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.     

Improved water quality in response to pollution control measures at Masan Bay, Korea

The total pollution load management system (TPLMS) was first applied in 2007 to the highly developed Masan Bay watershed, Korea. To evaluate the effect of TPLMS on water quality improvement, we analyzed the water qualities in rivers and bay during 2005-2010, targeting chemical oxygen demand (COD), suspended sediment (SS), total nitrogen (TN), and total phosphorus (TP) loads. Land-based pollutant loading all decreased during this period, with a significant reduction in COD and SS loads (p<0.01). The COD reduction in seawater, following the TPLMS implementation, was also significant (p<0.01). Time-lagged responses in COD and Chl-a supported an estimated seawater residence time of ~1 month. Land-based nutrient loads were also significantly reduced for TN (p<0.01) and TP (p<0.05), however, significant reductions were not observed in the bay, indicating potential alternative nutrient inputs from non-point sources into the bay system.     

Effects of an Urban Park and Residential Area on the Atmospheric CO2 Concentration and Flux in Seoul, Korea

The CO₂ concentrations and fluxes over an urban forest site (Namsan) and an urban residential region (Boramae) in Seoul, Korea, during the non-growing season (2–4 March 2011), the growing season (10–12 June 2011), and the late-growing season (22–24 September 2011) were analyzed. The CO₂ concentrations of two sites showed nearly the same diurnal variation, with a maximum value occurring during the night and a minimum value occurring during daytime, as well as the same seasonal variation, with a maximum value during the non-growing season (early spring) and a minimum value during the growing season (summer). The CO₂ flux over the urban forest did not show any typical diurnal variation during the non-growing season, but did show diurnal variation with a small positive value during the night and a large negative value during daytime in the growing and late-growing seasons due to photosynthesis in the urban forest. The CO₂ flux over the urban residential region showed a positive daily mean value for all periods, with large values during the non-growing season and small values during the growing season, and it also showed diurnal variation with two maxima at 0600–1000 LST and 1800–2400 LST, and two minima at 0300-0600 LST and 1100-1500 LST, and was strongly correlated with the use of liquefied natural gas for cooking and heating by surrounding houses.     

Tidal Influences on Biotic and Abiotic Factors in the Seomjin River Estuary and Gwangyang Bay,Korea

To assess changes in abiotic and biotic factors between flood and ebb tides, we investigated the seasonal phytoplankton dynamics and environmental conditions along a salinity gradient at 14 stations in the Seomjin River estuary (SRE), Korea, and conducted bioassays to investigate the effect of nutrient addition (+N, +P, and +NP) on phytoplankton growth. Saltwater intrusion upstream was greatly dependent on the amount of freshwater discharge resulting from seasonal rainfall. There was a strong negative correlation between salinity and the nitrate+nitrite concentration (p?<?0.001), and between salinity and the silicate concentration (p?<?0.001), but no clear correlation between salinity and the ammonium concentration, or salinity and the phosphate concentration (p?>?0.01). This indicates that the N and Si loading increased as a result of freshwater input. The algal bioassays showed that high phytoplankton growth rates were usually recorded in response to the +NP treatment, but in the saltwater zone, the phytoplankton community also responded rapidly to the +N treatment, and to the +P treatment in the freshwater zone. The range of nutrient limitation depended on freshwater discharge. The seasonal and horizontal distribution of phytoplankton communities changed along the salinity gradient. The significant differences in abiotic factors between flood and ebb tides play important roles in controlling the biotic factors, including the occurrence of aquatic organisms including microalgae.     

Biomarker responses in caged rockfish (Sebastes schlegeli) from Masan Bay and Haegeumgang, South Korea

The purpose of this study was to compare enzymatic biomarker activities in fish caged at two sites, Masan Bay (contaminated) and Haeguemgang (reference). In the present study, ethoxyresorufin O-deethylase (EROD), brain acetyl cholinesterase (bAChE), muscle acetyl cholinesterase (mAChE) and butyryl cholinesterase (mBChE) in caged rockfish (Sebastes schlegeli) were measured 0, 1, 3, 7, 14, 21 and 30 days after caging. The level of CYP1A mRNA and Protein expression was induced higher in Masan Bay at 1, 3, 7, 14 and 30 days after caging. EROD activity in the caged fish was significantly higher in Masan Bay than in Haeguemgang 3 and 7 days after caging, but not at 14 and 30 days after caging. bAChE activity was significantly inhibited at 7 and 14 days after caging in Masan Bay. However, mBChE activity was not significantly inhibited during the experiment. Taken together, the data suggest that the caged fish were exposed, at least transiently, to CYP1A inducers and ChE inhibitors, which is consistent with our previous observations.     

