Transcript Document

411
2003
Chemistry Lecture Slides
River Ecosystems(3):river chemistry
General conditions affecting River Chemistry
well mixed
•chemically homogeneous
•except hyporheic environment
•thermal stratification rare (occasionally large pools)
generally aerobic environment
•favors oxidation
•suppresses anaerobic processes
•but locally important exceptions (hyporheic, pools, banks, floodplains)
 Concentrations of dissolved material [dissolved load]


in general ionic or polar compounds dissolve best in water
amount of dissolved material is highly variable in nature

commonly dissolved material includes ions from simple salts:
 anions drawn to anode (+ electrode) are negatively charged
 cations drawn to cathode (- electrode) are positively charged

Common gases from the atmosphere
 Dissolved constituents reflect "history" of the water in question
 what kinds of material has the water come in contact with
 source materials include solids and overlying gases
 atm gases

dust, cloud seeds and CL-
 landscape surface and subsurface
 how long the water has been in contact with soluble material
 concentration by evaporation
 evaporation-> "pure" water
 leaves heavier solutes behind
 dilution by addition of less concentrated water
 gains and loses due to in situ reactions [both physical and biologically mediated]
Principal dissolved material in freshwater ecosystems
anions
CO3=
HCO3ClSO4=
OH-
cations
carbonate
Na+
bicarbonate
Ca++
chloride
Mg++
suphate
K+
hydroxide
Fe++
sodium
calcium
magnesium
pottasium
iron
NonN2
O2
CO2
DOC
ionic
nitrogen
oxygen
Carbon dioxide
Diss org carbon
 TDS: a complete but general accounting

Gravimetric Methods
 Total dissolved solids [TDS]
 Total suspended solids [TSS] : an analog for suspended material

Conductivity a common but nonspecific measure of dissolved content
 quick and easy
 basically determined from electrical resistance
 micrmho=microsiemen are the units
 doesn't give indication of non-ionic constituents e.g. dissolved organic matter
 not nec proportion to weight of ionic species
relationships between conductivity and TDS (~2:1)

