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Article

Distribution Characteristics and Pollution Sources Analysis of Polycyclic Aromatic Hydrocarbons and Phthalate Esters in the Seawater of Land-Based Outlets around Zhanjiang Bay in Spring

by
Zhifeng Wang
1,
Hui Zhao
1,2,3,4,* and
Lirong Zhao
1,*
1
College of Chemistry and Environmental Science, Guangdong Ocean University, Zhanjiang 524088, China
2
Southern Marine Science and Engineering Guangdong Laboratory, Zhuhai 519082, China
3
Research Center for Coastal Environmental Protection and Ecological Resilience, Guangdong Ocean University, Zhanjiang 524088, China
4
Cooperative Research Center for Offshore Marine Environmental Change, Guangdong Ocean University, Zhanjiang 524088, China
*
Authors to whom correspondence should be addressed.
Water 2024, 16(7), 948; https://doi.org/10.3390/w16070948
Submission received: 30 January 2024 / Revised: 15 March 2024 / Accepted: 17 March 2024 / Published: 25 March 2024
(This article belongs to the Special Issue Water Environment Pollution and Control, Volume III)
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Abstract

:
This study analyzed the distribution characteristics and sources of pollutants in the coastal estuaries of Zhanjiang Bay (ZJB) to provide theoretical and data support for the scientific prevention and control of bay pollution. Monitoring data from eight rivers and flood drains flowing into ZJB in March 2021 were used to analyze the composition and spatial distribution characteristics of polycyclic aromatic hydrocarbons (PAHs) and phthalate esters (PAEs) in the water bodies of the bay. The dominant components in the eight rivers and flood drains were 3–4-ring PAHs, with Bis (2-ethylhexyl) phthalate (DEHP), Diisobutyl phthalate (DIBP), and Dibutyl-O-phthalate (DBP) being the main PAE compounds. Higher pollutant levels were observed in residential areas, aquaculture zones, and industrial areas. Eigen-ratio analysis and principal component analysis were used to identify pollution sources, including atmospheric inputs (coal, petroleum products, biomass combustion products), offshore petroleum pollution, and plastic pollution sources. The assessment showed that atmospheric inputs contributed to 89.75% of the total PAHs in the bay, with coal and biomass combustion accounting for 62.12% and petroleum fuel combustion accounting for 27.63%. The content of ΣPAEs ranged from 588.43 to 1427.26 ng·L−1, with a mean value of 906.59 ng·L−1, which is at a low to medium level compared to other regions of China and abroad, indicating a medium-low level of pollution risk. The results of this study have important implications for guiding urban development, adjusting energy consumption structures, and planning pollution prevention and control measures in ZJB.

