Danube - River of Cooperation

 

Water Quality, Sediment and Aquatic Organisms of the Danube Prior and After NATO Air Strikes

by Vesna Martinović-Vitanović and Vladimir Kalafatić [1]

plenary lecture at the XI International Conference "Danube - River of Cooperation", November, 17-19 2000

 

Abstract

After the destruction of the Novi Sad and Pancevo Oil Refineries, Pancevo Petrochemical Complex and Fertiliser Plant numerous toxic substances poured into the Danube and endangered its flora and fauna. The consequences of war destruction have been studied within the narrow and the broader zone of influence of the above industrial complexes. These studies included ecological, ecotoxicological and genotoxicologic investigations of Danube water, sediment and biota. The results of these investigations together with the literature data collected through the long-term studies performed in the same area prior the NATO bombing were used to estimate the endangerment of river from the biological point of view. Such an estimation represents a basis for undertaking measures to recover and protect the river after the war has ceased.

 

Introduction

In the spring of 1999, upon repeated bombardments of the oil refinery in Novi Sad and the petrochemical complex at Pancevo town, a catastrophic pollution occurred, resulting in disturbances of the Danube aquatic ecosystem, endangerment of the environment and biota. The consequences were of interest not only for the public in Yugoslavia, but also in other countries the Danube flows through, especially the Balkan countries and those situated downstream from the region exposed to military activities. It is of a special importance to emphasize that the bombing imperiled the Danube section that includes the largest Yugoslav National Park "Ðerdap" (Martinović-Vitanović et al., 1999 a, d).

Modern warfare, war technology and methods of waging war destroy the environment. The bombing of Yugoslavia was chemical warfare with the endeavour to bring about an ecological catastrophe. This statement stems from the fact that chemical, petrochemical, petroleum and other industrial facilities and storage areas filled with hazardous and harmful substances were targeted in a planned and deliberate manner, resulting in the release of thousands of tones of hazardous matters into the environment. This caused ecological damage of enormous proportions (Tosović, ed., 2000). Although no precise gradation exists for this type of man-made catastrophe, since this was the world's first encounter with such a strategy of waging aggressive warfare, the direct and local consequences can be evaluated with certainty as being catastrophic, and some of them will definitely be long-lasting and will endanger not only FR Yugoslavia but the broader region as well.

Owing to the combustion of large amounts of chemicals, harmful and hazardous substances, Yugoslavia experienced extreme but short-lived air pollution, and owing to leaking non-inflammable substances or inflammable substances that did not burn, there was long-term pollution of the soil and surface and ground waters. The pollution in these zones, especially in the Danube River basin is a hazard for the further degradation of the environment, and a risk for the human health. In addition to the immediate consequences which were primarily caused by explosions, fires and the release of toxic substances into the environment, the long-term consequences are of greater importance owing to contamination of the environment by slowly decomposing chemicals.

On the eve of the war and particularly after an impending state of war was declared, considerable measures undertaken in order to prevent chemical disasters. These included: moving hazardous and harmful substances away from industrial zones, moving chemicals to several places around industrial facilities and in smaller quantities in order to minimise the consequences of any accident, neutralising or destroying hazardous and harmful matters and suspending operations in some facilities and plants that operate with harmful materials.

In addition to these preventive activities that continued during the war, ecological investigations were made in the Danube River Basin targeted by NATO. The environment was continually monitored during and after the war in order to diminish the immediate consequences and undertake measures to protect environment, lives and human health. (Ristić, ed., 1999; Tosović, ed., 2000).

The Yugoslav most qualified institutions and experts were engaged to work with the Balkan Task Force (BTF members were appointed by the UN organisation for environmental protection - UNEP). It is quite certain, however, that the degree and consequences of pollution cannot be precisely determined based on a short investigative "campaign" which can be only understood as an initial attempt by international institutions to establish the degree and consequences of pollution caused by destruction in FR Yugoslavia.

This paper presents the results of investigations on the state of the environment in the Danube River basin, and an evaluation of the consequences of NATO bombing. In order to enable a comparison of the state of the environment prior and after the war, the paper presents the quality of watercourse in endangered locations prior to the air strikes.

The Danube, one of the most significant international rivers, flows through Yugoslavia in its middle and partly in its lower course (total length 588 km). It has been limnologically studied in detail including the Yugoslav section of the course (Martinović-Vitanović & Kalafatićc, 1995). In addition to the basic scientific interest for studies of the Danube that involve examinations of hydrobionts, preservation of biodiversity and the aquatic ecosystem as a whole, special attention has been paid to investigations of water quality because of increasing eutrophication and pollution (Protić, 1939; Milovanović, 1965; Liepolt, ed., 1967; Illies, ed., 1967; Živković, 1968, 1973; Mišić et al., 1976; Nedeljković, 1979; Janković, 1978; Petrović, 1973, 1983; Janković & Jovičić, eds., 1994; Jovičić & Jovanović, 1994). Within the framework of systematic control of surface water quality in the region of Belgrade performed during the last two decades, river water quality in the City area was regularly determined (Martinović-Vitanović & Kalafatić, 1987, 1988; Martinović-Vitanović et al., 1997, 1999 b, c; Jakovčev, 1987, 1988; Tanasković et al., 1998). These studies are of special interest not only for maintaining the quality at the surface drinking water intake near Vinca settlement, which supplies the Belgrade Water System, but also for evaluating the anthropogenic impacts on the aquatic ecosystem (Kalafatić et al., 1989). The investigations of the Danube are particularly important because of the long-term changes in hydrological regime induced by damming the river and the formation of the hydropower reservoirs Djerdap I and Djerdap II. These accumulations have been an object of complex limnological studies from the very beginning (Milovanović, 1973; Živković, 1975; Petrović, 1975, 1978; Martinović-Vitanović & Kalafatić, 1990). Their influence, i.e. slowing down the river flow rate registered upstream to Slankamen village (1215.5 km of the river course) represents a topic of study on the basic watercourse, especially in the Belgrade region where the Danube becomes additionally loaded with different pollutants originating from urban and industrial wastewaters. In the 80s, the Danube river water quality was examined at the spot where the river receives wastewater from the petrochemical complex at Pancevo town (Obusković & Kalafatić, 1983; Kalafatić et al., 1984).

During 1986/87 complex limnological studies were performed in the yugoslav part of the Danube. The aim of these investigations was to established the Danube water quality and the degree of eutrophication. One of the sampling spots was at Novi Sad (Janković & Jovičić, eds., 1994).

After destruction of the "Pančevo" Oil Refinery, Petrochemical Plant and Fertiliser Factory that led to the introduction of different toxic substances into the Danube imperiling aquatic biota, hydrobiological investigations were initiated with the aim of monitoring the effects of bombing in the region and Danube river sections closer to and more distant from the aforementioned industrial complex. It is worth mentioning that at the time of military activities and pollutant discharge from the destroyed units of the industrial complex into the Danube, the water level of the river sections studied was extremely high and water discharge exceeded 6,000 m3 s-1.

