Chang-Bok Lee

GEOCHEMISTRY OF SURFACE SEDIMENTS OFF THE SOUTHERN AND WESTERN COASTS OF KOREA

Abstract The continental shelf off the southern and western side of the Korean Peninsula is part of a modern epicontinental sea, and is an effective sediment trap for clastic material derived from China and Korea. We have analyzed 179 surface sediment samples from this shelf for Al, Fe, Na, K, Mg, Ca, Ti, P, Mn, Sr, Ba, V, Cr, Co, Ni, Cu, Zn, organic carbon and calcium carbonate in order to determine the geochemical characteristics of these sediments. Results showed a wide range of element contents which are mainly related to the textural variability of sediments. Exceptions to this were found in the contents of Ca, K, Sr and Ba. The Ca and Sr contents were largely determined by the amounts of carbonate present. The K content, on the other hand, appeared to be influenced by both the contents of illite and feldspar, and Ba, of potassium feldspar. For muds (i.e., sediments deposited under present-day conditions), it is possible to distinguish those in the central Yellow Sea from those in the Keum Estuary: the former are characterized by high contents of Fe, Na, K, Mg, Ca and V, and the latter by high contents of Mn, Ba and Co. These differences become more apparent when these elements are normalized relative to Al in order to minimize grain size effects. The distribution of V/Al ratios is different from that of other elements: the highest V/Al values occur in muds from the central Yellow Sea derived from the Huanghe (the Yellow River in China), whereas the highest values of Mn/Al are found in the nearshore area adjacent to the Korean Peninsula. Based on these results, it is suggested that the sources of fine sediments in the Yellow and South Seas can be distinguished from the geochemical characteristics of the surface sediments. In the Yellow Sea, two different sources of fine-grained sediments can be seen, the Huanghe and the Keum River. The former is characterized by higher V contents and the latter by higher Mn contents. Using the V/Al ratio as an end-member component of the two source materials, the dispersal patterns of the fine sediments (>6O) were also derived.

A mechanism for the enrichment of Cu and depletion of Mn in anoxic marine sediments, Banweol intertidal flat, Korea

Abstract To understand the behaviour of heavy metals in anoxic marine sediments, surface and core sediment samples were collected in the Banweol intertidal flat (BIF) on the west coast of Korea where sulphate reduction occurs actively. Contents of Cu in this area are considerably higher than those in nearshore environments around the Korean peninsula, whereas those of Mn are lower. Copper in the sulphide fraction is enriched in the BIF sediments compared to that in the nearshore environments while Mn in the oxide fraction is depleted. Meanwhile, contents of Ni, Co, Pb and Cd in BIF sediments are comparable to those in the nearshore environments. The above results suggest that the precipitation of copper sulphide and the dissolution of manganese oxide are responsible for the enrichment of Cu and the depletion of Mn, respectively, in the highly anoxic BIF sediments. Hence, aratio of Cu/ Mn is regarded as an appropriate indicator of diagenetic influence in anoxic marine sedimentary environments.

REE geochemistry of suspended sediments from the rivers around the Yellow Sea and provenance indicators

Rare earth element (REE) compositions of the suspended sediments from the rivers around the Yellow Sea were different in that Korean river sediments (Han, Keum and Yeongsan Rivers) yield stronger fractionations than Chinese river sediments (Changjiang, Huanghe and Yalujiang), shown by obvious enrichments of LREE (light rare earth element) relative to UCC (upper continental crust). Variations of source rock compositions in the drainage basins are responsible for the differences of REE compositions between the river sediments. REE fractionation parameters including (La/Yb)UCC and (Gd/Yb)UCC as well as the ratios of La/Sc and Th/Sc can be treated as proper proxies for identifying the Chinese river sediments from those Korean river matters, and furthermore, for studying the provenances and paleoenvironmental changes of the marginal seas of China.

Atmospheric metal and phosphorus concentrations, inputs, and their biogeochemical significances in the Japan/East Sea.

Atmospheric metals and phosphorus over the southern Japan/East Sea were investigated in order to evaluate their sources, concentrations and inputs, and to identify their biogeochemical roles in this marginal sea. Aerosols were collected on the east coast of Korea from February 2002 to April 2003 (n=101) as well as at a remote island (Ulleung) and on a ship from February 2002 to June 2003 (n=13). The aerosols were analyzed for Al, Co, Cu, Ni, P, Pb and Zn. Simultaneous collections of aerosols at both coast and offshore were performed, and several high dust aerosols (Al>5 microg m(-3)) were collected at both regions. At the coastal site, both dust mineral and pollutants were transported by westerly winds from the Asian continent, but local emissions were significant (e.g., Cu, Ni, P and Zn) as well during the summer monsoon (May-August). The experimental relationships between the coast and offshore sites were defined. From these relationships, it was possible to obtain the annually averaged atmospheric metal and P concentrations over the southern Japan/East Sea, which has increased by over 2 times for the last decade. Through the estimation of atmospheric metal and phosphorus fluxes and comparisons with inputs from the Tsushima Warm Current, the atmospheric pathway was found to be a significant source for Al, Pb and Zn.

