Int. J. Aquat. Biol. (2021) 9(6): 388-392 ISSN: 2322-5270; P-ISSN: 2383-0956 Journal homepage: www.ij-aquaticbiology.com © 2021 Iranian Society of Ichthyology Short Communication Alkanes in the sediments of Al-Gharraf River, Southern Iraq Shaimaa Talib Abedali* 1, Snaa Talib Jawed2, Wesan Fadhel Khalef3 1Department of Biology, College of Education for Women, University of Thi Qar, Thi Qar, Iraq. 2Department of Biology, College of Education for Pure Sciences, University of Thi Qar, Thi Qar, Iraq. 3Department of Biology, College of Sciences, University of Thi Qar, Thi Qar, Iraq. s Article history: Received 20 September 2021 Accepted 217 December 2021 Available online 2 5 December 2021 Keywords: Petroleum Anthropogenic Biogenic Gas chromatography Abstract: The study aimed to determine the concentrations of alkanes compounds using a gas chromatograph with high-precision separation techniques. Samples were collected from four stations in the Al-Gharraf River in southern Iraq during 2018-2019. A seasonal variation was observed in the concentrations of alkanes, which is the highest in the winter. The total alkanes concentrations were the lowest at 0.079 μg/g at station 1 in summer. The highest total concentration of alkanes was in station 3 in winter reaching 2.215 μg/g. There was a dominance of individual carbon compounds of C17, C19, and C21 indicating the source of hydrocarbon from phytoplankton, plant, and bacteria. The presence of carbon compounds higher than C25 reveals that organic matter is derived from land and aquatic plants. The results also indicate that the source of petroleum hydrocarbons in the sediments of the Al-Garraf River is a common biogenic and anthropogenic based CPI index and the pri/phy guide that was less than 1 in the second and third stations for all seasons, and greater than 1 in the first and fourth stations. Introduction One of the important pollutants in the aquatic environment is petroleum hydrocarbons which affect their living organisms (NRC, 1985). Hydrocarbons enter the aquatic environments through several sources and aquatic organisms absorb them during their feeding; however, the quantity of oil compounds is scare in the aquatic systems (Cajeravelli et al., 1995). The regular alkanes with carbon numbers of C15, C17, and C19 are formed from marine biological sources e.g. phytoplankton; while alkanes with carbon numbers of C33 and C25 are composed of terrestrial vascular plants (Sakari et al., 2008). The presence of high-chain carbon compounds (C25-C30) indicates the presence of flowering plants. The most individual alkane compound found in the sediments of the marshes is C17, which is produced by the sulfur bacterium of Desulfovibrio desulforicans .(AL-Saad and Ali-Timari, 1993) Chromatography is used for detecting the type of pollution and its source, whether it is biogenic or anthropogenic by measuring the carbon preference *Correspondence: Shaimaa Talib Abedali DOI: https://doi.org/10.22034/ijab.v9i6.1497 E-mail: shaimaa.talib@utq.edu.iq coefficient (CPI). CPI is the sum of the odd-numbered carbon compounds to the sum of the concentrations of the even-numbered carbon compounds; if it is greater than one, indicating that the origin of the pollution is biogenic and if less than one, indicates the anthropogenic origin of the pollution, and if its values are close to one shows the common origin (Canton and Grimalt, 1992). The other source of hydrocarbons is oil and its derivatives are made up of a mixture of organic compounds constituting 50-98% of the total oil composition, in addition to other elements such as sulfur, nitrogen, and oxygen (Leighton, 2000). Oil also contains some trace elements such as cadmium (Cd), vanadium (V), nickel (Ni), and cobalt (Co) (Albagies, 1989). Therefore, this study aimed to investigate the pollution of petroleum hydrocarbons in the Al-Garraf River, a tributary of the Tigris River. Materials and Methods The Al-Gharraf River, a tributary of the Tigris River, is located in the southeastern part of Iraq, within the alluvial plain area before the Kut Dam (Ghazi, 2004). 