Boldness in a deep sea hermit crab to simulated tactile predator attacks is unaffected by ocean acidification

Despite rapidly growing interest in the effects of ocean acidification on marine animals, the ability of deep-sea animals to acclimate or adapt to reduced pH conditions has received little attention. Deep-sea species are generally thought to be less tolerant of environmental variation than shallow-living species because they inhabit relatively stable conditions for nearly all environmental parameters. To explore whether deep-sea hermit crabs (Pagurus tanneri) can acclimate to ocean acidification over several weeks, we compared behavioral “boldness,” measured as time taken to re-emerge from shells after a simulated predatory attack by a toy octopus, under ambient (pH ～7.6) and expected future (pH ～7.1) conditions. The boldness measure for crab behavioral responses did not differ between different pH treatments, suggesting that future deep-sea acidification would not influence anti-predatory behavior. However, we did not examine the effects of olfactory cues released by predators that may affect hermit crab behavior and could be influenced by changes in the ocean carbonate system driven by increasing CO₂ levels.     

Hydrological modelling uncertainty analysis for different flow quantiles: a case study in two hydro-geographically different watersheds

This study focuses on analysis of hydrological model parameter uncertainty at varying sub-basin spatial scales. It was found that the variation in sub-basin spatial scale had little influence on the entire flow simulations. However, the different sub-basin spatial scales had a significant impact on the reproduction of the flow quantiles. The coarser sub-basin spatial scale provided a better coverage of most prediction uncertainty in observations. However, the finer sub-basin spatial scale produced the best single simulation output closer to the observations. In general, the optimal sub-basin spatial scales (ratio to the entire watershed size) in the two test watersheds were found to be in the ranges 14–19% and 2–4% for good simulation of high and low flows, respectively. It is therefore worthwhile to put more effort into reproducing different flow quantiles by investigating an appropriate sub-basin spatial scale.     

Petrology of an intrusion-related high-grade migmatite: implications for partial melting of metasedimentary rocks and leucosome-forming processes

Intrusion-related migmatites comprise a substantial part of the high-grade part of the southern Damara orogen, Namibia which is dominated by Al-rich metasedimentary rocks and various granites. Migmatites consist of melanosomes with biotite+sillimanite+garnet+cordierite+hercynite and leucosomes are garnet- and cordierite-bearing. Metamorphic grade throughout the area is in the upper amphibolite to lower granulite facies (5–6 kbar at 730–750 °C). Field evidence, petrographic observations, chemical data and mass balance calculations suggest that intrusion of granitic magmas and concomitant partial melting of metasedimentary units were the main processes for the generation of the migmatites. The intruding melts were significantly modified by magma mixing with in situ partial melts, accumulation of mainly feldspar and contamination with garnet from the wall rocks. However, it is suggested that these melts originally represented disequilibrium melts from a metasedimentary protolith. The occurrence of LILE-, HFSE- and LREE-enriched and -depleted residues within the leucosomes implies that both quartzo-feldspathic and pelitic rocks were subjected to partial melting. Isotope ratios of the leucosomes are rather constant (¹⁴³Nd/¹⁴⁴Nd (500 Ma): 0.511718–0.511754, ε Nd (500 Ma): ?3.54 to ?5.11) and Sr (⁸⁷Sr/⁸⁶Sr (500 Ma): 0.714119–0.714686), the metasedimentary units have rather constant Nd isotope ratios (¹⁴³Nd/¹⁴⁴Nd (500 Ma): 0.511622–0.511789, ε Nd (500 Ma): ?3.70 to ?6.93) but variable Sr isotope ratios Sr (⁸⁷Sr/⁸⁶Sr (500 Ma): 0.713527–0.722268). The most restitic melanosome MEL 4 has a Sr isotopic composition of ⁸⁷Sr/⁸⁶Sr (500 Ma): 0.729380. Oxygen isotopes do not mirror the proposed contamination process, due to the equally high δ¹⁸O contents of metasediments and crustal melts. However, the most LILE-depleted residue MEL 4 shows the lowest δ¹⁸O value (<10). Mass balance calculations suggest high degrees of partial melting (20–40%). It is concluded that partial melting was promoted by heat transfer and release of a fluid phase from the intruding granites. High degrees of partial melting can be reached as long as the available H₂O, derived from the crystallization of the intruding granites, is efficiently recycled within the rock volume. Due to the limited amounts of in situ melting, it seems likely that such regional migmatite terranes are not the sources for large intrusive granite bodies. The high geothermal gradient inferred from the metamorphic conditions was probably caused by exhumation of deep crustal rocks and contemporaneous intrusion of huge masses of granitoid magmas. The Davetsaub area represents an example of migmatites formed at moderate pressures and high temperatures, and illustrates some of the reactions that may modify leucosome compositions. The area provides constraints on melting processes operating in high-grade metasedimentary rocks.     

