Chemical pollution monitoring of the River Pinios (Thessalia—Greece)

Journal of Environmental Management 76 (2005) 282–292 www.elsevier.com/locate/jenvman

Chemical pollution monitoring of the River Pinios (Thessalia—Greece) D. Bellos, T. Sawidis* Department of Botany, University of Thessaloniki, GR-54006 Thessaloniki, Macedonia, Greece Received 7 May 2003; accepted 4 January 2005 Available online 31 May 2005 Dedicated to Prof. Dr Ioannis Tsekos on the occasion of his retirement.

Abstract The impact of human activities and environmental factors on the fluctuation of chemical and physicochemical parameters along the Pinios River and its tributaries was studied. Their seasonal variations throughout the years 1996–1998 are also presented. Most of the parameters (physical or chemical) measured in this survey exhibited high spatial and temporal variability. High temperatures during the warm period, attributed both to meteorological conditions and to the geographical relief of Thessalia plain, cause a restriction of the water flow, an accumulation of organic matter and the depletion of the dissolved oxygen in the water. Conductivity and hardness are high during the warm and wet period for different reasons. At the seaward part of the river high conductivity and hardness values indicate extended admixture of seawater. COD values fluctuated seasonally. Among the studied stations along the Pinios River the most polluted was the area where the river has passed the city of Larissa. q 2005 Elsevier Ltd. All rights reserved. Keywords: Chemical parameters; Pollution; Rivers; Water quality

1. Introduction Rivers are dynamic systems and may change in nature several times during their course (e.g. from a fast-flowing mountain stream to a wide, deep, slowly flowing lowland river) because of changes in physical conditions such as slope and bedrock geology. They carry horizontal and continuous one-way flow of a significant load of matter in dissolved and particulate phases from both natural and anthropogenic sources. This matter moves downstream and is subject to intensive chemical and biological transformations (Goltermann, 1985; Admiraal and van Zanten, 1988). The surface water chemistry of a river at any point reflects several major influences, including the lithology of the catchment, atmospheric inputs, climatic conditions and anthropogenic inputs (Bricker and Jones, 1995). Identification and quantification of these influences should form an important part of managing land and water resources within a particular river catchment (Petts and Calow, 1996). * Corresponding author. Tel.: C30 2310 998292; fax: C30 2310 998389. E-mail address: [email protected] (T. Sawidis).

0301-4797/$ - see front matter q 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.jenvman.2005.01.027

Most data on chemical denudation rates in small catchments are currently available from northern temperate environments. Less is known about weathering within small catchments in temperate environments. On the other hand many of the world’s most severely polluted areas lie in temperate regions. The measurements in the Pinios River are among the lowest reported in the literature for riverine systems influenced mainly by urbanization, agricultural runoff and climatic changes (Sawidis et al., 1991; Moustaka et al., 1992; Fytianos et al., 2002). The Pinios River is the most important river in the Thessalia region; it supplies drinkable water and is being used for a variety of agricultural, industrial and recreational activities thus largely contributing to the economy of the region. The river runs through an area of grassland and mixed agricultural land. The hydrology of the catchment is slow and the river remains still unregulated. Human activities have affected the river system in numerous ways, for example, through deforestation, urbanisation, agricultural development, land drainage, pollutant discharge, and flow regulation (dams, channelisation, etc). Dams and water abstraction, which modify the hydrological regime, are present only in a few cases (e.g. Sugar dam). Since the turn of the century, the combined land and sea surface temperature averages have increased by

