411 2003Chemistry Lecture Slides
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)
General conditions affecting River Chemistry
River Ecosystems(3):river chemistry
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]
anions cations Non- ionic CO3
= carbonate Na+ sodium N2 nitrogen
HCO3- bicarbonate Ca++ calcium O2 oxygen
Cl- chloride Mg++ magnesium CO2 Carbon dioxide
SO4= suphate K+ pottasium DOC Diss org carbon
OH- hydroxide Fe++ iron
Principal dissolved material in freshwater ecosystems
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)
6 HOH + 6 CO2 <=>C6H12O6 + 6 O2
stoichiometrically useful but too simplified
Photosynthesis and macro-nutrients
a more realistic (but also very simplified) equation for the productionof 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 weightsNecessary Inputs atomic wt mg per mole algae wt relative to P
CO2-C ~12 1272 ~41NO3
-N ~14 224 ~7PO4
=-P ~31 31 1Energy
parameter low medium high Conductivity s 5-80 90-800 1000+ TDS ppm <20 40-400 500+ Alkalinity ppm <40 50-150 200+ Ammonia ppb Nitrite ppb Nitrate ppb
<5 <5 <80
20-80 5-20 100-800
100+ 30+ 1000+
SRP (TRP) ppb TP ppb
<5 <10
10-20 15-30
30+ 50+
How much is a lot?
0 . 0 0
0 . 0 4
0 . 0 8
0 . 1 2
0 . 1 6
7 5 1 5 0 2 2 5
O S O HM_ _
E_ _
Alkalin ity (p pm as CaCO3)
SolubleReactivePhos-phate(ppm)
10 ppb
50 ppb
100
Variable Count Mean StdDev pH 131 7.5 0.5 Alkalinity 255 166 62 Conductivity 1130 416 198 NO2 + NO3 (ppm) 947 1.073 2.521 Ammonia (ppm) 833 0.083 0.162 SRP (ppm) 634 0.022 0.031 Total P (ppm) 774 0.059 0.080 Gilvin 242 0.024 0.020 Turbidity (NTU) 247 15.980 15.530
What is average?
parameter continental rain
Maine river
Michigan river
Seawater
Na+ mg/l
0.20 0.90 15.00 11000.00 K+
mg/l 0.15 0.30 3.60 399.00
NH4+
mg/l 0.10 0.08 0.04 0.04
Mg++ mg/l
0.05 0.40 7.70 1290.00 Ca++
mg/l 0.10 1.7 33.00 412.00
Cl- mg/l 0.20 0.55 19.00 19354.00
NO3-N mg/l
0.40 0.06 0.50 5.00 SO4
= mg/l 1.00 6.33 69.00 2712.00
CO3=
mg/l <1.0 7.7 100.0 120.00
PO43+-P
mg/l 0.010 0.010 0.030 0.025
PH -log10 [H+] 4.5 4.9 7 8.1
Cond. s 6 36 496 70000+ TDS mg/l 3 18 249 35292
Examples of some chemically distinct waters
…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
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
mass balance in a channel segment
River Ecosystems(3):river chemistry
Spiraling length
Sb Sw
dissolved material load•constituents reflect hydrologic source and history of material contacts• concentrations highly variable across landscape (spatial) as well as over time
Concentration
Mass/Volume Mass flux (load)/ water flux (Q)
[C] = L / Q
[C] = a Q b-1
River Ecosystems(3):river chemistry
VdC/dt = QCin – QCout +/- VrC
Mass balanceFor a CompletelyMixed Flow reactor
material transport in rivers: load
flow transportthree categories of material [load]
•dissolved (chemistry)•suspended•bed
L = a Q b
Where a and b are constants
b=1b >1
b< 1
b<< 1
Q
L
All forms of load are highly variable over time (flow effects)
Qd
d
Point Source (PS) and non-Point Source (NPS) loading
•PS loads relatively constant (b<<1, concentration strongly subject to dilution)•NPS loads usually increases with increasing runoff: note options
Q
Loa
d (q
uant
ity/
tim
e)Typical non-point source
Typical point source
hysteresis
Q
Con
cent
rati
on (
quan
tity
/vol
)
Typical non-point source
Typical point source
Nitrate+Nitrite (ppm)
Sol. Reactive Phosphate (ppm)
1 2 3
3
12
Primary productivity of Aquatic ecosystems
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
Monod’s model
Primary productivity of Aquatic ecosystems
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
Monod’s model
Max
concentration of limiting input [S]
photosyntheticrate
1/2 max
K value
Ecological implications:photosynthesis responds in a non-linear fashion to changes in all essential inputs
Max
concentration of limiting input [S]
photosyntheticrate
1/2 max
K value
Monod’s model
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
Max
concentration of limiting input [S]
photosyntheticrate
1/2 max
K value
Monod’s model
Some typical uptake constants for phosphate taxon division K (g l-1 P) Max (-15 g
per m-2cell
