Chemical Analysis and Evaluation of Fe and Ni Spatio-temporal Variations along Tundzha River Southeastern Downstream, Bulgaria Nedyalka Georgieva*1, Zvezdelina Yaneva1 Chemistry Unit, Department of Pharmacology, Animal Physiology and Physiological Chemistry, Faculty of Veterinary Medicine, Trakia University, Students Campus, 6000 Stara Zagora, Bulgaria E-mail: [email protected]; [email protected] *Corresponding author: Assoc. Prof. N. V. Georgieva PhD, Tel.: (+359) 42 699 642; Fax: (+359) 42 672 009; Е-mail: [email protected] Abstract The urge for sustainable development of natural water resources, especially in the developing countires and these with economies in transition implements the establishment and/or further development of national monitoring networks and water resources databases, as well as the development of relevant national indicators. In this context, the present study evaluated the current status of Fe and Ni levels, their origin and spatio-temporal distribution in the surface waters from the southeastern downstream of Tundzha River, Bulgaria, including five of its tributaries in Stara Zagora Region. To accomplish the latter goal, Ni concentrations in real surface water samples were determined by atomic absorption spectrophotometry (AAS) and Fe contents - spectrophotometrically, during the period December 2009 - November 2010. The statistical significance of the experimental data was tested. The ecological monitoring revealed sharp increases of Ni concentrations, surpassing the Ist category standard for surface water quality (0.05 mg/L Ni) from 3 to183 times, in the six studied rivers during July, 2010. Tundzha River and Radova River characterized with the maximum Ni contents predominantly during the spring and summer months. Accidental industrial wastewater discharge from the machine-building and textile enterprises in Kazanlak Municipality could be the probable reason for the registered elevated Fe contents (from 0.24 to 2.30 mg/L) in Leshnitza River and Tundzha River surpassing the IInd category standard for surface water quality (1.50 mg/L Fe) with approximately 1.5 times during April, 2010. The high measured Fe concentrations in the samples from Radova River (1.20 mg/L) and Lazova River (1.70 mg/L), Gurkovo Municipality, during May 2010, could be attributed to reverse infiltration of Fe-enriched mine leachate from the nearby situated abandoned mines. The significance of the research was expressed by the fact that it provided a database necessary for the development of pollution control strategies on national and international basis considering that Tundzha River is the biggest tributary of Maritza River, emptying into it on Turkish territory near Edirne. Keywords: Fe, Ni, monitoring, rivers, Bulgaria Introduction Heavy metals are a serious pollutant of the environment due to their toxicity, persistence and bioaccumulation ability. Their occurrence in waters and biota indicate the presence of natural or anthropogenic sources. Trace metals tend to be trapped in the aquatic environment and accumulate in sediments and may be (i) directly available to benthic fauna or (ii) released to the water column through sediment re-suspension, adsorption/desorption reactions, reduction/oxidation reactions and the degradation of organisms (Pekey et al., 2004). Industrial and household heavy metals-rich effluents discharged, directly or indirectly, through leakages in the sewage systems and consequently into natural water sources cause excessive pollution of surface and groundwaters. Consequently, water quality and irrigation value are lost. It is necessary to know the mechanisms of the heavy metals transportation and their complexes in rivers to understand their chemical cycles in nature. In natural BALWOIS 2012 - Ohrid, Republic of Macedonia - 27 May, 2 June 2012 1 media, trace metals undergo numerous changes during their transport due to dissolution, precipitation and sorption phenomena. Trace element concentrations of river basins depend on not only industrial and household waste inputs but also on the geochemical composition of the area (Akcay et al., 2003). Some trace metals like iron (Fe) and copper (Cu) are important both as nutrients and potential toxicants for algal growth in natural water bodies. It is not yet clearly established if the relatively high dissolved Fe concentrations (< 0.45 µm) observed in many organic rich freshwater systems are attributed to Fe-organic (humic) complexes and/or small Fe-oxyhydroxide particles. Recently, both types of colloids, Fe-oxyhydroxides and Fe-C colloidal matter, have been identified as important carriers of dissolved Fe in boreal river systems (Ingri et al., 2006; Benedetti et al., 2003). The direct and indirect effects of Fe on the structure and