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approximately 0.5 8C on a worldwide basis (NOAA, 1994). This increasing temperature trend is thought to be a consequence of the increasing atmospheric concentrations of ‘greenhouse’ gasses, primarily carbon dioxide (Justic et al., 1996). This temperature increase will affect the global hydrologic cycle and the riverine runoff, increasing the evaporation over seas and oceans and transporting water vapor. Climate change, if manifested by increasing riverine freshwater inflow, may affect coastal and estuarine ecosystems in several ways. Changes in sea surface temperatures affect the vertical oxygen transport and create hypoxia or anoxia conditions in the bottom (Justic et al., 1996). The mass fluxes of riverine nutrients could have an immediate effect on the productivity of the coastal phytoplankton. Increased freshwater inflow changes the nutrient balance and subsequently the coastal phytoplankton communities. Climatic changes will affect river discharge and nutrient flux to the Sea. In the Mediterranean region, the changing temperate climate, with increasing temperature and scarce rains, causes a diversity of processes such as fluctuations in water flow, eutrophication and floods. Moreover the loss of surface vegetation due to frequent fires and overgrazing by sheep and goats causes erosion and desertification of the area of catchment. In such conditions erosive materials are the major input of inorganic N and P. Thus in the Mediterranean area rivers are more sensitive to the external factors in terms of inputs and climate change. In this climatic region, studies of chemical pollution of rivers are scarce and have focused mainly on France and a few from the Iberian Peninsula (Kagalou et al., 2002). Apart from the climate change, the Pinios River is largely influenced by intensive agricultural activities, domestic seawage (from the cities Tricala and Larissa) and wastes from a sugar industry, slaughter-houses and olive-presses. The river catchment is dominated by very intensive agriculture, with extensive agrochemical use and heavy soil erosion. The hills and mountains surrounding the Thessalia plain ensure that a high proportion of nutrients applied at high elevations run off across the floodplain into the river. In a previous study the chemical pollution along the Pinios River was shown to be largely dependent on external factors in terms of inputs and climatic change. In this work data on water quality ranged from 3.5 to 13.3 mg/l for DO, from 7.20 to 8.75 for pH, from 320 to 620 mS/cm for conductivity and from 9.2 to 19.8 mg/l for COD (Sawidis, 1997a). The pollution levels of the river in comparison with other water systems were found to be very high, due to climatic peculiarities of the Thessalia plain, especially during the warm period (Sawidis, 1997b). In the present study the fluctuation of chemical and physicochemical parameters along the river and their seasonal variation during the years 1996–1998 are presented. The sampling stations in this study were extended to the three main

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tributaries of the river, in order to have an overall view of the whole fresh water system. In this paper, an attempt was made to estimate the water quality of the Pinios River according to the proposed Directive of European Parliament and Council (2000/60) for monitoring physicochemical parameters (CEN/ISO standards). The purpose of this Directive is to establish a framework for the Community action to protect inland surface, transitional, coastal and ground waters. The physicochemical characteristics studied are: temperature, hardness, dissolved oxygen, pH, conductivity and COD.

2. Materials and methods 2.1. Study area The Pinios River is a system comprising both the main course and a number of tributaries that feed into it. The catchment area that the river system drains is Thessalia, the biggest hydrological basin in Greece (9.747 km2) where the Pinios River together with its tributaries is the unique receiver (Fig. 1). The average water discharge is 103 m3/s with high fluctuations between the winter and summer months. During the summer months, the Pinios River becomes a small and in some areas a very small river (Fig. 2). Moreover, the impacts of climate change are seriously aggravated by the geological relief of the area. The Pinios River together with the rivers Axios and Aliakmon are the most important freshwater inputs and contributors of organic matter to the semi-enclosed Thermaicos Gulf and the Aegean Sea. Thessalia is one of the most densely inhabited regions in Greece because it is a productive agricultural area. The region is surrounded, to the north, by Mount Olympus and Chasia, to the west by the Pindos Range, to the south by Mt Othrys and to the east by Mt Ossa. These mountains surrounding the Thessalia plain prevent air circulation. Mt Olympus and Ossa in particular, through which the Pinios enters the Aegean Sea, form a natural wall that separates the plain from the Aegean Sea. Fresh air masses are thus blocked from moving from the sea towards the Thessalia plain. During the summer period the atmospheric temperature sometimes reaches up to 46 8C in the city of Larissa. Nine sampling sites (stations) were established along the Pinios River and its tributaries taking into account their positions in relation to sources of pollution (Fig. 1). The aim was to include a wide spectrum of biotope types, geological deposits, urban and municipal effects, etc. Vehicular access to the river was the major determinant of sampling location. Across the main river (Pinios) the stations are: (1) Fotada, a relatively non-affected area, near the river sources. (2) Keramidi, a station that is polluted from the discharge of the municipal sewage of the city of Trikala (60,000 inhabitants) (3) Larissa, before the river enters the city of Larissa. (4) Sugar dam, after the city of Larissa (120,000 inhabitants).