Atmospheric transport of water-soluble ions (NO3−, NH4+ and nss-SO42−) to the southern East Sea (Sea of Japan)

Atmospheric deposition of different types of aerosols over the southern East Sea has received little attention in terms of seawater biogeochemistry. We investigated the concentrations of water-soluble ions (NO3(-), NH4+ and nss-SO4(2-)) in the aerosols associated with air mass transport patterns arriving at the east coast of Korea, adjacent to the southern East Sea, in order to determine source regions affecting chemical composition of aerosols and to assess the atmospheric pathway as a significant controlling mechanism of the biogeochemistry in this marginal sea. Concentrations of certain elements (Al, Na, Ca, V, Zn and Pb) together with the water-soluble ions were measured in the aerosol samples (n=34) collected during the period March 2002-February 2003. The geometric mean concentrations of the water-soluble ions were NO3(-) 2.98 (0.56-16.22), NH4+ 1.42 (0.37-6.73) and nss-SO4(2-) 2.47 (0.17-17.35) microgm(-3). The backward trajectories revealed that air masses passing slowly over eastern China contributed more to increases in the concentrations of water-soluble ions than those associated with fast-moving northwesterly and maritime winds. Therefore, the correlation between the NH4+ and NO3+ concentrations increased, suggesting that gas-phase NH3 and HNO3 was forming fine-mode NH4NO3. The atmospheric N input accounted for approximately 10% of new production over the southern East Sea on an annual scale, while it accounted for over approximately 25% of new production during the water column stratification seasons (summer and early fall).

GEOCHEMICAL AND MINERALOGICAL CHARACTERISTICS IN TWO-COLOR CORE SEDIMENTS FROM THE KOREA DEEP OCEAN STUDY (KODOS) AREA, NORTHEAST EQUATORIAL PACIFIC

Abstract At sites 89 and 90 of the Korea Deep Ocean Study (KODOS), located in the western part of the area between the Clarion and Clipperton fracture zones, the topmost sediment column can be divided into two layers by a sharp color boundary: an upper pale brown layer (Unit A) and a lower dark brown layer (Unit B). Geochemical and mineralogical properties in Units A and B are clearly different across the color boundary, which can be interpreted to be a hiatus with an age gap of at least 3 Ma. The large gap in sediment ages results in an overall difference in sediment properties between Units A and B. That is, older Unit B sediment is higher in smectite contents, more severe in fossil dissolution, and lower in POC contents, commonly due to prolonged diagenesis. Disappearance of the coarse mode (50–60 μm) of the size distribution in Unit B is a result of prolonged dissolution of siliceous fossils. However, other phenomena occurring just below the color boundary (the most severe dissolution of fossils, the most frequent occurrence of coarse-grained micronodules and smectite aggregates, maximum value of metals (Mn, Cu, Ni), and increased water contents) can be explained by the active stirring of bottom sediments by intensified paleo-bottom currents present during the hiatus. That is, turbulence as well as winnowing action caused by the paleo-currents had, respectively, accelerated the dissolution of siliceous fossils and the concentration of coarse grains at the hiatus. In addition, micronodule formation was promoted by the efficient formation of oxygen-depleted micro-environments around in-situ fauna remains, which were buried efficiently by increased reworking and resedimentation of bottom sediments by the paleo-current activity. Meanwhile, increases in metal and water contents just below the color boundary are the results of the concentration of micronodules enriched in metals and probable formation of ‘woodpile’ fabric by abundant spicules and spines, respectively. Active stirring of bottom sediments by the intensified paleo-bottom currents as well as the large gap in sediment age between Units A and B are mostly responsible for the vertical variations of geochemical and mineralogical properties in two-color core sediments.

Growth of diagenetic ferromanganese nodules in an oxic deep-sea sedimentary environment, northeast equatorial Pacific

Abstract To study the accretion mechanism of diagenetic ferromanganese nodules formed in an oxic deep-sea sedimentary environment, manganese nodules, sediments, and pore waters were sampled in the northeast equatorial Pacific. Diagenetic ferromanganese nodules are ellipsoidal to discoidal in shape, rough in surface texture, enriched in Cu, Ni and 10 A-manganite, and are ubiquitous on the abyssal plain; hydrogenetic nodules are polynucleated, irregular in shape, smooth in surface texture, enriched in Co and δ-MnO 2 , and occur dominantly on seamounts. Numerous microlayers with diagenetic or hydrogenetic characteristics occur successively in the nodules. Concentration of nitrate in sediment pore waters indicates that overall redox conditions are oxic. However, Mn-oxide grains on the walls of burrows and worm tubes are interpreted to be reprecipitated metal ions supplied from oxygen-depleted microenvironments that formed in the oxic sediment column by decomposition of organic matter. Active mixing of bottom sediments by benthic fauna and bottom currents is indicated by ubiquitous burrows, worm tubes, and tracks and trails, high values in sediment mixing coefficients (>1 cm 2 /yr), and scattering of data points in depth profiles of pore water nitrate concentrations. We suggest that diagenetic ferromanganese nodules in an oxic deep-sea sedimentary environment grew from remobilized metal ions as well as reprecipitated Mn-oxide grains, which were supplied to the nodules episodically during the stirring of bottom sediments by benthic fauna and intermittent strong bottom current flow.