389 Int. J. Aquat. Biol. (2021) 9(6): 388-392 It flows towards the southwest between the Tigris and Euphrates, passing through the Al-Hayy, Qalaat Sukar, Al-figer, Al-Nasr, and Al-Shatra towns. Then it splits into two branches, one of them i.e. Shatt al- Bid’ah ends in the marshes leading to Marsh al- Hammar (Directorate of Water Resources, 2008). Four stations were selected for sampling: the first station (32°08'29.4"N 46°02'38.3"E) in an area characterized by the presence of villages and agricultural lands on both sides that were wide with the high water level, the second station (31°41'21.6"N 46°06'53.9"E) was about 50 km far from the first station, after the river exiting Al-Figer district in about 4 km. The river in this area is characterized by the abundance of water plants and with a narrow width, as well as the presence of villages and agricultural lands, the third station (31°22'50.8"N 46°10'51.0"E) is located after the river exits the city of Shatrah, at a distance of 40 km from the second station. On both sides of the river in this station, there are villages and agricultural lands, with the narrow course less than in the first and second stations, with a decrease in the water level. The fourth station (31°09'55.0"N 46°36'36.6"E) was located at the Islah area near the entrance of the river into the marshes (72 km away from the third station) and characterized by the presence of agricultural land and high water level. Sediment samples were collected from the four stations in four seasons using a Van veen grab and then kept in aluminum foil. Drying the sediment was done by freeze dryer and then they grind with a mechanical mortar and afterward sieved with a metal sieve with 63 µm diameter (Goutx and Saliot, 1982). A gas chromatography device (Hp-Hewlett Packard- 5890, USA) was adopted to determine the concentrations of aliphatic hydrocarbons (alkanes) of the petroleum from sediments in the laboratories of the Marine Science Center, University of Basra. It is Table 1. Total sum and type of n-alkanes (mg/L) in the sediment of the AL-Gharraf River in summer. N-alkane S1 S 2 S 3 S 4 C13 0.003 0.02 0.004 0.003 C14 0.002 0.01 0.005 0.002 C15 0.03 0.002 0.007 0.006 C16 0.002 0.003 0.006 0.004 C17 0.006 0.002 0.013 0.021 C18 0.004 0.083 0.032 0.011 C19 0.005 0.024 0.012 0.042 C20 0.006 0.038 0.035 0.046 C21 0.005 0.003 0.062 0.053 C22 0.003 0.049 0.025 0.032 C23 0.002 0.002 0.024 0.028 C24 0.004 0.032 0.093 0.002 C25 0.002 0.015 0.071 0.043 C26 0.008 0.061 0.102 0.025 C27 0.007 0.052 0.025 0.136 C28 0.004 0.064 0.064 0.102 C29 0.002 0.02 0.092 0.006 C30 0.005 0.025 0.21 0.063 C31 0.007 0.003 0.043 0.003 C32 0.002 0.002 0.009 0.005 C33 0.001 0.002 0.016 0.003 C34 0.002 0.001 0.006 0.002 Sum 0.079 0.513 0.956 0.638 Pristine 0.005 0.072 0.008 0.01 Phytine 0.004 0.095 0.04 0.01 Prstine/phytine 1.25 0.757 0.2 1 Even 0.042 0.368 0.587 0.304 Odd 0.043 0.145 0. 369 0.494 Odd/even 1.023 0.394 0.628 1.625 Table 2. Total sum and type of n-alkanes (mg/L) in the sediment of the AL-Gharraf River in autumn. N-alkane S1 S 2 S 3 S 4 C13 0.002 0.034 0.005 N.D C14 0.002 0.025 0.004 N.D C15 0.001 0.043 0.007 0.021 C16 0.005 0.062 0.003 0.034 C17 0.001 0.093 0.082 0.042 C18 0.071 0.154 0.081 0.032 C19 0.028 0.054 0.095 0.068 C20 0.001 0.012 0.092 0.041 C21 0.011 0.047 0.12 0.052 C22 0.002 0.068 0.098 0.021 C23 0.032 0.084 0.11 0.092 C24 0.003 0.054 0.125 0.074 C25 0.001 0.082 0.095 0.062 C26 0.016 0.074 0.182 0.052 C27 0.085 0.042 0.121 0.063 C28 0.012 0.098 0.21 0.082 C29 0.052 0.024 0.071 0.054 C30 0.001 0.032 0.092 0.023 C31 0.062 0.011 0.021 0.021 C32 0.002 0.021 0.043 0.02 C33 0.041 0.003 0.002 N.D C34 0.003 0.009 0.003 N.D sum 0.434 1.126 1.662 0.854 Pristan 0.084 0.07 0.03 0.062 Phytan 0.06 0.12 0.051 0.054 Pristine/phytan 