Persistent Toxic Substances in Sediments of ... - ACS Publications

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Persistent Toxic Substances in Sediments of Korean Coastal Waters: A Review Seongjin Hong,1 Seo Joon Yoon,2 Yeonjung Lee,1 and Jong Seong Khim*,2 1Department

of Ocean Environmental Sciences, Chungnam National University, Daejeon 34134, Republic of Korea 2School of Earth and Environmental Sciences & Research Institute of Oceanography, Seoul National University, Seoul 08826, Republic of Korea 3Marine Ecosystem and Biological Research Center, Korea Institute of Ocean Science and Technology, Ansan 15627, Republic of Korea *E-mail: [email protected]

In this chapter, studies on persistent toxic substances (PTSs) in sediments of Korean coastal waters over the past two decades, including 90 reports published since 1997, were collected and reviewed. The distributions and concentrations of the following 12 chemical groups in coastal sediments were analyzed: PCDD/Fs, PCBs, DDTs, HCHs, CHLs, PAHs, alkyl-PAHs, NPs, BTs, PBDEs, HBCDs, and SOs. Sedimentary PTSs are known to be widely distributed along the Korean coasts. Spatial distribution data suggested the presence of multiple independent sources of PTSs, with hotspot areas (e.g., Lake Sihwa, Masan Bay, Ulsan Bay, and Yeongil Bay) producing high pressures of certain PTSs. Temporal trends of sedimentary PTSs show decreases in recent years which seem to be associated with chemical controls and regulations. This review provides updated information, collation of PTSs studies, and discussion of future research directions for PTS contamination in Korean coastal waters.

© 2016 American Chemical Society Loganathan et al.; Persistent Organic Chemicals in the Environment: Status and Trends in the Pacific Basin Countries I ... ACS Symposium Series; American Chemical Society: Washington, DC, 2016.


Abbreviations BTs: butyltins CCME: Canadian Council of Ministers of the Environment CHLs: chlordanes Co-PCBs: coplanar PCBs DDTs: dichloro-diphenyl-trichloroethane ERL: effects range low ERM: effects range median EPS: expanded polystyrene FEQG: federal environmental quality guidelines HBCDs: hexabromocyclododecanes HCHs: hexachlorohexanes HSOS: Hebei Spirit oil spill HSV: higher screening value ISQG: interim sediment quality guidelines KIOST: Korea Institute of Ocean Science & Technology LSC: lower screening value MOF: Ministry of Oceans and Fisheries NIER: National Institute of Environmental Research NOAA: National Oceanic and Atmospheric Administration NPEOs: nonylphenol ethoxylates NPs: nonylphenols PAHs: polycyclic aromatic hydrocarbons PBDEs: polybrominated diphenyl ethers PCBs: polychlorinated biphenyls PCDD/Fs: polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans PEL: predicted effects level POPs: persistent organic pollutants PTSs: persistent toxic substances SDs: styrene dimers SOs: styrene oligomers STs: styrene trimers TBT: tributyltin TEQs: toxicity equivalents TEL: threshold effect level USEPA: U.S. Environmental Protection Agency WWTPs: wastewater treatment plants XPS: extruded polystyrene

Introduction Persistent toxic substances (PTSs), such as polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), dichloro-diphenyl-trichloroethane (DDTs), hexachloro-hexanes (HCHs), chlordanes (CHLs), polycyclic aromatic hydrocarbons (PAHs), alkyl-PAHs, nonylphenols (NPs), butyltins (BTs), polybrominated diphenyl ethers (PBDEs), 156 Loganathan et al.; Persistent Organic Chemicals in the Environment: Status and Trends in the Pacific Basin Countries I ... ACS Symposium Series; American Chemical Society: Washington, DC, 2016.


