Olesya Gonchar

Chernivtsi National University named by Yuriy Fedkovych, Ukraine

gonchar_olesya@gala.net
Characterization of the chemical composition of the water of

the river Dniester

(based on hydrochemical expedition).

 

Поверхневі води найбільш яскраво відображають інтенсивність господарської діяльності людини і являються якісним показником стану навколишнього середовища. Сьогодні у всьому світі спостерігається тенденція до збільшення забруднення поверхневих вод в результаті невпинного зростання промислового та с/г виробництва, зумовленого невпинним зростанням чисельності населення. Така тенденція характерна і для будь-якого об’єкту України, в тому числі ідля басейну р. Дністер

Surface water is most clearly reflect the intensity of households governmental human activities and are an indicator of quality of the environment. Today in the world there is a tendency to increased pollution of surface waters. This trend is typical for any water bodies of Ukraine, including the Dniester River Basin.

Hydrochemical investigation of the Dniester River and the Dniester reservoir conducted in 2007-2008, in periods of low and high water content. The study involved eight alignment of the Dniester River, 3 of which are located within the Dniester reservoir. Namely:

1. Dniester - Sambir;
2. Dniester -  Rozvadiv;
3. Dniester - Zhydachiv,
4. Dniester -  Halich,
5. Dniester - Zalischyky;
6. Dnester res. - Khotyn,
7. Dnester res. - Novodniestrovsk, 500 m above the dam;
8. Dnester res. - Novodniestrovsk, 500 m below the dam.

In selected samples were determined following indicators:
- from the group of major ions: HCO3, SO, Cl, Ca, Mg, Na, K;
- from the group of nutrients: NH, NO, NO, PO;
- from the group of physical and chemical substances: pH, O, permanent oxidation, CO, hardness;
- from the group of trace elements: Fe, Mn.

The results of two research expeditions are presented in this paper.

 Objective: to investigate the spatial and temporal characteristics of change of chemical composition of the Dniester River (Ukrainian part).

Object: Dniester (Ukrainian part of the river).

Subject: chemical composition of water of the Dniester River.

The results of the researches, that were conducted during expeditions, highlighted below.

The content of hydrocarbons in the water of the Dniester River varied between 170mg/dm3  during spring floods (Zalischyky, 2008) to 324 mg/dm3  during the autumnlow flow (Dniester res., 2007). On average, their concentration in water of the Dniester River was 266 mg/dm3 .

The minimum concentration of chloride in water was found in the upper Dniester, near the town  Sambir and is 14 mg/dm3  and 18 mg/dm3  respectivelyduring spring flooding and fall low flow. Maximum - 52 mg/dm3  in alignment of the Dniester River - the town Halich. The average concentration of chloride to the Dniester River from source to the border with Moldova is 31.7 mg/dm3 .

The minimum concentration of sulfates as found during spring flooding in 2008 andwas 20.2 mg/dm3  (Sambir). The highest content of sulfateequals 67.1mg/dm3  ( Rozvadiv) during low water content (autumn, 2007). The average concentration of SO-4 within the expeditionary studies was 49.3 mg/dm3 .

The content of calcium in the water of the Dniester River changed according to changes in water contenting thing. In particular, the maximum concentration of Ca2 + detected during autumn low flow in 2008 and was 100 mg/dm3  (Rozvadiv), the minimum during the spring flood in 2007 - 44 mg/dm3  (Zalischyky). It should be noted that the average amount of concentration Ca2 + in the water of the Dniester River also indicate a link between the content of calcium ions and changes in water content, varying from 66.3 mg/dm3  (spring flood) to 73.7 mg/dm3  (autumnlow flow ).

The concentration of  magnesium changed in minor extent, on average, in the the water of the research part of theDniester River from 24.5 mg/dm3  during spring floods to 28.4mg/dm3  in certain periods of time. The maximum content of Mg2 + was found in the waterof the Dniester reservoir near Novodniestrovsk, 38.4 mg/dm3  (spring flood) and44.1 mg/dm3  (autumn low flow).

An important indicator of the chemical composition of surface water bodies is mineralization, which usually varies according to changes in water content. Size of mineralization according to the average indicators for the Dniester River, changed according to the studied seasons: spring floods (2008) and autumn low flow (2007). It is from 308 to 367 mg/dm3  mg/dm3 . The minimum value of mineralization was found in the spring floods and equals 230 mg/dm3  (Zalischyky), the maximum  is409 mg/dm3  in autumn low flow ( Rozvadiv).

 Nutrients determine water quality. Their excessive amounts in the water may make it unsuitable for use. In the spatial dynamics of the ammonium ion content should be noted Dniester reservoir. The maximum concentration of  NH4-  is 0.3 mg/dm3  (Khotyn). The minimum content of  NH4- is <0.05 mg/dm3  in most cases during the spring flood. The minimum content of nitrite ions is 0.002 mg/dm3  (Sambir, 2007), maximum - 0.7 mg/dm3  (Halych, 2007). The concentration of nitrate ions in the investigated seasons was different. In the autumn low flow maximum value was found in the middle of the river: 10.5 mg/dm3  (Zalischyky), 11.8 mg/dm3  (Khotyn, Dniester res.). During the spring flood maximum NO3- were found in the water of the Dniester reservoir: 12.5 mg/dm3  (Khotyn), 13.6 mg/dm3  (Novodniestrovsk, 500 m below the dam hydroelectric). The content of nitrite ions varied within normal limits. The average, for the studying part of the Dniester, phosphate concentration was changed from 0.097 mg/dm3  during spring floods to 0.151 mg/dm3  in autumn low flow period. It should be noted spatial differences in the change of content of phosphate ions. According to the results of the expedition during the autumn low flow maximum value PO42- were found in the water reservoir of the Dniester, namely 0.340 mg/dm3  (Novodniestrovsk, 500 m above the dam hydroelectric) and 0.218 mg/dm3  (Novodniestrovsk, 500 m below the dam hydroelectric). Results of research expeditions during the spring flood indicate the maximum value PO42-at the top of the Dniester River, namely 0.154 mg/dm3  (Rozvadiv) and 0.168 mg/dm3 (Zhydachiv).

One of the objectives of the study was to determine in the water of the Dniester River of pH. Spatial-temporal dynamics of changes in pH are small and fluctuate within the normal range from 7.7 (low flow autumn to 7.8 (spring flood) according to the averaged values.

Spatial dynamics of permanent oxidation is clearer in the spring flood. The range of values of PO for water in the studying parts of the Dniester River varied from 1.9mhO/dm3  (Novodniestrovsk, 500 m below the dam) to 12 mhO/dm3  (in Ho-ting), while during the autumn low flow fluctuations decreased in range from 3.8mhO/dm3  (Sambir) to 6.4 (p. Rozvadiv).

Among the trace elements determined iron in the water content of the Dniester River. At different mean-zone, according to participating in the study, the total iron content varied along the length of the river. Thus, during the autumn low flow maximum concentration Fe was found at the top of a mountain river in alignmentin Rozvadiv, and in  Halich, 0.29 and 0.073 mg/dm3  mg/dm3 respectively, while in the spring  flood in 2008 the maximum concentration of  Fe  was found in the ranges of average plains of the river, in alignment Zalischyky and Khotyn 0.12 and 0.32 mg/dm3  mg/dm3  respectively.

Thus, the content of major ions particularly bicarbonate, calcium ions, the amount of ions varied according to changes in water content of the Dniester River. Maximal values ​​were found during autumn low water (2007), minimal - flood (2008). Content of nutrients is the largest in the water of the Dniester reservoir.