『Abstract
Pollution of inland waters by agricultural land use is a concern
in many areas of the world, and especially in arid regions, where
water resources are inherently scarce. This study used physical
and chemical water quality and stable nitrogen isotope (δ15N)
measurements from zooplankton to examine nitrogen (N) sources
and concentrations in four small lakes of Khorezm, Uzbekistan,
an arid, highly agricultural region, which is part of the environmentally-impacted
Aral Sea Basin. During the 2-year study period, ammonium concentrations
were the highest dissolved inorganic N species in all lakes, with
a maximum of 3.00 mg N l-1 and an average concentration
of 0.62 mg N l-1. Nitrate levels were low, with a maximum
concentration of 0.46 mg N l-1 and an average of 0.05
mg N l-1 for all four lakes. The limited zooplankton
δ15N values did not correlate with the high loads of
synthetic fertilizer applied to local croplands during summer
months. These results suggest that the N cycles in these lakes
may be more influenced by regional dynamics than agricultural
activity in the immediate surroundings. The Amu-Darya River, which
provides the main source of irrigation water to the region, was
identified as a possible source of the primary N input to the
lakes.
Keywords: Nitrogen cycling; Water quality; Stable nitrogen isotopes;
Agricultural runoff; Anthropogenic impacts; Lakes』
Abbreviations
Introduction
Study area
Methods
Results
Discussion
Summary and conclusions
Acknowledgments
Appendix
References