Seasonal dynamics of transparency and concentration of some the water of Strezevo reservoir

Transcription

1 International Journal of Scientific Research Engineering & Technology (IJSRET), ISSN Volume 3, Issue 3, June Seasonal dynamics of transparency and concentration of some nutrients in the water of Strezevo reservoir Sonja Georgiev ska* 1, Julijana Tomovska 2, Igor Zlatkov 3, Mohammad Ali Shariati 4 1. Public Watereconomy Enterprise "Strezevo" Bitola, Republic of Macedonia. 2. University, St.Kliment Ohridski,, Faculty of Biotechnical sciences-bitola. 3. Agency for Promotion and Development of Agriculture-Bitola. 4. Department of Food Science and Technology, Science and Research Branch, Islamic Azad University, Tehran, Iran. ABSTRACT Increasing organic production in lakes is a normal process, but increased amounts of nutrients leads to increase in the degree of trophimus and eutrophication. Over time, many dynamics processes lead to visible changes that cause transformation ecosystems and succession from one form to another. These developments are clearly visible in stagnant freshwater ecosystems, in which over long period of time have seen their emergence, development and finally their disappearance while fulfilling the basin with different material. These changes are simultaneously sent and succession biocenosis which reflect in increasing production. Increased amount of nutrients in the water, allows increased primary production, thus increasing biomass of phytoplankton may lead to reduce light penetration. The subject of this paper is to determine seasonal changes in transparency and concentrations of some nutrients in the water of reservoir Strezevo through a long period of nine years. The results of these investigations showed that the values of the studied parameters indicate large fluctuations depending of seasonal changes and anthropogenic effects. Keywords: - Transparency, Nutrients, reservoir. Fig.1. Strezevo reservoir Strezevo 1. INTRODUCTION Strezevo reservoir is one of the largest artificial lakes in Republic of Macedonia which has a multifunctional activity. It is located in the southwestern part of R.Macedonia, near the town of Bitola. Its activity is multipurpose. It is used for irrigation, water supply, power generation, and flood defense, supply industry with technological water, fishery and recreation. Good water quality is required to perform all these functions Therefore it is performed regularly and continuous monitoring of the water for the long period. But over time aging of this aquatic ecosystem is inevitable that as a consequence is the occurrence of a process of eutrophication. Fig.2. Tower intake of the Strezevo reservoir Anthropogenic impacts of nature, often leads to undesirable consequences. One of these occurrences is eutrophication, including the reservoirs that man made. This process has been especially evident during the XX century and continuously resumes to this day. During the 7 years of 2th century, eutrophication has become an acute problem, what is that which control the primary production in freshwater lakes for increased pollution? (Krebs, 1994).One of the important issues of contemporary limnology is actually determining the cause of increased primary organic production in lakes, which ultimately leads to eutrophication. Within this main issue is the default in the mutual relationship between concentration of nutrient salts in water and the amount of primary organic production. Nutrients

2 International Journal of Scientific Research Engineering & Technology (IJSRET), ISSN Volume 3, Issue 3, June are coming into the lakes either directly through wastewater either indirectly by leakage. Their increased concentration leads to massive growth of algae, and succession to the phytoplankton which primarily reflected the suppression the silicate and green algae often expressed dominance of Cyanobacteriace. This process is marked as eutrophication (Krebs, 1994). To control the process of eutrophication in aquatic ecosystems it need to determine nutrients whichh need to be controlled. It proposed N, P and S. The results of many studies have shown that phosphorus is one that is limited to the development of phytoplankton in lakes (Edmonson, 1991, by Krebs, 1994). For primary producers phosphorus is available in the form of orthophosphate which is soluble and which is in control of the primary production (Wetzel, 1983). Parallei with the determination pf the content of certain nutrients in the water of reservoir Strezevo, in every collection of samples it also perform measuring water transparency as an important parameter for determining the tropic state of aquatic systems. 2. MATERIALS AND METHODS As rude indicator but frequently used indicator in underwater lighting and to determinee the depth to which is losing visibility is Secchy disc. Measurement of water transparency is performed in each analyzing the physicochemical parameters of water, and especially, regularly, continuously, all year seasons monitor this parameter. Water transparency is measured by immersion to seccchy disc depth to which you can watch and take note the value of depth in the centimeter or meter (Schnjorbel, 197). Collection and storage of materials for the determination of certain nutrients is made with standard limnological methods (Standard methods for the examination of water and wastewater, 2). Forms of nitrogen as nitrate nitrogen and ammonia as ammonia nitrogen, and phosphate determined spectophotometricaly by the spectrophotometer SPEKOL UV VIS. 3. RESULTS AND DISCUSSION Results of nine years period of research of the water quality in the reservoir Strezevo suggest that the large fluctuations in parameter values in different seasons, depending of seasonal changes and anthropogenic activities. Transparency of water depends on several factors: Concentration of suspended organic and inorganic matter in water Density of plankton Distributed particles Dissolved substances and pigments Angle at which the sun s rays fall Weather conditions (sunny, cloudy, with or without waves) Indicators Fig.3. Secchy disc Limits and concentrations of appropriate class I Transparency > 7 7,- m 1 4, 3,9-2, IV V < 2, < 2, Secchy dick is a metal disk with diameter of 3 cm, with black and white fields (Fig.3.).The results of these measurements during the nine years period (21-29) are given in Table 1. This parameter is standardized by the Regulation on water classification (Official Gazette of Republic of Macedonia, No 18/99). (Limits and maximum allowed values or concentration of organoleptic indicators) The average annual value of the transparency of water is one of the important parameters for determining the tropic state of lakes. As it can be seen, the transparency of the water of reservoir Strezevo, shows oscillations depending of the