1. Introduction

Identifying pollution sources is crucial for effective pollution prevention and control. Molecular markers, such as polycyclic aromatic hydrocarbons (PAHs) and phthalate esters (PAEs), are commonly used for this purpose [1,2,3,4]. PAHs are compounds consisting of two or more benzene rings and are primarily emitted by human activities. They are widespread in rivers, the atmosphere, soil and marine environment [4,5,6]. Different PAHs have distinct molecular characteristics, allowing for the determination of their source or origin based on their composition in environmental media [4,5]. PAHs are commonly used to identify emission sources, such as petroleum product leakage, petroleum fuel combustion, coal combustion, and biomass combustion. On the other hand, PAEs are the main plasticizers and softeners used in the plastic industry. They are found in various products including toys, household goods, building materials, agricultural materials, and packaging [7,8]. Di (2-ethylhexyl) phthalate (DEHP), Diisobutyl phthalate (DIBP) and Dibutyl phthalate (DBP) are the most widely used PAEs plasticizers, with DEHP accounting for approximately 80% of China’s total PAEs production [9,10]. PAEs are released as plastic products age and decompose into microplastics in the environment, making them useful for analyzing plastic or microplastic pollution [7,11]. Microplastic pollution has become a major focus in marine pollution research, and Zhanjiang Bay (ZJB) has attracted attention due to the extensive use of plastic products in aquaculture [12].
Bays are often major sites of terrestrial PAH and PAE pollutants. The contribution and characteristics of PAH emission sources are closely related to the economic development level and energy consumption structure in coastal areas. Studies have shown that PAHs dominant in water bodies in various coastal areas are mostly 2–4 ring PAHs, primarily derived from coal and biomass combustion, fossil fuels, and introduced through atmospheric deposition, urban sewage and shipping activities [13,14,15,16]. PAEs have been detected in many coastal waters in China, including the Yangtze River Estuary, the East China Sea, the Pearl River estuary, and Jiaozhou Bay, with DEHP, DIBP, with DBP being the most prevalent [17,18,19,20].
ZJB is a typical tropical bay located near Zhanjiang City in South China. It is home to major petrochemical and steel enterprises, ports, docks, tidal flats, and mariculture areas. The bay is affected by the discharge of domestic sewage, industrial wastewater, aquaculture tail water, dry/wet deposition of combustion products, surface runoff, offshore oil pollution, and aquaculture activities. As a result, the water quality of ZJB has not been of a good standard for a long time, falling into the inferior four types of seawater classification in GB 3097-1997 [21] and becoming the focus of pollution prevention and control in the coastal waters of Zhanjiang City. Hitherto, there have been limited systematic studies on the source and concentration of organic pollutants in the estuaries of ZJB. This study aims to analyze the pollutant composition in the rivers and flood discharge estuaries of ZJB using observation data from eight rivers and flood discharge channels in the spring of 2021. Principal component analysis and eigenvalue analysis will be employed to determine the contribution and source of various pollutants. The findings will provide essential insights for environmental protection and pollution prevention in ZJB.

2. Materials and Methods

2.1. Sample Collection

In this study, surface seawater samples were collected from the estuaries of 8 major rivers or flood discharge channels in ZJB in March 2021 (Figure 1). The sampling sites (S1–S8) were affected by residential areas, industrial zones, and aquaculture activities. Among them, S1–S3 were located at the north bank of Zhanjiang Donghai Island and were mainly affected by aquaculture wastewater discharge (S2 and S3 are situated in the same river, which is used for reservoir aquaculture flooding. The purpose of this is to test the internal and external pollution of the floodgates). S4 is at the estuary of the Nanliu River, located in the petrochemical industrial area, surrounded by the petrochemical wharf. S5 is at the Lvtang estuary in the urban residential area, a sewage estuary. S6 and S8 are in municipal sewers, and S7 is at the mouth of the largest river into ZJB, the Suixi River. Portable samplers were used to collect approximately 1.2 L of water samples, which were then stored in glass bottles with the addition of approximately 5 mL of methanol. The samples were stored in a refrigerator at 4 °C until further analysis. The oil content of the samples was determined using n-hexane liquid-liquid extraction/ultraviolet spectrophotometry according to the ‘Marine Monitoring Specification 2007’.

