Who done it? Searching for clues with sediments

The sediments near Horn Richterswil - today a recreation and bathing resort on Lake Zurich - are contaminated with toxic metals, particularly mercury. On behalf of the Canton of Zurich, researchers have used sediment cores to reconstruct when the pollutants entered the lake. In this way, they could help clarify the origin of the contaminants. The Contaminated Sites Ordinance obliges all cantons to check polluted sites for contamination and to decontaminate them where necessary. In 2013, the Canton of Zurich's Cantonal Office for Waste, Water, Energy and Air (AWEL) therefore commissioned the aquatic research institute Eawag and several engineering firms to examine the lake bed near Horn Richterswil for contamination. The adjacent area of land had been used as an industrial site for over 100 years before it became the property of the Canton of Zurich in 1976 and the Commune of Richterswil in 2020. It has been a public recreation and bathing resort since the mid-1980s.