• 한국지하수토양환경학회:학술대회논문집
• /
• 한국지하수토양환경학회 2003년도 총회 및 춘계학술발표회
• /
• pp.63-66
• /
• 2003

This study applied a hydrogeological field survey and isotope investigation to identify source locations and delineate pathways of groundwater contamination by nitrogen compounds. The infiltration and recharge processes were analyzed with groundwater-level fluctuation data and oxygen-hydrogen stable isotope data. The groundwater flow pattern was investigated through groundwater flow modeling and spatial and temporal variation of oxygen isotope data. Based on the flow analysis and nitrogen isotope data, source types of nitrate contamination in groundwater are identified. Groundwater recharge largely occurs in spring and summer due to precipitation or irrigation water in rice fields. Based on oxygen isotope data and cross-correlation between precipitation and groundwater level changes, groundwater recharge was found to be mainly caused by irrigation in spring and by precipitation at other times. The groundwater flow velocity calculated by a time series of spatial correlations, 231 m/yr, is in good accordance with the linear velocity estimated from hydrogeologic data. Nitrate contamination sources are natural and fertilized soils as non-point sources, and septic and animal wastes as point sources. Seasonal loading and spatial distribution of nitrate sources are estimated by using oxygen and nitrogen isotopic data.

• 한국물환경학회지
• /
• 제34권1호
• /
• pp.26-32
• /
• 2018

In order to analyze the effects of sediment on the occurrence of algal bloom on the Giheung Reservoir, the contamination levels of sediments were evaluated. The concentrations of various organic compounds (ignition loss), as well as the total nitrogen, total phosphorus, and heavy metals (Zn, Cr, Co, Ni, Pb, As, Hg, Cd) were analyzed in the sediments taken at eighteen sites of the reservoir. The concentrations of ignition loss and total nitrogen tended to increase from upstream to downstream, and ranged from 4.38 to 12.93% and 2,153 to 4,723 mg/kg, respectively. Heavy metals were in the order of Zn>Cr>Co>Ni>Pb>As>Hg, and the contamination level of the heavy metals was not high as a whole. The concentrations of the total phosphorus were in the range of 765 ~ 3,238 mg/kg, which exceeded the contamination level of the "Sediment Quality Assessment Guideline of River and Lake Sediment (Rule No. 2015-687 of the National Institute of Environmental Research, Korea)" at two upstream sites, four downstream sites, and all downstream sites. These results indicated that the pollution level of the total phosphorus, which is the main factor related to algal bloom, was found to be serious. Therefore, it is necessary to establish a countermeasure for sediment management in order to control the algal bloom which occurs periodically in the reservoir.

• 방사성폐기물학회지
• /
• 제3권3호
• /
• pp.159-165
• /
• 2005

원자력 시설의 해체 시 발생되는 다양한 종류의 폐기물 중에서 배관류를 재활용하거나 처분하기 위해서는 배관 내부의 정확한 방사선학적인 오염 특성의 평가가 선행되어야 한다. 그러나 기존의 측정법인 survey-meter를 이용한 오염도의 직접 측정은 배관 내부와 같은 국소지역의 오염 특성을 정확하게 평가할 수 없으며, 간접법을 이용한 표면오염도 측정의 경우도 시료채취의 어려움뿐만 아니라 시료채취 시 작업자의 오염 가능성이 있기 때문에 적용성에 많은 문제점이 있다. 본 연구에서는 Monte Carlo 모사기법을 이용해 직경이 작은 배관 내부의 베타선 오염도를 측정하기 위하여 플라스틱 섬광체를 모사하였으며, 모사 결과에서 베타선 에너지를 효율적으로 측정할 수 있는 최적의 플라스틱 섬광체 두께 및 형상을 도출할 수 있었다. 이 전사모사 결과를 바탕으로 섬광체의 가공 및 배관 내부에서의 검출기 이송 문제를 고려해 검출기를 제작하였으며 그 특성을 평가하였다. 그 결과 배관 내부의 오염도 측정에 적합한 검출기 성능을 확인하였고, 파이프 내부처럼 국소 지역의 방사선학적 오염 특성 평가를 위한 검출기 개발 가능성을 확인하였다.