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Fig. 1. Map of Thessalia (Central Greece) showing the studied river Pinios (stations: (1). Fotada, (2) Keramidi, (3) Larissa, (4) Sugar dam, (5) Itea and (6) Pyrgetos) and the tributaries Titarisios (station 7), Kalentzis (station 8) and Enipeas (station 9). The major pollution sources are located in stations 2 (city of Tricala) and 4 (city of Larissa).

2.2. Analytical methods Fresh surface water (from a depth of 0.5 m) was collected monthly from each site over a period of three years (1996– 1998) using 1 l polypropylene sampling bottles. The water samples were transferred in a portable refrigerator to the laboratory. The sampling program provided on a seasonal basis measurements of the physicochemical parameters of the river waters. Measurements were always carried out in the same order during the sampling day in order to keep to a minimum the fluctuations of the physical and chemical parameters caused by temperature differences. The first or second day of every month during the above-mentioned period was determined as sampling day. Sampling started at 08:00 and finished at 12:00. Particulate and dissolved matter was separated immediately by filtering samples through pre-combusted (4 h at 480 8C) and pre-weighed Whatman GF/F fiberglass filters (47 mm). Filtered samples were poured into Pyrex

pre-combusted 100 ml bottles and frozen immediately. Chemical analyses were carried out using APHA (1989) standard methods. The water samples were collected in triplicate and analysed. The dissolved oxygen was measured on site by means of a portable oxygenmeter, type WTW OXI-320. Measurements were calibrated with Winkler titration (Parsons et al., 1984). Hydrogen ion activity (pH), temperature and conductivity values were measured on site by a portable pH/8C-meter (Handylab 1 SCHOTT) and conductometer (Handylab LF 1 SCHOTT), respectively. Hardness was measured by the volumetric method with titration of T-Triplex B. COD values were measured by the ‘closed 180 160 140

Station 6 Station 3 Station 1

120 m3/s

In this station the treated municipal sewage and wastewaters from the industrial zone are discharged. (5) Itea, which is influenced by small industries. (6) Pyrgetos near the estuaries of the river in the Aegean Sea. (7) Tributary Titarisios, which originates from Mt Olympus and Chasia. (8) Tributary Kalentzis, which originates from Pindos range and (9) Tributary Enippeas, which originates from Mt Othrys. All of the above tributaries are polluted only by agricultural runoff.

100 80 60 40 20 0 J

M

M

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Fig. 2. Seasonal variation of water flow (mean values for the years 1996– 1998) in three main stations ((1) Fotada, (3) Larissa and (6) Pyrgetos) along the river Pinios. Data from local authorities.

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refluxed’ method according to APHA standard methods. All reagents used were p.a. (Merk, AG).

3. Results

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were observed near the cities Tricala (station 2) and Larissa (stations 3 and 4). After the city of Larissa (stations 5 and 6) the water temperature gradually decreased again. The tributary Enipeas (station 9) also showed high temperatures, while the lowest water temperature was detected in the tributary Titarisios (station 7).

3.1. Temperature 3.2. Hardness The fluctuation of the water and air temperature along the Pinios River and its tributaries is given in Fig. 3a. The seasonal variation of the temperature is given in Fig. 3b. Water temperature showed high seasonal variations and ranged from 4.1 8C during the winter (December 1996) to 30.1 8C during the early summer (June 1998). Beginning from the initial station (sources) the river was observed to become gradually warmer. The highest temperature values

The fluctuation of hardness in the surface waters along the river Pinios and its tributaries is given in Fig. 4a. The last station (Pyrgetos) was characterized of high hardness values. The tributary Enipeas (station 9) also showed high values. Seasonal variation of hardness is presented in Fig. 4b. Hardness ranged between 78 and 434 ppm CaCO3.

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Fig. 3. (a) Temperature fluctuation along the river Pinios and its tributaries. Right scale indicates the standard deviation values. (b) Seasonal variation of water and air temperature in the river Pinios and its tributaries.

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Fig. 4. (a) Hardness fluctuation along the river Pinios and its tributaries. Right scale indicates the standard deviation values. (b) Seasonal variation of hardness in the river Pinios and its tributaries.

