Ecotoxicological evaluation of sewage sludge using bioluminescent marine bacteria and rotifer

Bioassay using the marine bacteria,Vibrio fischeri and rotifer,Brachionus plicatilis, and chemical analyses were conducted to assess the toxicity of the various sewage sludges, one of the major ocean dumped materials in the Yellow Sea of Korea. Sludge elutriates extracted by filtered seawater were used to estimate the ecotoxicity of the sludge. Chemical characterization included the analyses of organic contents, heavy metals, and persistent organic pollutants in sludge. Bacterial bioluminescent inhibition (15 min), rotifer mortality (24 hr) and rotifer population growth inhibition (48 hr) assay were conducted to estimate the sludge toxicity. EC50 15 min (inhibition concentration of bioluminescence after 15 minutes exposed) values by Microtox® bioassay clearly revealed different toxicity levels depending on the sludge sources. Highest toxicity for the bacteria was found with the sludge extract from dyeing waste and followed by industrial waste, livestock waste, and leather processing waste. Clear toxic effects on the bacteria were not found in the sludge extract from filtration bed sludge and rural sewage sludge. Consistent with Microtox® results, rotifer neonate mortality and population growth inhibition test also showed highest toxicity in dyeing waste and low in filtration bed and rural sewage sludge. High concentrations of persistent organic pollutants (POPs) and heavy metals were measured in the samples from the industrial wastes, leather processing plant waste sludge, and urban sewage sludge. However, there was no significant correlation between pollutant concentration levels and the toxicity values of the sludge. This suggests that the ecotoxicity in addition to the chemical analyses of various sludge samples must be estimated before release of potential harmful waste in the natural environment as part of an ecological risk assessment.     

Evaluation of typhoon‐induced rainfall using nonparametric Monte Carlo simulation and locally weighted polynomial regression

Typhoons in Korea are the major causes of natural disasters in the Korean peninsula. In this study, rainfall generated by typhoons was quantitatively analysed using various statistical methods. First, the frequency analysis of rainfall induced by typhoons was carried out to calculate the design rainfall. Second, the frequency analysis of simulated rainfall derived by nonparametric Monte Carlo simulation (NMCS) was performed to evaluate the uncertainty of rainfall caused by typhoons. Third, the regression relationship between the physical characteristic factors of typhoons and rainfall was established by locally weighted polynomial regression (LWPR), and the characteristic factors of typhoons were simulated. The simulated characteristic factors were then used to estimate rainfall and to calculate the design rainfall by typhoons. Comparative analyses of design rainfalls as estimated using various statistical methods were performed. The LWPR showed good performance in terms of reproducing typhoon characteristics. Therefore, the combined NMCS and LWPR method suggested in this study can be used as a supplementary technique for assessing extreme rainfall with climate change and reflected variability. Copyright © 2010 John Wiley & Sons, Ltd.     

Diagenesis of oxyanions (V, U, Re, and Mo) in pore waters and sediments from a continental margin

This research tests the hypothesis that trace metals respond to the extent of reducing conditions in a predictable way. We describe pore water and sediment measurements of iron (Fe), manganese (Mn), vanadium (V), uranium (U), rhenium (Re), and molybdenum (Mo) along a transect off Washington State (USA). Sediments become less reducing away from the continent, and the stations have a range of oxygen penetration depths (depth to unmeasurable O₂ concentration) varying from a few millimeters to five centimeters. When oxygen penetrates ∼1 cm or less, Fe is reduced in the pore waters but reoxidized near the sediment-water interface, preventing a flux of Fe²⁺ to overlying waters, whereas Mn oxides are reduced and Mn²⁺ diffuses to overlying waters. Both Re and U authigenically accumulate in sediments. Only at the most reducing location, where the oxygen penetrates 0.3 cm below the sediment-water interface, does the surface 30 cm of sediments become reducing enough to authigenically accumulate Mo.Stations in close proximity to the Juan de Fuca Ridge crest are enriched in Mn and Fe from hydrothermal plume processes. Both V and Mo clearly associate with Mn cycling, whereas U may be associating with either Mn oxides and/or Fe oxyhydroxides. Rhenium is uncomplicated by adsorption to Mn oxides and/or Fe oxyhydroxides, and Re accumulation in sediments appears to be due solely to the extent of reducing conditions. Therefore, authigenic sediment Re enrichment appears to be the best indicator for intermediate reducing conditions, where oxygen penetrates less than ∼1 cm below the sediment-water interface, when coupled with negligible authigenic Mo enrichment.     

