Determination of heavy metals
Transcription
Determination of heavy metals
International Journal of Environmental Science and Development, Vol. 2, No. 6, December 2011 Determination of heavy metals (Cd, Co, Cu, Ni and Pb) in croacker fish (Johnius belangerii) from Musa estuary in the Persian Gulf Alireza safahieh, Fazel Abdolahpur Monikh, Mohammad Taghi Ronagh, Ahmad Savari, and Abdolmajid Doraghi 28]. On the other hand, heavy metals accumulation by fish may result in high level of metals intake by human consumers, which finally leads to serious health problems. Located in the northwest of the Persian Gulf, Musa estuary is surrounded by port, harbor, and petrochemical complex as well as urban areas. It is subjected to different types of human activities such as petrochemical industries, ships and oil tankers trafficking that are considered as potential sources of heavy metals input into the seawater. On the other hand, this estuary is an important location for fishing within the Iranian coasts of the Persian Gulf. Belanger's Croaker, Johnius belangerii is well distributed in Musa estuary and its arbitraries and constitutes a considerable portion of the annual catch of the local fishermen. In addition, it is widely used by local people for both direct and indirect consumption. Heavy metals accumulation by fish with high annual catch may contribute in sever health problems for its consumers. Since the information concerning heavy metal accumulation in Musa estuary is scarce, this study was carried out to determine the concentration of Cd, Co, Cu, Ni and Pb in muscle, liver and gill tissues of J. belangerii collected from different creeks of the estuary. Besides, a comparison of our results with those from other parts of the Persian Gulf is included to evaluate the magnitude of the contamination in the area. Abstract—Musa estuary is surrounded by port, harbor, petrochemichal complex as well as urban areas and receives various types of contaminants such as heavy metals. It is considered as a habitat for Belonger’s croaker Johnius belangerii in the Persian Gulf. Due to its relatively low price, the fish is commonly consumed by the local people in Mahshahr and Sarbandar cities, while there is no available data on heavy metals accumulation by this species. This study was carried out to determine the concentration of five heavy metals in J. belangerii tissues. Fish samples were taken from five creeks and dissected into muscle, liver and gills. The tissues were acid digested and analyzed for their heavy metal contents. The concentration of Cd, Co, Cu, Ni and Pb was determined by flame atomic absorption spectrometer. Results showed that the highest level of Cd, Co, Cu, Ni and Pb was 7.21, 1.08, 1.12, 2.72 µg/g and 4.57 in liver , 1.88, 1.04, 2.09, 9.43 and 6.83 µg/g in gills and 0.14, ND, 5.61, 2.43 and 3.78 µg/g in muscle respectively. The level of heavy metals in muscle was lower than WHO standard, meanwhile the level of metals in fish were decreased by the increase of distance from PETZON. Biomonitoring of contaminants in Musa estuary could serve as a good estimate of environmental health. Index Terms—Musa estuary, havy metals, Johnius belangerii, Persian Gulf I. INTRODUCTION Contamination of aquatic ecosystems with heavy metals receives particular attention [1]. Essential and non-essential heavy metals may appear as potentially harmful elements for most aquatic and terrestrial organisms at some concentrations of uptake. They are considered as serious contaminants because of their persistence and remarkable tendency to be concentrated in organisms tissues [2]. These elements are introduced into aquatic environment through different sources such as petrochemical wastewater, agricultural runoff, and urban effluents as well as tankers traffic [1]. Environmental factors such as pH, salinity, DO and temperature [6, 5] as well as