Vol. 27, 2009, No. 6: 470–476 Czech J. Food Sci. Mercury and Methylmercury Content in Chub from the Svitava and Svratka Rivers at Agglomeration Brno Kamila KRUžÍKOVÁ1, Jana BLAHOVÁ1, Renáta KENšOVÁ1, Jana JURčÍKOVÁ2, Dušan HYPR3 and Zdeňka SVOBODOVÁ1 1Department of Veterinary Public Health and Toxicology, University of Veterinary and Pharmaceutical Sciences Brno, Brno, Czech Republic; 2Institute of Public Health of Ostrava, Ostrava, Czech Republic; 3Czech Hydrometeorological Institute, Brno, Czech Republic Abstract Kružíková K., Blahová J., Kenšová R., Jurčíková J., Hypr D., Svobodová Z. (2009): Mercury and methylmercury content in chub from the Svitava and Svratka Rivers at agglomeration Brno. Czech J. Food Sci., 27: 470–476. The aim of our study was to determine the total mercury and methylmercury contents in the muscle of indicator fish, to determine the total mercury contents in the sediment, and to evaluate the health risks associated with fish con- tamination. Chub (Leuciscus cephalus L.) were caught in seven localities on the Svratka and Svitava Rivers in the Brno agglomeration in 2007. The total mercury content was determined by atomic absorption spectrophotometry using an AMA 245 analyser. Methylmercury levels were determined by gas chromatography (using electron-capture detector) after acid digestion and extraction with toluene. The highest levels of total mercury and methylmercury contamina- tion in the fish muscle (0.18 ± 0.09 mg/kg and 0.16 ± 0.09 mg/kg, respectively) were found at the Rajhradice site (the Svratka River, under the Brno city), whereas the lowest contents of mercury and methylmercury (0.08 ± 0.02 mg/kg and 0.04 ± 0.03 mg/kg) were detected at the Modřice site (the Svratka River). Total mercury content in the sediment ranged from 0.06 mg/kg to 1.38 mg/kg, the higher value having been detected in the sediment from the Svratka River at the Rajhradice site above the confluence with the Svitava River. The lowest content was discovered at Kníničky (the Svatka River). The hazard indices calculated for the selected localities showed no health risk to the common consumer or to the fishermen and their families. Keywords: Czech river; Leuciscus cephalus; methylation; methylmercury; sediment; total mercury The contamination of aquatic systems is pres- phenyls (PCB), dioxins, polyaromatic hydrocarbon ently at the centre of attention in the research (PAH), and others. In the Czech Republic, much community. Most of the xenobiotic compounds attention has been directed to the monitoring have the ability to accumulate in living organisms of heavy metal (including mercury) contamina- (for example fish), and sometimes they can be tion of surface water and the evaluation of the hazardous to people. Included in this group of health hazards related to human fish consumption compounds are heavy metals, polychlorinated bi- (Maršálek et al. 2006). Supported by the Ministry of Education, Youth and Sports of the Czech Republic, Projects No. MSM 6215712402 and No. 2B06093. 470 Czech J. Food Sci. Vol. 27, 2009, No. 6: 470–476 Mercury is known as a global pollutant and is over 95% of total mercury (THg) in the fish tissues distributed throughout the natural environment (Mason et al.1995; Houserová et al. 2006a) affecting many bio-organisms. Methylmercury ac- The aims of the present study are: cumulates in fish, resulting in these fish becoming − to determine THg and MeHg concentrations the main source of human methylmercury contami- in the muscle of chub which were used as an nation. Inorganic forms of mercury do not partici- indicator species and were caught in 7 locali- pate in mercury bioaccumulation in ecosystems, ties on the Svitava and the Svratka rivers at the therefore the determination of the organic forms Brno agglomeration, is essential. Inorganic mercury is methylated in − to detect total mercury concentration in the freshwater ecosystems into methylmercury (MeHg) sediment from the localities in which the indi- (WHO 1990). This mercury methylation mecha- cator fish were caught, nism was first described by Landner (1971) and − to evaluate the health risks associated with the by Wood (1971). Methylation involves both biotic consumption of fish from these localities. and abiotic pathways. The biological production of methylmercury largely depends on anaerobic sediment bacteria of the genus Methanobacterium MATERIALS AND METHODS (Hamasaki et al. 1995). Bacteria which have the abilities to reduce sulphates play an important role Study area. In this work, attention was paid in the process of methylation in the water sediment. to mercury contamination in the Svitava and the The process of methylation occurs fastest on the Svratka Rivers. These rivers run through the city surface of the sediment (Compeau & Bartha 1985). of Brno, the second largest town in the Czech The rate of methylation is a