Chapter 15

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 O2 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 mi2 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• CO2, 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

Global Warming Discussion