3 International Journal of Scientific Research Engineering & Technology (IJSRET), ISSN Volume 3, Issue 3, June season and the year. It varies in the range from 6 cm in May 28 to 7 cm in June 26. Namely, there is matching peaks of increased transparency and reduced transparency over several months. Water transparency has expressed period which varies from season to season. It notes that there is cycling in all years of study. In 21 the grates transparency is established in February (31 cm).in the period from March to June is the constant level (2 227 cm), to slightly to rise in July and August (21, 272,86 cm). In the period September November transparency decreases and the lowest values for 21 are determined in October (142 cm). In January May 22, values of transparency of the water were on level below 2 cm, but in June and July were noted peak, and sharp increase in transparency (4cm). Relat ively good transparency is maintained in the next months, to the end of the year and it is within 3 cm. Throughout the next 23, the values of Secchy disk not falled below 2 cm. During most of the year there are 3 cm and above 3 cm. The lowest values were registered in the period from May to June (2 cm), and then the transparency increases. The greatest transparency of the water in 24 was measured in January (4 cm). Then transparency is reduced, so that the smallest is in May (13, 33 cm). In June July it comes to a gradual increase in the values of Secchy disk, in August to reach high value 334,28 cm. Follow gradually decrease in September-October to reach about 2 cm in the winter months (November December). Relatively high transparency of over 2 cm was measured in the first three months of 2 and continues to decline to reach a minimum of 9 cm in June. Further transparency in summer gradually increases and reaches a maximum in September (36 cm). Slightly reducing the Secchy disk has at the end of 2. In 26 is the largest measured transparency of water accumulation in Strezevo reservoir examined during nine years period. Maximum value of Secchy disk in 26 amounted to 7 cm, and it measured in June. Same year, the lowest transparency is measured in March (16 cm). At the beginning of 27, has a relatively high transparency of over 2 cm, in the spring months to decrease and reach a minimum of 74,12 cm in May. It has sharply increased in July (279 cm), and slightly decline in the months following reduced transparency of 1, 71 cm in November. 28 is characterized by the fact that May is the month with the smallest measured water transparency of 6 cm. There is expressed seasonal oscillation of transparency, as observed with greater clarity at the beginning of the year, reducing in the spring months, a sharp increase in July, to reach the maximum in August 28 (27 cm).followed slight decrease in the autumn months, and the end of the year with a transparency of about 2 cm. It is the same in 29 when the minimum value of Secchy disc is measured in May (1 cm), but now the largest peak and also the maximum amount of the transparency is measured in October (482 cm). Table 2 presents the average annual concentrations of nutrients and values of transparency in the water of reservoir in the period from 21 to 29. This table show that total concentrations of nitrogen and phosphorus are increasing from year by year. It is a consequence of the reaction of nutrient s increase in the reservoir as a consequence of the fact that the source of the nutrients in the water area (waste from villages, from animals etc), are relatively high in relation to the nitrogen and phosphorus compared. Specifically, NO2/3 * (mg) registered in this form, as measured only content of nitrates, while nitrites are under detection limit. Their representation in nine year period ranges from,878 mg/l (23) to,63 mg/l (28). Ammonia concentrations varied in the range of, 941 mg/l (22). Distribution of ammonia is highly variable regionally, seasonally and spatially depending on the level of productivity of the lake and the degree of contamination with organic matter (Wetzel, 197). The largest concentrations of inorganic nitrogen were found in 28 (.673 mg/l) and the lowest concentration of inorganic nitrogen was measured in 24 (,79 mg/l). As one of the most important nutrients, total phosphorus ranges from.122 mg/l (24) to.38 mg/l (27). Phosphoru s is one of the 2 essential elements which is needed for plant development (including algae),as a jerry -built

