Lake Shihwa Research Articles

Changes in sedimentary environments in Shihwa Lake, Korea

Shihwa Lake was an artificial freshwater lake formed in 1994 by constructing a 12.7-km-long seawall, but it became a seawater lake in 1997. The water quality of Shihwa Lake had not been recovered despite the seawater exchange through the drain gate. This may adversely affect not only the water but also the bottom sediment environment of the lake. To determine the possible reasons for the environmental deterioration, water and core samples from three points in the lake were collected. And the parameters, such as the water temperature, salinity, dissolved oxygen (DO), particle distribution, total carbon (TC) and total nitrogen (TN), C/N ratio, and radioactive strength, were measured to estimate the water and sediment quality. In addition, we investigated changes in the sedimentation environment based on heavy-metal analysis, stable-isotope analysis of the core sample, and numerical analysis of sand transport. The core-sample analysis revealed a change in the sedimentation process on a time basis (before, during, and after the construction of the seawall). As a result, the sedimentation rate was approximately 4 cm/year during the seawall construction and 2 cm/year after the construction near the center of the lake. Furthermore, we established that the trends in these calculated sedimentation rates, determined using the radioactive strength method, align consistently with the results obtained from simulations and ultrasonic-wave observations. Finally, we evaluated the effects of a tidal power plant on the exchange of seawater and sedimentation processes.

Benthic Respiration and Heavy Metal Benthic Fluxes in Artificial Shihwa Lake: Approaching In Situ Measurement

This study assessed the impact of intensive human activities on organic matter (OM) and heavy metal cycles in Shihwa Lake, South Korea. Sediment oxygen demand (SOD), benthic nutrient flux (BNF), and benthic heavy metal flux were estimated using in situ benthic chambers. The combined analysis of sediment trap and SOD showed that the vertical supply of OM was a major controlling factor for benthic respiration. The BNF accounted for 35–144% and 32–184% of the N and P required, respectively, for primary production (PP) in the water column. The higher SOD may have also accelerated the release of Mn, Fe, Co, and Ni from the sediment. Benthic fluxes of Cr, As, Cd, Pb, Cu, and Zn were highest near the industrial complex, with ranges of 1.3 ± 0.9, 6.4 ± 4.9, 0.2 ± 0.1, 0.5 ± 0.4, 7.7 ± 1.4, and 452 ± 133 μmol m−2 d−1, respectively. Mn, Fe, Co, As, Pb, Ni, and Cu contributed more than 10% of the sediment to the current standing stock at Shihwa Lake.

Characterization of Lacinutrix neustonica sp. nov., Isolated from the Sea Surface Microlayer of Brackish Lake Shihwa, South Korea

A Gram-negative, strictly aerobic, non-motile, slightly curved rod-shaped bacterial strain, designated as HL-RS19T, was isolated from a sea surface microlayer (SML) sample of the brackish Lake Shihwa. Here, we characterized the new strain HL-RS19T using a polyphasic approach to determine its taxonomic position. A phylogenetic analysis of its 16S rRNA gene sequence revealed that strain HL-RS19T belonged to the genus Lacinutrix and was closely related to L. mariniflava AKS432T (97.9%), L. algicola AKS293T (97.8%), and other Lacinutrix species (<97.3%). The complete genome sequence of strain HL-RS19T comprised a circular chromosome of 3.9 Mbp with a DNA G+C content of 35.2%. Genomic comparisons based on the average nucleotide identity and digital DNA-DNA hybridization showed that strain HL-RS19T was consistently discriminated from its closely related taxa in the genus Lacinutrix. Strain HL-RS19T showed optimal growth at 20–25 °C, pH 6.5–7.0, and 3.0–3.5% (w/v) sea salts. The major fatty acids (>5%) of strain HL-RS19T were identified as iso-C15:1 G (16.5%), iso-C16:0 3-OH (12.9%), anteiso-C15:1 A (9.9%), anteiso-C15:0 (9.7%), iso-C15:0 (9.0%), and iso-C15:0 3-OH (8.3%). The polar lipids consisted of phosphatidylethanolamine, three unidentified aminolipids, an unidentified phospholipid, and two unidentified lipids. The major respiratory quinone was MK-6. Based on phylogenetic, genomic, phenotypic, and chemotaxonomic data, strain HL-RS19T represents a novel species belonging to the genus Lacinutrix, for which the name Lacinutrix neustonica sp. nov. is proposed. The type strain is HL-RS19T (=KCCM 90497T = JCM 35710T). The genome sequence analysis of strain HL-RS19T suggests that it may be well adapted to a harsh SML environment and is likely involved in arsenic cycling, potentially contributing to the bioremediation of anthropogenic arsenic pollution.

