Seasonal and Temporal Inﬂuence on Polycyclic Aromatic Hydrocarbons in the Red Sea Coastal Water, Egypt

: This study investigated seasonal variation, spatial distribution, sources, composition and potential ecological risks of 16 polycyclic aromatic hydrocarbons (PAHs) in Red Sea coastal water. Surface seawater samples were collected at fourteen different locations. The sum of 16 PAHs concentrations in Red Sea showed clear variation between seasons, ranged from 1.08–6.10, 0.79–50.86, 1.37–54.47 and 0.21–7.18 µ g/L in summer, autumn, winter, and spring respectively. PAHs levels in Red Sea coastal waters were relatively high at certain sites during autumn and winter seasons. They could be classiﬁed as highly polluted by PAHs contaminants (>10 µ g/L). According to the diagnostic ratios measured, the majority of PAHs in this study originated from pyrogenic sources, while minor amounts originated from petrogenic sources. Four rings PAHs accounted for more than 64% of the total PAHs studied. PAHs pose a high ecological risk along the period of study, according to the ecological risk assessment by Risk quotients (RQNCs and RQMPCs).


Introduction
The Red Sea's coastal and marine resources contribute to Egypt's food, energy, oil (exploration and production), and tourism industry. In recent years, the quality and protection of natural ecosystems has become a major concern, especially in the coastal and marine areas, where growing population and anthropogenic activities have put a stress on a wide range of natural systems [1,2]. Tourism, shipping activities, oil extraction, harbours, and fishing practices are all examples of environmental threats to the Red Sea ecosystem [3][4][5][6].
A group of over 100 compounds with fused benzene rings is known as polycyclic aromatic hydrocarbons (PAHs) [7]. PAHs are contained in soot, smoke, boat shipping activities and exhausts generated by incomplete combustion of organic compounds such as petroleum [8]. PAHs are toxic, mutagenic, and carcinogenic. PAHs are considered as persistent organic pollutants (POPs) found in ecosystems, including coastal waters [9].
PAHs pollution in the aquatic ecosystem can be traced back to three different sources: pyrogenic, petrogenic, and diagenetic. High molecular weight PAHs dominate pyrogenic PAHs, as a result of incomplete combustion of organic material. Petrogenic PAHs are homologue series of PAHs that are found in petroleum products (e.g., refined and crude oil). Biogenic PAHs are formed in marine sediments at early stages of diagenesis or biological processes (e.g., perylene) [10][11][12]. PAHs are environmentally dangerous compounds especially those with 2-7 benzene rings. Based on their physical, chemical, and biological characteristics, PAHs are divided into two classes [13]. Low molecular weight (LMW)

Locations of Sampling
Seawater samples were collected seasonally from 14 sites along the Red Sea coast of Egypt during January, May, August, and November 2015 as described in Figure 1. Location of the stations was determined by the global positioning system (GPS) presented in Table 1.
To determine the effect of various pollution sources on the study area, coastal sites near potential pollution sources, harbours, marinas, shipyards, and shipping activities were chosen. Surface seawater samples (0-0.2 m) were collected manually in 1L brown glass bottles (methanol and hexane were used to wash it several times). To protect the samples from bacterial activity during transportation and storage, they were acidified to a pH of ≈ 2.0 by adding a few drops of %10 HCL. The samples were kept at 4 • C until analysis.

Chemicals
PAHs mixture standard (>99%) were purchased from Accustandard (New Haven, CT, USA). The solvents of hexane, methanol and dichloromethane were used for the extraction of hydrocarbons ≥ 99.9% purity, HPLC grade, Fisher Scientific Company (Hampton, NH, USA), Merck (Darmstadt, Germany) and Fluka (Buchs, Switzerland) respectively. Other chemicals were purchased from Kanto Chemical co. (Tokyo, Japan) and Merck (Darmstadt, Germany) and were of analytical grade. Na 2 SO 4 (analytical grade) was additionally activated before use at 400 • C for 6 h and then stored in sealed containers. SiO 2 and Al 2 O 3 were activated at 200 • C prior to use for 4 h. After that, 5% deionized water was added to partially deactivated.

