geologic history of the red river basin · the first is a measure of the amount ... • other terms...

Water Chemistry

Water 101

I. Introduction

A. Water is not pure• Many different kinds of chemicals

dissolved in it• Ions, organic chemicals, organic matter ,

particulate matter, and gases can all be in water

• Some are considered pollutants, others are natural components

II. Basic Water Quality Measurements• DO – dissolved oxygen• pH• Temperature• Specific conductivity• Turbidity

II. Basic Water Quality MeasurementsA. DO – stands for dissolved oxygen. • The amount of oxygen dissolved in the

water• Animals and protists require oxygen to live• The amount of oxygen dissolved in water

varies due to several factors

II. Basic Water Quality Measurements• They include:

– 1. Water temperature •More oxygen can be dissolved in cool water than in warm water.

•For example, at 20o C (68 F) water can hold up to 9.2 mg/l, at 25o C (77 F) water can only hold 8.4 mg/l

Graph showing Oxygen concentration dependence on temperature

From: http://www.lenntech.com/why_the_oxygen_dissolved_is_important.htm

II. Basic Water Quality Measurements

– 2. Biological activities that use oxygen (respiration, organic breakdown, etc.)•Decomposition of organic material requires oxygen

•Decomposition tends to occur in the bottom sediments of aquatic systems


– 3. Biological activities that produce oxygen (photosynthesis)•Since sunlight is greatest at the surface, photosynthesis tends to add more oxygen to the upper layers

– 4. Physical activities that add oxygen (turbulent water)•0nce again, this tends to add oxygen to the upper surface of water

II. Basic Water Quality Measurements• Dissolved Oxygen is usually measured in

one of two ways – 1. The first is a measure of the amount

of oxygen per liter of water and is measured in the unit mg/l•mg/l stands for milligrams per liter •A DO of 10 mg/l means there are 10 milligrams of oxygen dissolved in 1 liter of water


– 2. The second way to measure oxygen is called % saturation •Saturation is the point at which water is holding all the oxygen it can hold

•% saturation compares the amount actually in the water with the amount at the point of saturation


•Example: at 250C water can hold 9.2 mg/l of oxygen at saturation–Lets say you measure a stream at 250C and the DO is 8.3 mg/l

–The % saturation would be calculated by taking 8.3 /9.2 which would equal 90%

–So the % saturation DO = 90%


– It is actually possible to have a super saturated condition•In waters that are highly oxygenated, there can be % saturation greater than 100%

II. Basic Water Quality Measurements• A relationship seen in many aquatic

ecosystems is the high amount of DO during the daylight hours and then a precipitous drop during the night.

• DO levels around 7 – 9 mg/l are considered optimal for fish

• A DO below 4 usually can not support fish.

II. Basic Water Quality MeasurementsB. Temperature – Temperature varies

during the day in aquatic ecosystems. • Has a great affect on the DO in water • Aquatic organisms have a particular

tolerance range for temperature, – some prefer cool waters, others can

survive in fairly warm waters.

II. Basic Water Quality Measurements• Cooling and Evaporation

– Water cools as it evaporates– The physical process of water molecules

changing from liquid to gas absorbs energy (heat)

– This cools the surface the water evaporates from

II. Basic Water Quality MeasurementsC. Specific conductivity – This is a measure

of the ability of the water to conduct an electrical current.

• It is actually a measure of the ion concentrations in the water

• high ion concentrations have a higher conductivity.

II. Basic Water Quality Measurements• Water usually has several types of

dissolved ions (salts)• Common ions include calcium (Ca++),

magnesium (Mg++), and bicarbonate (HCO3

-)

II. Basic Water Quality Measurements• Other ions such as phosphates and

nitrates are also a part of specific conductivity– Important plant and algae nutrients – Specific conductivity can give an

estimate of the primary productivity of a water body

II. Basic Water Quality Measurements• Other terms used in relation to dissolved ions

– Total dissolved solids (TDS) – all organic and inorganic salts dissolved in the water•High TDS means high specific conductivity

– Hardness – relates to the amount of calcium and magnesium dissolved in the water

II. Basic Water Quality Measurements• Salinity - measure of the total

concentration of salts (mg per liter) dissolved in water

II. Basic Water Quality MeasurementsD. pH – This is the measurement of the

acidity or alkalinity of the river or stream • Depends on a variety of factors, but

especially the soil characteristics of the watershed – Areas with high concentrations of

calcium carbonate will tend to have a pH above neutral (7).