Within the scope of ecological studies of the aquatic ecosystem, abiocen (monitoring of physico-chemical parameters of the Danube water and sediments, as well as of dangerous and harmful substances discharged into the environment upon bombardment) and biocen (composition and structure of plankton and benthic fauna communities) were examined. Ecotoxicological studies were aimed at establishing cumulative effects of toxicants, i.e. bioaccumulation of harmful matter in molluscs, fish and ichthyophagous birds. Genotoxicological investigations focused on the effects of the Danube water pollution, i.e. the continued presence of genotoxic substances in the Danube five months after the bombardment of the industrial zone in Pancevo town.

These studies together with the investigations of the Danube carried out for many years in the zone of the City of Novi Sad, Belgrade and Pancevo town represent the basis for estimating the threat to the river from the biological point of view, recognition of the present status and the undertaking of possible measures aimed at protection, restoration and revitalization of the Danube.

 

Study Area, Material and Methods

During the war starting from April 5, 1999 to June 8, 1999 the Oil Refinery - Novi Sad was bombed twelve times and was hit by 269 missiles.

Fire and the effusion of crude gasoline, leaded gasoline, crude oil and oil derivatives resulted in a technological and chemical disaster that polluted the surface and ground waters and the atmosphere, and the combustion led to the release of large amounts of hydrocarbons.

During the NATO bombing that destroyed the storage and pipeline installations, a total of 73,569 t of oil and oil derivatives were destroyed. In addition to damaging the technological installations, most of the oil and oil products burned in the fire. A great deal of the Oil Refinery's storage space was destroyed. Around 5,000 t of derivatives and around 18,500 t of oil were destroyed in the Yugoslav oil pipeline, and a great number of the storage tanks were totally destroyed. It is estimated that around 90% (66,212 t) of the total amounts of destroyed oil and derivatives burned, around 9.9% (2,283 t) leaked into the surrounding soil, and around 0.1% (73.6 t) leaked into the waste water canal. Around 130 t of the leaked amount are assumed to have returned to the tanks in this manner.

During the bombing 95% of the production and processing installations, numerous pipes and pumps to transport oil and oil products were destroyed or damaged (Tosović, ed., 2000).

On August 24, 1999, within the framework of joint activities with the BTF technical mission ecological investigations were performed in the zone of accidental discharge of harmful substances from the Oil Refinery - Novi Sad and in the vicinity of water intake sources.

Sampling sites were selected bearing in mind the nature of the specific substances that leaked into the watercourse and their affinity towards suspended detritus and shoreline sedimentation.

Locations upstream (I - 1,254 km) and downstream (II- 1,252 km) from Novi Sad and the point at the confluence of the Danube-Tisa-Danube (DTD) canal into the Danube (III) were chosen as references to determine the influence of the leaked oil and derivatives from the bombed refinery on the quality of the Danube River water, regardless of whether the pollution leaked from the oil terminal into the DTD canal or went through waste water canal directly into the Danube (Fig. 1). The characteristics of the flow in the shoreline zone on the left bank are generaly suitable for the formation of a large sediment layer and benthic communities, which enabled collecting samples on selected locations.

Within the scope of ecological studies, the first examinations in the zone influenced by the discharge of harmful matters from the industrial complex at Pancevo town into the Danube were initiated on April 28, 1999 after repeated actions of NATO air forces over this area. They were continued on May 18, 1999 and after the war ceased on July 1, 8 and 22, then on August 11 and 25 and October 15, 1999.

From the southern industrial zone of Pancevo, through the wastewater canal, the Danube was loaded with large amounts of toxic materials: 200 t of ammonia, 1,000 t of 1,2-dichlorethane (EDC), 70 t of 33% hydrochloric acid, 0.2 t of mercury, 40 t of sodium hypochlorite and 85 t of polyvinyl chloride (PVC). Around 62 t of crude oil and other derivatives burned for the most part or leaked into the canal (37,700 t of crude oil, 6,200 t of different types of petrol, 350 t of diesel fuel, 7,480 t of heating oil, 6,600 t of heavy vacuum oil, about 230 t of liquid petroleum gas, 80 t of benzene, 1,200 t of kerosene and 1,900 t of other derivatives and unspecified products mixed with several tenth tonnes of substances for fire extinction). After the bombing, undetermined amounts of ammonium nitrate and mono ammonium phosphate as well as other raw materials from the Fertiliser Factory (NPK plant) were flushed into the wastewater canal due to the heavy rain. Owing to the bombing, the wastewater treatment plant in Pančevo southern industrial zone stopped working. It is located in the Petrochemical complex and is designed to treat wastewater mechanically, chemically and biologically before its release into the canal. This plant released 98,229 m3 of wastewater from the petrochemical complex and 69,761 m3 of wastewater from the oil refinery into the canal. This water contained hazardous and harmful substances from these factories (Tanasković et al., 1999; Tosović, ed., 2000).

The samples were collected from locations up- and downstream from the wastewater canal of the industrial complex at the place of its discharge into the Danube, as well as from the canal itself.

Sampling was performed along the left riverbank and in the middle of the river course, at the river section from the mouth of the river Tamis (1154 km) up to 1148 km of the river Danube course in the following manner: location I, representing a "pure", control section was situated upstream from the canal (1153.4 km); downstream from the canal - locations II (1152.6 km), III (1151.5 km, left riverbank) and V (1151.5 km, in the middle of the river course by a sand river island) and location IV in the canal itself. Investigations at these locations included only the closer zone of the accidental pollution (Fig. 2).

Subsequently, it turned out that with regard to the amount and properties of the discharged substances it is possible to expect disturbances of the aquatic ecosystem in a far longer Danube section and with a time lag. Therefore, the consequences of the war operations were followed on a downstream river section (1158 - 1075.5 km), Banatska Palanka - Ram profile (1077 km) representing the most distant spot where the experts of the BTF also collected samples (Martinović-Vitanović & Kalafatić, 1999, 2000 a, b, c; Martinović-Vitanović et al., 1999 d; Tripković & Gavrić, eds., 1999; Tosović, ed., 2000).

These additional examinations were performed at the following locations: the profile upstream from Ada Zilovo river island, 1091 km - location VI; the profile downstream from Zavojska Ada river island, 1083 km - location VII; Ada Čibuklija a sunken river island, a swamp within the Danube river course itself, from 1082.5 to 1078.5 km - location VIII; the profile at Banatska Palanka village - Ram village, 1077 km - location IX and the profile at 1075.5 km of the Danube course - location X (Fig. 2).

Sampling of both river water and sediment, at the Banatska Palanka - Ram section were performed on July 8 and August 12, 1999 when aggression was terminated. The samples were collected along both the right and left riverbanks, as well as in the middle of the river course. In addition to the parameters connected to the effects of NATO aggression, all other standard parameters for the estimation of water quality were determined.

