Because the density of variable charge in a soil is influenced by the solution concentration and the pH, exchanging ion transport in the soil is also affected by them. In this study, the effect of variable charge on exchanging ion transport in an allophanic Andisol (Typic Hydrudand) that has negative and positive variable charges was investigated experimentally. Miscible‐displacement experiments were conducted under saturated and unsaturated (−1.96 kPa of soil water pressure) conditions. The cases studied here involved ion exchange under a constant total concentration condition and a constant pH condition. A SrBr2 solution was applied to the soil column, which was initially saturated with a CaCl2 solution. The miscible‐displacement experiments were carried out at different total concentration (0.001–0.1 molc L−1) and pH (4.2–7.65). Bromine flowed out slowly at lower pH due to the large anion‐exchange capacity (AEC). Strontium discharged slowly at higher pH due to the large cation‐exchange capacity (CEC). The counterion penetrated slowly at a lower concentration because the amount of the counterion contained in a unit of solution volume was small. Observed breakthrough curves (BTCs) agreed with those expected from measured exchange isotherms. Based on the relationship between the Sr BTC and the Br BTC, no notable differences were observed between the BTCs under saturated conditions and those under unsaturated conditions. The influence of the solution concentration and the pH cannot be ignored when considering ion transport in an allophanic Andisol.
In soils, dissolved silicon (Si) is adsorbed onto soil particles or is leached into groundwater through the soil profile. Andisols may play an important role in contributing to high dissolved Si concentrations in groundwater on Jeju Island, Korea. In this study, we evaluated the available Si content that potentially affects groundwater composition and investigated the relationship between the available Si content and chemical properties of volcanic ash soil on Jeju Island. We used the 1 M sodium acetate buffer (pH 4.0) to extract the available Si. Selected chemical properties were determined for 290 topsoil samples collected from different land sites throughout Jeju Island, and we analyzed the available Si content in the typifying pedons of Jeju Island and mainland Korea. The available Si content in Jeju Island topsoils ranged from 75 to 150 mg·kg−1, and the available Si content of Andisols in both orchards and grasslands was significantly higher than that of non-Andisols. The available Si content was highly correlated with the amounts of oxalate extractable Si, Al, and Fe in Andisols and was negatively related to the Alp/Alo ratio. With increasing elevation, we detected a decrease in the available Si and allophane content in Andisols, whereas Al-humus complexes increased with increasing elevation. The ratio of available Si in the lowest subsoil/topsoil increased to a value of 6.0, indicating that large amounts of available Si are present in the subsoil. The available Si content in the lowest subsoil of Andisols on Jeju Island was 10 times higher than that in the typifying pedons of the Korean mainland. In contrast, there were no differences in the available Si content between the topsoil and the subsoil of the typifying pedon series of Jeju and mainland non-Andisols because of differences in pedogenic processes. Collectively, our findings indicate that weathering of Andisols on Jeju Island potentially affects the Si concentration in groundwater.
Korean soils are classified officially by Soil Taxonomy. Soils in Korea were classified into 7 orders, 14 suborders, 27 great groups, and 390 soil series. The dominant soils in Korea were Inceptisols and Entisols, and Alfisols, Ultisols, Andisols, Mollisols, and Histosols were distributed to a small extent. This study was conducted to reclassify Korean soils based on the second edition of Soil Taxonomy: A Basic System of Soil Classification for Making and Interpreting Soil Surveys. Morphological properties of typifying pedons of 405 soils were investigated and physio-chemical properties were analyzed according to Soil Survey Laboratory Methods Manual of USDA. Alfisols of 44 soils were reclassified; 16 soils were reclassified as Ultisols and 3 soils as Mollisols. Forty Andisols were reclassified; 3 soils were reclassified as other orders. Sixty-four Entisols soils were reclassified; 11 soils were reclassified as Inceptisols, 4 soils as Mollisols, and 3 soils as Andisols. Two hundreds and ten Inceptisols soils were reclassified; 39 soils were reclassified as Alfisols, 21 soils as Ultisols, 13 soils as Mollisols, and 2 soils as Andisols. Twenty-one Inceptisols soils, 16 Alfisols soils, and one Andisols soil were reclassified as Ultisols. As a result of reclassification of Korean soils, Korean soils are now classified into 7 orders, 17 suborders, 39 great groups, 85 subgroups, and 405 soil series. Alfisols and Ultisols are increased remarkably. Sixty Inceptisols soils are reclassified as Alfisols or Ultisols; 44 soils including 30 paddy soils are distributed on fluvio-marine plains, alluvial plaines, local valleys, alluvial fans, and mountain foot slopes. Soils distributed on rolling to hilly areas are mainly developed as Ultisols and some are as Alfisols. Also soils distributed on diluvial terrace are mainly developed as Ultisols and some are as Alfisols. Only two Mollisols soils were developed to a small extent. But 15 soils in Jeju Island and Ulreung Island, 3 soils in limestone areas, and 5 soils in coastal areas are classified as Mollisols. Inceptisols occupied 76.6% and Entisols occupied 12.9% of the whole country. Ultisols and Alfisols occupied only 5.0% and 3.8% respectively. Many soils deveped on rolling to hilly, diluvial terraces, local valleys, mountain foot slopes, etc. are reclassified as Ultisols and Alfisols. As a result Ultisols occupy 12.9% and Alfisols occupy 8.8% of the whole country.
This study was conducted to redetermine the rainfall erosion factor (R factor) in USLE for the estimation of soil loss at Korea. The redetermined R factor may be applied more precisely to interpret the changes of regional/yearly/seasonal patterns, including the amount of rainfall and the kinetic energy of rainfall, in Korea. This study calculated the R factors based on 60-minute precipitation data from 60 sites covering the whole country for 30 years from 1981 to 2010. As a result, the annual mean rainfall was 4,147 MJ mm ha -1 yr -1 hr -1 in Korea. Coastal regions of Jeonnam and Gyeongnam, northwest regions of Gyeonggi, and Seoul had the greater values of R factor compared to other regions. The annual mean R factors for every decade were 3,988, 4,085, and 4,370 MJ mm ha -1 yr -1 hr -1 in 1981~1990, 1991~2000, and 2001~2010, respectively. Generally, the R factors had an increasing tendency over and over pest decades. The ratios of summer R factor to total annual mean R factor were 69.8% (1981~1990), 73.7% (1991~2000), and 74.2% (2001~2010). We found that the absolute values and the relative ratios of summer rainfall are gradually increased.
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