In 1986 a contract was signed concerning the scientific-technical cooperation of the Russian Federation (former USSR) and the Federal Republic of Germany. Based on this contract, the Oka-Elbe project was launched 1992 in Nishni Novgorod. This paper presents the results of heavy metal investigations (270 samples) in the Oka River drainage area.
Table 1 shows some general data of the Oka River, the second largest tributary of the Volga River, draining larger parts of the Central Russian Platform. The Oka catchment area is one of the regions with the highest industrialization, in particular mechanical engineering, metal works, petrochemistry, chemical and weapon industries.
Fine grained sediments are indicators for pollution with heavy metals and other contaminants in aquatic environments. Accordingly, the sediment investigations in the Oka area were designed to evaluate the present situation of heavy metal pollution and, furthermore, to estimate their hazard potentials with respect to practicable sanitation methods.
The concentrations of the elements Hg, Cd, Pb, Cu, Cr, Ni, Co, Fe and Mn were determined by AAS in the sediment fraction < 20 µm after dissolution with aqua regia (Table 2).
The most important results for the Oka drainage area can be summarized as follows:
1. No sediment pollution occurs in respect to the elements nickel and cobalt. The average concentrations are even lower than the geochemical background concentrations ("average shale" after Turekian & Wedepohl, 1961).
2. The average concentration of mercury is also lower than its geochemical background. A strong sediment pollution with respect to mercury, however, occurs in the Klyazma River, the largest tributary of the Oka River, draining the northern part of the Moscow region.
3. The concentrations of lead, chromium, copper, and zinc are about 40% higher than the theoretical background. In some areas, moderate to strong pollution was detected at:
- the Oka River downstream from the city of Orel
- the Upa River downstream from the city of Tula
- the Moskva River downstream from the city of Moscow
-the Klyasma River downstream from Moscow and downstream from Vladimir
4. The highest pollution of the sediments is with cadmium. The average concentration of cadmium is about 4 times higher than the theoretical background concentration. Strong and extremely strong pollution, i.e. an accumulation factor up to 32, occurs at all stations listed under point 3.
5. Sediments of the drinking water reservoirs of Moscow, situated in the Northwest of the city at the Moskva and its tributaries, do not show any contamination with heavy metals.
Due to the excellent logistic support and financial backing by the German (BMBF) and the Russian authorities the cooperation has been very fruitful and encouraging.
Table 1: General data of the Oka catchment area.
Length of the river in km 1500
Catchment area in km2 245,000
Inhabitants in the catchment area 21 Mio.
Average discharge in m3/s 1270
Table 2: Statistic parameters of the Oka River sediment samples, fraction < 20 µm. Concentrations in mg/kg. Sampling campaigns: Sept. 1992; June/July 1993; June/July 1994.
n=52 hg Cd Pb Cr Cu Ni Zn Co
Oka average value 0.16 1.1 27 91 52 55 137 16
median 0.13 1.4 25 80 43 50 113 16
maximum 0.5 14.6 68 707 359 229 555 21
minimum 0.1 0.1 9 31 13 26 51 9
Background average shale 0.4 0.3 20 90 45 68 95 19
Fig. 1: Heavy metal concentrations in sediments of the Oka River and some tributaries.