• 대한임상독성학회지
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• 제3권1호
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• pp.11-16
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• 2005

Chemical mixtures of components, each of which are present at less than guidance concentrations, may be hazardous due to additivity, interactions, or both. Toxicological interactions may increase the health hazard above what would be expected from an assessment of each component singly, or all components additively. So chemical mixture are a particular issue in public health. There are several approach to assess whether there are additivity or interaction in assessing toxicological effects, such as, components-based approach, physiologically-based pharmacokinetic /pharmacodynamic(PBPK/PD) models, hazard index method, and weight-of evidence method. If we consider interaction or additivity effects in assessing the health effects of chemcial mixtures, we can get more accurate information about toxicological effects and dose-response relationship in chemical mixtures.

• 한국물환경학회지
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• 제23권5호
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• pp.723-730
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• 2007

This study was conducted to develop a combined method for remediating a Chlorinated Aliphatic Hydrocarbons (CAHs) mixtures-contaminated aquifer. The process is consist of two processes. A chemical process (1st) using natural zinc ores for reducing higher concentrations of CAH mixtures to the level at which biological process is feasible; and A biological process (2nd) using aerobic cometabolism for treating lower concentration of CAH mixtures (less than 1 mg/L). Natural zinc ore showed relatively high transformation capacity, average dehalogenation percentage, and the best economic efficiency in previously our study. To evaluate the feasibility of the process, we operated two columns in series (that is, chemical and biological columns). In the first column filled with natural zinc ore and sand, CAH mixtures were effectively transformed with more than 95% efficiency, the efficiency depends on the Empty Bed Contact Time (EBCT) and the mass of zinc ore packed. Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD) analysis were performed to make sure whether natural zinc ore played an key role in the dechlorination of the CAH mixtures. The characteristics of zinc metal surface changed after exposure to CAHs due to oxidation of $Zn^0$ to $Zn^{2+}$. In the biological column injecting propane, DO and effluent of the chemical column, only 1,1,1-TCA was cometabolically transformed. Consequently, the combined process would be effective to remediate an aquifer contaminated with high concentrations of CAH mixtures.

• 한국환경농학회지
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• 제29권2호
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• pp.93-101
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• 2010

갈탄과 아미노산액 혼합처리가 벼, 배추 및 고추의 지상부와 지하부 생육 및 수량에 미치는 영향을 조사한 후 생육증진효과를 검토하여 친환경농산물 생산용자재로의 활용가능성을 구명하고, 갈탄과 아미노산액에 화학비료를 감량하여 혼합처리하여도 작물재배 가능성이 있는지를 검토하며, 갈탄과 아미노산액 혼합처리 전후의 토양에 미치는 화학적 특성을 조사하여 토양개량제로써의 활용가능성을 구명하고자 하였다. 그 결과, 갈탄과 아미노산액 혼합처리한 구의 벼 생육은 화학비료 표준시비량 단용구보다 양호하였으며, 특히 갈탄과 아미노산액 150 kg/ha 처리구와 갈탄과 아미노산액 150 kg/ha 에 화학비료 표준시비량의 혼합처리구에서 다른 처리구보다 전반적으로 양호한 것으로 나타났다. 배추와 고추의 생육은 갈탄과 아미노산액 600 kg/ha 처리구와 갈탄과 아미노산액 600 kg/ha에 화학비료 표준시비량의 혼합처리구에서 다른 처리구보다 전반적으로 양호한 것으로 나타났다. 벼와 배추의 수량은 갈탄과 아미노산액 150kg/ha 처리구와 갈탄과 아미노산액 150 kg/ha 에 화학비료 표준시비량의 혼합처리구에서 양호하였고, 고추의 경우 갈탄과 아미노산액 600 kg/ha 처리구와 갈탄과 아미노산액 600 kg/ha에 화학비료 표준시비량의 혼합처리구에서 양호하였다. 논과 밭토양에 갈탄과 아미노산액과 화학비료감량 혼합처리구의 유기물함량은 전반적으로 높았고, EC는 낮았다. pH와 유효인산의 경우 밭토양에서는 약간 높아지는 경향이었고, 논토양에서는 큰 변화가 없었다. 논과 밭토양에 갈탄과 아미노산액과 화학비료감량처리시 토양의 부분적인 화학적 특성, 특히 유기물함량을 높일 수 있었다. 그러나 이와 같은 결과들이 연용처리하여 재배하였을 경우에도 유사한 결과를 초래할지에 대한 연구는 추후 면밀히 검토되어져야 할 것으로 판단된다.