hexabromocyclododecanes (HBCDs), and styrene oligomers (SOs), are released into the environment as waste or by-products from industrial and domestic applications. They may be introduced directly or indirectly into marine environments as chemicals or as constituents of organic matter, waste, or crude oil. Land-based discharge via estuaries is the most prevalent route of PTS release, followed by atmospheric input, maritime transport, ocean dumping, and oil spill accidents (1–3). Once PTSs have entered coastal environments, they undergo various processes in the biogeochemical cycles of the water column. Generally, PTSs are first adsorbed onto suspended particles, due to their hydrophobic nature, and then settle and accumulate in coastal sediments. They can accumulate in marine organisms, become biomagnified through the food chain, and may be degraded by microbial activities (3–5). Distributions of PTSs in marine environmental media are strongly dependent on the particular substances’ physico-chemical properties (3). Characteristically, PTSs are hydrophobic with log Kow values ranging from 3 to 7 (6, 7), giving them low water solubilities, low degradation rates, and high bioaccumulation and sediment adsorption potentials. The solubility of PTSs decreases as they move from river to estuary waters owing to the greater ionic strength of seawater relative to freshwater. Consequently, PTS adsorption onto suspended particles and sediments is greater in estuarine sites than in freshwater sites (8–10), resulting in PTS accumulation in estuarine and coastal sediments, with relatively low levels reaching remote regions by oceanic currents. Accumulated PTSs can persist in coastal sediments for long periods of time where they can have adverse effects on benthic organisms. After organic matter has been deposited into sediments, it is degraded through a combination of biological and chemical processes under suboxic and anoxic conditions within superficial sediments in a process known as eo- or early diagenesis (11, 12). During eodiagenesis, while labile organic matter is being degraded, refractory organic matter, including PTSs, remains in sediments. Various biotic and abiotic factors affect the sedimentary accumulation of organic chemicals, such as organic carbon content, grain size, chemical hydrophobicity, degradability, and microbial activity (13). High organic matter content in sediments can lead to dissolved oxygen depletion in bottom water, which has adverse effects on benthic animals.

Review Framework Rapid economic growth in South Korea has caused severe pollution in the past three decades. PTS contamination in South Korean coastal sediments has been monitored extensively since the mid-1990s; and there has been rapid growth in research activities related to sedimentary PTSs in the past two decades. The ample PTS monitoring data accumulated allowed us to conduct a fairly comprehensive assessment of Korean coastal areas and thereby to elucidate spatial pollution patterns on a regional scale. We collected and reviewed previous studies examining PTSs in the sediments of Korean coastal waters, focusing on the following 12 groups of PTSs: PCDD/Fs 157 Loganathan et al.; Persistent Organic Chemicals in the Environment: Status and Trends in the Pacific Basin Countries I ... ACS Symposium Series; American Chemical Society: Washington, DC, 2016.


(14–30), PCBs (14, 16, 20, 24, 31–51), DDTs (14, 32–35, 37–39, 41, 44–49, 51–54), HCHs (14, 32–35, 37–39, 41, 44–49, 51–54), CHLs (35, 38, 39, 41, 44–49, 51–54), PAHs (14, 16, 20, 24, 27, 37, 43–49, 51, 55–66), alkyl-PAHs (63, 67–72), NPs (17, 27, 35, 37, 43–49, 51, 59, 66, 73–82), BTs (14, 35, 37, 43, 51, 59, 83–97), PBDEs (17, 20, 27, 36, 43, 73, 98–103), HBCDs (73, 103), and SOs (55, 66). A total of 90 reports on PTSs in Korean sediments have been published in South Korean and international journals from 1997 to 2016 (Figure 1). The aforementioned chemical groups have, for the most part, been subjected to similar intensities of research interest, with the exception of emerging PTSs, such as HBCDs, SOs, and alkyl-PAHs (derived mainly from marine oil spills). Among the aforementioned 12 groups of PTSs, sedimentary PAHs and PCBs are the most studied in Korea. Early PTS studies in Korea were limited to reporting environmental levels of classical persistent organic pollutants, such as PCDD/Fs, PCBs, and organochlorine pesticides. Later studies have addressed contamination levels of more recently recognized PTSs, such as PBDEs, HBCDs, and SOs.

Figure 1. Number of publications and target chemical groups among studies of persistent toxic substances in sediments of the Korean coastal waters.

