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  • Effects of multifunctional weir construction on key water quality indicators: a case study in Nakdong River, Korea

    International Journal of Environmental Science and Technology

     

    Authors : C. D. Jo1, C. G. Lee1 & H. G. Kwon

    ISSN : 1735-1472


    Abstract
      In this study, changes in water quality characteristics were compared before and after the construction
    of eight multifunctional weirs in the Nakdong River Basin in South Korea. A cluster analysis of spatial
    variation showed that the locations classified as Cluster 1 pre-construction (sites ND7 and ND8) shifted
    into Cluster 2 post-construction, indicating that spatial cluster types changed after the construction of
    multifunctional weirs. Principal component and factor analyses revealed that nitrogen and phosphorous
    nutrients at the pre-construction stage (total nitrogen, total phosphorous, and phosphate-phosphorus)
    and electrical conductivity were extracted in principal component 1, while biochemical oxygen demand,
    chemical oxygen demand, pH, and chlorophyll-a were extracted in principal component 2. However,
    biochemical oxygen demand, chemical oxygen demand, total organic carbon, and chlorophyll-a at the
    post-construction stage were extracted in principal component 1, while total nitrogen, nitrate-nitrogen,
    and dissolved oxygen were extracted in principal component 2. The key water quality indicators
    transitioned from nutrients to organic pollutants after the construction of the multifunctional weirs.
    A water quality trend analysis with seasonal Mann Kendall testing and locally weighted scatter plot
    smoothing methods showed that organic pollutant indicators such as chemical oxygen demand and
    total organic carbon tended to increase after the construction of multifunctional weirs. Therefore,
    the key quality indicators for water quality improvement and management should be chemical oxygen
    demand and total organic carbon.


    Keyword : -

    Link  : https://link.springer.com/article/10.1007/s13762-022-03973-8

  • Geostationary satellite-derived ground-level particulate matter concentrations using real-time machine learning in Northeast Asia

    ENVIRONMENTAL POLLUTION

     

    Authors : Seohui Park, Jungho Im, Jhoon Kim, Sang-Min Kim

    ISSN : 0269-7491


    Abstract
      Rapid economic growth, industrialization, and urbanization have caused frequent air pollution events
    in East Asia over the last few decades. Recently, aerosol data from geostationary satellite sensors have
    been used to monitor ground-level particulate matter (PM) concentrations hourly. However, many studies
    have focused on using historical datasets to develop PM estimation models, often decreasing their
    predictability for unseen data in new days. To mitigate this problem, this study proposes a novel real-time
    learning (RTL) approach to estimate PM with aerodynamic diameters of <10 μm (PM10) and <2.5 μm (PM2.5)
    using hourly aerosol data from the Geostationary Ocean Color Imager (GOCI) and numerical model outputs
    for daytime conditions over Northeast Asia. Three schemes with different weighting strategies were evaluated
    using 10-fold cross-validation (CV). The RTL models, which considered both concentration and time as
    weighting factors (i.e., Scheme 3) yielded consistent improvement for 10-fold CV performance on both
    hourly and monthly scales. The real-time calibration results for PM10 and PM2.5 were R2 = 0.97 and 0.96,
    and relative root mean square error (rRMSE) = 12.1% and 12.0%, respectively, and the 10-fold CV results
    for PM10 and PM2.5 were R2 = 0.73 and 0.69 and rRMSE = 41.8% and 39.6%, respectively. These results
    were superior to results from the offline models in previous studies, which were based on historical data
    on an hourly scale. Moreover, we estimated PM concentrations in the ocean without using land-based variables,
    and clearly demonstrated the PM transport over time. Because the proposed models are based on the RTL
    approach, the density of in-situ monitoring sites could be a major uncertainty factor. This study identified
    that a high error occurred in low-density areas, whereas a low error occurred in high-density areas. The
    proposed approach can be operated to monitor ground-level PM concentrations in real-time with uncertainty
    analysis to ensure optimal results.