Photosynthesis and macro-nutrients
6 HOH + 6 CO2 <=>C6H12O6 + 6 O2
stoichiometrically useful but too simplified
a more realistic (but also very simplified) equation for the production
of plant (algae) protoplasm:
106 CO2 + 16 NO 3-+ xPO4 + 122 HOH + 18 H + ENERGY<=> (C106H263O110N16P1) + 138 O2
note molar ratios of 106:16 ( ~12:1) C to N and 16:1 N to P
correcting for molar weights
Necessary Inputs
atomic wt
mg per mole algae wt relative to P
CO2-C
~12
1272
~41
NO3-N
~14
224
~7
PO4=-P
~31
31
1
Energy
How much is a lot?
parameter
Conductivity s
TDS ppm
Alkalinity ppm
Ammonia ppb
Nitrite ppb
Nitrate ppb
SRP (TRP) ppb
TP ppb
low
5-80
<20
<40
<5
<5
<80
<5
<10
medium
90-800
40-400
50-150
20-80
5-20
100-800
10-20
15-30
high
1000+
500+
200+
100+
30+
1000+
30+
50+
What is average?
0. 1 6
Soluble
Reactive
Phosphate
(ppm)
0. 1 2
Variable
pH
Alkalinity
Conductivity
NO2 + NO3 (ppm)
Ammonia (ppm)
SRP (ppm)
Total P (ppm)
Gilvin
Turbidity (NTU)
Mean
7.5
166
416
1.073
0.083
0.022
0.059
0.024
15.980
StdDev
0.5
62
198
2.521
0.162
0.031
0.080
0.020
15.530
E__
0. 0 8
0. 0 4
0. 0 0
Count
131
255
1130
947
833
634
774
242
247
50 ppb
M__
OS
75
100 1 5 0
OH
225
Alkalinity (ppm as CaCO )
10 ppb
Examples of some chemically distinct waters
parameter
Na+ mg/l
K+ mg/l
NH4+ mg/l
Mg++ mg/l
Ca++ mg/l
Cl- mg/l
NO3-N mg/l
SO4= mg/l
CO3= mg/l
PO43+-P mg/l
PH -log10 [H+]
Cond. s
TDS mg/l
continental
rain
0.20
0.15
0.10
0.05
0.10
0.20
0.40
1.00
<1.0
0.010
4.5
6
3
Maine
river
0.90
0.30
0.08
0.40
1.7
0.55
0.06
6.33
7.7
0.010
4.9
36
18
Michigan
river
15.00
3.60
0.04
7.70
33.00
19.00
0.50
69.00
100.0
0.030
7
496
249
Seawater
11000.00
399.00
0.04
1290.00
412.00
19354.00
5.00
2712.00
120.00
0.025
8.1
70000+
35292
River Ecosystems(3):river chemistry
…three ways to look at dissolved materials:
•load or loading [mg/sec or g/day or kg/yr]
can standardize loading by area:
yield [e.g. mg/sec/sq mile or g/day/acre or kg/yr/km2]
•concentration [mg/liter]
River Ecosystems(3):river chemistry
mass balance in a channel segment
dominated by input and output
•retention decreases with increasing velocity and decreasing biological activity
•longitudinally, incremental uptake/deposition leads to an assimilative capacity for consumable inputs
•by a combination of assimilation and dilution abnormally high inputs can be processed longitudinally
nutrient cycling becomes nutrient spiraling
Spiraling length
Sb Sw
River Ecosystems(3):river chemistry
dissolved material load
•constituents reflect hydrologic source and history of material contacts
• concentrations highly variable across landscape (spatial) as well as over time
Concentration
[C] = L / Q
[C] = a Q b-1
VdC/dt = QCin – QCout +/- VrC
Mass/Volume Mass flux (load)/ water flux (Q)
Mass balance
For a Completely
Mixed Flow reactor
material transport in rivers: load
Q
d
d
flow  transport
three categories of material [load]
•dissolved (chemistry)
•suspended
•bed
All forms of load are highly variable over time (flow effects)
b >1
L=aQb
L
b< 1
Where a and b are constants
b<< 1
Point Source (PS) and non-Point Source (NPS) loading
Q
•PS loads relatively constant (b<<1, concentration strongly subject to dilution)
•NPS loads usually increases with increasing runoff: note options
Load (quantity/time)
Typical non-point source
hysteresis
Typical point source
Q
Concentration (quantity/vol)
Typical non-point source
Typical point source
Q
Sol. Reactive Phosphate (ppm)
1
2
1
3
2
3
Nitrate+Nitrite (ppm)
Primary productivity of Aquatic ecosystems
Monod’s model
A basic model for enzyme mediated reaction rates. Common used
to describe the relationship between concentrations of a limiting
input and the resulting rate of photosynthesis.
growth or uptake rate = (S * Max) / (S+K)
S=input concentration; Max= maximum rate; K=1/2
saturation constant
Primary productivity of Aquatic ecosystems
Monod’s model
A basic model for enzyme mediated reaction rates. Common used
to describe the relationship between concentrations of a limiting
input and the resulting rate of photosynthesis.
growth or uptake rate = (S * Max) / (S+K)
S=input concentration; Max= maximum rate; K=1/2 saturation
constant
Max
photosynthetic
rate
1/2 max
concentration of limiting input [S]
K value
Monod’s model
Max
photosynthetic
rate
1/2 max
concentration of limiting input [S]
K value
Ecological implications:
photosynthesis responds in a non-linear fashion to changes in
all essential inputs
Monod’s model
Max
photosynthetic
rate
1/2 max
concentration of limiting input [S]
K value
Ecological implications:
photosynthesis responds in a non-linear fashion to changes in
all essential inputs
small changes in rare inputs can induce large responses,
but large changes in common inputs can have relatively small
consequences
