Optimal conditions for three brood chronic toxicity test method using a freshwater macroinvertebrate <Emphasis Type="Italic">Moina macrocopa</Emphasis>

Freshwater cladocera such as Daphnia magna and Ceriodaphnia dubia have been used extensively for freshwater toxicity test worldwide. However, these species may not be indigenous in certain geographical regions, which restrict the utility of these organisms as test species. In the present study, we investigated optimal culture and test conditions for an indigenous freshwater macroinvertebrate of Korea, Moina macrocopa. The culture conditions that were evaluated included water temperature (20°C and 25°C), rearing media (moderately hard water or MHW, with or without selenium supplementation, or Elendt M4), and food density (2.5 × 10⁷ and 5 × 10⁷ cells/mL of Selenastrum capricornutum), and their effects on the life history characteristics of M. macrocopa were determined. Population growth rate of M. macrocopa was maximized at 25°C with 5 × 10⁷ cells/mL of algal food density in MHW. A series of chronic three brood reference toxicant tests were conducted under the ideal culture conditions that were identified here, and the results of the tests indicated reliable reproducibility of the test protocol. Optimal culture and test conditions that were identified for M. macrocopa in the present study are suggested for evaluation of chronic toxicity of chemicals and industrial or municipal discharge.     

Monitoring of heavy metal contaminants using feathers of shorebirds, Korea

This study presents concentrations of iron, zinc, copper, lead and cadmium in the feathers of 3 shorebird species (n = 29) from Okgu Mudflat, Korea in the East Asian-Australian Migration Flyways. Lead concentrations (ANOVA, p < 0.001) in Red-necked Stints (geomean = 9.61 μg g(-1) dry weight) were higher than in Terek Sandpipers (geomean = 5.56 μg g(-1) dry weight) which in turn were higher than in Great Knots (geomean = 2.78 μg g(-1) wet weight). Cadmium concentrations (ANOVA, p < 0.001) were higher in Great Knots (geomean = 2.97 μg g(-1) wet weight) and in Red-necked Stints (geomean = 2.70 μg g(-1) dry weight) than in Terek Sandpipers (geomean = 0.33 μg g(-1) dry weight). Lead (r = 0.574, p < 0.01) and cadmium (r = 0.380, p < 0.05) concentrations between feathers and livers of shorebirds were significantly correlated. Lead concentrations in 65.5% (19 individuals) of shorebirds exceeded a toxicity threshold for feathers (4 μg g(-1) dry weight). Iron, zinc, copper, lead and cadmium concentrations in feathers were within the range of earlier studies for wild birds, but lead concentrations in Red-necked Stints were higher than those reported in other studies. Because lead concentrations in feathers and livers of Red-necked Stints were markedly higher than in other shorebirds, we suggest that Red-necked Stints were exposed to higher lead concentrations than the other shorebirds on their breeding or wintering grounds.     

Hydroxyl radical generation and oxidative stress in Carassius auratus liver as affected by 2,4,6-trichlorophenol

With Carassius auratus, one of the main economic fish species in Eastern China as test material, this paper studied the hydroxyl radical generation and oxidative stress in its liver under the effect of 2,4,6-trichlorophenol (2,4,6-TCP). Different doses of 2,4,6-TCP were injected intraperitoneally into the fishes, and the Electron paramagnetic resonance (EPR) spectra of hepatic free radicals, activities of superoxide dismutase (SOD), catalase (CAT) and glutathione-s-transferase (GST), levels of reduced glutathione (GSH) and oxidized glutathione (GSSG), and malondialdehyde (MDA) contents were determined 24h after injection. The results showed that under the effects of 2,4,6-TCP, the generation of free radical that was considered to be hydroxyl radical increased significantly, the activities of antioxidant enzymes decreased, with CAT most strongly affected and followed by SOD and GST, the GSH level decreased significantly while GSSG level had little difference, resulting in a decreased GSH/GSSG ratio, and the MDA content increased significantly. All the test parameters showed that C. auratus was subjected to oxidative stress and damage when exposed to 2,4,6-TCP.     

