• Proceedings of the Korea Society of Environmental Toocicology Conference
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• 2002.10a
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• pp.162-162
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• 2002

염소소독 결과 수돗물 중에 존재하는 Dichloroacetic acid(DCAA)와 Trichloroacetic acid(TCAA)는 동물실험 결과 발암성 등 악영향을 일으키는 것으로 알려져 있다. 이러한 화합물들은 수돗물을 사용할 때 열을 가하면 그 농도가 변하게 된다. 이 연구에서는 설문조사를 통해 개인이 하루 동안에 섭취하는 수돗물의 양과 섭취패턴을 조사하고, 각 가정마다 수돗물의 농도를 측정하여 DCAA 및 TCAA에 대한 경구섭취 노출량을 평가하고자 실시하였다. 춘천에 위치하고 있는 60가정을 2002년 1월부터 2월 사이와 7월부터 8월 사이에 방문하여 수돗물을 채취하고, 주부를 대상으로 24시간 동안의 물 사용에 대한 설문을 실시하였으며, 아침 첫 소변을 회수하였다. 수돗물 및 소변 중 DCAA 및 TCAA에 대한 분석은 methyl ester 형태의 유도체를 만든 후 GC/PDECD로 분석하였다. 수돗물을 가열하면 DCAA의 농도는 증가하고, TCAA의 농도는 감소하였고, DCAA 및 TCAA의 경구 섭취량은 수돗물 중의 농도에 섭취부피와 가열시간에 따른 농도변화율을 곱하여 산출하였다. 실험 대상자들의 평균 수돗물 섭취부피는 1.7$\ell$이었고, 평균 가열시간은 10~15분이었다. 추정한 DCAA의 섭취량은 찬 수돗물만을 마시는 것을 가정한 것에 비해 182% 높았고, TCAA에 대해서는 30% 낮았다 이와 같은 결과는 우리나라 사람들의 식생활이 국이나 찌개 및 보리차 등과 같이 가열한 음식이나 음용수를 많이 섭취하기 때문이다. 그러므로 음용수 중 DCAA 및 TCAA의 인체 섭취 노출평가를 하기 위해서는 섭취한 부피뿐만 아니라 가열에 따른 농도 변화도 동시에 고려하여 야 한다.배 센타의 재고 완충역할을 수행하게 한다. 이에 따라 안전 재고 및 역 배송을 최소화 할 수 있을 뿐 아니라 미 출고로 인한 손실을 최소화하며 고객의 서비스를 일정하게 유지시킬 수 있을 것으로 기대된다.증진, 페기물 발생 억제 분야에 상당한 성공을 거두었으며, 지금도 지속적으로 유지 관리 및 미비한 부분(CAER, 등)의 향상에 노력하고 있다. Dow Korea의 수입 판매 부분에 주로 관련된 Product Stewardship 및 Distribution Code는 여러 사업부 및 여러 지역(미국, 유럽, 아시아 등)에 위치한 담당자가 관련된 까닭에 가장 복잡한 부분이어서 많은 인력과 시간을 소비하면서 노력하고 있으나 아직까지 소정의 목표에 도달하지 못했으며, 2000년 말에 모든 실행지침이 실행되도록 목표, 실행 계획 및 조직을 수정하여 노력하고 있다.lumn density at distant position from MD5 is larger than that in the (:entral region. We have deduced that this hot-core has a mass of 10sR1 which i:s about an order of magnitude larger those obtained by previous studies.previous studies.업순서들의 상관관계를 고려하여 보다 개선된 해를 구하기 위한 연구가 요구된다. 또한, 준비작업비용을 발생시키는 작업장의 작업순서결정에 대해서도 연구를 행하여, 보완작업비용과 준비비용을 고려한 GMMAL 작업순서문제를 해결하기 위한 연구가 수행되어야 할 것이다.로 이루어 져야 할 것이다.태를 보다 효율적으로 증진시킬 수 있는 대안이 마련되어져야 한다고 사료된다.$\

• Journal of Korean Society of Environmental Engineers
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• v.28 no.11
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• pp.1135-1140
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• 2006