Preparation and Extraction of Samples
Prior to extraction, surface seawater samples were filtered with a glass fiber filter (0.45 µm, Millipore, Burlington, MA, USA). The extraction of PAHs was carried out in accordance with method described by Parsons et al. 1984 [20]. Extracts was measured using gas chromatography-mass spectrometry (GC-MS, Shimadzu QP2010 ultra) technique.
After every five samples, procedural blanks were tested; no interferences were found in the blanks. Blank experiments were performed and used for the calculation of LODs. The detection limits ranged from 0.01 µg/L to 0.03 µg/L which includes 0.01 µg/L for naphthalene, acenaphthylene, fluorene, anthracene, fluoranthene and phenanthrene, 0.02 µg/L for acenaphthene, benzo [

Statistical Analysis
The findings were statistically analyzed using the SPSS 25 statistical package. The results of total PAHs in different sites and seasons are non-parametric because they were not normally distributed and non-homogeneous (p < 0.05). Therefore, Kruskal-Wallis one-way ANOVA on ranks (where normality test failed) and Mann-Whitney U test post hoc are used to assess statistical significance of differences. The Kolmogorov-Smirnov (K-S) and Levene-Smirnov (L-S) tests were used to determine normality and equal variance respectively.

Total PAHs Seasonal Variations and Patterns of Distribution
The total PAHs (∑PAHs) concentrations in surface seawater of the study area differ significantly in hot seasons (summer and spring seasons) from cool seasons (winter and autumn seasons). The levels of ∑PAHs in the summer season varied from 1.08 µg/L at station 11 to 6.10 µg/L at station 4 with mean value of 3.16 µg/L ' Table 2'. While in autumn season, concentrations of ∑PAHs ranged from 0.79 µg/L at station 10 to 50.86 µg/L at station 8 with mean value 7.32 µg/L. Whereas in winter season, concentrations of ∑PAHs ranged from 1.37 µg/L at station 14 to 54.47 µg/L at station 13 with mean value 20.88 µg/L. The concentrations of ∑PAHs in the spring season ranged from 0.21 µg/L at station 4 to 7.18 µg/L at station 7 with mean value 2.12 µg/L ( Figure 2).     As shown at station 4, the summer season has a comparatively high percentage of PAHs (marine sport club, Hurghada) (6.10 µg/L). This site has popular jetties for tourists where boating activities are likely to contribute significantly to the ∑PAHs levels found in the area of study-particularly when there is a petroleum leak or sloppy engine oil disposal from boats and ferries. In addition, concentrations of PAHs in station 7 (Safaga shipyard) (5.97 µg/L) were in dockyards and where shipping maintenance work takes places, which could contribute to ∑PAHs in the seawater. During the autumn season, the level of PAHs was highest in station 8 (50.86 µg/L), followed by station 7 (14.19 µg/L), and station 9 (10.85 µg/L). These sites have intense shipping activities, which may contribute to PAHs in the seawater of the area of study.
