The effect of operational parameters on the photocatalytic degradation of pesticide

The photocatalytic degradation of Cartap Hydrochloride, a synthetic pesticide. has been investigated over coated TiO2 photocatalysts irradiated with a ultraviolet (UV) light. The effect of operational parameters, i.e., Cartap Hydrochloride concentration, reaction time, light intensity and additive on the degradation rate of aqueous solution of Cartap Hydrochloride has been examined. Results show that the employment of efficient photocatalysts and the selection of optimal operational parameters may lead to degradation of Cartap Hydrochloride solutions.     

Full-scale experience for nitrogen removal from piggery waste.

The nitrogen-removal performances of three full-scale piggery wastewater treatment plants, with different organic and nitrogen loads, at the capacity ranges of 95 to 130 m3/d, were compared in this study. Plants 1 and 2 can be characterized as the modification of anoxic-aerobic operating systems, while an anaerobic and anoxic-aerobic system was used in plant 3. The influent piggery wastewater concentration for plant 1 was relatively lower, but with higher organic and nitrogen loads, resulting in higher chemical oxygen demand (COD) and ammonium-nitrogen in effluent. Plant 2 was operated with strong piggery wastewater, resulting in a higher operating temperature. The high temperature could inhibit the nitrifying activity in plant 2. Although plant 3 was operated with a higher influent total COD-to-total Kjeldahl nitrogen ratio (TCOD:TKN), an additional external carbon source was required to polish the final effluent to remove nitrogen. Influent COD in plant 3 was used in the anaerobic-anoxic reactor for both methane (CH4) production and denitrification. Based on various mass balances, including caloric, COD, and alkalinity, the key elements for the successful nitrogen removal from the piggery waste were reactor temperature (less than 35degrees C), influent TCOD:TKN (greater than 6), and alkalinity-to-TKN ratio (greater than 3).     

Daily intakes of naturally occurring radioisotopes in typical Korean foods

The concentrations of naturally occurring radioisotopes ((232)Th, (228)Th, (230)Th, (228)Ra, (226)Ra, and (40)K) in typical Korean foods were evaluated. The daily intakes of these radioisotopes were calculated by comparing concentrations in typical Korean foods and the daily consumption rates of these foods. Daily intakes were as follows: (232)Th, 0.00-0.23; (228)Th, 0.00-2.04; (230)Th, 0.00-0.26; (228)Ra, 0.02-2.73; (226)Ra, 0.01-4.37 mBq/day; and (40)K, 0.01-5.71 Bq/day. The total daily intake of the naturally occurring radioisotopes measured in this study from food was 39.46 Bq/day. The total annual internal dose resulting from ingestion of radioisotopes in food was 109.83 muSv/y, and the radioisotope with the highest daily intake was (40)K. These values were same level compiled in other countries.     

Organic micro-pollutant removal in liquid-phase using carbonized silk cotton hull

Phenolic compounds constitute one of the major pollutants in the modern world. Although many physical and chemical treatment technologies for their removal exist, most of them are economically not feasible. The present study was aimed at using silk cotton hull, a potent agricultural waste as an adsobent for removal of 2,4-dichlorophenol (2,4-DCP), which was used as a model phenolic compound. The process parameters were investigated and optimized conditions were determined. The equilibrium time was found to ...     

Transfer of 137Cs to rice plants from various paddy soils contaminated under flooded conditions at different growth stages

Soil blocks from 18 paddy fields around three Korean nuclear power plant sites were put into lysimeters. Greenhouse experiments were carried out to investigate the (137)Cs transfer from these paddy soils to rice plants for its deposition at different growth stages. A solution of (137)Cs was applied to the flooded lysimeters at 2-3 different stages. The applied (137)Cs was mixed with the topsoil only at the pre-transplanting application. The transfer was quantified with a transfer factor based on the unit-area deposition (TF(a), m(2)kg(-1)-dry). The TF(a) in the pre-transplanting application showed a remarkable variation with the soils. However, the differences in the mean values among the study sites were not statistically significant. The straw TF(a) was 2-3 times higher than the corresponding seed value. The early-tillering stage and booting stage applications resulted in a higher transfer than the pre-transplanting application by factors of, on an average, 2 and 16 for the straws, and 3 and 25 for the hulled seeds, respectively. The (137)Cs transfer was found to correlate negatively with the soil pH and positively with the organic matter content. Based on the present results, the representative (137)Cs TF(a) values for the rice are proposed for use in the whole of Korea for the deposition at three different growth stages.     