South Korean sedimentary PTS studies have concentrated on highly polluted regions (Table 1 and Figure 2), including, principally, the 20 regions assessed in this review. These 20 regions include 9 regions along the western coast (Incheon Harbor, Gyeonggi Bay, Lake Sihwa, Namyang Bay, Asan Bay, Taean Coast, Geum River Estuary, Saemangeum Coast, and Youngsan River Estuary), 7 regions along the southern coast (Yeosu Bay, Gwangyang Bay, Masan Bay, Jinhae Bay, Gohyun Bay, Nakdong River Estuary, and Busan Harbor), and 4 regions along the eastern coast (Onsan Bay, Ulsan Bay, Yeongil Bay, and Uljin Coast). Among these regions, the highly industrialized south-eastern coastal areas, namely Masan Bay, Jinhae Bay, Gwangyang Bay, Ulsan Bay, and Busan Harbor, have been considered of particular concern for sedimentary PTS pollution in South Korea.

158 Loganathan et al.; Persistent Organic Chemicals in the Environment: Status and Trends in the Pacific Basin Countries I ... ACS Symposium Series; American Chemical Society: Washington, DC, 2016.


Figure 2. Map of Korean coastal study areas, with respective numbers of publications.

Sediment quality guidelines for PTSs were chosen to assess the potential ecological risks (Table 2). Concentrations of PTSs in the Korean sediments were compared to the guidelines of PCDD/Fs (104), PCBs (105), DDTs (105), HCHs (106), CHLs (106), PAHs (106), NPs (107), BTs (108), PBDEs (109), and HBCDs (110). In the present study, we collected and reviewed major findings regarding PTSs contamination in sediments of Korean coastal waters over the past two decades. Chemical analysis data obtained from 2,740 coastal sites were examined. Our aim was to document key sources, spatial distributions, potential risks, and temporal trends of 12 groups of sediment accumulated PTSs for use in future monitoring and risk assessment. This review provides an information update regarding currently available data on Korean sedimentary PTSs to support researchers’ and regulators’ understanding of PTSs contamination in Korean coastal waters. In addition, the present findings may guide the identification of current hotspot areas and prioritization of PTS monitoring, assessments, and management practices. 159 Loganathan et al.; Persistent Organic Chemicals in the Environment: Status and Trends in the Pacific Basin Countries I ... ACS Symposium Series; American Chemical Society: Washington, DC, 2016.

160


Table 1. Summary of study efforts on persistent toxic substances in sediments of Korean coastal waters Study area

Type

Period

Target chemical group(s)

1. Incheon Harbor

Bay

1996-2010

PCDD/Fs, PCBs, DDTs, HCHs, CHLs, PAHs, NPs, BTs, PBDEs, HBCDs

2. Gyeonggi Bay

Bay

1995-2015


3. Lake Sihwa

Inland

2000-2015

PCDD/Fs, PCBs, DDTs, HCHs, CHLs, PAHs, NPs, PBDEs, SOs

Lake

1996-2015

PCDD/Fs, PCBs, DDTs, HCHs, CHLs, PAHs, NPs, PBDEs, HBCDs, SOs

4. Namyang Bay

Bay

1996

PCBs, DDTs, HCHs, CHLs

5. Asan Bay

Bay

2000-2007

PCDD/Fs, PCBs, DDTs, HCHs, CHLs, PAHs, NPs, BTs

6. Taean Coast

Coast

2000-2015

PCDD/Fs, PCBs, DDTs, HCHs, PAHs, alkyl-PAHs, BTs

7. Geum River Estuary

Estuary

2000-2014

PCDD/Fs, PCBs, DDTs, HCHs, PAHs, NPs, BTs, SOs

8. Saemangeum Coast

Coast

2000-2014

PCDD/Fs, PCBs, DDTs, HCHs, CHLs, PAHs, NPs, BTs, SOs

9. Youngsan River Estuary

Estuary

2000-2010

PCDD/Fs, PCBs, DDTs, HCHs, PAHs, NPs, BTs

10. Yeosu Bay

Bay

1999-2014

PCDD/Fs, PCBs, DDTs, HCHs, PAHs, alkyl-PAHs, NPs, BTs, PBDEs, HBCDs

11. Gwangyang Bay

Bay

1996-2010


12. Masan Bay

Inland

2000

PCBs, DDTs, HCHs, CHLs, PAHs, NPs

Bay

1992-2014


Loganathan et al.; Persistent Organic Chemicals in the Environment: Status and Trends in the Pacific Basin Countries I ... ACS Symposium Series; American Chemical Society: Washington, DC, 2016.


