Toxic metals
Toxic Metals
TAN.OCUs MAN GOUR ( n (V(V)(V) D) E un(V (v (V)(vI ML) |5253 57273747m|7|7 NNER TRANSTION CROUPS OhMM GiIn Dy He Er Tm ni L TU||{。|盒a■||w||L Elements shown in bold outline are known to be essential for human metabolism About 1/ 3 of all known enzymes require the presence of a metal ion for them to exhibit biochemical activity
• Elements shown in bold outline are known to be essential for human metabolism. • About 1/3 of all known enzymes require the presence of a metal ion for them to exhibit biochemical activity
oxic metals Some metals are essential for the normal development and well-being of humans and other creatures They include Na, K ca, Mg, cu, cr, and zn Other metals are toxic even when present in an organism at very low concentrations. Examples: Antimony, Arsenic, Barium, Beryllium, Cadmium, Lead, Mercury, Nickel, Selenium, and thallium (Arsenic and selenium are not metals but are often listed with them) The toxic metals can cause brain damage, kidney and liver disorders and bone damage
Toxic metals • Some metals are essential for the normal development and well-being of humans and other creatures. – They include Na, K, Ca, Mg, Cu, Cr, and Zn. • Other metals are toxic even when present in an organism at very low concentrations. – Examples: Antimony, Arsenic, Barium, Beryllium, Cadmium, Lead, Mercury, Nickel, Selenium, and thallium – (Arsenic and selenium are not metals but are often listed with them). – The toxic metals can cause brain damage, kidney and liver disorders, and bone damage
Maximum permissible levels for metals in drinking water(USEPA standards Metal Max Level Metal Max Level (ppb) (ppb) Antimony(Sb) 6 Lead 50 Arsenic 50 Mercury Barium 2000 Nickel 100 Beryllium 4 Selenium 50 Cadmium 5 Thallium 2 Chromium 100
Maximum permissible levels for metals in drinking water (USEPA standards) Metal Max. Level (ppb) Metal Max. Level (ppb) Antimony (Sb) 6 Lead 50 Arsenic 50 Mercury 2 Barium 2000 Nickel 100 Beryllium 4 Selenium 50 Cadmium 5 Thallium 2 Chromium 100
Biogeochemical cycle of metal species All metals cycle naturally through the environment Sources: weathering of rocks Transportation: uptake and processing by plants and microorganisms. Plants living in soils rich in metal species have evolved protective mechanisms These plants can be used in remediation of soils contaminated with metals Human intervention have greatly perturbed the natural biological cycles of the metals Mining and metallurgy Coal burning Metals can not be broken down into simpler, less toxic forms. As a result, they persist in the environment and bioaccumulate through food chain
Biogeochemical cycle of metal species • All metals cycle naturally through the environment. • Sources: weathering of rocks • Transportation: uptake and processing by plants and microorganisms. – Plants living in soils rich in metal species have evolved protective mechanisms. – These plants can be used in remediation of soils contaminated with metals. • Human intervention have greatly perturbed the natural biological cycles of the metals. – Mining and metallurgy – Coal burning • Metals can not be broken down into simpler, less toxic forms. As a result, they persist in the environment and bioaccumulate through food chain