Assessment of trace pollutants in Korean coastal sediments using the triad approach: a review

Distributions of PCDD/Fs, PCBs, and PCNs in coastal sediments collected from major industrial bays in South Korea

Polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs), polychlorinated biphenyls (PCBs), and polychlorinated naphthalenes (PCNs) were assessed in coastal sediments from industrial bays in South Korea to evaluate the pollution levels and their environmental impact. The mean sediment concentrations of Σ17 PCDD/Fs, Σ18 PCBs, and Σ15 PCNs were 198 ± 140, 3427 ± 7037, and 85 ± 336 pg/g dw, respectively. Generally, pollutant concentrations in the inner bay were higher than those in the outer bay, indicating the influence of industrial emissions and harbor activities. The primary sources were identified as steel manufacturing and wastewater treatment plants for PCDD/Fs, harbor and shipbuilding activities for PCBs, and combustion-related sources for PCNs. Notably, PCDD/F concentrations exceeded sediment guideline values. The combined effects of PCDD/Fs and PCBs demonstrated adverse impacts on aquatic organisms. Hence, the release of toxic pollutants into the marine environment could have potential biological effects due to the combined impact of these various compounds.

Methodological advances and future directions of microalgal bioassays for evaluation of potential toxicity in environmental samples: A review

Microalgal bioassays are widely applied to evaluate the potential toxicity of various persistent toxic substances in environmental samples due to multiple advantages, including high sensitivity, short test duration, and cost-effectiveness. Microalgal bioassay is gradually developing in method, and the scope of application to environmental samples is also expanding. Here, we reviewed the published literature on microalgal bioassays for environmental assessments, focusing on types of samples, sample preparation methods, and endpoints, and highlighted key scientific advancements. Bibliographic analysis was performed with the keywords 'microalgae' and 'toxicity' or 'bioassay', and 'microalgal toxicity'; 89 research articles were selected and reviewed. Traditionally, most studies implementing microalgal bioassays focused on water samples (44%) with passive samplers (38%). Studies using the direct exposure method (41%) of injecting microalgae into sampled water mainly evaluated toxic effects by growth inhibition (63%). Recently, various automated sampling techniques, in situ bioanalytical methods with multiple endpoints, and targeted and non-targeted chemical analyses have been applied. More research is needed to identify causative toxicants affecting microalgae and to quantify the cause-effect relationships. This study provides the first comprehensive overview of recent advances in microalgal bioassays performed with environmental samples, suggesting future research directions based on current understanding and limitations.

Revisited a sediment quality triad approach in the Korean coastal waters: Past research, current status, and future directions

We present a comprehensive review of the sediment quality triad (SQT) assessment studies in Korea. The bibliographic analysis was applied to evaluate how approaches in sediment assessment have evolved. A meta-analysis was performed, to evaluate potential risks of sedimentary persistent toxic substances (PTSs) reported in Korean coastal waters. Within the framework, we identified and discussed current status and spatiotemporal trends in contamination of both classic and emerging PTSs over the recent decadal period. Out of 26 target regions in Korea, five hotspots (Sihwa, Masan, Ulsan, Taean, and Gwangyang) of concern could be identified. Four of those regions have been designated as Specially-Managed Sea Area under the implementation of Total Pollution Load Management System in Korea, except for Taean coast (oil spill site). Meantime, we could identify three stepwise research phases based on a bibliographic analysis; Phase 1 (1995-2008), Phase 2 (2009-2015), and Phase 3 (2016-2020). It is noteworthy that a technical evolution of the SQT assessment by the phase was featured. It was also evidenced that in-depth studies adopting multiple lines of evidence (LOEs) became prevailed upon approaching Phase 3. In a quantitative manner, the toxicity explanatory power of target PTSs increased by about 10% in Phase 3 compared to the earlier phases. The meta-analysis using ratio-to-mean value method applied for the data set having all three LOEs indicated general improvement of sediment qualities in the hotspots. However, their associations quite varied across regions and years, reflecting a dynamicity in oceanographic settings and/or heterogeneity in toxicological effect or benthic community response. At present, SQT assessment adopting the increased LOEs generally supports better assessment. In conclusion, we suggest that future SQT studies globally should reaffirm the utility of the "multiple LOEs approach", focusing on the identification and management of causative toxicants that driving negative ecological impacts on marine ecosystems.

Large-scale sediment toxicity assessment over the 15,000 km of coastline in the Yellow and Bohai seas, East Asia

The Yellow and Bohai seas have long been contaminated by persistent toxic substances (PTSs) from numerous (un)known anthropogenic sources. In this study, we used Vibrio fischeri bioassay to evaluate ecotoxicological profiles associated with sedimentary PTSs contamination at a large marine ecosystem (LME) scale. A total of 125 surface sediments collected from the coastal areas of the Yellow and Bohai seas were analyzed both for aqueous and organic extracts. Not surprisingly, the results indicated site-dependent toxicities, but most sites were identified as non-toxic to V. fischeri. For aqueous extracts and organic extracts, 13% and 8% of samples, respectively exhibited marginal toxicity, while 0% and 2% of samples exhibited moderate toxicity. However, it should be noted that organic extracts (mean TU = 56) induced stronger toxicities than aqueous samples (mean TU = 0.4). This result generally back-supported the high toxicity potentials associated with sedimentary sink of organic pollutants. Several PTSs measured in the samples indicated a significant contribution to the observed V. fischeri toxicities. Of note, polycyclic aromatic hydrocarbons (PAHs; r = 0.28, p < 0.05), styrene oligomers (r = 0.41, p < 0.01), and alkylphenols (r = 0.38, p < 0.05) showed significant associations to the observed bacterial inhibition. Among PAHs, benzo[a]anthracene and phenanthrene exhibited a significant contribution to the observed V. fischeri toxicities. Meantime, salinity which reflects the distance from the point sources of land-driven pollutants along the rivers and estuaries in the Yellow and Bohai seas was a key environmental variable representing the sample toxicities. Overall, the present study provides baseline information for evaluating the potential sediment toxicity to implement responsible coastal management at an LME scale, and elsewhere.

