Water Pollution An Introduction Outline of Topics The

Water Pollution: An Introduction

Outline of Topics • The Hydrosphere – Water Reservoirs – Water Usage in the US – The Hydrologic Cycle • Composition of the Hydrosphere – The Dissolution Process – Composition of Seawater – Composition of Rivers • Water Pollution – – Changes in River Composition Westhampton Lake Water Pollution Overview: Sources, Pollutants US Water Quality

The Hydrosphere • Lecture Question – List the major water reservoirs on Earth – ie, the components of the hydrosphere – in order of volume (largest to smallest).

US Freshwater Usage Sources of freshwater • approx 75% surface water • approx 25% ground water Uses of freshwater • agriculture (41%) • hydro power (39%) • drinking/washing/etc (12%) • almost half (48%) supplied by ground water • industrial/mining (8%) Largest Consumption • agriculture, by far (85%)

The Hydrologic Cycle • Questions – What is the hydrologic cycle? • The hydrologic cycle is the movement of water between its reservoirs, on either a local or global scale. – What are the processes by which water circulates between its reservoirs? • • Precipitation Condensation Evaporation Transpiration – Uptake from soil by plants, release as vapor from stomata • Overland flow – Surface runoff – Channel flow • Groundwater flow – Baseflow recharges surface water (rivers, lakes, etc) • Infiltration into the soil – Mechanism of groundwater recharge

The Hydrologic Cycle

Global Water Balance and Circulation Volumes: km 3 Fluxes: km 3/yr

Global Water Balance and Circulation • Globally: a giant distillation – There is a net global movement of water • ocean atmosphere land oceans – This process concentrates solutes in oceans that were picked during flow over/through the land • What happens to water that falls (as precipitation) on the land? – Can be intercepted by foliage • Most of this evaporates back into the air – Can run off over land into a nearby river/lake – Can penetrate into the ground (infiltration/recharge) • Soil water: some of this is taken up by roots and transpired back into the air; some is evaporated (evapotranspiration) • Ground water: flows underground towards nearby rivers/lakes (base flow) – Runoff vs infiltration/recharge • Depends on the vegetation/landscape and the rate of precipitation

Fate of Atmospheric Precipitation

Dissolution of Solids • Question – What is a solution? How is it formed? – Electrolytes vs nonelectrolytes – Dissolution of solids • Molecular compounds • Ionic compounds

Composition of the Hydrosphere • Lecture Question – What are the most concentrated solutes in the hydrosphere? – Cations: Na+, K+, Ca 2+, Mg 2+ – Anions: Cl-, SO 42 -, H 2 CO 3/HCO 3 -/CO 32– Neutral: Si(OH)4

Dissolved Solutes in Seawater • Proportions are by mass fraction • Proportions remain fairly constant, even as salinity changes • Ranges of salinity: 33 – 37 g/kg

Dissolved Solutes in Seawater

Dissolved Solutes in Rivers Values from 1980

Dissolved Solutes in Rivers • Concs can be quite variable. • 98% of all rivers have Ca 2+ and HCO 3 - as the principal ions.

Change in Average River Water Composition (Major Ions) • Increases in concentrations of major ions in freshwater due to pollution: – – – – • Ca: +9% Mg: +8% Na: +28% K: +7% Cl: +30% SO 4: +50% (approx) HCO 3: +2% Why? – Irrigation • Mimics “distillation” process (which causes oceans to be salty) on a local scale • Water – often from underground – with dissolved solutes is applied to crops. Some evaporates, concentrating the salts in the soil. These (especially the more mobile ions, such as Na+ and Cl-) make their way back into local rivers. – Atmospheric acid deposition • SO 2 emissions will be oxidized in the atmosphere and deposit as sulfate PM.

