Water Quality of Some of the Belgrade Water Springs and Statistical Analysis of Nitrate Concentration

Violeta Cibulić1, Sanja Mrazovac Kurilić1, Vladanka Presburger Ulniković1, Luka Ivančajić3, Novica Staletović1, Maja Trifunović1, Lidija Stamenković2

 

1 University "Union-Nikola Tesla", Cara Dušana 62-64, Belgrade, Serbia; E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it

2 College of Specialized Professional Studies, Filipa Filipovića 20, Vranje, Serbia

3 Institute for Public Health Belgrade, Bul. Despota Stefana 54a, Belgrade, Serbia

 

Abstract

The manuscript is part of a groundwater monitoring program within the standard control measures for drinking-water health and safety on the territory of Belgrade. The paper presents the results of physical and chemical tests for the five most important spring water sources on the territory of Belgrade: Hajdučka Spring, Miljakovac Spring, Sakinac Spring on Avala, Saint Petka Spring-Monastery Rakovica and Saint Petka Spring-Kalemegdan. The assessment of the physicochemical analyses and results was carried out according to the Serbina drinking water quality standards (Rulebook on the Hygienic Correctness of Drinking Water). Results pointed out that, from a physicochemical water quality parameters point of view, the most analyzed spring water samples comply with the standards, but in some samples content of some heavy metals such as mercury and arsenic, significantly exceeds maximum allowable concentrations for drinking water. This paper also presents the results of testing for nitrate concentrations in the Belgrade spring waters (which have not exceeded MAC at any of the examined sites) and their statistical analysis. This paper presents the trend analysis of the nitrate content in Belgrade spring waters. For this purpose, the Man-Kendall test and linear regression analysis with the correlation calculation were applied. Based on the aforementioned analysis, it can be concluded that the data do not indicate the existence of a significant temporal or spatial trends.

Keywords: spring, groundwater, physicochemical characteristics, heavy metals, trend test.

Introduction

 

Monitoring of the health and safety of drinking water in the City of Belgrade is performed by the City Institute for Public Health. Groundwater monitoring program also includes sampling and analyses of water from total 30 natural springs on the territory of Belgrade, financed by the Secretariat for Environmental Protection of the City of Belgrade. (Water Law, Official Gazette of RS, No. 30/2010, 93/2012, 101/2016). In order for the water to be used for drinking safely, it must comply with physicochemical, microbiological and other standards, which are currently in R. of Serbia defined in the Ordinance on the Hygiene of Drinking Water (Official Gazette of RS, No. 42/98, 44/99).

The greatest problem with spring water is its microbiological correctness because these waters are, for the most part, not treated with purification treatment and final disinfection. The fact is that a large number of public fountains in Belgarde area have been insufficiently maintained in past years, especially regarding the regular cleaning of the water capture structures and maintenance of the surrounding area, with potential adverse effect on the quality of spring water. Previous studies pointed out that water quality of Belgrade public fountains is extremely variable and unstable with frequently recorded deviations in physicochemical parameters, primarily reflected in heavy metal concentrations (Baird, 1995).

Pollution by heavy metals is caused by the introduction, discharge or disposal of dangerous substances, energy or other agents in quantities or concentrations above the permissible limit values, thereby endangering human and environmental health (Kastori et al. 1997). The Regulation on Limit Values of Pollutants in Surface Water, Groundwater and Sediment, and Deadlines for Compliance ("Official Gazette of RS", No. 50/12) regulates the limit values of various substances, including heavy metals, as well as deadlines for achieving them.

When increased cocnentrations of metals is observed, it is necessary to distinguish between natural sources of metal and metal sources resulting from human activity. Metals in natural unpolluted sediments originate exclusively from the lithosphere, actually, from the mineral parts of the soil that make up rocks and minerals that make up the Earth's crust and wash into watercourses. The most important source of anthropogenic water pollution by metals is municipal and industrial wastewater discharged into natural recipients. Also, this includes water from cultivated agricultural and urban areas that pollute the land, and therefore the groundwater, as well as natural watercourses, thereby causing ecological and sanitary problems. However, for most metals, the quantities generated by anthropogenic activities have far exceeded the contribution from natural sources (Pettersson, 1993, Popović i Tričković, 1983). Whether the heavy metal infiltrates the groundwater depends on: the age of the aquifer (increase in age increases the possibility of mobilization), water flow velocity in the aquifer, pH values and redox potentials.

