Editorial

, Volume: 15( 10) DOI: 10.37532/1753-0431.2020.15(10).1-21

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Evaluation of Adsorption and Absorption Factors for Radionuclides and Organic Compounds for Marine Ecosystem in Red sea , Egypt

*Correspondence:

Khaled. M. Zakaria Faculty of science, Al- Azhar University, Oceanography & fisheries sector, Egypt, E-mail: drkhaledzakaria@gmail.com

Abstract

Keywords

Radionuclides, Oil spills; Absorption; Adsorption, Organic compounds

Introduction

Naturally, radionuclides are unstable when they undergo radioactive decay become stable [1]. Recently, the number of radionuclides such as ²³⁸U, ²³²Th, ²²⁸Ra, and ⁴⁰K in the marine biosphere has drawn much attention as a major ecological and public health concern because radium takes a long time to degrade in the human body[2]. In reality, radium-²²⁸ (²²⁸Ra) emits beta radiation with low energy and relatively poor ionization capacity, and radium²²⁶Ra (^226RaRa) releases alpha particles with very high energy[3]. Several communities of the world take marine biota as a significant source of protein[4]. The three main process uptake mechanisms of radium in marine organisms are adsorption, absorption, and intake through water and feed. The fish take radionuclides through food sediment and mainly water[5]. Several researchers have demonstrated that organisms living in or on polluted sediments can bioaccumulate the pollutants [6]. An elegant experiment carried out by Farrington involving a multiphase experimental exposure design of a demersal fish (Leiostomus xanthurus) feeding on a polychaete (Nereis virens) with both fish and polychaete exposed to PCB-contaminated 77]. This factor enables the bioaccumulation abilities of two species toward a single radionuclide to be compared. In this case, the term 'bioaccumulation ability' should be understood as the relationship between the bioaccumulation rate during a given time interval and the bioaccumulative capacity. However, more than the simple measurement of radionuclide concentrations is required to distinguish which of these two components is the most influential on the final result.

In knowledge, fishes have many health benefits due to their rich source of vitamins and minerals[8]. In contrast, the intake of accumulated radionuclides fish has many serious health concerns[9]. In studies of the behavior of heavy metals and organic pollutants, radionuclides can be utilized as radiotracers[10]. “Unfortunately, in the current study, the steady state was not achieved during the experiment to calculate radionuclide concentrations in the seawater”. Therefore, it was hypothesized to measure the bioconcentration of radionuclides, total petroleum hydrocarbon, and total aliphatic hydrocarbons in marine algae with water and sediments of habitat. This could be helpful in the determination of targeted chemicals to assess the risk of a hazardous effect on health.

Materials and Methods

Study area

The study area was along the coast of Ras Ghareb, Egypt. The spatial position of station 1 is latitude 28° 21' 13ʺ and longitude 33°5' 40ʺ while station 2 is latitude 28°20' 19ʺ and longitude 33°6' 45ʺ.

Sampling

The samples were taken from superficial shoreline sediment, seawater, marine species of algae, Sargassum dentifolium (Brown algae), and Chondria seticulosa (Red algae) at Ras Ghareb, Egypt station1, and station2. The samples were properly packed in polythene bags and transported into a laboratory for chemical analysis.

Preparation of experimental samples

The seashore sediment samples were air-dried at room temperature for a week. Further, it was incubated in the oven at 80°C for 48 hours till constant dry weight was obtained while crushed and homogenized. Then the samples were milled, sieved through 0.4 mm mesh filters, and stored for further analysis. The water was collected through a water sampler of 5 liters in each separate polythene bag. Then samples were acidified with Nitric acid that attained a pH of less than 2 to avoid micro-organisms growth. The samples were stored for radioactivity and Polycyclic aromatic hydrocarbon measurements. The samples were taken out of the ice pack, thawed, and rinsed with tap water to eliminate contamination in the lab. Then it was divided into pieces and put in a sample vial after being processed with an aseptic tool and plates. After that, the samples were labeled. The samples of marine organisms Sargassum dentifolium and Chondria seticulosa were transported to the laboratory in ice boxes and stored at -10oC until further analysis, and about 20 samples of each species were collected from the study area from the same location as water samples. The marine samples were washed and cut into smaller pieces for effective grinding. The cleaned samples were dried in an oven at 70oC for five days to ensure that the sample was completely moisture free and had a constant dry weight gain. The dried samples were ground to fine grain sizes using a stainless-steel cutter blender and sieved to obtain homogeneity. All homogenized samples were divided into two parts. The first part was transferred into a 250 ml sizes Marinelli beaker that was sealed hermetically and left for about four weeks at room temperature to attain secular equilibrium among the ²³⁸U-series and ²³²Th-series precursors with their short-lived progenies[11]. The second part was kept in the laboratory at room temperature to be used for the analysis of the organic hydrocarbon samples.

