• Journal of Forest and Environmental Science
• /
• v.34 no.4
• /
• pp.321-337
• /
• 2018

The characteristics of 124 Phytolacca americana present areas and 88 surrounding absent areas over the country were investigated and compared from July 2016 to Sept 2017. The Phytolacca americana was confirmed as having been nationally distributed and is usually found in roadsides at an altitude of 380 m (26%), forest edges (24%), forests (19%), sunny spots (60%), dry soils (53%), sandy loams (31%) and sand+gravel soils (22%). 321 taxons consisting of 79 families, 209 genera, 289 species, 2 subspecies, 26 varieties and 4 cultivars and 286 taxons consisting of 76 families, 195 genera, 256 species, 2 subspecies, 24 varieties and 4 cultivars were found in the Phytolacca americana present areas and the absent areas, respectively. The relative net contribution degree was found highest in the Phytolacca americana (100) followed by Robinia pseudoacacia (29.4), Humulus japonicus (8.8) and Artemisia princeps (6.0) in the present areas, while it was found highest in Robinia pseudoacacia (100) followed by Humulus japonicus (44.4), Artemisia princeps (35.9), Pueraria lobata (18.6) and Setaria viridis (12.3) in the absent areas. The Raunkier's life form in the present/absent areas was found highest in the therophytes (34%/34%), followed by hemicryptophytes (17%/18%), megaphanerophytes and mesophanerophytes (18%/17%), nanophanerophytes (11%/11%) and geophytes (9%/11%). There was no significant difference in the species diversity between the present (2.141) and the absent (2.124) areas. However, the allelopathic agent and light blocked-out by the Phytolacca americana could possibly inhibit germination and the development of other species; especially, where a difference in species diversity was found high in forests, compared to other habitats (p=0.0605). Accordingly, it is suggested to review possible disturbances of native species habitats in shady spots including forest gaps, although the effect of Phytolacca americana on the ecological system in the suburban open and disturbed areas is not large.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.31 no.6C
• /
• pp.213-220
• /
• 2011

Fines such as silt or clay are usually mixed with granular particles in natural or reclaimed soils which are slightly cemented. Such fines contained within weakly cemented soils may influence permeability and also mechanical behavior of the soils. In this study, a series of unconfined compression tests on weakly cemented sands with fines are carried out in order to evaluate the effect of fines on unconfined compressive strength (UCS) of cemented soils. Two different cement ratios and fine types were used and fine contents varied by 5, 10, and 15%. Two types of specimens were prepared in this testing. One is the specimen with the same compaction energy applied. The other is the one with the same dry density by varying compaction energy. When the same amount of compaction energy was applied to a specimen, its density increased as a fine content increased. As a result, the UCS of cemented soils with fines increased up to 2.6 times that of one without fines as an amount of fines increased. However, when the specimen was prepared to have the same density, its UCS slightly decreased and then increased a little as a fine content increased. Under the same conditions, a UCS of the specimen with silt was stronger than the one with kaolin. As a cement ratio increased, a UCS increased regardless of fine type and content.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.9 no.1
• /
• pp.61-70
• /
• 2007

This study was conducted to investigate nutrient dynamics and water quantity of throughfall and stemflow in natural oak stands in Korea. The ratio of the total throughfnll and stemflow to the amount of precipitation varied with locations. It was considered that the ratio was affected not only by the characteristics of tree species but also by regional, weather and other environmental conditions. It was, therefore, necessary to set up a water control system to launch a tending project for natural oak stands. Comparisons of nutrient amount in throughfall among regions reflected regional characteristics. $Ca^{2+},\;Mg^{2+}$ and $K^+$ ions were leached from the canopy and yellow sand accumulation. $Na^+$ and $Cl^-$ were marine-borne. $NO_3^-$ and $SO_4^{2-}$ resulted from dry deposition of air pollutants. Nutrient amount in the stemflow was as low as about 10% of that in the total throughfall and stemflow. The pH of stemflow in natural oak stands in urban areas ranged from 3 to 5. Influx of the acidic stemflow to soil could, in the long term, affect pH in soil solution and nutrient dynamics around root zones.

