Studies of heavy metal content in bottom sediments and aquatic plants near treated wastewater discharge

Abstract

The paper attempts to determine the degree of impact of discharged wastewater from five treatment plants on the Bug River ecosystem and its inflow, the Kamianka. For laboratory tests, samples of bottom sediments and aquatic plants were collected in 2014. The content of heavy metals: Zn, Pb, Ni in bottom sediments and aquatic plants (root, stem, leaf) growing close to the discharge of purified sewage, were analyzed. The amount of metals in the samples was determined applying the AAS method in its flame version. The average content of the metals determined in bottom sediments from the study points located before the treatment plant were Zn – 21.8; Pb – 11.5; Ni – 13.7 mg⋅kg−1. However, the content of these metals was higher in samples from the collection points which were located after the place of purified sewage discharge and amounted to: Zn – 34.3; Pb – 12.2; Ni – 16.9 mg⋅kg−1. The test plants were Acorus calamus L., Nuphar lutea L., Typha angustifolia L. The content of metals in the individual parts of macrophytes (root, stem, leaf) was as follows: Zn > Pb > Ni. In the bottom sediments and aquatic plants of the Bug and Kamianka rivers, a higher content of lead, zinc and nickel was found after the discharge of treated sewage in relation to their content than before discharge, but it was not a threat to the aquatic environment of the watercourses studied. Statistical analysis showed that the amount of sewage discharged to the tested receivers influenced the content of organic matter, zinc and nickel in bottom sediments.