2.2. Sample Extraction and Analysis

The samples were pretreated by solid phase extraction. Water samples (approximately 1.0 L) were filtered through a glass fiber filter (Whatman GF/F, 0.7 μm, Ф47 mm, GE Healthcare UK Limited, Little Chalfont, Buckinghamshire, UK) and extracted following a solid-phase extraction procedure using the Envi-C18 cartridge (SUPELCO,1 g/6 mL, Sigma-Aldrich, St. Louis, MO, USA). The cartridge was activated by adding 4 times 6 mL of n-hexane, 4 times 6 mL of dichloromethane, 4 times 6 mL of methanol, and 1 times 6 mL of water in the order. The filtered sample was spiked with the 5 PAH surrogate standards (100 ng), DIBP-d4 surrogate standard (400 ng), DEHP-d4 surrogate standard (500 ng), and isopropanol as a modifier. The recovery indicator concentrations of 5 PAHs, DIBP-d4 and DEHP-d4 in water samples were 100 ng·L−1, 400 ng·L−1 and 500 ng·L−1, respectively. The cartridge was connected to the water sample and vacuum water circulating pump using a micro-extraction tube, and it was then passed through the cartridge. The average flow rate of sample loading was maintained at 10 mL·min−1. After the water sample was extracted, the cartridge was naturally eluted with 2 mL acetone and 8 mL dichloromethane, respectively. The eluent was dehydrated with anhydrous sodium sulfate and concentrated to about 3 mL though natural volatilization. It was then replaced with n-hexane and further concentrated to about 0.4 mL though natural volatilization. A mixture of 100 μL of 3 PAH (p-Terpheny1-d14, BaP-d12 and DahA-d14) and 1 PAE (DPP-d4) internal standard substance was added to the concentrated sample and diluted to 0.5 mL with n-hexane to test. The final concentration of the PAH internal standard and PAE internal standard in each sample was 600 ng·mL−1 and 1600 ng·mL−1, respectively.
The samples were tested using gas chromatography/triple quadrupole mass spectrometry (Trace GC Ultra & TSQ Quantum XLS, Thermo Fisher, Waltham, MA, USA) for qualitative and quantitative analysis. The chromatographic column used was HP-5 ms (30 mm × 0.25 mm × 0.25 μm). PAHs and PAEs were detected simultaneously. The mass spectrometry mode for PAHs was selective reaction monitoring (SRM), while for PAEs it was selective ion monitoring (SIM). The temperature program for analysis consisted of an initial temperature of 70 °C for 2 min, followed by an increase to 290 °C at a rate of 5 °C/min for 10 min. The inlet temperature was maintained at 290 °C, and the EI source temperature was set to 250 °C. The retention time (RT) and m/z value of the target compounds were determined to be 54 min and 1, respectively. A standard sample chromatogram is shown in Figure 2 and the retention time of each analyte is shown in Table 1.

2.3. Quality Assurance and Control

In this study, to minimize potential contamination during sample handling and ensure data accuracy, all operations were subjected to strict quality control procedures. A procedure blank was used to determine potential contamination for each test. This showed that low concentrations of some PAHs and PAEs were detected, which were then appropriately subtracted from the sample extracts when they were higher than the method detection limit (MDL). The recovery rate was based on 60–120% of the recovery rate of surrogate standards in the US national standard method [22,23]. The average surrogate recoveries of 4 PAHs (acenaphthene-d10, phenanthrene-d10, phenanthrene-d12 and perylene-d12) and 2 PAEs (DIBP-d4 and DEHP-d4) ranged from 56% to 102% for water samples at river estuaries and sewage outlets, except for naphthalene-d8, which exhibited a low recovery rate and was not considered. The MDL of PAHs and PAEs were estimated as being three times the standard deviation of the field blanks or the corresponding amount of analyte that would generate a 10:1 signal-to-noise ratio, which was approximately 0.10–0.40 ng·L−1 and 0.20–1.00 ng·L−1 in this study. Data analysis was performed using SPSS 26.0, Origin 9.5, and ArcGIS 10.4 software.
The 15 PAHs compounds analyzed in this study were Acenaphthylene (Acy), Acenaphthene (Ace), Fluorene (Flu), Phenanthrene (Phe), Anthracene (Ant), Fluoranthene (Fla), Pyrene (Pyr), Benzo (a) anthracene (BaA), Chrysene (Chr), Benzo (b) fluoranthene (BbF), Benzo (k) fluoranthene (BkF), Benzo (a) pyrene (BaP), Indeno (1,2,3-cd) pyrene (IcdP), Dibenzo (a, h) anthracene (DahA), Benzo (ghi) perylene (BghiP). The 6 PAEs compounds were Dimethyl phthalate (DMP), Diethyl phthalate (DEP), Diisobutyl phthalate (DIBP), Dibutyl phthalate (DBP), Butyl benzyl phthalate (BBP), and Di (2-ethylhexyl) phthalate (DEHP).