• Journal of Korean Biological Nursing Science
• /
• 제13권3호
• /
• pp.204-210
• /
• 2011

Purpose: The purpose of this study was to provide basic data for the guidelines for cleaning the feeding bags by comparing the level of contamination according to cleaning and disinfection methods when feeding tube of Neurosurgery Intensive Care Unit patients. Methods: This study was a true-experimental study, with 48 cases in total. The feeding bag of 48 patients were randomly assigned to detergent cleaning method or disinfectant decontamination method. The period of the experiment was January to July 2008, and enteral nutrition was given within 30 minutes for 2 hours, 4 times a day at 7AM, noon, 5PM, and 9PM for seven days. Feeding bags were cleaned after each feeding according to the assigned cleaning and disinfection method followed by microbial cultures on 4th and 8th day before the 7AM feeding. Results: After three and seven days of feeding and cleaning, the level of contamination was significantly lower when bags were cleaned with disinfectant than cleaning with detergent and tepid water. Conclusion: In cases where feeding bags are reused, for example, intensive care unit and home care settings, study findings indicate that cleaning bags with disinfectant is an effective way to prevent contamination of bags.

• KEPCO Journal on Electric Power and Energy
• /
• 제7권2호
• /
• pp.317-321
• /
• 2021

As the large-scale renewable energy power plant increases, the high-capacity and compact Energy Storage System (ESS) is required. However, this trend could reduce the insulation reliability of ESS. In this study, the surface flashover characteristics for four types of solid insulators are investigated in the uniform electric field with AC and Lightning Impulse (LI) voltage waveforms under various contamination levels. In addtion, insulator surfaces are compared based on the contact angle before and after surface flashover. The experimental results show that AC flashover voltage is dependent on the materials and the contamination level, but LI flashover voltage is only associated with the contamination level. Especially, AC flashover voltage of PC (PolyCarbonate) is higher than that of other insulators, which is associated with the unique and sequential creepage discharge propagation pattern of PC. The localized discharges on the surface of PC form corresponding tracking points. Then, the interconnected trackings result in the complete flashover. This flashover patterns degrade the surface of PC much more than that of epoxy and Bulk Molding Compoud (BMC). Thus, the contact angle of PC is significantly reduced compared to that of other insulators. The increased hydrophilicity in the surface of PC enhances the insulator surface conductivity.

• Nuclear Engineering and Technology
• /
• 제34권5호
• /
• pp.415-420
• /
• 2002

The previous dynamic food chain model was improved for the consideration of the influence of radioactive contamination to agricultural products due to rain during the environmental releases of radionuclides in a nuclear accident Wet interception coefficients for the agricultural plants were derived as a function of radionuclide and rainfall amount, and mathematical formulations of the previous model were modified. As a result, rain during accidental releases was influential in agricultural contamination. The contamination level of agricultural products decreased dramatically according to increasing rainfall amount. It means that predictive concentrations in agricultural products using the previous model, in which dry interception to the agricultural plants is only considered, can be overestimated. The influence of rainfall in agricultural contamination was the most sensitive for $^{131}$ I, and the least sensitive for $^{90}$ Sr among the radionuclides considered in this study.

• 대한안전경영과학회지
• /
• 제17권4호
• /
• pp.241-246
• /
• 2015

Generally a patient who was injected radiopharmaceuticals for nuclear medicine examination is not an object of isolation. Therefore, when the patient uses toilet, we expect surface contamination of a toilet by radioisotope. The measured value is $25.69Bq/cm^2$(a restroom near admission and administration), $19.39Bq/cm^2$(a toilet near department of radiology). The study shows that 9 of 24 locations in controlled area exceed over surface contamination limit. From now on, we should find source of contamination through measurement radioactive nuclide to apply radiation safety management.