3.3. pH The fluctuation of the pH values along the river Pinios and its tributaries is given in Fig. 5a. Station 6 (Pyrgetos), near the river mouth, showed the lowest pH values followed by the tributary Kalentzis (station 8). The seasonal pH variation is given in Fig. 5b. It is obvious that the pH was relatively stable among and within the stations during the year. It ranged between 7.01 and 8.57 mostly being very close to 8. 3.4. DO DO concentration varied from 1.9 (station 8, tributary Kalentzis, Oct. 1997) to 18.5 (station 6, estuaries, Aug. 1997) mg/l. The DO fluctuation along the river is shown in Fig. 6a and the seasonal variation in Fig. 6b. The tributary Titarisios (Station 7) and the first station (Fotada) exhibited

the highest values, while the lowest ones were observed in the tributary Kalenzis (Station 8). The bay’s waters were always oxygenated, with supersaturation at the surface waters of the shallow stations. During spring (May), the seasonal spring bloom occurred, accompanied by a high dissolved oxygen concentration and elevated pH values. 3.5. COD The COD values varied from 1 to 36 mg/l. In Fig. 7a the COD is shown along the Pinios River and its tributaries, while its seasonal variation in all the aquatic systems studied is shown in Fig. 7b. High values were observed in stations 4 (Sugar dam) and 5 (Itea) after the river has passed the city of Larissa. Among the studied tributaries Enipeas (station 9) also showed high COD values. Based on our measurements no clear correlation between seasons and corresponding COD values could be provided.

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Fig. 5. (a) pH fluctuation along the river Pinios and its tributaries. Right scale indicates the standard deviation values. (b) Seasonal variation of pH in the river Pinios and its tributaries.

3.6. Conductivity Conductivity distribution along the river Pinios and its tributaries (Fig. 8a) showed high values at the last station (Pyrgetos) and the tributary Enipeas (station 9). Seasonally (Fig. 8b) high conductivity levels were observed mainly during the warm period as well as during the wet period. Conductivity values ranged from 138 to 697 mS/cm.

4. Discussion 4.1. Temperature As expected, high water temperatures were observed during the warm period from May to September (Fig. 3b). These may be attributed to both the meteorological conditions and the geographical relief of the Thessalia plain. Thermal increase can also be caused by the removal

of trees and vegetation that shade and cool streams. This is more obvious in the shallow tributary Enipeas where the riparian vegetation is completely absent. Apart from the expected summer heat from the sun, human induced heat from cooling equipment (electrical power, steel, chemical) resulted in a thermal plume in the river. High temperatures were recorded near the cities Tricala and Larissa (Fig. 3a). It is likely that urban and industrial wastes result in thermal pollution. Water is often drawn from rivers for use as a coolant in factories and power plants. The water is usually returned to the source warmer than when it was taken. The high heat capacity of the water makes it an ideal cooling medium carrying away waste heat with relatively small increases in its own temperature. As heat-laden water is able to absorb large amounts of heat it raises the temperature of the aquatic environment. It is well established that the ranges of water temperature significantly affect the changes in physicochemical

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Fig. 6. (a) Dissolved oxygen fluctuation along the river Pinios and its tributaries. Right scale indicates the standard deviation values. (b) Seasonal variation of Dissolved oxygen in the river Pinios and its tributaries.

parameters. Thermal pollution increases the solubility of certain chemicals and generally decreases the solubility of gases especially the amount of dissolved oxygen (Fig. 6a and b). High temperature, during the warm period, can result in intensive evaporation and low water flow (Fig. 2), which many times leads to the accumulation of organic matter, responsible for oxygen depletion in the water (Justic et al., 1997). Waste heat can affect the life in water and results in changing the composition and physiology of species. Heat can accelerate biological processes in plants and animals by depleting oxygen in water (Foreman et al., 1997; Mayo and Noike, 1996). The vulnerability to disease increases, algal populations change and invasion of destructive organisms is expected. Even small temperature changes in a body of water can drive away the fish and other wildlife that were originally present near the discharge source and attract other species in their place (Sawidis, 1997a).