2.4. Analysis of PAHs Characteristic Ratios and PAEs Index

The characteristic ratio method is a commonly used and well-established method for identifying pollution sources based on the relative content and composition of PAHs. The isomeric molecules of PAHs emit from different pollution sources and can be used to infer their causes or sources. For example, low-ring PAHs are primarily derived from the leakage of crude oil and its refined oil, as well as low-temperature pyrolysis processes. In contrast, high-ring PAHs are associated with high-temperature pyrolysis processes, such as the combustion of coal, biomass and petroleum fuels [24]. By analyzing the characteristic ratio of PAHs, such as the low-ring to high-ring PAH ratio (L/H), the source of PAHs can be determined. Additionally, the combined use of multiple PAH isomeric ratios can help identify multiple pollution sources [25].
As plasticizers and softeners, PAEs are widely used in the production and use of various plastic products, including toys, daily necessities, building materials, agricultural materials, and food packaging. As plastic products age and decompose in the natural environment, they release PAEs, which contribute to plastic pollution and microplastic formation. Therefore, analyzing the content of PAEs in the environment can provide insights into plastic pollution and microplastic pollution [9,11]. In this study, the content components of PAEs were used to assess plastic pollution in ZJB.

3. Results

3.1. Content and Distribution of PAHs and PAEs

The detection results of PAHs and PAEs in the water samples from the eight rivers or flood discharge channels in ZJB are presented in Table 1. 15 PAHs compounds were detected, with detection frequencies (DFs) reaching 100% for all compounds except BaA, BkF, BaP, IcdP, DahA and BghiP. The content of ΣPAHs ranged from 9.38 to 48.35 ng·L−1, with an mean value of 18.03 ng·L−1 and a relative standard deviation (RSD) of 66.7%. Among the six PAE compounds, the DFs of DMP and DEP were 62.5% and 37.5%, respectively, while the other compounds had 100% DFs. The content of ΣPAEs ranged from 588.43 to 1427.26 ng·L−1, with a mean value of 906.59 ng·L−1 and a RSD of 26.9%. The spatial distribution of ΣPAHs and ΣPAEs in different stations is shown in Figure 3. Among the eight stations, S5 had the highest ΣPAH content, followed by S4 and S3, while the differences between the other stations were relatively small. Regarding ΣPAEs, S4 had the highest ΣPAE content, followed by S3 and S2, with the difference between the other stations being relatively small.

3.2. Compositional Characteristics of PAHs and PAEs

Among the 15 PAHs compounds, Phe had the highest average content, followed by Flu, Fla, Pyr, Ant. The composition of 3–6-ring PAHs in each station is shown in Figure 4. The contents of 3-ring PAHs were the highest among the eight rivers and flood discharge channels of ZJB, with 3-ring accounting for 60.5–75.2% of ΣPAHs, four-ring PAHs accounting for 21.5–33.6%, and 5–6-ring PAHs accounted for 1.1–15.0%. Among the six PAE compounds, DIBP, DBP, and DEHP were the main components, accounting for 28.4%, 19.9%, and 51.0% of the total PAEs, respectively, totaling 99.3%. Regarding the eight stations of PAEs, DEHP accounted for 43.7–62.7% of ΣPAEs, DIBP accounted for 21.7–36.8%, while DBP accounted for 14.1–27.2%. In general, 3–4-ring PAHs were the dominant components of PAHs, while DEHP was the most abundant PAE compound. The concentration of the three main PAEs was in the following order: DEHP > DIBP > DBP, with DEHP being the most abundant.

