Today-Review exam (briefly)-Biodiversity - Ecosystems-Nutrients as Pollutants - Introduce last class Activity (In-class Debate)

Next Tuesday- Quiz- More Atmospheric Pollutants- Begin Water Pollution

Biodiversity – diversity of life

- Variety of genes among individuals of a species

– color, height

- Variety of Species

- Variety of ecosystems– coral reefs, rainforests

Ecosystems

• an assemblage of different species and their physical environment, all organized in a way that each population of organisms obtains energy and nutrients through specific pathways within the ecosystem.

Ecosystem componentsFunctional groups of organisms

a. Producers (autotrophs)fix energy and inorganic nutrients into organic forms that are accessible to other organisms.

b. Consumers (heterotrophs) get energy and nutrients by consuming the producers.

Decomposers (heterotrophs) get energy and nutrients by decomposing all other organisms that have died.

Physical or Abiotic EnvironmentLandWaterAir

Energy transfer

Unidirectional transfer of energy from one functional group to another until it is dissipated from the ecosystem as heat

Energy is transferred in one direction, from producers to consumers to decomposers.

After decomposers have extracted energy from dead organic matter, the energy is no longer available within the ecosystem.

Fig: ecosystem

Nutrient and material cycling

Cycling of nutrients among the various groups of organisms through trophic (feeding) interactions

Unlike energy, nutrients do not move unidirectionally through the ecosystem. They are recycled through the activity of decomposers, which return the organic nutrients to their inorganic forms.

This process is called mineralization. The mineral nutrients are then available again to producers and microbes that can use them.

slide/ sea urchin

slide/ otter in kelp bed

fig/ otter,urchin, kelp

circle

otters eat sea urchins

sea urchins eat kelp

kelp provides habitat for otter

As we discussed Tuesday, PhosphorusIs very often limiting in freshwater systems

What is happening here?Why doesn’t the line keepGoing up?

Multiple or co-limiting factors – often it is more Complex than Liebig’s Law of the minimum

Look what happens with the addition of N

Increase in autotrophs. . .

Decrease in autotrophs. . .

Primary productivity is an important control on ecosystem productivity and one reason why we focus so much on nutrients

INPUTSWeathering

Atmospheric Input

Biological Nitrogen Fixation

Immigration

OUTPUTSErosion

Leaching

Gaseous Losses

Emigration/Harvesting

Nutrient flux in Ecosystems

Excess Nitrogen – Too much of a good thing!

Because Nitrogen often limits plant growth humanshave gone to great lengths to use it as fertilizer

It is also a by product of all types of combustion

The net result is that we have altered the natural way that Nitrogen cycles more than we have any other element -including Carbon

In an undisturbed nitrogen cycle the element cycles veryEfficiently – it is valuable so not readily given up by biota

In an undisturbed nitrogen cycle the element cycles veryEfficiently – it is valuable so not readily given up by biota

But humans add HUGE amounts of Nitrogen to the ecosystem

160

Nitrogen containing Compounds

N2 – nitrogen gasNO3 – nitrateNO2 - nitrite NH4 – ammoniumNH3 – ammoniaN2O – Nitrous OxideOrganic Nitrogen –Living and dead plantsAnd animals

Human Emissions - Combustion

• NOx

• N2 +O2 --> 2NO

• Forms in high temperatures of combustion engine

• Converted in the atmosphere to HNO3 - nitric acid

From atm.

Human Emissions - Fertilizer

• N2 +Energy H+--> NH3

• Formed by the Haber process• Added to fields all over the

world, but often lost after harvest

Nitrogen from agriculture and from combustion isn’t coupled inA tightly cycling system and often “escapes” into the atmosphereForming acid precipitation

“Natural Rain”• Pure water

– pH of 7 - neutral

• Rain is not pure water – Dissolved CO2

– Forms carbonic acid

• pH = 5.7

• Other dissolved substances

Human Influence• Increasing emissions of NOx

• 55% of NOx emissions are human related

• Regionally these percentages can be much higher– NE US - 65%, Europe - 80%

WHY is acid rain a threat? I                                                                      

•Because acid rain will cause more cases of respiratory disease, skin irritation and eye irritation. People from the Kanto Plains of Japan have experienced severe eye and skin irritation since 1970.

