The aim of this study was to assess quality of the Danube sediment on five locations near Novi Sad (Futog, Strand, “Sever IV”Collector discharge site, Kovilj marsh, DTD-Kac bridge, i.e. on the Danube section 1240-1270 km) during the year 2001. Sediment samples were taken two times per quarter, and they were analyzed for the general parameters (total hydrocarbons, mineral oil, COD, BOD), inorganic pollution (heavy metals), as well as specific toxic organic substances (polycyclic aromatic hydrocarbons and pesticides). We identified the specific organic pollution (polycyclic aromatic hydrocarbons and pesticides, especially lindane), as well as inorganic toxic components, of which contents of nickel, cadmium and zinc exceeded the corresponding values found in the upstream sediment in Hungary. In some cases, values for copper, lead and chromium were also higher. In the DTD canal, during quarter IV (November-December), we also found mercury in elevated concentration. On the basis of these results it was concluded that the most endangered locations are Kovilj marsh and DTD canal-Kac bridge. The reason for this is most likely the very slow flow of water at the two locations.

Key words: Danube River, sediment quality, organic pollution, heavy metals

 

INTRODUCTION

There is no systematic monitoring of river sediment quality in Federal Republic of Yugoslavia (FRY) and thus there are no pertaining regulations.

In the course of the 1999 bombing and immediately after that the emergency monitoring of the territory of Ratno Ostrvo on the left Danube bank showed severe worsening of the quality of water and sediment¹. In order to assess the existing and potential pollution, with the aim of protecting the environment and the population along this part of the Danube River, Institute of Chemistry of the Faculty of Sciences in cooperation with the Public Enterprise for City Construction and Development carried out again measurements on five locations in the course of 2001 (Figure 1):

·         at Futog (“background sample”), 1270 km

·         at Strand, 1257 km

·         at Ratno Ostrvo, downstream of the discharge of the collector of treated oily waters from the Refinery and atmospheric sewage “Sever IV”, 1253 km

·         at Kovilj marsh, 1240 km

·         on DTD Canal, at the Kac bridge, 0+750 m

Measurements were carried out two times in a quarter: quarter I (March – April), quarter II (May – June), quarter III (August – September) and quarter IV (November – December).

  

Figure 1. Map of sampling sites

 

MATERIAL  AND METHODS

Samples were taken with the aid of the Eckman sediment sampler. Spatial samples were taken at a 10-m distance from the river bank.

The analysis encompassed general parameters of organic (total hydrocarbons, mineral oils, chemical oxygen demand – COD and biological oxygen demand – BOD) and inorganic (heavy metals) pollutants, as well as specific analyses for contents of toxic organic substances (polyaromatic hydrocarbons and pesticides).

Content of mineral oils in sediment was determined by quantitative IR spectrometry^2,3 after the 6-hour extraction with carbon tetrachloride in a Soxhlet apparatus.

COD was determined by titrimetric dichromate method, by the procedure developed in the laboratory. BOD was measured using the Lovibond BOD sensor. Contents of metal ions were determined by AAS after digestion with concentrated nitric acid. 

Quantitative GC/MS analysis was used to determine contents of pesticides and 16 polycyclic aromatic hydrocarbons (PAHs) from the EPA list of priority pollutants⁴. The following PAHs were measured: naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benz(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, dibenzo(a,h)anthracene, benzo(g,h,i)perylene and indeno(1,2,3-cd)pyrene. The following pesticides were determined: lindane, endosulphane1(alpha), endosulfane2(beta), aldrin, heptachlor epoxide isomer B, endrin, endrin aldehyde, 4,4’-ddd, 4,4’-dde, 4,4’-ddt, alpha-BHC, beta-BHC, delta-BHC.

Sediment samples were analyzed by GC/MS after the 1-hour extraction with the solvent mixture methylene chloride – n-hexane (1:1) at room temperature and purification of the extract by column chromatography on silica gel.⁵

The qualitative GC/MS SCAN analysis of the sediment gave the spectra in a wide range (35-550 atomic units), which were matched with the spectra of the commercial Wiley database. The components with the probability exceeding 70% ⁵ were included in the work.