Multi‐scale system reliability analysis of lifeline networks under earthquake hazards

Recent earthquake events evidenced that damage of structural components in a lifeline network may cause prolonged disruption of lifeline services, which eventually results in significant socio‐economic losses in the affected area. Despite recent advances in network reliability analysis, the complexity of the problem and various uncertainties still make it a challenging task to evaluate the post‐hazard performance and connectivity of lifeline networks efficiently and accurately. In order to overcome such challenges and take advantage of merits of multi‐scale analysis, this paper develops a multi‐scale system reliability analysis method by integrating a network decomposition approach with the matrix‐based system reliability (MSR) method. In addition to facilitating system reliability analysis of large‐size networks, the multi‐scale approach enables optimizing the level of computational effort on subsystems; identifying the relative importance of components and subsystems at multiple scales; and providing a collaborative risk management framework. The MSR method is uniformly applied for system reliability analyses at both the lower‐scale (for link failure) and the higher‐scale (for system connectivity) to obtain the probability of general system events, various conditional probabilities, component importance measures, statistical correlation between subsystem failures and parameter sensitivities. The proposed multi‐scale analysis method is demonstrated by its application to a gas distribution network in Shelby County of Tennessee. A parametric study is performed to determine the number of segments during the lower‐scale MSR analysis of each pipeline based on the strength of the spatial correlation of seismic intensity. It is shown that the spatial correlation should be considered at both scales for accurate reliability evaluation. The proposed multi‐scale analysis approach provides an effective framework of risk assessment and decision support for lifeline networks under earthquake hazards. Copyright © 2009 John Wiley & Sons, Ltd.     

Permo-Triassic high-pressure metamorphism in the central western Korean Peninsula,and its link to Paleo-Tethyan Ocean closure: Key issues revisited

Permo-Triassic high-pressure(HP) mafic granulites, together with the Bibong retrogressed eclogite,preserved along the central western Korean Peninsula provide important insights into the Late Permian to Triassic collisional orogeny in northeast Asia. The metamorphic pressureetemperatureetime(P-T-t)paths of these rocks, however, remain poorly constrained and even overestimated, owing to outdated geothermobarometers and inaccurate isopleth techniques. Here we evaluate the metamorphic Pe T conditions of Triassic HP mafic granulites including those in Baekdong, Sinri and Daepan and the Bibong Triassic retrogressed eclogite in the Hongseong area, and the Permo-Triassic Samgot mafic granulite in the Imjingang Belt of the central western Korean Peninsula through the application of modern phase equilibria techniques. The Baekdong and Samgot mafic granulites and the Bibong retrogressed eclogite yield a range of 12.0 -16.0 kbar and 800 -900℃, representing HP granulite facies conditions. The Sinri and Daepan granulites from the Hongseong area show relatively lower grade metamorphic conditions between HP granulite and normal granulite facies, and are characterized by sub-isothermal decompression during exhumation. The similarities in the metamorphic ages and the post-collisional igneous activity from the central western Korean Peninsula indicate that the Triassic ages represent the retrograde stage of the metamorphic Pe T paths. In contrast, the Late Permian metamorphic ages, which are older than protolith ages of the post-collisional igneous rocks, correspond to the possible prograde stage of metamorphism. The P-T-t paths presented in this paper, together with the metamorphic ages and post-orogenic igneous events reported from these areas suggest trace of the subduction, accretion and exhumation history, and indicate a tectonic linkage among the northeast Asian continents during the Paleo-Tethyan Ocean closure.