Distribution of Cs and Pu in the surface waters of the East Sea (Sea of Japan)

Surface and subsurface water samples for ¹³⁷Cs and ^239,240Pu analysis were collected in the East Sea (Sea of Japan) during August 1993. The ¹³⁷Cs levels of the surface waters are quite homogeneous in the East Sea (average = 3.1±0.2 mBq kg⁻¹). The ^239,240Pu levels vary from 6 to 10 μBq kg⁻¹ in the surface. ^239,240Pu to ¹³⁷Cs ratios in the surface water are within 0.002 to 0.003. The East Sea may be regarded as a part of the North Pacific Ocean in terms of ¹³⁷Cs dispersal in the surface, where the ¹³⁷Cs contents of the surface seawater seem to be controlled primarily by the atmospheric input. However, since our sampling was made just two months prior to the widely publicized Russian dumping incident on the 17th October 1993, our measurements may provide background data to assess the immediate impact of the Russian dumping on the levels of ¹³⁷Cs and ^239,240Pu in the East Sea.     

R/V Isabu-Based First Ultraclean Seawater Sampling for Ocean Trace Elements in Korea

Ocean Science Journal - Trace elements (Mn, Fe, Co, Ni, Cu, Zn, etc.) are essential micronutrients for marine organisms and are thus related to major issues in the ocean, such as climate change,...     

Investigating the Effects of Different LED Wavelengths on Aggregation and Swimming Behavior of Chub Mackerel (Scomber japonicus)

Ocean Science Journal - Efficient fish aggregation systems are essential for catching chub mackerel (Scomber japonicus), which is a major target of purse seine fisheries in South Korea. To aid the...     

Depositional environment in the southern Ulleung Basin, East Sea (Sea of Japan), during the last 48 000 years

The present study is based on the sedimentological data from a piston core KCES1 off the southern Ulleung Basin margin, the East Sea (Sea of Japan). The data include sediment color (L^*), X-ray radiographs, grain size distribution and AMS¹⁴C date. Four kinds of sediments (homogeneous, laminated, crudely laminated and hybrid sediments) are identified according to the characters of the sedimentary structures that were considered to reflect changes in bottom-water oxygenation. Alternations of dark laminated/crudely laminated sediments and light homogeneous sediments represent millennial-scale variations that are possibly associated with the high-resolution changes in the East Asian monsoon (EAM). The relative contributions of the East China Sea Coastal Water (ECSCW) and the Tsushima Warm Current (TWC) were likely the main reasons for the repetition of the anoxic and oxic depositional conditions in the East Sea since the last 48 ka BP. During the interstadial, the strengthen summer EAM was attributed to the expansion of the ECSCW because of more humid climate in central Asia, and then more strongly low-salinity, nutrient-enriched water was introduced into the East Sea. The ventilation of deep water was restricted and therefore the dark laminated layer deposited under the anoxic bottom water condition. During the lowest stand of sea level in the last glacial maximum (LGM), the isolated East Sea dominated by stratiˉed water masses and the euxinic depositional environment formed. The homogenous sediments have been predominating since 17.5 ka BP indicating that the TWC has intruded into the East Sea gradually with the stepwise rise of sea level and the bottom water oxygen level was high. During the late Younger Dryas (YD) period, the last dark laminated layer deposited because the ventilation of bottom water was restricted by stronger summer EAM. The TWC strengthened and the bottom water became oxic again from 10.5 ka BP.     

Statistical Moments of Active-Region Images During Solar Flares

We present new temporal-evolution diagnostics of solar flares. The high-order statistical moments (skewness and kurtosis) of the Hα images of active regions during solar flares were computed from their initial phases up to their maxima. The same method was used for quiet active regions for tests and comparison. We found that temporal profiles of the Hα statistical moments during flares roughly correspond to those observed in soft X-rays by the GOES satellite. Maxima of the cross-correlation coefficients between the skewness and the GOES X-rays were found to be 0.82?–?0.98, and the GOES X-rays are delayed 0?–?144 seconds against the skewness. We recognized that these moments are very sensitive to pre-flare activities. Therefore we used them to determine the flare starting-time and to study the pre-flare quasi-periodic processes. We determined the periods of these pre-flare processes in an interval of 20?–?400 seconds by using special convolution filters and Fourier analysis. We propose to use this method to analyze active regions during the very early phases of solar flares, and even in real time.     

Surface albedo from the geostationary Communication,Ocean and Meteorological Satellite (COMS)/Meteorological Imager (MI) observation system

The surface albedo is an essential climate variable that is considered in many applications used for predicting climate and understanding the mechanisms of climate change. In this study, surface albedo was estimated using a bidirectional reflectance distribution function model based on Communication, Ocean and Meteorological Satellite/Meteorological Imager data. Geostationary orbiting satellite data are suitable for a level 2 product like albedo, which requires a synthetic process to estimate. The authors modified established methods to consider the geometry of the solar-surface-sensor of COMS/MI. Of note, the viewing zenith angle term was removed from the kernel integration used for estimating spectral albedo. Finally, the spectral (narrow) albedo was converted into the broadband albedo with shortwave length (approximately 0.3–2.5 μm). This study determined conversion coefficients using only one spectral albedo of visible channel. The estimated albedo had a relatively high correlation with Satellite Pour l’Observation de la Terre/Vegetation and low unweighted error values specific for land types or times. The validation results show that estimated albedo has a root mean square error of 0.0134 at Jeju flux site that indicates accuracy similar to that of other satellite-based products.