Heavy Metal Concentrations in Common Freshwater Snails of Azraq Oasis, Jordan

See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/226763659 Heavy metal concentrations in common freshwater snails of Azraq Oasis, Jordan Article in Hydrobiologia · July 1994 DOI: 10.1007/BF00006248 CITATIONS READS 4 36 3 authors, including: Km Swaileh Birzeit University 28 PUBLICATIONS 397 CITATIONS SEE PROFILE All in-text references underlined in blue are linked to publications on ResearchGate, Available from: Km Swaileh letting you access and read them immediately. Retrieved on: 04 October 2016 Hydrobiologia 286: 167-173, 1994. © 1994 Kluwer Academic Publishers. Printed in Belgium. 167 Heavy metal concentrations in common freshwater snails of Azraq Oasis, Jordan Khaled M. Swaileh, Mohamed N. Mesmar & Naim S. Ismail* Department of Biology, Yarmouk University, Irbid, Jordan(*author for correspondence) Received 5 March 1992; in revised form 25 May 1993; accepted 13 July 1993 Key words: heavy metals, Melanopsis, Theodoxus, Melanoides, Azraq Oasis, Jordan Abstract Heavy metal concentrations in three freshwater snails, an aquatic plant, sediment, and water from Azraq Oasis pools in the Jordanian desert were measured by atomic absorption spectrophotometry. There were significant differences in metal accumulation among snail species. These snails are ranked according to their metal accumulation capacity in the order: Melanoides tuberculata>Melanopsispraemorsa> Theodoxusjordani. Although there were no significant differences among the size classes of these snails in metal concentrations, larger snails contained generally higher levels of metals than the smaller ones. The concentration factors for the selected snails exceeded 103, while it ranged from 0.1-10.2 x 103 for Typha angustata plants. Among sampling sites, metal concentrations in M. praemorsa, T. angustata, sediment, and water were not significantly different, except for Fe in M. praemorsa which was highest at station 3, and Cd and Cr which were highest in water and sediment of station 4. The seasonal variation in metal content was found to be species and metal-dependent. Introduction Azraq Oasis lies in the Jordanian desert at about 100 km east of Amman, the capital city of Metal pollution is becoming important with the Jordan. It provides drinking water for Amman rapid development in industry and technology. and some other cities in Jordan, and has a special The use of living organisms as bioindicators of importance in being a national park for migrating metal pollution has several advantages: they in- birds between Africa and Eurasia (Nelson, 1973). tegrate pollution over a period of time; indicate However, there have been no studies on the heavy the bioavailability and biomobility of the pollut- metals in Azraq Oasis inspite the potential pol- ant; may concentrate the pollutant to levels that lution from the increasing traffic on the highways exceed those in the abiotic environment (Martin passing through Azraq to Iraq and Saudi Arabia. & Coughtrey, 1982; Moriarty, 1983). Thus, for a The freshwater bodies of Azraq are heavily species to act as an effective indicator of metal populated with three prosobranch snails: Mel- pollution it must have the ability to concentrate anoides tuberculata (Muller, 1774) (Thiaridae), metals, and be abundant and easily collected in Melanopsis praemorsa (Linnaeus, 1758) the study area. (Thiaridae), and Theodoxus jordani (Sowerby, 168 1836) (Neritidae). The cat tail, Typha angustata, a calliper, divided into size classes, dried at room is the most common aquatic plant in Azraq temperature over a filter paper, and deep frozen (Nelson, 1973). for further analysis. The purpose of the present study is to deter- Submerged pieces of 3 to 5 T. angustata plants mine the concentration of Cu, Zn, Fe, Pb, Cd, Co, were collected from each pool, washed with dis- Mn, and Cr metals in water, sediment, common tilled water, and deep frozen for later analysis. snails, and the aquatic plants in Azraq, in order Similarly, 3 to 5 sediment samples were taken to select the best bioindicators for future moni- from each pool and deep frozen for later analy- toring programs. sis. Three, one liter, water samples were collected from each pool and stored at 4 C until analyzed. The sampling protocol was repeated for four Materials and methods successive seasons: Summer (July 1989), Autumn (October, 1989), Winter (January 1990), and Study area Spring (April 1990). Azraq has a true desert climate, with hot dry summers and cool wet winters. The average Analytical procedures annual rainfall is below 100 mm and precipitation occurs mainly during December-January. The A total of 30-225 snails of each size class from extreme annual air temperature range is 10-45 ° C each pool were crushed, and their tissues were with an average of 29 C (Nelson, 1973). dried at 85 C to constant weights. Weighed dry There are two