**10.5. Copper (Cu)**

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 biocides to kill blooming algae [14].

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

### **10.6. Zinc (Zn)**

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 classified as purity class I.

### **10.7. Lead (Pb)**

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 lead in surface waters [14].

In the water of the Turawa reservoir, the average lead concentration was 0.0116 mg dm−3; it changed from non-detectable to 0.412 mg dm−3. According to surface water classification obligatory in the years studied, the reservoir water with respect to Pb content was most often classified as purity class III and occasionally as class IV. The high concentration resulted from the fact the Mała Panew river delivering 87% water to the reservoir was strongly polluted with heavy metals, including lead. Most lead in water bodies collects in bottom sediments where from it can later move back to water.
