Forms of Nitrogen N2N2 X R-NH 2 R-NH 2 is organically bound form of nitrogen NH 4 + Decomposition Of O.M. Uptake by plant Uptake by plant NO 2 - NO 3 - nitrosomonas nitrobacter NH 4 + is exchangeable, NO 3 - is not

Rhizobium Symbiotic Biological Nitrogen Fixation Symbiosis between plant roots and rhizobium bacteria Nodules are packed with Rhizobium N2N2 NH 4 + gas mineral

Nitrogen Fixation is Difficult and Specialized N 2 + 6H 2 2NH 3 Fixing N 2 is energetically “expensive” NNTriple bond –Must use energy to break these bonds

Artificial Nitrogen Fixation Haber - Bosch Process - Artificial Fixation of Nitrogen Gas: –200 atm – o C –no oxygen yield of 10-20% Produces 500 million tons of artificial N fertilizer per year. 1% of the world's energy supply is used for it Sustains roughly 40% of the world’s population

Nitrogen and Food 70% of water used Food production has grown with population Crop Varieties Fertilizers

Nitrogen Fertilization NO 3 - Negative Exchange sites Loss of Productivity Leaching to groundwater, surface water NO 3 - NH 4 +

Mineral Forms: NH 4 + and NO 3 - NO 3 - is more mobile in the environment than NH 4 + _ _ _ _ _ __ _ _ NH 4 + NO 3 - Leaching to ground Or surface water Loss of Productivity Leaching to groundwater, surface water

Some Areas of Florida are Susceptible

Approximately 250 million years ago

Approximately million years ago Flooded, stable platform Subject to marine sedimentation FL platform/plateau For the next several million years the platform was dominated by carbonate sedimentation Late Jurassic Sedimentation: settling of particles from a fluid due to gravity

Carbonate Deposition/Sedimentation Marine Calcium and Magnesium Carbonate CaCO 3 MgCO 3

Florida platform was a flooded, submarine plateau dominated by carbonate deposition FL platform CaCO 3 Between about 150 Mya and 25 Mya

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The Eocene and Oligocene limestone forms the principal fresh water-bearing unit of the Floridan Aquifer, one of the most productive aquifer systems in the world Eocene: 55 – 34 million years ago Oligocene: 34 – 24 million years ago The Eocene and Oligocene Limestone

carbonates Prior to 24 Mya Marine Carbonates Between 150 and 25 Mya, Florida was dominated by carbonate deposition

Continental Influences highlands Sediments

Isolation of the Florida Peninsula Suwannee Current Georgia Channel Sediments

Lowering of Sea Levels, Interruption of Suwannee Current Suwannee Current Events of the Late Oligocene Epoch, approximately 25 Mya Raising of the Florida Platform

Exposure of Limestone The Oligocene marked the beginning of a world wide cooling trend and lower sea Levels. Erosion cavities Due to acidity

Rejuvenation of Appalachians, weathering, increased sediment load sediments Miocene Epoch: began approximately 24 Mya Sediments were sands, silts, clays

Sediments Filling in the Georgia Channel Early Miocene (~ 24 Mya)

Sediments Rising sea levels allow sediments to become suspended in water and drift over the platform

Siliciclastics Covered the Peninsula Sands And Clays

1.Deposition of Eocene/Oligocene Limestone (55 – 24 Mya) 2.Raising of the Florida platform 3.Lowering of sea levels, interruption of the Suwannee Current 4.Infilling of the Georgia Channel with sediments derived from Appalachian/continental erosion 5.Sea level rise, lack of Suwannee current. 6.Suspended siliciclastic sediments settle over the peninsula 7.These sediments blanket the underlying limestone forming the upper confining layer for the Floridan Aquifer. Summary

55 – 24 million years ago Clays and Sands (low permeability) Surface Siliciclastics (sandy) (highly permeable) The Floridan aquifer is a confined aquifer. The water-bearing unit is permeable limestone. Low Conductivity Confining Unit (poor water movement) Unconfined aquifer is extensive throughout the state of Florida Low permeability rock (confining) Conductivity: the ease with which water moves through material

Calcium Carbonate CaCO 3 The Water-bearing Unit is Extremely Productive Magnesium Carbonate MgCO 3 How does this material hold and deliver water? limestone

Carbonate Dissolution Acid (H + ) dissolves calcium carbonate Carbonates are made porous by acid dissolution

Carbon dioxide dissolved in water produces carbonic acid CO 2 + H 2 O = H 2 CO 3 (carbonic acid) H 2 CO 3 => H + + HCO 3 - Acid Rainfall is naturally acidic

CaCO 3 + H + = HCO Ca 2+ Acidity from rainfall reacts with CaCO 3 and dissolves the carbonate rock. (solid)(solution) (acid) (solution) CO 2 + H 2 O = H 2 CO 3 H 2 CO 3 => H + + HCO 3 - Dissolution Cave Dissolution Cavities

Caves and Solution Cavities Acid dissolves calcium carbonate CaCO 3 + H + = HCO Ca 2+ Carbonates Clayey Deposits Channels and Caves

Karst Topography Characterized by sinkholes, springs, depressions, lakes

Sinkhole Lakes Florida is Dominated by Karst Topography

Sinkhole formation depends on the material overlying the carbonate water-bearing unit Thin, sandy covering Thick sands up to 200 ft thick and some clays Cohesive clays up to 200ft Very thick clays > 200ft. Miocene clays have been eroded and shaped throughout their history resulting in extreme variability in thickness across the state.

