THE NEVA PROJECT: SITE 4
Ecology of Lake Ladoga and the Neva River
The water economy of St. Petersburg is greatly dependent on the ecology of Lake Ladoga, because the Neva River, which flows out of Ladoga, is the city’s major source of potable water. The pollution load of Lake Ladoga, via the Neva, also has a considerable influence on water quality in the Gulf of Finland, on the Baltic sea. There are about 500 factories situated in the lake area which discharge their effluents into Ladoga. The daily waste water discharge into the lake is about 3.8 million m3, 660,000 m3 of which are poorly treated or untreated, containing 1100 t of pollutants daily or 400,000 tons per year.
View of Lake
Ladoga
Eutrophication is a critical problem in Lake Ladoga and is likely to bring about fundamental changes in the ecosystem of the lake. The lake was formerly oligotrophic or mesotrophic, meaning it had relatively few nutrients and, as a result, the clear, pure water characteristic of fairly young lakes. The problem in Lake Ladoga began in the mid-1960s, when phosphorus concentrations began to rise. In the 1980s the phosphorus load was estimated to be 6600 tons per year and it has been on the increase since then. The main sources of phosphorus along the lake are the pulp and paper industry, chemical enterprises, non-ferrous metallurgy, agriculture (especially large-scale pig farms) and municipal effluent treatment facilities that do not remove nutrients.
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Water
quality of Neva River at Shlisselburg, 1999
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| Water quality parameter | Unit | Value |
| Dissolved
oxygen |
mg/l | 10.1 |
| BOD5 | mg/l | 1.6 |
| suspended solids | mg/l | 1.2 |
| Nitrite nitrogen | mg/l | 0.007 |
| Total nitrogen | mg/l | 0.69 |
| Total phosphorus | mg/l | 0.024 |
| Volatile phenols | mg/l | 0.005 |
| Oil products | mg/l | 0.03 |
| Copper | micro-g/l | 2.8 |
| Lead | micro-g/l | 4.0 |
| Manganese | micro-g/l | 4.0 |
| Cadmium | micro-g/l | 0.4 |
| Mercury | micro-g/l | 0.2 |
| DDT | micro-g/l | 0.03 |
The average concentration of total phosphorus in the lake during the vegetation period ranges from 0.011 to 0.038 mg/l. The maximum phosphorus load level which would allow the lake to return to its natural oligotrophic or mesotrophic state in 10-12 years is estimated to be 3600-4000 tons/year. But over the past decade, the average load has been much higher (approximately 6650 tons/year, about 2450 of which discharged into Neva and then to the Gulf of Finland). The average concentration of total nitrogen in the lake ranges from 0.58 to 0.72 mg/l during the vegetation period.
Because of the deterioration of water quality in Lake Ladoga, the Neva is classified on the Water Pollution Index as a level III (moderately polluted) river, even at its source in Shlisselburg, though it has improved during the last two decades and is now close to being at level II (pure). Average concentrations of main pollutants in the water at the Neva’s source in Shlisselburg are given in the table (left).
QUESTIONS FOR OUR READERS: What historical impact might the old and new Ladoga Canals have had on the ecology of Lake Ladoga? Did meieval trade also bring alien species to this area? Please feel free to contact us.