SWAT을 이용한 유역 내 토지 피복 변화에 따른 시화호 유입 퇴적물 양 모의

SWAT을 이용한 유역 내 토지 피복 변화에 따른 시화호 유입 퇴적물 양 모의

납 동위원소 연대측정을 이용한 시화호 내측 우음도의 퇴적환경 복원

납 동위원소 연대측정을 이용한 시화호 내측 우음도의 퇴적환경 복원

10 years long-term assessment on characterizing spatiotemporal trend and source apportionment of metal(loid)s in terrestrial soils along the west coast of South Korea

Long-term trends in the spatial distributions and sources of metal(loid)s in soils adjacent to the west coastal areas of South Korea have been systematically investigated for 10 years (2010–2019). Monitoring in 17 sites clearly showed site- and region-specific distributions, being associated with land use type (significant differences, as road > agriculture > wild) (P < 0.05), rather than temporal variation. The great concentrations of all metal(loid)s were found near Lake Shihwa (LS) and Geum River (GG), near the road, indicating that transportation activity was the main source of metal(loid)s contamination in soil. Especially, Cd (0.5 mg kg−1), Hg (0.04 mg kg−1), Pb (65 mg kg−1), and Zn (184 mg kg−1), related to the transportation activity near the road, showed twice greater than other land use types, on average. The concentration of metal(loid)s in each site and with the same land use type did not greatly vary over the years, with no significant annual difference (P > 0.05). The degree of metal(loid)s contamination compared to the background levels was identified in the order of Pb > Zn > Cr > Cu > As>Cd > Ni > Hg, with the contaminated hotspots mostly in LS or GG. The potential ecological risk was evidenced for Cd and Hg, but such a trend was temporally irregular over the years, indicating site-specificity. The sources of metal(loid)s were carefully determined as natural (20%), fuel combustion & agricultural pollution (43%), and vehicular emissions (37%) using the Positive Matrix Factorization model. The relative contribution of each source to contamination over the last decade was found to be similar, supporting that site-dependent lesser variation in metal(loid)s contamination in the coastal areas of South Korea. Overall, the distribution of metal(loid)s in the soil near the west coastal areas over the last decade largely depended on land use activities, and contamination degree was associated with non-point sources, such as transportation and fuel combustion.

The rebirth and eco-friendly energy production of an artificial lake: A case study on the tidal power in South Korea

In light of climate change and greenhouse gas reduction, countries around the world are doing their part to develop various types of eco-friendly energy. In this context, the Shihwa Tidal Power Plant is an advanced energy generation infrastructure which uses the resources of the sea, a project that pioneers and practices low-carbon, green growth engineering. Not only as an advanced energy generation infrastructure but also it is an eco-friendly infrastructure that resurrected ‘the dead lake’, which had suffered extreme water pollution due to cutoff in seawater circulation after the completion of the tide embankment in 1994. By circulating the water of the lake, new mud flats have appeared in the upstream area, an area once submerged due to the embankment. These new mud flats are providing new shelters for various organisms, thus transforming the lake into an eco-friendly, life-giving one. Most tidal power plants are difficult to construction due to geological features. The Sihwa tidal power plant was developed harmoniously by utilizing the unique geological features and tidal power plant principles on the West coast of the Korean peninsula. Shihwa Tidal Power Plant is a special and differentiated development example of renewable energy production and environmental improvement along with the significant water quality improvement effect of Shihwa Lake due to increased seawater exchange rates. This article therefore presents the review of Shihwa Lake’s environmental issues and eco-friendly energy production process with the aim to identify the good practices, the challenges as well as the lessons learnt from their experience. This development will be another case of a country seeking to develop new marine energy. This is also a good practice of improving the environment of freshwater lakes in coastal areas.

