Recent depositional history of noble and critical elements in sediments from a wastewater-impacted bay (Vidy Bay, Lake Geneva, Switzerland)

Opposing trends in environmental pollution have been observed in recent years, with a growing awareness of the need to reduce emissions to the environment being accompanied by a concomitant increase in the use of polluting substances, which can potentially end up in the environment and harm humans and ecosystems. In order to assess the temporal evolution of loadings of seldom monitored trace elements, including noble metals and some technology critical elements, we analyzed a sediment core taken from the Bay of Vidy (Lake Geneva), impacted by the effluent of an urban wastewater treatment plant (WWTP). The temporal profiles of the chemical elements show essentially two patterns linked to the implementation of the WWTP, with some elements increasing sharply (e.g. Au, In, Ba, Sb, Sn, platinum group elements), while others (e.g. Ga, Ge, rare earth elements) show decreasing concentrations due to dilution by additional effluent particle loads. The origin of the elements showing a marked increase is attributed to local sources (photographic industry and municipal incinerator). There is (still?) no evidence in the sedimentary record of concentration increases linked to the growing use of technologically critical elements by industry.