    Keyword : Particulate matter, AOD, Satellite, Machine learning, Real-time learning

    Link  : https://doi.org/10.1016/j.envpol.2022.119425

  • Identifying pollution sources of sediment in Lake Jangseong, Republic of Korea, through an extensive survey: Internal disturbances of past aquaculture sedimentation

    ENVIRONMENTAL POLLUTION

     

    Authors : Tae-Woo Kang, Hae Jong Yang, Jong Hak Han, Young-Un Han, Min-Seob Kim, Jihyun Kim, Soon Hong Hwang, Eun Hye Na, Yoon-Seok Chang

    ISSN : 0269-7491


    Abstract
      Lake sediments are important sinks of various pollutants and preserve historical pollution records
    caused by anthropogenic activities. Recently, the sediments of Lake Jangseong, South Korea were first
    detected with high concentrations of organic matter (ignition loss [IL]; total organic carbon [TOC]),
    nutrients (total nitrogen [TN]; total phosphorus [TP]), and some heavy metals (Zn, Cu, Cd, and Hg).
    Here, we identified the origins of these concentrations accumulated in the sediments using extensive
    surveys and various assessments. Sediment pollution assessed by sediment quality guidelines, pollution
    load index, and potential ecological risk index was found to be of serious concern for IL, TN, TP, and Cd.
    Thus, we assessed pollution sources through spatial, grid, and vertical distributions and found that the
    high pollutant concentrations detected in 2020 were confirmed only at a certain location in the lake.
    Additionally, similar results were detected in the sedimentary layer below a sediment core at a depth
    of 15.0 cm. The high pollutant concentrations locally occurred around a “hotspot” site that was previously
    frequently used for aquaculture activities, indicating that the pollutants were accumulated in sediments
    owing to past cage fish farming rather than from influx of externally sourced pollution. Furthermore,
    chemical fractionation of phosphorus and heavy metals and assessment of stable isotopes (13C and 15N)
    of organic matter suggested that the pollutants in the sediments at the “hotspot” sites had different
    origins than those found at other sites. Accordingly, the by-products discharged after cage fish farming,
    such as residual feed, fish meal, and waste, accumulated in the sediments and were then exposed to
    natural internal disturbances caused by the effects of climate change-induced drought. This local
    distribution and the phosphorus and heavy metal chemical fraction results with low elution potential
    indicated that the pollutants in the sediments of Lake Jangseong had negligible impact on water quality.


    Keyword : Lake sediment, Cage fish farming, Internal disturbance, Sediment core, Phosphorus, Cadmium

    Link  : https://doi.org/10.1016/j.envpol.2022.119403

  • Contribution of liquid water content enhancing aqueous phase reaction forming ambient particulate nitrosamines

    ENVIRONMENTAL POLLUTION

     

    Authors : Na Rae Choi a, Seungshik Park, Seoryeong Ju, Yong Bin Lim, Ji Yi Lee, Eunhye Kim, Soontae Kim, Hye Jung Shin, Yong Pyo Kim

    ISSN : 0269-7491


    Abstract
      Contribution of liquid water content (LWC) to the levels of the carcinogenic particulate nitro(so)
    compounds and the chemistry affecting LWC were investigated based on the observation of seven
    nitrosamines and two nitramines in rural (Seosan) and urban (Seoul) area in South Korea during
    October 2019 and a model simulation. The concentrations of both the total nitrosamines and
    nitramines were higher in Seosan (12.48 ± 16.12 ng/m3 and 0.65 ± 0.71 ng/m3, respectively) than
    Seoul (7.41 ± 13.59 ng/m3 and 0.24 ± 0.15 ng/m3, respectively). The estimated LWC using a
    thermodynamic model in Seosan (12.92 ± 9.77 μg/m3) was higher than that in Seoul (6.20 ± 5.35 μg/m3)
    mainly due to higher relative humidity (75 ± 9% (Seosan); 62 ± 10% (Seoul)) and higher concentrations
    of free ammonia (0.13 ± 0.09 μmol/m3 (Seosan); 0.08 ± 0.01 μmol/m3 (Seoul)) and total nitric acid
    (0.09 ± 0.07 μmol/m3 (Seosan); 0.04 ± 0.02 μmol/m3 (Seoul)) in Seosan while neither fog nor rain
    occurred during the sampling period. The relatively high concentrations of the particulate nitrosamines
    (>30 ng/m3) only observed probably due to the higher LWC (>10 μg/m3) in Seosan. It implies that
    aqueous phase reactions involving NO2 and/or uptake from the gas phase enhanced by LWC could
    be promoted in Seosan. Strong correlation between the concentrations of nitrosodi-methylamine (NDMA),
    an example of nitrosamines, simulated by a kinetic box model including the aqueous phase reactions
    and the measured concentration of NDMA in Seosan (R = 0.77; 0.37 (Seoul)) indicates that the aqueous
    phase reactions dominantly enhanced the NDMA concentrations in Seosan. On the other hand, it is
    estimated that the formation of nitrosamines by aqueous phase reaction was not significant due to the
    relatively lower LWC in Seoul compared to that in Seosan. Furthermore, it is presumed that nitramines
    are mostly emitted from the primary emission sources. This study implies that the concentration of the
    particulate nitrosamines can be promoted by aqueous phase reaction enhanced by LWC.


