Heavy Metal Pollution

Introduction Release of toxic metal ions into water Lead Pb2+, mercury Hg2+, cadmium Cd2+ Ions Called Heavy Metals due to high RAM Cumulative poisons Concentrations build up in body on continuous exposure [over time]

Sources (i) Industrial effluent (ii) Potential pollution from batteries of various kinds if not recycled (iii) Pb2+ from the water pipes of old houses - especially if water is acid

Case Study Mercury metal Poisonous inhaled into lungs Not poisonous if swallowed Passes out in a few days Inorganic mercury salts dangerous at high concentrations. E.g. HgCl2, Hg(NO3)2 etc. Organic at low levels Damage kidneys and intestine Makes one “poco loco”. “Mad as a Hatter”

Minimata Bay Japan Late 1950’s Industrial waste discharged into bay Hg salts got into food chain High concentrations built up in fish People ate a lot of fish Caused birth defects and death Called Minimata Disease

Removal Usually removed before discharge (i) Removed by precipitation Pb2+ + 2 Cl- = PbCl2(s) (ii) Ion exchange

E U Limits For levels of nitrate, phosphate and specific metal ions [2 examples] Substance Maximum admissible Concentration Nitrates 50 mg / L Phosphates 2.2 mg / L Lead Mercury 1 µg / L