• 한국동물위생학회지
• /
• 제24권2호
• /
• pp.117-126
• /
• 2001

To ensure the safety of domestic livestock products, the government made it obligatory to enforce the hazard analysis critical control point(HACCP) in all domestic slaughterhouses. Under the HACCP, most of the hazards generated in slaughterhouses are bio-hazards, especially pathogenic bacteria. In order to reduce to the pathogenic bacteria, critical control point (CCP) is established and controled in the process of slaughter. A study was carried out to measure the level of bacterial contamination of swine carcass in 6 slaughterhouses selected. As a result, the aerobic plate counts(cfu/$\textrm{cm}^2$) of all samples was $10^2$-10 in average, except slaughterhouse C. The level of the aerobic plate counts on the surface of lower loin in slaughterhouse C was $10^4$ and it was considered that slaughterhouse C should set the process of manual transport of carcass as the CCP. Escherichia coli level was the highest in middle line cut surface. Especially, E coli level of slaughterhouses C and D were about 6.5- and 3.0-fold higher than that of other 4 slaughterhouses. Thus, it was considered that the slaughterhouses C and D should set the process of the entrails treatment as the CCP. The air contamination was measured at two point in a slaughterhouse. The air contamination level was 4-13 times higher than that of the standard Japanese slaughterhouses.

• 농업과학연구
• /
• 제41권1호
• /
• pp.35-40
• /
• 2014

This study was carried out to evaluate the Salmonella cross contamination at retail chicken meat outlets in Kandy, Sri Lanka and to identify the risk factors for Salmonella contamination at retail chicken meat outlets. Fifteen retail chicken meat outlets in Kandy area were randomly selected. Pre-tested questionnaires were used to collect data for identifying risk factors of Salmonella cross contamination at retail outlets and swab samples from meat contact surfaces/utensils were obtained. Out of 57 swab samples collected from meat contact surfaces/utensils, the overall prevalence of Salmonella cross contamination was 21%. Weighing scale (33%), meat containing trays/buckets (27%) and cutting board (25%) showed the highest percentage of Salmonella prevalence whereas knife and showcase showed relatively low percentages, 14% and 9%, respectively. Retail chicken outlets with slaughtering facilities had a significantly higher prevalence of Salmonella cross contamination than those without slaughtering facilities. This higher rate of Salmonella cross contamination at retail chicken meat outlets could be attributed to lack of proper cold chains and minimal facilities, and poor level of hygiene in those outlets.

• 한국환경보건학회지
• /
• 제29권1호
• /
• pp.19-27
• /
• 2003

Coliforms is currently being used as the standard of environmental water qualify to evaluate the level of source water quality especially condition of fecal contamination. However, not properly applied to water quality management. So in this study, in addition to Coliforms, fecal contamination indicator bacteria turk at Feral Coliforms(FC), E. coli, Fecal streptococci(FS), Clostridium and environmental parameters related with it's distribution were investigated on a monthly basis in 6 water intakes of Han River. The mean of BOD, DO, SS and pH, benchmarks of source water management were maintained the second grade of environmental water quality standard applied to Han River but Coliforms exceeded it. Distribution of Coliforms ranged from 1.0×10¹ to 2.7 10/sup 5/ CFU/ml, FC ranged from ND to 5.3×10¹ CFU/ml, E. coli ranged from ND to 9.2×10¹ CFU/ml, FS ranged from ND to 2.5×10¹CFU/ml, they were steepy rise on July and August in common when rainfalls was heavy and water temperature was high, but Clostridium perfringens ranged from 1.7×10¹to 1.7×10¹CFU/ml not fluctuate by month. Statistical analysis of sampling data showed that most significant correlations occurred among FC and Coliforms(r = 0.840), E. coli(r = 0.792), FS(r = 0.687) and environmental parameters(temperature, turbidity, SS, rotor were all r > 0.60) while no significant correlation was observed between ammonia generally recognized fecal contamination indicator and bacteria. Identification of the coliforms showed that Enterobacter, Klebsiella, Citrobacter were comprised of 32%, 24%, 16% respectively, and E. coli were 7% of it. while E. coli was made up 85.9% of FC. The mean value of FC/Coliforms ratio, 5.2(0.1-42) were higher in Amsa, Guui than Jayang. Fecal coliforms, as those are able to reflect more particularly the extent of the fecal contamination, were considered useful in deciding the level of water treatment while monitoring the fecal contamination from the source of water supply. Therefore, it is expected that the water quality is going to be managed more efficiently by using fecal coliforms supplementarily to total coliforms which are current standard item of water-quality environment.