In the winter season, high concentrations of ∑PAHs were observed at station 13 (marina Marsa Alam) (54.47 µg/L) which is the main touristic port for Marsa Alam area, station 7 (Safaga shipyard) (51.52 µg/L), station 8 (adjacent to Abou Tartour harbour, Safaga) (48.18 µg/L), station 9 (fishermen valley, safaga) (31.82 µg/L) and station 1 (near oil company, Ras Gharieb) (22.20 µg/L). At station 7 (Safaga shipyard) (7.18 µg/L), a rather high concentration of PAHs in seawater was recorded throughout the spring season. Additionally, the total concentration of PAHs at stations (7, 8 and 9) during the autumn season and stations (1, 2, 3, 7, 8, 9, 11, 12 and 13) during the winter season were higher than the maximum permissible concentrations of 10 µg/L, indicating that certain species, especially fish, in these locations were likely exposed to PAHs during their lifetime. Our findings agreed with previous research indicating that PAH concentrations is generally related to seasonal variations, with lower PAH concentrations observed during the summer and higher concentrations observed during the winter [22,23]. References [23,24] observed that decreasing concentrations in the summer may be due to increased degradation caused by higher seawater temperatures, which influences the rate at which PAHs are degraded by microorganisms, or higher photo-oxidation. When the lower molecular weight PAHs are more than the larger molecular weight, PAHs do not have a very high acute toxicity to aquatic organisms [25]. By comparing our results with internationally permissible levels [26], we find that the total PAH levels at all stations are significantly higher than the European Union's maximum allowable concentrations of 0.20 µg/L and the US Environmental Quality Criteria, ΣPAHs = 0.030 µg/L, for conservation of human aquatic life consumers [27,28]. Figure 3 shows the PAHs composition pattern by  (1, 2, 7, 8, 9, 11, 12 and 13) in the winter season had four-ring PAHs concentrations that were higher than the maximum allowable concentrations10 µg/L. During the summer season, the most commonly detected PAHs in samples were Chrysene (31.56%), Benzo  Table 3'.    The mean concentration of individual PAHs, including carcinogenic and noncarcinogenic PAHs, in all samples ranged from ND to 1.00 µg/L, ND to 2.68 µg/L, ND to 8.04 µg/L, and ND to 2.18 µg/L, over the summer, autumn, winter, and spring seasons, respectively. Individual PAHs levels are either within or beyond the European Water Framework Directive's (WFD) Annual Average Environmental Quality Standards (AA-EQS), which indicate that the permissible range for PAHs is 0.002 to 2.4 µg/L [29].
The results obtained by using non-parametric Kruskal-Wallis' test (K-W) were found no significant differences (p > 0.05) among stations studied, whereas significant differences (p < 0.01) were found among four seasons. The seasonal average concentrations of total PAHs were higher in winter and autumn seasons compared to the other seasons. By using Mann-Whitney U test post hoc for non-parametric results that exhibit significant difference between the winter season and (summer, autumn and spring season, respectively) with P value (0.000, 0.002 and 0.000, respectively), no significant difference was found between (spring and summer), (summer and autumn), and (autumn and spring) (p =0.178; p = 0.87; p = 0.125), respectively. Seasonal variation of TPAHs values for stations, represented in form of box-whisker plots Figure 4. In different seasons, the total PAHs concentrations in surface seawater of the study area were in the decreasing order as: winter > autumn > summer > spring (Figure 4). These concentrations are comparable to those observed in other parts of the world as shown in Table 4. Direct comparison of data in the literature regarding PAHs were somewhat difficult due to differences in the analytical methods, representative samples, yearly seasons, and detected PAH components. It was found that the mean total PAH concentrations observed in the current study were greater than those found in Alexandria coast, Egypt [30], Venice Lagoon, Italy [31], Dalian coast, China in winter and summer seasons [32], Suez Canal, Egypt in all seasons [33], Thane creek, India [34], Shandong coastal area, China [35], Persian Gulf, Iran [36], Pearl River estuary, China [37], and Gulf of Trieste, Northern Adriatica Slovenia [38] due to the increase of the coastal anthropogenic activities in the study area compared to these areas previously mentioned. Our results, on the other hand, were lower than those from Egypt's Red Sea Coasts [39], Alexandria coast, Egypt [40], Suez Gulf, Egypt [25], Langkawi Island, Malaysia [41], and Coastal Area of Suez Gulf, Egypt [42].  