Radioactivity measurements

The concentration of natural radioactive elements ²³⁸U, ²³²Th, and ⁴⁰K in the samples was determined using a highresolution HPGe γ-spectrometry system with 30% counting efficiency.

It was performed using 250 cm3 counting vials filled to a height of 7 cm, corresponding to 170 cm3. The duration measurement was up to 80,000 sec and was carried out in the Egyptian Nuclear and Radiological Regulatory Authority Laboratory. The obtained spectra were analyzed. The gamma-ray transitions were used to determine the existence of radionuclides and calculate their activities. The ²²⁶RaRa or ²³⁸U activities were estimated from 234Th (92.38keV, 5.6%) for samples assumed to be in radioactive equilibrium. However, γ-energies of 214Pb (351.9 keV, 35.8%) and 214Bi (609.3,45%), (1764.5 keV, 17%), and ²²⁶RaRa (185.99 KeV, 3.5%) were used to estimate the concentration of ²²⁶RaRa. The Gamma-ray energies of 212Pb (²³⁸.6 keV, 45%), and ²²⁸Ac (338.4 keV, 12.3%), (911.07 keV, 29%), (968.90 keV, 17 %) were used to estimate the concentration of ²³²Th. The activity concentrations of ⁴⁰K were measured directly by their gamma rays (1460.8 keV, 10.7%). An empty polystyrene container was counted the same way as the samples to assess the background distribution caused by naturally occurring radionuclides in the area around the detector. The final activity concentrations were calculated after measurement and subtraction of the background. The activities were determined by measuring their respective decay daughters [12-15].

Total Petroleum Hydrocarbons (TPH extraction )

The cute parts of algae were crushed in a mortar with a pestle. The extraction was performed using ten grams of samples from each specie, weight through analytical balance. The sample was put into a 100 mL beaker and 60mL of acetone and dichloromethane (1:1 v/v) were used as an extraction solvent. The total petroleum hydrocarbon contents of Sargassum dentifolium and Chondria seticulosa were extracted by shaking. The beaker with the content was placed on a magnetic stirrer/ heater and shaken for about 10 minutes at 70°C. The extract was poured into a clean roundbottom flask. Then 30 mL of fresh solvent was added, and the process was repeated. The extracts were combined, and 5 grams of anhydrous sodium sulfate was added to remove water. The extract was concentrated to 3 mL with a rotary evaporator maintained at 20°C. Then 1.5 mL of the concentrated extract was loaded on a silica gel column. The silica gel column was prepared by loading a 2 g glass wool, followed by 30 g silica gel, onto a chromatographic column that was 2 cm internal diameter and 10 cm long. Each bed was prepared with 40 ml HPLC-hexane to remove any organic contaminant.

Furthermore, 1.5 mL concentrated extract was loaded and eluted with 30 mL HPLC hexane into a labeled100 mL beaker to get the aliphatic hydrocarbon components in the sample. After the hexane had almost eluted through the column, but before completely letting the column dry, 30 mL of dichloromethane was added to elute the aromatic hydrocarbon contents into another labeled 100 mL beaker. Then 2 g of anhydrous sodium sulfate was added to remove any traces of water left in the extract. The fractions were concentrated using a rotary evaporator of about 2 ml. Then 1ml of the extract was transferred into a well-labeled vial ready for gas chromatographic analysis. The samples were stored at 4°C until GC analysis.

