Increased As load to the Uchen stream due to mine drainage and soils in the abandoned Kangwon mining district of Korea

To determine the appropriate allocation of resources for the future restoration of the abandoned mining district of Kangwon in Korea, identification of the main pollutants and the main sources discharging these pollutants is crucial. Therefore, a 2-year study was undertaken to quantify the amount of pollutants in the Uchen stream (a potential sink for contamination), which runs through the district, and to determine the potential sources of these pollutants, including mine drainage and soil. Arsenic (As) was the main pollutant in mine drainage and soils showing concentrations above the Korean regulated standard levels of 50 μg L⁻¹ and 50 mg kg⁻¹ for water and soil, respectively. In addition, the pollution index (PI) showed that mine drainages were polluted by As to a moderate (2 ≤ PI < 3) or strong (4 ≤ PI < 5) degree. Consequently, As load in mine drainage and soil contributed to increased amounts of As in the stream. The As loads in mine drainages (11 and 587 g month⁻¹ for mine adit 1 and 2, respectively) accounted for only 9% of the total As load to the stream (6,378 g month⁻¹); and the influence of mine drainages on As contents in the stream was more reliant on the total volume of mine drainage generated rather than the As concentration in the mine drainage. Approximately 91% of the As in the stream was derived from the soils within the study area.     

Examining potential genetic links between Jurassic porphyry Cu–Au ± Mo and epithermal Au ± Ag mineralization in the Toodoggone district of North-Central British Columbia,Canada

The Toodoggone district comprises Upper Triassic to Lower Jurassic Hazelton Group Toodoggone Formation volcanic and sedimentary rocks, which unconformably overlie submarine island-arc volcanic and sedimentary rocks of the Lower Permian Asitka Group and Middle Triassic Takla Group, some of which are intruded by Upper Triassic to Lower Jurassic plutons and dikes of the Black Lake suite. Although plutonism occurred episodically from ca. 218 to 191 Ma, the largest porphyry Cu–Au ± Mo systems formed from ca. 202 to 197 Ma, with minor mineralization occurring from ca. 197 to 194 Ma. Porphyry-style mineralization is hosted by small-volume (<1 km³), single-phase, porphyritic igneous stocks or dikes that have high-K calc-alkaline compositions and are comparable with volcanic-arc granites. The Fin porphyry Cu–Au–Mo deposit is anomalous in that it is 16 m.y. older than any other porphyry Cu–Au ± Mo occurrence in the district and has lower REEs. All porphyry systems are spatially restricted to exposed Asitka and Takla Group basement rocks, and rarely, the lowest member of the Hazelton Group (i.e., the ca. 201 Ma Duncan Member). The basement rocks to intrusions are best exposed in the southern half of the district, where high rates of erosion and uplift have resulted in their preferential exposure. In contrast, low- and high-sulfidation epithermal systems are more numerous in the northern half of the district, where the overlying Hazelton Group rocks dominate exposures. Cogenetic porphyry systems might also exist in the northern areas; however, if they are present, they are likely to be buried deeply beneath Hazelton Group rocks. High-sulfidation epithermal systems formed at ca. 201 to 182 Ma, whereas low-sulfidation systems were active at ca. 192 to 162 Ma. Amongst the studied epithermal systems, the Baker low-sulfidation epithermal deposit displays the strongest demonstrable genetic link with magmatic fluids; fluid inclusion studies demonstrate that its ore fluids were hot (>468°C), saline, and deposited metals at deep crustal depths (>2 km). Sulfur, C, O, and Pb isotope data confirm the involvement of a magmatic fluid, but also suggest that the ore fluid interacted with Asitka and Takla Group country rocks prior to metal deposition. In contrast, in the Shasta, Lawyers, and Griz-Sickle low-sulfidation epithermal systems, there is no clear association with magmatic fluids. Instead, their fluid inclusion data indicate the involvement of low-temperature (175 to 335°C), low-salinity (1 to 11 equiv. wt.% NaCl) fluids that deposited metals at shallow depths (<850 m). Their isotope (i.e., O, H, Pb) data suggest interaction between meteoric and/or metamorphic ore fluids with basement country rocks.     