The mean concentration of individual PAHs, including carcinogenic and noncarcino genic PAHs, in all samples ranged from ND to 1.00 μg/L, ND to 2.68 μg/L, ND to 8.0 μg/L, and ND to 2.18 μg/L, over the summer, autumn, winter, and spring seasons, respec tively. Individual PAHs levels are either within or beyond the European Water Frame work Directive's (WFD) Annual Average Environmental Quality Standards (AA-EQS which indicate that the permissible range for PAHs is 0.002 to 2.4 µ g/L [29]. The results obtained by using non-parametric Kruskal-Wallis' test (K-W) wer found no significant differences (p > 0.05) among stations studied, whereas significant di ferences (p < 0.01) were found among four seasons. The seasonal average concentration of total PAHs were higher in winter and autumn seasons compared to the other season By using Mann-Whitney U test post hoc for non-parametric results that exhibit signif cant difference between the winter season and (summer, autumn and spring season, re spectively) with P value (0.000, 0.002 and 0.000, respectively), no significant difference wa found between (spring and summer), (summer and autumn), and (autumn and spring) ( =0.178; p = 0.87; p = 0.125), respectively. Seasonal variation of TPAHs values for station represented in form of box-whisker plots Figure 4. In different seasons, the total PAH concentrations in surface seawater of the study area were in the decreasing order as: win ter > autumn > summer > spring ( Figure 4). These concentrations are comparable to those observed in other parts of the world a shown in Table 4. Direct comparison of data in the literature regarding PAHs were some what difficult due to differences in the analytical methods, representative samples, yearl seasons, and detected PAH components. It was found that the mean total PAH concen trations observed in the current study were greater than those found in Alexandria coas Egypt [30], Venice Lagoon, Italy [31], Dalian coast, China in winter and summer season [32], Suez Canal, Egypt in all seasons [33], Thane creek, India [34], Shandong coastal area China [35], Persian Gulf, Iran [36], Pearl River estuary, China [37], and Gulf of Triest Northern Adriatica Slovenia [38] due to the increase of the coastal anthropogenic activitie in the study area compared to these areas previously mentioned. Our results, on the othe hand, were lower than those from Egypt's Red Sea Coasts [39], Alexandria coast, Egyp [40], Suez Gulf, Egypt [25], Langkawi Island, Malaysia [41], and Coastal Area of Suez Gul Egypt [42].

Composition of PAHs
PAHs are usually found in complex mixtures rather than as individual compounds. Compounds with four or more rings that are generated by high-temperature combustion processes are known as high-molecular-weight PAHs (HMW-PAHs) [43,44]. Four rings of PAHs (FIu, Pyr, BaA, and Chr), five rings (BbF, BkF, BaP, and DahA), and six rings (IP, BP) were dominated by high-molecular-weight PAHs, representing the range of 83.54-96.43%, 79.81-99.72%, 67.95-98.53%, and 38.80-100% of the total values of PAHs in the summer, autumn, winter and spring seasons, respectively which are most likely the result of anthropogenic activities [45] including incomplete combustion of fuel in ships and vehicle engines ' Table 5'. Whereas the concentration of the total fossil polycyclic aromatic hydrocarbons (ΣTFPAHs) or LMW-PAHs (low molecular weight PAHs) are comprised of two rings (Nap) and three rings (Ac, Ace, Ant, F, and Phe) ranging from 3.57-16.46%, 0.28-20.19%, 1.47-32.05% and zero-61.20% of the total PAHs concentrations, in the summer, Sustainability 2021, 13, 11906 9 of 18 autumn, winter, and spring season, respectively. The contamination pattern of PAHs was in the sequence of four rings > 2 + 3 rings > 6 rings > 5 rings of the 16 PAHs based on ring number detected in the autumn and winter season. Whilst, decreasing in the order as following: 4 rings > 5 rings > 2 + 3 rings > 6 rings and that 4 rings > 2 + 3 rings > 5 rings > 6 rings in the summer and spring, respectively. The most abundant 4-rings compounds of (Chr, BaA, Pyr, and FIu), were present in all seasons' samples.
In the summer, autumn, winter, and spring seasons, benzo[a] anthracene (BaA), a potential carcinogenic pollutant, was found in all samples, with concentrations ranging from 0.41 to 1.02 µg/L (average of 0.5 µg/L), 0.16 to 2.48 µg/L (average of 0.71 µg/L), 0.23 to 6.68 µg/L (average of 2.32 µg/L) and ND to 0.8 µg/L (average of 0.27 µg/L), respectively. In different seasons, the mean level of BaA was greater than the EPA National Recommended Water Quality Criteria for the conservation of aquatic Life (0.010 µg/L), which could have an ecological impact in these areas [28].