3.3. Source Identification of PAHs and Principal Component Analysis

Characteristic ratios are commonly used to identify the source of PAHs. For example, a value of Ant/(Ant + Phe) < 0.1 indicates the petroleum sources, while a value >0.1 indicates the combustion source. A value of Fla/(Fla + Pyr) < 0.4 indicates the oil source, a value of 0.4–0.5 indicates the fossil fuel combustion source, and a value >0.5 indicates the coal and biomass combustion source [26,27]. Figure 5A shows the characteristic ratio of PAHs. The results indicate that S5 associated with the oil source, while the other estuaries have Ant/(Ant + Phe) > 0.1, indicating the combustion source. Additionally, Fla/(Fla + Pyr) values in all stations were >0.5, indicating the source of coal and biomass combustion. Principal component analysis was employed to further explore the source and contribution of PAHs [26,27]. Figure 5B shows the principal component analysis of PAHs, with the two principal components explaining a total variance of 89.75% (PC1: 62.12%, PC2: 27.63%). PC1 was primarily composed of Acy, Ace, Flu, Phe, Ant, Fla, Pyr, BaA, Chr for 3–4-ring PAHs with high load values, indicating sources related to low-temperature combustion such as coal and wood [28]. PC2 was mainly composed of BaA, BbF, BkF, BaP, IcdP, DahA, and BghiP for high-ring PAHs with high load values, indicating high-temperature combustion of petrochemical fuels [29].

4. Discussion

4.1. Spatial Distribution Characteristics of Organic Pollutants

The distribution of PAHs and PAEs in the estuaries of ZJB is influenced by terrestrial input and other sources of pollution. The content of PAHs is highest near the densely populated central urban area, while PAEs show their highest contents in the aquaculture and industrial area near the middle of the bay. The dominant pollutants in the bay are 3–4-ring PAHs and 3-ring PAEs, indicating their close association with the energy consumption structure of fossil fuel, coal, and biomass combustion in Zhanjiang City [30,31]. The presence of DIBP, DBP and DEHP are closely related to the extensive use of plasticizers in production in the plastic industry [9,10]. For example, S5, located adjacent to the central city of Zhanjiang and the sea traffic terminals, exhibits the highest content of ΣPAHs, which can be attributed to the extensive use of engine fuel. S4, adjacent to the Nanliu River industrial area, shows the highest content of ΣPAEs, likely originating from industrial wastewater [30]. The content of other PAH monomer compounds, except for BbF, exhibit significant dispersion at different stations, indicating the influence of various pollution sources, such as the surrounding atmosphere and offshore oil sources. In addition, PAE pollution in the environment is associated with the production, use, and disposal of plastic products [12]. Wang et al. [32] reported no significant difference in the abundance of microplastics in ZJB. In general, the spatial distribution of PAE content is similar to the characteristics of microplastic pollution, indicating the widespread presence of plastic pollution or its contaminated wastewater discharge in ZJB, such as leachate from garbage dumps entering the bay through rainfall [11,33,34]. Yao et al. [35] also pointed out that plastic pollution is widespread in the coastal environment of ZJB (Table 2).
The contents of PAHs and PAEs in this study were compared with reported results from waters at home and abroad (Table 2). The findings showed that the concentrations of PAHs and PAEs in this study were relatively low. From a regional perspective, the pollution degree of PAHs in Zhanjiang Bay is much lower than that in Taiwan Salt Estuary [14] and the Yellow River Delta [16], which are known for having the highest PAH content in China and abroad. The pollution degree of PAEs in Zhanjiang Bay was higher than that in the Rhône River [42] but lower than other regions at home and abroad. Furthermore, the concentrations of PAHs in this study were significantly lower than the values reported by Ke et al. [31] and ranged from 685.8 to 1080.4 ng·L−1, with an average of 887.5 ng·L−1. This suggests that the input source of PAHs in Zhanjiang Bay has been effectively controlled by the Zhanjiang Municipal Government through various environmental pollution control measures in recent years [44,45].

