Study of the accumulation of Polychlorinated Biphenyls (PCBs) in Siganus rivulatus from Latakia city (Syria)

This research focused on determining the concentrations of some polychlorinated biphenyls (PCBs) in marine water and muscle tissue of a type of saltwater fish for human consumption ( Siganus rivulatus ), which were collected in the summer and winter of 2022 in two locations in Latakia city beach (Sports City - South Corniche) using gas chromatography technology GC/MS. The results of this study showed that these areas are affected by polychlorinated biphenyls, which shows the continuous arrival of these combinations into the marine environment as a result of tourism activities, urban construction, sewage channels for homes and restaurants, or movement through river waters that flow directly into these areas. The total concentrations of polychlorinated biphenyls (PCBs) in the water of the studied areas ranged between 22.1037 µg/l and 46.553 µg/l, with the highest value recorded in the South Corniche region during the summer, which was for the combination PCB-101 and amounted to 14.004 µg/l, in contrast the lowest value was recorded in In the Sports City area during the winter, the PCB-151 combination reached 0.0447 µg/l. The total concentrations of polychlorinated biphenyls in the muscle tissue of the studied fish ranged between 61.2154 µg/g and 67.9369 µg/g, with the highest value recorded in the Sports City area during the summer, which was for the combination PCB-199 and amounted to 40.44 µg/g, in contrast the lowest value was recorded. In the southern Corniche area during the winter, the combination PCB-138 reached 0.492 µg/g. The correlation association that was studied between the lengths of the studied fish and the total concentration of PCBs indicated the presence of a significant positive association, R = 0.78. This shows an increase in the concentration of PCBs with the age of the fish, which shows an activity in the arrival of these pollutants into the marine environment.


INTRODUCTION
The Mediterranean Sea is a semi-enclosed area that is particularly vulnerable to pollution, as it is considered a storehouse of persistent organic pollutants (POPs), in a water bath in an Ultrasonic device for 60 minutes at a temperature of 45 ⁰C.The mixture was then placed in a sifter at 4000 rpm for 5 minutes to separate the solvent from the precipitate, and this process was repeated twice (Rocco et al., 2008;Ozcan et al., 2009).
The solvent was concentrated using a rotary evaporator to 5ml.The sample was transferred to a clean tube, and the model was concentrated using a gentle stream of nitrogen to 1ml, and then it was ready for purification.

Separation and purification
The sample was prepared in a burette with a length of 7.6cm and an inner diameter of 1.3cm.The burette was filled from bottom to top with 1g of anhydrous sodium sulfate, 2g of activated silica, and 2g of activated silica modified with sulfuric acid.After that, 2g of anhydrous sodium sulfate was added.The multilayer silica column was washed with 20ml of n-hexane before use Nevado et al., (2010), after which the sample was introduced to the queue, and purification was performed.The final extract was then collected and evaporated using a gentle stream of nitrogen to concentrate the sample.The sample was then analyzed on a gas chromatograph (GC/MS).

Sample analysis
The samples (water -fish) were analyzed using gas chromatography (GC/MS) technology.A TRP-5 capillary column with a length of (30 m) and an inner diameter of (0.32 m) was used to separate the combinations.The flow of the mobile phase was 1 ml/min according to the system.The following thermal programming: 70 ℃ (1 min) 280 ℃ (10 min) The qualitative analysis process was carried out using the external standard solution method by comparing the retention times of sample combinations with the retention times of typical combinations of specific identity and concentration.Figure 1 shows the chromatogram of a mixture of polychlorinated biphenyls (PCBs).Area: The peak height of the combination in the sample.

Distribution of PCBs in water samples from the South Corniche area
Fifteen isomers of polychlorinated biphenyls (PCBs) were detected in the waters of this region.Table 1 shows the total concentration of polychlorinated biphenyls Ʃ PCBs in the waters of this region during the two seasons of the study.We find that the lowest value of the total concentration of PCBs was 23.05 µg/l during the winter, in contrast the highest value was 46.55 µg/l during the summer.The reason for the decrease in the value of the total concentration of PCBs  in the winter and its increase in the summer in this region may be due to the rise in human and tourist activities in the summer and the decrease of these activities in the winter, as both of them negatively affect water quality (Needham and Ghosh, 2019; Undeman et al., 2022).The total concentrations of PCBs varied between the summer and winter seasons, as their value increased in the summer and decreased in the winter.We also note that there is a clear difference in the distribution of PCBs during the two seasons of the study, especially compounds with low molecular weight, and this is attributed to the tendencies of these compounds become more soluble in marine waters in summer as a result of rising temperatures, as the solubility of low molecular weight PCBs increases with increasing temperature (Shiu et al., 1997).PCB-101 recorded the highest value of 14.004 µg/l in the summer, in contrast the lowest value was for PCB-151, which reached 0.095 µg/l in the summer, and in the winter, it went 0.0447 µg/l.The concentrations of combinations PCB-15, PCB-101, PCB-118, PCB-151, and PCB-199 were monitored only in the winter, in contrast the other combinations were below the detection limit (Figure 2).