Type

Period


13. Jinhae Bay

Inland

2011

PBDEs

Bay

1995-2014


14. Gohyun Bay

Bay

2000-2007

PCDD/Fs, PCBs, DDTs, HCHs, PAHs, BTs, PBDEs, HBCDs

15. Nakdong River Estuary

River

1999

PCBs

Estuary

2002-2005

PCDD/Fs, PBDEs, HBCDs

16. Busan Harbor

Bay

2000-2010

PCDD/Fs, PCBs, DDTs, HCHs, PAHs, NPs, BTs, PBDEs, HBCDs

17. Onsan Bay

Inland

1999


River

1999


Bay

1999-2007


Inland

1999


River

1999


Bay

1996-2010


Inland

2001-2011

PCDD/Fs, PCBs, PAHs, NPs

Bay

1998-2007


161

Study area

18. Ulsan Bay

19. Yeongil Bay

Continued on next page.


Study area

Type

Period


20. Uljin Coast

Coast

2000-2007

PCDD/Fs, PCBs, DDTs, HCHs, PAHs, BTs, PBDEs, HBCDs

Nationwide

Bay /Coast

1997-2010


162


Table 1. (Continued). Summary of study efforts on persistent toxic substances in sediments of Korean coastal waters


Table 2. Sediment quality guidelines of persistent toxic substances used in the present review Chemical group

Unit

Sediment quality guidelines

Remark & References

PCDD/Fs

pg TEQs g-1

ISQG

0.58

PEL

21.5

Canadian sediment quality guidelines for the protection of aquatic life (104)

ERL

22.7

ERM

180

ERL

1.58

ERM

46.1

ISQG

0.32

PEL

0.99

ISQG

2.26

PEL

4.79

ISQG

768

PEL

7071


PCBs

DDTs

HCHs

CHLs

PAHs

ng g-1 dw

ng g-1 dw

ng g-1 dw

ng g-1 dw

ng g-1 dw

Possible toxicological significance of chemical concentrations in sediments (105) Possible toxicological significance of chemical concentrations in sediments (105) Canadian sediment quality guidelines for the protection of aquatic life (106) Canadian sediment quality guidelines for the protection of aquatic life (106) Canadian sediment quality guidelines for the protection of aquatic life (106)

NPs

ng g-1 dw

ISQG

1000

Canadian sediment quality guidelines for the protection of aquatic life (107)

BTs

ng g-1 dw

LSC

1255

HSV

17570

Recommendations for screening values for tributyltin in sediments (108)

PBDEs

ng g-1 dw

FEQG

6143

Federal Environmental Quality Guidelines of PBDEs (109)

HBCDs

ng g-1 dw

FEQG

1600

Federal Environmental Quality Guidelines of HBCDs (110)

TEL: threshold effect level; PEL: predicted effects level; ERL: effects range low; ERM: effects range median; ISQG: interim sediment quality guidelines; LSC: lower screening value; HSV: higher screening value; FEQG: federal environmental quality guidelines.

Sedimentary PTSs in Korean Coastal Waters PCDD/Fs PCDD/Fs are formed as by-products ofwaste incinerators, chemical industries, and wastewater effluents (26). PCDD/Fs and coplanar PCBs (Co-PCBs) are widely distributed in environmental media in industrial and municipal areas. They have received considerable attention due to their high toxicity potential and bioaccumulative characteristics (26, 111). A nationwide 163 Loganathan et al.; Persistent Organic Chemicals in the Environment: Status and Trends in the Pacific Basin Countries I ... ACS Symposium Series; American Chemical Society: Washington, DC, 2016.


survey of chemical emission and inventory in South Korea identified municipal solid waste incinerators and steel industry sites as the major sources of PCDD/Fs (112, 113).

Figure 3. Distributions of PCDD/Fs in sediments of Korean coastal waters. (Data sources: (14–30). Sediment quality guideline: (104)).