• Korean Membrane Journal
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• 제6권1호
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• pp.55-60
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• 2004

In recent years, an increasing interest in membrane technology has been observed in chemical and environmental industry. Membrane technology has advantages of low cost, energy saving and environmental clean technology comparing to conventional separation processes. Pervaporation is one of new advanced membrane technology applied for separation of azeotropic mixtures, aqueous organic mixtures, organic solvent and petrochemical mixtures. Sodium alginate composite membranes were prepared for the enhancement of long-term stability of pervaporation performance of water-ethanol mixture using pervaporation. Sodium alginate membranes were crosslinked with CaCl$_2$ and coated with polyelectrolyte chitosan to protect washing out of calcium ions from the polymer. The surface structures of PAN and hydrolysed PAN membrane were confirmed by ATR Fourier transform infrared (FT-IR). A field emission scanning electron microscopy (FE-SEM; Jeol 6340F) operated at 15 kV. Concentration profiles for Ca in the membrane surface and membrane cross-section were taken by an energy dispersive X-ray (EDX) analyser (Jeol) attached to the field emission scanning electron microscopy (Jeol 6340F). Pervaporation experiments were done with several operation run times to investigate long-term stability of the membranes.

• 한국환경과학회지
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• 제25권3호
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• pp.417-424
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• 2016

The objective of this study was to evaluate the microwave drying characteristics of mixtures of chemical wastewater sludge (70~90%) and anthracite coal (10~30%) with respect to physical and economic factors such as mass, volume reduction, moisture content, drying rate and heating value when the wastes were dried at different weight mixing ratio and for different microwave irradiation time. The drying process were carried out in a microwave oven, the combined drying process with a 2,450 MHz frequency and 1 kW of power. Maximum dry rates per unit area on the microwave drying of mixtures with chemical wastewater sludge and anthracite coal were $35.5kg\;H_2O/m^2{\cdot}hr$ for Cs90-Ac10; $40.1kg\;H_2O/m^2{\cdot}hr$ for Cs80-Ac20 and $35.0kg\;H_2O/m^2{\cdot}hr$ for Cs70-Ac30. The result clearly indicated that moisture can be effectively and inexpensively removed from the wastes through use of the microwave drying process.

• 한국환경농학회지
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• 제31권4호
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• pp.368-374
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• 2012

BACKGROUND: The urgency of feeding the world's growing population while combating soil pollution, salinization and desertification requires suitable biotechnology not only to improve crop productivity but also to improve soil health through interactions of soil nutrient and soil microorganism. Interest in the utilization of microbial fertilizer has increased. A principle of nature farming is to produce abundant and healthy crops without using chemical fertilizer and pesticides, and without interrupting the natural ecosystem. Beneficial microorganisms may provide supplemental nutrients in the soil, promote crop growth, and enhance plant resistance against pathogenic microorganisms. We mixed beneficial microorganisms such as Bacillus sp. Han-5 with anti-fungal activities, Trichoderma harziaum, Trichoderma longibrachiatum with organic material degrading activity, Actinomycetes bovis with antibiotic production and Pseudomonas sp. with nitrogen fixation. This study was carried out to investigate the mixtures on the soil microflora and soil chemical properties and the effect on the growth of lettuce and cucumber under greenhouse conditions. METHODS AND RESULTS: The microbial mixtures were used with each of organic fertilizer, swine manure and organic+swine manure and compared in regard to changes in soil chemical properties, soil microflora properties and crop growth. At 50 days after the treatment of microorganism mixtures, the pH improved from 5.8 to 6.3, and the EC, $NO_3$-Na and K decreased by 52.4%, 60.5% and 29.3%, respectively. The available $P_2O_5$ and $SiO_2$ increased by 25.9% and 21.2%, respectively. Otherwise, the population density of fluorescent Pseudomonas sp. was accelerated and the growth of vegetables increased. Moreover, the population density of E. coli and Fusarium sp., decreased remarkably. The ratio of bacteria to fungi (B/F) and the ratio of Actinomycetes bovis to fungi (A/F) increased 2.3 (from 272.2 to 624.4) and 1.7 times (from 38.3 to 64), respectively. Furthermore, the growth and yield of cucumber and lettuce significantly increased by the treatment of microorganism mixtures. CONCLUSION(S): These results suggest that the treatment of microorganism mixtures improved the chemical properties and the microflora of soil and the crop growth. Therefore, it is concluded that the microorganism mixtures could be good alternative soil amendments to restore soil nutrients and soil microflora.

