Shadegan Wetland: Heavy Metals Contamination & Ecological Risk, Essays (university) of Urban planning

Download Shadegan Wetland: Heavy Metals Contamination & Ecological Risk and more Essays (university) Urban planning in PDF only on Docsity! Contemporary Urban Affairs 2017, Volume 1, Number 3, pages 67– 72 Quality Evaluation and Study of Ecological Toxicity of Heavy Metals in Shadegan Wetland * Dr. Samar Mortazavi 1, Dr. Mohsen Tizhoosh 2, Dr. Zahra Cheraghi 3 1, 2, 3 Department of Environmental Science, Faculty of Natural Recourses and Environmental Science, Malayer University, Iran 1 E mail: mortazavi.s@gmail.com , 3 E mail: nejatsan@tums.sc.ir A B S T R A C T Wetlands hold a principal position in storing food for primary producers, so they are not able to bear the pressure. The slightest disturbance, hence, may harm wetlands and cause detrimental effects. The present study aims at monitoring heavy metals and evaluation of the sediment quality index of Shadegan wetland in Iran. Thus, a sampling of surface sediments of the wetland was performed at ten stations with three replications; after the preparation of samples with aqua regia, the concentrations of heavy metals were measured by atomic absorption spectroscopy. The quantification of sediment pollution using the contamination factor, contamination degree, pollution load index, ecological risk assessment index, and ecological toxicity of heavy metals in the region were all carried out. The results of Cf and Cd showed that the degree of zinc and copper contamination is low; however, the degree of lead contamination is moderate. Moreover, the obtained PLI was less than 1 indicating a lack of sediments contamination with heavy metals. The RI was less than 150 indicating a low risk of contamination. In addition, comparing the concentrations of elements with National Oceanic and Atmospheric Administration and Sediment Quality Guidelines showed slightly toxic and non-toxic sediments, respectively. Finally, based on a mixture of effect range median, all sediment samples are placed in the first category with less than 12% toxicity probability. CONTEMPORARY URBAN AFFAIRS (2017) 1(3), 66-72. https://doi.org/10.25034/ijcua.2018.3683 www.ijcua.com Copyright © 2017 Contemporary Urban Affairs. All rights reserved. 1. Introduction Aquatic ecosystems, as one of the main environmental features, are a key supplier of food and a roof over aquatic organism’s head; on the other hand, they are also large sources for a wide range of pollutants. Since these ecosystems withstand a high capacity for development, they are subject to more serious risk due to the pollutants. Domestic and industrial sewage discharges, the growth in urbanization, and industrial activities in coastal areas are severe threats to the safety of the coastal environment and aquatic ecosystems. Among the existing pollutants in the sewage, heavy metals can be mentioned, especially the ones that play important roles in society as the main raw materials for many industries. (Zhuang and A R T I C L E I N F O: Article history: Received 2 August 2017 Accepted 10 August 2017 Available online 12 October 2017 Keywords: Sediment quality; Toxicity; heavy metals; Shadegan wetland. *Corresponding Author: Department of Environmental Science, Faculty of Natural Recourses and Environmental Science, Malayer University, Iran, E-mail address: mortazavi.s@gmail.com This work is licensed under a Creative Commons Attribution - NonCommercial - NoDerivs 4.0. "CC-BY-NC-ND" JOURNAL OF CONTEMPORARY URBAN AFFAIRS, 1(3), 67-72/ 2017 Samar Mortazavi, Mohsen Tizhoosh, Zahra Cheraghi 68 Gao, 2014; Caerio, et l, 2005) Some, such as copper and zinc, play a vital role in the metabolism of the human body. However, in high concentrations, they turn into toxic substances. Being attributable to high persistence toxicity, solubility low absorption and accumulation in the bottom sediments, heavy metals cause contamination in aquatic environments. (Caerio, et al., 2005) The biological toxicity and bio-magnification in food chains have made the issue of heavy metals a significant global problem. (Förstner and Wittmann, 1983) the ways to clean up contaminated sediment are mostly costly, and in some cases impossible. Hence, the evaluation of sediment contamination in the aquatic environment, identifying sources of pollution, applying management policies, and processes to reduce a number of pollutants into the aquatic environment is more important than focusing on clearing techniques. Many studies have been done in this regard, among which the one carried out by Zarezadeh and Rezai, (2014) can be mentioned through which they have investigated the heavy metals in the sediments bed of mangroves Khurgabrik in Jack Port involving Molar coefficient, the degree of reformed contamination, and ecological risk assessment index. Vaezi et all, (2014) have investigated Mollar environmental index, pollution load, ecological toxicity in sediments in Mosa Firth, Persian Gulf. Chai et al., (2016) explored heavy metal pollution in river sediments in Serbia by calculating the pollution load index and ecological risk assessment. Chai and et al. Sakan and Dordevic, (2015) examined the index of enrichment, molar and ecological risk assessment in Xiangjiang River sediments. In the present study, the types of sediment geochemical index have been determined. Moreover, the ecological risks have been assessed, and ecological toxicity of sediments with heavy metals, namely lead, zinc and copper have been analyzed. The results have been compared with the standards of NOAA and SQG, respectively. 