Heavy metals can be classified as toxic (As, Pb, Cd, Hg, Ni), potentially essential (V, Co) and essential (Fe, Cu, Zn, Mn ...). Their form, mobility, sorption and bioavailability depend on the physical and chemical conditions of the environment in which they are located, as well as the nature of the present chemical species in the environment with which they can interact (Poguberović, 2016). Their bioaccumulation or biomagnification characteristics present a significant danger to humans and above all, to the environment in general.

Transport of heavy metals in the natural environment is conditioned by:

  • physico-chemical characteristics of the contaminant (metal),
  • processes of transport in the environment and processes of transformation (abiotic and biotic) (Agbaba, 2008).

Once pollutants containing heavy metals are discharged into the environment they are distributed between particles of sediment, soil and water. Important chemical and biological processes that accelerate the input of pollutants through the food chain are the process of distribution between phases (defined by the distribution coefficient), the processes of metabolism and specific factors of bioaccumulation and bioconcentration.

In recent years, due to the excessive use of mineral fertilizers, there has been an enormous increase in the concentration of nitrates in the soil, from where they leach into the groundwater. From there, they enter the food chain. It was found that nitrates slowly move through the soil, their dissolution time in groundwater is very long. It is estimated that it takes about 20 years to determine their presence in water and to show their negative effect. It is considered that the effects of nitrate pollution will be present and will only become intense within the next few decades. In high concentrations may lead to toxicity in humans which can result in cardiovascular problems, methaemoglobinaemia... They oxidize hemoglobin into methemoglobin in the blood, which impairs oxygen delivery to tissue and leads to cyanosis. Otherwise, prolonged exposure to increased levels of nitrates and nitrites in humans leads to diuresis and bleeding of the spleen. (Baird, 1995)

Determination of nitrogen in water that occurs in the form of ammonia, nitrate or nitrite is of great hygienic significance, since these compounds are produced by decomposition of organic matter (protein, urea, etc.) under the influence of chemical reactions or under the influence of bacteria. Nitrates are nitric acid salts and represent the ultimate product of the oxidation of nitrogen compounds. The maximum permissible concentration for nitrates, expressed over nitrogen, is 10 mgN/dm3 of water. Nitrates naturally appear as part of the nitrogen cycle. The nitrite ion is very unstable and oxidizes to nitrate with the help of the nitrite oxidizing bacteria, Nitrobacter under the influence of oxygen in the aerobic zone. They are used in the food industry as a food additive, especially in meat and cheese. They are used as fertilizer and oxidation agents in agriculture and the chemical industry. Nitrates in water can also be evidence of fresh fecal pollution.

In the field of environmental protection, especially environmental monitoring, it is very important to detect trends among the data of the tested parameters. The application of trend analysis in environmental protection is broad, and one of the possibilities is to estimate the trend of pollution concentration over time. This paper investigates nitrate concentrations in water from the springs (public fountains) in Belgrade area.

 

General Review

Spring water is mainly used in its "raw" state, which means without prior purification and disinfection. Due to frequent variations in the quality of most spring water and despite the results that can demonstrate the chemical and microbiological correctness of the tested water samples, the use of water from these sources is not safe for human health (Ćerić et al., 1990). Figure 1 shows a map with marked geographical positions of five representative springs on the territory of Belgrade whose physico-chemical test results are presented in this paper. These are Hajdučka Spring (Fig. 2), Miljakovac Spring, Sakinac Spring on Avala, Saint Petka Spring - Monastery Rakovica (Fig. 3) and Saint Petka Spring - Kalemegdan Spring (Fig. 4).

 

fig01
Figure 1: Map of the geographical location of the representative springs on the territory of Belgrade.

 

Hajdučka Spring was built at the beginning of the 18th century and the records from that period mention the establishment of this spring in 1828. By the mid-nineteenth century, when the spring only had one pipe, it represented a kind of picnic area. More recently, Hajdučka Spring underwent restoration between 2001 and 2003. The spring area was renovated prior to the Second World War, and several minor repairs were made thereafter up until 2001. This spring, shown in Figure 2, is the only one on the territory of the City of Belgrade where sanitary protection zones are defined.

Miljakovac Spring is one of the rare sources of drinking water within the city of in Belgrade area. In 1975, a fountain was built in the park, which was named after a national hero Velizar Stanković.