major springs in Azraq which samples (0.1 gm) were digested in a hot 4:1 mix- provide water for its pools. Three pools in South ture of concentrated 'Analar' nitric and perchlo- Azraq and one in North Azraq were selected for ric acids until a clear solution was obtained this study (Fig. 1). Two pools in South Azraq (Andrews, 1989). The clear solutions were then (Stations 1 and 2) and the pool at North Azraq diluted to 100 ml using distilled water. Similarly (Station 4) are closed to people since they are the collected specimens of T. angustata from each located in the vicinity of the water pumping sta- pool were dried and digested as described above. tions. However, station 3 at South Azraq is not The sediment samples were oven dried and two closed and is used for activities such as fishing grams from each sample were treated with 30% and swimming. H 20 2 in a boiling water bath to destroy the or- ganic matter (Malo, 1977). Samples were diluted to 200 ml with distilled water and 10 ml of 6M Sampling HCl were added and the suspension was heated for 30 minutes. The hot mixture was filtered Selected snail species were randomly collected by through a Whatman No. 42 filter paper. The resi- hand picking from edges of the pools and trans- dues on the filter paper were washed three times ferred into clean plastic bags. Melanoides tuber- with hot dilute HCl (1:19, v:v) and the filtrate was culata was commonly found in the thin layer of cooled and brought up to 250 ml with the same detritus covering the bottom of the pools. Melan- dilute HCI. The water samples were filtered opsis praemorsa and Theodoxus jordani were usu- through 0.45 m millipore filter paper to separate ally found attached to leaves of the common particulates (Wahbeh et al., 1985). The concen- aquatic plant Typha angustata. The collected trations of 8 heavy metals (Zn, Co, Cu, Cr, Cd, snails were kept in an ice-box and transferred to Fe, Mn, and Pb) in the above solutions and in the the laboratory where they were washed with dis- filtered water samples were measured using a tilled water, identified according to Brown (1980), flame atomic absorption spectrophotometer (Pye measured to the nearest millimeter of length using Unicam). 169 Fig. 1. Location map of Azraq Oasis showing the sampling stations (1, 2, 3, and 4). Statisticalanalysis concentration in a selected snail to that in water, was calculated for each snail species and the Data were expressed as mean concentrations aquatic plant. The biotransference factor, which (ppm) + S.D. The main effects of snail size, sam- is the ratio of a metal concentration in a selected pling sites, and the seasonal variation of the metal snail to that in the aquatic plant, was measured concentration were tested using the one way for the three snail species. analysis of variance. p = 0.05 was taken as the level of significance. Duncan's multiple range test was further employed to identify the highest con- Results centrations that are significantly (p < 0.05) different from the lowest concentrations. The concen- There were significant differences in the mean tration factor, which reflects the ratio of a metal concentrations of the heavy metals Cu, Zn, Fe, 170 Pb, Cd, Co, Mn, and Cr among the three snail tion of the snails, the aquatic plant, sediment, and species (Table 1). In general, M. tuberculata con- water is shown in Fig. 2. There were significant tained significantly higher levels of metals other seasonal variations in the mean concentrations of than M. praemorsa and T. jordani, except for Fe Cu, Fe, Pb, Cd, and Cr in M. praemorsa. The level and Mn which were highest in M. praemorsa. Sig- of Cu and Fe were highest during autumn and nificantly lower means of the heavy metals were winter, while Cd and Cr levels were highest dur- found in T. jordani. No significant difference in ing winter and spring. The concentration of Pb the mean concentrations of metals were found was highest during autumn. Moreover, Duncan's among the size classes of the selected snail spe- test indicated significantly higher concentrations cies. However, larger (> 10 mm) M. tuberculata of Zn and Co during spring and winter, respec- snails contained higher levels of the heavy metals tively, than those during autumn and winter, re- than the smaller ones (< 10 mm). Large snails spectively. There were significant seasonal varia- (> 15 mm) of M. praemorsacontained also higher tions in the Cu, Mn, and Cr concentrations of concentrations of Cu, Zn, Fe, Cd, Mn, and Cr M. tuberculata. The highest concentrations of Cu than the medium (11-15mm) and small and Cr were during winter. The level of Mn was (< 5 mm) snails. Large snails (> 5 mm) of T. jor- highest during summer. Similarly, Duncan's test dani contained higher concentrations of Cu, Cd, indicated significantly high concentration of Fe and Cr than the smaller (< 5 mm) snails.

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