Chapter_7_Water_Pollution_

Chapter_7_Water_Pollution_ - 1 Chapter 7 Water Pollution...

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Water Pollution Environmental Chemistry ENVS 4101 Dr Portier 1 1 Chapter 7
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7.1 Nature and Types of Water Pollutants • See list in Table 7.1 Markers of water pollution that show presence of pollution sources • Herbicides indicate agricultural runoff • Fecal coliform bacteria indicate sewage sources • Pharmaceutical metabolites in domestic wastewater Biomarkers of water pollution are organisms that indicate pollution • May accumulate pollutants that appear in analysis • May show effects from pollutant exposure • Fish lipid tissue accumulates persistent organic pollutants • Osprey at top of aquatic food web is a good biomarker 2
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3 7.2 Elemental Pollutants Trace elements (harmful at a few parts per million or less) • See list in Table 7.2 Heavy metals are among most harmful • Cadmium • Mercury • Lead • Most are sulfur seekers Metalloids may be significant water pollutants • Most important is arsenic • Selenium and antimony can also be harmful
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4 7.3 Heavy Metals Cadmium • Highly toxic • Chemically very similar to zinc From mining and industrial wastes (especially metal plating Lead • Widely used and distributed in the past • Plumbing (lead pipe, solder) used to be a major source • Uses (such as in gasoline) have been greatly curtailed Mercury • Highly toxic • Minimata Bay incident • Mobilized by bacterial methylation—HgCH3+, Hg(CH3) 2
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5 7.4 Metalloids Arsenic is the most significant • From coal combustion • Occurs with phosphate minerals • Byproduct of copper, gold, lead refining • Natural occurrence in some groundwaters • Formerly in pesticides: Pb3(AsO4)2, Na3AsO3, Cu3(AsO3)2 Bangladesh tube well poisonings may have affected millions
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7.5 Organically Bound Metals and Metalloids Have metal (metalloid) bonded to carbon • Alkyl groups such as ethyl in Pb(C2H5)4 π (pi) electron donors such as ethylene, C2H4 • Carbonyls with bound CO Tetraethyllead, C2H4, in gasoline introduced large quantities of lead into the environment until it was banned Methylation of mercury by anoxic bacteria mobilized otherwise insoluble inorganic mercury Organotin compounds were widely used as marine biocides in ship and boat paints • Tributyltin chloride commonly used industrial biocide • Endocrine disruption in shellfish and oysters • Uses now being phased out 6
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7 7.6 Inorganic Species Cyanide (HCN, CN - ) • Extremely toxic • Industrial uses including metal cleaning, electroplating • Produced by coke ovens • Water pollution and fish kills from mineral processing • Concern for terrorist attacks on water supplies Ammonia • Generally as NH4+, NH3 at high pH • Added to drinking water for residual disinfection from chlorination Free carbon dioxide, CO2 In water from decay of organic matter, geochemical sources Makes water corrosive, harmful to aquatic life
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8 Hydrogen sulfide, H2S From industrial sources, decay of organosulfur compounds, geochemical sources Foul odor, very detrimental to water quality, very toxic
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This note was uploaded on 10/11/2011 for the course ENVS 4101 taught by Professor Portier during the Spring '10 term at LSU.

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Chapter_7_Water_Pollution_ - 1 Chapter 7 Water Pollution...

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