Gas chromatographic analysis

Each extract was transferred to a 1.5 mL vial and was loaded into a gas chromatography system Agilent 6890 series model G1530 A, with Flame Ionization Detector (FID) and cold on-column injection. Then 1μL sample was injected and analyzed for TPH (C9–C36). An HP-5 (crosslinked PH ME siloxane) column with dimensions 30 m x 0.25 mm with a stationary phase thickness of 0.25 μm was used for analytical separation. The carrier gas was purified nitrogen held at a flow rate of 5 mL per minute. The operating temperature program was started at 60°C for 2 mins and then increased at a rate of 10°C per minute to 300°C for 10 minutes. The injector and detector temperature were maintained at 250°C(FIG. 1).

Results and Discussion

Radionuclides in seawater and sediments

The absorption of ²³⁸U, ²³²Th, and ⁴⁰K in seawater and coastal sediments of two regions in Ras Ghareb, Egypt. nucleoid concentration was found higher in sediments than in seawater of both regions (FIG. 2). Thorium was found with low concentration in sediments than water only in the region1. While the amount of ⁴⁰K in both water and sediments varies significantly (TABLE 1).

TABLE 1. Concentration of ²³⁸U, ²³²Th, and ⁴⁰K in seawater and coastal sediments collected from different locations along the Ras Ghareb region coastline.

A study was done along the coast of the Oman Sea on the concentration of ²³⁸U, ²³²Th, and ⁴⁰K, showing that sediments have agreater variety of radionuclides than water samples. Though, it was acceptable in terms of environmental andradioisotope risks when compared to reference values fromIran and other regions of the world. Regarding the turkey, the radio nucleotide value was found higher than permitted by global guidelines[16].

Another study in the Gulf of Thailand of these three natural radionuclides found high concentrations in marine sediment. In Jeddah, Saudi Arabia, a similar study found the normal limit of these radionuclides in the sediment.

Radionuclides in marine biota

The comparative analysis of radioactive material in both species revealed varying levels in their respective locations (FIG. 3). The concentration of selected radionuclides was found high in Chondria seticulosa in both regions. While the concentration of these radionuclides was high in region 1 than in region 2 in both algae species (TABLE 2).

TABLE 2. Concentration of ²³⁸U, ²³²Th, and ⁴⁰K in marine organisms collected from different locations along the Ras Ghareb region coastline.

A research study was conducted in Nigeria to find out the concentration of radionuclides in fish and fish feed, due to their high consumption rate in the area. The results found that both adults and children received annual committed effective doses that were all below the suggested 1.0 mSv y1 limit for members of the public. This demonstrates that, from a radiological standpoint, the radiation dose derived from ingesting fresh fish samples does not represent any substantial health hazards to the public [17, 18]. An investigation was made into the radioactive activity of wild fungi in Iraq, particularly black desert truffles. The measured values were identified as lower than the estimated value for the international mean [19].

The bioconcentration factor algae

The bioconcentration of radionuclides was found with a high concentration in Chondria seticulosa in both regions of the samples. The high concretion of ²³⁸U 2.016, was found in Chondria seticulosa in Region1. While the BCF of ⁴⁰K was 1.178 in Chondria seticulosa The use of concentration factors as a practical technique to represent the accumulation of radionuclides in biota relative to radionuclide concentrations in seawater was motivated by the necessity to report radionuclide accumulation in biota in various conditions and geographical areas. Later, concentration factors were used to forecast radioactivity in organisms and model radioactive distribution and transfer in aquatic settings [20]. In China, it was found that humans ingested the aquatic animals at a determined committed effective dose of 0.06 mSv-2.99 mSv. The artificial nuclides 90Sr and 137Cs had minimal dose contributions, but 210Po was the main source of radiation damage in both marine creatures and humans [21].

Petroleum hydrocarbons in seawater and sediments

The findings of TPH show varying results in seawater and sediments of both sites. The highest value of Decane C10 was 31.6 ng/g DW followed by N (TABLE 3).

TABLE 3. Bioconcentration Factor (BCF) for radionuclides in marine organisms along the Ras Ghareb region coastline.