Severe contamination and time trends of legacy and novel halogenated flame retardants in multiple environmental media from Lake Shihwa, Korea: Effectiveness of regulatory action

Novel halogenated flame retardants (HFRs) were introduced to industrial markets as alternatives to legacy brominated FRs (BFRs), such as polybrominated diphenyl ethers (PBDEs). In the present study, PBDEs and their brominated and chlorinated alternatives, novel BFRs (NBFRs) and dechlorane plus (DP), were measured in multiple environmental matrices in a highly industrialized lake in Korea. Legacy and novel HFRs were detected in multiple samples, indicating ubiquitous contamination. Concentrations of HFRs in water and sediment observed in creeks running through machine, textiles, and automobile industrial complexes were significantly higher than those observed in inside and outside of the lake. Higher bioaccumulation levels of HFRs were observed in inshore compared with offshore waters. Results suggest that multi-matrix distribution of legacy and novel HFRs was dependent on the geographical proximity to industrial sources. Compared with previous studies, the highest levels of PBDEs and NBFRs were recorded in water samples on a global scale, implying on-going emissions from industrial activities. Decabromodiphenyl ethane (DBDPE) was a dominant compound in water samples, whereas the concentrations of PBDEs, NBFRs, and DP in sediment were similar to each other. This suggests a shift in consumption from legacy to novel HFRs, preferentially in water environments. A significant declining trend in PBDEs was observed in water and sediment collected between 2008 and 2015, indicating the effectiveness of regulatory actions. Based on their environmental occurrence and bioaccumulation potential, pentabromoethylbenzene and bis(2-ethylhexyl) tetrabromophthalate may pose emerging concerns regarding contamination of aquatic environments.

Quantitative analysis of polyethylene terephthalate and polycarbonate microplastics in sediment collected from South Korea, Japan and the USA

Microplastics (MPs) have emerged as contaminants of public health and environmental concern. Although studies have reported the occurrence of MPs in sediment, quantitative determination of polyethylene terephthalate (PET) and polycarbonate (PC) concentrations is limited. In this study, marine coastal and freshwater sediment collected from various locations in South Korea, Japan and the United States were analyzed for PET and PC MPs using a depolymerization method of sample preparation followed by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) detection. PET MPs were found in surface sediments from South Korea (n = 20), Japan (n = 4) and the United States (n = 43) at concentrations (dry weight) in the ranges of <MQL-13,000,000 ng/g (median: 6600 ng/g), 3600–5400 ng/g (4400 ng/g) and <MQL-10,000 ng/g (<MQL), respectively. Similarly, PC MPs were found in the concentration ranges of <MQL-140,000 ng/g (median: 290 ng/g, South Korea), 150–510 ng/g (100 ng/g, Japan) and <MQL-110,000 ng/g (160 ng/g, the United States). Spatial analysis of concentrations of PET and PC MPs in sediment from Lake Shihwa watershed in South Korea showed a decreasing trend with increasing distance from inland point source areas (Ansan industrial area). No distinct vertical profiles were recorded for PET or PC MPs in sediment cores collected from Tokyo Bay (Japan) or inland lakes in Michigan (the United States). The measured concentrations of MPs in sediment provide baseline data to evaluate future trends and for ecological risk assessment.

Assessment of Organic Matter Sources in the Singil Stream Flowing into Lake Shihwa, South Korea

The Singil Stream, flowing into an artificial lake, Lake Shihwa (South Korea), experiences a strong anthropogenic pressure with continuous organic matter (OM) inputs from rural, urban, and industrial areas. In this study, we investigated suspended particulate matter (SPM) and streambed sediments collected along the Singil Stream in 2014 and 2016, by applying a dual element approach (δ13C and δ15N) to identify OM sources. The SPM and streambed sediment samples from the indusrial area showed higher organic carbon and nitrogen concentrations (or contents) than those from the other areas, with distinctively lower δ15N values. Accordingly, our dual element approach indicates that the industrial area was the predominant OM source influencing OM quality and thus water quality of the Singil Stream flowing into Lake Shihwa during the study periods. However, further studies are necessary to better constrain OM sources in the Singil Stream since OM sources from the industrial area appear to be complex.

Investigations of Pb and Cu Isotopes to Trace Contamination Sources from the Artificial Shihwa Lake in Korea

