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- Title
Long-term Changes in Environmental Variables of Traunsee, an Oligotrophic Austrian Lake Impacted by the Salt Industry, and Two Reference Sites, Hallstättersee and Attersee.
- Authors
Jagsch, A.; Gassner, H.; Dokulil, M. T.
- Abstract
Morphometric, hydrological and basic physico-chemical characteristics of three deep Alpine lakes, Traunsee, Hallstättersee and Attersee as well as their long-term bahaviour are presented. The deep Alpine lakes Hallstättersee and Traunsee have been influenced by salt mining and the traditional salt industry for over 100 years. Waste products from these activities, entering the lakes, have mainly affected the chemistry of these water bodies, especially by substantially increasing the chloride concentrations up to 170 mg L-1. As a consequence of the increased density, mixing conditions of the lakes were altered. The resulting incomplete mixing led to oxygen depletion in deeper layers. In addition, increased nutrient load from the catchment rised the trophic level in the 70s and 80s of the last century in turn, affecting the oxygen content in the hypolimnion. Finally a situation developed where the risk became high for these lakes to become meromictic induced by human activity. In fact, Hallstättersee became facultatively meromictic. This process was interrupted by increased chloride input of more than 30 mg L-1 due to accidental wash out from an upstream salt mine rendering Hallstättersee homogenous in 1978 to 1980 resulting in complete over-turn. Conditions substantially improved in both lakes after mining practices were altered and restoration measures against eutrophication were initiated. Chloride and phosphorus concentrations declined, while oxygen conditions substantially improved in the following years. Conditions in Traunsee substantially improved and chloride levels near the sediment decreased to less than 140 mg L-1. The third lake considered here, Attersee, always remained in a near-natural state although some signs of increased nutrient levels became visible in the late 1970s. Chloride concentrations of around 3 mg L-1 in this lake can be considered as background levels. Attersee can now serve as a reference site for deep Alpine lakes because of its ultra-oligotrophic and pristine nature.
- Subjects
SALT mining; EUTROPHICATION; LAKE restoration; LIMNOLOGY; WASTE spills; SEWAGE disposal in rivers, lakes, etc.
- Publication
Water, Air & Soil Pollution: Focus, 2002, Vol 2, Issue 4, p9
- ISSN
1567-7230
- Publication type
Article
- DOI
10.1023/A:1020301302080