Sakinac Spring is located on Avala Mountain, located approx 20 km south of the city of Belgrade. It was named after the sakas, two-wheeled horse cart with water barrels, which in the past was used to distribute drinking water to households. Water from the Sakinac Spring was used by Serbian industrialist Đorđe Weifert for beer production at his factory. Nowadays, water from this spring is used for drinking. It is mostly used by the local population, but also by numerous excursions, primarily due its low temperature, which gives it its refreshing properties. The water from the Sakinac. Spring is mostly used by the residents of surrounding settlements of Pinosava, Beli Potok and Zuce, but also by a large number of people from Belgrade.

 

fig02
Figure 2: Hajdučka Spring, Košutnjak.

 

fig03
Figure 3: Saint Petka Spring in Rakovica.

 

The Saint Petka Spring in Rakovica, shown in Fig. 3, is located close to the church of St. Petka in Rakovica, in southern part of Belgrade. The most common cause of the physicochemical inadequacy of this water is increased turbidity and the presence of heavy metals. Therefore, this water undergoes treatment to reduce critical concentrations of certain parameters. However, the samples of water for analysis shown in this paper were taken prior to treatment.

 

fig04
Figure 4: Saint Petka Spring in Kalemegdan.

 

The fountain of St. Petka in Kalemegdan fortress is located along one of the most famous sanctuaries of Belgrade (Fig. 4). Ružica Church is dedicated to St. Petka and the place where people from all over come to drink a glass of water from the spring. Many people consider this water healing and testify to its miracles. However, previous investigations confirm that this spring water has poor quality, and therefore, prior to use, it is treated with several tretamnet processes, including adsorption on activated carbon, membrane filtration on the principles of reverse osmosis and UV disinfection. Water treatment also includes remineralization o water.

 

Methodology

Systematic control of the quality of spring water on the territory of the City of Belgrade is performed by the Belgrade Public Health Institute which is a competent authority for spring water monitoring. Control of the hygienic correctness of spring water is carried out in order to protect the health of the population and to monitor the quality of groundwater sources that are used as an alternative source of water supply. The results are also one of the indicators for the assessment of the state of the environment. (Law on Sanitary Control, Official Gazette of RS, No. 125/04).

The program of controlling the quality of spring water includes 30 springs on the territory of Belgrade. Each month, basic physicochemical and microbiological analysis is performed on 15 spring water sources in the City. In the period from March 1st to October 30th, the quality control of spring water is carried out on 15 suburban springs. Once a year, physicochemical, microbiological and biological analyses are performed on water from all the springs. Based on the results of laboratory tests and knowledge of the sanitary and hygienic condition of the facilities and the surroundings of springs, competent authority issues an opinion on the possibility of using these water as drinking water from a health aspect.

Physical and chemical quality control of spring water is performed in accordance with:

  • The Rulebook on the Method of Sampling and Standard Methods for Laboratory Analysis of Drinking Water (Official Gazette of FRY, No. 33/78), and according to the predetermined dynamics;
  • The Rulebook on Hygienic Correctness of Drinking Water (Official Gazette of RS, No. 42/98, 44/99),
  • The Standard Requirements SRPS ISO 17025. (Law on Sanitary Control, Official Gazette of RS, No. 125/04).

Due to the limited space, test results from only five of the most important springs will be shown in this paper: Hajdučka Spring, Saint Petka Spring - Monastiry Rakovica, Saint Petka Spring - Kalemegdan, Miljakovac Spring and Sakinac Spring on Avala, shown in the Figs. 2-6.

In order to provide a high quality assessment of hygienic correctness and risk assessment of the spring water used for drinking, the Public Health Institute in Belgrade also carries out periodic analysis, which includes other hazardous and harmful substances in water:

  • heavy metals in spring water located close to the roads and industrial complexes,
  • pesticides in spring water that are surrounded by intensively cultivated agricultural land,
  • organic compounds (trihalomethane, aromatic hydrocarbons, chlorinated alkanes, ethene and benzene). (Artiola et al., 2004)

The content of aluminum, iron, manganese, copper, zinc, chromium, nickel, arsenic and mercury were tested according to standard test methods. (WHO, 2000). Pesticides and other specific organic compounds were tested according to standard methodology.

Detection of trends on the tested parameters is very important in the field of monitoring of environmental parameters. The applicability of trend analysis in environmental protection is in estimating the trend of pollution concentration over time. (Rosner, 2011)

In this paper, nitrate concentration trends in drinking water over time were studied. Two types of trend tests were applied:

  • hypothesis testing (Mann-Kendall test) (Cleveland, 1993)
  • linear regression (slope regression and data correlation) (Dixon et al., 1983).