4.2. Identification of Pollution Source Characteristics

4.2.1. Source of Air Pollution

The characteristic ratio and principal component analysis revealed that the PAHs in the estuarine water of ZJB were primarily derived from the combustion of coal, biomass, and petroleum fuel (in that order). These fuels are known to emit pollutants such as NOx, VOCs, and PM10 during combustion, making them significant sources of air pollution in Zhanjiang [46]. The environmental pollution control measures implemented during the 13th Five-Year Plan period, including the elimination of black and odorous water bodies and the renovation of sewage outlets, effectively controlled domestic sewage and industrial wastewater discharge into the sea [45]. However, the combustion of fossil fuels in Zhanjiang City remains a significant atmospheric pollution source, with the emitted pollutants being transported into the ocean through atmospheric dry/wet deposition and surface runoff, thereby becoming an important source of organic pollution in ZJB.
The dominant content of 3–4-ring PAHs in the study indicates that low temperature combustion of petroleum, coal, and biomass is widespread. Phe is the most abundant PAH and may come from direct emissions of gasoline engine or diesel engine fuel [47]. The combustion of coal, biomass, and petrochemical fuel had an important contribution to PAH pollution in ZJB, and the contribution rates were 62.12% and 27.63%, respectively. According to the statistics [48], the consumption of petroleum and its products in Zhanjiang has increased dramatically in recent years. The number of automobiles has increased from 31,299 in 2015 to 767,886 in 2020, and the emission of exhaust pollutants from mobile sources has generally shown an upward trend. Many large steel, oil refining and other large enterprises settled in Zhanjiang and went into production, resulting in a sharp increase in coal consumption from 4.08 million tons in 2010 to 12.2 million tons in 2020. Although biomass burning, such as straw, has been banned since 2014 in Zhanjiang City, the characteristic ratio and principal component analysis in this study indicates the continued presence of biomass burning in the area. Overall, atmospheric pollution sources have become one of the main input sources of PAH pollution in ZJB.

4.2.2. Source of Oil Pollution

Among the 15 PAHs, 3–4-ring PAHs were the main components, indicating that there was oil pollution in the study area. In the study, the oil content in water samples was determined. The results showed that the oil content ranged from 0.052 to 0.259 mg·L−1, which exceeded the 0.05 mg·L−1 of the Case 1 and Case 2 seawater quality standards. Among them, the oil content of S5 is 0.259 mg·L−1, and the characteristic ratio of PAHs shows that pollution at S5 is an oil source. The coastal areas of ZJB are densely distributed with port terminals, fishing terminals, safe havens, etc. For example, S5 of Lvtang River is not only located in the central urban area of Zhanjiang, but also near the wharf and a large number of ships. Oil pollution may come from domestic sewage, port terminal operations, ship berthing, marine traffic, and other oil seepage. According to statistics [48], in 2020, the number of motor ships in ZJB reached 198, and more than 200,000 ships entered, left and docked in ZJB. The port cargo throughput reached 233.91 million tons, and crude oil production and processing reached 5.16 million tons and 8.6 million tons, with processing further suggesting the presence of oil pollution sources in ZJB, as supported by the identification of PAHs pollution sources.