Concentration and speciation of trihalomethanes(THMs) and haloacetic acids(HAAs) that can be created during chlorine disinfection as disinfection by-products(DBPs) in Korean water treatment plants(WTPs) were investigated. 4 WTPs that adopted conventional water treatment processes were chosen for investigation and each represented a typical WTP on the Han, Keum, Sumjin and Nakdong Rivers. The average concentration of THMs was 26.9 ppb, and the maximum and minimum concentrations were 47.6 ppb and 11.0 ppb respectively, while the average concentration of HAAs was 25.4 ppb, and the maximum and minimum concentrations were 57.1 ppb and 9.7 ppb respectively. DBPs concentration was lower in the winter than the summer. The major species of THMs was chloroform and its average percentage was 77%, and the second highest was bromodichloromethane(20%), while the concentration of bromoform was below detection limits. The sum of dichloroacetic acid(DCAA) and trichloroacetic acid(TCAA) was 97% of $HAA_5 $ on average base. But its percentage was 90% in the Han River WTP, especially it was the lowest during the winter. On the other hand, the concentration of DCAA was higher than TCAA except during the summer.

• Journal of Korean Society on Water Environment
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• v.20 no.3
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• pp.275-280
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• 2004

This study was performed to investigate the disinfection efficiency and the formation characteristics of disinfection by-products(DBPs) by chlorination in the sewage effluent. The effluent was sampled from the sewage treatment plants operated in the activated sludge process and the advanced sewage process. The type of DBPs investigated were Trihalomethanes(THMs), Dichloroacetonitrile(DCAN), Chloral hydrate(CH), Dichloroacetic acid(DCAA), Trichloroacetic acid(TCAA). Major findings are as follows. First, the optimum injection concentration for chlorination in sewage effluent were found to be in the range $0.5{\sim}1.0mg\;cl_2/L$. Also, It was found that the chlorine dosage in the effluent of activated sludge process was higher than in the effluent of advanced sewage process. Second, the maximum formation concentration of THMs were $12.7{\mu}g/L$. The THMs formation reaction was finished in a short time of several seconds and chloroform was mainly formed. Also, it was found that the concentration of ammonium nitrogen is higher, the concentration of THMs is lower. Third, it was found that DCAA and TCAA were mainly formed as DBPs by disinfection.

• Progress in Medical Physics
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• v.27 no.4
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• pp.175-179
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• 2016

In this study, we evaluated the reusable leuco malachite green (LMG) micelle gel properties dependent on various components of chemical concentration and compared with leuco crystal violet (LCV). The gels were delivered to 10, 20, 30, 40 and 50 Gy at 6 MV photon beam from linear accelerator and analyzed using spectrophotometry. We confirmed that the reusable LMG and LVC absorbance wavelength peak were made up at 630 nm and 600 nm respectively. The transparency of reusable LMG decreased with higher amount of trichloroacetic acid (TCAA) and lower reusable LMG dyes. 1 mM reusable LMG was the lowest transparency. The sensitivity was increased depending on lower trichloroacetic acid (TCAA) concentrations and the amount of suitable surfactant (Triton X-100), which was found to be 7 mM. However, we were not able to investigate sensitivity effects factor from reusable LMG dyes. The gel dosimeter containing 16 mM TCAA, 7 mM Triton X-100 gel dosimeter showed the highest sensitivity at $0.0021{\pm}0.0001cm^{-1}.Gy^{-1}$. The sensitivity of LCV was found to be higher than reusable LMG at $0.0037{\pm}0.0005cm^{-1}.Gy^{-1}$. The reusable LMG and LCV dose responses were shown to be $R^2=0.997$, $R^2=0.999$ respectively, as stable measurement results. Future research is necessary to improve dose sensitivity, dose rate dependency and gel fading with extensive chemical formulations.

• Korean Journal of Food Science and Technology
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• v.51 no.1
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• pp.12-17
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• 2019

Dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) in fresh-cut salads available from the market were determined by gas chromatography-mass spectrometry (GC-MS). The target compounds in 3 g of acidified homogenates were extracted with 20 mL of methyl t-butyl ether (MTBE). The extract was concentrated to 1 mL and heated for 1 h at $55^{\circ}C$. The analytes were separated using a DB-1701 column and detected with a mass spectrometer. The method detection limit was approximately $6{\mu}g/kg$, and both analytical accuracy and precision were found to be satisfactory. The linearity of the calibration curves expressed as the coefficients of determination was >0.996. The analysis of seven samples using the established method showed that the four samples contained considerable amounts of analytes ($25.4-31.2{\mu}g/kg$ of DCAA and $18.8-46.1{\mu}g/kg$ of TCAA). These results raised a concern about the impact of fresh-cut salad consumption on human health.