The highest average level of individual PAHs measured in seawater samples was chrysene (1.00, 1.92, 8.04 and 1.31 µg/L) in the summer, autumn, winter and spring season, respectively. This high chrysene concentration may be due to its low water solubility, which allows it to be adsorbed onto particulate matter's surface, and also its high resistance to degradation. Our findings agree with those of [48], who discovered that the amount of chrysene did not shift significantly after 12 years of oil spill, suggesting the chrysene is difficult to degrade by to the aquatic ecosystem than other compounds. Fluoranthene and Benz(a)anthracene are two typical tetracyclic polycyclic aromatic hydrocarbons that are difficult to degrade [49]. In the summer and spring seasons, respectively, benzo[a]anthracene, which has the fingerprint of fossil fuels, was found to have the second highest mean concentration for individual PAHs (0.19 and 0.27 µg/L). During the autumn and winter seasons, fluoranthene (Flu) had the second highest mean concentration of individual PAHs (2.68 and 4.06 µg/L, respectively).
As presented in Figure 5, HMW-PAHs with four rings are predominated (65.92%, 87.64%, 79.68% and 79.64% of the total PAHs in the summer, autumn, winter, and spring season, respectively. In the summer, autumn, winter, and spring seasons, PAHs with three rings accounted for 4.89%, 1.02%, 5.94% and 4.05% of total PAHs, respectively. While, in the summer, autumn, winter, and spring seasons, the PAHs with the two rings accounted for 2.75%, 1.17%, 0.6% and 3.63% of the overall PAHs in the samples analyzed, respectively. Whereas the PAHs with the five rings were reported 16.49%, 5.09%, 6.77% and 12.90% of the total PAHs in the studied samples in the summer, autumn, winter, and spring season, respectively. Finally, the PAHs with the six rings accounted for 9.97%, 5.08%, 7.01% and 0.00% of the overall PAHs in the studied samples in the summer, autumn, winter, and spring season, respectively. The total PAHs in the samples studied may have come from a pyrogenic source, which could explain these findings. for 2.75%, 1.17%, 0.6% and 3.63% of the overall PAHs in the samples analyzed tively. Whereas the PAHs with the five rings were reported 16.49%, 5.09%, 6.7 12.90% of the total PAHs in the studied samples in the summer, autumn, win spring season, respectively. Finally, the PAHs with the six rings accounted fo 5.08%, 7.01% and 0.00% of the overall PAHs in the studied samples in the summ tumn, winter, and spring season, respectively. The total PAHs in the samples stud have come from a pyrogenic source, which could explain these findings.

Identification of PAHs Sources
Many factors contribute to the difficulties in identifying PAHs sources, such as the possibility of multiple sources of pollution coexisting, as well as the transformation process of PAHs [50].
Seven molecular diagnostic ratios were employed to identify putative sources of PAHs in the study area, as indicated in Table 7. In the aquatic ecosystem, the ratio of low molecular weight to high molecular weight PAHs (LMW/HMW) is a measure of weathering. A high level of microbial degradation resistance is indicated by a lower value of this ratio [51].
Pyrogenic sources were found to be depleted in low molecular weight 2-3 rings PAHs (LMW) and enriched in high molecular weight 4-6 rings PAHs (HMW), resulting in LMW/HMW ratios of less than one. LMW-PAHs predominated in petrogenic sources such as light refined petroleum products or fuel oil with an LMW/HMW > 1 ratio [50,52,53]. The LMW/HMW ratios were less than one in all seasons, with the exception of station 4 in the spring, indicating that they derived from pyrogenic sources.