Field depuration and biotransformation of paralytic shellfish toxins in scallop<Emphasis Type="Italic"> Chlamys nobilis</Emphasis> and green-lipped mussel<Emphasis Type="Italic"> Perna viridis</Emphasis>

Under laboratory conditions, the scallop Chlamys nobilis and the mussel Perna viridis were exposed to N-sulfocarbamoyl toxins (C2 toxin), a paralytic shellfish toxin (PST), by feeding a local toxic strain of the dinoflagellate Alexandrium tamarense (ATDP) that produced C2 toxin exclusively. The bivalves were subsequently depurated in the field, and their depuration kinetics, biotransformation and toxin distribution were quantified. Depuration was characterized by a rapid loss within the first day, followed by a secondary slower loss of toxins. In the fast depuration phase, scallops detoxified PSTs more quickly than the mussels (depuration rate constants for scallops and mussels were 1.16 day^–1 and 0.87 day^–1, respectively). In contrast, the mussels detoxified PSTs more quickly than the scallops in the slow depuration phase, and the calculated depuration rate constants (mean+SE) from day 2 to day 13 were 0.063+0.009 day^–1 and 0.040+0.019 day^–1 for mussels and scallops, respectively. The differences in the appearances of gonyautoxins, GTX2 and GTX3, and their decarbamoyl derivatives, dcGTX2, dcGTX3 and GTX5, which are all derivatives of C2 toxin, indicated active and species-specific biotransformation of the algal toxins in the two bivalves. In both species of bivalves, the non-viscera tissue contained fewer toxins and lower concentrations than the viscera-containing tissue compartment. In scallops, very little toxin was distributed in the adductor muscle. In mussels, most of the PSTs were found in the digestive gland with significant transport of toxins into the digestive gland from other tissues during the course of depuration. The toxin profiles of scallops and mussels differed from each other and from that of the toxic algae fed. A significant fraction of GTX5 was detected in the mussels but not in the scallops. Our study demonstrates a species specificity in the depuration kinetics, biotransformation and tissue distribution of PSTs among different bivalves.Communicated by T. Ikeda, Hakodate     

Distribution and structure of heterotrophic protist communities in the northeast equatorial Pacific Ocean

The distribution and structure of heterotrophic protist communities and size-fractionated chlorophyll a were studied during the Korea Deep Ocean Study 98 (KODOS 98) research expedition (July 1998) in the northeast equatorial Pacific Ocean (5–11°N). Areas of convergence and divergence formed at the boundaries of the South Equatorial Current (SEC), North Equatorial Current (NEC), and North Equatorial Counter Current (NECC) during the expedition. Water column physicochemical characteristics significantly influenced the size structure of heterotrophic protist communities. Intense vertical mixing and high nutrient and chlorophyll a concentrations characterized SEC and NECC areas, which were affected by converging and diverging water masses, respectively. Nanophytoplankton dominated in SEC and NECC areas; both areas also had relatively high heterotrophic protist biomasses (average 743 µg C m^–2). NEC areas were characterized by a stratified vertical structure, low nutrient and chlorophyll a concentrations, and picophytoplankton dominance. The heterotrophic protist biomass in NEC areas averaged 414 µg C m^–2; nanoprotists (<20 µm) dominated the community. The nanoprotist biomass comprised 49–54% of the total heterotrophic protist biomass in SEC/NECC areas and 67–72% in NEC areas. The biomass of heterotrophic protists was higher in SEC/NECC areas than in NEC areas, but the relative importance of nanoprotists was greater in NEC areas than in SEC/NECC areas. Heterotrophic dinoflagellates were dominant components of the <20 µm and >20 µm size classes in both water columns. The biomass of heterotrophic protists significantly correlated with the net-, nano-, and picophytoplankton biomass in SEC/NECC areas and with the nano- and picophytoplankton biomass in NEC areas. Heterotrophic protists and phytoplankton also showed strong positive correlation in the study area. The size structure of the phytoplankton biomass coincided with that of heterotrophic protists; the heterotrophic protist biomass positively correlated with the protists prey source. These relationships suggest that the community structure of heterotrophic protists and the microbial food web depended on size classes within the phytoplankton biomass. Microzooplankton grazing and phytoplankton growth rates were higher in SEC/NECC areas than in NEC areas. In contrast, the potential primary production grazed by microzooplankton was relatively high in NEC areas (127.3%) compared with SEC/NECC areas (94.6%). Our results indicate that the relative importance and size structure of heterotrophic protists might vary according to two distinct water column structures.Communicated by T. Ikeda, Hakodate     

