مطالعه امكان استفاده از دوكفه‌اي Barbatia helblingii به عنوان پايشگر زيستي تركيباتPAHs در سواحل بوشهر

Evaluation of Ark clam (Barbatia helblingii) as Biomonitor Agent for PAHs Contamination in Coastal Area of Bushehr

هيدروكربن‌هاي آروماتيك چندحلقه‌اي (PAHs) گروه بزرگي از آلاينده‌هاي آلي هستند. بسياري از اين تركيبات، بالقوه سمي بوده و نتيجه تماس جانداران با اين تركيبات موضوع تحقيقات بسياري را به خود اختصاص داده است. سواحل استان بوشهر محل انجام بسياري از فعاليت‌هاي استخراج و حمل و نقل مواد نفتي در شمال خليج فارس است و احتمال مي‌رود مقادير چشمگيري از اين تركيبات در آب و آبزيان اين منطقه وجود داشته باشد. به منظور آگاهي از غلظت PAHs در آب دريا و دوكفه‌اي Barbatia helblingiiو بررسي امكان پايش اين تركيبات توسط دوكفه‌اي مذكور، نمونه‌برداري از آب و دوكفه‌اي در 5 ايستگاه مختلف درمنطقه جزر و مدي ساحل بوشهر انجام شد. پس از هضم و استخراج PAHsبا حلال‌هاي آلي، اين تركيبات به وسيله دستگاه كروماتوگرافي مايع با كارايي بالا (HPLC) تفكيك و سنجش شدند. نتايج نشان داد غلظت PAHs كل در آب ايستگاههاي مورد مطالعه از 04/4 تا 03/31 ميكروگرم در ليتر متغير بوده است. غلظت اين تركيبات در بافت نرم دوكفه‌اي B.helblingii در ايستگاههاي مورد مطالعه،54/129 تا 75/634 نانوگرم برگرم وزن خشك بوده است. غلظت PAHs در آب و صدف جمع‌آوري شده از ايستگاههاي مختلف تفاوت معني‌داري با يكديگر داشت (05/0(P < . رافايل آلوده‌ترين و آب شيرين‌ كن تميزترين ايستگاه بود. نتايج نشان داد همبستگي مستقيم و معني‌داري ميان غلظت تركيبات PAHs در آب و دوكفه‌اي وجود دارد (05/0(P < . با توجه به نتايج حاصل، دوكفه‌اي B.helblingii به‌عنوان گونه مناسبي براي پايش زيستي تركيبات PAHs درسواحل بوشهر معرفي مي‌شود.