The potential sources of PAHs are measured by the pyrogenic index (PI), which is the ratio of LMW to HMW that is greater than one. The PI has some advantages over the PAHs isomers ratio for three reasons: first, any change in the ratio will accurately represent changes in LMW and HMW-PAHs; second, the PI provides greater precision with greater consistency and lower uncertainty; and third, natural weathering and biodegradation slightly alter the PI values [59].
To differentiate between pyrogenic and petrogenic origins, PAHs with molecular masses of 178 and 202 are widely used [50,57,58,60]. Previous researchers have used values of ratios as an example Flu/Pyr (M.wt = 202) and Phe/Ant (M.wt = 178) [50,57,58,61]. Since petroleum produces more phenanthrene than anthracene (a more thermodynamically stable tricyclic aromatic isomer) the Phe/Ant ratio is expected to be quite high in cases of petrogenic pollution with PAHs [50,60,62]. Budzinski et al.(1997) [57] noticed that Phe/Ant ratios larger than 10 suggested petrogenic inputs, while Phe/Ant ratios less than 10 were indicative of pyrolytic sources. Furthermore, Flu/Pyr values less than one indicated petrogenic origins, whereas values more than one were connected to a pyrolytic origin. The Phe/Ant ratios for all stations in all studied seasons is less than 10, this suggested a pyrolytic origin, with the exception of station 4 in the winter season. Fluoranthene/pyrene (Flu/pyr) rates reveal the source of PAHs. For the summer season, PAHs from stations (9, 11, 12, and 13) are mostly petrogenic, while the rest of the stations are mostly pyrolytic. For the autumn season, PAHs from stations (3, 4, 9, 12, and 13) are mostly petrogenic, while the rest of the samples are mostly pyrolytic. For the winter season, PAHs from station (2) are mostly petrogenic, whereas PAHs of stations (1, 5, 6, 8, 9, and 12) have mainly petrogenic origin while the rest of the stations have mainly pyrolytic origin for spring season, and the rest of the samples have Flu/Pyr >1 suggest pyrolytic origins.
Ant/(Ant + Phe), Flu/(Flu + Pyr), and BaA/(BaA + Chr) were also used in the current study for further linking PAHs composition to pollution sources [56]. A ratio of Ant/(Ant + Phe) less than 0.1 indicates petroleum origin, whereas a ratio larger than 0.1 suggests combustion dominance. The results indicate Ant /(Ant + phe) ratio > 0.1 values at stations 5 and 12 for the autumn and spring seasons respectively, while the majority of the samples showed low concentrations at both seasons. In both the summer and the winter seasons, the Ant/(Ant + Phe) ratio > 0.1, suggesting pyrogenic origin, with the exception of station (4) in the winter season.
With Flu/(Flu + Pyr) ratio less than 0.4 indicates petroleum combustion, and from 0.4 to 0.5 indicates fossil fuel combustion (crude oil and vehicle), while greater than 0.5 suggesting combustion of coal, wood and kerosene [56]. In this study, the Flu/(Flu + Pyr) ratio was greater than 0.5, indicating pyrolytic origin for the majority of locations along all seasons. Except for stations (11 and 12), stations (3, 4, 9 and 13) and station (2) with recorded Flu/(Flu + Pyr) ratios between 0.4 and 0.5 in summer, autumn, and winter seasons. This suggests petroleum combustion origin. In the summer, autumn, and spring seasons, the Flu/(Flu + Pyr) ratios for stations (9 and 13), station (12), and stations (1, 5, 6, 9 and 12) were all less than 0.4, indicating petroleum pollution.
A petrogenic source is indicated by a ΣCOMB/Σ16PAHs ratio of <0.3, a mixed source by a ratio of 0.3 to 0.7, and a high-temperature combustion source by a ratio of >0.7 [54]. In all seasons, the COMB/16PAHs ratio was >0.7, with the exception of station (4) in the spring season, which dropped within the range of mixed sources. This indicates that the PAHs sources in the study area came from combustion sources.