• Korean Journal of Environmental Biology
• /
• v.37 no.4
• /
• pp.607-617
• /
• 2019

This study examined the habitat distribution characteristics of Aquatic Oligochaeta according to the construction of weirs in the four major rivers in South Korea. The area was investigated 10 times from March to October in 2018 and a total of 18 species and 35,390 ind. m^-2 were sampled. The dominant species by number was Limnodrilus hoffmeisteri(77.1%) and the subdominant species was Branchiura sowerbyi(9.5%). A total of 32.418 g m^-2 dry weight was analyzed. The correlation analysis showed that the number of Aquatic Oligochaeta individuals correlated with the sediment depth, clay ratio, silt ratio, sand ratio, cobble ratio, pebble ratio, pH and TOC mg L^-1. Specifically, the clay ratio and sediment depth were associated with increases in the number of individuals. The total organic carbon(TOC) increased from March to October and, conversely, the number of individuals tended to decrease.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.45 no.1
• /
• pp.117-126
• /
• 2017

This study was carried out to figure out on the changes of longitudinal salt movement in the soil through the soil according to the materials and thickness of salt prevent materials and the place of salt prevent at reclaimed land from the sea which is one of the most serious problems when tree planting. Changes of soil salinity were different depending on the seasons. In particular, the soil salinity was lower during the rainy season. But during the dry seasons including early summer before the rainy season and winter season, salinity was relatively higher. Among the seven interruption materials, crushed stone, dredged sand and wood chips showed better interruption effects than the other materials. The interruption effect of salt movement was highest in the both of side and bottom interruption treatment of salt movement than the side interruption treatment of salt movement or the bottom interruption treatment of salt movement. The thickness of the layer should be at least 20cm to prevent salinity effectively.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.10 no.2
• /
• pp.132-139
• /
• 2002

This study was carried out to investigate the effects of aging and soil texture on composting of diesel-contaminated soil. The soils used for this study were silt loam and sand. Target contaminant, diesel oil, was spiked at 10,000mgTPH/kg of dry soil. Aging times of diesel-contaminated soils were 15days and 60days, respectively. Fresh diesel-contaminated soil was also investigated. Moisture content was controlled to 70% of soil field capacity. Mix ratio of soil to sludge was 1:0.3 as wet weight basis. Temperature was maintained at $20^{\circ}C$ Volatilization loss of TPH was below 2% of initial concentration. n-Alkanes lost by volatilization were mainly by the compounds of C10 to C17. Diesel in contaminated soil was mainly removed by biodegradation mechanism. First order degradation rate constant of TPH in sandy soil was ranged from 0.081 to 0.094/day, which is higher than that in silt loam(0.056-0.061/day). From fresh to 60day-aged soils, there was little difference of TPH biodegradation rate between the soils. Carbon recovery ranged from 0.61 to 0.89. TPH degradation rate was highly correlated with $CO_2$ production rate.

• Journal of Convergence for Information Technology
• /
• v.10 no.7
• /
• pp.153-159
• /
• 2020

In order to find out the condition of flow in sewer pipes, this study investigated the characteristics of tractive force of sewage flow estimated using actual measured values of water level, velocity, and flowrate in sewers located at uppermost portion in a treatment area during dry weather periods. When the scene of sewage flow was taken by CCTV after cohesive and non-cohesive solids (tofu and sand) were put on the sewer invert, it was found that the solids could be flushed without significant interruption. In sewer with slope of 0.00319, the frequency exceeding the minimum tractive force of sewage during a weekday was zero, while it was 10 per day with slope of 0.00603. During the week of the field observation, the event to exceed the minimum tractive force occurred once, suggesting that sewer odor would potentially increase. Maximum tractive force in sewer with steep slope was 2.9-3.1 N/㎡, but with gentle slope it decreased to 1.6-1.7N/㎡. It was also observed that the interval of time maintained below the criterion of minimum tractive force increased, during weekends compared to weekdays and for the sewage including non-cohesive particles which could enter combined sewers during a storm period. This study found that the sewer sediments formed by direct feces input into sewers, through sewer pipes which were designed meeting the standard sewer design criteria, could be flushed without staying as deposited solids state for a long time.