Introduction Polycyclic aromatic hydrocarbons (PAHs) are a major group of organic contaminants consisted of two or more benzene rings. Many of these compounds are potentially toxic for both human and aquatic life. Therefore, many studies have been carried out to investigate their toxicity in PAHs exposed organisms. Bushehr coastal area is impacted by PAHs compounds derived from human activities related to oil exploitation and export. In addition, it is also influenced by contaminations originated from industrial and municipal discharges. Since all mentioned contaminants are major sources of PAHs input in to the Bushehr marine environment, PAHs contamination of water and aquatic organisms in the area is an expected issue. The bivalveʹs metabolism system is not well developed to remove PAHs content from their bodies rapidly. These are filter feeder organisms with low mobility. These characteristics make them eligible candidates for biomonitoring of PAHs compounds in coastal ecosystems. Since Ark clam (Barbatia helblingii) is well distributed in Bushehr coasts, this investigation is carried out to evaluate the potential of this specie as a biomonitoring agent for PAHs contamination. Materials and Methods E-mail: a.safahieh@kmsu.ac.ir Seawater and clams were sampled from five different stations of intertidal zone, including Rafael, Sheghab, Abshirinkon, Industrial zone and Helyleh (stations 1 to 5) along Bushehr coasts (Figure 1). PAHs were extracted from seawater using hexane as solvent and separation funnel as apparatus. The extract was passed throughout anhydrous sodium sulphate followed by florsil column. In order to digest PAHs and extract them from clamʹs tissues, about 5 g of homogenised and freeze-dried soft tissue was digested in soxhlet apparatus with 200 ml of methanol and 20 ml of 2M KOH. Then PAHs were extracted by separation funnel containing 90 ml hexane and 30 ml water. The extracts were passed through clean¬up column containing 10 mg Alumina, 10 mg silica and 10 mg anhydrous sodium sulphate. When the whole solvent was evaporated, 1 ml of acetonitril was added to each sample and the samples were transferred into the vials. PAHs concentration was detected by HPLC system, equipped with reversed- phase Ci8 (4.5x250 mm) column and UV detector. The liquid gradient used was a mixture of acetonitril (60%) and water (40%), which was shifted to 100% acetonitril within 30 minutes. Corresponding author: Tel: 09168331821 Fig.l: Locations of the sampling stations. Results and discussion Results showed that the PAHs concentrations in seawater samples taken from Rafael, Sheghab, Abshirinkon, Industrial zone and Helyleh stations were 31.03, 20.85, 4.04, 17.58 and 12.29 jug/1 respectively (Figure 2-a). These levels are below the PAHs levels reported from Bandar Anzali lagoon (116.5), coastal waters in Bahrain (16-89) and China (4.70-67.70), while they were higher than the PAHs concentrations in the water samples from Chesapeake Bay (0.02-0.06), northwest of Baltic Sea (0.03- 0.05) and Daya Bay in China (4.22-29.32) reported by previous studies. O * «-a rh a e 20 400 g 10 Rafael Sheghab Abshirinkon IndustnalZone Helyleh Rafael Sheghab Abshirinkon Industrial Zone Helyleh Fig. 2:Total PAHs (tPAHs) concentration in seawater (a) and soft tissues of B.helblingii (b) Concentration of tPAHs in soft tissue of B.helblingii from the same stations was 634.75, 476.66, 129.54, 452.47 and 414.96 ng/g (dw) respectively (Figure 2-b). Significant differences were found between tPAHs concentrations in both seawater and clam samples collected from different stations (P<0.05). The maximum PAHs concentration in seawater was measured in Rafael station, while the minimum was observed in Abshirinkon. The Rafael station is exposed to municipal and harbor wastes. Low PAHs concentration in Abshirinkon station might be attributed to its long distance from urban area and harbors. The molecular composition of PAHs in seawater and clams were different to some extent. Generally 3- ringed PAHs molecules were dominant in water samples, while 5+6-ringed PAHs molecules were scarce. The same pattern of molecular composition was also observed in clamʹs soft tissue. The only exception was found in the soft tissues collected from Helyleh station in which 4-ringed PAHs were dominant compared to 3-ringed compounds (Table 2). Generally it seems that the amount of clams accumulated by low molecular weighted PAHs (3 and 4-ringed) was more than high molecular weighted compounds (5 and 6-ringed). Table 2: PAHs concentration in soft tissues of Ark clam (B.helblingii) and seawater sampled from Busher, the Persian Gulf Stations Rafael Sheghab Abshirinkon Industrial Zone Helyleh Seawater (ug/l) 13 ring PAHs 25.09+2.33 12.45+2.33 3.60+0.99 13.12+1.60 8.34+2.30 14 ring PAHs 5.94+0.66 8.40+1.26 0.48+0.17 2.81+0.29 3.54+0.60 15+6 ring PAHs - - - 1.54+0.18 0.41+0.08 tPAHs 31.03+2.99 20.85+3.59 4.04+1.16 17.58+2.29 12.29+3.05 B. helblingii ng/g(dw) 13 ring PAHs 352.24+23.78 224.56+16.19 68.24+8.27 247.96+20.38 153.37+10.37 14 ring PAHs 243.77+16.62 223.54+17.07 44.01+8.15 136.54+10.02 261.59+14.92 15+6 ring PAHs 38.74+3.02 28.56+4.47 17.28+1.69 67.97+2.80 - tPAHs 634.75+43.43 476.66+37.74 129.54+18.10 452.47+33.14 414.96+25.30 A significant linear correlation was found between tPAHs concentrations in seawater and clamʹs tissues (P<0.05). The same correlation was also found for 3-ringed, 4-ringed, and 5+6-ringed PAHs in seawater and clams. Correlations between PAHs concentrations in seawater and soft tissues of clams are shown in Figure 3. Although it seems that the value of Pearson correlation coefficient between PAHs concentrations in water and clamʹs tissues is negatively influenced by the number of aromatic rings existing in PAHs molecules, all correlations were positive and significant (P<0.05). 2 4 6 4 ling PAHs concentration in seawater (>i« I) 0 0.5 1 1.5 2 5+6 ling PAHs concentration in sea watering 1) Fig. 3: Correlation between PAHs concentrations in seawater and soft tissues of clams (P<0.05), a: tPAHs, b: 3-ringed PAHs, c: 4-ringed PAHs and d: 5+6- ringed PAHs. The clam B. helblingii is well distributed in the north Persian Gulf. It could be sampled easily and provides sufficient amounts of soft tissues for PAHs analysis. According to all mentioned advantages it is concluded that B.helblingii could serve as suitable biomonitoring agent for PAHs contamination in Persian Gulf. Key words v = 12.997X + 45.492 R=0.97 P<0.05 3 «s II 10 20 3 ring PAHs concentration in seawater (ng 1) y = 25.393x + 20.607 R=0.66 P<0.05 Biomonitoring, PAHs, Ark clam (B.helblingii), Bushehr coasts, Persian