4 International Journal of Scientific Research Engineering & Technology (IJSRET), ISSN Volume 3, Issue 3, June component of nucleic acids, based on synthesis of enzymes and system for transferring energy at the cellular level (Reynolds, 1978). The categorization of the examined nutrients is according to the Decree of the classification of waters and waterways of the Republic of Macedonia (Official Gazete of R.M. no 18, ). Pursuant to this ordinance, according to the content of nitrates, the water from reservoir Strezevo is classifited in I class. According to the concentration of ammonia, water is IV class. According to the content of total phosphorus, water from the reservoir Strezevo is classified in I IV class. This means that the total phosphorus content is very variable in different years of researching. Data quality of the input water indicate that it is relatively stimulus for eutrophic processes, but after the transformation of the water quality, which is taking place in the reservoir, and stratification, the same processes of eutrophication in the accumulation are taking on lower level than expected, based on the concentration of the incoming nutrients 4. CONCLUSIONS On the basis of the presented transparency measurements and concentrations of examined nutrients, in the water of reservoir Strezevo from 21 to 29, we can draw the following conclusions: 1. According to the mean annual average water transparency in and 29 water satisfied the conditions for class. 2. According to the mean annual average water transparency in 27 and 28, water satisfied the conditions for IV class. 3. According to ten mean annual average concentrations of nitrate nitrogen, water satisfied the conditions for I class. 4. According to the mean annual average concentrations of ammonia nitrogen, water satisfied the conditions for IV class.. According to the mean annual average concentrations of total phosphorus, water is from I to IV class. All these points to the fact that water quality in the reservoir Strezevo, varies according to season and year. Although more of the parameters examined (which are not listed here) are in class I, there are parameters of class and IV indicating that is it the process eutrophication, which is characterized by negative effects on water quality. Because of this state of water quality in the reservoir Strezevo, it is necessary an emergency procedure to approach realization the implementation of measures to protect water quality in the reservoir. 8 I Fig.4. The transparency in the water of Strezevo reservoir during the investigation period (expressed in cm) Table 2. Annual average concentrations of nutrients and values of Secchy disc transparency in reservoir Strezevo (21-29) Year NO 2/3 * NH 3 inorga nic N total R (mg/ l) II IV V VI VII Secc hy disc (cm)

5 International Journal of Scientific Research Engineering & Technology (IJSRET), ISSN Volume 3, Issue 3, June Table 1. Transparency of water during represented by months (expressed in cm) month I II IV V VI VII V IX X XI XII REFRENCES 1- APHA AWWA WPCF.2.Standard methods for the Examination of water and wastewater 21th ed Beetter, G.193.Handbook for chemical investigation of waters. Hyg. Inst. Of Srbije nr.3 Belgrade pp.78. (In Serbian). 3- Krebs, C.J Ecology, The experimental Analysisof Distribution and Abundace, Fourth Edition. Harper Collins College Publishers. 4- Regulation for classification of water.1999.official Gazette of Republic of Macedonia, No 18/99. - Reynolds, C. S Phosphorus and the eutrophication of lakes a personal view in phosphorus in the Environment: its chemistry and biochemistry. Ciba foundation Symposium 7, pp Schnjorbel, J. 197.Methods for Hydrobiology (Freshwater biology), Pergamon Press. Oxford Wetzel, G. R. 197.Limnology. W. B. Saunders Co. Philadelphia. London, Toronto, pp Wetzel, R.G.1983.Limnology, 2nd edition.w.b. Saunders Company, Philadelphia, London, Toronto.