Environ Geol (2008) 53:1413–1419 DOI 10.1007/s00254-007-0750-6
ORIGINAL ARTICLE
Distribution of trace elements in the coastal sea sediments of Maslinica Bay, Croatia Nenad Mikulic Æ Visnja Orescanin Æ Loris Elez Æ Ljiljana Pavicic Æ Durdica Pezelj Æ Ivanka Lovrencic Æ Stipe Lulic
Received: 17 January 2007 / Accepted: 28 March 2007 / Published online: 26 April 2007 Ó Springer-Verlag 2007
Abstract Spatial distributions of trace elements in the coastal sea sediments and water of Maslinica Bay (Southern Adriatic), Croatia and possible changes in marine flora and foraminifera communities due to pollution were investigated. Macro, micro and trace elements’ distributions in five granulometric fractions were determined for each sediment sample. Bulk sediment samples were also subjected to leaching tests. Elemental concentrations in sediments, sediment extracts and seawater were measured by source excited energy dispersive X-ray fluorescence (EDXRF). Concentrations of the elements Cr, Cu, Zn, and Pb in bulk sediment samples taken in the Maslinica Bay were from 2.1 to over six times enriched when compared with the background level determined for coarse grained carbonate sediments. A low degree of trace elements leaching determined for bulk sediments pointed to strong bonding of trace elements to sediment mineral phases. The
N. Mikulic Ministry of Environmental Protection, Physical Planning and Construction, Ulica Republike Austrije 20, 10000 Zagreb, Croatia V. Orescanin (&) I. Lovrencic S. Lulic Laboratory for Radioecology, Rudjer Boskovic Institute, Bijenicka Cesta. 54, 10002 Zagreb, Croatia e-mail:
[email protected] L. Elez Ministry of Culture, Administration for Protection of Nature, Runjaninova 2, 10000 Zagreb, Croatia L. Pavicic D. Pezelj Department of Geology and Palaeontology, Faculty of Science, University of Zagreb, Horvatovac 102a, 10000 Zagreb, Croatia
analyses of marine flora pointed to higher eutrophication, which disturbs the balance between communities and natural habitats. Keywords Marine sediments Trace elements EDXRF Pollution
Introduction The influence of almost 200 years of harbour activity in the Maslinica Bay and release of untreated sewage wastewaters on the quality of sediments and marine flora was investigated. The Maslinica Bay is situated in the western part of the Solta Island in the middle Adriatic Sea (Fig. 1). It is connected with the open sea through a narrow mouth of 360 m width. Depth of the bay ranges from 1 to 21 m. The lithology of the researched area is quite uniform and is represented with a few varieties of carbonates. These are mostly limestones and calcareous dolomites, and to the lesser extent, dolomitic limestones and dolomites. Chert is also documented in some limestones. As a result of intensive chemical weathering of carbonate sediments under the influence of precipitation water, a terra rossa is formed. This deposit covers a relatively small area of the Solta Island (Marincic et al. 1971). The village of Maslinica is situated on the coast and was founded in eighteenth century. At present, 174 Maslinica residents are oriented towards fishing and tourism. The number of inhabitants more than doubles every summer because of the tourist activity. Major sources of pollution are assumed to be sewage waste (due to absence of public sewage system) and trace elements released from the antifouling paints applied on the ships in the local port built in the 19th century.
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Fig. 1 Location map of the study area and sampling points
Antifouling paints are the major anthropogenic source of trace elements in the coastal sea sediments in the vicinity of ports and marinas (Novelli et al. 2002; Orescanin et al. 2002, 2003; Colson and Hughes 2004; Inoue et al. 2004; Mikulic et al. 2004; Devier et al. 2005). These paints are used for the coating of underwater parts of the boats in order to prevent growth of algae, microorganisms and small invertebrates. As an active substance in the paints, tributyltin (TBT) or other trace elements compounds like Cu2O were used. Use of antifouling paints caused serious environmental pollution and damage to marine organisms. Harmful effects varied from genetic damages to the local extinction of certain species. As a result of all those findings most of the countries regulated the use of hazardous substances, especially organotin compounds in the antifouling paints (Champ 2000). Croatia is one of the countries where the use of all those paints is allowed and still contributes to pollution of the Adriatic Sea.
Materials and methods Physical and chemical characterisation Sediment samples were taken at 21 locations: six control samples (C) (samples 1–6), seven samples in the Maslinica Bay outside of the local port (MB) (samples 7–13) and eight samples inside the local port (P) (samples 14–21) (Fig. 1). At each location about 1 kg of sample was taken with a grab sampler, put into a plastic box and transported to the laboratory. Each sample was mixed thoroughly and divided into sub-samples. 100 g of sub-sample was dried at
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105°C in a drying oven, disaggregated in an agate mortar and prepared for determination of the total elemental composition by pressing approximately 2 g of powdered sample into pellet. Second sub-sample (app. 300 g of wet sediment) was wet sieved using Retsch (DIN-ISO3310/1) sieves to six size fractions (2 mm) and then each fraction was dried at 105°C in a drying oven and weighted. The fractions 63 lm) and approximately 300 individuals of benthic foraminifera were picked; counting was completed for planktonic foraminifers and ostracods. Taxonomic analyses were based on the Loeblich and Tappan (1988) and Bonaduce et al. (1975) classifications.
Fig. 2 Granulometric composition of the Maslinica Bay sediment. C control samples, MB samples taken in the vicinity of local port, P sediments sampled inside the local port
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to a possible trace metal pollution, concentrations of trace elements measured in the port sediments were compared with background values determined for Punat Bay sediment B (Orescanin et al. 2002) which has similar granulometric composition and origin as investigated sediments. As shown in Table 1, enrichment over background values ranged from 1.2 times for Mn to over six times in the case of Cr. Granulometric characteristics are one of the most important factors controlling the concentrations of trace elements in sediments. Finer-grained fractions and their associated sediment phases have a higher proportion of trace elements more often than the coarse-grained sediments, which are connected with larger surface area of smaller particles. Dependence of concentrations of the elements Pb, Ca, Fe, Cu and Zn on granulometric composition of the sediments is presented in Fig. 4. Only Ca concentrations showed decrease with the increasing content of fine-grained fraction. All the other elements showed the opposite pattern. The highest, almost linear increase in the fine-grained fraction (
