which applies to the group of metals and metalloids with atomic density greater than 4 g/cm or 5 times or more, greater than water
(Huton and Symon, 1986; Battarbee et al., 1988; Nriagu
and Pacyna 1988; Nriagu, 1989; Garbarino et al., 1995,
Hawkes, 1997). However, being a heavy metal has little
to do with density but concerns chemical properties.