ESM 202 Environmental Biogeochemistry

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ESM 202Environmental Biogeochemistry

• John Melack and Trish Holden

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Objectives

• Apply biogeochemical understanding to important
  environmental issues
• Understand SOURCES, RESERVOIRS and PROCESSES of
  pollutants and nutrients
• Provide basic biogeochemical knowledge for making
  sound environmental decisions

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Relevance

• Management of nutrients in a watershed to avoid
  eutrophication
• Develop a sound environmental restoration program
• Design a successful remediation program for
  contaminated site
• Understand the greenhouse effect, its drivers and
  the possible solutions

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Terminology

• Reservoir (M) an amount of material defined by
  physical, chemical or biological characteristics.
  There may also be physical boundaries. Examples
• carbon in the atmosphere (CO2, CO, CH4, VOCs,
  etc.)
• nitrogen in soil (NH4, NO3-, DON, etc.)
• sulfur in sedimentary rocks (as S, SO4 or S2- ,
  bound as FeSO4, FeS)
• phosphorous in lake water (as P, or PO42-)

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Terminology

• Flux (F) the amount of material transferred from
  one reservoir to another per unit time (m L-2
  t-1)
• carbon dioxide to atmosphere from combustion of
  fossil fuels
• nitrogen deposition from the atmosphere to land
• phosphate leaching out of the soil into rivers
• VOC emissions from human activities into the
  atmosphere or to groundwater

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Terminology

• Process A physical, chemical or biological
  activity that results in a flux or change in mass
  or chemical form
• evaporation
• photosynthesis
• oxidation (CH4 in atmosphere)
• biodegradation

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Terminology

• Cycle
• A system with two or more reservoirs connected by
  fluxes
• May be closed or open (i.e. some mass is gained
  or lost by the system)
• Processes occur throughout

Atmosphere
Biota
Soil
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Terminology

• Compartments or Phases
• Atmosphere
• Water body (e.g. lake, river, ocean, pond)
• Soil
• solid phase (e.g. sand, clay)
• gas phase in the soil
• water phase in the soil (e.g. moisture or fully
  saturated)
• organic phase in the soil (Soil Organic Matter,
  biota)
• Biota

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Terminology

• Source (Q) a flux into a reservoir
• Sink (S) a flux out of the reservoir
• Budget
• A balance sheet of all sources and sinks of a
  reservoir or a combination of reservoirs. If at
  steady-state,
• dM/dt 0
• M constant
• We can use a budget of known sinks and sources to
  determine the value of one unknown sink or source.

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C (concentration of P)
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System Analysis
IN Out Change in System
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System Analysis
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System Analysis

• The Model
• is typ. expressed as a differential eq.

QiCP,i?t QoCP,o ?t V?C
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Linear Systems

• The fluxes between reservoirs are approximated
  with a linear function

Fij kij Mi
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Non-Linear Systems

• Exchange of carbon dioxide between ocean surface
  water and atmosphere is non-linear
• Ms is the mass of all forms of dissolved
  inorganic carbon (CO2, H2CO3, HCO3- and CO32-)
• bsa is the buffer factor - results from the
  equilibrium between CO2(aq.) and the other forms
  of inorganic carbon, and has a value of about 9

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Environmental Analysis of Urban Ecosystems
Larry Baker and Chuck Redman Phoenix-Central
Arizona Project NSF Long-Term Ecological
Research Program
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Ag submodel for the Phoenix-CAP Ecosystem Values
in 106 kg/yr (Baker et al., in review)
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Mixing
Lake
Q2 CP,2
Volume (V) ?C
Qi CP,i
Q1 CP,1
Qo CP,o
Knowing Q1, CP,1, Q2, and CP,2, what are Qi and
CP,i?
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Mixing
Flow Balance Q1 Q2 Qi
v
P Mass Balance Q1CP,1 Q2CP,2 QiCP,i
v
mixing equation
Solve for CP,i
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Loss
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Biological Stoichiometry

• Redfield formula (marine phytoplankton)
  (CH2O)106(NH3)16(H3PO4)
• Redfield ratio C106N16P1

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Prokaryotes simple microbes

• Estimated 5 x 1030 cells on Earth
• Compare to 6 x 109 people!
• Contain ca. 500 Pg C (1 Pg 1015 g)
• Equals plant C reservoirs
• Contain ca. 100 Pg N and 10 Pg P
• 10 times higher than plants
• Open ocean, soil, subsurface
• Turnover times fast (1 wk to mo., ½ yr, several
  years or more)

(REF Whitman et al. PNAS 1998)
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Microbes

• Large pools of C, N, P
• And thus, K, Fe, S, etc.
• Recyclers
• Decomposition
• Polymers to monomers
• Monomers to CO2, CH4
• Biodegradation / bioremediation
• C and N fixation
• Consumption of CO2
• N2 capture/ conversion to NH4
• Uptake of other nutrients (e.g. P)
• Changing oxidation states (oxidation reduction)
• Iron reduction Fe3 ? Fe2
• Denitrification NO3- ? N2
• Oxygenating and de-oxygenating water
• Photosynthetic cyanobacteria add O2
• Aerobic heterotrophic bacteria convert O2 and C
  to CO2

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Microbial Uptake
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This course

• Earths chemistry
• Learn about
• macro- and micro-nutrients
• systems perspective
• nutrient cycling interrelationships
• Drivers and controls on cycling
• Issues at global to local scales
• Management responses

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Structure of the Course

• 2 lectures /week (Melack, Holden, others)
• Discussion 1x / week (10)
• Each student chooses and delivers one paper
• Summarize and lead discussion, 10 minutes
• 2 to 3 students per discussion, per week
• Published literature related to a weekly topic
• Get buy-off from professor or TA
• Signup 1st week
• Assignments 1 PS (10), 2 papers (15 ea), 1
  memo (5)
• Midterm (15) and Final (30 )

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Questions??

• John Melack melack_at_bren.ucsb.edu
• Trish Holden holden_at_bren.ucsb.edu