Title:
A comparative study of chlorinated paraffins (CPs) in seawater and sediments between the Bohai
Sea, China and Seto Inland Sea, Japan.
PI: Jian Zhang
Affiliation: Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, YIC, CAS
Members: Jianhui Tang
Affiliation: Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, YIC, CAS
Members: Xinyu Guo
Affiliation: Ehime University Faculty member of LaMer
Aim:(1) To investigate the occurrence and distribution characteristics of CPs in the Seto Inland Sea.
(2) To compare the concentrations and compositional distributions of CPs between the Seto Inland
Sea and the Bohai Sea.
(3) To explore the possible sources of CPs in the Seto Inland Sea.
Procedure:(1) Participate a cruise in the Seto inland sea, and collect water and sediment samples;(2) Discussion with Prof. Xinyu Guo about the comparison of POPs in the Bohai Sea and Seto
Inland Sea.
Result:Introduction
CPs are complex mixtures of chlorinated n-paraffins with different carbon chain lengths anddegrees of chlorination (Li et al., 2021). According to the carbon chain length, CPs can be
subdivided into short-chain chlorinated paraffins (SCCPs, C10-C13), medium-chain chlorinatedparaffins (MCCPs, C14-C17) and long-chain chlorinated paraffins (LCCPs, C18-C30). Since the first
synthesis of CPs in the 1930s, they have good flame retardancy and electrical insulation, lowvolatility and high stability, and are inexpensive and readily available. CPs are used in flame
retardants, plasticizers, metal cutting fluids and other product (Tomy et al., 1998). China has been
producing CPs products since the 1950s and is currently the world's largest producer and a major
exporter (Glüge et al., 2016). Shandong Peninsula and Liaodong Peninsula are important CPs
producing areas in China. SCCPs are of particular interest to researchers because of their longdistance transport potential, persistence, bioaccumulation, high toxicity to aquatic organisms, andpossible carcinogenic effects in humans. In May 2017, the Stockholm Convention Persistent Organic
Pollutants Review Committee decided at its Eighth Conference of the Parties to list SCCPs in Annex
A as a new group of persistent organic pollutants to limit their production and emissions (Castro etal., 2019).
Affected by population use emissions and emissions from CPs production areas, there is a highlevel of CPs pollution in the rivers and atmosphere in the Bohai Rim region. As the most important
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sink for pollutants in the Bohai Rim region, a large amount of CPs pollutants enter the Bohai Sea.
The long-term existence in water bodies and sediments threatens the ecological environment of theBohai Sea and further causes health risks to humans through the enrichment of marine food webs.
In this study, we have carried out sample preparation and instrumental analysis on the surface
seawater samples of the Bohai Sea in April, August, and November-December 2018 (Fig. 1),
obtained experimental data, and preliminarily analyzed the concentrations and distribution ofSCCPs.

Fig.1 The samping sites of surface seawater in the Bohai Sea in 2018.
Influenced by global pandemic of COVID-19 and also due to the new policies for international
travelling in China and Japan, we cancelled the exchange and study plan at Ehime University inJapan in 2021. We were not able to participate a cruise in the Seto Inland Sea, so we did not collectwater and sediment samples from the Seto Inland Sea.
SCCPs Concentrations in Surface Seawater
Table 1 lists the concentrations of SCCPs in the surface seawater of the Bohai Sea at different
time periods. For ΣSCCPs, it was detected in all seawater samples. In the three time periods, thedetection rate of SCCPs in the dissolved phase was higher than 60%, and the detection rate in theparticulate phase was 100%. Overall, the concentrations of ΣSCCPs ranged from 20.47 ng/L to5751.97 ng/L (median concentration: 208.2 ng/L). Compared with other studies in China, theconcentrations of ΣSCCPs in the seawater of the Bohai Sea was lower than the concentrations ofΣSCCPs in the seawater of the Pearl River Estuary in southern China (270±66 ng/L) (Huang et al.,2019), and also lower than the concentrations of ΣSCCPs in the river system of Shanghai (278 ng/L)(Wang et al., 2019). But it was higher than the concentrations in the seawater of the East China Sea(122±73 ng/L) (Hu et al., 2021). SCCPs in the Bohai Sea are at a moderate pollution level in China.

2 / 5Table 1
Concentrations of SCCPs in the surface seawater of the Bohai Sea.

Dissolved-phase

Particulate-phase

SCCPs(ng/L)

SCCPs(ng/L)

detection rate

0.63

11

mean

35.1

252.03287.1341.19

531.09524.67

min

n.d.

20.47

20.47

max

145.162465.92465.9median

30.19

120.3

142.83detection rate

0.91

11

mean

628.36230.82859.181399.68529.241439.6

min

n.d.

37.76

61.26

max

5680.92

2560.395751.97

median

86.81

77.55

201.09detection rate

0.88

11

mean

113.69503.59617.28164.41502.23453.25

min

n.d.

34.35

64.75

max

533.981451.761478.24

median40.95

296.54566.31detection rate

0.8

1

1

mean

314.3

283.58597.87982.73534.641067.21

min

n.d.

20.47

20.47

max

5680.92

2560.395751.97

median

42.63

94.47

208.2

seawater
2018.04

standard
deviation

2018.08

standard
deviation

2018.1112

standard
deviation

total

standard
deviation

ΣSCCPs(ng/L)

Perspectives in future:
Since SCCPs were added as POPs by the Stockholm Convention, the production and use of
SCCPs were restricted worldwide (Castro et al., 2019), and the production of MCCPs and LCCPs as
substitutes increased (van Mourik et al., 2016). The chemical structure, environmental behavior andtoxicity of MCCPs are similar to those of SCCPs; some studies have found that MCCPs with achlorination degree of more than 46% are persistent and toxic; the production and application ofMCCPs may have similar side effects to the environment and biosphere as SCCPs, and bring about
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new environmental issues and health risks. Environmental impacts and potential endocrine
disrupting effects of MCCPs and LCCPs have been included in the EU priority list. However, thereis less information about the concentration levels of MCCPs and LCCPs in the environment
compared to SCCPs. SCCPs, MCCPs and LCCPs deserve equal attention in the environment.
At present, the most common analytical method for CPs is gas chromatography, mainly for
SCCPs and MCCPs (Gao et al., 2016). LCCPs have high melting and boiling points and are difficult
to volatilize, so it is difficult to analyze by gas chromatography (Koh et al., 2002). Some researchers
have established a method for simultaneous determination of SCCPs, MCCPs and LCCPs based onreversed ultahigh-pressure liquid chromatography (UPLC) coupled with chlorine-enhanced electron
spray ionization/atmospheric pressure ionization (ESI/API) quadrupole time-of-flight mass
spectrometer (QTOF-MS) (Li et al., 2017), the results are remarkable. This study expects the followup work to develop a CPs analysis method using high performance liquid chromatography to analyze
the concentration level and distribution of SCCPs, MCCPs and LCCPs in the Bohai Sea.
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