Spatial distribution and source identification of traditional and emerging persistent toxic substances in the offshore sediment of South Korea

While the coastal pollution of persistent toxic substances (PTSs) has been widely documented, information on offshore environments remains limited. Here, we investigated the spatial distribution and sources of PTSs in the offshore sediments (n = 34) of South Korea. Sediment samples collected from the Yellow Sea (n = 18), the South Sea (n = 10), and the East Sea (n = 6), in 2017-18 were analyzed for a total of 71 PTSs. Target compounds include 31 PCBs, 15 PAHs, 9 emerging PAHs (e-PAHs), 10 styrene oligomers (SOs), and 6 alkylphenols (APs). Sedimentary PCBs showed relatively low concentrations with no significant difference across the three seas (0.16-6.9 ng g^-1 normalized organic carbon, OC). Low-chlorinated PCBs (tri- and tetra Cl-CBs) were predominant (mean: 77%), primarily indicating atmospheric inputs. PAHs widely accumulated in the three seas with low to moderate level (22-250 ng g^-1 OC), and dominated by high molecular weight PAHs (4-6 rings). PMF analysis revealed coast-specific PAHs sources; i.e., originated from mainly coke production (77%) in the Yellow Sea, vehicle emissions (68%) in the South Sea, and fossil fuel combustion (49%) in the East Sea. SOs showed significant contamination than other PTSs, with elevated concentrations in the Yellow Sea (mean: 350 ng g^-1 OC). APs showed a similar regional distribution to SOs, but concentrations were much lower (mean: 17 ng g^-1 OC). SOs and APs seemed to be introduced from rivers and estuaries on the west coast of Korea, where industrial and municipal activities are concentrated, then might be transported to offshore through tide or currents. Overall, the novel data presented for various PTSs in offshore Korean sediments warrant the necessity of a long-term monitoring effort and urgent management practice to protect marine ecosystem.

Perfluoroalkyl acids in rapidly developing coastal areas of China and South Korea: Spatiotemporal variation and source apportionment

Polyfluoroalkyl substances (PFASs) are recognized as emerging contaminants that have captured worldwide attention. They are primarily transported in environments and spread around the globe due to their persistent and bioaccumulative characteristics. In this study, 15 PFASs were detected in major rivers of the rapidly developing coastal areas of China and South Korea. The concentrations and compositions of these PFASs varied greatly between different regions along the coastline. The total concentrations ranged from 14.9 to 16,500 ng L^-1, and the mean concentrations of Σ₁₅PFASs in Liaodong Bay, Bohai Bay, Laizhou Bay, and the west coast of South Korea were 124 ng L^-1, 81.4 ng L^-1, 1550 ng L^-1, and 36.2 ng L^-1, respectively. In Laizhou Bay, the relatively high perfluorooctanoic acid (PFOA) was due to the high usage and manufacturing of PFOA-containing products and contributed 59% of the total compounds. In Liaodong Bay and Bohai Bay, PFBA and PFOA were the most abundant compounds, accounting for >55% of the total compounds. Along the west coast of South Korea, PFBA and PFPeA were the most prevalent compounds, contributing 28% and 24% of the total compounds, respectively. The data collected in the last decade were analyzed to investigate the temporal trends of selected PFASs. The total concentration of Σ₁₀ PFASs decreased in both China and South Korea, while the proportion of short-chain PFASs increased. The proportion of C₄-C₇ PFCAs in South Korea rapidly increased from 46% to 79% but decreased from 49% to 43% in China. The positive matrix factorization (PMF) model successfully addressed the site-specific source apportionment, which showed that 53% of the PFASs in Laizhou Bay were due to fluorine manufacturing. The results of this study provide novel insights into elucidating the spatiotemporal distribution and complicated sources of PFASs over a large area and provide a clear message for all stakeholders, water and coastal managers, and scientists.

Current contamination status of traditional and emerging persistent toxic substances in the sediments of Ulsan Bay, South Korea

Contamination status of traditional and emerging persistent toxic substances (PTSs) in sediments and their major sources were investigated in Ulsan Bay, Korea. A total of 47 PTSs, including 15 traditional PAHs, ten styrene oligomers (SOs), six alkylphenols (APs), and 16 emerging PAHs (E-PAHs) were analyzed. Concentrations of traditional PAHs, SOs, and APs ranged from 35 to 1300 ng g^-1 dry weight (dw), 30 to 3800 ng g^-1 dw, and 30 to 430 ng g^-1 dw, respectively. For the last 20 years, PTSs contamination in the bay area has been improved. However, 12 E-PAHs were widely detected in sediments, with a maximum of 240 ng g^-1 dw (for benzo[e]pyrene) at the creek site. These E-PAHs seemed to originate from surrounding activities, such as biomass combustion, mobile sources, and diesel combustion. Due to environmental concerns for E-PAHs, further research on the potential toxicity, distribution, and behavior of these compounds should be implemented.

