J Soils Sediments DOI 10.1007/s11368-013-0706-2
SEDIMENTS, SEC 1 • SEDIMENT QUALITY AND IMPACT ASSESSMENT • RESEARCH ARTICLE
Spatial patterns and temporal changes of heavy metal distributions in river sediments in a region with multiple pollution sources Zdenka Bednarova & Jan Kuta & Lukas Kohut & Jiri Machat & Jana Klanova & Ivan Holoubek & Jiri Jarkovsky & Ladislav Dusek & Klara Hilscherova
Received: 4 December 2012 / Accepted: 17 April 2013 # Springer-Verlag Berlin Heidelberg 2013
Abstract Purpose The main purpose of this study was to evaluate temporal and regional variability of contamination by heavy metals (HMs) in river sediments using their enrichment factors (EFs) and benchmarking according to sediment quality guidelines (SQGs). The Zlin region in the Czech Republic (Morava and Drevnice River basins) represents a model area where several regionally specific ecological risk assessment studies have recently been conducted with a focus on organic pollution, eco-toxicity, geological, and geochemical characteristics. Materials and methods Four consecutive sediment sampling campaigns were undertaken in spring and autumn 2005–2006. Aqua-regia leachable content of Cd, Co, Cr, Cu, Ni, Pb, Sb, V, and Zn in surface sediments from 14 sites was analyzed using ICP-MS, and Hg content was analyzed using AMA-254 analyzer. EFs were calculated to identify the human impact on pollution in the area. Comparisons to SGQs were conducted to identify the areas and HMs of greatest risk. Results and discussion Calculation of EFs contributed to the effective clustering of HMs. Median EFs of Co, Ni, and V
Responsible editor: Marcel van der Perk Electronic supplementary material The online version of this article (doi:10.1007/s11368-013-0706-2) contains supplementary material, which is available to authorized users. Z. Bednarova : J. Kuta : L. Kohut : J. Machat : J. Klanova : I. Holoubek : K. Hilscherova (*)
ranged from 0.9 to 1.4 at all sites indicating concentrations very close to natural geological background levels. There was greater enrichment at locally polluted sites, the highest in the cases of Cd, Sb, Hg, and Cr. Widespread influence of diffuse HM sources (traffic, agriculture, and urban wastes) was apparent from elevated concentrations of Pb, Cu, and Zn at all sites. EF values also helped to identify the greatest temporal changes and shifts in HMs contamination between adjacent sites caused by 50-year recurrence interval floods in early spring 2006. The impact was most apparent in downstream sites; namely directly below the confluence of the two major rivers. Conclusions The overall contamination of HMs in the region was classified as low-to-moderate with significantly contaminated sub-areas. The study showed relatively stable spatial distributions of HMs, indicating potential sources of pollution. Cu was identified as the HM of greatest risk. The study emphasizes the necessity of considering both environmental circumstances and background HM occurrence to prevent misinterpretation of the pollution situation. The use of EFs which include grain size proxy normalization and HM background levels, along with the comparison of the detected concentrations to SQGs, proved an efficient way to identify hazardous contamination from anthropogenic sources. Keywords Enrichment factor . Heavy metals . Sediment quality guidelines
Research Centre for Toxic Compounds in the Environment (RECETOX), Faculty of Science, Masaryk University, Kamenice 753/5, 62500, Brno, Czech Republic e-mail:
[email protected]
1 Introduction
J. Jarkovsky : L. Dusek Institute of Biostatistics and Analyses, Masaryk University, Kamenice 126/3, 62500, Brno, Czech Republic
Heavy metals (HMs), due to their persistence and toxicity in the environment, have become a serious problem in past decades. The occurrence of HMs in the environment can be
J Soils Sediments
linked both to natural and anthropogenic sources, and their bioavailability and toxicity to aquatic life depend on speciation, which is largely determined by the physico-chemical conditions at each site (Campbell et al. 2006). The chemical industry, fossil fuel combustion, pesticides and fertilizer application, sewage waters, urban pollution, road and roof runoff, and outdated tap water systems (Nriagu and Pacyna 1988; Bergbäck et al. 2001; Förstner et al. 2004) are the major anthropogenic sources of HMs, both at local and regional scales (Nriagu 1979). Sediments have the ability to accumulate organic and inorganic chemicals and thus serve as a sink for pollutants in the environment. Metals entering the aquatic systems can be associated with the fine-grained fraction of sediments and suspended matter with large surface areas and high sorption capacities. Under natural conditions, HMs are initially sorbed on the biofilm, which consists of various microorganisms covering mineral surfaces (Förstner 2004). However, this process depends on: the particular metal; ion-exchange properties of the sediment (Nehyba et al. 2010); physical and chemical characteristics of the pore water in sediment, such as pH, redox potential, and salinity; and the concentration of dissolved organic chelators (Campbell et al. 2006). Water and sediment form a dynamic system where the contaminants can be released to water, transported, and redistributed according to the hydrologic and other specific conditions (Büttner et al. 2006). Metals can thus potentially impact even uncontaminated or lesscontaminated parts of the river (Förstner et al. 2004). In sediments, some amount of trace metals occurs naturally, and geological background concentrations in some areas may be even higher than the sediment quality guideline (SQG) levels (Campbell et al. 2006). A distinction between natural levels and anthropogenic contamination can be inferred from calculation of an enrichment factor (EF) for each metal. For a comparison of measured concentrations to the background levels, some authors suggest comparing the data with: average crustal concentrations (Taylor 1964); concentrations from the deepest part of core profiles (Meybeck et al. 2007; Birch and Olmos 2008); or concentrations measured upstream where no pollution is expected (Grosbois et al. 2006). It is usually recommended to use specific background values connected to the assessed region (Chapman et al. 1999; European Commission 2010). Sampled and background sediments can differ in texture, therefore normalization of data to grain size distribution or using one element as a grain size proxy is recommended. The element most often used as a grain size proxy is Al, because aluminosilicates are assumed to compose the major part of fine-grained sediments (Covelli and Fontolan 1997; Grosbois et al. 2006; European Commission 2010; Milacic et al. 2010). The assessment of sediment quality is inevitably connected to the quality of surface waters. Good chemical and ecological
status of surface waters is required by European Water Framework Directive (WFD, 2000/60/EC), therefore there is also a need to set sediment environmental quality standards (European Commission 2011). These are the key tools for the assessment and classification of the chemical status of a waterbody under the WFD. The derivation of SQGs can be based on the equilibrium partitioning model using mainly aqueous-phase organisms (Crommentuijn et al. 2000) or sediment effect concentrations (SECs) based on ecological and ecotoxicological endpoints in sediments (de Deckere et al. 2011). This study investigated variation in levels of HMs originating from various sources, and their annual and seasonal changes as influenced by major floods, in river sediments from part of the Morava river basin. The area assessed has been described in a set of publications focused on persistent organic pollutants (POPs) contamination, geological, and geochemical characteristics and sediment toxicity (Hilscherova et al. 2007, 2010; Babek et al. 2008; Blaha et al. 2010; Nehyba et al. 2010). This study aimed to: (a) evaluate heavy metal distributions in river sediments; (b) assess regional patterns and temporal variability in HM pollution; and (c) compare concentrations with SQGs to assess the real environmental significance of the observed contamination.
2 Materials and methods 2.1 Study area and sampling sites The study sites are located in the Zlin region, in the catchments of the Morava, Bratrejovka, Lutoninka, and Drevnice rivers (Table 1). Bratrejovka and Lutoninka are small streams (drainage areas 32.1 and 89.3 km2, respectively) with average discharges