After the river passes the city of Larissa (stations 5 and 6) the water temperature gradually decreases again, especially after the contribution of the cold tributary Titarisios (station 7), which originates from the cold sources of Mt Olympus. The passing of the River Pinios through the Tempi valley, with additional sources of cold water and a large amount of trees on both sides where Platanus orientallis and Salix alba are dominant, results in the further cooling of water before the river reaches the estuaries. 4.2. pH pH values were higher than natural at the shallow stations. The lower pH values along the Pinios River (Fig. 5a) were observed in the final station (near the outfall of the river), which is affected by sea currents. Low pH values were also observed in the Kalenzis tributary. In both stations mentioned above (stations 6 and 8) the acidophilic

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Fig. 7. (a) COD fluctuation along the river Pinios and its tributaries. Right scale indicates the standard deviation values. (b) Seasonal variation of COD in the river Pinios and its tributaries.

aquatic moss Drepanocladus fluitans was the most abundant plant in this area. This species has long been considered to be an indicator of aquatic habitats with relatively high amounts of nutrients and neutral pH (Li and Vitt, 1994; Samecka-Cymerman and Kempers, 2001). Seasonal variation of the pH values (Fig. 5b) did not show great differences. The observed values were within the range to permit all the natural processes of aquatic life. pH variations and DO levels, in turn, regulate most of the biochemical and chemical reactions affecting water composition. Thus, an increase in the phytoplankton population (from March to July) produces an increase in the pH value and oxygen supersaturation due to high photosynthetic activity (Fourqurean et al., 1993; Kress and Herut, 1998). During this time the plant community of the river is dominated by the aquatic species Potamogeton nodosus (Poiret), Myriophyllum spicatum L. Ceratophyllum demersum L. and the alga Cladophora glomerata L. comprised the rest (Sawidis et al., 1991, 1995).

Apart from the photosynthetic processes, many human activities result in the net production of acidity, including use of nitrogen fertilizers and timber harvesting (Mayo and Noike, 1996; Sawidis, 1997a; Bellos et al., 2004). Since weathering is a major proton sink in most ecosystems, it is reasonable to hypothesize that the additional proton load imposed by human activities should result in increased rates of chemical weathering. This probably explains the low pH values in the tributary Kalenzis (station 8), which are associated with low DO. 4.3. DO The first station of the Pinios River (Fotada) and the tributary Titarisios (station 7) show high DO values (Fig. 6a). Both stations are situated near the sources where the river flux is more or less inclined resulting in a churning up of the water. On the other hand the shallow and horizontally flowing tributary Kalentzis (station 8) shows

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Fig. 8. (a) Conductivity fluctuation along the river Pinios and its tributaries. Right scale indicates the standard deviation values. (b) Seasonal variation of conductivity in the river Pinios and its tributaries.

the lowest values. The unexpected high DO values at station 4 (Sugar dam), after the river exits the city, are attributed to the waterfall created by the dam where there is an artificial oxygen enrichment of the falling water. During the warm period DO showed lower values (Fig. 6b). In high temperatures all water elements are in the state of maximum oxidation (C as CO2, HCO3 as CO3, N as NO3, S as SO4, etc.). Oxygen is reduced first, but when its concentration falls below a certain point, nitrates or nitrites are used as oxidants (Capblancq, 1989). The significant decrease in DO during the warm period coincides chronologically with a great increase in algal blooms causing degradation of habitat for other river life, and a change in the competitive balance between species leading to loss of biodiversity (Cooper et al., 2002). At the same time, various aquatic macrophytes form a very dense surface layer preventing the enrichment of water with oxygen (Babalonas and Papastergiadou, 1989).

During the spring bloom, there is an increase in phytoplankton growth and increased consumption of nutrients (NO3CNO2, NH4, PO4), while in the winter, because of low phytoplankton concentrations the nutrient contents remain high in the water. During the extreme dry summer period, nutrient concentrations are at their highest values reaching 2.4 mg/l for PO4–P, 80.5 mg/l for SO4, 22.1 mg/l for NO3–N and 0.98 mg/l for NO2–N (Bellos et al., 2004). Fertilizers and other nutrients used to promote plant growth on farms and in gardens encourage the growth of algae and plants in water (eutrophication). After the summer period, the plant matter and algae die and settle underwater, decomposed by microorganisms (Sawidis, 1996). In the process of decomposition, these microorganisms consume DO in the water. Oxygen levels may drop to such dangerously low levels that oxygen-dependent animals in the water, such as fish, die.