ecological factors such as sex, size and feed habit play significant roles in heavy metal accumulation in aquatic organisms [11, 2]. Fish is regarded as an appropriate bio-indicator for metals concentration in aquatic ecosystems [4, 29, 30], because it could concentrate large amount of some metals in different tissues [15, 26, 27, II. MATERIALS AND METHODS A. Study Area The samples of fish were collected from five different creeks along Musa estuary during August 2010. The sampling stations were chosen in Khor-Ghazale, Khor-Ahmadi, Khor-Jafari, Khor-Zangi and Khor-Ghanam (Fig. 1). B. Sampling and Sample Preparation Using trawl net, 20 fish samples from the same size (19-25 cm total length and 54-66 g total weight) were collected from each creek. Fish were transferred to the laboratory using icebox and kept frozen at -20 o C until analysis. Before analysis, the samples were thawed in room temperature, their tissues including muscle, liver and gills were obtained and oven dried at 90 o C for 12 hour until constant weight was obtained. One gram of muscle, 0.5 gram of liver and gills were digested in concentrated nitric acid. The digestion procedure stated at 40 o C for 1 h and continued in 140 o C for the next 3 h. After digestion the samples were cooled in laboratory temperature and the remaining digested solutions were made up to certain volume with double distilled water Manuscript received October 12, 2011, revised October 13, 2011. A. Safahieh, F. Abdolahpur Monikh, M. T. Ronagh and A. Doraghi and with the Department of Marine Biology, Faculty of Marine Sciences and Oceanography, Khorramshahr University of Marine Science and Technology, Khorramshahr, Iran (email: a.Safahieh@Kmsu.ac.ir.) 460 International Journal of Environmental Science and Development, Vol. 2, No. 6, December 2011 and finally filtered through 42µm filter paper. To determine the metals concentration in the samples, a GBC (Savant AA Sigma) flame atomic absorption spectrometer (AAS) was used (Table I). All chemical regents were from analytical reagent grade (Merck). All solutions were prepared in deionized water. Calibration standards of each heavy metal were prepared by appropriate dilution of the stock solutions (1000 ppm, Merck). The glassware and plastic containers were acid washed with nitric acid 10% for 24 h and rinsed with double distilled water before use. To avoid samples contamination and check the accuracy of the method, blank samples and CRM (Dorm-2, muscle of Dogfish, National Research Council of Canada) were analyzed at the same time and with the same manner of the fish samples. The Blanks were also used to auto zero the apparatus and it was routinely analyzed after 10 metal analysis. The recovery values of all metals were satisfactorily fallen between 90% to 114% (Table II). C. Data Analysis As said, all data were subjected to Shapiro-wilk test in order to check normal distribution. Significant differences between heavy metals concentration in various stations were determined using One-Way analysis of variance (ANOVA) followed by Duncan post hoc test (α=0.05). Fig. 1. A map showing of study area TABLE I: THE OPERATION CONDITION OF THE AAS Metals Cd Co Cu Ni Pb Wavelengh (nm) 228.8 240.7 324.7 232 217 Silt Width (nm) 0.05 0.2 0.5 0.2 1 Lamp Current (MA) 3 6 3 4 5 TABLE II: HEAVY METALS LEVELS (µG/G D. W) OBSERVED IN DOGFISH MUSCLE CERTIFIED REFERENCE MATERIAL DORM-2 (NATIONAL RESEARCH COUNCIL, CANADA) Dorm-2 (muscle) Cd Co Cu Ni Pb Observed values 0.048 0.201 2.67 17.12 0.083 Gas Acetylene Acetylene Acetylene Acetylene Acetylene Support Air Air Air Air Air Khor-Jafari. The average concentration of the metals in liver is shown in Table IV. Significant differences were obtained for the concentration of Cd, Cu and Pb in liver among different stations. The maximum concentration of Cd (7.21 µg/g), Cu (12.32 µg/g) and Pb (4.57 µg/g) was found