On August 25 together with the BTF mission water, sediment and biota (macrozoobenthos) of the Danube were tested in the Pancevo zone (samples were taken from the canal too) and at the Banatska Palanka - Ram profile. The investigations were made at the same locations at which samples of sediment surface layers of the canal and the Danube were taken during and immediately after the NATO bombing. Unlike earlier testing, a sample of undisturbed sediment was taken in the canal about 100 m from its confluence with the Danube. The testing zone at the Banatska Palanka - Ram profile covered the left and the right bank, 100 m in length and up to 100 m in width from the central line. A special probing device took samples of the sediment core, which should enable reconstruction of pollution in the prior period. In this regard reconstruction of the intensity of pollution by specific substances that adsorb onto sediment particles assume the sediment layers have been undisturbed over time, i.e. excludes the migration of deposits brought by changes in the river's flow.

Hydroecological studies included examinations of plankton and benthic fauna components (Martinović-Vitanović et al., 1999 a; Martinović-Vitanović & Kalafatić, 1999, 2000 b, c). These investigations were primarily focused on the composition and structure of communities. Standard limnological methods were applied for collecting the samples in the field and their processing under laboratory conditions (APHA, 1980; Lind, 1979; Felfoldy, 1974).

The samples for monitoring physico-chemical parameters of water and sediments, as well as for determination of toxicants in biological materials were collected simultaneously and in collaboration with members of the Public Health Institute, Belgrade, who analysed water and sediments and examined accumulation of pollutants in hydrobionts (Tanasković et al., 1999; Tripković & Gavrić, eds., 1999; Tosović, ed., 2000).

Determining the saprobity indicators using Sladecek's saprobity system (Sladecek, 1973) enabled the calculation of saprobity index S by the Pantle & Buck method (Pantle & Buck, 1955), and the determination of water quality (YUFROW, 1985).

Over 100 samples were collected for qualitative and quantitative analyses of phyto- and zooplankton, and 35 samples were examined for chlorophyll a (Chl a). Benthic fauna samples were collected along the left riverbank using equipment after Eckman and 40 samples were collected. The material was fixed in situ with 4% formaldehyde.

Ecotoxicological investigations were aimed at determining cumulative effects of toxicants, i.e. bioaccumulation of harmful matters in molluscs, fish and ichthyophagous birds. During May 1999 over 100 samples of biological material were collected at 1148 km of the river course and downstream, and during July and August 1999 about 35 samples were collected at the Pancevo and Banatska Palanka - Ram locations. Bearing in mind the nature of the specific substances that leaked into the watercourse and their affinity towards suspended detritus and shoreline sedimentation, where favorable conditions exist, sites were selected to sample the mussels jointly with the BTF technical mission.

Genotoxicological examinations of the effects of the Danube pollution i.e. the presence of genotoxic compounds in the river water were performed applying the Allium test for the analysis of chromosome aberrations. Toxicity level of the river water samples collected during October, 1999 at 1148 km of the river course was also estimated by a root growth test (Fiskesjo,1985; Vujošević et al., in preparation). This test was recommended by the Royal Swedish Academy of Science (1973) and GENE-TOX Program (Grant, 1982).

 

Results and Discussion

State of the Danube River prior to NATO Bombing

Hydrochemical investigations

During the period under investigation, water quality was controlled within systematic testing on the following profiles, among others: Novi Sad (1,259 km), Slankamen (1,215 km), Višnjica (1,162 km), Smederevo (1,117 km) and Ram (1,077 km). Targeted testing was made in the Belgrade zone from the aspect of ecological research and the protection of drinking water supply sources on the profiles: Stari Banovci (1,191 km), Zemun (1,173 km), Bela Stena (1,160 km), Vinča (1,145 km) and Brestovik (1,127.5 km).

During the five-year period, the Danube River section from Novi Sad to Ram had an average mercury concentration of 0.3 mg/l with a maximum concentration of 4.9 mg/l registered in 1994 upstream from Novi Sad.

The average concentration of mineral oils in this section is 44 mg/l but excessive petroleum hydrocarbon pollution was registered within maximum concentration reached 1,112 mg/l at Vinča in 1994 and 415 mg/l at Stari Banovci in 1998.

Maximum concentrations of polycyclic aromatic hydrocarbons (PAHs) were recorded at Bela Stena in 1997 and reached 0.10 mg/l, while the average value was 0.04 mg/l.

Polychlorinated biphenyls (PCBs) were not found in the water in measurable quantities durin the five-year period. Targeted testing included analyses of the content of mercury (Hg), polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) in mussels and sediment (Tosović, ed., 2000).

The maximum mercury content in sediment was 0.7 mg/kg dry matter, registered in 1986 at Vinča, while the tissue of the mussels Unio sp. had a maximum content of 0.40 mg/kg dry matter. The sample was collected at Brestovik in 1991.

During 1998, samples of sediment and mussels did not register the presence of PCBs and PAHs.

Hydroecological investigations

Plankton
The Danube's plankton includes species and varieties from the folowing groups: Bacillariophyceae, Chlorophyceae, Cyanophyceae, Euglenophyceae, Xanthophyceae, Dinophyceae, Chrysophyceae, Protozoa, Rotatoria, Cladocera, Copepoda, Lamellibranchiata and Nematoda.The community is of the type Bacillariophyceae-Chlorophyceae-Rotatoria. Based on saprobiological analyses of plankton, the Danube's water quality had a saprobity index S ranging from 0.70-1.90 minimum to 2.30-2.60 maximum. The Danube's water in the investigated section was primarily within acceptable limits, and occasionally outside the prescribed quality (Martinović-Vitanović et al., 1999 b; Martinović-Vitanović & Kalafatić, 2000 b; Tripković & Gavrić, eds., 1999).

Benthos
The Danube's macrozoobenthos community consists of the groups: Oligochaeta, Gastropoda, Bivalvia, Chironomidae (Diptera), Nematoda, Isopoda, Decapoda and Amphipoda. There are fewer instances of Hydrozoa, Trichoptera, Odonata, Diptera - Ceratopogonidae and Tabanidae, while findings of Ephemeroptera, Coleoptera and Colembolla are quite rare. Species that are adopted to and tolerant of organic pollution are favoured and appeared in highly dense populations within the biotope along the riverbank where there is primarily silt, on sections greatly exposed to the influence pf organic pollution. The populations noted were uniform with a small number of species dominating.
Analyses of the composition and the structure of macrozoobenthic communities of the Danube River in Belgrade region in the period 1996-1998 confirm previous findings regarding to high degrees of organic pollution (Jakovčev, 1987, 1988; Martinović-Vitanović et al., 1999 c).
Most tested sites had the absolute domination of members of the family Tubificidae (Oligochaeta), with the exception of several probes with an increased share of members of Gastropoda or Hirudinea. Most often members of the group Oligochaeta made up more than 50% of the total density of the community, and in some locations their share reached 99.9%. Total community density on the investigated section of the Danube ranged from 2,222 ind. m-2 to over 106 ind. m-2. In general, there is a higher density in river bottom fauna communities in sites downstream from the confluence of the Sava into the Danube than in the control section. The results of saprobiological analyses of benthic fauna communities indicate that the quality of the Danube in the Belgrade region was outside the prescribed limits. The saprobity index S varied from 2.60 to 3.35 (Martinović-Vitanović et al., 1999 c; Tosović, ed., 2000; Tripković & Gavrić, eds., 1999).

