Danube Delta Biosphere Reserve - ten years of toxic substances investigations

Abstract

The main propose of this study was to assess the levels of some toxic substances in expressing the pollution degree of the aquatic ecosystems. A ten-yearinvestigation of 4heavy metals(such as As, Pb, Ni, Cr) in surface water and sediments samples from a representative aquatic complex in the Danube Delta Biosphere Reserve (Matita-Merhei) was accomplished. The results (expressed in µg heavy metal/L for water samples and mg heavy metal/kg dry sediment samples) were annual mean concentrations (2006-2015) of heavy metals and were assessed according tothe European Water Framework Directive 2000/60/CE. The research conducted over the past decade has shown that the accumulation of the heavy metals in the Danube Delta Biosphere Reserve is, generally, determined by natural factors (natural frame, climate, drainage system), but also by the varied activities occurred in the border area. The analysis of the obtained results revealed that the quality standard was exceeded in the case of bottom sediment samples for Pb, Ni and Cr, with a general ascending trend as follows: As<Pb<Ni<Cr. As a general remark, the trend analysis on the set of ten-year data showed a decreasing tendency of toxic substance concentrations in the last years.