• 한국환경농학회지
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• 제40권1호
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• pp.13-19
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• 2021

BACKGROUND: Chemicals such as antibiotics and surfactants can enter agricultural environment and they can be degraded by natural processes such as photolysis. These chemicals exist in mixtures in the environment, but studies on degradation of the mixtures are limited. This study compares the photodegradation of Triton X-100 (TX) and antibiotics [tetracycline (TC) and sulfathiazole (STH)] when they are in a single solution or in mixtures. METHODS AND RESULTS: TC, STH, and TX solutions were exposed to UV-A for the photodegradation tests for 14 days. The residual TC, STH, and TX concentrations were analyzed by using HPLC. The TC degradation was similar regardless of the presence of TX, while the TX degradation was lower in the presence of TC. The STH degradation was similar regardless of the presence of TX, while the TX degradation was greater in the presence of STH. However, the STH degradation was slower in the TC-STH-TX mixture than in the STH-TX mixture. Also, the TX degradation was negligible in the TC-STH-TX mixture. The results show that the photodegradation of TC, STH, and TX can be different in mixtures. This can be attributed to the different emission and absorption wavelengths of each compound and interaction between these compounds and photoproducts. CONCLUSION: Overall, this study emphasizes that photodegradation of single chemicals and chemical mixtures can be different, and more studies on single compounds as well as mixtures are required to understand the fate of chemicals in the environment in order to manage them properly.

• 한국환경보건학회지
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• 제49권2호
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• pp.89-98
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• 2023

Background: Organophosphorus flame retardants (OPFRs) are a group of chemical substances used in building materials and plastic products to suppress or mitigate the combustion of materials. Although OPFRs are generally used in mixed form, information on their mixture toxicity is quite scarce. Objectives: This study aims to elucidate the toxicity and determine the types of interaction (e.g., synergistic, additive, and antagonistic effect) of OPFRs mixtures. Methods: Nine organophosphorus flame retardants, including TEHP (tris(2-ethylhexyl) phosphate) and TDCPP (tris(1,3-dichloro-2-propyl) phosphate), were selected based on indoor dust measurement data in South Korea. Nine OPFRs were exposed to the luminescent bacteria Aliivibrio fischeri for 30 minutes and the human hepatocyte cell line HepG2 for 48 hours. Chemicals with significant toxicity were only used for mixture toxicity tests in HepG2. In addition, the observed EC_x values were compared with the predicted toxicity values in the CA (concentration addition) prediction model, and the MDR (model deviation ratio) was calculated to determine the type of interaction. Results: Only four chemicals showed significant toxicity in the luminescent bacteria assays. However, EC₅₀ values were derived for seven out of nine OPFRs in the HepG2 assays. In the HepG2 assays, the highest to lowest EC₅₀ were in the order of the molecular weight of the target chemicals. In the further mixture tests, most binary mixtures show additive interactions except for the two combinations that have TPhP (triphenyl phosphate), i.e., TPhP and TDCPP, and TPhP and TBOEP (tris(2-butoxyethyl) phosphate). Conclusions: Our data shows OPFR mixtures usually have additivity; however, more research is needed to find out the reason for the synergistic effect of TPhP. Also, the mixture experimental dataset can be used as a training and validation set for developing the mixture toxicity prediction model as a further step.

• 공업화학
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• 제16권4호
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• pp.513-518
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• 2005

혼합비율 및 반응온도의 변화에 따른 ZnO가 첨가된 PVC와 PS의 혼합 열분해 특성에 관한 연구를 TG와 GC-MS를 이용하여 수행하였다. 본 연구로부터 혼합물에 있어서 PS의 양이 증가할수록 액상 생성물은 증가하였으며 기상 생성물은 감소함을 알 수 있었다. 또한 ZnO의 첨가량이 증가할수록 기상 생성물과 염화수소의 발생량은 감소하였으며 염화수소의 발생 억제 및 액상 생성물의 최대수율을 얻기 위한 최적의 반응온도는 $500^{\circ}C$임을 알 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제25권9호
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• pp.1346-1350
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• 2004

Pseudo-first order rate constants $(k_{obs})$ are reported for the following solvolyses in approximately isodielectric mixtures: 3- and 4-methoxybenzyl chloride, bromo- and chlorodiphenylmethane, and 4-chloro-, 4,4'-dichloro and 4-methyl-chlorodiphenylmethane in 0-80% v/v nitromethane-methanol mixtures; and bromo- and chlorodiphenylmethane and 4-methyl-chlorodiphenylmethane in various acetonitrile-methanol mixtures (in the range 0-50% v/v) at$25^{\circ}C.$ These data, and literature data for t-butyl halides (Cl, Br, and I), and for p-methoxybenzoyl chloride, show rate maxima in solvent compositions of ca. 30% aprotic cosolvent, explained by a stoichiometric solvent effect on electrophilic solvation. Linear relationships are observed between $(k_{obs})/[MeOH]^2$ and [AP]/[MeOH], where [AP] refers to the molar concentration of aprotic cosolvent. The results are consistent with competing third order contributions to $k_{obs}$, $k_{MM}[MeOH]^2$ with hydrogen-bonded methanol as electrophile, and $k_{MAP}[MeOH][AP]$ with hydrogen-bonding disrupted by the aprotic solvent.