Environmental Geology Final Exam

What are the three signals influenced by earth’s axis?

Precession

Obliquity

Eccentricity

Precession

Affects how much summer sun is received at high latitudes

More sun received by land = warmer planet

Land reflects the heat back up  

Obliquity

Tilt of earth’s axis relative to the sun that changes how much sun is received during a year at the poles vs equator

Eccentricity

Change in the shape of earth’s orbit around the Sun that alters the length of the seasons and affects the importance of precision

Tectonic cycle

Mountain building can cool the planet by pulling CO2 out of the atmosphere 

Why did the CO2 go up in the 1960s?

The highway system

Mass production of cars

People started flying more 

As countries develop economically, people have the freedom to move around and travel more

Overall growing populations and rising prosperity

Proxy measurements of CO2

Stomata

Phytoplankton

Boron

Is CO2 the major reservoir for carbon?

No

Other major reservoirs for carbon

Carbonate rocks

Plants/Living

• Leave behind organic carbon reservoirs when they die

Carbon that forms in soils

Bicarbonate

• Infiltrates streams and aquifers

Oxidation/Respiration

• Does this through animals and plants 

What are the most common minerals in silicate rocks?

Feldspars

• named based on which cation is in them

Albite

Anthrite

Which feldspar is dominant in calcium?

Anathrite

• The most easily dissolved minerals

• Calcium doesn’t fit that well

Example of a positive feedback loop

Albedo effect

• Higher temperatures>less ice cover> less sunlight reflected>higher temperatures 

Example of a negative feedback loop 

Silicate weathering

• Higher temperature>more silicate weathering>faster trapping rate of CO2>lowers atmospheric CO2>Lower green house gases> lower temperature 

Three different weathering methods

Equilibrium Limit

Kinetic Limit

Mineral Supply Limit

Equilibrium limit

Mineral reacts quickly

Reaches equilibrium in the dissolved solutes around that rock

Reaction rate slows down because it reaches equilibrium 

Kinetic Limit

Minerals weathered very slowly

The reaction is too slow to reach equilibrium

• Ex: Feldspar 

Mineral supply limit

The ractio is so quick, it uses up the mineral completely

Rain doesn’t react with tht mineral anymore

Trace amounts but reacts quickly

Transport of minerals to weathering zone

Arrhenius Equation

Test the strength of the negative feedback loop

Reaction rate constant and how it changes with temperature

Inorganic Chemicals

Arsenic

Lead

Fluoride

Maximum Contaminant Limit (MCL)

Legally required and enforceable

Maximum Contaminant Level Goal (MCLG)

Desirable but NOT enforceable

What caused the lead to be released into the pipes in Flint, Michigan?

Flint was cutting costs and did NOT put orthophosphate into the pipes

Orthophosphate is an anti-corrosion agent 

Why did bacteria grow in the pipes?

iron formed ferric chloride, this attached to the chlorine in the water and allowed bacteria to grow

Why was ferric chloride added to the drinking water at the treatment plant?

Ferric chloride is a coagulant

This was added to the water as an attempt to group together the organic chemicals and matter from the river

Why did the water look orange?

This was due to iron oxides from the metal pipe experiencing oxidation 

Why were lead concentrations so erratic across household taps and time?

Some samples depended on the time of day they were collected 

Some flakes of the pipe continued to break off, sending a pulse of lead through the system  

Some EPA protocols were not followed including:

• Sample first thing in the morning before the tap was turned on 

How does the EPA require water samples to be taken for lead exposure assessment from taps?

They are supposed to take samples first thing in the morning before kids get to school

They are also supposed to sample the first water that comes out of the tap 

Science

• Preliminary 

• Self-questioning

• Focused on the process of generating knowledge 

  • Scientific method

• Seeking the general rules

• Minimizes the influence of emotion on perception

• Seeks funding from established public and private organizations

Activism

• Supposed

• Moving forward with evidence at hand

• Focused on change or action

• Highlights extreme cases for shock value

• Seeks funding for private organizations or individuals 

NHANNES

Study that monitored progress of dropping lead concentrations

Arsenic in Asian Deltas: Problem

Arsenic in shallow groundwater in the Ganges-Brahmaputra Delta caused the largest case of human drinking water poisoning ever 

Arsenic in Asian Deltas: Causes 

Arsenic naturally dissolves from minerals in the aquifer or soils 

Associated with redicing high DOC ground waters and monsoonal climates 

Arsenic in Asian Deltas: Impacts

Vast increases in intestinal cancer, Keratosis (skin lesions)  

What are the mitigation options for arsenic in groundwater for the Asian region? 

1. Field Testing 

2. Lateral switching

   1. Switch to a neighbor’s well

3. Drilling deeper

   1. Getting underneath the sediments where arsenic is high 

4. Filtration

Causes of arsenic in Asian Deltas

• High arsenic in aquifers in deltas require organic-rich deposits, alluvial and floodplain deposit and fine textures soils at the surface 

The flatter the land surface = the higher the arsenic concentration is 

• Sediments are finer, the groundwater flows more slowly

• When things slow down there is more arsenic released into the water

Where in the world is high arsenic found?

• High elevation, interior settings

• Low elevation, coastal

• Near major mountain ranges

  • Central Mexico

  • Himalayas

  • Tibetan plateau

• Floodplains and deltas

  • Most of the population live on floodplains and deltas

  • These are also regions vulnerable to increased flooding from sea level rise

What is high arsenic usually paired with?

High arsenic is usually paired with Ammonium

• Active decomposition of organic carbon

High ammonium and high arsenic often go together 

Geothermally influenced water

• Yellowstone

• Hot water coming up to the surface

• Deep earth is the source of arsenic

Reductive Dissolution

• Bangladesh

• Pakistan

  • Lots of primary production

  • Flat topography

  • Long pore water residence time

  • Arseicn released due to reduction of iron oxides by abundance of organic matter

  • Arsenic attached to iron oxide crystals, when they dissolve arsenic is released

Oxidized Desorption

• Oxygenated aquifers

• Arid regions

  • Western US

  • Central mexico

• Evaporation

• Little primary production

• Deep vadose zones 

Due to silicate weathering

• Weathered by carbonic acid

• Silicate keeps raising the pH

• As the pH is raised, it causes the surfaces of iron oxide