Jeong, H.; Choi, J.Y.; Lee, J., and Ra, K., 2020. Investigations of Pb and Cu isotopes to trace contamination sources from the artificial Shihwa Lake in Korea. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 1122-1127. Coconut Creek (Florida), ISSN 0749-0208.The concentrations of heavy metals and Pb and Cu isotopes in sediments from five streams (A–G) around the Shihwa National Industrial Complex in Korea were investigated with the aim of identifying sources of metal pollution. The average concentration of Zn (21,106 mg/kg) was the highest, followed by Cu (2,804 mg/kg), Ni (2,126 mg/kg), Pb (897 mg/kg), Cr (807 mg/kg), As (18 mg/kg), Cd (8.0 mg/kg), and Hg (1.4 mg/kg). The concentrations tended to be highest in sediments from stream G. The 206Pb/207Pb and 208Pb/206Pb ratios of stream sediments ranged from 1.1302 to 1.1626 and 2.0983 to 2.1990, respectively. The Pb isotopes in stream sediments showed linear trends both Chinese Pb ore and Korean Pb–Zn Ore deposit. The Pb isotopic composition overlapped with Shihwa road dust values. The δ65CuAE647 values of stream sediments ranged from –0.16‰ to 0.64‰, clustering in two groups, one relatively enriched in the light Cu isotope (0.08‰–0.13‰) and another enriched in the heavy Cu isotope (0.37‰–0.48‰). Our results indicate that streams F and G are relatively enriched in heavy Cu isotopes. 208Pb/206Pb vs. δ65CuAE647 plots indicate that the two branches of the Shingil stream (E and F) are noticeably distinguished, with their isotopic compositions suggesting different pollution sources. The Cu and Pb isotopic compositions reflect those of road dust, and suggest that the stream sediments were affected by road dust transported in stormwater runoff. Thus, road dust may be a potential source of metal pollution in the stream sediments of industrial regions in Korea.

Spatiotemporal Distribution of Dissolved Heavy Metals in Gyeonggi Bay, Korea

In this study, we investigated the spatial and temporal distribution of heavy metals and nutrients in Gyeonggi Bay, Korea, to determine their present status and seasonal variability, and to identify their sources. Two surveys (May and August 2017) covering the entire Gyeonggi Bay (15 sites) and twelve surveys over four seasons (February, May, August, and November of 2016–2018) covering the Incheon Special Management Area (7 sites) were carried out to collect surface seawaters. Three surveys (January, April, and August of 2015) were also performed to collect seawater samples at Shihwa Lake (16 sites). Although the concentration gradients of nutrient type heavy metals (e.g. copper, nickel, zinc, and cadmium) corresponded to patterns of salinity in both dry and wet seasons, there was little seasonal variability over the three years studied. However, there was evidence that heavy metals were released during mixing with freshwaters in the wet season, likely from river outflow or direct coastal inputs such as effluents from Shihwa Lake. For nutrients, whereas the conservative mixing of dissolved inorganic nitrogen and the release of dissolved inorganic phosphate and dissolved silica were observed in the wet season, the concentrations of organic particles (e.g., chlorophyll-a, particulate organic carbon, and particulate organic nitrogen) had an inverse relationship with salinity in the dry season (May). Scavenged metals (e.g., manganese and cobalt) had non-freshwater coastal sources, such as benthic remobilization from suboxic sediments, and exhibited seasonal variation; they progressively increased in concentration from winter to spring and summer, and dropped to their minimum levels in the fall, which was presumably related to variation in microbial activity in sediments. Based on their relationship with salinity, heavy metals were deduced to be derived from coastal sources such as effluents from Shihwa Lake and freshwater from the Han River.

Spatial and temporal trends of melamine and its derivatives in sediment from Lake Shihwa, South Korea.

Occurrence, spatial distribution, and temporal trends of melamine and its derivatives (ammeline, ammelide, and cyanuric acid) were investigated in surface sediment and two sediment cores collected from Lake Shihwa, South Korea. ∑Melamine (sum of melamine and its three derivatives) was found in all surface sediment samples at concentrations that ranged from 16.6 to 4390 ng/g dry weight (dw), with an average value of 202 ng/g dw. ∑Melamine concentrations exhibited a clear spatial gradient, in decreasing order, as: creeks (mean: 577 ng/g dw) > inshore locations (41.9 ng/g dw) > offshore locations (24.3 ng/g dw). ∑Melamine concentrations were notably high in sediment collected near wastewater treatment plant (WWTP) outfalls. Melamine was the most prevalent compound in sediment collected from creeks (87%) and WWTP outfall locations (48%), whereas cyanuric acid was the dominant compound in sediment from inshore (51%) and offshore (63%) locations. The historical profiles of ∑Melamine in sediment cores corresponded with coastal development and environmental changes in this region. This is the first study to document the occurrence and temporal distribution of melamine in sediment cores, and this information is useful in understanding the fate of these relatively less-studied chemicals in the environment.

