Environmental Chem Ch 2
Why is water hardness important?
- Affects alkalinity (has the ability to produce one of the buffering capacity ions) - Water use in public settings (hard water affects soaping ability and causes scale build up)
What are two reasons pH is important?
- Affects many chemical and biological processes (abiotic and biotic) - Alters states/forms of many chemical species, which can affect the transportation and bioavailability (nutrients and pollutants)
What are the two ends of the scale of dissolve oxygen?
- Anoxic (no free O2) - Oxic (abundance of O2
Name four types of minerals that cause water hardness.
- CaCO3 - MgCO3 - CaSO4 - CaSO4 * 2 H2O
What drives the pH in unpolluted natural systems?
- Carbonic acid - Bicarbonate - Carbonate
What is the importance of TSS?
- Decreased photosynthesis - Suspended solids can interfere with biological processes, such as coating and blocking vision - Transports contaminants (pollutants)
In a redox reaction, what does reduction mean?
- Electrons are gained - Oxidizing agent
In a redox reaction, what does oxidation mean?
- Electrons are lost - Reducing agent
What are the three main species that need to be present for buffering capacity?
- HCO3- +. H+. -> H2CO3 - CO3^2- + H+. ->. HCO3- - OH- + H+ -> H2O
Why is dissolved oxygen important?
- Main player in many redox reactions - Dictates the types of organisms expected to be found in the system
What happens to the ORP Value, Chemical Environment, Chemical species behavior, and [O2] is the pE value decreases?
- ORP Value: becomes more negative - Chem Env: Reducing environment - Chem species behavior: Tendency to lose e- to new chem species introduced into the system - [O2]: Low; anoxic
What happens to the ORP Value, Chemical Environment, Chemical species behavior, and [O2] is the pE value increases?
- ORP Value: becomes more positive - Chem Env: Oxidizing environment - Chem species behavior: Tendency to gain e- from new chem species introduced into the system - [O2]: High; oxic
What are the three main sources of dissolved oxygen (DO)
- Primary producers (photosynthesis) - Atmosphere gas exchange - Turbulence (rate of movement, wind)
How do aquatic organisms impact the water chemistry?
- Primary producers dissolve oxygen - Microbes are responsible for the decomposition of organic matter and the main facilitators of redox reactions
What uses up dissolve oxygen in aquatic systems?
- Respiration (Carb/sugar + O2 -> CO2 + H2O) - Decomposition and biodegradation of organic matter (carbon based with H, O, P, N, S)
What is TSS measured with?
- Secchi disk - Turbidity meter (reported as NTUs)
What are the two types of hardness?
- Temporary - Permanent
Why is electron activity important?
- The redox reactions are facilitated by microbes, which decrease the O2 levels - Redox reactions can mobilize pollutants or contaminants - Redox reactions can convert compounds into more bio-available forms (nutirents)
What is pH measured with?
- Titration instrument - pH probe/meter
What is the importance of calculating Alkalinity?
- To determine the buffering capacity of a system (Its ability to resist changes in pH) - Alkalinity is an indicator of carbon (HCO3- and CO3^2-) which can be used by organisms
What is the importance of conductivity/salinity?
- Tolerance is a major driver of aquatic habitat availability - Creates stratification zones - Greater salinity results in lower dissolved oxygen
How is electron activity reported and measured?
- pE (-log (e- activity)) - ORP (oxidation reduction potential - Both measured with an electrode and reported as volts or millivolts
What are the four important properties of water discussed in class?
1. Good solvent 2. Transparent to light 3. Max density at 4 C 4. High heat capacity
What are 6 systems in limnology?
1. Lakes 2. Rivers 3. Streams 4. Reservoirs 5. Wetlands 6. Ground Water
What are the two importances of aquatic organisms discussed in class?
1. They heavily impact the aquatic chemistry 2. They are bioindicators
What are the 9 common water quality parameters?
1. pH 2. Alkalinity 3. Dissolved Oxygen (DO) 4. Suspended and dissolved solids 5. Hardness 6. Temperature 7. Electron Activity 8. Chlorophyll 9. Pathogens
What is the electron activity (redox reactions) parameter of water?
A measure of the tendency for an environment to receive or supply electrons
What is the result of the differing electronegativities in H2O?
A negative dipole, which makes water polar
What is a halocline?
A seperation in the water column due to salinity differences
What is H2O?
A small molecule with electronegativities between the O and H big enough that the electrons are not shared equally
What end of the DO scale is associated with aerobic organisms?
Abundance of oxygen in system (Oxic)
What hardness can also affect what other water parameter?
Alkalinity - As more biological water is produced, more CH2O is decomposed to form CO2, which is then used to produce more Ca^2+ which increases the hardness of the system
What is the effect of water being transparent to light?
Allows primary producers to survive and photosynthesize
How does temperature affect decomposition?
As temperature increases, decomposition increases - metabolic processes increase to a point, before killing organisms
How does temperature affect gas solubility?
As temperature increases, the gas solubility decreases
How does temperature affect the solute concentrations in a system?
As temperature increases, the solutes dissolve better
How are temperature and density of a system related?
As water approaches 4 C, the density increases and cold water sinks. If water temp goes below 4 C, then the density decreases (ice floats) - Creates a cycle/movement of nutrients going up and DO going down the water column
How is the alkalinity determined?
By titration - Reported as ppm CaCO3 or mg/L CaCO3
What is the chemical equation of the driving factors of hardness concentration?