Characteristics of long-term changes in microbial communities from contaminated sediments along the west coast of South Korea: Ecological assessment with eDNA and physicochemical analyses

The environmental DNA (eDNA) metabarcoding was applied to assess benthic ecological health in the west coast of South Korea by investigating a long-term microbial community change (2015-17). The ecological interaction among microorganisms, from phylum to family level, and their associations to environmental variables across the five regions were highlighted. As part of the study, the available chemistry and toxicological data in the regions during the monitoring periods were incorporated into an integrated sediment triad assessment. The bacterial communities were dominated by Proteobacteria (34.2%), Bacteroidetes (13.8%), and Firmicutes (10.8%). Proteobacteria and Bacteroidetes dominated consistently across regions and years, while Firmicutes and Cyanobacteria significantly varied by region and years (p < 0.05). The abundance of this phylum declined over time with the increasing abundance of Cyanobacteria, indicating their independent interactions to certain environmental changes. Planctomycetes and Gemmatimonadetes linked to some contaminants (ΣPAHs and Cu), implying indicator taxa. Overall, eDNA-based microbial community analysis combined with exposures of contaminants and responses of microorganisms is a promising strategy for the assessment of benthic ecological health in contaminated sediments from coastal waters.

Legacy and Current-Use Contaminants in Sediments Alter Macroinvertebrate Communities in Southeastern US Streams

Sediment contamination of freshwater streams in urban areas is a recognized and growing concern. As a part of a comprehensive regional stream-quality assessment, stream-bed sediment was sampled from streams spanning a gradient of urban intensity in the Piedmont ecoregion of the southeastern United States. We evaluated relations between a broad suite of sediment contaminants (metals, current-use pesticides, organochlorine pesticides, polychlorinated biphenyls, brominated diphenyl ethers, and polycyclic aromatic hydrocarbons), ambient sediment toxicity, and macroinvertebrate communities from 76 sites. Sediment toxicity was evaluated by conducting whole-sediment laboratory toxicity testing with the amphipod Hyalella azteca (for 28 d) and the midge Chironomus dilutus (for 10 d). Approximately one-third of the sediment samples were identified as toxic for at least one test species endpoint, although concentrations of contaminants infrequently exceeded toxicity benchmarks. Ratios of contaminant concentrations relative to their benchmarks, both individually and as summed benchmark quotients, were explored on a carbon-normalized and a dry-weight basis. Invertebrate taxa measures from ecological surveys tended to decline with increasing urbanization and with sediment contamination. Toxicity test endpoints were more strongly related to sediment contamination than invertebrate community measures were. Sediment chemistry and sediment toxicity provided moderate and weak, respectively, explanatory power for the similarity/dissimilarity of invertebrate communities. The results indicate that current single-chemical sediment benchmarks may underestimate the effects from mixtures of sediment contaminants experienced by lotic invertebrates. Environ Toxicol Chem 2020;39:1219-1232. Published 2020. This article is a U.S. Government work and is in the public domain in the USA.

Integrated assessment of west coast of South Korea by use of benthic bacterial community structure as determined by eDNA, concentrations of contaminants, and in vitro bioassays

During the past few decades, contamination of sediments by persistent toxic substances (PTSs) has been observed in estuarine and coastal areas on the west coast of South Korea. The contaminants are suspected to cause toxicities in aquatic biota, but little is known about their ecological effects, particularly on benthic microbial communities. In this study, an eDNA-based assessment was applied along with classic assessments of exposure, such as chemistry and in vitro bioassays, to evaluate condition of benthic bacterial communities subjected to PTSs. Two strategies were adopted for the study. One was to conduct a comprehensive assessment in space (by comparing seawater and freshwater sites at five coastal regions) and in time (by following change over a 5-y period). Although we found that bacterial composition varied among and within years, some phyla, such as Proteobacteria (28.7%), Actinobacteria (13.1%), Firmicutes (12.7%), and Chloroflexi (12.5%) were consistently dominated across the study regions. Certain bacterial groups, such as Firmicutes and Verrucomicrobia have been linked to contamination at some sites in the study area and at specific points in time. Bacterial communities were not significantly correlated with salinity or AhR- and ER-mediated potencies, whereas concentrations of PAHs, APs, and certain metals (Cd and Hg) exhibited significant associations to the structure of bacterial communities at the phylum level. In fact, the relative abundance of microbes in the phylum Planctomycetes was significantly and negatively correlated with concentrations of PAHs and metals. Thus, the relative abundance of Planctomycetes could be used as an indicator of sedimentary contamination by PAHs and/or metals. Based on our correlation analyses, Cd and ER-mediated potencies were associated more with bacterial abundances at the class taxonomic level than were other PTSs and metals. Overall, the eDNA-based assessment was useful by augmenting more traditional measures of exposure and responses in a sediment triad approach and has potential as a more rapid screening tool.

Long-term trends of persistent toxic substances and potential toxicities in sediments along the west coast of South Korea

For decades, in response to industrialization and urbanization, environmental qualities of estuarine and coastal areas of the west coast of Korea have been deteriorating. Long-term changes in concentrations of persistent toxic substances (PTSs) in sediments, including PAHs, styrene oligomers, nonylphenols, and metals and their potential toxicities via AhR- and ER-mediated potencies, and bioluminescent bacterial inhibition, were investigated. Long-term monitoring in five estuarine and coastal areas (2010-2018; 10 sites) showed that concentrations of PAHs and nonylphenols in sediments have declined while concentrations of some metals, Cd, Cr, and Hg have increased. Similarly, AhR-mediated potencies in sediments have declined, but inhibitions of bioluminescent bacteria have increased. Concentrations of sedimentary PAHs and AhR-mediated potencies were significantly (p < 0.01) and positively correlated. Sources of PAHs from combustion have been gradually declining while inputs from vehicle exhaust by-products have been increasing. Overall, this study brought our attention a balanced regulation in chemical-specific manner.