What is responsible for increasing flood risks? The case of Gangwon Province,Korea

We examined the anthropogenic and natural causes of flood risks in six representative cities in the Gangwon Province of Korea. Flood damage per capita is mostly explained by cumulative upper 5% summer precipitation amount and the year. The increasing flood damage is also associated with deforestation in upstream areas and intensive land use in lowlands. Human encroachment on floodplains made these urban communities more vulnerable to floods. Without changes in the current flood management systems of these cities, their vulnerability to flood risks will remain and may even increase under changing climate conditions.     

Hydrogeochemical characterization of major factors affecting the quality of shallow groundwater in the coastal area at Kimje in South Korea

This study has evaluated the main hydrogeochemical characteristics that affect the quality of shallow groundwater in the coastal area at Kimje in South Korea. In this area, the chemical composition of groundwater is mostly classified into Na⁺?Cl^? and Ca²⁺+Mg²⁺?NO₃^-+Cl^? types. These types are affected by three major factors: seawater intrusion, fertilizers and redox processes. The Na⁺?Cl^? type, which is generally localized in the coastal area, shows typical characteristics of groundwater affected not only by modern seawater but also by old seawater residing in the reclaimed land. In contrast, the Ca²⁺+Mg²⁺?NO₃^-+Cl^? type, which is usually found inland, is very contaminated by fertilizers. As groundwater flows from the inland area to the coast, the redox condition changes from an oxic condition to a suboxic/anoxic condition. In addition, the reclamation has caused a large amount of underlying organic matter. These effects provide optimum conditions for the occurrence of redox processes in the coastal area.     

Effects of natural and calcined oyster shells on Cd and Pb immobilization in contaminated soils

In Korea, soils adjacent to abandoned mines are commonly contaminated by heavy metals present in mine tailings. Further, the disposal of oyster shell waste by oyster farm industries has been associated with serious environmental problems. In this study, we attempted to remediate cadmium (Cd)- and lead (Pb)-contaminated soils typical of those commonly found adjacent to abandoned mines using oyster shell waste as a soil stabilizer. Natural oyster shell powder (NOSP) and calcined oyster shell powder (COSP) were applied as soil amendments to immobilize Cd and Pb. The primary components of NOSP and COSP are calcium carbonate (CaCO₃) and calcium oxide (CaO), respectively. X-ray diffraction, X-ray fluorescence and scanning electron microscope analyses conducted in this study revealed that the calcination of NOSP at 770°C converted the less reactive CaCO₃ to the more reactive CaO. The calcination process also decreased the sodium content in COSP, indicating that it was advantageous to use COSP as a liming material in agricultural soil. After 30 days of incubation, we found that the 0.1 N HCl-extractable Cd and Pb contents in soil decreased significantly as a result of an increase in the soil pH and the formation of metal hydroxides. COSP was more effective in immobilizing Cd and Pb in the contaminated soil than NOSP. Overall, the results of this study suggest that oyster shell waste can be recycled into an effective soil ameliorant.     

Geostatistical integration using 2-D electrical resistivity and 3-D gravity methods for detecting cavities in a karst area

Two-dimensional (2-D) electrical resistivity and three-dimensional (3-D) gravity explorations were undertaken to estimate the 3-D distribution of karst cavities at the area of Yongweol-ri in Korea where ground subsidence has occurred. Although the gravity method is a low-cost way of analyzing a 3-D continuous structure, its vertical resolving power is poor. In contrast, the electrical resistivity method can provide a 2-D and/or 3-D subsurface structure with a much higher lateral and vertical resolution than the gravity method. Accordingly, geostatistical methods and density information were used to enhance the 2-D resistivity structure revealed by the electrical resistivity method into a 3-D structure. The assumptions are, first, that each data set senses the same underlying geological structure in terms of different material properties and, secondly, that two different material properties are correlated locally or globally throughout the entire target area. As a result, the distribution of limestone cavities can be estimated under the assumption that they are mostly filled with groundwater and clayey soils and have abnormally low levels of resistivity and density. The estimated distribution corresponds with the grouting, borehole imaging and monitoring data. In this example, it can be seen that the integration analysis of 2-D electrical resistivity and 3-D gravity methods is a very powerful tool for 3-D subsurface imaging and that the method can provide enhanced imaging capabilities for 3-D cavities.     