Risk Quotients (RQs)
Risk quotients (RQ) are frequently employed to assess the potential environmental impact of PAHs on aquatic organisms [63][64][65]. The risk levels posed by PAHs were determined using RQ as the following: Individual PAHs concentrations were referred to as C PAHs . The quality values are based on the concentrations of PAHs in seawater that are considered insignificant (NCs) and maximum permitted (MPCs) by [63]. As a result, RQNCs and RQMPCs can be described as: where C QV(NCs) and C QV(MPCs) were the quality values of PAHs in the medium's NCs and MPCs, respectively [66].
The risk classification of PAHs and mean PAHs' RQNC s and RQ MPCs in the investigated samples along the Red Sea coast during various seasons are shown in Table 8. The majority of measured individual PAHs had RQ(NCs) >1.0 in all seasons, indicating that the majority of individual PAHs in the study area were above moderate risk thresholds. RQ (MPCs) of (Naph, Ace, Acthy, F, Phe and Ant in all seasons) and (BaP in summer and autumn, IP in spring) were <1.0, while RQ (MPCs) of (Flu, Pyr, BaA Chr and BbF in all seasons, BaP in winter and spring seasons and IP in summer, autumn, and winter seasons) were >1.0. Individual PAHs posed a moderate to high ecological risk in the study area's seawater according to these findings. The RQ ΣPAHs (NCs) and the RQ ΣPAHs(MPCs) of the study area in different seasons are depicted in Figure 6. The RQ ΣPAHs (NCs) and RQ ΣPAHs (MPCs) indicate that ΣPAHs posed a high ecological risk to marine organisms in all seasons, with the exception of the spring season, where stations 4 and 14 posed a moderate risk. Finally, the ecological risk of PAHs in the study area's seawater has been contaminated, necessitating the implementation of appropriate control and remediation measures should be introduced.
The RQ (NCs) and RQ (MPCs) may be a more accurate indication than PAHs concentrations. Figure 7 demonstrates the composition of RQ (NCs) . The contributions of individual PAHs to RQ (NCs) were quite similar to their contributions to RQ (MPCs) . The ratio of RQ (NCs) of 4 -ring PAHs was found to be the key contributor to the ecological load in seawater in different seasons. In the summer season, the RQ (NCs) of 5-ring PAHs were the predominant ecosystem risk at stations (5, 7, 9 and 11), and in the winter and spring seasons, the RQ(NCs) of 5-ring PAHs were the primary ecosystem risk at station (7). The RQ(NCs) and RQ(MPCs) may be a more accurate indication than PAHs concentra tions. Figure 7 demonstrates the composition of RQ(NCs). The contributions of individua PAHs to RQ(NCs) were quite similar to their contributions to RQ(MPCs). The ratio of RQ(NC of 4 -ring PAHs was found to be the key contributor to the ecological load in seawater i different seasons. In the summer season, the RQ(NCs) of 5-ring PAHs were the predominan ecosystem risk at stations (5, 7, 9 and 11), and in the winter and spring seasons, th RQ(NCs) of 5-ring PAHs were the primary ecosystem risk at station (7).

Conclusions
This work investigated 16 PAHs in surface seawater along Egypt's Red Sea coast. At different sampling sites, the spatial distribution and species of PAHs differed significantly. According to the European Union's water standard, the levels of PAHs contamination along the Red Sea coast was higher than the maximum permissible PAHs concentrations (0.20 µg/L) in all samples and this may cause toxicity in certain species that are exposed. Benzo(a)pyrene (BaP) and Dibenzo(a, h)anthracene were not observed in all seasons, whereas HMW PAHs were prevalent in both. PAHs pollution along the Red Sea coast was primarily caused by pyrogenic sources linked to shipping and shipyards, according to the source identification. Individual PAHs pose a moderate to high ecological risk, according to RQNCs and RQMPCs, while the mean values of RQΣPAHs (NCs) and RQΣPAHs (MPCs) show that PAHs pose a high ecological risk in the majority of sites. The findings of this research are serve as useful baseline data for PAHs contamination in the area of study. Data Availability Statement: This study did not report any data.