Concentrations of PCDD/Fs and Co-PCBs in sediments from Korean coastal waters are highly variable (Figure 3). The greatest TEQ (toxicity equivalent) concentrations of PCDD/Fs and Co-PCBs were detected in highly industrialized regions, most notably the inland creeks of the Lake Sihwa (1.04–1,770 pg TEQ g-1 dw), followed by those of Yeongil Bay (0.43–1,040 pg TEQ g-1 dw) and Masan Bay (3.6–423.8 pg TEQ g-1 dw) (24, 26, 27), indicating that industrial and municipal areas in the vicinities of these regions are discharging large amounts of PCDD/Fs and Co-PCBs. Due to their high hydrophobicity, PCDD/Fs and Co-PCBs tend to adsorp onto suspended solids that settle in aquatic sediments. The TEQ concentrations of PCDD/Fs reported for several industrial regions exceed the Canadian sediment quality guidelines for protection of aquatic life (104). Temporal trends of sedimentary PCDD/Fs contamination showed slightly decreasing trends in the regions of Lake Sihwa from 2005 to 2007 (26, 30), Yeongil Bay from 1998 to 2005 (25, 29, 30), and Masan Bay from 2004 to 2013 (17, 20, 22, 27) (Figure 3). These reductions suggest that the strict regulations for flue gases from waste incinerators enacted in recent decades may be effective for modulating PCDD/Fs levels in coastal sediments (114).

PCBs PCBs are persistent, ubiquitous, and toxic environmental contaminants that represent a global concern due to their persistence, bioaccumulation, and toxicity potential to humans and wildlife (3, 6, 38). They have been detected in various environmental media over the last 30 years worldwide. Despite the ban on PCBs use as a dielectic fluid in capacitors and transformers in South Korea since the 1970s, PCBs are still frequently detected in environmental samples (Figure 4). The greatest concentrations of PCBs were found in samples from highly industrialized regions, namely Gyeonggi Bay (1.0–580 ng g-1 dw) on the western coast, followed by Busan Bay (5.7–199 ng g-1 dw) on the southern coast, and Yeongil Bay (1.0–170 ng g-1 dw) on the eastern coast (24, 40, 50). Sedimentary PCBs concentrations in some sites exceeded established sediment quality guidelines, signifying possible toxicological significance (105). Temporal trends in sedimentary PCBs contamination showed slightly decreasing trends in the regions of Gyeonggi Bay from 1995 to 2003 (33, 37, 40, 50), Masan Bay from 1998 to 2013 (14, 20, 36, 43, 45), and Busan Bay from 2000 to 2007 (14, 31, 40) (Figure 4). Management plans for PCBs emission sources, such as incomplete combustion and industrial processes (75), should be implemented in current hotspot areas.



Figure 4. Distributions of PCBs in sediments of Korean coastal waters. (Data sources: (14, 16, 20, 24, 31–51). Sediment quality guideline: (105)).



Figure 5. Distributions of DDTs in sediments of Korean coastal waters. (Data sources: . Sediment quality guideline: (105)).