Nonane C9 at 28.3 ng/g DW was found in Region 2 of Ras Ghareb among the TPH. The overall values of TPH were observed high in region 2 as compared to Region 1 (FIG. 4). The TPH 160.2 ng/g DW was found in the Region 2 coastal sediments (TABLE 4).

TABLE 4. Concentration levels of total aliphatic hydrocarbons TAH found in marine organisms collected from different locations along the Ras Ghareb region coastline.

According to a study in the Southern China sea on TPHs and n-alkanes. Here it was found that TPHs were higher than those on the far shore in the central and northern waters along the shoreline. The concentration of n-alkanes in the water samples ranged from C10 to C38, and they were primarily produced by higher terrestrial plants [22]. The TPH levels found in Pulicat Lake in India throughout the study period present less of an ecological threat to the environment and biota [23].

Total aliphatic hydrocarbons in brown and red algae

The results of TAH demonstrate that both sites of water and sediments have different outcomes. In Region 2 of Ras Ghareb, among the TAH, the highest concentration of Dodecane C12 was found at 29.7 ng/g DW, followed by Nonane C9 at 28.2 ng/g DW of Chondria seticulosa. When comparing the TAH of area 1 which was 45.5 and 82.7 with region 2 which was 101 and 134, it was found that region 2 has a high concentration of aliphatic hydrocarbons (FIG. 5). Correspondingly, it was also observed that Chondria seticulosa has a high absorption capacity of TAH than Sargassum dentifolium (TABLE 5). The F3 and F4 fractions of Fucus viroids were found to have good radical scavenging properties in vitro, and zebrafish embryos showed a protective effect against oxidative stress brought on by hydrogen peroxide (FIG. 6) [24]. The two species of algae Taonia atomaria and Padina pavonica of the central Adriatic Sea were significantly found to be primary oil composition constituents[25] (TABLE 6) .

TABLE 5. Concentration levels of total aliphatic hydrocarbons TAH found in marine organisms collected from different locations along the Ras Ghareb region coastline.

TABLE 6. Bio-Concentration Factor (BCF) for the investigated TAH in the investigated marine organisms in the water.

Bioconcentration factor for total aliphatic hydrocarbons in brown and red algae

The BCF of Region 1 6.8, 14.7 has greater than region 2, while Chondria seticulosa was shown a higher value of TAH in both sites. Eicosane C20 was the highest BCF in Chondria seticulosa of Region 1. The high bioconcentration of aliphatic compounds in Chondria seticulosa indicates its absorption capacity(TABLE 7).

TABLE 7. Comparison of activity concentration of 226Ra, ²³²Th, and ⁴⁰K (Bq/kg) in algae in other studies.

The ability of mangroves to absorb and store heavy metals in their tissue lower heavy metals in the aquatic environment because of their capacity to do so (FIG. 7). According to the review, the mangrove species have a promising potential to be employed for biomonitoring in the aquatic environment[26-32] (TABLE 8). Perennial herbs species were identified as sensitive that can be produced to lessen soil contamination in Pazanan, based on their frequency and resistance to adverse conditions is a suitable option for the phytoremediation of soil contaminated with nickel and TPHs [33-44] (TABLE 9) .

TABLE 8. Comparison of activity concentration of 226Ra, ²³²Th, and ⁴⁰K (Bq/L) in Seawater those in other studies.

TABLE 9. Comparison of activity concentration of 226Ra, ²³²Th, and ⁴⁰K (Bq/ Kg) in Sediments those in other studies.

Investigated marine organisms ²³⁸U: Isotope of uranium, ²³²Th: naturally occurring isotope of thorium, ⁴⁰K: radioactive isotope of potassium, BCF: Bio-concentration factor[45-57] .

Conclusion

The chemical analysis of seawater, sediments and marine algae was performed to investigate their adsorption and absorption capacity of radionuclides, total petroleum hydrocarbons, and total aliphatic hydrocarbons. the concentration and bioaccumulation of radionuclides, TPH, and TAH were observed with high levels in the coastal sediments and red algae of Ras Gareb as compared to water and brown algae. The value of radionuclides was found within the acceptable range of international limits. The Chondria seticulosa were found with significant absorption of TPH, TAH, and radionuclides. So, it could be used to lower the concentration of these chemicals in seawater.

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