DSpace Collection:

Characterization of aerosols over the Arctic Ocean and comparison permafrost data

Mon, 01 Aug 2016 00:00:00 GMT

Title: Characterization of aerosols over the Arctic Ocean and comparison permafrost data Authors: Park, Keyhong

Hydraulic and Thermal Conductivities of Kaolin-Silica Mixtures Under Different Consolidation Stresses

Mon, 01 Aug 2016 00:00:00 GMT

Title: Hydraulic and Thermal Conductivities of Kaolin-Silica Mixtures Under Different Consolidation Stresses Authors: Park, Keubo; Lee, Junhwan; Yoon, Hyung-koo; Kim, Dongwook Abstract: Stable backfill materials for the heat sensitive structures of buried power cables, hot water pipes, and gas pipelines are suggested to have low permeability and high heat transfer characteristics. Hydraulic and thermal conductivities of backfill materials or clay liners are important parameters in proper design and construction of geotechnical structures involved with heat transfers. In this study, to investigate optimal natural backfill or liner materials, thermal and hydraulic conductivities of Kaolin-Silica mixtures were examined based on the results from laboratory tests under different consolidation conditions. From the experiment results, the thermal conductivity increases while hydraulic conductivity decreases with increasing density during consolidation process. Backfill materials with high Kaolin content under low consolidation stress were desirable materials for burrier of heat sensitive structures.

Relationships Among pH, Minerals, and Carbon in Soils from Tundra to Boreal Forest Across Alaska

Fri, 01 Jan 2016 00:00:00 GMT

Title: Relationships Among pH, Minerals, and Carbon in Soils from Tundra to Boreal Forest Across Alaska Authors: Satoru Hobara; Noriharu Ae; Lee, Bang Yong; Keisuke Koba; Yongwon Kim; Keiji Kushida Abstract: Tundra and boreal forests in northern high latitudes contain significant amounts of carbon (C) in the soil, indicating the importance of clarifying controls onsoil Cdynamics in the region and their feedback effects on climate systems. In northern Alaska, variations in soil C processes are closely associated with variations in soil acidity within ecosystems;however, the reason for this association remains unclear. In this study, we demonstrate that it results from weathering and subsequent changes in soil geochemical characteristics, including minerals and adsorptive organic C. We sampled soils from 12 sites in Alaska along a 600-km transect from the Arctic Ocean to interior Alaska, spanning the biomes of tundra, tundra？boreal forest ecotone, and boreal forest. Mineral soil analyses revealed that soils with lowpH have fewer base cations, more aluminum/iron minerals, and lower base saturation, indicating that weathering is a major function of these geochemical characteristics in the broad area over northern Alaska. Adsorbed organic C in soil presented strong correlations with Al and Fe minerals, soil pH, and soil total C and represented approximately 30？55% of total soil C, suggesting that soil C accumulation in the Alaskan ecosystems is strongly controlled by weathering-related changes in geochemical characteristics. An adsorption test supported these observations and illustrated a greater capacity for acidic soil to adsorb organic C. These findings demonstrate that variations in weatheringassociated characteristics have a strong influence on the regional variation in C dynamics and biogeochemical consequences in the Alaskan ecosystems.

An analytical system enabling consistent and long-term measurement of atmospheric dimethyl sulfide

Fri, 01 Jan 2016 00:00:00 GMT

Title: An analytical system enabling consistent and long-term measurement of atmospheric dimethyl sulfide Authors: Jang, Sehyun; Suh, Young-Sang; Lee, Kitack; Park, Ki-Tae Abstract: We describe here an analytical system capable of continuous measurement of atmospheric dimethylsulfide (DMS) at pptv levels. The system used customized devices for detector calibration and for DMS trapping and desorption that were controlled using a data acquisition system (based on Visual Basic 6.0/C 6.0) designed to maximize the efficiency of DMS analysis in a highly sensitive pulsed flame photometric detector housed in a gas chromatograph. The fully integrated system, which could sample approximately 6 L of air during a 1-hr sampling, was used to measure the atmospheric DMS mixing ratio over the Atlantic sector of the Arctic Ocean over the 3-full growth periods of phytoplankton in 2010, 2014, and 2015, with minimal routine maintenance and interruptions. During the field campaigns, the measured atmospheric DMS mixing ratio varied over a considerable range, from < 1.5 pptv to maximum levels of 298 pptv in 2010, 82 pptv in 2014, and 429 pptv in 2015. The operational period covering the 3-full growing seasons of phytoplankton showed that the system is suitable for uninterrupted measurement of atmospheric DMS mixing ratios in extreme environments. Moreover, the findings obtained using the system showed it to be useful in identifying ocean DMS source regions and changes in source strength.