Meiobenthic nematodes in the assessment of the relative impact of human activities on coastal marine ecosystem

Ecological quality (EcoQ) status of the Southwest and West coasts of South Korea was evaluated within the "National Investigation of Marine Ecosystems in Korea" in the 2015. In particular, the study dealt to assess the ecological quality of the sediments using free-living nematode communities. A total of 149 species were found in the study area, and Daptonema, Sabatieria, Parodontophora, Sphaerolaimus, and Viscosia were found as dominant genera. Statistical analysis of both environmental and faunal parameters showed an increasing human pressure from Western to Southern coasts. The community structure changed with the environmental features of the study area and allowed the detection of a suite of possible nematode indicators that might be used in monitoring studies. In particular, Dorylaimopsis spp. appeared heavy metal and organic matter resistant taxa, Sabatieria an eutrophication resistant genus, while Paracanthonchus and Neotonchus as heavy metal and organic matter sensitive genera. The principal component analysis (PCA) results showed a clear negative correlation between maturity index and both heavy metal and organic matter increasing, while diversity indices did not appear to be significantly influenced by them. Appling the thresholds of the synthetic nematode indices, the EcoQ of the study area was assessed as poor to moderate.

Major AhR-active chemicals in sediments of Lake Sihwa, South Korea: Application of effect-directed analysis combined with full-scan screening analysis

This study utilized effect-directed analysis (EDA) combined with full-scan screening analysis (FSA) to identify aryl hydrocarbon receptor (AhR)-active compounds in sediments of inland creeks flowing into Lake Sihwa, South Korea. The specific objectives were to (i) investigate the major AhR-active fractions of organic extracts of sediments by using H4IIE-luc in vitro bioassay (4 h and 72 h exposures), (ii) quantify known AhR agonists, such as polycyclic aromatic hydrocarbons (PAHs) and styrene oligomers (SOs), (iii) identify unknown AhR agonists by use of gas chromatography-quadrupole time-of-flight mass spectrometry (GC-QTOFMS), and (iv) determine contributions of AhR agonists to total potencies measured by use of the bioassay. FSA was conducted on fractions F2.6 and F2.7 (aromatics with log K_ow 5-7) in extracts of sediment from Siheung Creek (industrial area). Those fractions exhibited significant AhR-mediated potency as well as relatively great concentrations of PAHs and SOs. FSA detected 461 and 449 compounds in F2.6 and F2.7, respectively. Of these, five tentative candidates of AhR agonist were selected based on NIST library matching, aromatic structures and numbers of rings, and available standards. Benz[b]anthracene, 11H-benzo[a]fluorene, and 4,5-methanochrysene exhibited significant AhR-mediated potency in the H4IIE-luc bioassay, and relative potencies of these compounds were determined. Potency balance analysis demonstrated that these three newly identified AhR agonists explained 1.1% to 67% of total induced AhR-mediated potencies of samples, which were particularly great for industrial sediments. Follow-up studies on sources and ecotoxicological effects of these compounds in coastal environments would be required.

Newly Identified AhR-Active Compounds in the Sediments of an Industrial Area Using Effect-Directed Analysis

Effect-directed analysis was used to identify previously unidentified aryl hydrocarbon receptor (AhR) agonists in sediments collected from a highly industrialized area of Ulsan Bay, Korea. The specific objectives were to (i) investigate potent fractions of sediment extracts using the H4IIE-luc bioassay, (ii) determine the concentrations of known AhR agonists (polycyclic aromatic hydrocarbons (PAHs) and styrene oligomers (SOs)), (iii) identify previously unreported AhR agonists in fractions by use of GC-QTOFMS, and (iv) evaluate contributions of individual compounds to overall AhR-mediated potencies, found primarily in fractions containing aromatics with log K_ow 5-8. Greater concentrations of PAHs and SOs were also found in those fractions. On the basis of GC-QTOFMS and GC-MSD analyses, 16 candidates for AhR agonists were identified in extracts of sediments. Of these, seven compounds, including 1-methylchrysene, benzo[j]fluoranthene, 3-methylchrysene, 5-methylbenz[a]anthracene, 11H-benzo[b]fluorene, benzo[b]naphtho[2,3-d]furan, and benzo[b]naphtho[2,1-d]thiophene, exhibited significant AhR activity. Relative potency values of newly identified AhR agonists were found to be greater than or comparable to that of benzo[a]pyrene (BaP). The potency balance analysis showed that newly identified AhR agonists explained 0.07-16% of bioassay-derived BaP-EQs. These chemicals were widely distributed in industrial sediments; thus, it is of immediate importance to conduct studies on sources and potential effects of those chemicals.

Carbon and nitrogen stable isotope signatures linked to anthropogenic toxic substances pollution in a highly industrialized area of South Korea

Sources of organic matter in a polluted coastal embayment (Lake Sihwa) indicated that δ¹³C and δ¹⁵N of suspended particulate matter (SPM) and sediments could be distinguished by land-use type and surrounding activities. Specifically, low δ¹⁵N occurred in inland creeks near industrial complex, where severe contamination by persistent toxic substances (PTSs) is evidenced. To identify the sources of ¹⁵N-depleted organic matter and PTSs, the SPM and/or sediments were collected along ~8 km of the Singil Creek and in stormwater drainage pipes that carried pollutants to the creeks from upland areas. Results indicated that stormwater originating in industrial areas was the main source of low δ¹⁵N and elevated PTSs, which appeared to flow into stormwater drains with rainwater and eventually into the creeks at stormwater outfalls. To improve the water quality of inland creeks, it will be necessary to reduce the amount of untreated stormwater entering stormwater drainage system from industrial complex.