 

State of the Danube River after NATO Bombing

In order to understand the processes and development of water pollution caused by the warfare, it is important to analyze precipitation and hydrological characteristics at the tested locations and river sections during the bombing and after the end of bombing up until the situation was recorded with the BTF technical mission in August 1999 (Tosović, ed., 2000).

Owing to precipitation and snowmelt in the upper parts of the Danube basin and its tributaries where the water reserves in snow were at a histirically maximum level of 200% average, a wave of flooding formed at the end of February that reached values above 6.000 m3 s-1 at Novi Sad, 10.500 m3 s-1 at Pančevo and 11.000 m3 s-1 at Ram. After a brief decrease in flows, a new wave of flooding was formed in the middle of April that reached a maximum at the end of May and beginning of June. From the mid-June to mid-August water flows on the Danube dropped slightly, but were still above the average for that time of year. During the activities by the UNEP-BTF mission, the Danube flows corresponded to the average for that period and were 3.000 m3 s-1 at Novi Sad and 4.350 m3 s-1 at Ram.

Hydrochemical investigations
Studies during the war and upon termination of bombing

Novi Sad
In order to determine the impact of the destroyed Novi Sad Oil Refinery on water pollution in the Danube, on the biota and the possible endangerment of the "Ratno ostrvo" water source, investigations were done on May 5, 1999 upstream and downstream from the Refinery outflow (Tosovic, ed., 2000). Chemical testing of the water indicated that all samples contained concentrations of mineral oil above MPC (0,050 mg/l) and a maximum value of 0,124 mg/l was registered immediately downstream from the Refinery outflow. The concentrations of PAHs were within the limits of class II river water.
The sediment had concentrations of mineral oils ranging from 30 mg/kg to 293 mg/kg. Qualitative analysis established the presence of hydrocarbon series of the n-alkane type. There was a high presence of phthalate and series C>20 and C>30 and cyclohexane derivatives. The nature of n-alkane series indicates pollution with heavy fractions of petroleum.
All samples contained polycyclic aromatic hydrocarbons (anthracenes, pyrenes, phenanthrenes, etc.).

Pančevo
In the samples collected on April 28, 1999 ten days after the discharge of ammonia into the canal (location IV) its concentration in water samples from the canal was 37.3 mg/l and in the Danube water (locations II and III) 2.0 mg/l. It is certain that the ammonia concentration at the time of the incident was significantly higher and accompanied by an oxygen deficit, resulting in death of fish in the canal, as well as in the Danube downstream from Pancevo. Due to a total oxygen deficit in the canal, the ammonia concentration decreased very slowly as judged by its levels in water samples taken later on.
The concentration of 1,2-dichloroethane (EDC) during the first sampling even reached 25.5 g/l in the canal water, while downstream from the spot it joins the Danube it was 7.1 g/l (location II). In the samples collected on May 18, 1999 EDC concentration in the river water was below the limits of sensitivity of the method (0.1 mg/l), while that in the canal it was about 30 mg/l. In water samples collected 0.5 m above the river bottom, EDC concentrations were up to four times higher than in the samples taken 0.5 m under the surface.
As a consequence of oil and oil derivatives discharge from the Oil Refinery into the canal, the levels of total hydrocarbons (CxHy), and polycyclic aromatic hydrocarbons (PAHs) were significantly increased already during the first sampling.
The concentration of CxHy in the canal water samples was 1.28 g/l to be decreased in the samples collected later, but still the values ranged around 1.0 mg/l. In water samples collected at the spot situated immediately after the mouth of the canal (location II), the concentration of CxHy was found to be 314 mg/l during the first sampling. During the second (May 18) and the third sampling (July 1, 1999) the concentrations of hydrocarbons had decreased to below 1 mg/l.
PAH concentrations in the canal water were almost the same during the first and the second sampling (15,10 mg/l and 14,10 mg/l, respectively). Danube river water collected during the first sampling downstream from the canal mouth contained PAHs in concentrations significantly exceeding permissible values for river waters (6.30 mg/l to 1.54 mg/l and 2.19 mg/l to 1.30 mg/l, in the surface layer and near the bottom, respectively).
Water from both the canal and the Danube collected during the 3rd (July 1) and 4th sampling (July 22, 1999) did not contain increased PAH levels. Canal water taken during the first sampling and river water taken in the following samplings downstream from the canal (locations II and III, July 22 1999) contained increased levels of linear alkyl benzenes (LAB) (350.2 mg/l and 128.5 mg/l respectively).
Water samples taken either from the canal or the Danube did not contain increased mercury concentrations.
Sediments collected from the canal during the first three samplings contained 889.1 mg/kg, 149.6 mg/kg and 195.7 mg/kg EDC, respectively. In the samples collected on July 22, 1999 EDC concentration was found to be under the detection limits (1,0 mg/kg). In the Danube sediments taken from locations II and III, EDC in concentrations of 384.3 mg/kg and 206.3 mg/kg respectively, was detected only during the first sampling. In the samples of sediment collected downstream from the canal at location II, EDC level was 1.3 mg/kg.
The level of total hydrocarbons in the canal sediments ranged between 3.1 mg/kg and 766.4 mg/kg, maximum concentration being recorded at the first sampling. It is interesting to note that the sediments taken at locations upstream from the canal contained total hydrocarbons in concentrations decreasing with time (387.3 mg/kg; 191.5 mg/kg; 95.1 mg/kg and 29.5 mg/kg).
Sediment samples from the Danube collected downstream from the canal (1152,6 km and 1151,5 km) were also polluted with total hydrocarbons and their concentrations decreased with time. Also, with longer distance between the location and the canal, lower total hydrocarbon concentrations were found. In all sediment samples taken from the Danube and the canal, concentrations of PAHs exceeded those usually found in these types of waters. In the first canal samples PAH level was found to be 11.9 mg/kg. It gradually decreased to 865.6 mg/kg in the sample taken on July 22, 1999. The situation with the Danube sediment was somewhat different. Upstream from the canal mouth PAH concentrations varied greatly from 18.2 mg/kg to 2.0 mg/kg, but without any regularity. Thus, the lowest concentration was registered on July 22, while the highest one was found on August 25, 1999. The same pattern of PAH concentration changes was recorded at the locations situated downstream from the canal mouth, maximum concentration being 9.8 mg/kg.
Mercury levels in the Danube sediment samples were rather low. In approximately 50% of the samples Hg concentrations were under detection limits, while in the others they were below 1 mg/kg. Maximum concentration of this toxic metal was 1.15 mg/kg. Only in the canal sediment samples were mercury concentrations exceeding 1 mg/kg recorded, maximum level being up to 3.5 mg/kg.
The presence of PCBs in water and sediment samples of both the canal and the Danube was not detected.