Comparison of different disinfection processes in the effective removal of antibiotic-resistant bacteria and genes

This study compared three different disinfection processes(chlorination, E-beam, and ozone) and the efficacy of three oxidants(H2O2, S2O-8, and peroxymonosulfate(MPS)) in removing antibiotic resistant bacteria(ARB) and antibiotic resistance genes(ARGs) in a synthetic wastewater. More than30 mg/L of chlorine was needed to remove over 90% of ARB and ARG. For the E-beam method, only1 dose(kGy) was needed to remove ARB and ARG, and ozone could reduce ARB and ARG by more than 90% even at 3 mg/L ozone concentration. In the ozone process, CT values(concentration × time)were compared for ozone alone and combined with different catalysts based on the 2-log removal of ARB and ARG. Ozone treatment yielded a value of 31 and 33(mg·min)/L for ARB and ARGs respectively. On the other hand, ozone with persulfate yielded 15.9 and 18.5(mg·min)/L while ozone with monopersulfate yielded a value of 12 and 14.5(mg·min)/L. This implies that the addition of these catalysts significantly reduces the contact time to achieve a 2-log removal, thus enhancing the process in terms of its kinetics.     

The status of flood wastes treatment and future tasks in South Korea

Natural disasters such as typhoon, flood, and heavy rainfall cause damage in South Korea every year during the summer season. After each rainy season, South Korea suffers not only from flood wastes but also from debris that pile up at dams and stagnate at the estuary of the river. Thus, it is very important to handle these types of wastes as quickly as possible to recover from flood damages and to prevent environmental contamination such as offensive odor and water contamination by the leachate from flood wastes. Other countries such as Japan or USA have established and implemented regulations and guidelines for flood waste. Note, however, that South Korea did not establish practical guidelines; hence, the urgency of establishing practical measures for flood waste. In this study, we suggested various ways of making environmentally sound guidelines including the method of reducing the amount of flood waste by environmentally sound treatment process for flood waste, and the method of setting up and operating the temporary storage site for purposes of efficient separation and treatment of flood waste.     

Vaporization reduction characteristics of aqueous ammonia solutions by the addition of ethylene glycol, glycerol and glycine to the CO2 absorption process

Aqueous ammonia (NH₃) solution can be used as an alternative absorption for the control of CO₂ emitted from flue gases due to its high absorption capacity, fast absorption rate and low corrosion problem. The emission of CO₂ from iron and steel plants requires much attention, as they are higher than those emitted from power plants at a single point source. In the present work, low concentration ammonia liquor, 9 wt.%, was used with various additives to obtain the kinetic properties using the blast furnace gas model. Although a solution with a high ammonia concentration enables high CO₂ absorption efficiency, ammonium ions are lost as ammonia vapor, resulting in reduced CO₂ absorption due to the lower concentration of the ammonia absorbent. To decrease the vaporization of ammonia, ethylene glycol, glycerol and glycine, which contain more than one hydroxyl radical, were chosen. The experiments were conducted at 313 K similar to the CO₂ absorption conditions for the blast furnace gas model.     

Analysis and evaluation of chlorinated persistent organic compounds and PAHs in sludge in Korea

The concentrations of 12 POPs listed in the Stockholm convention, chlorophenols (CPs) and PAHs were investigated in sludge samples from wastewater and sewage treatment plants (WWTPs and STPs). The concentrations of PCDD/Fs in the wastewater sludge ranged from 0.189 to 1092 ng-TEQkg(-1) dry wt., and most of the sludge samples had levels below the EU guideline for the land application of PCDD/Fs (<100 ng-TEQkg(-1) dry wt.) except one sample. Co-PCB congeners were analyzed from four WWTPs, with total concentrations ranging from 0.265 to 26.6 ng-TEQkg(-1) dry wt., which were similar to the results obtained from previous studies. The levels of PCDD/Fs and Co-PCBs varied according to the main source of the influent to each WWTP and the paper industry was the main source of these compounds in the sludge due to the chlorine bleaching process. In case of OCPs, HCB and p,p'-DDE were detected at relatively high levels in the sludge samples compared to other target compounds, ranging from 1.30 to 21.5 microg kg(-1) dry wt. and 0.758 to 14.8 microg kg(-1) dry wt., respectively. Different OCP distribution patterns were observed according to sludge types, with HCB and DDTs being dominant in the sludge from WWTPs and STPs, respectively. The total levels of PAHs and CPs ranged from 1.24 to 44.9 mg kg(-1) dry wt. and 0.340 to 3.85 mg kg(-1) dry wt., respectively. The PAHs and CPs were also shown to have various distribution patterns, possibly due to the different wastewater sources to the WWTPs.     