The Importance of Sinkholes and Sinkhole Lakes Hydrologic connections between the surface and the underlying limestone are maintained.

Florida: Nitrates (NO 3 - ) Nitrates do not interact significantly with soil material and can move rapidly to groundwater. 3. Areas where the aquifer confining unit is thin are also particularly vulnerable. What areas are particularly vulnerable? 2. Areas where natural groundwater recharge occurs 1. The unconfined, surficial aquifer

residential and commercial septic systems in rural areas about 300 row crop and vegetable farms 44 dairies with more than 25,000 animals 150 poultry operations with more than 38 million birds Lower Suwannee River Watershed Nitrates NO 3 Drinking water standard: 10 ppm

Possible sources of nitrate in the ground water in the vicinity of the river include fertilizer, animal wastes from dairy and poultry operations, and septic-tank effluent. Nitrate concentrations were higher in the measured springs than in the river. Flow Groundwater Nitrate Discharge to Rivers

Phosphorous

Importance Essential Macronutrient Limiting Resource Present in Fertilizers, animal wastes, wastewater Availability can be very limited

Organic Phosphorous Components of soil organic matter and plant tissue Phosphate sugars Nucleic Acids (DNA/RNA) ATP Phospholipids ATP

Fertility % of applied fertilizer phosphorous used by plants - the rest is bound to soil particles or forms insoluble solids =>excess application =>saturation of soil capacity -Total soil phosphorous is low -Most of the total is unavailable to plants -Much of soil P forms insoluble solids (limiting to availability)

Soil Phosphorous PO 4 -3 Inorganic H 2 PO 4 - HPO 4 -2 H 3 PO 4 (Orthophosphate) The form of available phosphorus is pH-dependent

Plant Availablity H 2 PO 4 - HPO 4 -2 pH 3-6pH 8-11 pH 6-8 Optimum pH = 6.5 for mineral soils Most Available

Acidic Soils

Acid Soils (Low pH) Aluminum and Iron availability increased at low pH Al(OH) 3 FeOOH Solubility increased Al 3+ Fe 3+ Al(OH) 3 + 3H + = Al H 2 O example

Aluminum Precipitation at Low pH H 2 PO 4 - (pH 3-6) Al 3+ + H 2 PO H 2 0 = Al(OH) 2 H 2 PO 4 + 2H + (Insoluble) Al(PO 4 ) H 2 O Variscite Al 3+ + PO 4 -3 = Al(PO 4 ) simplified Form of available P at low pH: H 2 PO 4 - combines with free Al 3+ and Fe 3+

Basic Soils (High pH)

Calcium Binding in Basic Soils CaCO 3 CaCO 3 + 2H 2 (PO 4 ) - = Ca [H 2 (PO 4 )] 2 + CO 3 2- CaHPO 4 Ca 5 (PO 4 ) 3 OH (Apatite mineral) (higher calcium availability) H 2 (PO 4 ) - is the available form of P

Availability and pH Availability and pH Low pH High pH Aluminum and Iron phosphates Calcium Phosphates Formation of insoluble solids

Reaction with Soil Minerals

Anion Exchange It is possible for clays to develop positive change at their edges when they are broken during weathering H 2 PO 4 - Small quantities of P

Fixation on Iron and Aluminum A dominant interaction between Phosphorus and soils is strong interaction with Iron and Aluminum Oxides Al OH Fe OH

Fixation: Aluminum/Iron oxides Fe OH H 2 (PO 4 ) - + Fe FE OH H 2 (PO 4 ) - OH- +

Fe OH P O-O- O-O- + Fe OH P O-O- O-O-

Coatings on Sands and Silicate Clays Fe coating Fe OH H 2 (PO 4 ) -

Organic Matter Organic matter does not typically bind strongly with phosphorus. Organic matter covers fixation sites Organic matter reacts with free Fe and Al Organic matter competes for anion exch. sites Organic Matter tends to increase P availability

-Plant Available -Fe, Al bound -Calcium bound -exchangeable - Fixed on oxides H 2 PO 4 - HPO 4 -2 Al(PO 4 ) H 2 O Ca 3 (PO 4 ) 2 H 2 PO Inorganic Soil Phosphorous Inorganic (low)

Next: Phosphorus and South Florida