II. Basic Water Quality Measurements• In North Dakota, most river and streams

are slightly alkaline and have a pH between 7.5 and 9

• Values between 5 and 9 are considered safe for most aquatic life.

II. Basic Water Quality MeasurementsE. Turbidity – This is the measurement of

how clear the water is. • The more suspended solids there are in

the water column, the murkier it is • Examples of suspended solids that can

cause high turbidity are soil particles, algae, organic detritus, and sewage discharge.

II. Basic Water Quality Measurements• Rivers in the North Dakota tend to have a

fairly high turbidity because of a high amount of algae, or phytoplankton, in the water.

• Total Suspended Solids (TSS) –measurement of the solids suspended in the water column

II. Basic Water Quality Measurements• Do not confuse dissolved solids with

suspended solids. • Dissolved solids do not have a major

impact on turbidity, • You can have very clear water that has a

high TDS and specific conductivity

III. Measuring Water Quality

A. Probes – electronic components for measuring certain parameters

• Probes are an expensive, but accurate ways of measuring water quality parameters

• Several companies make multiprobe sondes, a device that can measure many different parameters at once


• Multiprobe sondes take quick measurements and record them within the instrument– You can later download them into a

computer for analysis• Multiprobes can also be used for long term

monitoring– This application is called data logging


– The probe is placed in a river and left for a designated period of time

– The probe will measure and record parameters at a set interval

• Most water resource professionals use multiprobes for measuring the water quality parameters discussed earlier

A Hydrolab multiprobe sonde

Moon Lake Vertical Profile, 8-28-12

Depth meters pH DO%

DO mg/l Temp °C

SpCµS/cm

Turbidity NTU

0 8.9 120.3 10.45 21.92 4,181 12.81 8.91 123 10.64 21.92 4,183 9.132 8.9 117 10.2 21.48 4,180 9.973 8.9 114.5 10.01 21.45 4,176 11.24 8.9 113.7 9.94 21.44 4,176 5.815 8.89 111.7 9.77 21.37 4,176 7.566 8.84 95.5 8.61 21.16 4,170 11.47 8.8 69.5 6.35 20.16 4,163 5.478 8.74 38.2 3.75 19.62 4,144 3.749 8.66 14.5 1.48 18.33 4,142 6.9110 8.47 5.2 0.51 16.13 4,113 4.7811 8.41 3.4 0.35 15.01 4,071 4.1112 8.4 3 0.3 14.63 4,067 4.513 8.36 3 0.3 14.1 4,073 2.4614 8.32 2.9 0.3 13.86 4,070 2.5615 8.29 3.2 0.32 13.75 4,072 na

0

2

4

6

8

10

12

14

1612 14 16 18 20 22 24

Depth (M)

Temp in C

Temperature

Temperature

0

2

4

6

8

10

12

14

16

0 2 4 6 8 10 12

Depth (m)

Dissolved Oxygen mg/l

DO

DO

III. Nutrients

A. Nutrients• Phosphorus and nitrogen are considered

the most important nutrients in aquatic system

• High nutrient loads can lead to eutrophication

• Phosphorus is considered to be the main limiting nutrient in fresh water bodies

Lake Winnipeg algal bloom

https://savelakewinnipeg.org

• The discovery that phosphorus was the liming nutrient in aquatic systems was fairly recent

• Most likely candidates were nitrogen, carbon dioxide, and phosphorus

• Chemical companies favored CO2 as being the limiting nutrient because their products did not add it to water

III. Nutrients

• Several lines of evidence led to the idea of phosphorus being the main limiting nutrient in aquatic systems– Carbon concentrations in Lake Erie have

stayed the same the last 100 years•Algae blooms have increased dramatically as phosphate levels increased

III. Nutrients

• Both CO2 and nitrogen are more abundant in aquatic ecosystems and are readily available from the atmosphere

• In many lakes, comparison of PP and nutrient concentrations shows a strong correlation between PP and phosphorus

• In a whole –lake manipulation it was shown that the addition of phosphorus caused extensive algae blooms

III. Nutrients

IV. Nutrient loads

A. Excess nutrients are often considered detrimental to aquatic ecosystems

• They can lead to eutrophication of a water body

• They may be detrimental to certain species over long exposures

IV. Nutrient loads

B. Presence of nutrients in the water are dependent on several factors

• 1. Urban discharges – Studies show slightly higher levels of

nutrients in the Red River above the Fargo Moorhead area

– Ammonia and Phosphorus were the two main nutrients

IV. Nutrient loads

• 2. Agricultural land use– North Dakota is an agricultural state

•Fertilizers often end up in the water•This runoff is an important part of the nutrient load of our rivers and streams