• Environmental Analysis Health and Toxicology
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• v.14 no.1_2
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• pp.35-43
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• 1999

A number of disinfection by-products (DBPs) are formed as a result of the addition of chlorine into the public water supply and some of them have been suggested to cause adverse health effects on humans. However, the estimation of human ingestion exposure to each DBP has been performed simply by multiplying the concentration of a chemical in the cold tap water by the volume of water consumed during a given period of time. However, a questionnaire concerning water consumptions administered to sixty people residing in Chunchon showed that the volume of tap water consumed accounted for approximately 70% of the total volume of water consumed and that of heated water represented approximately 94% of tap water ingested. Heating durations for water-containing foods (e. g., soups and pot stews) and heated beverages (e. g., barley tea) were grouped into 10, 20, 30, and 35 minutes. Based on these time frames, an aluminum pot containing one liter of tap water was heated for the above respective time periods using a gas range to determine the variations of the concentrations of individual DBPs by heating. The pH and total residual chlorine were measured before and after heating. Collected water samples were carried to the laboratory and analyzed for eight DBPs and total organic carbon. Chloroform, bromodichloromethane, chloral hydrate, 1, 2-dichloro-2-propanone, 1, 1, 1-trichloropropanone, and dichloroacetonitrile were not detected following heating for 10 minutes and longer. The concentration of dichloroacetic acid (DCAA) was elevated with heating duration, resulting in the averages of 2.0, 3.1, 4.7, and 12 times the initial concentration, respectively, for 10, 20, 30, and 35 minute heating periods. On the other hand, the concentration of trichloroacetic acid (TCAA) decreased with heating duration, with 0.65, 0.40, 0.34, and 0.19 times lower than the initial concentration. Therefore, it is suggested that ingestion exposure to DCAA increases with heating duration but that ingestion exposure to TCAA decreases. In addition, while the amount of DCAA was elevated at the initial time periods (10 or 20 minutes) and then slowly decreased, that of TCAA was rapidly decreased. In conclusion, water-heating processes during cooking influence the concentrations of individual DBPs in the tap water, with lower levels for volatile DBPs and TCAA, and higher levels for DCAA. Therefore, concentration change needs to be taken into consideration in the estimation of human ingestion exposure to DBPs.

• Journal of Environmental Health Sciences
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• v.32 no.4 s.91
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• pp.262-267
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• 2006

DBPs and T&O(taste-and-odor) compounds in drinking water is one of main source to deteriorate water quality. So, these compounds can cause adverse health effects and result in many consumer complaints aesthetically. This experiments carried out to investigate the effect of boiling water on DBPs and T&O compounds in the tap water. THMs and TCM concentration were reduced by 91.3%, 88.9% after 5 min of boiling, respectively. It is certainly, resulted from volatilization of TCM. TCAA concentration decreased when the water was boiled, too. By contrast, the concentration of DCAA was increased with duration time from boiling-point. The reduction of TCAA from the boiled water can be attributed to chemical transformation like decarboxylation. T&O compounds such as geosmin and 2-MIB was effectively removed by boiling of water, resulting in the removal efficiency of 97.1%, 94.4% after 5 min of boiling, respectively.

