Occurrence and possible fate of organochlorine pesticide residues at Manzala Lake in Egypt as a model study Essam Kamel, Saad Moussa, Mostafa A. Abonorag & Muhsin Konuk
Environmental Monitoring and Assessment An International Journal Devoted to Progress in the Use of Monitoring Data in Assessing Environmental Risks to Man and the Environment ISSN 0167-6369 Volume 187 Number 1 Environ Monit Assess (2015) 187:1-10 DOI 10.1007/s10661-014-4161-3
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Author's personal copy Environ Monit Assess (2015) 187:4161 DOI 10.1007/s10661-014-4161-3
Occurrence and possible fate of organochlorine pesticide residues at Manzala Lake in Egypt as a model study Essam Kamel & Saad Moussa & Mostafa A. Abonorag & Muhsin Konuk
Received: 12 July 2014 / Accepted: 10 November 2014 / Published online: 26 November 2014 # Springer International Publishing Switzerland 2014
Abstract Persistence of the residue of organochlorine pesticides (OCPs) became a great danger to our environment long ago. In this study, the persistence of OCPs at Manzala Lake in Egypt was determined. Four different sites were investigated: the El-Gamel, El-Kowar, ElRasoah, and Janb El-Timsah regions. Among these, the El-Kowar region had the highest concentration of total OCPs in the sediment samples when compared to other regions during both 2012 and 2013. In fact, generally, the residues of OCPs in the sediment samples were significantly higher in all tested sites in comparison with other compartments. Conversely, OCP residues were undetectable in water samples at both the El-Gamel region and the El-Rasoah site in the studied seasons. The data proved that the sediment layer plays a sourcing role in OCP persistence in the aquatic ecosystem. Data analysis also indicated that there was an external source for OCP contamination in the Manzala Lake ecosystem E. Kamel : M. A. Abonorag Biochemistry and Toxicology Department, Animal Health Research Institute, Giza, Dokki, Egypt S. Moussa Insect Molecular Biology and Biotechnology Unit, Plant Protection Research Institute, Giza, Dokki, Egypt M. Konuk (*) Faculty of Engineering and Natural Sciences, Molecular Biology and Genetics Department, Üsküdar University, Altunizade 34662 Istanbul, Turkey e-mail: [email protected]
M. Konuk e-mail: [email protected]
that most likely comes from Nile Basin countries and which extends the expected half-life of these compounds. It could be exemplified by DDT, the half-life of which increased from 30 to approximately 47 years. Keywords OCP . Persistence . Half-life . Aquatic ecosystem
Introduction Manzala Lake covers nearly 3 % of the non-desert surface area of Egypt and is located near the Mediterranean coast of the Delta region. It represents the main meeting point of several polluted water resources and is considered to be the most important natural resource for fish production in Egypt. It provides more than 7 % of the country’s total fish production (GAFRD 2006). Water is considered an essential resource not only for human life but for all living organisms on Earth. Therefore, studying and analyzing water ecosystem compartments have become a primary concern for the health of human beings. In the 1940s, organochlorine pesticides (OCPs) were introduced as the first important synthetic organic pesticides used to minimize pest attacks. During the 1970s, OCPs were banned in developed countries (Cruz et al. 2003), and the Ministry of Agriculture in Egypt banned them in the 1980s (Dogheim et al. 1996). However, their residues persist to this day in the environment, especially in the
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aquatic ecosystem, posing a serious threat to its aquatic organisms, including fish. It is well known that OCPs have low polarity, low aqueous solubility, and high lipid solubility (lipophilicity), so they have the potential to accumulate in the food chain, creating a grave threat to humans and other untargeted organisms (Afful et al. 2010). The World Health Organization (WHO) has announced that organochlorines have been found to be carcinogenic compounds in animal models (Shakeel et al. 2010). These characteristics (the temporal concordance of their widespread usage and extended half-life) are found in combination with increasing rates of breast cancer in coastal areas. This stimulated the hypothesis that exposure to OCPs may cause breast cancer. Screening of the available literature reveals that OCPs create a continuous health hazard to all living organisms, including humans, animals, birds, and aquatic creatures (Taylor et al. 1988; Pardio et al. 2012). The significant threat of such compounds even while controlling insecticides is based on their persistence in the environment (El-Mekkawi et al. 2009) and their ability to be transferred by movable water from one area to another. Thus, the current study aims to assess the degree of contamination and to calculate the possible half-life of OCP compounds in water, sediment, aquatic weeds, and fish at four different locations of Manzala Lake (the El-Gamel, El-Kowar, ElRasoah, and Janb El-Timsah regions) during the switching seasons of October 2012 and March 2013.