4.2.3. Source of Plastic Pollution

The sources of PAEs are complex and can originate from various sources, such as domestic sewage, plastic factories, and plastic products widely used in agricultural breeding processes [7,49,50,51]. Zhanjiang is well-known for aquaculture in China [12], and the extensive use of plastic products in aquaculture activities contributes to PAE pollution in ZJB. Plastic products used in aquaculture, such as fishing nets, foam floating plates, and packaging, can degrade into microplastics in the environment, releasing PAEs, which will enter the water body through rainwater erosion and become one of the sources of PAE pollution in ZJB. In this study, PAEs in S1–S3 had a high content, which may be related to the extensive use of plastic products in adjacent aquaculture areas. Chen et al. [12] also pointed out that microplastics in ZJB may come from polyethylene (PE), polypropylene (PP), expanded polystyrene (EPS), olefins and rubber. Different aquaculture activities have an impact on the species and abundance of microplastics in ZJB. Net cage farming is located in the middle of the bay, and plastic nets are the main source of microplastics in the region. DIBP, DBP and DEHP were the main PAEs compounds in this study, which also came from these plastic fragments [9,49,51]. Among them, DEHP is the most abundant PAE, and the proportion of DEHP in each station is the highest, which is consistent with the fact that DEHP is the most used PAE in China [9,10]. Apart from aquaculture activities, plastic pollution in ZJB is also associated with residential, industrial, and agricultural production activities. For instance, the highest PAE content at S4 may be attributed to manufacturing emissions in industrial areas, while the PAEs at S5 may originate from domestic sewage and solid waste in residential areas. According to relevant statistics [48], there are about 27 rubber and plastic products enterprises in the Zhanjiang area, with an annual production of 85,000 tons of plastic products, 411,700 tons of primary plastic products, and 2643 tons of agricultural plastic film. Zhang et al. [52] demonstrated that microplastics found on the beaches of ZJB Yugang Park can originate from plastic products such as polyethylene, polystyrene, polyvinyl chloride resin, and polypropylene. Therefore, the sources of PAEs in ZJB are likely derived from plastic products as well as the manufacturing processes of plastic products enterprises.

5. Conclusions

This study revealed that 3–4-ring PAHs and 3-ring PAEs (DEHP, DIBP and DBP) were the main pollutants in the estuaries of ZJB. The concentrations of PAHs and PAEs were relatively low compared to other regions. PAHs primarily originated from the combustion of coal, biomass, and petroleum fuel in sequence, while PAEs were likely derived from various sources, including aquaculture, plastic production, and domestic and industrial sewage. Air pollution, oil pollution, and plastic pollution were identified as significant sources of organic pollutants in ZJB. The findings highlight the importance of implementing effective pollution control measures to mitigate the impact of these pollutants on the bay ecosystem.

Author Contributions

Conceptualization, H.Z., L.Z. and Z.W. Methodology, L.Z. and Z.W. Software, Z.W. Validation L.Z. and Z.W. Formal analysis, H.Z., L.Z. and Z.W. Writing—original draft preparation, Z.W. and L.Z. Writing—review and editing, Z.W. and L.Z. Visualization, Z.W. Supervision, H.Z. and L.Z. Project management, H.Z. and L.Z. Funding acquisition, H.Z. and L.Z. All authors listed made a substantial, direct, and intellectual contribution to the work, and approved it for publication. All authors have read and agreed to the published version of the manuscript.

Funding

The present research is supported by the National Natural Science Foundation of China (No. 42076162) and the Science and Technology Special Project of Zhanjiang City (No. 2019B01009).

Data Availability Statement

Data is contained within the article.

Conflicts of Interest

The authors declare no conflicts of interest.

