The Oder Estuary - IOW

4
3.1 Nitrogen load
The total waterborne nitrogen influx depends on several factors like rainfall, season and
temperature. In the rainy year of 1994 the nitrogen influx was five times higher then in the years
1990, 1991, and 1992. Especially during rainy month a very high amount of nitrate is measurable
in the Oder Estuary. For example 1.700 - 1.200 tons of NO3-N entered the Estuary only from the
river Peene between January and March of 1994 (Fig. 2).
1600
1200
800
400
0
NO3-N (tons)
nitrate load runoff
runoff (Mio m3)
1 4 7 10 1 4 7 10 1 4 7 10 1 4 7 10 1 4 7 10 1 4 7 10 1 4 7 10 1 4 7 10 1 4 7 10
1990 1991 1992 1993 1994 1995 1996 1997 1998
Figure 2 Nitrate load and river runoff into the western Oder Estuary from the river Peene (1990
– 1998)
During periods of such a high runoff the nitrate concentration in the Estuary increases significantly.
Maximal concentrations of dissolved inorganic nitrogen (460 - 670 µmol/l DIN) were observed in
the upper part of the river Peene. The riverin nitrogen amount didn’t show a significant trend. In
comparison the nitrogen amount of the point sources dropped considerably though the importance
of these sources is low. In the beginning of the nineties the amount of nitrogen load from the point
sources comprised still 20 %. Modernisation as well as building of new sewage plants able to
remove nitrogen led to a decrease of the nitrogen amount to only 2 % since 1996. In spite of the
reduction of the nitrogen influx from sewage plants the whole nitrogen load of the western Oder
Estuary hardly changed (Tab. 2).
80
60
40
20
0