Water Pollution • What is wrong with Westhampton Lake? – Pathogens • High counts of fecal coliform (human, animal) – Cultural eutrophication • Due to nutrient pollution – Nitrogen: nitrate, ammonium – Phosphorus: phosphate • Harmful effects – – – Oxygen depletion Siltation Decreased light penetration Increased mobility of toxic metals Increased production of methane, hydrogen sulfide, other noxious gases

Classification of Water Pollution • Biological pollution – Pathogens (poor sanitation) – Others: invasive species, eutrophication, etc • Physical pollution – Thermal pollution (water used as coolant) – Siltation (increased TSS), eg due to increased erosion • Chemical pollution – Change in chemical composition and toxicity

Water Pollution Overview • Worst Water Pollution Problems – Pathogens • Due to poor sanitation • Can be a serious problem in developing countries • WMO estimate: 3. 5 million die a year from water-born disease, mostly children under 2 years old – Nutrient pollution • Causes cultural eutrophication, algae blooms, oxygen depletion – High BOD waste • Causes oxygen depletion – Toxic metals • Sometimes called “heavy” metals • Lead, mercury, arsenic are the worst offenders – Toxic organics • Pesticides, petroleum by-products, solvents, industrial waste, etc

Major Activities that Pollute the Hydrosphere • Industrial discharges – eg, paper and pulp mills, chemical manufacturers, steel plants, textile manufacturers, food processing plants • Sewage discharges – Discharges of treated sewage from treatment plants; combined sewer overflows (CSOs) • Urban runoff – Runoff from impervious surfaces (streets, etc) • Agricultural operations – Crop production, livestock operations (esp cafos) • Silvicultural operations – Forest management, tree harvesting, logging road construction • Resource extraction – Mining, petroleum drilling, runoff from mine tailing sites • Waste disposal – Landfill leachate, underground injection, incineration (followed by atmospheric deposition of pollutants) • Hydrologic modification – Channelization, dredging, dam construction, removal of riparian vegetation, streambank modification, drainage/filling of wetlands

Water Pollution Summary

US Water Quality • Classification – Good • Water quality is sufficient to meet all designated uses – Impaired • Water quality is insufficient to meet at least one designated use • State obligated to develop “TMDL” rules for impaired water bodies • Some Designated Uses (varies by state) – Food supply • Fish consumption • Shellfish consumption – Water supply • Public drinking water • Agricultural (irrigation) – Recreation • Swimming (primary contact) • Boating (secondary contact) – Ecosystem health • Aquatic life support • Wildlife support

US Water Quality: Common Causes of Impairment

Water Quality in the US (2000): Rivers and Streams • Overall impairment level – • Leading Polluting Sources 1. 2. 3. 4. 5. • 39% of rivers and streams are impaired for their designated use Agriculture Hydrologic Modification Urban Runoff Forestry Sewage Discharges Leading Pollutants/Stressors 1. 2. 3. 4. 5. Pathogens Siltation Habitat Alterations High BOD Nutrients

Water Quality in the US (2000): Lakes, Reservoirs, Ponds • Overall impairment level – • Leading Polluting Sources 1. 2. 3. 4. 5. • 45% of lakes, reservoirs, and ponds are impaired for their designated use Agriculture Hydrologic Modification Urban Runoff Unspecified Point Sources Atmospheric Deposition Leading Pollutants/Stressors 1. 2. 3. 4. 5. Nutrients Toxic Metals Siltation TDS (ie, high salinity) High BOD

Water Quality in the US (2000): Estuaries • Overall impairment level – • Leading Polluting Sources 1. 2. 3. 4. 5. • 51% of estuaries are impaired for their designated use Sewage Discharges Urban Runoff Industrial Atmospheric Deposition Agricultural Leading Pollutants/Stressors 1. 2. 3. 4. 5. Toxic Metals Pesticides High BOD Pathogens Toxic Organics

Water Quality in the US (2000): Great Lakes • Overall impairment level – • Leading Polluting Sources 1. 2. 3. 4. 5. • 78% of Great Lakes Shoreline waters are impaired for their designated use Contaminated Sediments Urban Runoff Agricultural Atmospheric Deposition Habitat Modification Leading Pollutants/Stressors 1. 2. 3. 4. 5. Toxic Organics Nutrients Pathogens Siltation High BOD

Virginia Water Quality

VA Water Quality • Leading causes of impairment – Rivers • • Major: Pathogens (fecal coliform, e coli) Others (minor): DO, p. H, freshwater benthics, PCBs in fish – Lakes 1. DO 2. PCBs in fish – Estuaries (Chesapeake) 1. PCBs in fish 2. DO 3. Benthics (more minor)

VA Water Quality Trends

VA Chesapeake Bay: Oxygen Depletion

VA Chesapeake Bay: Submerged Aquatic Vegetation • SAV goal: 77, 463 acres – 37, 640 acres attained – 38, 823 acre shortfall