Publikationsdatum:
2006-06-12
Beschreibung:
Nitrate input to a river is largely controlled by land use in its catchment. We compared the information carried by the isotopic signatures of nitrate in 12 Baltic rivers, in relation to the vegetation cover of their catchments. We found isotope values in nitrate ranging from −2 to 14 for δ15N and 8 to 25 per mil for δ18O. Seasonal signals were evident in all rivers. The annual variability of riverine isotope signatures is presented in detail for one Nordic, the Kemijoki, and two southern rivers, Vistula and Oder. Nordic rivers with relatively pristine vegetation in its catchments show not only low δ15N values and high δ18O-NO3− but also lower annual variability than rivers draining densely populated land. Seasonal signals could be found in all of the rivers. We used load weighted nitrate isotope data and data from the three major sources (farmland/sewage, atmospheric deposition and from runoff of pristine soils) to theoretically estimate the shares of nitrate from these sources. The results agree well with same estimates derived from a Global Land Cover data base. The comparison with an emission model (EM) reveals good agreements for intensively used catchments and rather bad ones for pristine catchments. Advantages and limitations of the tested model types are discussed.
Print ISSN:
1810-6277
Digitale ISSN:
1810-6285
Thema:
Biologie
,
Geologie und Paläontologie