    Keyword : Nitrosamines, Nitramines, Atmospheric reaction, Liquid water conten, Free ammonia, Seoul, Seosan

    Link  : https://doi.org/10.1016/j.envpol.2022.119142

  • Long-Term Trend of the Levels of Ambient Air Pollutants of a Megacity and a Background Area in Korea

    Applied Sciences-Basel

     

    Authors : Na Kyung Kim, Yong Pyo Kim, Hye Jung Shin, Ji Yi Lee

    ISSN : ****-****


    Abstract
      It is imperative to understand the changes of the levels of air pollutants in Northeast Asia with
    respect to the changes of the emissions of air pollutants. In this study, we analyzed long-term
    trends of both the chemical composition of fine particles and gaseous species in Seoul, a megacity,
    and Baengnyeong Island, a background area located in the Yellow Sea of Republic of Korea
    (South Korea) from 2012 to 2019. Long-term changes of the concentrations of air pollutants were
    analyzed using the Mann Kendall trend test and Sen’s slope. Since the SO2 emissions in this region
    have been significantly reduced during last decade, NO3  has become the major species of fine
    particles instead of SO42 . Seoul and Baengnyeong Island are rich in NH4+ in the atmosphere, and
    due to the SO2 emission reduction, the balance of ammonia nitric acid sulfuric acid has been changed,
    and the concentration of NO3  has increased. This trend is more obvious in Baengnyeong Island than
    Seoul due to the lower local emissions in Baengnyeong Island. As a result of this study, it is possible
    to confirm that concentrations of air pollutants and the majority of aerosols affecting PM2.5
    concentrations in Northeast Asia have changed according to the changes in emissions in this region.


    Keyword : emission changes, nitrate, NOR, SOR, sulfate

    Link  : https://pure.ewha.ac.kr/en/publications/long-term-trend-of-the-levels-of-ambient-air-pollutants-of-a-mega

  • Source apportionment of PM2.5 in Seoul, South Korea and Beijing, China using dispersion normalized PMF

    SCIENCE OF THE TOTAL ENVIRONMEN

     

    Authors : Jieun Park a, Hyewon Kim b, Youngkwon Kim c, Jongbae Heo d, Sang-Woo Kim e, Kwonho Jeon f, Seung-Muk Yi a, c, Philip K. Hopke

    ISSN : 0048-9697


    Abstract
      East Asian countries experience severe air pollution owing to their rapid development and
    urbanization induced by substantial economic activities. South Korea and China are among the
    most polluted East Asian countries with high mass concentrations of PM2.5. Although the
    occurrence of transboundary air pollution among neighboring countries has been recognized for
    a long time, studies involving simultaneous ground-based PM2.5 monitoring and source
    apportionment in South Korea and China have not been conducted to date. This study performed
    simultaneous daily ground-based monitoring of PM2.5 in Seoul and Beijing from January to
    December 2019. The mass concentrations of PM2.5 and its major chemical components were analyzed
    simultaneously during 2019. Positive matrix factorization (PMF) as well as dispersion normalized PMF
    (DN-PMF) were utilized for the source apportionment of ambient PM2.5 at the two sites. 23 h average
    ventilation coefficients were applied for daily PM2.5 chemical constituents' data. Nine sources were
    identified at both sites. While secondary nitrate, secondary sulfate, mobile, oil combustion, biomass
    burning, soil, and aged sea salt were commonly found at both sites, industry/coal combustion and
    incinerator were identified only at Seoul and incinerator/industry and coal combustion were identified
    only at Beijing. Reduction of the meteorological influences were found in DN-PMF compare to C-PMF
    but the effects of DN on mobile source were reduced by averaging over the 23 h sampling period.
    The DN-PMF results showed that Secondary nitrate (Seoul: 25.5%; Beijing: 31.7%) and secondary sulfate
    (Seoul: 20.5%; Beijing: 17.6%) were most dominant contributors to PM2.5 at both sites. Decreasing
    secondary sulfate contributions and increasing secondary nitrate contributions were observed at both sites.