자성을 이용한 시화호 유역 산업단지 도로먼지 내 중금속 오염원 추적

본 연구에서는 시화호 유역 산업단지 도로먼지 내 중금속 오염원 추적과 공간분포 특성, 금속 오염도/위해성 평가를 위하여 도로먼지를 채취하였으며, 자성을 이용하여 중금속 분석을 실시하였다. 도로먼지 내 중금속의 평균농도는 Cr 498 mg/kg, Ni 164 mg/kg, Cu 992 mg/kg, Zn 1,824 mg/kg, As 19.4 mg/kg, Cd 2.22 mg/kg, Pb 612 mg/kg, Hg 0.08 mg/kg로 나타났다. Cr, Ni, Cu, Zn, Pb의 변동계수(CV)가 100%를 초과하고 있어 인위적인 오염원이 존재하고 있었다. 자성 부분(magnetic fraction)에서의 Cr, Ni, Cu, Zn, Cd, Pb, Hg의 평균농도가 비자성 부분(non-magnetic fraction)에 비해 2~35배 높았으며, 시화산업단지가 반월산업단지에 비해 높은 특징을 보였다. 농집지수를 이용한 오염도 평가 결과는 반월, 시화산업단지 도로먼지 내 Cr, Cu, Zn, Cd, Pb이 “심한 오염(heavily polluted)”에 해당되는 것으로 나타나, 차량기인 타이어, 브레이크, 엔진 등의 마모를 통한 공급이 있음을 알 수 있었다. Cu와 Zn는 차량기인 뿐만 아니라 금속물질의 제조와 사용 등 다양한 오염원의 영향을 크게 받는 것으로 판단된다. 도로먼지 내 중금속 농도는 전체 도로먼지(total fraction) 52%, 자성 부분 100%, 비자성 부분 52%가 심각하게 오염된 “매우 나쁨”에 해당되는 결과를 얻었다. 전체 도로먼지 중 자성 부분은 양으로는 14%를 차지하지만, 중금속의 양은 Cr 79%, Ni 78%, Cu 40%, Zn 45%, Cd 38%, Pb 29%, Hg 46%를 차지하고 있었다. 도로먼지에서 63 μm 이하가 차지하는 평균 비율은 28.6%로 나타났으며, 이는 시화호로 유입되는 하천을 오염시키는 주요 원인으로, 추가적인 오염원 방지 대책이 필요하다고 판단된다. 또한 도로먼지 청소시 자성을 이용한다면 도로먼지의 상당량을 제거할 수 있어 효율적으로 활용될 수 있을 것이다.

Distribution of Humic Fluorescent Dissolved Organic Matter in Lake Shihwa: the Role of the Redox Condition

Hypoxia has occurred worldwide in coastal and marginal oceans. The redox condition has recently garnered major interest as a favorable condition for delivering sedimentary organic matter to the water column. In this study, we measured the fluorescence of fluorescent dissolved organic matter (FDOM) in brackish Lake Shihwa, Korea, in which hypoxic conditions are typically observed during summer. Especially, fluorescent intensities of the humic FDOM (FDOMH) were relatively high during summer, with a relatively lower dissolved oxygen (DO) level, and exponentially increased with decreasing DO concentrations. The results indicated that the production of FDOMH is associated with anaerobic processes. It was further supported by a significantly positive relationship between FDOMH and ammonium. Based on the relatively low values of redox potential (up to 60.0 mV) and high concentration of phosphate with the low DO level, this enrichment of FDOMH seems to be linked to the input of anoxic porewater. Using a simple schematic diagram, the contribution of FDOMH from reducing environments is comparable to that from stream water, which is known to be a major source in coastal regions. This study highlights that the redox condition is a key factor contributing to the production of FDOMH in coastal marine environments.

Assessing environmental changes in Lake Shihwa, South Korea, based on distributions and stable carbon isotopic compositions of n-alkanes

We investigate historical environmental changes in an artificial lake, Lake Shihwa in South Korea, based on bulk (TOC, TN, C/N ratio, δ13CTOC, and δ15NTN) and molecular (concentrations and δ13C of n-alkanes) parameters, by analyzing riverbank sediments (n = 12), lake surface sediments (n = 9), and lake core sediments (n = 108). Although the bulk organic parameters showed similar characteristics for all lake surface sediment samples, the distribution pattern and δ13C of n-alkanes revealed distinct differences between 2009 samples and 2012/2016 samples. This change of sedimentary organic matter characteristics can be attributed to operation of the tidal power plant that began in 2011, which improved lake water circulation and thus changed the lake sedimentary environment from anoxic to more oxic conditions. The vertical profiles of bulk and molecular lake sediment core records collected in 2009, especially at the site closest to the dike, showed a drastic shift around 1987, indicating that stronger anoxic sedimentary conditions prevailed after 1987. This is linked to sea dike construction in 1987, which prohibited sea-lake water exchange and thus deteriorated water quality in Lake Shihwa. We conclude that Lake Shihwa has experienced severe environmental changes due to human activities.

