Elsevier

Chemosphere

Volume 90, Issue 9, March 2013, Pages 2467-2476
Chemosphere

Persistent organochlorine pesticide and PCB residues in surface sediments of Lake Qarun, a protected area of Egypt

https://doi.org/10.1016/j.chemosphere.2012.11.012Get rights and content

Abstract

Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) were determined in sediment samples collected from 34 locations in Lake Qarun, Egypt to elucidate their concentrations, distribution, possible sources and potential ecological risk. A total of 25 OCPs and 29 PCBs were identified and quantified. OCPs and PCBs were found to be ubiquitous pollutants in the aquatic environment of Lake Qarun, particular near urban areas reflecting the local usage and input of these pollutants. Total concentrations of OCPs and PCBs in sediments ranged from 1.01 to 164.8 ng g−1 and 1.48 to 137.2 ng g−1, respectively. Among OCPs, γ-HCH, heptachlor, aldrin, endrin, p,p′-DDE, oxy-chlordane and endosulfan I and II were the most abundant compounds. The composition of PCB congeners was dominated by the tri-, tetra-, penta- and hexa-chlorinated biphenyls. The ratios of certain metabolites (isomers) to their parent compounds (mixtures) indicated there are still new inputs of lindane, endrin, heptachlor and technical endosulfan to Qarun Lake, while the ratios of (p,p′-DDE + p,p′-DDD)/∑p,p′-DDTs indicate earlier usage of DDT. Contamination levels of PCBs and HCHs can be categorized as moderate to high compared to other urbanized regions worldwide. According to established sediment quality guidelines, γ-HCH, endrin and chlordanes would be more concerned OCP species for the ecotoxicological risk in Lake Qarun.

Highlights

► High levels of OCs were found at sites near wastewater discharges. ► Ubiquitous contaminants were endrin, γ-HCH, aldrin, CHLs, and endosulfan. ► The composition of DDT and its metabolites suggest old input of DDT. ► Levels of OCs were low to moderate compared to other locations worldwide. ► Areas of expected potential ecotoxicological risk were identified.

Introduction

Persistent organic pollutants (POPs) such as organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs), are ubiquitous pollutants in the environment that have caused worldwide concern. For several decades, these compounds have been produced and extensively used world-wide for various applications in industry and agriculture. Many organochlorines have been implicated in a broad range of adverse human health and environmental effects, including impaired reproduction, endocrine disruption, immuno suppression and cancer (Colborn et al., 1993, El-Shahawi et al., 2010). Because of their persistent, semivolatile and bioaccumulative nature, long-range transport and biological effects in the environment, they are restricted or banned globally under the Stockholm Convention on Persistent Organic Pollutants (Stockholm Convention, 2001, Stockholm Convention, 2009).

Sediments act as a sink for POPs brought into the aquatic environment from direct discharges, surface run-off and atmospheric fall out. These and other chemicals may enter aquatic systems through direct/indirect discharge, surface run-off and atmospheric deposition. From such sinks, POPs and their residues can enter living organisms, via flux through the water phase, and eventually bioaccumulated in sediment-dwelling organisms and edible fish (e.g., Licata et al., 2003, Chau, 2005). Therefore, the distribution of POPs in sediments and biota can serve as a useful index of pollution and potential environmental risks.

With the rapid development of agriculture and industry in Egypt, OCPs an PCBs and have been detected in various biotic and abiotic environmental compartments (e.g., Barakat, 2003, Barakat, 2004, El-Kady et al., 2007, Mansour et al., 2009, Khairy et al., 2012, Barakat et al., 2012a). In Egypt, uses of organochlorine pesticides began in the 1950s and were extensively used until 1981 to protect crops from insects, disease fungi and weeds, to remove unwanted vegetation and to control insects by the general public. The reported total active ingredients of major organochlorine pesticides during a 30-year period are as follows: toxaphene 54,000 mt (1955–1961), endrin 10,500 mt (1961–1981), DDT 13,500 mt (1952–1971) and lindane 21,000 mt (1952–1978) (El-Sebae et al., 1993). The main use of these organochlorine insecticides was the control of insects, specially the cotton leafworm and bollworms in extensive agricultural production. Based on the reports of their harmful effects to wildlife and humans, organochlorine pesticides were banned or restricted from use or trade since 1988 and prohibited in Egypt by a Ministerial Decree in 1996. However many of these contaminants have long environmental half-lives, on the order of 10–20 years, and may continue to be detected for many years (Jones and Voogt, 1999). Most studies that examined the POPs in sediment were from marine and estuary environment, and little information is available on POPs contamination in sediment from inland lakes in Egypt (Barakat, 2004).