A study of polychlorinated dibenzo-p-dioxins and dibenzofurans in the atmosphere of Hong Kong

A total of 27 ambient air samples of were collected from six locations in Hong kong during the period of January-August, 2000 and analysed for polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs). In all sampling locations, higher concentrations of PCDDs/PCDFs, ranging from 0.03 to 0.43 pg I-TEQ/m3 were measured in winter months (January and March) than in the summer months (July and August) of concentrations at 0.018-0.025 pg I-TEQ/m3. These concentrations are similar to annual ranges reported earlier for two Hong Kong urban sites and other urban cities in Asia. Europe, and the United States. Despite significant seasonal variations in ambient air concentrations of PCDD/Fs (expressed in I-TEQ) were observed, the congener profiles of all the samples in this study period were similar, with OCDD, 1,2,3,4,6,7,8-HpCDD, OCDF and 1,2,3,4,6,7,8-HpCDF being the predominant species. However, the homologue profiles for the samples collected at the six locations of this study were found to display significantly different spatial and seasonal trends.     

Control of bacterial growth in water using synthesized inorganic disinfectant

Chlorine is a popular method for controlling bacterial growth in cooling towers. However, there are several drawbacks such as the difficulties in maintaining the disinfection efficacy particularly at high temperature and pH. In order to overcome these difficulties, an inorganic disinfectant based on silver and copper, which is called EEKO-BALL (commercial name), was recently developed. EEKO-BALL is made from specific ceramics and coating materials. This study was performed to evaluate the efficacy of EEKO-BALL and compare it with that of silver (Ag+) and copper (Cu2+) ions. In addition, a field study was undertaken to investigate the control of bacterial growth in several cooling tower systems. The results showed that the contact time required for inactivating 99% of E. coli was 15 min in the EEKO-BALL stock solution at 25 degrees C, pH 7.3, with 0.05 mgl(-1) Ag and 0.05 mgl(-1) Cu. EEKO-BALL was approximately four times more effective than silver and copper ions in inactivating E. coli at 25 degrees C, pH 7.3. The control of bacterial growth in the cooling towers was found to be effective, lasting more than two months after a one-time installation of the EEKO-BALL. Overall, this study suggests that EEKO-BALL can effectively work as an inorganic disinfectant for bacterial growth control.     

Persistent organochlorine residues in northern fur seal from the Pacific coast of Japan since 1971

The present study was conducted to determine the residue levels of persistent organochlorines such as PCB homologues, DDT and its metabolites, and HCH isomers in the ventral blubber of female northern fur seal (Callorhinus ursinus) collected off Sanriku, the Pacific coast of northern Japan, since 1971. Among the organochlorines examined, the concentrations of PCBs and DDTs were found to be high in all samples. The residue levels of these two contaminants showed a drastic reduction following maturity and then a slight increase after the retirement from pregnancy/menopause. Temporal variation of PCB and DDT residues showed maximum levels around 1976 and then decreased, whereas HCH residue levels revealed a very slow declining pattern. Considering the concentrations and compositions of the residues, the northern fur seal is likely to be exposed to organochlorine contamination deriving from global terms. In this context, continuous contamination has been foreseen with regard to PCB and HCH residues. The pattern of organochlorine residues indicated that the northern fur seal has higher metabolic capacity than Dall's porpoise, while it is comparable to those of larga seal and Steller sea lion.