Banatska Palanka - Ram
Laboratory studies of the samples taken from the Banatska Palanka - Ram river section showed that concentrations of mineral oil, PAHs, PCBs, EDC and mercury never exceeded maximum permissible concentrations (MPC) for class II river waters (Water Legislation, 1982; YUFROW, 1985).
Sediment samples taken only along the right and left riverbank revealed the consequences of pollution with mercury, oil and derivatives. Maximum concentrations were as follows: mercury - 0.28 mg/kg, mineral oil - 371.7 mg/kg and PAHs - 454.2 mg/kg. The presence of EDC and PCBs was not recorded in sediment samples.

Investigations in collaboration with the BTF mission

Novi Sad
Within the framework of joint activities with the BTF mission, investigations of the water and sediments were done in samples collected upstream and downstream form Novi Sad and in the immediate vicinity of Oil Refinery and water intake sources of the City Waterworks.
The concentrations of total hydrocarbons upstream and downstream from Novi Sad were quite high, particularly in the lower layers of water where they went up to 200.0 mg/l, while the contents of polycyclic aromatic hydrocarbons (PAHs) ranged from 0.04 to 0.09 mg/l. The concentrations of polychlorinated biphenyls (PCBs), highly volatile hydrocarbons, lead and mercury were on the border of sensitivity of the analytical methods used. The increased hydrocarbon content on this profile confirms the existance of pollution in the upstream river. The water quality in the profile just before the DTD canal was primarily the same as in the upstream control zone.
The water at the confluence of the DTD canal contained 235 mg/l of total hydrocarbons which certainly results from the leaked oil derivatives at the bombed refinery terminal (Tosović, ed., 2000).
The water sample at the profile downstream from the Novi Sad, the confluence of the DTD canal and the refinery collector outflow, had a total hydrocarbon concentration of mg/l, which is on the same order of magnitude as the water tested upstream.
Testing a river's sediment enables the reconstruction of events and pollution in the river, since sediment holds onto specific substances that are characteristic of the pollution, unlike the same substances that are freely transported in the downstream current.
In the profile upstream from Novi Sad and the refinery leakage, total hydrocarbons in the sediment were 4.15 mg/kg, polycyclic aromatic hydrocarbons were 0.19 mg/kg, and lead was 8.2 mg/kg dry matter, which confirms prior pollution in the river from the upstream part of the Danube basin owing to insufficient protection on the water.
Acording to mass spectrum analyses of the chemical compounds adsorbed in the sediment, the primary pollutant is petroleum.
An analysis of the surface layer of sediment in the profile downstream from Novi Sad shows the results of the petroleum and derivatives leaking from the DTD canal and refinery collector caused by the bombing and resulting from the shutdown of the separation system in the industrial complex. The high concentration of total hydrocarbons of 8.79 mg/kg and PAHs of 0.364 mg/kg dry matter confirm this.
The lead concentration of 25.0 mg/kg, three times higher than the upstream profile, is due to pollution from petrol additives in this zone. Other specific substances were within the limits measured in the upstream profiles and concentrations did not exceed 1.0 mg/kg dry river sediment.
The highest concentration of petroleum hydrocarbons of 92.6 mg/kg was found in the DTD canal sediment where the highest lead content was also found, 29.2 mg/kg (Tosović, ed. 2000).
These concentrations are all indisputably the direct result of NATO bombing on the quality of water and sediment in this part of the Danube, and are traces of the accidents which reached a culmination right after the end of the warfare.

Pančevo
Testing indicated that the Danube water in the Pancevo zone contained a high concentration of total hydrocarbons, particularly in layers above the bottom where it was - 113 mg/l at location I. This can be linked to all upstream events such as bombing of the "Oil refinery" complex in Novi Sad and the transport of pollution in the downstream river flow.
The concentrations of mercury, ammonium ions, PCBs and PAHs were within the usual limits for this section of the river or were below the detection limit. Water samples from the canal contained leaked EDC (28.6 and 42.3 mg/l) but it was not found in the Danube water samples from the downstream profile.
Qualitative-quantitative analysis detected the presence of PAHs originating from petroleum and its derivatives. The highest measured concentration was 0.10 mg/l. The surface layer of the canal and Danube sediment in all tested zones showed the presence of total hydrocarbons: at location IV - 8.6 mg/kg dry matter, location I - 6.0 mg/kg and location II - 7.5 mg/kg, respectively. Mass spectrum analysis confirmed their petroleum origin.
The highest concentration of mercury in the surface layer of the sediment in the canal of 2.82 mg/kg dry matter indicates the consequences of leakage from the bombed industrial plants. The highest concentration of mercury found in the 10-20 cm layer was 13.5 mg/kg. Bearing in mind the specific weight of mercury and mercury compounds its presence can be linked to the NATO bombing.
An analysis of the core probes from the sediment of the canal indicated high concentrations of total hydrocarbons (70-80 cm - 19.1 g/kg) and PAHs (70-80 cm - 157.5 mg/kg) in all layers. There was no noted regularity in changes in the concentrations of total hydrocarbons and PAHs with increase in the depth of the sediment. The interdependence between concentrations of total hydrocarbons and PAHs was clearly expressed.
Polychlorinated biphenyls were not found.
Based on mass spectrum analyses of the undisturbed sediment and the composition of chemical compounds, it can be concluded that the dominant pollution is of petroleum origin.

Banatska Palanka - Ram
Testing for specific substances in the water at this profile did not reveal increased total hydrocarbon concentrations, PAHs, PCBs and the soluble forms of mercury and lead compared to upstream profiles.
The contents of specific substances - adsorbed hydrocarbons, PAHs and lead in the sediment were increased, particularly in surface samples of silt on the right side of the river (Ram) where the speed of sedimentation was greater and the sediment was richer in fresh sedimentation material. Polychlorinated biphenyls, highly volatile hydrocarbons and mercury were not found in the Danube sediment at the Banatska Palanka - Ram profile.
Analysis of individual segments of the sediment core indicated considerable amounts of adsorbed hydrocarbons, PAHs and mercury. This pollution can be connected with the emission of pollutants in the prior period throughout the river basin upstream from Ram.

Hydroecological investigations
Studies during the war and upon termination of bombing

Owing to the direct penetration into the wastewater canal of the southern industrial zone of Pancevo and in the Danube enormous amounts of harmful and hazardous substances endangered hydrobionts. A water management service inspection on April 19, 1999 noted dead fish downstream from Pancevo. Dead fish were recorded all the way to Kovin and Kostolac, with a considerably greater amount on the left bank of the river. During the first sampling on April 28 a large number of dead fish were found in the canal and immediately downstream in the Danube (location II). Dead birds and fish, completely covered with oil, were registered in the canal. Oil covered all the shoreline vegetation, reeds and willows. Also, on May 28, at location VI (Ada Zilovo) the current carried a large number of aquatic snails in the process of decomposition.