Nationwide monitoring of mercury in wild and farmed fish from fresh and coastal waters of Korea

Mercury (Hg) concentrations were monitored in wild and cultured fish collected from fresh and coastal waters in the Korean peninsula from April 2006 to August 2008 nationwide. Total Hg concentrations were reported for 5043 fish samples, including 78 species from 133 locations. Significant interspecies variation was noted in the Hg levels. The average Hg concentration in each fish species ranged from 6.31 μg kg(-1) for mullet (Mugil cephalus) to 200 μg kg(-1) for mandarin fish (Siniperca scherzeri). Among the species collected, the maximum concentration of Hg, 1720 μg kg(-1), was measured in an Amur catfish (Silurus asotus). Only wild freshwater fish exceeded the WHO ingestion standard. Wild freshwater piscivorous fish samples from a large artificial upstream lake contained the highest Hg levels. Hg concentrations were compared between fish groups categorized as wild and farmed fish from freshwater and coastal waters. Although the wild freshwater fish had similar size ranges, their Hg concentrations were higher than those of the other groups. Compared to the feed of farmed marine and freshwater fishes, the prey of wild freshwater fish had a higher Hg concentration, and the total Hg concentrations in freshwater and associated sediment samples were higher than those in coastal water and associated sediment samples. In the freshwater environment, piscivorous fish bioaccumulated two times more Hg than carnivorous and omnivorous fish and four times more than planktivorous fish. The difference in Hg concentrations among trophic groups might have been due to differences in the size of fish, in addition to the variations among different trophic groups. These data will be useful for developing the fish consumption advisory as a management measure to reduce Hg exposure.

Heavy Metal Contamination in Surface Sediments from Masan and Jinhae Bay, Southeast Coast of Korea

Concentrations of selected heavy metals (Al, Fe, Mn, Cr, Cu, Ni, Zn, Pb, As and Cd) in surface sediments from 96 sites in Masan and Jinhae Bay were studied in order to understand metal contamination. Results show that the surface sediments were mainly enriched by Cu (18-294 ppm), Zn (67-568 ppm), Pb (10-120 ppm) and Cd (0.2-3.5 ppm). The coastal zone of Masan Bay was significantly more contaminated than the non-coastal zone, and spatial distribution pattern suggested additional sources of heavy metal input in the coastal area. The enrichment ratio and geoaccumulation index () have been calculated and the relative contamination levels assessed in the study area. The enrichment ratios of Cu, Zn, Pb and Cd in Masan Bay have been observed to be relatively high. results reveal that the study area is not contaminated with respect to Fe, Mn, Cr and Ni; moderately to strongly contaminated with Cu, Zn and Pb; and strongly to strong contaminated with Cd. The high contents of Cu, Zn, Pb and Cd in the study area result from anthropogenic activities in the catchment area. Based on the eight different sediment quality guideline values from USA (ERL, ERM), Canada (TEL, PEL), Australia/New Zealand (ISQG-high, ISQG-low) and Hong Kong (ISQV-low, ISQV-high), sediment quality of Masan and Jinhae Bay was also assessed and characterized.

Trace metals (Co, Ni, Cu, Cd, and Pb) in the southern East/Japan Sea

Total dissolvable metals (Co, Ni, Cu, Cd, and Pb) in both surface waters and the water columns were acquired in the southern East/Japan Sea during a cruise around the Ulleung Basin in June 2001 to understand the spatial distributions of the metals. Concentrations in offshore surface waters were found to be Co 60 ± 12 pM, Ni 2.16 ± 0.25 nM, Cu 1.85 ± 0.55 nM, Cd 0.134 ± 0.018 nM, and Pb 155 ± 40 pM. Spatial distributions in surface waters showed that metal levels were generally enhanced at coastal sites in both Korea and Japan, where the metal distributions indicated complex patterns due to inputs, biogeochemical processes, and physical factors including upwelling. The Co distributions in the water columns seemed to be influenced predominantly by surface and bottom inputs, scavenged rather than regenerated at depth. For Cd, there was generally good agreement between the Cd and PO4 depth distributions, in agreement with the literature. The Cd/PO4 ratio from the water columns was found to be 0.133–0.203, lower than that in other marginal seas (e.g. the East/South China Seas and the Philippine Sea) of the western Pacific Ocean; this might be a result of the fast ventilation rate in this sea. The vertical Pb profile showed typical scavenged-type behavior with a surface maximum and deep minimum. From a comparison of inputs from the atmosphere and the Tsushima Warm Current, atmospheric deposition is substantial enough that it cannot be ignored, and its role in metal cycling is more significant in the offshore zone.