Status of pollution Threats to our environment Relationships between air pollution, plants, & soils Damage caused by sediment
Problems are becoming worse We’re getting more proactive/aware Pollution – adding something to air, water, soil that makes it less desirable for human use of less able to maintain nature’s balance What are some examples of pollutants?
Us Some of our actions, innovations, technology, industry inherently degrading to environment Even though we didn’t know it at the time Loss of Biodiversity Loss of species locally or globally 90% of world’s food produced on 30% of the land Modifications of Landscapes & Climate Replacing nature’s way
Drained wetlands Man-made structures Water withdrawals Overexploitation Excessive fishing, lumbering, hunting, farming Introduction of Nonnative species Noxious weeds Predatory animals/insect species Pollution of Fresh Water Some rivers/lakes becoming less safe for drinking or recreation
Soil degradation Threatens land Crusting, compaction, erosion, nutrient depletion, etc.
Eutrophication – water overly enriched w/ nutrients forming algal bloom (robs O 2 from water) Half-life – time for ½ of substance to be destroyed, inactivated Total Maximum Daily Load (TMDL) – regulatory maximum amount of pollutants allowed in water – controversial – used by EPA Don’t forget to check out the rest of the terms on pg 461
Eutrophication of Surface Water Fertilizers increase algal growth in water Eutrophication accelerates algal growth & O2 tie-up N & P are the major culprits P pollution sources Municipal sewage Direct dumping of wastes Eroded phosphate fertilizers
Dead Zone – eutrophic zone at end of Mississippi River – extensive aquatic death in 8000 mi 2 area N in Groundwater N easily washed away ~½ of all N applied not used by crops Not all N pollution from agriculture Maximize N usage by plants, minimize excessive N fertilization
Methemoglobinemia Reduction in oxygenation of blood causing suffocation Cyanosis – “Blue Baby” syndrome in humans Related to high nitrate levels in drinking water Upper limit 45ppm in drinking water Can be a problem w/ well water
Wastewaters Added to Soils Sewage sludge, industrial wastes Many household chemicals found in wastewaters EPA restrictions tightening to protect waters Sewage Sludge Has often been buried in landfills Can be land-applied & be just as helpful as animal manure Toxic metals, pathogenic organisms, human vectors (rats, mice, mosquitoes) can be problematic
Livestock Manures Manure = #1 product of American agriculture 1.4b t produced annually Trend toward fewer, larger animal production units causing more concentration of manure What are our options? Manure nutrient content varies w/ rations Concentrated in some undesirable nutrients (salts)
Municipal Garbage, Composts, Sanitary Landfills Recycling has improved Toxic cleaners, pesticides, medicines, solvents, etc. are the major problem/risk Increased tonnage & tighter regulations making more problems Food-processing Wastes Pea pods, tomatoes, peanuts, etc. Organic (except for any chemicals used in processing) & can be composted Wash water can also pollute, should be treated
DDT Developed in 1880’s Kills almost all insects easily & quickly Mosquitoes Low toxicity to humans, animals Inexpensive & long lasting Two major drawbacks: Long ½ life (10-25 yrs) Accumulates in animal fats – birds eat dead insects, kills birds U.S. banned in early 1970’s
Pesticides Today Many hundreds of pesticides available Acceptable pesticides must have following characteristics: Short-lived in environment w/in 1-2 wks, or 1-2 d Not carcinogenic, teratogenic, mutagenic Effective & practical to use Not volatile Safe to apply w/ reasonable care Stay where applied
Pesticide Problems & the Extent of Pollution Toxicity to humans & animals major concern Some argument as to safe/acceptable levels Resistance becoming a problem To what? How? What are our options? Ag accounts for 2/3 of all pesticide use in U.S. Atrazine most applied herbicide High risk for pollution due to being sprayed on bare soils, early spring, more rain
Very immobile in soils, tightly held Can result from many sources Sludges, fertilizers, atmosphere (ore smelting), paint waste, etc. Some sources now closed, tightly regulated, installed more environmentally friendly equipment
Toxic plants to animals (can be in certain soils) Weeds, nutritive elements Those using pasture in their animal production units must have idea of risk, be able to identify symptoms
Lead Contamination Some say most important environmental hazard world-wide Atmospheric lead sources – burnt fuel in autos Decreased now w/ lead-free gas Soil Pb levels still high near roads Can cause brain damage Field Burning Traditionally used to control weeds, insects Risk from smoke Reduced visibility – auto accidents Air quality issues
Acidic Rain & Fog Acid rain – rain w/ pH <5.6 Most severe near heavy industrial areas Sulfuric acid & nitric acid Acid fog – acidity more concentrated – pH 2-3 Can cause serious injury to plants EPA regulations have improved this problem Acid rain emissions down 62% from 1970’s
Ozone Depletion & Enrichment Ozone – screens 99% of UV rays from Earth Chlorofluorocarbons (CFC’s) Where do they come from? Have been banned? Ozone declined steadily until mid 90’s, now evidence of recovery Greenhouse Gases Components that trap heat near Earth’s surface CO 2, nitrous oxide, methane, etc.
Abundance of these gases causing “Global Warming” Many disputes Some historical data used is projected or estimated See figure 15-12 on pg 478 Evidence of ice melting Evidence of animal migration away from warmer areas Some arguing this is in preparation for another mini “Ice Age”
Sediment Problems Both physical & chemical problem Filling in of waters Pollutants carried w/ it Sources/causes: Eroded topsoil High in nutrients Filling of water reservoirs Reduced sunlight penetration into water Lower amounts of food produced for aquatic organisms
Covering of good topsoil w/ poorer sediment Raising of river beds – more prone to flooding