•Because acid rain reduces crop productivity. In the Netherlands, damage to crops is estimated at $182 million a year. In Japan, damage to vegetable crops has been reported.

•Because acid rain corrodes and destroys buildings and monuments. The EPA estimates that annual costs of repairing damage due to acid rain exceeds $5 billion. Marble is particularly vulnerable.

WHY is acid rain a threat? II

•Because acid rain damages plant and animal life in lakes and streams. Lakes die, rendering them unable to support life.

•In Maine, 2% of trout habitats and 6% of minnow habitats are no longer able to support animal life.

•More than 1/2 of lakes currently being studied in Canada have lost 40-50% of species such as mollusks and insects.

•Florida has the highest percentage of acidic surface waters - 23% of lakes and 39% of streams.

WHY is acid rain a threat? III

Because acid rain harms forests. Over 20-25% of European forests are classified as moderately or severely damaged. In France, 10-20% of trees in sensitive regions have lost more than 25% of their foliage.

•Because acid rain degrades soils. In Sweden soils have become up to thirty times more acidic in the last sixty years, and the acid deposition extends several meters below soil surface.

What happens to the rain when it hit the ground?

• Acid in rain ….• … will react with a base in soil• Many of our mobile ions produced in

chemical weathering can “neutralize” the acid

• Base Cations: Ca, Mg, Na, K• What determines the neutralization capacity

of soil?

Acid Rain

• Reactions to convert to acid take place in ~2 days - travel 1000 miles

• Down wind - Acid rain

• Dry Dep. vs Wet Dep.

• Dry Deposition – 50 % of total

– Can react with plants - strip nutrients

– Tree dieback

pH of Rain - Eastern US

• pH of rain over the Northeast averages in around 4.5

• Note that in the early years the range is expanding

• 1990 things are getting better...

pH Rain - Europe

• Europe experiences similar acid rain

• Coal burning in England and Germany

Emissions vs. Effects

• All areas receiving acid deposition are not susceptible to the effects of the rain….why?

Acid Rain and Trees

Forests affected by Acid RainNortheast USCanadaNorthern EuropeAsia

Acid Rain and Buildings

Many buildings are made of concrete and or stone

These compounds act as bases and react with acid

The building technically “weathers” very fast, orNon technically “crumbles”

Europe

The US Capitol

When the pH drops below 6.0 species start to die off.When one species dies, others that depend on it may as well

Acid Rain Effects – Aquatic Systems

Acid Neutralization

• How does this work?• Cation Exchange on

clay minerals• Role of chemical

weathering...

How does acid kill the fish?One way is mobilizing metals

• When all base cations are striped from soils

• Acid now reacts with metals e.g. aluminum – Normally aluminum is immobile– below pH 5 - mobile aluminum

• Fish breath in the water – Aluminum comes out of solution– Clogs gills - suffocate

Where do N emissions originate?

~ 55% come from agriculture

~ 25% come from industry – e.g. coal fired power plants

~ 20% come from automobiles

Major powerplants – sources of N emissions – Acid rain

Change in NOx emissions 1990 - 1999

Nitrogen deposition 1989 - 1991 Nitrogen deposition 1995 - 1998

Surface water sensitivity to Acid Deposition - known in 1990

Surface water sensitivity to Acid Deposition - known in 1998

Watersheds – Large areas thought to be nitrogen saturated

Land - Sensitive Ecosystems to Nitrogen Deposition

Change in NOx emissions 1990 - 1999

19905,700

199811,600

Emissions increasing in the western US

199015,800

199817,600

Emissions increasing in the western US

199024,700

199828,800

Emissions increasing in the western US

Recent and current policies to reduce acid precipitation andNitrogen emissions are shifting the problem from one area To another

While emissions are remaining stable or decreasing in alreadyHeavily impacted areas, they are increasing in formerly“clean” or relatively unimpacted areas -Especially including other countries!

-Nitrogen is only one compound important in acid rain andpollutant emissions to the atmosphere

sulfur – SOx – has been a relative success storymercury is not an acid forming element, but is extremelytoxic and is still increasing

Acid Rain Summary

http://www.epa.gov/airmarkets/picturethis/index.htm

http://www.epa.gov/castnet/charts.html

For more information see

Acid Rain Effects

• Other animals suceptible