in the liver of fish from Khor-Zangi, Khor-Jafari and Khor-Ghazale respectively. Table V shows the concentrations of heavy metals in gills tissue. There were significant differences between concentrations of Cd Ni and Pb in gills tissue of fish from different creeks. The highest level of Cd (1.88 µg/g), Ni (9.43 µg/g) and Pb (6.83 µg/g) was recorded in fish from Khor-Zangi, Khor-Ghazale and Khor-Zangi respectively. The data indicated that each tissue has a specific capacity for heavy metals accumulation (Fig. 2). The order of metal accumulation in different tissues was as follows: gills > liver > muscle for Cd, Ni and Pb, liver > gills > muscle for Co and liver > muscle > gills for Cu. Certified values 0.043 0.182 2.34 19.4 0.065 III. RESULTS The average concentrations of studied heavy metals in Johnius belangerii from Musa estuary (µg/g d.w) in muscle are shown in Table III. The concentration of Co in muscle was below the detection limit of the AAS. There were significant differences between the concentration of Cu and Pb in fish from different stations. The highest level of Cu (5.61 µg/g) and Pb (3.78 µg/g) was measured in the fish from 461 International Journal of Environmental Science and Development, Vol. 2, No. 6, December 2011 TABLE III: HEAVY METAL CONCENTRATION IN MUSCLE (µG/G DW) Location Khor-Ghazale Khor-Ahmadi Khor-Jafari Khor-Zangi Khor-Ghanam a,b,c Cd 0.09 ± 0.20 0.13 ± 0.03 0.08 ± 0.02 0.14 ± 0.03 0.10 ± 0.02 Co Cu Ni a ND ND ND ND ND 1.62 ± 0.07 3.59 ± 0.04b 5.61 ± 0.80c 1.68 ± 0.18a 1.53 ± 0.02a 2.04 ± 0.29 2.16 ± 0.55 2.43 ± 0.57 2.10 ± 0.52 1.19 ± 0.37 Pb 1.58 ± 0.20ab 2.42 ± 0.38bc 3.78 ± 0.76c 2.98 ± 0.61bc 0.59 ± 0.05a Show differences among creeks, ND= Not Detected. TABLE IV: HEAVY METAL CONCENTRATION IN LIVER (µG/G DW) Location Khor-Ghazale Khor-Ahmadi Khor-Jafari Khor-Zangi Khor-Ghanam a,b,c Cd 2.38 ± 0.42ab 1.09 ± 0.33a 1.8 ± 0.37a 7.21 ± 1.2c 4.23 ± 0.44b Co Cu 4.31 ± 0.32b 10.75 ± 1.21c 12.32 ± 1.76c 5.12 ± 0.45b 1.76 ± 0.42a 0.94 ± 0.12 1.08 ± 0.28 1.03 ± 0.21 0.98 ± 0.19 0.91 ± 0.12 Ni 2.39 ± 0.29 2.72 ± 0.33 2.53 ± 0.12 2.27 ± 0.14 2.53 ± 0.15 Pb 4.57 ± 0.35b 3.08 ± 0.41ab 3.97 ± 0.47b 3.31 ± 0.22ab 2.64 ± 0.38a Show differences among creeks TABLE V: HEAVY METAL CONCENTRATION IN GILL (µG/G DW) Location Khor-Ghazale Khor-Ahmadi Khor-Jafari Khor-Zangi Khor-Ghanam a,b,c Cd Co Cu Ni Pb 0.97 ± 0.04ab 0.92 ± 0.04ab 1.32 ± 0.11ab 1.88 ± 0.13b 0.73 ± 0.03a 0.91 ± 0.02 0.83 ± 0.03 1.04 ± 0.1 0.86 ± 0.02 0.8 ± 0.01 2.04 ± 0.25 1.94 ± 0.19 2.09 ± 0.43 1.37 ± 0.38 1.04 ± 0.26 9.43 ± 1.04c 7.89 ± 1.12b 6.74 ± 1.26b 1.63 ± 0.21a 6.82 ± 1.33b 5.71 ± 1.06b 5.33 ± 1.26b 6.83 ± 1.48c 6.62 ± 1.43c 2.57 ± 0.32a Show differences among creeks Fig. 2. Heavy metals concentration in different tissues of Johnius belangerii (M: muscle, L:liver and G: gills) IV. DISCUSSIONS This study examined the concentrations of Cd, Co, Cu, Ni and Pb in Muscle, liver and gills tissues of J. belangerii from five creeks in Musa estuary. The heavy metal levels in J. belangerii tissues showed different values among the stations. The observed differences between metal concentrations in the same tissues from different creeks indicate that there are different sources for heavy metals input along Musa estuary. In addition, physicochemical factors of the water from which fish were caught may vary among studied creeks [9]. The relatively higher concentrations of some metals recorded in Khor-Jafari could be related to the effluent discharge from petrochemical units and Immam port [9]. A big branch of Khor-Jafari has been dried by PETZON (petrochemical special economic zone) and now serves as an effluent receiving pond, where refined wastes are discharged before releasing into the seawater. The high concentration of Ni that was measured in Khor-Ghazale might be due to heavy 462 traffic of oil tankers in this creek. Khor-Ahmadi are located