Authors : C. D. Jo1, C. G. Lee1 & H. G. Kwon
 
Author Affiliations
Nakdong River Environment Research Center, National Institute of Environmental Research, Dalseong-Gun, Daegu, 43008, Republic of Korea
 
Issue Date : 05 February 2022
 
ISSN : 1735-1472
 
Issued By : Springer Link
 
Keyword : Cluster analysis; Factor analysis; Organic pollutant indicators; Principal component analysis; Water quality management
 
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

Authors : Seohui Park, Jungho Im, Jhoon Kim, Sang-Min Kim
 
Author Affiliations
1. Department of Urban & Environmental Engineering, Ulsan National Institute of Science and Technology, Ulsan, Republic of Korea
2. Department of Atmospheric Sciences, Yonsei University, Seoul, 03722, Republic of Korea
3. Environmental Satellite Centre, Climate and Air Quality Research Department, National Institute of Environmental Research, Incheon, 22689, Republic of Korea
 
Issue Date : 01 August 2022
 
ISSN : 0269-7491
 
Issued By : ELSEVIER
 
Keyword : Particulate matter; AOD, Satellite; Machine learning; Real-time learning
 
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.

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
 
Author Affiliations
1. Yeongsan River Environment Research Center, National Institute of Environmental Research, Gwangju, 61011, Republic of Korea
2. Environmental Measurement & Analysis Center, National Institute of Environmental Research, Incheon, 22689, Republic of Korea
3. National Institute of Environmental Research, Incheon, 22689, Republic of Korea
 
Issue Date : 01 August 2022
 
ISSN : 0269-7491
 
Issued By : ELSEVIER
 
Keyword : Lake sediment; Cage fish farming; Internal disturbance; Sediment core; Phosphorus; Cadmium
 
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..

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
 
Author Affiliations
1. Department of Environment and Energy Engineering, Chonnan National University, 77 Yongbongro, Gwangju 61186, South Korea
2. Department of Environment and Energy Engineering, Chonnam National University, Gwangju, 34134, South Korea
3. Department of Chemical Engineering and Materials Science, Ewha Womans University, Seoul, Seoul, 03760, South Korea
4. Department of Environmental and Safety Engineering, Ajou University, Gyeung-gi, 16499, South Korea
5. Department of Air Quality Research, National Institute of Environmental Research of Korea, Incheon, 22689, South Korea
 
Issue Date : 01 August 2022
 
ISSN : 0269-7491
 
Issued By : ELSEVIER
 
Keyword : Nitrosamines; Nitramines; Atmospheric reaction; Liquid water conten; Free ammonia; Seoul, Seosan
 
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.

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