Distribution of PCBs in water samples from the Sports City area
A mixture of polychlorinated biphenyls (PCBs) was detected in the water of this region.Table 2 shows the total concentration of polychlorinated biphenyls (Ʃ PCBs) in the water of this region during the two seasons of the study, where we find that the lowest value for the total concentration of Ʃ PCBs was 22.1037 µg/l during the winter, in contrast the highest value of total concentration was 28.044 µg/l during the summer.The reason for the decrease in the value of the total concentration of PCBs in the winter and its increase in the summer in this region may be due to the reduction of these activities in the winter in addition to the open nature of the area which is affected by solid sea currents (Swackhamer and Skoglund, 1993).Low water temperature also enhances the migration of these lipophilic pollutants to adhere to organic materials suspended in the aqueous phase (Swackhamer and Skoglund, 1993).

ANALYSIS ARTICLE | OPEN ACCESS
Discovery 59, e116d1357 (2023) 5 of 12  PCB-101 recorded the highest concentrations among the studied combinations, as its concentration reaching 11,441 µg/l during the summer, in contrast its concentration was 9.976 µg/l.The lowest value for the combination PCB-195 was recorded during the winter and amounted to 0.048 µg/l, in contrast its concentration during the summer was below the detection limit.The other minimum value for the combination PCB-151 was recorded during the summer and amounted to 0.0534 µg/l, in contrast its concentration was during the winter without limit of detection.The concentrations of combinations PCB-15, PCB-101, PCB-118, PCB-151, PCB-195, and PCB-199 were monitored only in the summer and winter.In contrast, the attention of other combinations was not observed because they were below the detection limit, (Figure 3).

Distribution of PCBs in fish samples from the South Corniche region
Fifteen isomers of polychlorinated biphenyls (PCBs) were detected in the Siganus rivulatus of this region.Table 3 shows the total concentration of polychlorinated biphenyls Ʃ PCBs in the Siganus rivulatus of this region during the two seasons of the study, where we find that the lowest value of the total concentration is for PCBs, it reached 61.2154 µg/g during the winter, in contrast the highest value of the total concentration for PCBs reached 62.916 µg/g during the summer.The total concentrations of PCBs in fish collected during the two seasons of the study converged, with a slight increase in their engagements during the summer, which shows the continued arrival of PCBs into the marine environment in this region and their accumulation in the muscle tissue of fish.An apparent accumulation of combinations containing a more significant number of chlorine atoms was observed in the fish studied due to their resistance to decomposition and metabolism and their unique system of distributing chlorine in their molecular structure (Bright et al., 1995).

Distribution of PCBs in fish samples from the Sports City area
Fifteen isomers of polychlorinated biphenyls (PCBs) were detected in Siganus rivulatus from this region.Table 4 shows the total concentration of polychlorinated biphenyls Ʃ PCBs in Siganus rivulatus from this region during the two seasons of the study, where we find that the lowest value for the total concentration is for PCBs, it reached 64.7086 µg/g during the winter, in contrast the highest value of the total concentration reached 67.9369 µg/g during the summer.We note that there is a diversity of combinations accumulated in Siganus rivulatus fish.We also note that combinations with larger molecular weights had higher concentrations in the studied fish.A decrease in the attention of most of the PCBs was observed during the summer and their clarity in the winter due to photo-oxidation processes and high temperatures in the summer season, which leads to increased rates of biodegradation by microorganisms such as fungi, bacteria, and germs (Bamforth and Singleton, 2005).Nd: not detected.
The concentrations of PCBs in the winter were relatively close to those attention in the summer.Figure 5 shows the attention of the isomers of PCBs, where PCB-199 recorded the highest value, reaching 40.44 µg/g, and it was during the summer.At the same time, it was the lowest value for the combination PCB-196 and went 0.819 µg/g during the summer.Concentrations of PCB-138, PCB-141, PCB-151, PCB-170, PCB-180, PCB-187, and PCB-194 were not monitored in the summer as they were below the detection limit.PCB-199 and PCB-209 recorded high concentrations in study seasons because these combinations contain a more significant number of substituted chlorine atoms and, therefore, have a significant molecular weight.This makes the ability of fish to metabolize these combinations weak, and thus, they remain accumulated in the muscle tissue of fish for a long time (Shaw, 1993).

