Contamination of Lake Neusiedl with anthropogenic trace substances: considerations on their origin and behaviour

In this paper, we first present the contamination of Lake Neusiedl with anthropogenic trace substances regulated at national or EU level. Second, we identify main emission pathways for selected substances into the River Wulka and Lake Neusiedl and identify the potential environmental behaviour of trace substances in the aquatic system. Even if a comprehensive monitoring of all regulated substances in the lake is at present still missing, we can assume the compliance with environmental quality standards for most of them based on measurements carried out in the River Wulka and from biota-monitoring in the lake. For some substances quality criteria are not or probably not met, for others a final diagnosis is currently not possible due to analytical constraints. Depending on the examined substance, effluents from waste water treatment plants, agricultural erosion or atmospheric deposition on the lake surface may be the dominant pathway of contamination into the River Wulka and Lake Neusiedl. Besides specific considerations for individual substances, taking into account the enormous number of anthropogenic trace substances that are released into the environment, Lake Neusiedl must be regarded as especially vulnerable to this kind of contamination. The high vulnerability mainly derives from the lake acting as a substance-sink. Persistent chemicals which enter the lake may concentrate in the water of the lake or may be stored in the sediments of the reed belt, from where they might be mobilized later on. Even if many of the highly persistent chemicals are removed from the lake water through degradation or conversion to metabolites, little is known about the end products of this conversion and they cannot be monitored completely because of their high number. As a basis for the development of strategies for a long-term and efficient management of the lake, a regular monitoring of trace substances in lake and reed belt should be reinforced considerably to detect any undesirable developments as early as possible.