Some typical uptake constants for phosphate
taxon
division
K (g l-1 P)
Cyclotella nana
Thalassiosira fluviatilis
Scenedesmus sp.
Psudomonas aeruginosa
bacillariophyceae
bacillariophyceae
chlorophyceae
cyanophyta
0.6
1.7
19
12.2
Physiological richness
Max (-15 g
per m-2cell
surface
day -1)
2.0
7.3
30
18
Liebig’s Law of the minimum
yield or growth of an organisms is determined by the abundance of
that substance which, in relationship to the needs of the organism, is
least abundant in the environment [i.e.,at a minimum]
Liebig’s Law of the minimum
TABLE: Proportions of Essential Elements for Growth in Living Tissues of Freshwater Plants
(Requirements), in the Mean World River Water (Supply), and the Approximate Ratio of
Concentrations Required to Those Available
ELEMENT
Oxygen
Hydrogen
Carbon
Silicon
Nitrogen
Calcium
Potassium
Phosphorus
Magnesium
Sulfur
Chlorine
Sodium
Iron
Boron
Manganese
Zinc
Copper
Molybdenum
Cobalt
AVERAGE PLANT CONTENT
/REQUIREMENT (% by
weight)
80.5
9.7
6.5
1.3
0.7
0.4
0.3
0.08
0.07
0.06
0.06
0.04
0.02
0.001
0.0007
0.0003
0.0001
0.00005
0.000002
AVERAGE SUPPLY IN
SURFACE WATERS
(% by weight)
89
11
0.0012
0 .00065
0.000023
0.0015
0.00023
0.000001
0.0004
0.0004
0.0008
0.0006
0.00007
0.00001
0.0000015
0.000001
0.000001
0.0000003
0.000000005
RATIO of NEED to SUPPLY
[RELATIVE DEMAND]
1
1
5000
2000
30,000
<1000
1300
80,000
<1000
<1000
<1000
< 1000
<1000
<1000
<1000
< 1000
<1000
<1000
<1000
After Vallentyne, J.R.: The Algal Bowl--Lakes and Man. Miscellaneous Special Publication 22, Ottawa,
Dept. of the Environment, 1974
Liebig’s Law of the minimum
ELEMENT
Oxygen
Hydrogen
Carbon
Silicon
Nitrogen
Calcium
Potassium
Phosphorus
Magnesium
Sulfur
Chlorine
Sodium
Iron
Boron
Manganese
Zinc
Copper
Molybdenum
Cobalt
AVERAGE PLANT CONTENT
/REQUIREMENT (% by
weight)
80.5
9.7
6.5
1.3
0.7
0.4
0.3
0.08
0.07
0.06
0.06
0.04
0.02
0.001
0.0007
0.0003
0.0001
0.00005
0.000002
AVERAGE SUPPLY IN
SURFACE WATERS
(% by weight)
89
11
0.0012
0 .00065
0.000023
0.0015
0.00023
0.000001
0.0004
0.0004
0.0008
0.0006
0.00007
0.00001
0.0000015
0.000001
0.000001
0.0000003
0.000000005
RATIO of NEED to SUPPLY
[RELATIVE DEMAND]
1
1
5000
2000
30,000
<1000
1300
80,000
<1000
<1000
<1000
< 1000
<1000
<1000
<1000
< 1000
<1000
<1000
<1000
there is always some input which is least abundant and limits primary production
•limiting factors may change over time and across space
•co-limitations are important
essential input
indicator
inorganic carbon
Phosphorus
Nitrogen
Micro-nutrients
radiant energy
<40 ppm total alkalinity
<10 ppb TRP or N:P>>16
<40 ppb NO3 or N:P<<16
Poor growth with high CNP
high turbidity/ gilvin/ depth
the 1% rule
examples of systems with
photosynthetic rate
limited by this input
soft water lakes
eastern and midwestern rivers, most N.A. lakes
southwest and northwest rivers, oceans
Some tropical streams
Reservoirs, turbid rivers
[Si] : [TP] <160
RCC: does it work?
Riparian
condition
Veloc
allocthonous
[terrestrial
leaves, wood, DOC]
autochthonous
[algae+ macrophytes]
Nutrients
Light
DETRITAL
POOL
Ldecomposers
Bacteria & fungi
L
L
L2
grazers
shredders
collector-gathers
filter-feeders
invert
predators
invertivorous fish
/birds
L3
L4
piscivorous fish
L5
piscivorous birds
/mammals
INSECT
PREDATORS?
FISH?
Grazer
Invert.
biomass
FLOODS?
DROUGHTS?
DISEASE?
Algal
Biomass
POLLUTION?
Nutrients
Top-down community controls and high disturbance regimes
can obscure
simple responses to nutrient inputs
Biomass [mg d.w. m-2]
Drift
Bedrock
400000
300000
200000
400000
300000
200000
100000
100000
50000
40000
30000
20000
50000
40000
30000
20000
10000
10000
5000
4000
3000
2000
5000
4000
3000
2000
Periphyton
1000
1000
500
400
300
200
5
Invertebrates
6
7
8
9 10
20
SRP [ug/l -1]
30
40
500
400
300
200
4
5
6
7
8
9 10
20
SRP [ug/l -1]
30
40
Figure 3. Hypothetical (A) and fitted (B) path diagram illustrating results of CSA of the effects of hydrologic disturbance
on benthic algal and primary consumer biomass in Knobs and glacial drift streams. Rectangles are observed exogenous and
endogenous variables, ovals are unmeasured, latent variables, and small circles are error variances. Numbers give the
magnitude of direct effects, and numbers in italics are squared multiple correlations. Bold indicates significant effects at p <
0.05 based on bootstrapped
error estimates (n = 133).
-.20
.37
(B)
-.24
Inorganic
Nitrogen
Phosphorus
Bankfull
Power
.56
.24
.43
Frequency of
Substrate Movement
Nutrients
e10
.87
High Flow
Di sturbance
.74
Q90 &
Summer Temp
.27
.87
.45
.05
Algal Biomass
Benthic Chlorophyll a
.17
1.00
Low Flow
Di sturbance
- .52
.55
- .92
- .48
- .51
.37
Filter Feeder
Biomass
e3
- .12
Grazer
Biomass
e4
.59
.45
.51
.14
time
Oxygen consumed
Biological Oxyen Demand
BOD ppm
Oxygen ppm