• Journal of Environmental Science International
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• v.15 no.8
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• pp.785-797
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• 2006

The formation characteristics of trihalomethanes (THMs) and haloacetic acids (HAAs) were investigated in chlorination of raw water of different organic mallet characteristics. The samples used in this study were hydrophobic (N-HPO) and hydrophilic fraction (N-HPI) (which were concentrated and separated from Nakdong river water), and humic acid (HA) (which is known as a strong hydrophobic acid) as a reference organic matter, the specific UV absorbance (SUVA) of which was 2.19, 1.15 and 7.92, respectively. With increasing chlorine contact time, THMFP and HAAFP (the formation potential of THMs and HAAs) increased, but their increase was different depending on the organic mallet characteristics (i.e., for N-HPI, THMFP was higher than HAAFP, but the inverse result was obtained for N-HPO and HA and the ratio between them was greater for HA), and the mainly formed chemical species were CHCI$_3$ in case of THMs and dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) in case of HAAs for N-HPO and HA (and the ratios of CHCI$_3$ to total THMs and DCAA and TCAA to total HAAs for HA were higher than those for N-HPO), but for N-HPI, the ratio of brominated THMs was a little higher than that of CHCI$_3$ and the ratio of DCAA and TCAA to total HAAs was lower than that of N-HPO, although they are main chemical species in case of HAAs. Comparing THMFP and HAAFP with the increase in bromide concentration added with those in not adding it, the former increased greatly and its increase was higher for the organic mallet with stronger hydrophobicity, but the latter was lower for N-HPO and N-HPI and was similar for HA. The main chemical species with increasing bromide concentration were CHBt$_3$ in case of THMs regardless of organic matter characteristics, and dibromoacetic acid (DBAA) for N-HPO and N-HPI, DBAA and tribromoacetic acid (TBAA) for HA in case of HAAs. With increasing reaction temperature and pH, THMFP and HAAFP increased for the former, but for the latter, THMFP increased and HAAFP decreased, although the rate of increase or decrease was different with organic mallet characteristics.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.7
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• pp.762-770
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• 2005

Adsorption and biodegradation performance of chlorinated by-products such as trihalomethanes(THMs) and haloacetic acids(HAA5) on granular activated carbon were evaluated in this study. The coconut-based activated carbon was found more effective than others in adsorption of THMs due to larger pore volume of less than $20{\AA}$. The wood-based activated carbon was less effective than coconut- and coal-based activated carbon in adsorption nevertheless having larger pore volume and specific surface area than others. The maximum adsorption capacity(X/M) of coconut-based carbon for THMS was 1.1-1.5 times larger than coal based carbon and 14.1-31.4 times larger than wood based activated carbons. Activated carbon usage rate(CUR) of coconut-, coal- and wood-based activated carbons for chloroform were 9.4, 11.2 and 38 g/day respectively. In the evaluation of adsorption isotherm of THM species for coconut-, coal- and wood-based activated carbons, k value of chloroform was the lowest in the THM species, It menas that chloroform is difficult to remove by activated carbon adsorption. and BDCM, CDBM, bromoform are in the succeeding order of adsorption. In the evaluation of biodegradation rate, mean biodegradation rate was chloroform 7%, BDCM 5%, CDBM 4% and bromoform 3%, respectively THMs are difficult materials to be biodegraded. In the evaluation of characteristics of adsorption and biodegradation for HAA5 species, HAA5 species appear to be removed effectively by activated carbon. Most of the HAA5 are adsorbed at the beginning of operation periods and HAA5 except TCAA were almost biodegraded from bed volume of 2,000 and more than 90 percent of biodegradation of TCAA was started from bed volume around 4,000 and after that biodegradation rate was increased with increasing bed volume.

• Korean Chemical Engineering Research
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• v.44 no.2
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• pp.216-226
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• 2006

Total trihalomethanes (THMs), dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) that are the major disinfection byproducts (DBPs) are monitored continuously in drinking water in Seoul. Study on characteristics of DBPs is crucial to judge the safety of drinking water in Seoul. Analysis of THMs, haloacetonitriles (HANs), chloral hydrate (CH), and haloacetic acids (HAAs) was carried out in several distribution systems from January 2002 to December 2004. The concentration of THMs was 0.015 mg/L in purified water, 0.019 mg/L in tapwater by direct service, and 0.023 mg/L in tapwater through watertank, respectively. It might be due to the increased contact time with chlorine by a process of the distribution system. And the other DBPs show a tendency to increase in its concentration by a process of the distribution system. Also, in summer, the concentration of DBPs was higher than in spring and winter. It might be due to the higher temperature of water in summer. In all cases, the quantities of detected DBPs were 4-6 times lower than those of regulation limits of drinking water in Seoul. In view of these results, the tapwater in Seoul is good to drink it all the times.