    Keyword : PM2.5, Source apportionment, Positive matrix factorization (PMF), Dispersion normalized PMF (DN-PMF), Potential source contribution function (PSCF), Conditional bivariate probability function (CBPF)

    Link  : https://doi.org/10.1016/j.scitotenv.2022.155056

  • Simultaneous feature engineering and interpretation: Forecasting harmful algal blooms using a deep learning approach

    WATER RESEARCH

     

    Authors : TaeHo Kim a, Jihoon Shin, DoYeon Lee, YoungWoo Kim, Eunhye Na, Jong-hwan Park, Chaehong Lim, YoonKyung Cha

    ISSN : 0043-1354


    Abstract
      Routine monitoring for harmful algal blooms (HABs) is generally undertaken at low temporal frequency
    (e.g., weekly to monthly) that is unsuitable for capturing highly dynamic variations in cyanobacteria abundance.
    Therefore, we developed a model incorporating reverse time attention with a decay mechanism (RETAIN-D)
    to forecast HABs with simultaneous improvements in temporal resolution, forecasting performance, and
    interpretability. The usefulness of RETAIN-D in forecasting HABs was illustrated by its application to two
    sites located in the lower sections of the Nakdong and Yeongsan rivers, South Korea, where HABs pose
    a critical water quality issue. Three variations of recurrent neural network models, i.e., long short-term
    memory (LSTM), gated recurrent unit (GRU), and reverse time attention (RETAIN), were adopted for
    comparisons of performance with RETAIN-D. Input features encompassing meteorological, hydrological,
    environmental, and biological factors were used to forecast cyanobacteria abundance (total cyanobacteria
    cell counts and cell counts of dominant cyanobacteria taxa). Incorporation of a decay mechanism into the
    deep learning structure in RETAIN-D allowed forecasts of HABs on a high temporal resolution (daily)
    without manual feature engineering, increasing the usefulness of resulting forecasts for water quality and
    resources management. RETAIN-D yielded a high degree of accuracy (RMSE = 0.29 1.67, R2 = 0.76 0.98,
    MAE = 0.18 1.14, SMAPE = 9.77 87.94% for test sets; on natural log scales) across model outputs and sites,
    successfully capturing high variability and irregularities in the time series. RETAIN-D showed higher accuracy
    than RETAIN (except for comparable accuracy in forecasting Microcystis abundance at the Nakdong River site)
    and outperformed LSTM and GRU across all model outputs and sites. Ambient temperature had high
    importance in forecasting cyanobacteria abundance across all model outputs and sites, whereas the relative
    importance of other input features varied by the output and site. Increases in contributions with increasing
    irradiance, decreasing flow rates, and increasing residence time were more pronounced in summer than other
    seasons. Differences in the contributions of input features among different time steps (1 to 7 days prior to forecasting)
    were larger in the Yeongsan River site. RETAIN-D is applicable to a wide range of forecasting models that can
    benefit from improved temporal resolution, performance, and interpretability.


    Keyword : Reverse time attention mechanism, Decay mechanism, Recurrent neural network, Explainable artificial intelligence, Harmful algal bloom, Cyanobacteria

    Link  : https://doi.org/10.1016/j.watres.2022.118289

  • Effects of lubricant-fuel mixing on particle emissions in a single cylinder direct injection spark ignition engine

    Scientific Reports

     

    Authors : Hoseung Yi1, Jihwan Seo1, Young Soo Yu1, Yunsung Lim2, Sanguk Lee2, Jongtae Lee2, Hanho Song3 & Sungwook Park

    ISSN : 2045-2322


    Abstract
      Gasoline direct injection (GDI) engines emit less carbon dioxide (CO2) than port fuel injection
    (PFI) engines when fossil fuel conditions are the same. However, GDI engines emit more ultrafine
    particulate matter, which can have negative health effects, leading to particulate emission regulations.
    To satisfy these regulations, various studies have been done to reduce particulate matter, and several
    studies focused on lubricants. This study focuses on the influence of lubricant on the formation of
    particulate matter and its effect on particulate emissions in GDI engines. An instrumented, combustion
    and optical singe-cylinder GDI engine fueled by four different lubricant-gasoline blends was used with
    various injection conditions. Combustion experiments were used to determine combustion characteristics,
    and gaseous emissions indicated that the lubricant did not influence mixture homogeneity but had
    an impact on unburned fuels. Optical experiments showed that the lubricant did not influence spray
    but did influence wall film formation during the injection period, which is a major factor affecting
    particulate matter generation. Particulate emissions indicated that lubricant included in the wall film
    significantly affected PN emissions depending on injection conditions. Additionally, the wall film influenced
    by the lubricant affected the overall particle size and its distribution.