function of both the Republic, with a population of 366 680. The city activity of methylating bacteria and total mercury lies in the basin of the Svratka and Svitava Rivers. concentration (Gilmour & Henry 1991). The Svratka River cuts a 29 km swath through the MeHg accumulates in fish as it advances through city and is the main water supply for the Kníničky the food chain. Methylmercury (MeHg) makes up Dam Lake, a popular recreation area in the city’s Figure 1. Map of the Czech Re- public and the sampling sites 471 Vol. 27, 2009, No. 6: 470–476 Czech J. Food Sci. northwest corner. The Svitava River flows through were collected at the selected localities by elec- the city for about 13 km. The Svitava River meets trofishing. The fish were immediately weighed the Svratka River downstream from Brno and is and measured, and their gender was determined the main tributary of the Svratka River. Seven macroscopically. The scales were removed for the sites on these rivers were chosen for assessing the age determination. For THg and MeHg analysis, influence of Brno on the mercury contamination samples of muscle tissues were taken from the of fish and sediments. cranial parts of the fish under the lateral line, and Two localities (Bílovice nad Svitavou; Svitava were then put into polyethylene bags, marked, before junction) on the Svitava River and five lo- and stored in a freezer at –18°C. Table 1 shows calities (Kníničky; Svratka before the confluence; the main biometric characteristics of the fish col- Modřice; Rajhradice; Židlochovice) on the Svratka lected from the selected sites. River were chosen (Figure 1). The Bílovice nad Svi- Samples of sediment were collected from the tavou site characterises the river above Brno and is same localities during the spring, summer, autumn, the control site for the Svitava River. Another site and winter seasons. At each location, composite on the Svitava (Svitava before junction) is located bottom sediment was collected into dark glass below Brno before it flows into the Svratka. bottles and stored at –18°C. The sampling was Kníničky reservoir was built between 1938 and validated in accordance with ISO 5667 12 norm. 1941 on the Svratka River to prevent flooding. The Determination of THg and MeHg. The amounts dam reservoir is a lake approx. 10 km long and of THg in muscle and in sediments were determined 800 m wide in places, and contains approx. 25 mil- by cold vapour atomic absorption spectrometry on lion m3 of water. The Brno Reservoir is a frequently an AMA 254 analyser (Altec Ltd., Dvůr Králové visited recreational area with water transportation n. L., Czech Republic). and sporting facilities. The sampling site Kníničky Methylmercury was determined in the form of (56.2 river km) is located downstream from the methylmercury chloride by gas chromatography reservoir and is above the city of Brno. One site (Caricchia et al. 1999). The samples were pre- chosen on the Svratka (Svratka before junction) pared by acid digestion and extraction with toluene (40.9 river km) is downstream from Brno before (Maršálek & Svobodová 2006). A Shimadzu the confluence with the Svitava River. Modřice capillary gas chromatograph with an electron cap- (38.7 river km) is the site of the sewage works com- tured detector GC 2010A (Shimadzu Kyoto, Japan) pany Brněnské vodárny a kanalizace a.s. The main was used for the analysis. A capillary column DB activity of this company is to operate the public 608 (30 m × 0.53 mm × 0.83 μm; J&W Scientific water works and sewage systems. The other sites Chromservis, Prague, Czech Republic) was used. are at Rajhradice (35.0 river km) and Židlochovice The evaluations were made using GC Solution (30.0 river km), located after the confluence of the software (Shimadzu Kyoto, Japan) and MS Excel two rivers downstream from Brno. software. Sampling of fish and sediments. In 2007, a The detection limits for THg and MeHg were total of 106 indicator fish (Leuciscus cephalus L.) 1 μg/kg and 21 μg/kg, respectively. The limit of Table 1. Biometric characteristics (mean ± S.D.) of chub captured in the selected localities Locality n Body length (cm) Body weight (g) Age (year) Bílovice nad Svitavou* 23 20.7 ± 1.8 141± 45.8 5.0 ± 1.0 Svitava before junction* 14 21.4 ± 2.5 180 ± 69.7 4.1 ± 1.0 Kníničky** 12 24.3 ± 4.1 294 ± 175.0 5.5 ± 1.8 Svratka before junction** 15 24.4 ± 2.7 231 ± 97.0 5.3 ± 1.2 Modřice** 14 24.9 ± 2.3 296 ± 100.4 5.4 ± 1.1 Rajhradice** 14 25.8 ± 4.9 336 ± 246.7 5.5 ± 1.5 Židlochovice** 14 24.2 ± 4.3 280 ± 162.3 4.1 ± 1.2 *site at the Svitava River; **site at the Svratka River; S.D. = standard deviation 472 Czech J. Food Sci. Vol. 27, 2009, No. 6: 470–476 detection (LOD) was set as a sum of triple the fish with an extensive food web, and thus it is very standard deviation of a blank and a blank mean suitable for the monitoring of aquatic ecosystems value.