Tracing the Pollution Source Using Pb Isotopes in Sediments of the Coastal Region Surrounding the National Industrial Complex, Korea

Jeong, H.; Ra, K.; Kim, K.-T.; Kim, E.-S.; Lee, S.-Y., and Choi, M.-S. 2018. Tracing the pollution source using Pb isotopes in sediments of the coastal region surrounding the national industrial complex, Korea. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 1456–1460. Coconut Creek (Florida), ISSN 0749-0208.166 sediment samples from Ulsan Bay and Shihwa Lake that is special management sea area were collected in 2014 not only to study the spatial distribution and pollution assessment of Pb but also to identify anthropogenic pollutions for Pb isotopes. The mean Pb concentrations of road-deposited sediments were higher than those of stream and coastal sediments in the study area. In all sediment samples, Ulsan showed an average concentration of 2 to 4 times higher than that of Shihwa. Pb concentrations in coastal sediments of more than 50 % were below the threshold effect level (TEL) of Korean marine sediment quality guidelines. The high exceedance of probable effect levels (PEL) showed in large harbors and near industrial facilities. Road-deposited sediments in Ulsan and Shihwa exceeded the class 2 (potentially toxic to benthic organisms) of Korean freshwater sediment quality guidelines. For both study areas, Pb isotope ratios tend to decrease with increasing Pb concentrations in sediments. In the case of Ulsan, high concentrations and low 206Pb/207Pb isotopic ratios were observed nearby the smelter and lead ore import harbor, indicating that Pb was released into the road surface during transportation using the vehicle and then moved to the marine area through the stream. However, Shihwa has a lot of small facilities (>19,000), it is difficult to clearly identify Pb pollution sources.

Polyp Removal of a Bloom Forming Jellyfish, Aurelia coerulea, in Korean Waters and Its Value Evaluation

Aurelia coerulea is a bloom forming jellyfish that first appeared before 1980 in the western and southern Korean seas and which has been blamed for huge economical losses in all fields of marine activities. As a preventive measure to reduce economical losses, polyp removal was undertaken at Lake Shihwa, Lake Saemangeum, and Masan Bay, Korea. In the course of efforts during 2 years to remove polyps, polyps were surveyed, quantified, and removed. In these areas, the initial total polyp abundance was 5.04 × 109 and 46.25% of them were removed; Lake Shihwa the highest rates of removal and Lake Saemangeum the lowest. These efforts to remove polyps prevented the appearance of 1.20 × 109 medusae, corresponding to 78.28 × 106 kg. The cost of polyp removal was evaluated and compared with that of medusae removal. The ratio between the cost of polyp removal and that of medusae removal ranged between 0.78–3.14%, indicating large cost savings for polyp removal undertakings. However, the effect of polyp removal varied from positive to none, and we assumed that the cleared surface for polyp removal, quantity of removed polyp, and existence of polyps’ hotspots in neighboring areas were the causes of the non-effectiveness of polyp removal undertakings.

Organophosphate flame retardants (OPFRs) in water and sediment: Occurrence, distribution, and hotspots of contamination of Lake Shihwa, Korea

Contamination by organophosphate flame retardants (OPFRs) is an emerging concern in aquatic environments. Concentrations of 18 OPFRs were measured in water and sediments collected from the artificial Lake Shihwa. OPFR concentrations in sediments measured in this study were the highest reported worldwide, implying severe OPFR contamination. The highest concentrations of OPFRs were found in creeks taken near industrial complexes, and OPFR concentrations decreased with increasing distance from creeks to inshore or offshore lake waters. On-going OPFR contamination by wastewater treatment plant (WWTP) discharge was evidenced by the clear decrease in OPFRs in water samples collected moving away from WWTP outfall. TBEP and TEP were dominant in water samples, while TDCPP and TCPP were dominant in sediment samples. Differences in contamination profiles with sample matrices are likely due to hydrophobicity of individual OPFRs. Non-parametric multidimensional scaling ordination showed that OPFR contamination was affected by pollution inflow and proximity to industrial complexes.

Regional Variation and Discharge Characteristics of Stream Water Quality and Heavy Metals Around the Shihwa Lake Basin

Regional Variation and Discharge Characteristics of Stream Water Quality and Heavy Metals Around the Shihwa Lake Basin