Heavy metal accumulation during the last 30 years in the Karnaphuli River estuary, Chittagong, Bangladesh

Ai-Jun Wang,Yong-Hang Xu,Seema Rani,Ahmed Kawser,Ke-Liang Chen,Xiang Ye

doi:10.1186/s40064-016-3749-1

Ai-Jun Wang, Yong-Hang Xu + Show 4 more

Open Access

https://doi.org/10.1186/s40064-016-3749-1

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Abstract

Heavy metal contamination of aquatic environment has attracted global attention owing to its abundance, persistence, and environmental toxicity, especially in developing countries like Bangladesh. Five heavy metals, namely chromium (Cr), copper (Cu), nickel (Ni), lead (Pb) and zinc (Zn) were investigated in surface and core sediments of the Karnaphuli River (KR) estuary in Chittagong, Bangladesh, in order to reveal the heavy metal contamination history in estuarine sediments and its response to catastrophic events and human activities. The surface sediment was predominantly composed of silt and sand, and the surface sediment was contaminated with Cr and Pb. Based on the 210Pb chronology, the sedimentation rate in the inter-tidal zone of KR estuary was 1.02 cm/a before 2007, and 1.14 cm/a after 2008. The core sediment collected from 8 to 20 cm below the surface mainly originated from terrestrial materials induced by catastrophic events such as cyclone, heavy rainfall and landslides in 2007 and 2008. The values of contamination factor (CF) showed that the sediment became moderately contaminated with Cr and Pb in the last 30 years. The variation and accumulation of heavy metals in core sediment before 2000 was mainly related to natural variations in sediment sources; however, in subsequent years, the anthropogenic inputs of heavy metals have increased due to rapid physical growth of urban and industrial areas in the Chittagong city. In general, the accumulation pattern of heavy metals after normalization to Aluminum in sediments of KR estuary indicated an accelerated rate of urbanization and industrialization in the last 30 years, and also suggested the influence of natural catastrophic event on estuarine environment.

Highlights

A conceptual environmental problem associated with urbanization and industrialization in space and time is the increased heavy metal pollution (Nriagu 1990)
The objectives of this study are to survey the contamination with heavy metals and reveal their accumulation history in the sediment of Karnaphuli River (KR) estuary, and further discuss the results in relation to catastrophic events and human activities
The surface and core sediments were analyzed for grain-size, total organic carbon (TOC) and heavy metals

Summary

Introduction

A conceptual environmental problem associated with urbanization and industrialization in space and time is the increased heavy metal pollution (Nriagu 1990). Due to the special geographic and hydrodynamic characteristics, estuary serves as the main sink for most heavy metals discharged by river system (Dassenakis et al 1995; Ip et al 2004; Zhang et al 2009; Xia et al 2011; Delgado et al 2012; Xu et al 2014), and the estuarine sediment can provide short- or long-term record of the accumulation of trace metal inputs from riverine, atmospheric, and anthropogenic sources (Windom et al 1988; Alexander et al 1993; Ip et al 2004; Delgado et al 2012; Xu et al 2014). The study of heavy metal contamination in estuarine sediment does indicate the environment health issue (Li et al 2007) and reveals information on relevant human activities in the surrounding areas (Delgado et al 2012). The objectives of this study are to survey the contamination with heavy metals and reveal their accumulation history in the sediment of KR estuary, and further discuss the results in relation to catastrophic events and human activities

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