Annual average river nitrate concentration (mg/l NO3-N) in 2008, averaged by river basin district
For countries that report only total oxidised nitrogen (TON = NO3 NO2) and not nitrate alone, the map shows the TON-N data, taken as an estimate for NO3. In most rivers TON-N will be almost the same as NO3-N. Note that these data are not yet quality-checked. Certain values and colour codes might therefore be incorrect.