Spatial distribution, enrichment, and source of environmentally important elements in Batticaloa lagoon, Sri Lanka

Abstract

The present paper is the first documentation of distribution and contamination status of environmentally important elements of superficial sediments in the Batticaloa lagoon that is connected to the largest bay of the world. Surface sediment samples were collected from 34 sites covering all over the lagoon. Concentrations of elements such as As, Cr, Cu, Fe, Nb, Ni, Pb, Sc, Sr, Th, V, Y, Zn, and Zr were measured by Xray florescence analysis. Geochemically, the lagoon has three different zones that were influenced mainly by fresh water sources, marine fronts, and intermediate mixing zones. The marine sediment quality standards indicate that Zr and Th values are exceeded throughout the lagoon. According to the freshwater sediment quality standards, Cr levels of all sampling sites exceed the threshold effect level (TEL) and 17 % of them are even above the probable effect level (PEL). Most sampling sites of the channel discharging areas show minor enrichment of Cu, Ni, and Zn with respect to the TEL. Contamination indices show that the lagoon mouth area is enriched with As. Statistical analysis implies that discharges from agricultural channel and marine fluxes of the lagoon effects on the spatial distribution of measured elements. Further research is required to understand the rate of contamination in the studied marine system. Keywords Spatial distribution . Heavy metals . Enrichment . Sediment quality assessment . Batticaloa lagoon . Sri Lanka Introduction Spatial distribution and concentration of heavy metals and other environmentally important elements in large-scale coastal aquatic environments are influenced by natural and anthropogenic factors (Gao and Chen 2012; Dou et al. 2013; Maanan et al. 2015). Major natural environmental factors include weathering and erosion of source rocks, river, marine fluxes, and biogenic influences. Major anthropogenic factors include industrial, agricultural, and domestic wastewater discharges and shrimp and fish farming effluents (Selvaraj et al. 2004; Fujita et al. 2014; Syakti et al. 2015). Heavy metals collected in aquatic bodies are mobilized by water fluxes and finally, they sink and accumulate in the bottom of coastal aquatic environments such as lagoons, estuaries, or continental shelf areas (Yeats and Bewers 1983). The low solubility, toxicity, wide sources, and bioaccumulation behavior of heavy metals and other toxic elements cause serious problems on the environment and aquatic biology and simultaneously on human health through the food chains (Munksgaard and Parry 2002; Yu et al. 2008). Therefore, it is necessary to investigate and monitor the temporal and spatial distribution and concentration of such elements in bottom sediments of coastal aquatic sediments (Bryan and Hummerstone 1977). The coastal zone of eastern Sri Lanka faces the largest bay of the world, Bay of Bengal. The northern part of the eastern coast is world famous for its valuable heavy mineral deposits such as ilmenite, zircon, and rutile. However, so far, no studies Responsible editor: Philippe Garrigues * Madurya Adikaram maduryaa@gmail.com 1 Department of Physical Sciences, Faculty of Applied Sciences, South Eastern University, Sammanthurai, Sri Lanka 2 Department of Geology, Faculty of Science, University of Peradeniya, Peradeniya, Sri Lanka 3 Department of Geosciences, Graduate School of Sc. and Eng, Shimane University, Matsue, Japan 4 Department of Forestry and Envt. Sc, Sri Jayawardhanapura University, Nugegoda, Sri Lanka Environ Sci Pollut Res DOI 10.1007/s11356-016-7973-6have been conducted on contamination of heavy metals and other toxic metals in the eastern coastal aquatic bodies. Hence, the present study focuses on spatial distribution and concentrations of some environmentally important elements in the superficial sediments of a large semi-enclosed lagoon in eastern Sri Lanka. It also includes an interpretation of contamination status and probable sources of such elements. This work provides a baseline study for the status of contamination in a large-scale lagoon of southeastern Asia.