**10.1. Manganese (Mn)**

cation in summer is favoured by hydrological and meteorological conditions such as small

There is no widely agreed criterion-based definition of heavy metals. Quantitative criteria used to define heavy metals included density, atomic mass and atomic number. Often applied density criteria range from above 3.5 g cm−3 to above 7 g cm−3. In aquatic environment, heavy metals occur as micro-pollutants. Their natural sources include rock weathering, volcano eruptions, sea aerosols, forest fires and geological processes. Most important anthropological sources are transport, power industry, chemical industry, solid waste sites, fertilizers, flue gases, and so on. Heavy metals are stable pollutants and once introduced into a given envi-

In aquatic environment, heavy metals can be in the form of ions and dissolved complexes, and bonded to inorganic suspended matter and also to dead remains of vegetation and animals. Heavy metals are toxic species, even at rather low concentrations, and toxicity is strongly

In 2004–2006, the quarterly measurements of such heavy metals as manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), lead (Pb) and cadmium (Cd) in the water of the Turawa reservoir were conducted. They included the following: 12 measuring series were performed, 130 determinations of each metal in each series. The measurements were made for different reservoir filling to achieve the most reliable results. The program of sampling must have been precisely planned since heavy metals undergo multiple processes of desorption and adsorption during turbulent movement of water. The main source of heavy metals in the reservoir was the Mała Panew river. In the catchment of this river, zinc and lead ores were mined for about 100 years in the sixteenth/seventeenth century. At the end of the eighteenth century, mining and metallurgy of heavy metals were developed in the area again. Mines and numerous processing plants were discharging polluted industrial effluents into the Mała Panew river and its tributaries resulting in heavy pollution of river water and bottom sediments in which heavy metals accumulate resulting in steady increase in concentration. The heavy metals accumulated in sediments in the past can re-enter the liquid phase of the river water. Both forms of the pollutants, that is, dissolved in water and bonded to sediments, can be transported to the Turawa reservoir. In the years studied, there were 46 point sources discharging the pollutants to the Mała Panew river, 36 (26 industrial) of which were situated in the catchment of the reservoir. Due to the tendency to accumulate, the heavy metals were present at high concentrations in the sediments deposited in the reservoir, for example, the permissible level for cadmium was exceeded 10 times and for lead and zinc seven times. The heavy metals present in sediments can be reintroduced into the liquid phase during water rippling and flow which

dependent on the metal. Their presence can influence the bloom of green algae.

enhance the fluctuation of water level and hence uncovering the reservoir bottom.

stream flow of inflowing rivers, low water level and high water temperature.

**10. Content of heavy metals**

394 Water Quality

ronment can remain there for a long time [9].

The occurrence of manganese in surface water is quite common. It is leached out of rocks and soil. According to some researchers, the concentration of 6 μg dm−3 is taken as a background for river water. The main anthropogenic sources include Mn metallurgy and burning coal and petrol. In small amounts, manganese is needed and present in vegetation and animals. It plays the role of catalyst in biochemical processes.

In the Turawa reservoir, the average content of manganese was 0.0590 mg dm−3 and changed from below detection limit to 0.2043 mg dm−3. The highest concentration was determined in winter due to advantageous conditions of leaching from subsoil. In summer, the content dropped due to adsorption on suspended matter.

According to surface water classification, the reservoir water, with respect to Mn content, was classified most often as the second class of purity, and occasionally as the first class in summer and as the third in winter.
