… matter Nickel is emitted by power plants or industrial processes. Source: jzehnder / fotolia.com Nickel belongs to the heavy metals and usually occurs bound to … matter - annual mean values 2007 - 2021 Source: Umweltbundesamt II 4.2 mit Daten der Messnetze der Länder und des Bundes Nickel in particulate matter - Annual tabulation Here the …