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Water 16 00948 g001
Figure 1. Sampling locations of ZJB.
Figure 1. Sampling locations of ZJB.
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Figure 2. Chromatogram of standard sample.
Figure 2. Chromatogram of standard sample.
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Figure 3. Concentration of ΣPAHs and ΣPAEs at each station.
Figure 3. Concentration of ΣPAHs and ΣPAEs at each station.
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Figure 4. Compositional patterns of PAHs and PAEs at each station.
Figure 4. Compositional patterns of PAHs and PAEs at each station.
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Figure 5. PAHs isomeric ratio and score plot of principal component analysis.
Figure 5. PAHs isomeric ratio and score plot of principal component analysis.
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Table 1. The content detection results and retention time of PAHs and PAEs for water samples at river estuaries and sewage outlets in ZJB.
Table 1. The content detection results and retention time of PAHs and PAEs for water samples at river estuaries and sewage outlets in ZJB.
ProjectPollutantRange (ng·L−1)Mean (ng·L−1)RSD (%)DF (%)RT (min)
PAHsAcy0.28~1.730.6763.110021.54
Ace0.28~2.650.8883.910022.27
Flu0.92~10.392.88101.010024.75
Phe3.77~19.677.2468.410029.12
Ant0.69~1.941.1040.210029.32
Fla1.08~5.612.2562.810034.66
Pyr0.81~3.941.6659.210035.63
BaAn.d.~0.400.13111.750.041.34
Chr0.32~1.070.5444.510041.52
BbF0.15~0.310.2227.010046.09
BkFn.d.~0.260.1382.937.546.19
BaPn.d.~0.270.1564.575.047.34
IcdPn.d.~0.270.05189.325.051.51
DahAn.d.~0.230.03264.612.551.66
BghiPn.d.~0.310.1192.862.552.42
ΣPAHs9.38~48.3518.0366.7
PAEsDMPn.d.~15.252.87167.562.521.63
DEPn.d.~3.290.84140.137.524.98
DIBP139.88~412.67257.7938.710030.84
DBP93.92~385.40180.2846.910032.70
BBP1.04~4.622.5147.710039.62
DEHP353.24~618.87462.3116.910042.70
ΣPAEs588.43~1427.26906.5926.9
Note: ‘n.d.’ means not detected. All the “n.d.” values were regarded as zero in the calculation of mean.
Table 2. Comparison of PAHs and PAEs concentrations in the water of different district in the world.
Table 2. Comparison of PAHs and PAEs concentrations in the water of different district in the world.
ProjectLocationSampling YearRange (ng·L−1)Mean
(ng·L−1)		KindsReferences
PAHsPearl River Estuary (China)201518.0–50.328.315[36]
Dalian Coastal Waters (China)2016–201716.0–115.049.015[37]
Salt River Estuary (China)2018–2019485.0–10,212.02292.516[14]
Sanniang Bay (China)201786.7–158.1106.716[15]
Yellow River Delta (China)2017113.0–1533.0496.016[16]
Moscow River (Russia)201350.6–120.175.87[38]
Tiber Estuary (Italy)2014–20151.75–607.590.516[39]
Zhanjiang Bay (China)20219.4–48.418.015This study
PAEsPearl River Delta (China)201413.0–6717.31159.614[19]
Bohai Sea (China)2015–20161670.0–22,400.04530.016[40]
Jiaozhou Bay (China)2015–20162240.0–12,600.05260.013[20]
Yangtze River Basin (China)2019–20201594.5–5155.5-15[41]
Rhône River (France)2017–201897.0–540.8314.27[42]
Tapao Canal (Thailand)20191440.0–12,080.04760.03[43]
Zhanjiang Bay (China)2021588.4–1427.3906.66This study
Note: ‘-’ means no data.
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Wang, Z.; Zhao, H.; Zhao, L. Distribution Characteristics and Pollution Sources Analysis of Polycyclic Aromatic Hydrocarbons and Phthalate Esters in the Seawater of Land-Based Outlets around Zhanjiang Bay in Spring. Water 2024, 16, 948. https://doi.org/10.3390/w16070948

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Wang Z, Zhao H, Zhao L. Distribution Characteristics and Pollution Sources Analysis of Polycyclic Aromatic Hydrocarbons and Phthalate Esters in the Seawater of Land-Based Outlets around Zhanjiang Bay in Spring. Water. 2024; 16(7):948. https://doi.org/10.3390/w16070948

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Wang, Zhifeng, Hui Zhao, and Lirong Zhao. 2024. "Distribution Characteristics and Pollution Sources Analysis of Polycyclic Aromatic Hydrocarbons and Phthalate Esters in the Seawater of Land-Based Outlets around Zhanjiang Bay in Spring" Water 16, no. 7: 948. https://doi.org/10.3390/w16070948

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