In the process of data preparation for these analyses, calculations of the monthly and annual mean values of the analyzed parameters and the graphical presentation of the results were made (Box et al., 1978; Cleveland, 1993). All analyses were performed in Microsoft Excel. (Mac Berthouex et al., 2002)

Professional standards for the quality and safety of drinking water in public water facilities determined under expert supervision predict that the tolerance level of deviation in hygienic correctness of drinking water at the annual level is 5% for microbiological and 20% for physical and chemical defects.(Official Gazette of RS, No. 42/98, 44/99, Official Gazette, No. 37/2011.)

 

Results And Discussion

The results of the physicochemical tests of the water from the five examined springs are shown in the Table 1, and the results of specific organic pollutants from the extended analysis are shown in the Table 2. These are the mean annual values of the parameters tested in 2014. In all tested samples, the spring water is clear (0.2 NTU), odorless and with color less than 5°Co-Pt. pH value ranged from 7.0 to 8.5 which indicates a neutral to a weak alkaline reaction.

 

tab01

 

The analyzed spring waters are very different in their mineralization. The content of mineral matter, expressed as the content of total dissolved solids or TDS, ranges from about 60 mg/dm3 in the spring water of St. Petka-Kalemegdan up to ten times higher, 600 mg/dm3, in the water of Hajdučka Spring. Other values of total dissolved solids range from 450 to 529 mg/dm3. This is also confirmed by the conductivity values that are the lowest in St. Petka Spring - Kalemegdan, 86.7 μS/cm, and the highest, 900 μS/cm, in the water of the Hajdučka Spring, where the TDS value is the greatest. The content of organic matter is expressed as KMnO4 consumption, and according to the Rulebook on Hygienic Correctness of Drinking Water, the maximum permissible concentration is 8 mg/dm3. In the tested spring waters, the content of organic matter ranges from 1.9 to 2.4 mg/dm3. And in this case, the lowest value is in the St. Petka Spring - Kalemegdan, and the highest concentration is recorded in the water of Hajdučka Spring and Miljakovac Spring, although all these values are far below the maximum permissible concentration. Concentrations of chloride, nitrite and ammonia are low and far below the maximum permissible concentration.

In regards to heavy metals, the content of aluminum, iron, manganese, copper, zinc, chromium, nickel arsenic and mercury was tested and their concentrations are mostly at a boundary or far below MAC (WHO, 2000). Deviations were observed for As, the concentration of which is two times higher at the St. Petka Spring - Kalemegdan, 0.02 mg/dm3, and two and a half times higher in water from Sakinac Spring, 0.025 mg/dm3. The waters of Hajdučka Spring and Miljakovac Spring mercury concentrations were ten times higher, 0.01 mg/dm3. Lead concentrations at all three springs: Hajdučka, Miljakovac and Kalemegdan were equal to the MAC, and slightly below the MAC at the Sakinac and Rakovica springs, while the concentration of manganese is at the MAC level.

Within the scope of the extended analysis, specific organic pollutants were also examined. A whole range of organic pollutants in spring water is analyzed, most often resulting from anthropogenic activity. For illustration, Table 2 shows some of the results of these tests. It can be seen that all the parameters shown in the table are far below the MAC, and the same results are obtained for other numerous specific parameters.

 

tab02

 

Statistical analysis of nitrate monitoring data for spring water is based on the determination of average monthly values and average annual values of nitrate content for a period of five years, from 2009 to 2013, Table 3.

 

tab03

 

A graphic presentation of monthly nitrate content during the five-year period was given for five representative springs (Cleveland, 1993), Charts 1-5. On the most charts (springs), 2010 is the year with the highest concentration of nitrates, especially in March and April.

 

fig05
Chart 1: Monthly concentrations of NO3 (mg/dm3) in the Hajdučka Spring water in the 2009-2013 period.

 

fig06
Chart 2: Monthly concentrations of NO3 (mg/dm3) in the Miljakovac Spring water in the 2009-2013 period.

 

fig07
Chart 3: Monthly concentrations of NO3 (mg/dm3) in Sakinac Avala Spring water in the 2009-2013 period.

 

fig08
Chart 4: Monthly concentrations of NO3 (mg/dm3) at St. Petka Spring in Rakovica in the 2009-2013 period.

 

fig09
Chart 5: Monthly concentrations of NO3 (mg/dm3) at the Sveta Petka Spring in Kalemegdan in the 2009-2013 period.

 

Average annual values were analyzed for each spring using the Man-Kendall test, followed by regression analysis, to detect the increasing nitrate concentration trend. The same procedures were used for spatial analysis to detect the trend in the behavior of nitrate in spring water. (Kendall et al., 2006).