Characteristics of Asian dust transport based on synoptic meteorological analysis over Korea

Classification of synoptic patterns and their correlation with dust events over East Asia were performed by means of cluster analysis. The average linkage and K-means clustering techniques were used to identify two major weather types during Asian dust events (ADEs; total 26 ADEs with 47 dusty days) of six spring seasons from 1996 to 2001. The first weather type mainly influenced neighboring Asian countries and frequently occurred with ADEs (approximately 23% of ADE cases). It mostly occurred under a surface high (low)-pressure system over the west (east) of the Korean peninsula coupled with an upper-level trough and cutoff low passage over the center of the Korean peninsula. It showed strong advection in the middle/ upper troposphere with both a high aerosol index and enhanced coarse particulate matter (PM) loading over Korea. In contrast, the second weather type was mostly associated with long distance or continental-scale transport and occurred less frequently with ADEs (approximately 15%). It appeared with an upper-level trough and a cutoff low vertically connected with a surface low system that was formed by a strong cyclonic vortex over the north of the Korean peninsula. There were weak advection, low aerosol index, and low coarse PM concentration over the Korean peninsula during the second weather type. In addition, it was found to be mostly associated with the trans-Pacific transport of Asian dust to the western coast of North America.     

Feasibility of phosphate fertilizer to immobilize cadmium in a field

To reduce effectively cadmium (Cd) phytoextractability by phosphate fertilizer in Cd contaminated soil, fused and superphosphate (FSP) was applied at the rate of 0, 33.5 (recommendation level), 167.5, and 335 kg P ha⁻¹ for radish (Raphanus sativa L.). Unlike from what we expected, soil Cd extractability and Cd concentration in radish increased with increasing FSP application in the field. To determine the effect of FSP on Cd immobilization, FSP was mixed with the selected soil at the rate of 0, 200, 400, 800, and 1600 mg P kg⁻¹ and then incubated for 8 weeks. As observed in the field study, NH₄OAc extractable Cd concentration increased slightly with FSP addition up to 400 mg P kg⁻¹ and thereafter dramatically decreased upon increasing its application rate. Soil pH and negative charge were decreased at low level of FSP application up to 400 mg P kg⁻¹, but thereafter continually increased with increasing application level. This could be indirect evidence that net soil negative charge was increased by the specific adsorption of phosphate at the high rate of FSP application over 400 mg P kg⁻¹. The labile Cd fraction (water soluble and exchangeable + acidic fraction) increased with increasing FSP application by 400 mg P kg⁻¹ and thereafter gradually decreased with corresponding increase in unlabile fraction (oxidizable and residual fraction). Based on these results, FSP might be applied with a very high rate over 800 mg P kg⁻¹ to decrease Cd extractability in the selected field. However, this level is equivalent to 1440 kg P ha⁻¹, which is about 43 times higher than the recommendation levels for radish production and resulted in a significant increase in water soluble P concentration creating a new environmental problem. Therefore, the feasibility of FSP to reduce Cd extractability in the field is very low.     

Observations of aerosol-bound ionic compositions at Cheju Island,Korea

To investigate the regional cycle of aerosols and their ionic constituents, three field intensive campaigns were conducted during fall and winter of 1997 and spring of 1998. The concentrations of most ionic species were found to decrease significantly across fall, winter, and spring such that the sum for all cation (and anion) species of each season is computed as: 193 > 96 > 73.7 nequiv m(-3) (and 240 > 104 > 51.5 nequiv m(-3)). To examine the fundamental characteristics of aerosol compositions in the study area, we conducted correlation analysis in various manners. The results indicated that the concentrations of major ionic species were strongly affected by some meteorological parameters including wind speed. It was also seen that relative strengths of correlations between important parameters (e.g., between wind speed and most of major inorganic species) maintain close relationships with the factors associated with the air mass origin. In addition, the results of factor analysis indicated the existence of at least three major sources in the study area which include: sea-salt aerosol, secondary aerosol, and organic aerosol component. The springtime occurrence of unexpectedly low concentrations of most ionic constituents is found to sensitively reflect the influence of the inflow of southeasterly winds that prevailed during spring, while it is not common for that season of the year. Because most of those changes are closely tied with the variabilities in the regional circulation patterns for each measurement period, assessment of the ionic composition in concert with the temporal variations of meteorological conditions provided valuable insights into the source signals of different air masses that passed by the study area.