DDTs Due to the persistent, ubiquitous, and biologically harmful properties of DDTs, DDTs contamination has been of great concern worldwide for several decades. Although their production and use has mostly been banned since the 1970s, DDTs are still found in marine samples widely distributed along the Korean coast (14, 75, 113). DDTs were banned for agricultural uses in South Korea in 1971. Approximately 758 tons and 1,320 tons of DDT were produced in and imported into South Korea, respectively, from 1949 to 1971 (75). The presently reviewed data indicate continued widespread DDTs contamination of Korean coastal sediments (Figure 5), presumably due to DDTs constituting the major organochlorine pesticides in use in Korea in the 20th century. Masan Bay, Ulsan Bay, and Incheon Harbor, in particular, were identified as areas of concern for DDT contamination (41, 44, 54). In 2007, some sites in Masan Bay exceeded the ERM guideline (41). In line with PTS concentrations overall, DDTs concentrations in coastal sediments showed a slight decreasing trend in recent decades. HCHs HCHs were used extensively as organochlorine pesticides around the world between the 1950s and early 1980s owing to their broad-spectrum insecticide efficacy for fruit, grain, and seed applications. They have been banned or restricted in many countries, including South Korea, since the 1970s (3, 4, 41, 113). Due to their semi-volatility and high persistence, HCHs can be transported over long distances via atmospheric circulation and ocean currents (7). HCHs were found to be widely distributed in sediments from Korean coastal environments (Figure 6). Very high HCHs concentrations were found in inland sediment samples from Lake Sihwa (0.55–10.7 ng g-1 dw) and Masan Bay (0.01–44.4 ng g-1 dw) (49). HCHs concentrations were particularly concerning in sediments from industrialized and urbanized regions of southeastern Korea, including Masan Bay, Ulsan Bay, and Yeongil Bay, where they exceeded predicted effect levels suggested by the Canadian Council of Ministers of the Environment (CCME) (44, 47–49). CHLs The lipophilic character of CHLs enables them to persist in the environment and undergo bioaccumulation in lipid-rich tissues of organisms; CHLs biomagnification through the food chain is a major concern. CHLs continued to be used as additive agents even after they were banned from use as pesticides (38). Though at lower concentrations than DDTs and HCHs, CHLs distribution trends in Korean coastal waters were similar to the trends observed for other organochlorine pesticides (41, 44, 54) (Figure 7). Previous monitoring studies documented CHLs concentrations in sediments sampled from Gyeonggi Bay (0.53–130 ng g-1 dw) in 1996 (54) that exceeded the predicted effects level suggested by the CCME (106). Because CHLs have been studied less than other pollutants in Korean sediments, temporal trends could not be evaluated. 168 Loganathan et al.; Persistent Organic Chemicals in the Environment: Status and Trends in the Pacific Basin Countries I ... ACS Symposium Series; American Chemical Society: Washington, DC, 2016.


Figure 6. Distributions of HCHs in sediments of Korean coastal waters. (Data sources: (14, 32–35, 37–39, 41, 44–49, 51–54). Sediment quality guideline: (106)).



Figure 7. Distributions of CHLs in sediments of Korean coastal waters. (Data sources: (35, 38, 39, 41, 44–49, 51–54). Sediment quality guideline: (106)).

PAHs PAHs are ubiquitously distributed contaminants formed as by-products of some types of combustion, particularly burning of coal and wood (65). Natural process (e.g., wildfires) and anthropogenic activities (e.g., fossil fuel combustion) are considered to be the major sources of PAH input into the marine environment (65, 115, 116). PAHs are transported to the marine environment through atmospheric deposition, estuary flow, urban wastewater runoff, and oil spills. Once introduced into an aquatic ecosystem, PAHs accumulate in coastal sediments due to their hydrophobicity and strong binding affinity for organic matter (16, 60, 64). Because PAHs are known to have carcinogenic, genotoxic, and mutagenic effects on marine organisms, PAH contamination is a serious environmental concern. Monitoring of sedimentary PAHs has been conducted in South Korea extensively in the past 20 years (Figure 8). Our data analysis of sedimentary PAHs indicated that PAHs are widely distributed in Korean coastal waters, with Yeongil Bay, Ulsan Bay, and Gwangyang Bay being identified as areas of concern for PAH pollution (24, 58, 61, 62, 64). PAH concentrations in sediments from some sites exceeded the sediment quality guideline (PEL), indicating that environmental management of PAH contamination is needed. Temporal distributions of PAHs suggested that the concentrations decreased slightly in Masan Bay from 1997 to 2014 (43, 45, 63, 65) as well as in Ulsan Bay from 1997 to 2007 (14, 58, 61, 64) and in Lake Sihwa from 2000 to 2015 (37, 55, 64), indicating that recent regulations on flue gases from waste incinerators may be curbing PAHs contamination in Korean coastal areas. 170 Loganathan et al.; Persistent Organic Chemicals in the Environment: Status and Trends in the Pacific Basin Countries I ... ACS Symposium Series; American Chemical Society: Washington, DC, 2016.




Figure 8. Distributions of PAHs in sediments of Korean coastal waters on (a) western coast and (b) southern and eastern coasts. (Data sources: (14, 16, 20, 24, 27, 37, 43–49, 51, 55–66). Sediment quality guideline: (106)).