Lake Qarun lies in the Faiyum Depression at the margin of the Western Desert of Egypt, about 80 km to the southwest of Cairo, and covers an area of 226 km2. It is an enclosed, saline, inland lake, 40 km in length, 5.7 km in width and 43 m below mean sea level. It is a shallow lake with a mean depth of 4.2 m (Baioumy et al., 2011). Lake Qarun is the third largest lake in Egypt and one of the oldest lakes in the world. It is the existing remnant of the ancient prehistoric lake (Moeris Lake) that was over 75 m deep and covered more than 2000 km2 of the Faiyum Depression (Shafei, 1960). It is rich in both natural and archaeological resources because of the presence of marine, fluvial and continental environment that goes back to some 40 million years. The lake receives the agricultural and sewage drainage water from Faiyum Province and the neighboring cultivated lands. Most of the drainage water reaches the lake through two main drains, El-Batts at the northeastern corner and El-Wadi near mid point of the southern shore, and two pump stations (Fig. 1). Although Lake Qarun is designated as protected area in 1989, the lake is suffering from serious water pollution problems due to uncontrolled solid and liquid domestic and industrial waste disposal practices, in addition to agrochemical contamination and lack of sustainable wastewater management (Hussein et al., 2008). Studies on the environmental health of Lake Qarun in Egypt have concentrated in the past mostly on inorganic chemical analysis of different ecosystem components (e.g., Saleh et al., 1988, Saleh et al., 2000, Mansour and Sidky, 2003, Hussein et al., 2008). Data from these studies showed that Lake Qarun is effected by pollution from industrial and agricultural waste disposal. Except for a limited study (Mansour and Sidky, 2003), which dealt with number of OC pesticide residues in sediments from three locations from the lake, no further information is yet available on the distribution and sources of OCs in this important ecosystem. The objectives of this work are to provide a survey of the concentration levels, distributions and sources of PCBs and OCPs in surface sediment samples from Lake Qarun and to assess their environmental risks in this basin. Compounds measured included 29 PCB congeners (PCB-8, 11, 18, 28, 44, 52, 66, 77, 81, 101, 105, 114, 118, 123, 126, 128, 138, 153 156, 157, 167, 169, 170, 180, 187, 189, 195, 206 and 209); o,p′-DDT, p,p′-DDT and degradation products o,p′-DDD, p,p′-DDD, o,p′-DDE and p,p′-DDE; chlordane related compounds (heptachlor and its epoxide, oxy-, cis- and trans- chlordane, trans-nonachlor); hexachlorobenzene (HCB); α-, β-, γ-, and δ-HCH; cyclodiene pesticides (aldrin, dieldrin, endrin, endrin aldehyde, endrin ketone, endosulfan I, II, and endosulfan sulphate) and methoxychlor. To our knowledge, this is a first comprehensive study to report on the concentrations of OCPs and PCBs in environmental samples from Lake Qarun and provide baseline data for future research on environmental occurrence and bioaccumulation of these compounds in the study area.

Section snippets

Study area and sampling

Thirty-four sites throughout the lake were sampled in January 2011 to analyze the contents of PCBs and OCPs in the surface sediments. The sampling stations were selected as such to cover areas affected by agricultural and sewage drainage water from Faiyum Province and the neighboring cultivated lands, and included the outfalls of the El-Wadi and El-Batts drains and the two pumping stations in the south and the southwest areas of the lake (Fig. 1). Approximately top 0–5 cm of sediment was

Organochlorine pesticides

Concentrations of organochlorine pesticides in surface sediments from Lake Qarun are shown in Table 1. Endrin was the most abundant compound in the sediment samples, followed by HCHs, CHLs, aldrin, and endosulfans. Other OCPs such as DDTs, HCB, dieldrin, endrin aldehyde, endrin ketone, and methoxychlor were found at lower concentrations. The concentrations of different OCPs had different spatial distribution. The significant difference observed among the locations may be attributed to different

Conclusions

The present study assessed the levels, distribution and toxicological potential of OCs in sediments from various areas of Lake Qarun, and add to the scarce knowledge of their environmental distribution in lake sediments from Egypt. Due to a diversity of potential inputs from sources such as industry, wastewater and sewage discharges, as well as agricultural runoff from the surrounding drains, PCBs and OCPs contaminants are ubiquitously distributed in sediments from Lake Qarun. The highest

Acknowledgments

The authors are grateful to Alexandria University (Egypt) for providing financial support to this study. We are indebted to two anonymous referees for their valuable comments and suggestions.

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