Chemical-, site-, and taxa-dependent benthic community health in coastal areas of the Bohai Sea and northern Yellow Sea: A sediment quality triad approach

To investigate benthic ecological quality associated with coastal pollution in the Bohai Sea and northern Yellow Sea, a sediment quality triad (SQT) approach was applied. Chemical (six groups of persistent toxic substances (PTSs) and 8 metals and metalloids), toxicological (AhR-mediated potency), and ecological (bacterial and meiofaunal communities) elements were selected and used in an integrated sediment assessment. The benthic meiofaunal community was newly analyzed and used as an additional component of the infaunal community during the SQT. Concentrations of chemicals and potential toxicity in sediments both indicated moderate to severe pollution in the study area, characterized by site-specific and land-uses. In particular, As, DDTs, and bioassay-derived dioxin equivalents exceeded corresponding sediment quality guidelines at nearly all locations. Limited occurrences of meiofaunal taxa (mean = 5.2) and relatively low species diversity, mainly comprised of nematodes (75.3%) and copepods (14.6%), among locations was generally consistent with pollution. The benthic community was consistent with compound-specific responses to gradients of contamination, particularly for As. Densities of two taxa, Nematoda and Nemertea exhibited strong negative correlations with concentrations of As. Compound-, site-, and taxa-specific variability of pollution of sediments was further supported by results of cluster analysis (CA) and nonmetric multidimensional scaling (NMDS). Finally, assessment integrating five benthic quality elements, including: 1) PTSs; 2) metals and metalloids; 3) sediment toxicity; 4) sediment microbiome; and 5) benthic meiofaunal community, explained contamination of sediments associated with land-uses, locality, or habitat. Status of the benthic community could not be explained by single component and their associations were not quantitative. Results of the integrated assessment, considering multiple benthic quality elements were useful to address overall quality of sediment, and were consistent with chemical-, species-, or site-dependent pollution of sediments in the Bohai and Yellow Seas.

A comparative review and analysis of tentative ecological quality objectives (EcoQOs) for protection of marine environments in Korea and China

Ecological quality objectives (EcoQOs), as tools for implementing ecosystem approach, have long been acknowledged to protect the marine ecosystems and fisheries in regional seas through joint efforts by surrounding countries over the past decade. The present review analyzed the best available meta-data relating to the five ecosystem elements that were recently proposed by the Northwest Pacific Action Plan to evaluate the current status of coastal ecosystem health in marine environment of the Yellow Sea. We suggested the six tentative EcoQOs among five ecological quality elements including: 1) biological and habitat diversity; 2) invasive species; 3) eutrophication; 4) pollutants; and 5) marine litters. Environmental status was assessed, depending on the EcoQOs targets, by comparison to the world average values, existing environmental standards, or reported values of other regional seas. Results of analysis revealed that among the six tentative EcoQOs, two target objectives to marine biodiversity and concentrations of nutrients (viz., DIN and DIP) were met towards good environmental status. Whilst, three EcoQOs relating to hypoxia and red-tide, pollutants (persistent toxic substances and metals), and marine litters (including microplastics) did not meet and one relating to invasive species could not be judged due to insufficient data sets. The biggest weak point for developing suitable EcoQOs and assessing status of ecosystem health could be insufficient meta-data sets available and/or discrepancy in methodological details cross the data-sets or between the two targeted countries. Thus, the cooperation of neighboring countries, viz., Korea and China for the Yellow Sea, is necessary for the ecosystem based management of our regional sea in the future. Overall, this first time review for the assessment of target tentative EcoQOs in the Yellow Sea region encompassing coasts of Korea and China would provide a better understanding of the current status of environmental pollution and ecosystem health.

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, δ¹³C_TOC, and δ¹⁵N_TN) 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.

Integrated assessment of persistent toxic substances in sediments from Masan Bay, South Korea: Comparison between 1998 and 2014

Complexity of anthropogenic influences on coastal ecosystems necessitates use of an integrated assessment strategy for effective interpretation and subsequent management. In this study a multiple lines of evidence (LOE) approach for sediment assessment, that combined use of chemistry, toxicity, and benthic community structure in the sediment quality triad was used to assess spatiotemporal changes and potential risks of persistent toxic substances (PTSs) in sediments of Masan Bay highlighting "long-term changes" between 1998 and 2014. Specific target objectives encompassed sedimentary PTSs (PAHs, alkylphenols (APs), and styrene oligomers), potential aryl hydrocarbon receptor (AhR; H4IIE-luc assay)- and estrogen receptor (ER; MVLN assay)-mediated activities, and finally several ecological quality (EcoQ) indices of benthic community structure. Concentrations of target PTSs in Masan Bay sediments were generally less by half in 2014 compared to those measured in 1998. Second, AhR-mediated potencies in sediments also decreased during this time interval, whereas ER-mediated potencies increased (+3790%), indicating that there has been substantial ongoing, input of ER agonists over the past 16 years. Potency balance analysis revealed that only 3% and 22% of the AhR- and ER-mediated potencies could be explained by identified known chemicals, such as PAHs and APs, respectively. This result indicated that non-targeted AhR and ER agonists had a considerable presence in the sediments over time. Third, EcoQ indices tended to reflect PTSs contamination in the region. Finally, ratio-to-mean values obtained from the aforementioned three LOEs indicated that quality of sediments from the outer region of the bay had recovery more during the period of 16-years than did the inner region. Overall, the results showed that even with the progress supported by recent efforts from the Korean governmental pollution control, PTSs remain a threat to local ecosystem, especially in the inner region of Masan Bay.