1.4 0.583 0.588 1.1481 Even 0.118 0.609 0.933 0.379 Odd 0.316 0.517 0.729 0.475 Odd/even 2.6 0.848 0.83 1.253 390 Abedali et al./ Alkanes in the sediments of Al-Gharraf River equipped with a type Hp (3396A) Integrator with injection type of splitless. The type of separation shaft was capillary Column J+W DB5, with a diameter of 0.25 mm and a length of 30 meters. Results and Discussions The total concentrations of total alkanes in the study stations ranged between 0.079 μg/g in the first station in summer and 2.215 μg/g in the third station in winter (Tables 1-4; Fig. 1). There were two types of regular alkanes, first with low molecular weights and others with high molecular weights, and their sources are multiple. Compounds with double carbon atoms such as C16, C18, and C20 indicates the presence of plant and animal plankton and bacteria (Volkmon, 1980) and the presence of carbon compounds more than C25 e.g. C31, C25, C27, and C29 evidence the organic matter is derived from land and aquatic plants (Simoneit, 1993). The results showed that the concentrations of total alkanes in the winter are higher than in summer in all stations since the high evaporation reduces alkanes as well as microorganisms break them into normal alkanes (Al- Saad, 1996). Microorganisms are less active and effective in winter (Douabul et al., 2012). Al-Imarah et al. (2006) studied the seasonal changes in the content of total petroleum hydrocarbons in the water and sediments of the southern Iraqi marshes showing the concentrations ranging 29.12-48.14 µg/g dry weight in its sediment samples and those of ranged 0.6-17.41 µg/L. The concentrations of hydrocarbons also were 0.012 µg/g dry weight in the sediments of Al-Baraka to 0.96 µg/g dry weight in the Al- Baghdadiya sediments (Nasir 2007) and it was also found that the concentrations of hydrocarbons in the water were lower than sediments. The results indicate that most of the CPI values are Table 3. Total sum and type of n-alkanes (mg/L) in the sediment of the AL-Gharraf River in winter. N-alkane S1 S 2 S 3 S 4 C13 0.002 0.004 0.004 0.008 C14 0.003 0.005 0.002 0.009 C15 0.023 0.007 0.074 0.019 C16 0.018 0.006 0.002 0.063 C17 0.082 0.002 0.102 0.232 C18 0.096 0.003 0.126 0.181 C19 0.092 0.012 0.075 0.173 C20 0.082 0.027 0.097 0.123 C21 0.065 0.042 0.041 0.176 C22 0.043 0.052 0.095 0.092 C23 0.086 0.026 0.086 0.163 C24 0.094 0.092 0.178 0.102 C25 0.092 0.071 0.093 0.103 C26 0.043 0.182 0.162 0.098 C27 0.096 0.178 0.086 0.146 C28 0.085 0.043 0.198 0.088 C29 0.0 89 0.064 0.093 0.096 C30 0.083 0.143 0.173 0.073 C31 0.032 0.013 0.063 0.022 C32 0.021 0.001 0.172 0.01 C33 0.032 0.112 0.021 0.003 C34 0.021 0.002 0.031 0.006 sum 1.28 1.66 2.215 1.988 Pristane 0.046 0.012 0.062 0.062 Phytane 0.015 0.082 0.076 0.193 pristane/phytane 3.06 0.14 0.815 3.112 Even 0.589 0.55 1.236 0.839 Odd 1.091 0.531 0.738 1.138 Odd/even 1.85 0.96 0.597 1.356 Table 4. Total sum and type of n-alkanes (mg/L) in the sediment of the AL-Gharraf River in spring. N-alkane S1 S 2 S 3 S 4 C13 0.002 0.004 0.004 0.008 C14 0.003 0.005 0.002 0.009 C15 0.023 0.007 0.074 0.019 C16 0.018 0.006 0.002 0.063 C17 0.082 0.002 0.102 0.232 C18 0.096 0.003 0.126 0.181 C19 0.092 0.012 0.075 0.173 C20 0.082 0.027 0.097 0.123 C21 0.065 0.042 0.041 0.176 C22 0.043 0.052 0.095 0.092 C23 0.086 0.026 0.086 0.163 C24 0.094 0.092 0.178 0.102 C25 0.092 0.071 0.093 0.103 C26 0.043 0.182 0.162 0.098 C27 0.096 0.178 0.086 0.146 C28 0.085 0.043 0.198 0.088 C29 0.0 89 0.064 0.093 0.096 C30 0.083 0.143 0.173 0.073 C31 0.032 0.013 0.063 0.022 C32 0.021 0.001 0.172 0.01 C33 0.032 0.112 0.021 0.003 C34 0.021 0.002 0.031 0.006 sum 1.28 1.66 2.215 1.988 Pristane 0.046 0.012 0.062 0.062 Phytane 0.015 0.082 0.076 0.193 pristane/phytane 3.06 0.14 0.815 3.112 Even 0.589 0.55 1.236 0.839 Odd 1.091 0.531 0.738 1.138 Odd/even 1.85 0.96 0.597 1.356 391 Int. J. Aquat. Biol. 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