Interannual and long-term variation in the nearshore fish community of the mesohaline Hudson River estuary

The detection of long-term shifts in species composition and spatial structuring of aquatic communities may be obscured by high levels of interannual variation. Estuarine fish communities are likely to exhibit high levels of variation owing to the influence of riverine forcing and the importance of anadromous and transient species, whose abundances may not be locally controlled. We describe patterns of interannual variation and long-term shifts in the nearshore fish community of the mesohaline Hudson River estuary based on 21 yr of beach seine sampling conducted annually between late August and mid November. Of the 60 species encountered, the most abundant were Atlantic silversides (Menidia menidia), striped bass (Morone saxatilis), white perch (Morone americana), American shad (Alosa sapidissima), and blueback herring (Alosa aestivalis). Relationships between annual community composition and seasonal flow and temperature regimes were examined with canonical correspondence analysis. Annual variation was most closely correlated with river flows in the 3-mo period preceding fish sampling, indicating a persistent effect of environmental conditions on community structure. Despite significant interannual variation in composition, longer-term trends in community structure were observed. These included declines in catch rates of freshwater and estuarine species and a dramatic increase in the catch of Atlantic silversides, an annual marine species. Associated with these changes were declines in community diversity and increased compositional variation. These results indicate that analyses of temporal changes in community structure need to account for the multiple time scales under which forcing factors and community composition vary.     

Development and application of a GIS-based tool for earthquake-induced hazard prediction

An integrated GIS-based tool (GTIS) was constructed to estimate site effects related to the earthquake hazards in the Gyeongju area of Korea. To build the GTIS for the study area, intensive site investigations and geotechnical data collections were performed and a walk-over site survey was additionally carried out to acquire surface geo-knowledge data in accordance with the procedure developed to build the GTIS. For practical applications of the GTIS used to estimate the site effects associated with the amplification of ground motion, seismic microzoning maps of the characteristic site period and the mean shear wave velocity to a depth of 30 m were created and presented as a regional synthetic strategy addressing earthquake-induced hazards. Additionally, based on one-dimensional site response analyses, various seismic microzoning maps for short- and mid-period amplification potentials were created for the study area. Case studies of seismic microzonations in the Gyeongju area verified the usefulness of the GTIS for predicting seismic hazards in the region.     

Coastal environmental assessment and management by ecological simulation in Yeoja Bay, Korea

An eco-hydrodynamic model was used to estimate the carrying capacity of pollutant loads and response of water quality to environmental change in Yeoja Bay, Korea. An energy-system model also was used to simulate the fluctuation in nutrients and organic matter in the bordering wetland. Most water quality factors showed a pulsed pattern, and the concentrations of nutrients and organic matter of seawater increased when input loads of nutrients increased due to freshwater discharge. The well-developed tidal zones and wetlands in the northern area of the bay were highly sensitive to input loads. Residence times of water, chemical oxygen demand (COD), and dissolved inorganic nitrogen (DIN) within the bay were estimated to be about 16 days, 43.2 days, and 50.2 days, respectively. Water quality reacted more sensitively to the effects of nitrogen and phosphorus input than to COD. A plan to reduce the present levels of COD and dissolved inorganic phosphorus (DIP) by 20–30% and DIN by at least 50% in pollutant loads is needed for satisfying the target water quality criteria. The natural removal rate of nutrients in wetlands by reeds was assessed to be approximately 10%.