By: Drew Zagala
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Test the nitrate, phosphorus, and pH of the Iris Pond and
Green Heron Pond. Compare results to previous water quality
tests to understand changes in nutrient levels and pH of the
Arboretum’s bodies of water.
Additionally, test the nitrate, phosphorus, and pH of Tamarack
Lake to determine its water quality and create a baseline for
future monitoring.
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High nutrient levels in a water system can severely change its
ecosystem
 Increases algae concentrations and algal blooms
 Decrease levels of dissolved oxygen
 Reduces biodiversity
 Reduces aesthetic appeal
Credit: Sevenhillslake.com
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Additionally, Green Heron supplies irrigation for the
Arboretum grounds
 High levels of nutrients can encourage weeds
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Nitrogen
 Applied usually as Nitrate (NO3-), Urea(CH4N2O), and Ammonia (NH3)
 Highly water soluble chemicals
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Prone to erosion by rain events, over-watering, and groundwater runoff
Source: United States Geologic Survey. Copyright 2003
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Phosphorus
 Applied as Phosphorus penta-oxide (P2O5)
▪ Not water soluble, but binds to soil particles
 Prone to erosion as soil erodes from an area – rain events, over-watering, high slope gradients
Source: The Caribbean Environment Program. Copyright 2014
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pH tends to determine the type of plants/animals that can live
in a body of water
 Nutrient availability for plants
 Solubility of heavy metals or other toxins
Source: Fundamentals of Environmental Measurements. Copyright 2016
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Minnesota Pollution Control Agency
 Calculated average nutrient and pH levels for various ecosystems in
Minnesota.
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North Central Hardwood Forests
Field pH
Nitrate
Total Phosphorus
8.6-8.8
10 ppb
23-50 ppb
Critical Eutrophic Level – 85 ppb phosphorus
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“Minnesota Lake Quality Assessment Report 3rd Edition”
Arboretum Water Body Nitrate Levels (ppb)
30
Nitrate (ppb)
25
25.8
20
20.4
20
20
15
Iris Pond
10
Ecosystem Average
10 ppb
5
0
2011
2012
2013
Year
2016
Arboretum Water Body Phosphorus Levels (ppb)
350
Phosphorus (ppb)
300
Shoreline buffer installed
286
250
200
150
Iris Pond
85
100
50
Critical Eutrophic Level
17
36
52
0
2008
2011
2012
Year
2013
2016
85ppb
Ecosystem
Average
23-50 ppb
Arboretum Water Body pH
8.5
8
pH
7.5
8.1
8
7.7
7.6
7
6.5
Iris Pond
6
5.5
5
2011
2012
2013
Year
2016
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2016 Data was collected for Green Heron Pond..
Green Heron Pond
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Nitrate
Phosphorus
pH
<20 ppb
1440 ppb
7.04
Unable to sample from “cleaner” center of lake
 High levels of decomposing matter
▪ Bog would normally filter out high levels of phosphorus from entering greater
lake area
Arboretum Water Body Nitrate Levels (ppb)
140
128
Nitrate (ppb)
120
100
80
60
Green Heron
40
20.5
20
Ecosystem Average
10 ppb
0
2011
2012
Year
Arboretum Water Body Phosphorus Levels (ppb)
45
Critical Eutrophic Level
85ppb
41
Phosphorus (ppb)
40
Ecosystem
Average
23-50 ppb
35
30
27
25
24
20
Green Heron
15
10
5
0
2008
2011
Year
2012
Arboretum Water Body pH
9
8.5
8
8.7
8
pH
7.5
7
6.5
Green Heron
6
5.5
5
2011
2012
Year
Horticulture
Research
Center
Lake
Minnewashta
Arboretum Water Body Nitrate Levels (ppb)
25
Nitrate (ppb)
20
20
15
Ecosystem Average
10 ppb
10
Tamarack Lake
5
0
2016
Year
Arboretum Water Body Phosphorus Levels (ppb)Critical Eutrophic Level
70
65
85ppb
Phosphorus (ppb)
60
50
Ecosystem Average
23-50 ppb
40
30
Tamarack Lake
20
10
0
2016
Year
Arboretum Water Body pH
9
8.5
8.5
8
pH
7.5
7
6.5
Tamarack Lake
6
5.5
5
2016
Year
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Iris Pond
 Healthy!
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Green Heron Pond
 Relatively healthy!
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Tamarack Lake
 Healthy!
Good levels of dissolved oxygen
Low levels of algae and algal blooms
Support diverse biota
Safe levels of dissolved oxygen
Moderate algae and algal blooms
Support biota
Good levels of dissolved oxygen
Low levels of algae and algal blooms
Support diverse biota
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Reduce the use of liquid fertilizers
 Do not over-apply!
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Clean up grass clippings and pulled weeds
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Remove animal droppings
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And….
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Designed to catch and store eroding nutrients and soil before they can pollute
bodies of water.
What are desirable traits for the plants in a Shoreline Buffer?
 Deep root systems -Tolerate high levels of nutrients
 Tolerate high/variable levels of water
 High biodiversity, preferably perennial
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Phosphorus erosion diagram: http://agrihelper.blogspot.com/2016/06/types-of-erosion-splashsheetrill-and.html
Nitrogen erosion diagram: http://pubs.usgs.gov/fs/2003/fs091-03/
pH diagram: http://www.fondriest.com/environmental-measurements/parameters/water-quality/ph/
Minnesota Pollution Control Ecosystem Averages: https://www.pca.state.mn.us/quick-links/eda-guide-typical-minnesota-water-qualityconditions
Previous Water Quality data collected by past interns: Dan Miller.
Water Quality Tests conducted by Tri-City/William Lloyd Analytical Laboratories
Critical Eutrophic Levels from: Heiskary, Steven A., and C. Bruce Wilson. Minnesota lake water quality assessment report: Developing nutrient
criteria. Water Assessment & Environmental Information Section, Environmental Analysis & Outcomes Division, Minnesota Pollution Control
Agency, 2005.
Eutrophic Lake Image: http://sevenhillslake.com/technical.html