between Khor-Jafari and Khor-Ghazale, thus heavy metal in this creek may result from dissolved metals in seawaters, which are transported via water movement. Khor-Zangi also receives a huge amount of petrochemical wastewater. In addition, this creek passes Sarbandar and Mashahr cities before empting into Musa estuary. Among the studied fish, those collected from Khor-Ghanam were less contaminated. Since this creek is relatively far from contamination sources in Musa estuary it seems that low amount of contaminants could reach this area. This study revealed that metal accumulation in gills and liver occurs in higher magnitude than what appeared in the muscle. This is a common finding that is also reported by several investigations [13, 5, 1]. Because of the presence of high levels of metallothionein protein, liver tissue acts as a target organ for heavy metal detoxification [14, 8, 2, 1, 21]. Gills act as the main site for entry of different kinds of contaminants such as heavy metals due to its continuous contact with the external medium. This organ serve a variety of physiological functions such as respiratory gas exchange, osmoregulation and nitrogen excretion [19, 20].Therefore, heavy metals may appear in a high level in liver and gill tissues compared to what occurs in muscle. Muscle tissue has lower tendency to accumulate heavy metals [22, 23, 24, 25]. Altindag and Yigit. (2005), Romeo et al. (1999) and Huang (2003) found higher concentration of heavy metals in liver and gill than in muscle. A few data is available concerning heavy metals concentration in fish species from north Persian Gulf however, published data on J. belangerii are scarce. Doraghi et al. (2009) reported concentrations of 0.62-0.78, 2.66-3.27, 9.48-11.78, 4.72-7.74, 1.82-3.22 µg/g dw for Cd, Co, Cu, Ni International Journal of Environmental Science and Development, Vol. 2, No. 6, December 2011 [3] and Pb respectively in J. belangerii collected from Hendyjan and Deylam, in the northwest Persian Gulf [16]. The metal concentrations in muscle of J. belangerii from Hendyjan and Deylam were higher than those found in Musa estuary. If compare the present results with metals concentration in Epinephelus coioides studied in the south Persian Gulf [17], it is clear that except Pb and Co in E. coioides from Bahrain and Pb in the same species from Quatar the concentration of other metals was noticeably higher in Cu and Ni measured in the muscle of fish in present study was higher than what reported for in J. belangerii . On the other hand metals concentration in muscle samples were more or less the same as the values reported for Euryglossa orientalis from the same locations [18]. Rather than contaminant concentrations in the ambient seawater, many other factors such as contamination source, environmental factors, age, inherent ability of the organism and even ecological niches may be involve in metals accumulation by fish. Although the maximum permissible level (MPL) has not been established yet for all contaminants, heavy metals concentration in edible tissue (muscle) of the studied fish (a wet wt. dry wt ratio of 0.3) was below the MPL values of Cu= 30 mg/kg and Pb= 2 mg/kg proposed by WHO [12]. Similarly heavy metals concentration in the muscle of J. belangerii in the present study were much lower than the MPL values of 0.5 mg/kg for Cd, 30 mg/kg for Cu and 2 mg/kg for Pb determined by FAO [12], indicating the absence of serious health risk for consumers. [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] V. CONCLUSION Present studies provide new information on the concentration of heavy metals in commercial fish from Musa estuary, the northwest Persian Gulf. Heavy metals concentration in tissues of J. belangerii from Khor-Jafari creek was higher than those fishes from other studied creeks. 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