    Keyword : -

    Link  : https://www.nature.com/articles/s41598-021-03873-w

  • Analysis of combustion and exhaust characteristics according to changes in the propane content of LPG

    Energy

     

    Authors : Seungju Baek, Sanguk Lee, Myunghwan Shin, Jongtae Lee, Kihyung Lee

    ISSN : 0360-5442


    Abstract
      Owing to the regulation of CO2 reduction in global transportation system, the number of
    vehicles using LPG is increasing worldwide and their cleanliness is being highlighted. LPG
    increases the content of propane (C3) to improve startability during winters; accordingly,
    the contents of butane (C4) and C3 change continuously depending on the weather. In this
    study, the spray and combustion process in an engine equipped with the latest LPLI system
    was analyzed to understand the engine control strategies according to the C3 content, and
    the change in exhaust emission was also studied. Although the injection quantity of LPG
    with C3 content of 25% was lower than that of LPG with 5% C3 content at the same fuel
    pressure, the commercial ECU increased the injection duration to match the number of carbons
    required for combustion. In addition, the ignition timing was advanced owing to the high-octane
    number of C3 and the maximum combustion pressure was increased by up to 8.63% owing
    to the high lower heating value and advanced ignition timing. In addition, BSNOx increased
    by up to 47.61% owing to the increased maximum combustion pressure, and BSCO and BSCO2
    increased by 33.14% and 11.70%, respectively, due to excessive injection.


    Keyword : Liquefied petroleum gas (LPG), Propane content; Spray characteristics, Combustion pressure, Exhaust emissions, Fuel economy

    Link  : https://doi.org/10.1016/j.energy.2021.122297

  • A Review of Medical Waste Management Systems in the Republic of Korea for Hospital and Medical Waste Generated from the COVID-19 Pandemic

    Sustainability

     

    Authors : Cheol-Woo Yoon, Min-Jung Kim, Yoon-Su Park, Tae-Wan Jeon and Min-Yong Lee

    ISSN : ****-****


    Abstract
      With the increasing generation of medical waste worldwide, managing medical waste has become
    crucial, given its potential environmental and public health risks. Previously in the Republic of Korea,
    medical waste was often mixed with municipal waste and disposed of in residential landfills or unsuitable
    treatment facilities (e.g., improperly managed incinerators). Environmental regulators and waste producers
    have made extensive efforts in recent years to improve waste management at healthcare facilities.
    This study presents an overview of the status of medical waste management in Korea and discusses
    information on the generation, composition, separation, transportation, and treatment of medical waste.
    Incineration was confirmed to be the most preferred treatment method for medical waste and was the
    only one used until late 2005. Large-scale medical waste incinerators are used for treating medical
    waste from most medical facilities in Korea; however, with increasing regulations on toxic air emissions
    (e.g., dioxins and furans), air emission standards are being tightened for all existing small-scale incineration
    facilities without air pollution control. Since medical waste usually contains various plastic materials such
    as polyvinyl chloride, these incinerators are highly likely to emit toxic air pollutants if improperly operated
    and managed. Waste minimization and recycling, control of toxic air emissions from medical waste incinerators,
    and alternative treatment methods to incineration are seen as major challenges. Incineration capacity cannot
    be expanded as quickly as the rising quantities of medical waste in Korea; thus, there is a growing need to
    reconsider the overall management system. Accordingly, we examined various medical waste treatment policies
    and methods that are being implemented in other countries, in addition to the main strategy of waste management.
    To determine preferable directions for the improvement of the medical waste management system, we investigated
    and compared the status of domestic and foreign waste management and proposed directions for improvement,
    focusing on several issues related to the current medical waste management system in Korea.


    Keyword : medical waste, Republic of Korea, effective management, hospital/medical waste, COVID-19 pandemic

    Link  : https://doi.org/10.3390/su14063678

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