بررسی کیفیت شیمیایی آب رودخانه قرنقوچای هشترود به منظور مصارف بخش‌های کشاورزی و شرب با تاکید بر نقش سازندهای زمین شناسی

Introduction

Any changes that are imposed on the river system will upset its existing balance and will be faced with the reaction of the river in order to create a new balance. Rivers experience different conditions along their path, starting from the mountain path and after crossing the plains, they reach the mouth of the seas or other main rivers. Today, one of the most important challenges is the destruction or reduction of resources that have been formed in the natural environment of the planet under special conditions and over a long period of time. Natural processes (hydrological, physical, chemical and biological) can affect the characteristics and concentration of chemical elements and the quality of fresh water, in addition, the effects of human activities are also effective in water quality. River water quality is affected by two sources. Natural and artificial (human) origin. Most of the studies that have been done on the lithology maps of river water quality around the world make clear the fact that the dissolution of carbonate and evaporite minerals compared to silicate minerals is due to their high solubility. They have a more decisive role in the hydrochemistry of river water. Even in the most parts of the world, there have been many studies on the effects of geological and lithological formations on the quality of surface and underground waters. Therefore, the approach and purpose of the present research is also in this direction.





Methodology

After collecting the sources about the topic and location of the research based on documentary and library methods, the study area was also identified using 1:50000 topographic maps of the region and 1:200000 and 1:100000 geological maps of the Geological Organization. has been Qualitative water samples of the rivers of Khanah from the physical and chemical aspects for a period of twenty years (1379-1399) were conducted by the regional water organization of East Azerbaijan province and the results have been provided to the researchers.



Results and Discussion

The most important quality criterion in the classification of water from the point of view of agriculture is the amount of salinity and the amount of sodium in it. Salinity is measured by electrical conductivity (Ec) and sodium (Na) by one of the sodium absorption ratio (Sar) standards. The sodium absorption ratio is the amount of sodium divided by the square root of the sum of calcium and magnesium in water in terms of milliequivalents per liter, which is expressed as follows:



Drinking water should be free of color, smell, and taste, and in terms of elements and chemical substances in it, it should be within the permissible range determined by health organizations. The range of 7 to 8.5 is suitable for drinking water. TDS refers to the amount of total dissolved solids in water, usually expressed in milligrams per liter. The total hardness (TH) is also one of the quality criteria of drinking water, the amount of which is measured in terms of the equivalent weight of calcium carbonate. The total hardness can be calculated from the following equation, where the Mg and Ca values are in milligrams per liter. The formula needs to be edited. And it is not placed correctly.

TH=2/497 Ca + 4/115 Mg

Investigations and geological evidence of the basin as well as the results of qualitative tests obtained from hydrometric stations on this river show that the presence of calcareous formations in the basin under the influence of weathering and erosion causes the dissolution of calcium carbonate and also the entry of soluble bicarbonate ions into the river water. An increase in bicarbonate concentration in water results (Figure 12). If there are layers of gypsum or calcium sulfate between geological formations, sulfate solutes are formed in water. The results of the concentration of sulfate salts in this river indicate that the amount of these salts in the river water varied from a minimum of 0.12 at the Sahand Dam station to a maximum of 16.76 at the Tekanlo station. These values in the water at the outlet of the river at the tunnel station The number varied between 1.4 and 5.7.



Conclusion

The main result of this research is to investigate the quality of drinking and agricultural water in the study area with emphasis on the influence and role of geological formations. As the results of water quality surveys for agricultural purposes showed, according to EC and SAR indicators and using the Wilcox diagram, the water quality for hydrometric stations in the central parts of the basin to the west and southwest, including two dam stations, respectively. Sahand and Tekanlo are at an excellent and good level and occupy more than 80 percent of the area of the basin. However, the eastern and northeastern part of the watershed near Chapini stations and tunnel station number 7, which is also the outlet of the watershed, has average and inappropriate water quality. Also, the quality of water for drinking purposes according to TDS and TH indicators and also by using Schuler's diagrams in the central parts (Chapini stations and Sahand Dam) and the north and northwest have good and acceptable water quality. and the south and southwest area (Tekanlu station) with less than 30% of the area of the basin, has poor water quality due to the high amount of anions and cations such as sodium, potassium and sulfate in this basin. Also, the northeastern parts of the basin near tunnel station No. 7 have bad and undrinkable water quality. It shows the results of the investigations.

Also, the presence of evaporative formations such as chalk, salt and gypsum, marl and refractory limes has caused mineral dissolution and finally caused changes and reduction of river water quality. . So, therefore, it is suggested that planning should be done in the direction of water use in the final basin, so that there will be no problems in the direction of water use in many years due to the lack of water and the quality of the region.