 

RESULTS AND DISCUSSION

The presented results are expressed with respect to the mass of dry sediment.

Contents of total and mineral oils are presented in Figure 2.

 

Figure 2. Contents of total and mineral oils in sediment samples during 2001

 

Contents of mineral oils measured on all locations are similar and do not show significant time-dependent changes, the exception being the sediment from the Kac bridge location, for which the value in quarter III amounted to 49 mg/kg.

Figure 3. COD and BOD values for the investigated sediment samples

 

The COD and BOD values of the investigated samples are presented in Figure 3. The COD values for Futog were in the range from 6000 to 28200 mg O₂/kg. For the Strand location they were in the range from 5300 to 105000 mg O₂/kg, which is a consequence of the closeness of the urban zone. For the zone of discharge site of the collector “Sever IV” the values varied in a narrower range from 8600 to 36300 mg O₂/kg, the corresponding range for the Kovilj marsh being 38400-142500 mg O₂/kg, while the highest values in the range 29500-240200 mg O₂/kg were measured for the DTD canal. The COD values for the location Strand, Futog and Kovilj marsh showed a decrease during the year and a relative increase in quarter IV. To get a complete picture of the situation it should be borne in mind that in the zone of the discharge site of the collector “Sever IV” the Danube flow is fast, whereas in the zone of the DTD Canal and Kovilj marsh it is slow.

Highest BOD values were also registered for the Kovilj marsh location (19000 mg O₂/kg in quarter III) and at the Kac bridge (14000 mg O₂/kg in quarter IV). For the Futog location the BOD values were in the range of 1600-3600 mg O₂/kg and for Strand 270-5600 mg O₂/kg, the minimum being measured in quarter IV. For the location “Sever IV” this parameter varied in the range of 770-7500 mg O₂/kg, the lowest value being also measured in quarter IV. A big increase of BOD value for the Kac bridge site in quarter IV suggests the presence of “fresh” pollution by the wastewater's of the industry located on the canal.

The BOD/COD ratios for the investigated samples are presented in Figure 4. They were in the range of 0.04-0.22 for Futog, 0.03-0.74 for Strand, 0.03-0.41 for “Sever IV”, 0.04-0.50 for Kovilj marsh, and 0.05-0.17 for the sediment sample from the DTD canal.

The BOD/COD ratio in about 70% of measurements was less than 0.2 (the lowest values were measured for quarters I and IV), which suggests the presence of hard-biodegradable pollutants. However, the average annual values were quite similar, so that none of the locations could be singled out on the basis of these general indicators.

 

Figure 4. BOD/COD ratios for the investigated sediment samples

 

As far as contents of heavy metals are concerned the sediment quality parameters have been compared with the corresponding values found for the Danube sediment upstream in Hungary and, because of the lack of the appropriate regulations in our country, they were related to the values mentioned in Dutch legislation (Table 1)^6,7.

 

Table 1. Concentrations of heavy metals in sediment of the Danube River before entering FRY

and MAC values for river sediment according to Dutch legislation

 

Concentrations of heavy metals (Hg, Ni, Cd, Cr, Pb, Cu, Mn and Fe) in the investigated samples are presented in Figures 5 and 6. The values for nickel content were higher on the Futog location in quarter II, and for cadmium in all for quarters compared to those found in sediments before the Danube entrance to FRY. Contents of nickel in quarter II and cadmium in quarter IV, as well as of zinc and copper in quarter II exceeded the values allowed by Dutch regulations.

For the location Strand, higher values compared to those measured in Hungary are found for nickel in quarter I, for cadmium in all four quarters and for zinc in quarters I and III. If compared with the MAC values of Dutch legislation higher values were found for nickel and cadmium in quarter I, for cadmium in quarter IV, and for zinc in quarter III.

As for the location “Sever IV” increased contents of cadmium were found in all four quarters, of zinc in quarter III, and of lead in quarters II and III if compared with the values measured on the upstream location (Hungary). The MAC values given by Dutch legislation were exceeded for cadmium in quarters I and IV and for zinc in quarter III.

