Hydrochemical analysis and ecotoxicological assessment of the Kacha river water quality

Abstract

Purpose: to conduct a hydrochemical analysis and give a comprehensive eco-toxicological assessment of the Kacha river water. Materials and methods. The content of chemical components in surface water was determined using titrimetric and photocolorimetric analyses. The degree of surface water pollution was calculated using a comprehensive assessment method on individual hydrochemical indicators, calculating the combinatorial water pollution index. Algotesting was carried out by measuring the optical density of the chlorella microalgae culture (Chlorella vulgaris Beijer). For phytotesting the seeds of dicotyledonous plants – cucumber (Cucumis sativus L.), soya bean (Glycine max (L.) Merr.) and monocotyledonous plants – common oats (Avena sativa L.) were used. Test parameters: seed germination and germination readiness, root and sprout length were analyzed. Results. According to the hydrochemical parameters of the Kacha river, the waters were classified as oligohaline, and according to the specific combinatorial index (S′ = 1.15) they were classified as slightly polluted ones of the second class. The values of the coefficient of complexity of water contamination rate during 2012–2018 were within 12 %. In 2023, the Kacha river water was defined as moderately hard water (7.4 mg-eq/cubic dm), while a decrease in the average water salinity (566.1 mg/cubic dm) and an improvement in its quality in terms of total iron (0.12 mg/cubic dm) were noted, which corresponded to the maximum permissible concentration for water bodies of municipal and amenity water use significance. The water algoeffect reached 57 %, and the phytoeffect – 87 %. Conclusions. The use of biological methods – algotesting and phytotesting – showed the presence of toxicants in the Kacha river water from the effluent to the mouth. The need for additional control of the river water quality during its use, including irrigation, was noted.

Keywords

• small rivers
• water quality
• hydrochemical analysis
• algotesting
• phytotesting