Plankton
During the investigations from April to August, in the vernal and summer period, the plankton community of the Danube in the examined zone was characterized by the presence of organisms from the following groups: Bacillariophyceae, Chlorophyceae, Cyanophyceae, Euglenophyceae, Dinophyceae, Protozoa, Rotatoria, Cladocera, Copepoda, Lamellibranchiata, including Nematoda representatives brought into open water from the littoral by water circulation.
Under conditions of high water level, a typical potamoplankton community characteristic for large lowland rivers, such as the Danube in its middle and lower course through Yugoslavia, was maintained. With respect to qualitative composition, Bacillariophyceae and Rotatoria were dominant, while Chlorophyceae, Cladocera and Protozoa were subdominant groups. Other groups were represented by a lower number of taxa. The plankton community of the Danube belongs to the Bacillariophyceae-Chlorophyceae-Rotatoria type (Martinovic-Vitanovic & Kalafatic, 1987; Martinovic-Vitanovic & Kalafatic, 1988; Martinovic-Vitanovic et al., 1997; Obuskovic & Kalafatic, 1983; Kalafatic et al., 1984; Martinovic-Vitanovic et al., 1999a). Quantitative analysis of the Danube plankton in the examined zone showed that Bacillariophyceae and Rotatoria, were dominant groups, Chlorophyceae, Lamellibranchiata and Copepoda being subdominant. Exceptionally, during July, Lamellibranchiata i.e. larvae of the shellfish Dreissena polymorpha Pall. represented a dominant group.
Total abundance of algae ranged from 83 Ind. cm-3 during April at location II to 3,848 Ind. cm-3 during August at location III.
Minimum Chl a content was recorded in river water samples collected in July (location V) and it was 4.2 mg m-3, while the maximum of 70.4 mg m-3 was found in water samples collected at location I in August.
Zooplankton density varied between 16 Ind. dm-3 (location II, April), and 334 Ind. dm-3 (location III, July), the larvae of freshwater mussel D. polymorpha making up 86.2%.
Due to a high water level, high water discharge and water circulation (main current along the left riverbank), no regularity in plankton distribution from the surface to the bottom was recorded in water samples collected during May 1999. Keeping in mind that the wastewater canal was contaminated during NATO aggression with pollutants of higher specific gravity compared to water (e.g. the specific gravity of EDC is up to 2.5 times higher), water samples were taken at the depth of 0.5 m under the surface and above the bottom, which is not a standard procedure for river systems. This was done with the aim of determining possible pollutant effects on composition and density of phyto- and zooplankton populations. The high water discharge of the Danube at the time of the NATO aggression led to complete water mixing from the surface to the river bottom and as a consequence, no significant differences were observed in the abundance of plankton communities along the vertical water column.
Also, no significant differences in either plankton diversity or abundance were observed along the river section examined.
Such a status of plankton communities was expected because of the high water discharge at the time of examination. This was the reason that no significant differences either in the composition or the structure of plankton communities were recorded in the locations situated upstream and downstream from the spot where the wastewater canal joins the Danube.

Benthos
During the studies presented here, the potamobenthic community, characteristic for middle (and partly lower) course of the Danube was recorded. Analyses of this material revealed somewhat higher diversity than expected20, 21, 48. Nine faunistic ecological groups were present, ranging from 3 to 6 per location and 22 taxa ranging from 5 to 12 per location were identified. The recorded taxa usually have a wide range of distribution being typically rheophilic, pellophilic, psamo-pellophilic and phyto-rheophilic forms. These forms are usually found in the examined section of the Danube river course. They are mainly eurivalent forms, tolerant to organic pollution. The Oligochaeta group with 13 species, six of which belong to Tubificidae and Naididae families, one taxon being from the Aelosomatidae family, was characterized by the highest species diversity. Also, two representatives of each Gastropoda, Bivalvia and Amphipoda and one representative of the order Coleoptera were recorded. Chironomidae, Odonata and Nematoda were determined only to the family, order or type.
The highest diversity registered during the present studies was recorded in May (seven groups and 15 different taxa), while in other periods of investigation, the number of taxa was lower and relatively uniform.
An analysis of the spatial distribution of macrozoobenthic organisms during all testing periods indicated a slight drop in the number of registered groups and taxa from the upstream towards the downstream locations.
Total density varied from 3,464 Ind. m-2 (location I) to 86,879 Ind. m-2 (location V). The distinct dominance of Oligochaeta was noted in the entire tested area, except at location V and upstream from the canal - location I where Gastropoda dominated. Tubificidae were the most represented organisms, particularly Tubifex tubifex Müll. and the Limnodrilus species. Litoglyphus naticoides C.Pf. (Gastropoda) also had a considerable share of the total community density among other representatives of the macrozoobenthos. No benthic fauna was noted at sites in the canal that were close to the wastewater outflow, while a small number of Oligochaeta were found close to the confluence. The quantitative composition of the macrozoobenthos and the abundance of the most important species indicate the presence of organic pollution in water, interstice and sediments. The dominance of the mentioned Tubificidae species and L. naticoides is an important indicator of the presence of biodegradable substances in the aquatic environment. The slight drop in diversity in the section exposed to the effects of pollution can be linked to the rise in concentrations of pollutants.
The quantitative relations of the most represented species of Oligochaeta - T. tubifex, Limnodrilus hoffmaisteri Clap. and Limnodrilus claparedeanus Ratz. - their spatial distribution and the considerable fluctuations noted in their population density can indicate the presence of pollutants. Upstream from the wastewater canal, during the first three sampling periods, T. tubifex was dominant in relation to the Limnodrilus species, while downstream from the canal the quantitative relations changed and the Limnodrilus species became dominant. Downstream from the wastewater canal there were no specimens of T.tubifex, while the L.hoffmeisteri population density was 5,022 Ind. m-2.
There was no substitution of dominant species in August but the abundance of T. tubifex decreased significantly.
Analyses of the relations among the benthic fauna communities upstream from the canal in terms of saprobity put the Danube water in the class of moderately polluted. The composition and structure of benthic communities and saprobiological analyses at the Banatska Palanka - Ram profile indicated the presence of organic pollution. The saprobity index S varied from 2.93 to 3.23.
In addition to the above-mentioned changes in the community level, the toxic substances that reached the Danube water caused changes at the organismic level in the benthos. A survey of individual probes with the exception of samples taken in April, indicated a relatively large number of fragmented Oligochaeta, remains of body covering with chaetae, and unusual appearance of dark, almost black content in the intestinal tracts of these organisms which might indicate changes in the silt probably resulting from the effects of pollution. The discarded rear body parts of representatives of the group Tubificidae and the specimens with "new" regenerated tails noted in considerable number (up to 31% of the total abundance of Oligochaeta) indicated the presence of self-destruction which occurs in unfavorable stressful conditions. The loss of the tail could be a biomarker of contamination by heavy metals (Lucan-Bouche et al., 1999) The examined samples also contained Oligochaeta with ruptured tissue, primarily in the head region, which could also be the result of pollutants in the substrate, interstice and lower layers of water.