Influence of sediment chemistry and sediment toxicity on macroinvertebrate communities across 99 wadable streams of the Midwestern USA

Simultaneous assessment of sediment chemistry, sediment toxicity, and macroinvertebrate communities can provide multiple lines of evidence when investigating relations between sediment contaminants and ecological degradation. These three measures were evaluated at 99 wadable stream sites across 11 states in the Midwestern United States during the summer of 2013 to assess sediment pollution across a large agricultural landscape. This evaluation considers an extensive suite of sediment chemistry totaling 274 analytes (polycyclic aromatic hydrocarbons, organochlorine compounds, polychlorinated biphenyls, polybrominated diphenyl ethers, trace elements, and current-use pesticides) and a mixture assessment based on the ratios of detected compounds to available effects-based benchmarks. The sediments were tested for toxicity with the amphipod Hyalella azteca (28-d exposure), the midge Chironomus dilutus (10-d), and, at a few sites, with the freshwater mussel Lampsilis siliquoidea (28-d). Sediment concentrations, normalized to organic carbon content, infrequently exceeded benchmarks for aquatic health, which was generally consistent with low rates of observed toxicity. However, the benchmark-based mixture score and the pyrethroid insecticide bifenthrin were significantly related to observed sediment toxicity. The sediment mixture score and bifenthrin were also significant predictors of the upper limits of several univariate measures of the macroinvertebrate community (EPT percent, MMI (Macroinvertebrate Multimetric Index) Score, Ephemeroptera and Trichoptera richness) using quantile regression. Multivariate pattern matching (Mantel-like tests) of macroinvertebrate species per site to identified contaminant metrics and sediment toxicity also indicate that the sediment mixture score and bifenthrin have weak, albeit significant, influence on the observed invertebrate community composition. Together, these three lines of evidence (toxicity tests, univariate metrics, and multivariate community analysis) suggest that elevated contaminant concentrations in sediments, in particular bifenthrin, is limiting macroinvertebrate communities in several of these Midwest streams.

Long-term changes in distributions of dioxin-like and estrogenic compounds in sediments of Lake Sihwa, Korea: Revisited mass balance

In the late 1990s, severe pollution by persistent organic contaminants (POCs) was observed in Lake Sihwa by use of a combination of instrumental analyses and in vitro bioassays. To determine long-term changes (>15-year gaps) in distributions of POCs and their potential toxic potencies in the given region, sediment assessments were reconducted. Target chemicals include polycyclic aromatic hydrocarbons (PAHs), alkylphenols (APs), and recently reported emerging chemicals, styrene oligomers (SOs). We employed in vitro bioassays (such as H4IIE-luc and MVLN) to determine potential sediment toxicities. The reduction rates of mean concentrations of APs and SOs in sediments between the two sampling years (1998 vs. 2015) were estimated to be 99% and 67%, respectively. Although APs and SOs significantly declined over the 15-year period, concentrations of PAHs were consistent. Results of the bioassays were consistent with the instrumental data, with relatively great concentrations of all target compounds being detected, particularly in inland creeks. Compositions of all target compounds exhibited changes in homologue patterns over the 15 years considered. This result indicated varying and/or continuing sources in this region. In particular, PAHs were dominated by higher-molecular-weight PAHs (e.g., benzo[g,h,i]perylene and benzo[b]fluoranthene) in recent years. This result might indicate consumption of oil-related fuels. Quantitative potency balance analysis revealed that concentrations of instrumentally-derived equivalents accounted for as little as 18.5% of bioassay-derived equivalents, which indicated significant amounts of unknown and/or unmeasured compounds were present. The present study documented the continuing severe pollution by selected POCs in the Lake Sihwa region over the last 15 years, indicating a lack of management in the area studied.

Integrating causation in investigative ecological weight of evidence assessments

Weight of evidence (WOE) frameworks integrate environmental assessment data to reach conclusions regarding relative certainty of adverse environmental effects due to stressors, possible causation, and key uncertainties. Such studies can be investigative (i.e., determining whether adverse impact is occurring to identify a need for management) or retrospective (i.e., determining the cause of a detected impact such that management efforts focus on the correct stressor). Such WOE assessments do not themselves definitively establish causation; they provide the basis for subsequent follow-up studies to further investigate causation. We propose a modified investigative WOE framework that includes an additional weighting step, which we term "direction weighting." This additional step allows for the examination of alternative hypotheses and provides improved certainty regarding possible causation. To our knowledge, this approach has not been previously applied in investigative ecological WOE assessments. We provide a generic example of 2 conflicting hypotheses related to a mine discharging treated effluent to a freshwater lake: chemical toxicity versus nutrient enrichment. Integr Environ Assess Manag 2017;13:702-713. © 2016 SETAC.

Environmental Impacts and Recovery After the Hebei Spirit Oil Spill in Korea

The Hebei Spirit oil spill (HSOS) on December 7, 2007 was the worst oil spill recorded in Korea, with the release of approximately 10,900 tons of crude oil and 375 km of coastline polluted along the west coast of Korea. Cleanup operation was conducted by official and contract responders as well as volunteers for massive oil containment and removal of heavy accumulations of stranded oil. Together with the oil cleanup, a long-term environmental impact assessment (EIA) of the HSOS was initiated based on the Marine Environmental Management Act, which covers oil contamination in a multimedia environment, toxic effects on organisms, and ecosystem injury. This review summarizes the long-term monitoring results of HSOS EIA focused on (1) pollution status of seawater, sediment, and bivalves, (2) ecotoxicological effects, and (3) ecosystem recovery. Overall, concentrations of petroleum hydrocarbons in the environment indicated that their concentrations were well down to at or near background or pre-spill contamination levels at most sites after 1 year. The potential toxic effects of residual oils in sediments have decreased to background levels in most coastal areas of Taean. The entire ecosystem in the most affected area of the Taean coasts appear to be considerably, but not fully, recovered at present, namely after 8 years of the HSOS. The presence of lingering oil and elevated contamination levels at several sites still require continuous long-term monitoring.