 

tab04

 

A time-decreasing trend was determined only for St. Petka Spring in Rakovica using Mann-Kendall´s trend test (Table 4). For other springs (fountains) it was established that there is no time trend in the behavior of nitrate concentration in the considered five years, and that there is no spatial trend of nitrate concentration for the analyzed springs.

 

fig10
Chart 6: Time dependence of nitrate content in St. Petka Spring in Rakovica in the 2009-2013 period.

 

The regression analysis of the nitrate spatial trend for the following four springs was based on information on the distance between the springs (Brownlee, 1960):

Distances:

Hajdučka spring – Miljakovac spring ≈ 2.72 km

Hajdučka Spring - St. Petka Spring, Rakovica ≈ 3.99 km

Hajdučka Spring - Sakinac Spring ≈ 9 km

Spring water from St. Petka in Kalemegdan was excluded from the analysis due to the fact that quality controls are done by sampling water after treatment.

 

fig11
Chart 7: Spatial dependence of nitrate content for the four springs in the 2009-2013 period.

 

Based on the application of the regression analysis, it was concluded that only St. Petka Spring in Rakovica shows a slightly declining trend in nitrate content. Other springs exhibited no trend, while the observed spatial trend shows a moderately strong linear upward trend.

 

Conclusion

The hygienic correctness of drinking water from the springs is controlled in order to protect the health of citizens and to monitor the quality of groundwater sources that are used as alternative drinking water supply sources. At the same time, these results are also represent indicators of the state of the environment.

From the aspect of basic and extended analysis of physicochemical parameters as well as specific organic pollutants these water sources correspond to the Regulation on Hygienic Correctness of Drinking Water. Main problem with these water sources is their microbiological quality because of their natural origins from springs that do not always receive the best treatment as they do not have defined sanitary protection zones, while water intake structures are usually insufficiently maintained. The purification filter set at the source of St. Petka in Kalemegdan provides satisfactory results in terms of water conditioning. Water from this source had in previous years been inadequate for drinking due to the increased concentrations of various chemical parameters (chlorides, nitrates, arsenic). A similar effect was achieved with the use of filters at the spring of St. Petka in the Rakovica Monastery where the water had previously been predominantly below standards, primarily due to increased concentrations of chromium.

However, with respect to heavy metal concentrations, the drinking water of the studied springs is of uneven quality. Only the Rakovica Spring water has a satisfactory quality in relation to the concentration of all the analyzed heavy metals, i.e. the concentration of all the measured heavy metals is below the MAC. The other springs have one heavy metal at concentrations greater than the MAC. Hajdučka and Miljakovac springs have mercury concentrations which are ten times higher than the MAC. The Sakinac and Kalemegdan springs have increased concentrations of arsenic with levels exceeding the MAC: Kalemegdan Spring being 2 times higher and Sakinac Spring being 2 and a half times higher.

Based on the physicochemical characteristics of the examined waters of these five springs, it can be concluded that it is necessary to perform regular monitoring which would include parameters for basic physical and chemical analysis, specific organic parameters within the extended chemical analysis of drinking water quality, as well as testing for heavy metals. Due to the increased concentration of some heavy metals as well as the very frequent microbiological contamination of these waters, it is necessary, through appropriate technological procedures, to purify these waters in order to achieve drinking water quality levels.

In addition to the need to conduct regular monitoring, it is necessary to determine the sources of heavy metals and the mechanisms by which they leach into groundwater, i.e. to prevent their further impact on the quality of drinking water in these springs.

In the field of environmental protection, especially monitoring of environmental parameters, it is very important to identify trends in the data of the tested parameters. The applicability of the trend analysis in environmental protection is broad, and one of the possibilities is to estimate the trend of pollution concentration over time, which was applied in this work in the case of nitrate concentration in spring water.

The nitrate content in water from five representative Belgrade springs, on which sampling was carried out over a period of five years from 2009 to 2013, in accordance with the Mann-Kendall test, does not show an upward trend, or cumulative effect. One of the reasons is the short period of time for the trend analysis, which should be more than a decade, but also the absence of major pollution. Unlike Mann-Kendall's test, a regression analysis has revealed a slight increasing trend of the nitrates in spring water from the urban zone to the suburban areas. The reasons for this may lay in the fact that suburban zones are dominated by households with small-scale agricultural production and uncontrolled use of pesticides, as well as by using inadequate septic tanks.

 

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