surface day -1) Cyclotella nana bacillariophyceae 0.6 2.0 Thalassiosira fluviatilis bacillariophyceae 1.7 7.3 Scenedesmus sp. chlorophyceae 19 30 Psudomonas aeruginosa
cyanophyta 12.2 18
Physiological richness
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
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 ofConcentrations Required to Those Available
ELEMENT AVERAGE PLANT CONTENT/REQUIREMENT (% by
weight)
AVERAGE SUPPLY INSURFACE WATERS
(% by weight)
RATIO of NEED to SUPPLY[RELATIVE DEMAND]
Oxygen 80.5 89 1Hydrogen 9.7 11 1Carbon 6.5 0.0012 5000Silicon 1.3 0 .00065 2000Nitrogen 0.7 0.000023 30,000Calcium 0.4 0.0015 <1000Potassium 0.3 0.00023 1300Phosphorus 0.08 0.000001 80,000Magnesium 0.07 0.0004 <1000Sulfur 0.06 0.0004 <1000Chlorine 0.06 0.0008 <1000Sodium 0.04 0.0006 < 1000Iron 0.02 0.00007 <1000Boron 0.001 0.00001 <1000Manganese 0.0007 0.0000015 <1000Zinc 0.0003 0.000001 < 1000Copper 0.0001 0.000001 <1000Molybdenum 0.00005 0.0000003 <1000Cobalt 0.000002 0.000000005 <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
there is always some input which is least abundant and limits primary production
ELEMENT AVERAGE PLANT CONTENT/REQUIREMENT (% by
weight)
AVERAGE SUPPLY INSURFACE WATERS
(% by weight)
RATIO of NEED to SUPPLY[RELATIVE DEMAND]
Oxygen 80.5 89 1Hydrogen 9.7 11 1Carbon 6.5 0.0012 5000Silicon 1.3 0 .00065 2000Nitrogen 0.7 0.000023 30,000Calcium 0.4 0.0015 <1000Potassium 0.3 0.00023 1300Phosphorus 0.08 0.000001 80,000Magnesium 0.07 0.0004 <1000Sulfur 0.06 0.0004 <1000Chlorine 0.06 0.0008 <1000Sodium 0.04 0.0006 < 1000Iron 0.02 0.00007 <1000Boron 0.001 0.00001 <1000Manganese 0.0007 0.0000015 <1000Zinc 0.0003 0.000001 < 1000Copper 0.0001 0.000001 <1000Molybdenum 0.00005 0.0000003 <1000Cobalt 0.000002 0.000000005 <1000
essential input indicator examples of systems withphotosynthetic ratelimited by this input
inorganic carbon <40 ppm total alkalinity soft water lakesPhosphorus <10 ppb TRP or N:P>>16 eastern and midwestern rivers, most N.A. lakesNitrogen <40 ppb NO3 or N:P<<16 southwest and northwest rivers, oceansMicro-nutrients Poor growth with high CNP Some tropical streamsradiant energy high turbidity/ gilvin/ depth
the 1% ruleReservoirs, turbid rivers
•limiting factors may change over time and across space•co-limitations are important
[Si] : [TP] <160
RCC: does it work?
decomposers
allocthonous
autochthonous
DETRITALPOOL
[algae+ macrophytes]
invertivorous fish /birds
grazersshredderscollector-gathersfilter-feeders
invertpredators
[terrestrial
leaves, wood, DOC]
piscivorous fish
piscivorous birds /mammals
Bacteria & fungi
Ripariancondition
Veloc
Light
Nutrients
Invert.biomass
Algal Biomass
Nutrients
Grazerbiomass
Algal Biomass
Nutrients
FISH?INSECTPREDATORS?
FLOODS?
DROUGHTS? POLLUTION?
DISEASE?
Top-down community controls and high disturbance regimes can obscure
simple responses to nutrient inputs
SRP [ug/l -1] SRP [ug/l -1]
4030201098765
400000300000200000
100000
50000400003000020000
10000
5000400030002000
1000
500400300200
40302010987654
400000300000200000
100000
50000400003000020000
10000
5000400030002000
1000
500400300200
Bio
mas
s [m
g d.
w. m
-2]
Periphyton
Invertebrates
Drift Bedrock
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).
Nutrients
High FlowDisturbance
Low FlowDisturbance
PhosphorusInorganicNitrogen
Frequency ofSubstrate Movement
.14
Algal BiomassBenthic Chlorophyll a
Q90 &Summer Temp
.51
GrazerBiomass
.59
Filter FeederBiomass
e10
.87 .27
.37
e3
e4
BankfullPower
.45
.17
.24
- .12
-.20
.87
-.24
- .92
.05
.43
.45
.55
- .52
- .48 - .51
.56
.74
.37
.14
.51
.59
.87 .27
.37
e3
e4
.45
1.00
.24
- .12
-.20
-.24
- .92
.05
.43
.45
.55
- .52
- .48 - .51
.56
.74
.37
(B)
Nutrients
High FlowDisturbance
Low FlowDisturbance
PhosphorusInorganicNitrogen
Frequency ofSubstrate Movement
.14
Algal BiomassBenthic Chlorophyll a
Q90 &Summer Temp
.51
GrazerBiomass
.59
Filter FeederBiomass
e10
.87 .27
.37
e3
e4
BankfullPower
.45
.17
.24
- .12
-.20
.87
-.24
- .92
.05
.43
.45
.55
- .52
- .48 - .51
.56
.74
.37
.14
.51
.59
.87 .27
.37
e3
e4
.45
1.00
.24
- .12
-.20
-.24
- .92
.05
.43
.45
.55
- .52
- .48 - .51
.56
.74
.37
(B)
Oxy
gen
cons
umed
Bio
logi
cal O
xyen
Dem
and
BO
D p
pm
Oxy
gen
ppm
time