Impacts of environmental and anthropogenic stresses on macrozoobenthic communities in Jinhae Bay, Korea

In this study, spatiotemporal dynamics of macrofaunal assemblages and their associations with environmental conditions were examined in Jinhae Bay (10 sites), where the obvious sources of pollution including industries, oyster farms (hanging cultures), and municipal discharges has surrounded. The survey had performed over five consecutive seasons in 2013-2014. Target sedimentary variables included grain size, organic content, C/N ratio, carbon and nitrogen stable isotope ratios, and some heavy metals. Five ecological quality indices (EcoQ) were calculated from the benthic community data to evaluate ecological qualities in site-specific manner. Jinhae Bay is a shallow (depths range, 11-24 m) and typical semi-enclosed bay. The benthic environments represented mud dominated bottoms (>70%) with fairly substantial organic content levels (>2%) over all five seasons. Seasonal patterns were observed with peak abundances in the spring and distinctive macrozoobenthos species shifts in the summer. The spring bloom could be explained by drastic increases of some polychaetes, mainly Capitella sp., at certain site, particularly near the shore. The oyster farms situated in the innermost locations seem to provide organic-rich bottoms being dominated by opportunistic species and/or organic pollution indicator species, such as Lumbrineris longifolia, Capitella sp., and Paraprionospio patiens. In general, the EcoQ indicators indicated that Jinhae Bay was moderately polluted, with exceptionally poor EcoQ in a few locations during the specific season(s). Overall, adverse effects on benthic community was broadly attributable to contaminations of heavy metals and nearby aquatic farm activities in Jinhae Bay, which requires a prompt action toward ecosystem-based management practice in the given area.

Hard science is essential to restoring soft-sediment intertidal habitats in burgeoning East Asia

Intertidal soft-sediment ecosystems such as mangrove, saltmarsh, and tidal flats face multiple stresses along the burgeoning East Asia coastline. In addition to direct habitat loss, ecosystem structure, function, and capacity for ecosystem services of these habitats are significantly affected by anthropogenic loss of hydrologic connectivity, introduction of invasive exotic species, and chemical pollution. These dramatic changes to ecosystem structure and function are illustrated by four case studies along the East Asian coast: the Mai Po Marshes in Hong Kong, the Yunxiao wetlands in Fujian, China, and the Lake Sihwa and Saemangeum tidal flats in Korea. While investment in restoration is increasing significantly in the region, the lack of key basic knowledge on aspects of the behaviour of intertidal soft-sediment ecosystems, particularly those in Asia, impairs the effectiveness of these efforts. The relationship between biodiversity and ecosystem function for relatively species-poor mangrove, seagrass, and saltmarsh systems has implications for restoration targeting monospecific plantations. The trajectory of recovery and return of ecosystem function and services is also poorly known, and may deviate from simple expectations. As many introduced species have become established along the East Asian coast, their long-term impact on ecosystem function as well as the socio-economics of coastal communities demand a multidisciplinary approach to assessing options for restoration and management. These knowledge gaps require urgent attention in order to inform future restoration and management of intertidal soft-sediment ecosystems in fast-developing East Asia.

Assessment of potential biological activities and distributions of endocrine-disrupting chemicals in sediments of the west coast of South Korea

The west coast of Korea has experienced environmental deterioration for more than half a century. In the present study, we specifically aimed to: i) evaluate potential toxicities of contaminants in sediments that cause effects mediated through the aryl hydrocarbon receptor (AhR) and estrogen receptor (ER); ii) determine spatio-temporal distributions of polycyclic aromatic hydrocarbons (PAHs) and alkylphenols (APs); and iii) identify causes of greater potencies of samples. From 2010 to 2014, sediments were collected from 12 major estuarine and coastal regions along the west coast of South Korea. In vitro cell bioassays were performed to determine AhR- and ER-mediated potencies using H4IIE-luc and MVLN cells, respectively. Fifteen PAHs and six APs in sediments were identified by GC/MSD. Results of bioassays generally showed a low-to-moderate degree of contamination, however, greater AhR- and ER-mediated potencies were measured at some locations. Concentrations of PAHs and APs varied among locations, which indicated that sources were independently affected by the surrounding environment (e.g., industrial complex and cities). Results of bioassays were generally well correlated with concentrations of putative causative chemicals. Benzo[k]fluoranthene, dibenz[a,h]anthracene, and benzo[b]fluoranthene were the major AhR agonists, explaining approximately 30% of the bioassay-derived benzo[a]pyrene equivalent concentration (BaP-EQ). Unknown AhR and ER agonists and potential mixture effects remain in question. Overall, the present study provides baseline information on chemical contaminations and potential toxicity of sediments in a fairly wide geographical region of the west coast of South Korea.

Arsenic speciation in water, suspended particles, and coastal organisms from the Taehwa River Estuary of South Korea

Water, suspended particulate matter (SPM), and biota samples were collected from the Taehwa River Estuary to determine the distributions, partitioning, and bioaccumulation of arsenicals. Six forms of As were quantitated by the use of HPLC-ICP/MS. As was found mainly near urban and industrial areas, and inorganic As(V) was the predominant As form in both water and SPM. Particulate arsenicals were found at the greatest concentrations in coarse particles (>180μm), followed by medium (30-180μm) and fine (0.45-30μm) particles, in freshwater. Arsenical concentrations were similar across the three particle fractions in saltwater. Field-based distribution coefficient (Kd) values for As depended strongly on SPM, with a less robust dependence on salinity. Concentrations of As were greater in macroalgae than in marine animals, such as fishes, bivalves, crabs, shrimps, and gastropods. Overall, the results of the present study provide useful information on the behaviors and fate of arsenicals in an estuarine environment.

