Promotion work for Scientific Degree of the Doctor of Geographic Sciences
(Dr.sc.geogr.)
Elga Apsite
The flow of organic matter in surface waters of Latvia and Sweden under
variable antropogenic impact
University of Latvia. Riga. 1999
CONCLUSIONS
The analysis of water quality parameters characterising the concentration of organic
mallei (chemical oxygen demand and the colour of water) in rivers of Latvia and
Sweden showed that in order to study natural and antropogenic processes in the
environment applying the monitoring data, it is necessary to ensure high quality
methods both in water sampling and the chemical analysis. We came to the conclusion
that it is necessary to improve the Latvian monitoring system of surface waters which
includes the methods of water samplings. chemical analysis, as well as, the choice of
water sampling sites and optimum water quality parameters which characterise the
concentration of organic matter.
The analysis of correlation and seasonal variation of water quality parameters
characterising the concentration of organic matter (chemical oxygen demand and the
colour of water) in rivers of Latvia and Sweden has showed similar results. The results
of correlation have showed strong positive and nonlinear correlation between organic
matter and water discharge. We could conclude that maximum level in the concentration
of organic matter is reached in spring and in autumn but minimal level could be
observed in river baseflow in summer or winter season. Such correlation and seasonal
variation of organic matter is determined by dynamical changes of dominating water
flow and humic substances in the river basin and the changes in the concentration of
substances related with river discharge.
The analysis of long-term variation of water quality parameters characterising the
concentration of organic matter indicates that there are considerable differences of
temporal trends in the concentration of organic matter. In general, the temporal trend of
chemical oxygen demand and the colour of water of rivers in Latvia presents a
downward trend (1977-1997) but in Sweden it shows an upward trend (1971-1994). The
natural and antropogenic factors in the river basins under investigation have affected the
existing character of trends.
The increase of the ratio between organic nitrogen and carbon in the rivers of Sweden is
affected by landuse, especially the area of arable lands and the percentage of lakes. The
research has revealed that wet deposition of nitrogen serves a subordinate role in the
increase of nitrogen in the rivers.
Having done the study ofhumification process in different landuse soils in Vidzemes
highland (in Latvia) we can conclude that the highest degree of humification is typical
of agricultural soils rather than of forest soils. It depends on the quality of raw material
of organic matter, as well as, on the complex of abiotic and biotic factors and
aniropogenic factors.
The elemental, functional, molecular mass, acid-base and spectral properties of humic
substances taken from surface waters and sediments of lakes in Latvia has been
determined to analyse the origin and properties of humic substances. The research has
revealed that humic substances isolated from oligotrophic and dystrophic lakes are of
similar nature as to their structure and properties, and they exhibit the importance of
biological transformation process of lakes in humic substances formation.
Publikācijas zinātniskajos žurnālos:
Apsite, E., Kļaviņš, M. (1997) Sources, flows and sinks of organic matter in aquatic
environments. Proceedings of the Latvian Academy of Sciences, B 3/4:51, 133-142.
Kļaviņš, M., Apsite, E., Parele, E. (1997) Humic substances in surface waters of Latvia.
Proceedings ofthe Latvian Academy ofSciences, B 3/4:51, 143-152.
Klaviņš, M., Apsite, E. (1997) Sedimentary humic substances from lakes in Latvia.
Environment Intemational, 23, 783-790.
Kļaviņš, M., Apsite, E., Cimdiņš, P. (1997) Aquatic humic substances from Latvia. Verh.
Imemat. Verein. Limnol., 26, 339-342.
Apsite, E., Kļaviņš, M. (1998) Assessment of the changes of COD and color in rivers of
Latvia during the last twenty years. Environment Intemational, 24,637-643.
Apsite, E,, Grimvall, A., Jacks, G. (1999) Impact of atmospheric deposition of nitrogen
and landuse on the spatial variability of the ratio of nitrogen to carbon in the Swedish
rivers (sagatavots publicēšanai)
Konferenču tēzes:
Apsīte, E., Kļaviņš, M. (1996) Humusvielu koncentrāciju izmaiņas Latvijas upēs pēdējo
divdesmit gadu laikā. Latvijas Ģeogrāfu kongress '96 tēzes un programma. LU, Riga, 48.50. lpp.
Apsite, E., Kļavinš, M. (1997) Analysis ofthe concentration changes of organic matler in
Latvian rivers during the last twenty years. 6"' Nordic Symposium on Humic Substances:
Humic Substances as an Environmental Factor. Hameenlinna, pp. 58.
Apsīte, E., Kļaviņš, M., Kokorīte, I. (1997) Analysis of water quality changes in the rivers
of Latvia during the last twenty years. International conference of Ph.D. students. Section
proceeding of natural sciences. University of Miskolc, Hungary, pp. 1-8.
Apsīte, E., Kokorīte, I. (1997) Latvijas upju bioķīmisko komponentu trendu analīze un
sezonālās izmaiņas. LU 56.zinātniskā konferences tēzes: Zeme, daba, cilvēks. LU, Riga,
4.-5. lpp.
Apsīte, E., Nikodemus, 0. (1999) Humifikācijas process dažāda zemes lietojuma augsnēs
Vidzemes augstienē. LU 57. konferences tēzes: Zeme, daba, cilvēks. LU, Rīga, 8. lpp.
Apsīte, E., Grimvals, A., Jaks, G. (1999) Atmosfēras slāpekļa nosēdumu un zemes
lietojuma ietekme uz slāpekļa un oglekļa attiecības izmaiņām Zviedrijas upēs. LU 57.
konferences tēzes: Zeme, daba, cilvēks. LU, Rīga, 7. lpp.