosion resistance of amorphous alloys is improved to a significant level when the alloys were heated below Tg.Calorimetric studies showed that thermally activated relaxation process of created disorder,which occurs during sub-Tg annealing,is responsible for the improvement in the corrosion resistance.Molecular dynamics simulations performed on the Cu-Zr amorphous alloys demonstrated that the relaxation process of the alloys is associated with the formation of energetically stable icosahedra and icosahedron-like structures.Our study highlights the effects of sub-Tg annealing on the improvement in the corrosion resistance of the amorphous alloys from the viewpoint the relaxation process of the short-range orders.