Earth is the third planet from the Sun and the only object in the Universe known to harbor life. According to radiometric dating and other sources of evidence, Earth formed over 4.5 billion years ago. Earth's gravity interacts with other objects in space, especially the Sun and the Moon, Earth's only natural satellite. Earth revolves around the Sun in 365.26 days, a period known as an Earth year. During this time, Earth rotates about its axis about 366.26 times.
Human activities have strongly modified the biogeochemical cycles of metallic trace elements (MTEs) increasing their fluxes towards and between surface environments. New isotope data has fostered better models of MTE sources, transfer and reactivities in dynamic and multi-sources systems, as required for targeting emission controlled strategies to combat origins and consequences of metal contamination.