In respect of contents of heavy metals the location Kovilj marsh is most endangered. If compared with the values measured in Hungary before the Danube entrance to FRY, higher concentrations of nickel, cadmium, zinc and copper were found in quarter I. The MAC values of Dutch legislation were exceeded for nickel in all samples except for that taken in quarter III, for cadmium in all samples, for zinc in all samples except for the one taken in quarter IV and for copper in the samples taken in quarters II and IV.

On the location DTD canal-Kac bridge higher values in comparison with those measured for the Danube sediment in Hungary were found for nickel, chromium and lead in quarters I, II, and III, for zinc and copper in quarters II and IV and for cadmium in all for quarters. If compared with the MAC values given by Dutch legislation these were exceeded for mercury in quarter IV, for nickel in all samples except for the one taken in quarter III, for cadmium and zinc in all samples, and for copper in the samples taken in quarters II and IV. High contents of heavy metals can be ascribed to the industrial activities on this location. The measured values were much higher than the background values for the Danube⁷ and exceeded the MAC values of Dutch legislation in the case of cadmium, copper, zinc and mercury in quarter IV.

Figure 5. Contents of  Hg, Ni, Cd, Cr, Pb and Cu in sediment;

A* - MAC value for river sediment according to Dutch legislation

 

Figure 6. Contents of Fe and Mn in sediment;  A* -  MAC

value for river sediment according to Dutch legislation

 

Contents of toxic organic componenets (PAHs and pesticides) in sediment measured upstream in Hungary before the entrance of the Danube to FRY and the MAC values given by Dutch legislation  are compared in Table 2^6,7.

 

Table 2. Contents of particular toxic components in sediment before

the Danube entrance to FRY and MAC values for toxic components in river sediment according to Dutch legislation

 

Contents of PAHs in the investigated samples are presented in Table 3. If compared with the MAC values given by Dutch legislation chrysene content for the Futog location was higher in quarters I and II, whereas the value was significantly lower in quarter IV.

For the location Strand PAH contents are higher compared to the values observed upstream at the Danube entrance to FRY, whereas the values for phenanthrene in quarter I, benz(a)anthracene in quarters I, II and III and benzo(a)pyrene in quarters I and III are higher than the MAC values given by Dutch legislation. However, contents of PAHs were significantly lowered in quarter IV.

As far as the discharge site of collector “Sever IV” is concerned, PAHs contents were the lowest, which is probably a consequence of rapid water flow in this section of the Danube, carrying downstream the pollutants. These contents were the lowest in quarter IV. If compared with the values measured during the bombing in 1999 and immediately after that (123,460 in May, 1946 in June and 754 µg/kg in August of 1999)¹ PAHs content on this location was significantly lower.

The Kovilj marsh location appeared to be most endangered in respect of the chemical quality of sediment. If compared with the corresponding values in Hungary before the Danube entrance to Yugoslavia PAHs contents are higher in quarter I. As for the comparison with the norms of Dutch legislation higher values were found for phenanthrene, fluoranthene, benz(a)anthracene, chrysene, and benzo(a)pyrene in the same quarter. After that significant decrease in the values was observed to quarter III, which can be ascribed to the pollutant transport by the river flow.

The PAHs contents for the location DTD-Kac bridge were at a level of about 400 ppb in quarter I, afterwards showed a decline, so that the lowest values were measured in quarter IV.

 On the basis of the above findings it is evident that highest contents were found for pyrene, chrysene, fluoranthene, phenanthrene, benzo(a)pyrene, benzo(a)anthracene, and benzo(b)fluoranthene.

The mean annual contents of the sum of 16 PAHs presented in Figure 7 show that the highest values were obtained for the Kovilj marsh location and then for Strand and Futog, whereas the values measured for the location “Sever IV” and DTD-Kac bridge were below 200 µg/kg. The lower values found for the location that are closest to the industry located on the Danube can be explained in terms of rapid river flow on these locations.

Figure 7. Mean annual contents of  PAH sums in sediment samples