Discussion
The results show that the distribution of polychlorinated biphenyls (PCBs) in the saltwater waters of the coast of Latakia appears clearly throughout the studied areas.This shows the continuous arrival of these combinations into the marine environment through several sources, including sewage channels, tourism activities, and agricultural activities (Needham and Ghosh, 2019; Undeman et al., 2022).We also note that the concentrations of PCBs were relatively high in the South Corniche area compared to the Sports City area, especially in the summer.The reason for this is attributed to the increase in tourist activities in the summer, the presence of sewage channels, and the increase in external sources of pollution in general, in contrast the Sports City area is far away.
Relatively from the direct sources of pollution, our results also show that there is a difference in the distribution of the isomers of polychlorinated biphenyls (PCBs) in saltwater waters, as we find that the combinations that contain fewer chlorine atoms are the most distributed isomers, especially di-and pentachlorobiphenyls, and this is due to their tendency to dissolve in saltwater waters is greater than that of combinations containing a more significant number of chlorine atoms (Shiu et al., 1997).
The results showed that the concentrations of PCBs were high in the exotic fish collected from the southern Corniche area compared to the samples collected from the Sports City area.This is due to the presence of fishing boats, tourist activities (the company of many tourist restaurants along the Corniche), or canals.The water whose waste is discharged directly into water without prior treatment (Needham and Ghosh, 2019; Undeman et al., 2022).We note from the above a difference in the distribution of polychlorinated biphenyls in exotic fish collected from the study areas, as we find that combinations that contain a lower number of chlorine atoms accumulate in the studied fish, but in lower concentrations than combinations that contain a more significant number of chlorine atoms, such as PCB combinations PCB-209, 199.This is because combinations with higher molecular weights have a more remarkable, ability to accumulate and have a higher resistance to decomposition and metabolism, thus causing them to get more (Shaw, 1993).
As for the combinations octachlorobiphenyl and ecachlorobiphenyl, they were found in large concentrations in fish, and this is due to their ability to accumulate significantly in the muscle tissue of fish and the difficulty of metabolizing these combinations in fish (Josefsson et al., 2006;ATSDR, 1990).The correlation association that was studied between the concentration of PCBs and the lengths of the studied fish indicated the presence of a strong direct association.This shows an increase in the concentration of PCBs with the increasing size of the fish, which means the continuity of the accumulation of these combinations in living organisms over time.Exposure to these pollutants is as shown in (Figure 6).showed that the concentration of PCBs increased proportionally with the length of the fish, which shows that these combinations continued to accumulate over time, which may pose a threat to the food chain.The values of the logarithm of the bioconcentration factor between water and exotic fish ranged between 2.0026 L/Kg and 4.82 L/Kg, where an increase in the importance of the logarithm of the bioconcentration factor Log BCF was observed with increasing importance of the logarithm of the distribution coefficient between octanol and water Log Kow. Figure 7 represents the correlations between the bioconcentration coefficient between the water and the studied fish, Log BCF, and the distribution coefficient between octanol and water, Log Kow.

Figure 1
Figure 1 Chromatogram of a mixture of PCBs.

Figure 2
Figure 2 Concentrations of PCBs (µg/l) in the water of the South Corniche area.

Figure 3
Figure 3 Concentrations of PCBs (µg/l) in the water of the Sports City area.

Figure 4
Figure4shows the concentrations of polychlorinated biphenyl isomers (PCBs), where PCB-209 recorded the highest value, reaching 35.91 µg/g during the winter.In contrast, PCB-138 recorded the lowest value, reaching 0.492 µg/g during the winter as well.PCB-199 and PCB-209 recorded high concentrations in both seasons of the study compared to the rest of the combinations, and the attention of each of them were higher in the winter compared to their attention in the summer.

Figure 4
Figure 4 Concentrations of PCBs (µg/g) in Siganus rivulatus in the South Corniche area.

Figure 5
Figure 5 Concentrations of PCBs (µg/g) in Siganus rivulatus in the Sports City area.

Figure 6
Figure 6 Correlation between the total concentration of PCBs and the length of the Siganus rivulatus.

Figure 7
Figure 7Log Kow and Log BCF associations between the water and the studied fish.

Table 1
Concentrations of PCBs (µg/l) present in the water of the South Corniche region

Table 2
Concentrations of PCBs (µg/l) present in the water of the Sports City area.

Table 3
Concentrations of PCBs (µg/g) present in Siganus rivulatus fish in the South Corniche region

Table 4
Concentrations of PCBs (µg/g) present in Siganus rivulatus fish in the Sports City area.