Monday April 16, 2012 Goal: Learn as much as possible in not enough time!!!. Warm UP: What are the main sources of air pollution? Acid Rain Webquest. Water ppt. Homework: Do Greenhouse effect tutorial (on website) Do Reading and questions on Ozone. Watch frontline video, do reading and questions on waste water.

Wiseman IB Chemistry Types of Aquatic Ecosystems Freshwater: lakes, rivers Salt: oceans Estuaries: where fresh meets salt Provides variety of habitats, supporting diverse animal and plant communities  Migratory populations  Spawning grounds  Bay grass protects juvenile fish and crabs from predators Filtration system, prevent erosion Wetlands: Where land meets water Tidal vs non-tidal Emergent, shrubs, forested

Wiseman IB Chemistry Abiotic Factors affecting Aquatic Ecosystems Light  varies w/ depth, particulate matter  Photosynthetic organisms... Temperature  varies w/ depth and season  Convection Solubility of solids/liquids  Salinity  pollutants Solubility of gases CO 2  oceans as carbon sink, leads to acidification  Important component of carbonate shells  Food for autotrophs O 2 Acidity  Lower pH results in more metals soluble in water  Certain level for which organisms adapted How these factors affect the Chesapeake Bay Water quality in the bay

Wiseman IB Chemistry Nutrient Cycling in Water Aerobic Get energy through oxidation Produce  CO 2, NO 3 -, PO 4 3- Anaerobic: get energy through reduction of oxides when there is little O2 Production of  ammonia, amines  Methane (biogas or marsh gas)  Hydrogen sulfide  Phosphine (PH 3 ) Movement of nutrients through an ecosystem determines what organisms can survive

Wiseman IB Chemistry Current State of Fresh Water Resources Physical and economic water scarcity and limited or reduced access to water are major challenges facing human society and are key factors limiting economic development in many countries. (MEA) Water scarcity and declining access to fresh water are a globally significant and accelerating problem for 1–2 billion people worldwide, hindering growth in food production and harming human health and economic development. (MEA) Drivers of degradation:  Population growth and Economic development (Everglades)Everglades  Pollution  Land conversion  Water withdrawal  Overharvesting and over exploitation

Wiseman IB Chemistry Pollutants Chemical Nutrients: N, P Toxins: organics, metals Heat Source  Energy (cooling towers)  Global warming Results:  Small range of temperatures over which aquatic organisms are adapted.  Changes metabolic rates  Removes dissolved gases (O2)  Coral bleaching Coral bleaching  April 2010: report: Potomac River showing statistically significant long-term warming. Lake Michigan

Wiseman IB Chemistry Desalination Distillation Basically: boil the water off and collect it Made more efficient if done in stages  As water condenses, it gives its heat to the next stage for boiling

Wiseman IB Chemistry Desalination Osmosis: Natural flow from high to low concentration thru semi- permeable membrane Results from “osmotic pressure” Reverse Osmosis Make it go the other direction by applying pressure Put simply, desalination purifies water by removing dissolved mineral salts and other solids. In the Middle East, most desalted water is produced by means of distillation, which imitates the natural water cycle: Salt water is heated to produce water vapor, which then condenses to form freshwater. American desal plants favor a different technology -- reverse osmosis -- which forces the water through a series of membranes, leaving the salts behind. Illustration: Colin Hayes OnEarth. Summer 2004 Copyright 2004 by the Natural Resources Defense Council

Wiseman IB Chemistry Eutrophication Eutrophication is the build up of nutrients in the water system. Nutrients support the growth of autotrophs (algae) Algae block sunlight from getting to lower levels of the ecosystem Algae die and as other organisms eat them, oxygen in the water is depleted Low levels of oxygen in the water result in hypoxic conditions where fish and other organisms that respire aerobically cannot live.

Wiseman IB Chemistry Biochemical Oxygen Demand Measure of amount of oxygen consumed by the biodegradable organic wastes and ammonia in a given amount of water over a time period (5 days at 20 C) Sample saturated with O 2 and put in closed container. After 5 days, dissolved O 2 lost is measured The more O 2 lost, the more organisms are in the water using up the oxygen BOD < 1 almost pure water BOD 5 Doubtful purity BOD 20 Unacceptable purity

Homework Read the Ozone article and answer questions attached. Watch the frontline video on water pollution at: ew/ Read ChemMatters Article on Water Treatment and answer questions attached. Wiseman IB Chemistry