Fig. 1 The Global Positioning System (GPS) map of Delta region of Egypt illustrates the sites of collected samples during the study, viz., El Gamel, El-Kowar, Bughas El-Rasoah, and Janb El-Timsah regions
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Materials and methods Sampling collection The Manzala Lake has two outlets to the Mediterranean Sea that allow seawater to flow in and out of the lake. Samples were collected from four regions that represent the different environmental conditions in the lack. In order to determine the persistence of OCP compounds in the lake, four ecosystem components were investigated: water, sediment, aquatic weeds, and fish. Simple random sampling technique was taken from four locations of the lake. These were the El Gamel region, a nature reserve area at the eastern end of a sandbar that separates the lake from the Mediterranean Sea; the ElKowar region (at international Mediterranean Sea coastal road); the Bughas El-Rasoah site (Manzala outlet to the sea); and the Janb El-Timsah region (Fig. 1). The samples were collected two times during a 1-year period (October 2012 and March 2013) as described below. Water samples The water samples were collected and prepared according to the method described by Myers (2006). Samples of 2.5 l of water were taken at a 50-cm depth from the water surface and kept in 3-l-capacity glass bottles. These were covered with screw-on plastic caps and immediately transported to the laboratory for analysis. The water samples were filtrated through a cotton funnel in order to remove debris. The filtrated water samples were then kept at 4 °C until further analysis.
Author's personal copy Environ Monit Assess (2015) 187:4161
Sediment samples Samples of 2 kg of sediment were taken using tube core sampler at a depth of 5 cm from the sediment soil surface. Water was removed from the sediment samples by decantation, and the sediment was then transferred to the laboratory. Samples were allowed to dry at room temperature for 48 h before analysis (ASTM 2010). Aquatic weed samples One kilogram of aquatic weed samples consisting of bulrush millet (Pennisetum glaucum) was examined for the presence or absence of OCP residues. The aquatic weed samples were obtained by dropping a weighted rake into the water and pulling up the vegetation that was snagged by the rake. The weeds were removed from the rake and stored in a shallow pot filled with clean water in order to keep them alive. The weeds were then placed in plastic bags and sealed securely. Weed samples were usually kept for 5 days in a fresh mode without any changes (Parsons 2001). Fish samples An amount of 2–2.5 kg of healthy, vigorous tilapia fish (Tilapia nilotica) were caught by local fishermen from the above mentioned sites and transferred directly to the laboratory. The soft parts of each fish were obtained by removing 10 g of dorsal muscle tissue. The muscle tissues were kept at −20 °C until further analysis (UNEP 2007). Analytical procedures Sample preparation and residue analysis Water, sediment, aquatic weed, and fish samples were prepared, and the pesticide residues were extracted according to the methods described by APHA (1975), Leyva-Cardoso et al. (2003), UNEP/IOC/IAE (1991), and IOC (1993), respectively. Sample cleanup The extracted samples were cleaned and fractionated according to the method described by UNEP (1988). The residue was dissolved in 2 ml of n-hexane and
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transferred into an autosampler vial for GC-electron capture detection (ECD) analysis. The extract was concentrated and injected into GC (Aglient 6890) equipped with a 63Ni ECD, a split/ splitless injection inlet, capillary column capability, and a 7683A autosampler. Chemistation software was used for instrument control. GC analysis was conducted on a HP-5MS (Aglient, Folsom, CA) capillary column of 30 m, 0.25 mm i.d., and 0.25-μm film thickness. The oven temperature was programmed from an initial temperature of 160 (2-min hold) to 240 °C at a rate of 5 °C/min and was maintained at 240 °C for 20 min. Injector and detector temperatures were maintained at 260 and 320 °C, respectively. Nitrogen was used as a carrier at flow rate of 3 ml/min.
Quality control The analytical quantitation was achieved exploring the internal standard calibration technique at different point calibrations, viz., 0.001, 0.01, 0.1, 1, and 10 ppb. The calibration curve correlation coefficients (r2) were higher than 0.9946. The obtained results were checked for accuracy and precision. Limit of detection (LOD) was calculated according to the following equation: LOD ¼
where SD represents the standard deviation for five replicate standard points and S represents the slope of the calibration curve. The LOD of OCs ranged from 0.001 to 0.002 ppb. The OC standards were added to four types of the studied samples and recoveries were ranged from 87 to 96 %. In each of the 10 batch samples, a blank (solvent), a spiked blank (standards + solvent), and a matrix spike (standards spiked + pre-extracted samples) were prepared, and each sample was analyzed two times. The recoveries in the spiked blanks and matrix spikes samples were varied (86–99 %) for OCs. The blank samples were run sporadically and did not contain any detectable amount of OCs. The variance coefficients of OCs concentration were less than 15 % in each duplicate sample. The scheme of quality control was periodically analyzed for OCPs and standard mixture including spiked blank along with the tested samples. An identified amount of pesticide standard samples was checked for accuracy routinely.
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Statistical analysis One-way analysis of variance (ANOVA) was followed by the Duncan multiple range test for comparison of means at P