Alkyl-PAHs Alkyl-PAHs in marine environments are derived mainly from crude oil (68, 70, 72). Due to their potential toxicity and very high concentrations in crude oil, alkyl-PAHs are recognized as chemicals of concern in oil spill areas. Before the Hebei Spirit oil spill (HSOS) off the Taean (western) coast in 2007, alkylPAHs were not monitored regularly in South Korea. After the HSOS, the Korean Institute of Ocean Science & Technology (KIOST) initiated alkyl-PAHs impact assessments (72, 117). Concentrations of alkyl-PAHs in sediments contaminated by oil spills are generally two to three orders of magnitude greater than those of parent PAHs (67). The distribution of alkyl homologues depends on the degree of alkylation during weathering, and might be used to assess oil weathering in local environments (118). Very high concentrations of alkyl-PAHs were found in sediments from both intertidal and subtidal areas following the HSOS (72, 117) (Figure 9). Sedimentary alkyl-PAH levels then decreased continuously in most coastal areas, reaching background levels within three to five years of the HSOS, a timeline that was relatively slow compared to trends observed in seawater, porewater, and organisms. High concentrations of crude-derived hydrocarbons, including alkyl-PAHs, remained long-term in some hotspot areas (67, 71, 117), such as the inner parts of small bays and mud-dominant regions, possibly due to a lack of flushing under low-energy conditions. Residual oil persisted in such sediments, where it could have long-term adverse effects on living organisms for many years. Sediment quality criteria for protection of marine wildlife in oil spill areas remains limited worldwide and comprehensive sediment quality guidelines for crude oil-derived PTSs still need to be established.

NPs NPs are degradation products of nonylphenol ethoxylates (NPEOs), which are used as detergents, wetting agents, dispersing agents, and emulsifiers in various industrial, domestic, and household applications (119). NPs and NPEOs have been recognized as endocrine disrupting chemicals that can cause estrogenic effects in marine organisms (119). In South Korea, the most common uses for NPs have been household detergents and cleaning agents (60%), followed by paint and epoxy resin manufacture (12%), copper laminates (9%), ink binders (5%), agricultural pesticides (2%), and other uses (12%) (120).



Figure 9. Distributions of alkyl-PAHs in sediments of Korean coastal waters. (Data sources: (63, 67–72)). NPs have been studied more than most other PTSs in coastal sediments. Previous studies suggested that sewage and wastewater from industrial complexes and cities were major sources of NPs in coastal environments (27). NPs have been found to be widely distributed in sediments of Korean coastal waters, with the greatest concentrations being found in the inland creeks of Lake Sihwa (0.2–31,700 ng g-1 dw) in 2000 (80), Yeongil Bay (4.9–14,540 ng g-1 dw) in 174 Loganathan et al.; Persistent Organic Chemicals in the Environment: Status and Trends in the Pacific Basin Countries I ... ACS Symposium Series; American Chemical Society: Washington, DC, 2016.


2010 (78), and Masan Bay (113–3,890 ng g-1 dw) in 2000 (45) (Figure 10). Concentrations of NPs in some sediments exceeded the Interim Sediment Quality Guidelines of the CCME (107), raising concerns for their potential adverse effects on marine organisms. Temporal trends for NPs in sediments indicate a gradual decrease [e.g., Lake Shihwa (46, 77, 80); Masan Bay (17, 27, 45, 76, 79)] following recent actions, such NP bans and expansion of wastewater treatment plants (120). More monitoring studies should be carried out to establish local sediment quality guidelines for regulating NPs in South Korea. BTs BTs, which include tributyltin (TBT) and its metabolites, are well-known PTSs that can impact marine life and persist in sediments for long periods of time (93). Concerns about TBT, an organotin compound used as a biocidal additive in antifouling paints on ship hulls, were raised based on reports of it having adverse effects on marine organisms in the 1980s (97). Due to BT toxicity for marine organisms, TBT use in antifouling agents has been restricted in many countries since the 1980s (93, 121). In South Korea, TBT use was prohibited for small ships (

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