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4.4. COD High values of COD indicate water pollution, which is linked to sewage effluents discharged from town, industry or agricultural practice. The two stations 4 (Sugar dam) and 5 (Itea), after the river passes the city of Larissa, show elevated COD values (Fig. 7a). The tributary Enipeas (station 9) also displayed high COD values thus indicating a significant load of organic matter mainly from farms and gardens. Temporal variability in COD measurements and other parameters (such as hardness, conductivity, DO, nutrients, etc.) in the temperate climate of the Thessalia plain could be largely explained by the variability in water discharge (Fig. 2). Values decreased during periods of increased water discharge. The seasonal variation of COD (Fig. 7b) presented abrupt fluctuations during the year due to the external manipulation of the river. The input of anthropogenic contaminants (from point discharges mixing with urban and agricultural runoff) causes distinct, but variable, COD concentration peaks, responsible for increasing the concentrations in nutrients and organic carbon in the fresh surface waters of the river. Most of the organic matter is processed by stream fauna consumption. In temperate climates, the development begins in the autumn, when the fallen leaves from the riverside vegetation accumulate in the watercourses. The importance of processing depends on several factors in the environment such as temperature and pH. 4.5. Conductivity and hardness Conductivity and hardness give information about the concentration of dissolved salts. The leaching of chemical fertilizers spread on agricultural lands by rainwater also causes high values of both parameters. At the seaward station (Pyrgetos), high conductivity and hardness values indicate admixture of seawater (Fig. 8a). It seems likely that the deeper water layers at these stations were dominated by the estuarine salt wedge (Admiraal et al., 1992). High values were also recorded in the tributary Enipeas (station 9) and the initial stations (Fotada and Keramidi) of the Pinios River. Human activities and the nature of geological deposits through which the river flows are the two main reasons for the high values observed. In the Mediterranean area most rivers run over calcareous substrata, which induce strong mineralisation of water. High conductivity or hardness represents natural conditions even at the source. The high conductivity values of the tributary Enipeas (station 9) are probably attributed to the variations in the geochemical influences of this river. This river shows high hardness values as well. According to Olsen’s classification (Olsen, 1950) on the basis of conductivity, waters with conductivity values between 250 and 1000 mS/cm are rich in electrolytes and are

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characterised as eutrophic. Our results for all studied stations generally belong to this range. Big seasonal differences in conductivity or hardness values were not evident. High values (Fig. 8b) were expected during the warm period, due to low water flow (Fig. 2), but the leaching of fertilizers and other agrochemicals caused abrupt peaks, which indicated an external manipulation of the river influenced by unexpected inputs. Under storm run-off events conductivity and hardness concentrations increased suddenly and reached a maximum within a short period of time. The major cause of high nutrient concentrations is the chemical fertilisers leaching from terrestrial systems after heavy rainfall (Bellos et al., 2004). In Thessalia alone more than 230,000 tons of fertilizers and 2000 tons of agrochemicals are annually being used which ultimately end up in the Pinios River. The consequences of the massive input of nutrients are extremely dangerous for the Mediterranean and especially for the Aegean Sea into which the Pinios River flows. Being a closed sea and one of limited extension, the Aegean Sea is unable to deal with the massive input of chemical pollutants that more or less uncontrollably enter it. Nearly every year, phenomena known as red tides and mucilaneous waters are evident.

5. Conclusion In the Mediterranean region the river Pinios is largely affected by great temperature differences measured during hot and cold weather periods. High summer temperatures and the intense need of water at this period of the year result in a restriction of water flow and subsequently in the accumulation of organic matter and the depletion of dissolved oxygen in the water. Intensive agricultural activities, uncontrolled use of agrochemicals and domestic sewage affect the nutrient balance. Hence most of the physical and chemical parameters exhibit high spatial and temporal variability.

Acknowledgements We wish to thank the Dipl. Chem. Mr Sotiris Beltsios for his assistance for measuring the water specimens at DEYAL chemical laboratories and the evaluation of recorded data, and the ETECO Water Technology Company for financial support.

References Admiraal, W., van Zanten, B., 1988. Impact of biological activity on detritus transported in the lower river Rhine: an exercise in ecosystem analysis. Freshwater Biol. 20, 215–225.

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