Investigations in collaboration with the BTF mission
Benthos

Novi Sad
Four tubificid species (Oligochaeta), two species of Bivalvia and one taxon each from the groups of Gastropoda, Amphipoda and Nematoda were found in the sample collected upstream from Novi Sad. The density of the benthic fauna community was 20,176 Ind. m-2. Representatives of Oligochaeta particularly Limnodrilus hoffmeisteri (58% juveniles), were dominant, half of the total number being juvenile forms.
The next groups were recorded downstream from Novi Sad: Oligochaeta (4 species), Bivalvia (1 species), Gastropoda (1 species) and Chironomidae. The density of community was 7,020 Ind. m-2. The oligochaetes were dominant, L. hoffmeisteri being the most abundant. Benthic sample taken at this location contained a lot of empty mollusc shells.
Following groups were found in the DTD canal: Oligochaeta (10 species), Gastropoda (3 species), Bivalvia (2 species), Hirudinea (2 species), Hydrozoa (1 species) and Trichoptera (1 species). There were also representatives of Nematoda and Chironomidae. Tubificidae (6 species) and Naididae were recorded among the Oligochaeta. Community density was 7,285 Ind. m-2. Among dominant Oligochaeta species L. hoffmeisteri had the highest population density. Macrozoobenthic community found in the DTD canal was far more diverse than in examined sites on the Danube, near Novi Sad. The sample taken in the Canal contained many Tubifex tubifex juveniles and the molluscs were exclusively juveniles. Almost 90% of the Hirudinea individuals had not reached the adult stage. Many empty mollusc shells were noted. In sites that were downstream from the accidental polluting at Novi Sad certain changes in the composition and structure of the benthic fauna were observed which might have been caused by pollutants. (Martinovic-Vitanovic & Kalafatic, 1999; 2000 a, b; Martinovic-Vitanovic et al., 1999 a, d). The effects of the pollution can also be seen from the remains of mollusc shells in samples taken at locations II and III that were directly affected by the pollution.

Pančevo
The greatest number of species recorded in the Danube site upstream from Pancevo belonged to Oligochaeta (5), followed by Bivalvia (2), while Gastropoda and Amphipoda had one species each. There were also representatives of Nematoda. Community density was 14,842 Ind. m-2. Oligochaeta (Tubificidae) L. hoffmeisteri and T. tubifex dominated. Lithoglyphus naticoides had the greatest population density of Gastropoda. Immediately downstream from the wastewater canal there was less diversity compared to the other sites, namely, five groups with eight taxa. Oligochaeta dominated here as well with four species. The density of the benthic community was 3,111 Ind. m-2. Downstream from Pančevo at 1149 km, six species of Oligochaeta were recorded. The oligochaetes were also quantitatively dominant. The density of macrozoobenthos was 16,531 Ind. m-2. No organisms were found in the wastewater canal.
This part of the Danube also showed the unfavorable effects of pollution on the structure of river bottom fauna. The leakage of pollutants into the canal had a lethal effect on the biota. Downstream from the canal, at location II, changes in the benthic community structure were noted possibly caused by pollutants. The macrozoobenthos community in this site was considerably less dense with as much as a 95.7% decrease in the abundance of T. tubifex compared to the control sample.

Banatska Palanka - Ram
Small fractions and detritus prevailed in the substrate along the bank of the Banatska Palanka - Ram section. More diverse benthic fauna was noted than in the upstream parts of the Danube. Four groups with 10 taxa were recorded along the left bank, while seven groups with 15 taxa were found on the right bank. The density of the benthic communities was 27,729 Ind. m-2 and 14,441 Ind. m-2, respectively. Limnodrilus species belonging to oligochaetes dominated. The substrate on both sides had many mollusc shells and heads and other chitinous parts of insect bodies. An entire layer of crushed shells was noted on the right bank. The large number of organism remains and damaged shells clearly indicated the lethal effect of pollution after the wartime destruction in the broader surroundings.

Ecotoxicological investigations
Studies during the war and upon termination of bombing

The first results of ecotoxicological studies revealed no bioaccumulation of harmful matters in fish tissues. Such data were quite expected, since the samples were collected during May, shortly after pollutants were discharged into the Danube.

The studies performed on samples collected during July and August, 1999, revealed the accumulation of PAHs, PCBs, lead, cadmium, zinc, copper and mercury in the tissues of shellfish, fish and ichthyophagous birds (cormorant Phalacrocorax carbo).

In the tissues of the shellfish Anodonta anatina caught downstream from Pancevo town (locality III), accumulation of PAHs (362.7 mg/kg), lead (0.46 mg/kg), cadmium (0.53 mg/kg), zinc (90.7 mg/kg), copper (0.63 mg/kg), chromium (0.57 mg/kg) and mercury (0.33 mg/kg) was recorded. In the tissues of the shellfish Unio tumidus found in the river profile Banatska - Palanka Ram (locality IX), in August, 1999, a pronounced accumulation of PAHs (263 mg/kg), was registered as well as that of lead (0.34 mg/kg), cadmium (0.45 mg/kg), zinc (84.2 mg/kg), copper (0.47 mg/kg) and mercury (0.17 mg/kg).

The analyses included muscular tissues of benthophagous and prey fish species of about the same age (2+ and 3+): Carassius auratus gibelio B. , Abramis brama L., Cyprinus carpio L., Acipenser ruthenus L., Silurus glanis L., Stizostedion lucioperca L. The concentrations of PAHs, zinc, copper, chromium and marcury were lower than those found in the shellfish. These data suggest that the shellfish accumulate heavy metals and especially PAHs much more efficiently evan for three orders of magnitude and PAHs concentrations recorded in fish muscular tissue did not exceed 1 mg/kg. No significant locality-related (localities II and IX) or diet-related differences were observed. Bioaccumulation of arsenic, lead, cadmium, nickel, PAHs and PCBs in fish muscles was not recorded. All of these matters occurred in the concentrations below detection limits of the method employed.

Hepatic tissue and pectoral muscle of a cormorant (Phalacrocorax carbo) specimen caught during July 1999 at river profile Banatska Palanka - Ram was also analyzed. Cormorant, as an ichthyophagous bird represents an extremely suitable object for indirect determination of heavy metals and specific organic pollutant accumulation in fish. Hepatic tissue contained much higher concentrations of copper, mercury, PAHs and PCBs than the muscles (8.3 mg/kg vs. 4.8 mg/kg, 13.75 mg/kg vs. 2.65 mg/kg, 275.2 mg/kg vs. 10.5 mg/kg and 12.5 mg/kg vs. <1.0 mg/kg, respectively). It is important to emphasize that this was the first record of PCBs presence in the tissues of an ichthyophagous bird although this presence in the tissues of an ichthyophagous bird although this kind of the studies was performed for many years (Martinović-Vitanović et al., 1999a; Martinović-Vitanović et al., 1999d).

Investigations in collaboration with the BTF mission

In the investigated section of Danube during the BTF mission shell samples were tested for PAHs, PCBs and mercury (Tripković & Gavrić, eds., 1999; UNEP/UNCHS Balkans Task Force, 1999; Tosović, ed., 2000).

