**10.8. Cadmium (Cd)**

hydroxide. In pure waters, its concentration is about 5 μg dm−3, while in strongly industrialized areas, surface waters can contain up to about 0.020 mg dm−3. Considerable amounts of nickel

In the water of the Turawa reservoir, the average cobalt concentration was about 6 μg dm−3 and ranged from below detection limits to 16.5 μg dm−3. According to surface water classification in force in the years studied, the reservoir water with respect to Ni content was classified as purity class I. Only occasionally, the limiting concentration for class I was slightly exceeded.

Copper is quite common in the earth crust; its content is about 0.02%. In water, it is in the form of quite mobile complexes with humic and fulvic acids. Copper compounds are easily bonded to sediments. Copper is present in mineral waters due to the process of leaching out of rocks and soil. The natural concentration of copper in surface waters is about 0.002 mg dm−3. The main anthropogenic sources of copper are metallurgy, copper-processing factories, corrosion of products made out of this metal and its numerous alloys. Copper compounds are used as

In the water of the Turawa reservoir, copper concentration ranged from non-detectable to 0.0202 mg dm−3 with an average of 0.0111 mg dm−3. According to surface water classification in force in the years studied, the reservoir water with respect to Cu content was classified as purity class I. The highest concentration was found in summertime during intensive water blooming since algae are capable to accumulate heavy metals, including copper. Algae were

Zinc in the earth is present in the form of minerals though its occurrence is not common. Small amounts of zinc can be found in water due to leaching from soil. However, the main sources of zinc in surface water are effluents of zinc smelters, zinc processing factories, chemical industry and coal burning. Pipe corrosion can also be a source of zinc in water, especially in drinking water. Polluted waters contain zinc at a concentration of 0.005–0.015 mg dm−3.

In the water of the Turawa reservoir, the average zinc concentration was about 35.4 μg dm−3 and ranged from below detection limits to 169 μg dm−3. According to surface water classification obligatory in the years studied, the reservoir water with respect to Zn content was

Despite common occurrence in the earth crust, lead content in natural waters is low. However, due to common pollution of surface waters with lead, it is rather difficult to assess its natural content. Lead is present at 0.003 mg dm−3 in non-polluted waters. The main anthropogenic sources of lead are chemical industry, mining and ore-processing industry. In industrial areas whereby non-ferrous metal smelters are present, atmospheric precipitation can be a source of

are emitted during combustion of diesel fuel [13].

**10.5. Copper (Cu)**

396 Water Quality

**10.6. Zinc (Zn)**

classified as purity class I.

lead in surface waters [14].

**10.7. Lead (Pb)**

biocides to kill blooming algae [14].

able to assimilate up to 90% of copper present in the reservoir.

Cadmium, in the free form, is not present in the earth crust, but occurs in ores of other heavy metals, mainly zinc. It is very toxic and accumulates in living organisms. It is one of the most dangerous substances on the earth. The main sources of surface water pollution with cadmium are industrial effluents from cadmium mining and metallurgy and corrosion of galvanic covers. It is also present in some phosphate fertilizers. In non-polluted waters, it is present at 0.02 μg dm−3. Cadmium remains in water for relatively long time, then precipitates as carbonate and undergoes adsorption on suspended matter and sediments. In the process of bonding to sediments, bacteria participate converting cadmium compounds to CdS [14].

In the water of the Turawa reservoir, the average Cd concentration was 0.0025 mg dm−3; it changed from non-detectable level to 0.0164 mg dm−3. According to surface water classification, the reservoir water with respect to Cd content was most often classified as purity class IV and occasionally as class V. The high concentration in the water of the reservoir resulted from the process of chemical denudation of this element in the catchment area of the Mała Panew river. Cadmium present at high concentration in bottom sediment did not re-enter water layer since it is sparingly soluble in neutral and alkaline solution. Leaching of cadmium took place only at the lower level of water (in winter) when some part of the reservoir bottom is uncovered. The additional reason of cadmium pollution is runoff from arable land whereby phosphate fertilizers and dolomite fertilizers produced out of waste of lead and zinc mining and metallurgy are applied. Lower concentration of cadmium was observed during intensive blooming of algae which can absorb up to 80% of cadmium in the reservoir. It was found out that vegetation and animals take in cadmium at the rate proportional to its content.