function of lotic ecosystems have been reviewed. In addition to the mining of Fe-enriched ores, intensified forestry, peat production, and agricultural water runoff have increased the load of iron in many river ecosystems. The effects of iron on aquatic animals and their habitats are mainly indirect, although the direct toxic effects of Fe2+ are also important in some lotic habitats that receive Fe-enriched effluents particularly during cold seasons. Ferric hydroxide and Fe-humus precipitates, on both biological and other surfaces, indirectly affect lotic organisms by disturbing the normal metabolism and osmoregulation, and by changing the structure and quality of benthic habitats and food resources. The combined direct and indirect effects of Fe contamination decrease the species diversity and abundance of periphyton, benthic invertebrates, and fishes (Eugen et al., 2003). The bioaccumulation of Fe in the organs and tissues of the freshwater crab, Potamonautes warreni Calman, from three metal-polluted aquatic ecosystems was examined by Steenkamp et al. (1993). Differences in Fe concentrations in water and sediment were related to environmental variables. The highest Fe concentrations in the crab occurred in the gills, suggesting this organ to be the prime site for the absorption and/or loss of Fe to and from the aquatic environment. Despite the absence of a seasonal or gender-related tendency in the heavy metal concentrations in the various organs and tissues, an inverse relationship between the size and the capacity of the crab to bioaccumulate Fe was established (Steenkamp et al., 1993). In addition, Fe is vital for almost all living organisms, participating in a wide variety of metabolic processes, including oxygen transport, DNA synthesis, and electron transport. Iron concentrations in body tissues must be tightly regulated because excessive Fe leads to tissue damage, as a result of the formation of free radicals. Disorders of Fe metabolism are among the most common diseases of humans, encompassing a broad spectrum of diseases with diverse clinical manifestations ranging from anemia to iron overload and, possibly, to neurodegenerative conditions (Eugen et al., 2003). Iron is found in surface and ground waters at varying concentration levels, usually up to 3 - 4 mg/L, but in some cases even up to 15 mg/L. When present, even at low concentrations it can be linked to aesthetic and operational problems such as bad taste and color, staining, as well as deposition in the water distribution system leading to incidence of high turbidity. Besides, Fe promotes the growth of certain types of chlorine-tolerant microorganisms in water distribution systems, thus causing increased costs for cleaning and sterilizing systems in addition to odor and taste problems. The state of iron in water depends above all on the pH and the redox potential. By increasing the pH, dissolved iron (Fe2+ or Fe3+) hydrolyzes to form precipitates. The ferrous ion hydrolyzes to produce the array of + 2- 3+ mononuclear species FeOH to Fe(OH)4 between pH 7 and 14. The ferric ion (Fe ) hydrolyzes much more readily than the ferrous ion, beginning at about pH 1. There are several genera of bacteria that oxidize dissolved iron with different mechanisms, including Gallionella sp., Leptothrix ochracea, Crenothrix polyspora, Leptothrix sp., Crenothrix sp., Clonothrix sp., Sphaerotilus sp., Toxothrix thrichogenes and Siderocapsaceae (Tekerlekopoulou et al., 2006). Nickel (Ni) is a non-biodegradable toxic heavy metal. According to the World Health Organization guidelines (WHO), the maximum permissible concentration of Ni in drinking water should be less than 0.1 mg/L (WHO, 2004). It has been reported that Ni is ubiquitous in the biosphere and is a common component of natural fresh waters due to erosion and weathering. The high consumption of nickel- containing products inevitably leads to environmental pollution by Ni and its by-products at all stages of production, recycling and disposal. It has also been reported that fresh water levels of Ni are typically about 1–10 µg/L in unimpacted areas and anthropogenic loading of Ni into aquatic and terrestrial ecosystems in industrial areas occurs by mining, smelting, refining, alloy processing, scrap metal reprocessing, fossil fuel combustion and waste incineration (Kandah et al., 2007). Ni concentrations in highly contaminated fresh waters may reach as high as several hundred to 1000 µg/L. BALWOIS 2012 - Ohrid, Republic of Macedonia - 27 May, 2 June 2012 2 It is known that exposure to nickel compounds can have adverse effects on human health (Can et al., 2006). Nickel allergy in the form of contact dermatitis is the most common and well-known reaction. Although the accumulation of the heavy metal in the body