CaCO3 + H2O + CO2 --> Ca^2+ + HCO3^-
In freshwater systems, what is the dominant cation in determining the hardness of the system?
Ca^2+ (calcium) is the dominant cation
What is chlorophyll and how is it a water parameter?
Chlorophyll is a pigment molecule that is used as a proxy to determine the amount of algae present in a system
What is permanent hardness?
Concentration of all cations with 2+ or greater charge
How is conductivity measured? How is it reported?
Conductivity is measured using a probe/meter - Reported as u or m Siemens/cm (uS/cm or mS/cm)
Why is the polarity of a water molecule important?
Dipoles interact with other dipoles and oppositely charged dipoles are attracted
What is a type of system with both horizontal and vertical stratification?
Estuaries
In freshwater systems, what is conductivity largely impacted by?
Geology, specifically clay and limestone
What species plays the dominant role in a system's buffering capacity in natural, unpolluted water?
HCO3- + H+ -> H2CO3-
What is the cause of water hardness?
Hardness is primarily due to the Mg^2+ and Ca^2+ ions in the system
How is hardness reported?
Hardness is typically reported as CaCO3 ppm
What is meant by "Water has a high heat capacity"?
Heat capacity is how much energy is required to change the system by 1 C
What is turbidity?
How much light can pass through a sample of water
What is the attractive force of oppositely charged dipoles in water called?
Hydrogen bond
What is the effect of water's max density at 4 C?
Ice floats, so large bodies of water don't freeze solid
How is chlorophyll of a system measured?
Important to note which type of chlorophyll is being measured - Measured with a spectrophotometer or fluorometer
Why is chlorophyll important?
It is used for estimating the amount of nutrients in a system (it indicates excessive nutrients)
What are the two ends of the spectrum of hydrology?
Limnology and Oceanography
What does hypoxic mean?
Low oxygen (2-3 ppm)
What end of the DO scale is associated with anaerobic organisms?
Low oxygen conditions (Anoxic/hypoxic)
What classifies something as a dissolved solid?
Matter that can pass through a 0.45 um filter
What facilitates redox reactions?
Microbes (bacteria)
What pairs of molecules can form hydrogen bonds?
O - H N - H F - H
Which is the more electronegative molecule in water?
O is more electronegative than H
What are bioindicators?
Organisms whose presence can indicate the health of a system - Fishes, invertebrates, and amphibians
What kind of reactions predominantly use up the dissolved oxygen in a system?
Redox reactions
What is salinity?
Salinity is an estimate of the amount of salt content in a system
What is the main variable that the spectrum of hydrology is based on?
Salinity of the water
What is horizontal stratification?
Several haloclines on the coast going out from the shore with the higher salinities being farther out from the coast
What classifies matter as a suspended solid rather than a dissolved solid? What are some examples?
Suspended solids are matter that cannot pass through a 0.45 um filter, such as silk, clay, and metal oxides
Conductivity is the basis for what two parameters within suspended and dissolved solids?
TDS and Salinity
What is TDS derived from and how is it reported?
TDS is derived from conductivity - Reported as ppm and must include the conversion factor, equation and method used, and the sample condition
What water parameter (other than TDS) is conductivity tied to?
Temperature - Often reported as specific conductance (conductivity at 25 C)
How does temperature affect a system?
Temperature affects the properties of the water molecules and the processes going on inside the system
What is the effect of water's high heat capacity?
Temperature regulations and stability, and heat can be transported (ocean currents)
How does temperature affect the chemical equilibria of a system?
Temperature shifts the chemical equilibria
What government agency sets the water quality standards? What is the standard pH for freshwater systems?
The EPA For freshwater systems, the standard pH range is 6/6.5 - 9
What is acidity?
The ability to neutralize a base, most often OH-
What is alkalinity?
The capability of a system to neutralize H+ and resist changes in pH - Also called its acid neutralizing capability (ANC)
What is conductivity?
The measure of the ability of a system to carry an electrical current
What is the water cycle?
The movement of water on, above, and below Earth's surface
As [H+] goes up, what happens to the pH value, and subsequently the acidity?
The pH value decreases and the solution becomes more acidic
As [H+] goes down, what happens to the pH value, and subsequently the acidity?
The pH value increases and the solution becomes more basic
What is limnology?
The study of freshwater
What is oceanography?
The study of the ocean
What is hydrology?
The study of water
What is vertical stratification?
The water below the halocline is more dense and has a higher salinity than the water above the halocline
What would happen if an ion was dropped in water?
The water molecules would surround the ion and create a hydration shell around it
What is TDS?
Total Dissolved Solids
What is TSS?
Total Suspended Solids
What is TSS measured as?
Turbidity
What are the two kinds of stratification?
Vertical and horizontal
What is temporary hardness?
Water that has Ca^2+ (calcium) and HCO3^- (bicarbonate)
What is the effect of water being a good solvent?
Water transports nutrients, wastes, and pollutants
What are two systems in the middle of the spectrum?
Wetlands and some brackish lakes
Dipoles interact with other dipoles and ____
ions
What is the formula for pH?
pH = -log [H+]
What kind of scale is pH measured on?
pH is on a log scale, meaning that any change in pH is a large shift that brings various effects - Each shift on a log scale is a factor of 10
In what units is dissolved oxygen expressed?
ppmO2 (mg/L)