2. Materials and Methods 2.1Area of study The Shadegan Wetland with an area of approximately 400,000 hectares in the range of coordinates 48 degrees 17 minutes and degrees 50 minutes east, 30 degrees 17 minutes 30 degrees and 58 minutes north is located in Khuzestan province, Iran, and has been recognized as an international wetland in the Ramsar Settlement in 1972. (Nasirian et al., 2015) Figure 1. The location of the Shadegan wetland (left) [Source: Google map], and the locations of the sampling stations within the wetland (right). 2.2 Sampling and Preparing Samples As per available access points, a sampling of surface sediments was carried in 10 stations with three replications and recording the geographic coordinates (table 1). For the purpose of preparation, the sediment samples were dried in an oven at a temperature of 105° C. Then, they were crushed in a stone mortar and screened by a 63-micron sieve. For the acid ingestion of sediments, Direct Aqua Regia was employed, following the ingestion; with the contribution of double distilled water in a 25 mL volumetric flask, the volume was delivered. (Yap et al., 2012) To ensure the accuracy of ingestion and elimination of errors Table 6. The results of heavy metal pollution in sediments of the Shadegan wetland. Cd MCd 10 9 8 7 6 5 4 3 2 1 St.No 11.08 1.11 1.04 0.96 1.04 1.20 1.15 1.14 1.20 1.15 1.20 1.00 Pb Cf 4.28 0.43 0.48 0.47 0.43 0.39 0.45 0.43 0.402 0.38 0.43 0.42 Cu 2.90 0.29 0.29 0.35 0.29 0.28 0.30 0.30 0.29 0.25 0.28 0.31 Zn - - 0.52 0.55 0.51 0.51 0.54 0.53 0.52 0.47 0.52 0.51 PLI - - 7.89 7.46 7.64 8.23 8.30 8.15 8.44 7.90 8.43 7.41 RI - - 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.07 0.08 0.08 m-ERM-Q 5. Discussion and Conclusion Investigating the mean concentrations of heavy metals in wetland sediments indicates that Zn> Pb> Cu. The mean concentration of Zn and Cu compared to the permissible concentration of these metals in a global average is lower, and the mean of lead is higher than the average global of the Earth’s crust. The cause of this can be the contamination of the sediments to these metals resulting from the discharge of industrial sewage at the sampling stations which is in line with the findings of Hatefi et al, (2016) and Mohammad Saleh et al, (2012) The Cp index results for 1<Pb<3 indicate that the average contamination in Shadegan wetland is in accordance with the results of Chandramohan studies. (Chandramohan, 2016) In this regard, Zn and Cu content is less than 1 which indicates their low pollution in the place. As it was mentioned in the results section, the pollution index coefficient results (Cf) was less than 1 in all stations for copper and zinc. Hence, they are places in the first category with a low degree of contamination. The results of a lead pollutant index factor were those of average pollution in all stations except for the ninth station; this may be due to the practical usage of this station, which is a small agricultural area. The results are in line with the findings of Mohammad Saleh et al, (2012) and Hatefi et al,(2016) Moreover, based on the results obtained from pollution index factor (Cd), Zn and Cu are ranked first as the two low pollution factors; the Cd factor of lead holds the second rank and has an average pollution factor, a finding which is consistent with the reports of Gholam Dokht Bandari et al,(2015) The obtained mCd index for Zn, Cu, and Pb revealed that all these metal elements are of very low pollution factors; the findings on Zn are similar to those of Zarezadeh and Rezaei,(2014) the results of Cu and Pb are in line with numbers of Gholam Dokht Bandari and Rezaie,(2015) studies. The index rate of PLI of all the stations was less than 1 which is indicative of pollution-free nature of the sediments there; this is consistent with the results found by Chandramohan et al, (2016) and Mohammad Saleh et al, (2012). The ecological risk index shows that, in all stations, the numerical results were less than 150 and that the stations exhibited low ecological risks; this was in harmony with Zarehzadeh and Rezaei, (2000). Compared with the existing standards of the U.S. and Canada, the results of the present study are representative of low- or non-toxic nature of the sediments for the living organisms in all the stations with low-toxic ratios. 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