Are styrene oligomers in coastal sediments of an industrial area aryl hydrocarbon-receptor agonists?

Effect-directed analysis (EDA) was performed to identify the major aryl hydrocarbon receptor (AhR) agonists in sediments collected from a highly industrialized area (Lake Shihwa, Korea). Great AhR-mediated potencies were found in fractions containing aromatic compounds with log Kow values of 5-8, and relatively great concentrations of styrene oligomers (SOs) and polycyclic aromatic hydrocarbons (PAHs) were detected in those fractions. Until now, there was little information on occurrences and toxic relative potencies (RePs) of SOs in coastal environments. In the present study; i) distributions and compositions, ii) AhR binding affinities, and iii) contributions of SOs to total AhR-mediated potencies were determined in coastal sediments. Elevated concentrations of 10 SOs were detected in sediments of inland creeks ranging from 61 to 740 ng g(-1) dry mass (dm), while lesser concentrations were found in inner (mean = 33 ng g(-1) dm) and outer regions (mean = 25 ng g(-1) dm) of the lake. Concentrations of PAHs in sediments were comparable to those of SOs. 2,4-diphenyl-1-butene (SD3) was the predominant SO analogue in sediments. SOs and PAHs were accumulated in sediments near sources, and could not be transported to remote regions due to their hydrophobicity. RePs of 3 SOs could be derived, which were 1000- to 10,000-fold less than that of one representative potent AhR active PAH, benzo[a]pyrene. Although concentrations of SOs in sediments were comparable to those of PAHs, the collective contribution of SOs to total AhR-mediated potencies were rather small (<1%), primarily due to their smaller RePs. Overall, the present study provides information on distributions and AhR binding affinities for SOs as baseline data for degradation products of polystyrene plastic in the coastal environment.

Performance evaluation and validation of ecological indices toward site-specific application for varying benthic conditions in Korean coasts

Although several ecological indices have been developed worldwide to assess the ecological quality (EcoQ) status of coastal environments, their applicability remains in question. The present study evaluated the performance of 14 univariate and multivariate indices selected to provide a good description of benthic EcoQ status. We specifically investigated on i) spatial and regional variability, ii) (dis)similarity between ecological indices, and iii) the association of selected indices against heavy metal pollution. Benthic community data were collected from six coastal regions of Korea (n=365) that have varying land-use activity in adjacent inland areas (municipal, industrial, and rural). Abiotic sedimentary parameters were also considered as possible pressures associated with benthic community responses, including grain size, organic carbon content, and heavy metal pollution. The macrozoobenthic biodiversity and EcoQ results generally well reflected the geographical settings and the pollution gradient of heavy metals between regions. Among the six selected indices (H', AMBI, BPI, BQI, EQR, and M-AMBI), BPI appeared to be the most tolerant index, with >90% of locations being classified as "High" to "Good" while EQR showed the clear classification across the EcoQ status range. Significant disagreement between BQI vs. AMBI, BPI vs. M-AMBI, and AMBI vs. M-AMBI were found. Overall, single or limited indices seemed to over- or underestimate the given benthic conditions, warranting the use of site-specific indices at specific areas and/or locations. In conclusion, our study demonstrates the utility of applying different ecological or multivariate indices to infer the general ecological status of specific sites to gauge the extent of sedimentary pollution.

Ecological effects of contaminated sediments following a decade of no industrial effluents emissions: the Sediment Quality Triad approach

Sediments contaminated by industrial effluents a decade after the emissions were stopped were statistically compared to sediments from reference channels, using the Sediment Quality Triad approach. The metals and metalloid concentrations, mainly Hg and As, increased towards the upper part of a contaminated channel, where the industrial discharge was located. A bioaccumulation assay with Scrobicularia plana showed the highest bioaccumulation and mortality in the most contaminated sediments and bioaccumulation strongly correlated with the sediments metals and metalloid concentrations. The resident macroinvertebrate community also showed significant differences between the contaminated and reference channels, in the upper areas, where the community was most affected. All three elements of the quality triad rejected the null hypothesis and indicated that despite the emissions ceasing in 2004, sediments remain contaminated by high levels of metals and metalloid, leading to bioaccumulation and with severe community level consequences.

Pollution characteristics and possible sources of seldom monitored trace elements in surface sediments collected from Three Gorges Reservoir, China

A geochemical study of Three Gorges Reservoir (TGR) sediments was carried out to analyze the concentrations, distribution, accumulation, and potential sources of the seldom monitored trace elements (SMTEs). The mean concentrations of Li, B, Be, Bi, V, Co, Ga, Sn, Sb, and Tl were 47.08, 2.47, 59.15, 0.50, 119.20, 17.83, 30.31, 3.25, 4.14, and 0.58 mg/kg, respectively. The concentrations of total SMTEs, together with their spatial distribution, showed that the SMTEs were mainly due to anthropogenic inputs in the region of TGR. The assessment by Geoaccumulation Index indicates that Tl, Be, V, Co, and Fe are at the unpolluted level; Bi, Li, Ga, and Sn were at the "uncontaminated to moderately contaminated" level. However, B was classified as "moderately contaminated" level and Sb was ranked as "strongly contaminated" level. The pollution level of the SMTEs is Sb > B > Bi > Li > Ga > Sn > Tl > Be > V > Co > Fe. The results of Correlation Analysis and Principal Component Analysis indicated Be, V, Co, Ga, Sn, Tl, Bi, and Fe in sediments have a natural source. B and Li were positively correlated with each other and mainly attributed into similar anthropogenic input. In addition, Sb has less relationship with other SMTEs, indicating that Sb has another kind of anthropogenic source.