Novi Sad
All samples of Sinanodonta woodiana had considerably higher contents of PAHs compared to concentrations in Anodonta anatina specimens. The highest concentrations of PAHs in Sinanodonta woodiana specimens were found upstream from Novi Sad. Among examined PAHs, naphthalene has the highest concentration of 2.63 mg/kg.
In most samples the next PAHs were detected: pyrene, phenanthrene, anthracene, benzo(b) and benzo(k)fluoranthene and benzo(a)pyrene.
It is characteristic that the highest concentrations of carcinogenic PAHs, benzo(b) and benzo(k) fluoranthene and benzo(a)pyrene were recorded upstream from Novi Sad.
Maximal PAHs concentration of 5.7 mg/kg was recorded in Sinanodonta woodiana collected upstream from Novi Sad.
The concentrations of mercury in all shell samples from the investigated area were from 0.16-0.21 mg/kg.
Polychlorinated biphenyls were not found.

Pančevo and Banatska Palanka - Ram
In the investigated section of the Danube (Pančevo and Banatska Palanka - Ram profile) during the BTF mission, mussel samples were tested for PAHs, PCBs and mercury. The highest value of PAHs in Sinanodonata woodiana (Lea) was found downstream from Pancevo at 1149 km (3.84 mg/kg). The A. anatina sample also downstream from Pančevo had the highest concentration of PAHs (2.96 mg/kg). By far the highest concentration of PAHs was found in a sample of U. tumidus at Banatska Palanka (5.26 mg/kg).
Polychlorinated biphenyls were not found.
The concentration of mercury in all shell samples ranged from 0.10-0.22 mg/kg.

Genotoxicological investigations

The degree of toxicity of water samples from the wastewater canal and the Danube upstream and downstream from the southern industrial zone of Pancevo was assessed by means of Allium cepa root length values in Allium test. Samples from localities I and III didn't show toxic effects. Clear inhibition of growth, compared to the control sample, was produced by sample from the locality II.

Genotoxic effects shown as the percent of chromosome aberrations are the smallest in the upstream sample I, even smaller than in the control. The sample from the locality II is the only one which is producing statistically significant increase in number of chromosome aberrations in comparison with control sample (X2(1)=10.7, p<0.001). However, upstream sample is significantly different from the both the second sample (X2(1)=11.19, p<0.001) and the third sample (X2(1)=4.6, p<0.05). Second and third sample do not differ significantly (X2(1)=3.00, n.s.).

From the results of our testing it is clear that both toxic and genotoxic effects of the Danube water are resulting from the water coming from the canal even five months after the chemicals leaked into the canal. Absence of these effects in upstream sample proves this. Positive results obtained in the test should be considered as a warning of risk present both for human health and for water environment (Vujošević et al., in preparation).

 

Conclusions

  • War activities that led to the destruction of large industrial complexes in the regions of Novi Sad and Pančevo town resulted in discharge of huge amounts of different pollutants into the Danube represent real ecocide. With regard to environment, the consequences of destruction of chemical plant complex in the City of Novi Sad and Pančevo town are expressed at local and regional level and can be classified as disastrous. Their influence at a global level is not negligible because of transfer and transformation of both the processes and the effects to more distant areas.
  • Pollutants originating from destroyed industrial complex of Novi Sad and Pančevo were transferred to downstream sections of the Danube up to Ram and further into the Djerdap accumulations. A part of the pollutants reached the Danube estuary and the Black Sea. A portion of the heavy naphtha fractions precipitated on the river bottom and remained on the river banks, but most of them were absorbed on suspended particles and precipitated on the bottom of river bed.
  • Direct penetration of huge amounts of harmful and dangerous substances into the Danube, imperiled its biota and resulted in pestilence of the snails and fish, while in the waste water canal of the southern industrial zone of Pence town, biota was completely destroyed.
  • This primarily affected benthic organisms, composition and abundance of communities in the localities examined. The consequences were observed at the level of organisms due to their way of life, low mobility and connection with substrate. Some of the pollutants had higher specific gravity than river water and were directly deposited into the sediment. Destruction of the aquatic habitats led to a different extent to decay of individuals, parts of populations and whole communities.
  • No significant differences in diversity and abundance of plankton were observed in localities situated along the examined Danube section comparing to previous results. This can be explained by a high water level and river water flow rate exceeding 6,000 m3/s. Accidental pollution did not influence greately plankton organisms and communities in the examined zone because of hydrological conditions, high water level and water flow rate. At the time of war operations during April and May, 1999, water level of the Danube was high and this had favourable effects on hydrobionts, especially on plankton communities, since the pollutants discharged into the river water got diluted, transformed and discomposed. On the other hand, abundant rainfalls led to an accelerated transmission of the pollution into the underground zone.
  • The absence of plankton and benthic fauna organisms in the mud of the waste waters canal of the oil-petrochemical industrial zone of Pančevo indicates a high level of toxicants and point out that its reclamation is of utmost importance.
  • With about 50,000 m3 of contaminated sediments in wastewater canal of southern industrial zone of Pancevo, depending on hydrological situation, the canal is a latent danger for aquatic ecosystems of the Danube and its flooded regions. Concerning interactions between the canal and the Danube, the canal is acting as (point) source of pollution to the Danube.
  • The results demonstrated that with a temporal and spatial shift harmful and dangerous matters were accumulated both in the river sediment and hydrobionts.
  • From the results of genotoxicity testing with Allium as test organism it is clear that both toxic and genotoxic effects of the Danube water at/in the Pančevo are resulting from the wastewater coming from the canal even five months after the chemicals leaked into it. Results obtained in the test should be considered as a warning of risk present both for human health and for water environment.
  • Definite conclusions on the action of the pollutants discharged into the Danube upon destruction of industrial complexes during the war operations on aquatic ecosystem, plankton and benthic fauna of the Danube, fish and ichthyophagous birds, as well as on macrophyte vegetation can be drawn out only upon long-term studies. Based on preliminary results and the data from the available literature indirect effects of the pollutants on organisms and their communities can be expected later via food chain. In the period to come it will be necessary to determine degree and range of harmful effects of the accidental pollution. For this purpose, new sampling localities situated downstream from the mouth of the wastewater canal should be established in a broader zone of influence. Thus, the Danube section that should be investigated in the future has to be defined after control analysis of all aquatic ecosystem components including a longer river sector than that examined from April to October 1999. A special attention should be paid to the effects of organic chlorine compounds (PCBs) and heavy metals (lead and mercury) on biota of the Danube.

 

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Acknowledgements:
Our investigations performed during and after the war were possible with the aid of Civil Defence Center, Belgrade and Association for the Danube and Sava Rivers Protection, Republic of Serbia - Belgrade.

[1] Senior research fellows at the Institute for Biological Research "Siniša Stanković", Belgrade, SCG
    Address: 29. November 142, 11000 Belgrade, SCG; e-mail: vmartino@ibiss.bg.ac.yu

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