• The Korean Journal of Ecology
• /
• v.27 no.6 s.122
• /
• pp.355-361
• /
• 2004

In order to elucidate the ecophysiological characteristics of coastal plants, we collected them on salt marsh and sand dune, and analyzed inorganic ($Na^+,\;K^+,\;Mg^{2+},\;Ca^{2+}$) and organic solutes (soluble carbohydrate, glycine betaine). Chenopodiaceous plant species (Atriplex gmelini, Salicornia europaea, Salsola collina, Suaeda glauca, Suaeda japonica) showed a tendency to accumulate inorganic ions such as $Na^+\;and\;Cl^-$ instead of $K^+$. However, Chenopodium serotinum which lives in ruderal habitat contained more $K^+$ and less $Na^+$ than the other Chenopodiaceous plants. Most Chenopodiaceous plant species maintained very low level of soluble $Ca^{2+}$ and relatively low concentration of carbohydrates and showed high concentration of glycine betaine which is among the most effective known compatible solutes in the leaves of plant under drought and saline conditions. On the other hand, plant species which belong to Gramineae (Ishaemum anthephoroides, Phragmites communis, Zoysia sinica) and Cyperaceae (Carex kobomugi, Carex pumila) absorbed $K^+$ selectively and excluded $Na^+\;and\;Cl^-$ effectively regardless of habitat conditions, and they accumulated more soluble carbohydrate as osmoticum than Chenopodiaceous plants. These results suggested that physiological characteristics such as high storage capacity for inorganic ions (especially alkali cations, chloride) and the accumulation of glycine betaine in chenopodiaceous plants and $K^+$-preponderance, an efficient regulation of ionic uptake (exclusion of $Na^+\;and\;Cl^-$) and the accumulation of soluble carbohydrate in monocotyledonous plants enable them to grow dry and saline habitats.

• Journal of the Korean GEO-environmental Society
• /
• v.19 no.11
• /
• pp.23-30
• /
• 2018

According to recent ground collapse occurrence, ground subsidence is increasing every year in downtown area, which is a social problem. The purpose of this study is to investigate the relationship between ground water level lowering and ground collapse through laboratory model experiments. After mixing 1:1 granite weathered soil with sand, sandy soil was formed as a relative density of 30%, 50%, and 80%. And then the changes of soil discharge with change of groundwater level were compared. The physical property of material of which particle distribution were well graded with maximu dry unit weight of $1.94kg/cm^3$ and internal friction angle of 37degrees. Ground water levels were measured at 10 cm, 20 cm, and 30 cm from the bottom. As a result, the experiment shows that the higher the groundwater level works the higher the discharge velocity and the magnitude of underground cavity also increases with elapsed time. Finally, the cumulative quantity of soil discharge occurred up to 30 kg at the elapsed time, 35 minutes. It was also confirmed that the range of ground collapse increased due to soil discharge with ground water level lowering.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.55 no.2
• /
• pp.133-138
• /
• 2010

This study was conducted to analysis a major cause of rice yield reduction in 4 research points, 1, 2, 3, and 5km, from coastline in the East Sea. There were great changes of temperature in each research point, though the average temperature a day was no difference between each research point. Each temperature in 1, 2, and 3km research points was 8, 7, and $4^{\circ}C$ lower than in 5km when cold salty wind was generated due to cold pool. As it was close in coastline, its soil was abundant sand components, little silt and clay soil components and lacking in cation exchange capacity(CEC). And plant height became a smaller, heading date was delayed for 3～4 days, and dry weight was reduced. Also, it was to be down percent of fertile grain. As cultivation site was close in seaside, its decline was larger because of reduction of panicle number per hill. It was "Samdeogbyeo" that was variety adapted in cold salty wind, having yield potential more than 90% in 2km.