Water Pollution

Types of Water Pollution Point Source –From a single, traced source –Ex: drain pipes, effluent of sewage treatment Nonpoint Source –Scattered; cannot be traced to a source –Ex: fertilizer/pesticide runoff, sediment pollution from lawns

Sources of Pollution Agriculture is largest source of water pollution –Types of Pollutants: Sediment, fertilizers, pesticides, fecal bacteria, salt Industrial activities also large source –Types of Pollutants: Chemical pollutants, heated water Mining –Types of Pollutants: Toxic chemicals of mining materials runoff into water

Oxygen-demanding Wastes Wastes that deplete water of dissolved oxygen Anything that is biodegradable qualifies –Bacteria degrade or decompose the wastes –They use oxygen to do this –Oxygen is used from water for this decomposition

Biological Oxygen Demand A stream with lots of biodegradable wastes will have a high biological oxygen demand (BOD) –This means, it will have a large demand for oxygen from organisms (bacteria)…usually means polluted, and ultimately a loss of oxygen –This is a common water quality test…often used to determine if oxygen-demanding wastes are around Frequently looking for sewage

Cultural Eutrophication Defined as: Process of nutrient addition to water by humans Nutrients usually in the form of fertilizer Fertilizers carry a combination of N-P-K (nitrogen, phosphorus, potash) –Fertilizers always have a N-P-K ratio, indicating what % of the fertilizer is what. – fertilizer has 10% N, 15% P, and 5% K Some nutrients found in detergents/soaps (phosphate)

Cultural Eutrophication -- Steps Excess nutrients (N, P, K) incite plant growth. In water, this means algae. Algal blooms occur in water Algae die! They are decomposed by bacteria. Bacteria use oxygen for decomposition Oxygen gets all used up. This oxygen-depleted area (hypoxic area) is a “Dead Zone” –Organisms needing dissolved oxygen will die

Effects of Algae Blooms Dead Zones (hypoxic zone) –US has largest Dead Zone in Gulf of Mexico (all fertilizers in Mississippi River dump here) –Gulf Dead Zone is size of the state of Connecticut. –Problem is worse due to wetland loss (wetlands would filter out the fertilizer nutrients) Some algal blooms can be hazardous to human health –Often called red tides or harmful algae blooms –Certain species of algae give of toxins that can kill people or make very sick

Solutions? Yes…this is reversible!! Dead Zones have shrunk, especially when not using fertilizers –Often shrink during economic recessions –People simply don’t use as much fertilizer Banned phosphates from detergents Apply the right formula of fertilizer to the needed area (get your soil tested!)

Review Questions 1) Waters with high amounts of fertilizer pollution will have: A) Low BOD levels B) Low phosphate levels C) Low levels of eutrophication D) Low CO 2 levels E) Low dissolved oxygen levels 2) Identify 2 environmental impacts of the addition of fertilizer to an aquatic ecosystem. 3) Identify 1 economic impact of increased flow of fertilizer into the Gulf of Mexico 4) Identify the organism directly responsible for hypoxia.

Oil Pollution Most oil pollution is actually runoff from land – NOT oil spills Oil kills organisms due to volatile compounds in it –Tar balls also coat feathers/fur, reducing buoyancy & movement Oil will settle in organisms in the food chain for years Oil spill cleanup only recovers about 15% of spill. Best way to deal with spills it to PREVENT them.

How Do You Clean Oil Spills? Skimming oil off water Burning oil –This releases toxic fumes into air Set up booms (barriers to contain oil) Use of absorbent materials to suck up oil (e.g. Hair or hay) Dispersants – chemicals to break oil down faster and into smaller droplets Oil-eating Bacteria – naturally consume crude oil

Famous Oil Spills 1989 – Exxon Valdez –Operator error lead to grounding of this vessel in Prince William Sound in Alaska –11-25 million gallons of oil spilled –Loss of many species (birds, otters, seals, whales); –Area still coated in oil tar on rocks today…oil still exists in the food chain

Famous Oil Spills 2010 – Deepwater Horizon (BP) –Off shore oil rig explosion and safety equipment malfunction (blowout preventer) –Largest oil spill in history –Spilled into Gulf of Mexico –Official estimate of around million gallons/day into water –Well open from 4/20 to 7/15 –Used lots of dispersants, which have potential toxic effects –Effects are unknown; Oil and dispersants likely to move through food chain and poison