IV. Nutrient loads

• 3. The geology of the area– Area with a shallow ground water

aquifer may lead to faster leeching of nutrients into the ground water

– May have higher pesticide and nitrate levels since they are able to infiltrate faster

IV. Nutrient loads

C. TMDL - Total Maximum Daily Load• TMDL is the maximum amount of a

pollutant that a waterbody can receive and still meet water quality standards

• These standards are usually set by states or tribes

V. Measuring Nutrients

A. Multiprobe sondes• Several sonde manufacturers have

developed probes for to measure directly or indirectly nutrients in the water

• Ex. - Nitrates, ammonium, chlorophyll, cyanobacteria, BOD, etc.

• Expensive and fairly high maintenance


B. Chemistry Kits• Kits that use chemical reactions that result

in a color change• Hach and LaMotte are best known for

making kits used in educational settings for Nitrates and Phosphates

• Not accurate or precise enough for regulatory purposes


C. Chemical analysis• For nutrients and many other substances,

such as heavy metals and pesticides, analysis is best done by a chemistry lab

• Water is collected and then shipped to the lab

• There are certified labs that can do this analysis

Date Time Latitude LongitudeWeather Condition

s

Max Depth (ft.)

Water Temp

7/19/2016

8:00 AM 46.62571 -103.15684 Mostly cloudy

1.7 18.95

Sp. Cond. pH %DO DO Comments

3418.7 9.9 7.7 0.71 Little to no flow. Heavily vegetated (submergent). Mucky bottom

Time Collected Analyte Result Units Result Comment

8:00 Na (ICP) 652 mg/L8:00 Mg (ICP) 70.5 mg/L8:00 K (ICP) 9.4 mg/L8:00 Ca (ICP) 34 mg/L8:00 Mn (ICP) 0.083 mg/L8:00 Fe (ICP) 0.592 mg/L8:00 Cl 15.1 mg/L8:00 pH 9.888:00 CO3 93 mg/L8:00 HCO3 100 mg/L8:00 OH < 1 mg/L8:00 Alk. Total 236 mg/L8:00 Cond 3370 umhos/cm8:00 Temp (C) 12 Deg C8:00 Delivery H 78 hrs8:00 SO4 1510 mg/L8:00 Hardness 375 mg/L8:00 Cation Sum 36.11 me/L8:00 Anion Sum 36.68 me/L8:00 Difference -0.567 me/L8:00 % Diff -0.78 %8:00 Na % 78.5 %8:00 SAR 14.68:00 TDS (C) 2430 mg/L8:00 Rerun Ion Ion Balance OK Ion Balance OK8:00 C/A v Cond Cat/An/Cond OK Cat/An/Cond OK8:00 Blank Chk No Blank Check No Blank Check8:00 XI-Dig-H2O Prepared8:00 ICP inst Completed

LMG16-04 Adobe Wall Creek

VI. Heavy Metals

A. Heavy metals include a variety of elements such as Cadmium, Chromium, Mercury, Selenium, Zinc, and Arsenic

• They can be found in the sediment of rivers and streams

• Most of the levels measured in North Dakota are due to natural sources

VI. Heavy Metals

• One exception to this may be Mercury– It is often released into the atmosphere

by industrial processes, waste incineration, and coal burning

– Some large game fish taken in the Red River Basin have had higher than 1 ppm of mercury in their tissues

– This is the US Food and Drug standard

VI. Other Chemicals of concern

A. Pesticides• Since North Dakota is dependent on

agriculture, herbicides can be found at detectable levels in the our waters

• However, none exceeded standards for drinking water

• The most common detected herbicide is atrazine


B. Polychlorinated Biphenyls – PCBs• Industrial compounds that have been

banned in the US because of their toxicity and persistence in the environment

• Commonly found in low concentrations in fish samples taken from the basin

• Concentrations were some of the lowest in the NAWQA study, however


C. Polycyclic aromatic hydrocarbons – PAHs• PAHs can occur naturally, but are also

released by the burning of fossil fuelsD. Volatile organic compounds – VOCs• These include industrial solvents and

petroleum products

geologic history of the red river basin · the first is a measure of the amount ... • other terms...

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