Natural Natural WaterWater

Chemistry Chemistry

Water Quality ParametersWater Quality ParametersTemperature - Dissolved Oxygen (DO) - pH

Alkalinity - HardnessNitrates and Phosphates - Turbidity

Conductivity-

TemperatureTemperature

Affects:Water densityGas solubilityChemical reaction ratesOrganism growth ratesConductivitypHDissolved Oxygen

… Changes in seasonal/diurnal air temperature

… Thermal stratification in lakes

… Size and temperature of inflows

… Residence time (lakes)

Temperature – naturally variesTemperature – naturally variesbecause of…because of…

… Heated industrial effluent

… Runoff from asphalt/pavement

… Deforestation

Temperature – artificially variesTemperature – artificially variesbecause of…because of…

Q10 rulecold-blooded aquatic organisms

Predicts that growth rate will double if temperature increases by 10˚C (18˚F) within their "preferred" range.

Dissolved Oxygen (DO)Dissolved Oxygen (DO)

DO is the measurement of oxygen dissolved in water and available for fish and other aquatic life.

Indicates health of an aquatic system.

Can range from 0-18 ppm.

Most natural water systems require 5-6 ppm to support a diverse population.

Varies with time of day, weather, temperature.

Dissolved Oxygen (DO)Dissolved Oxygen (DO)Increase in organic waste

Increase in algae/plant vegetation

Decrease in DO available to organisms

Leads to changes in ecosystem asorganisms needing lots of DO are replaced by organisms needing little.

Hood Canal, Wash. DOHood Canal, Wash. DO

HoodCanal

Sill

Saltwater from entrypoint.

Freshwater from streamand river runoff.

Highly stratified

Slow-circulating

Long residence time

Hood Canal

Modified from Hood Canal Dissolved Oxygen Project, Collias, UW, PRISM 2005http://www.hoodcanal.washington.edu/observations/historicalcomparison.jsp

Jan Apr DecSeptJun

Potential causesPotential causesNatural

• increased sunlight or other climate factors• increased nutrient availability• Changes in ocean properties• Changes in river input (e.g.: drought)• Changes in weather conditions

Artificial

• human loading of nutrients or organic material• Changes in river input (eg: diversion)

pHpH - - p(otential of) H(ydrogen)

Determines the solubility of nutrients (PO4-3, NO3

-, C) and heavy metals (Fe, Cu, etc)

Determines availability of these chemicals for use by aquatic life.

In natural water systems, determined largely by geology and soils.

pH of natural waterspH of natural waters

Modified from www.waterwatch.orghttp://www.vic.waterwatch.org.au/fortheteacher/manual/sect4f.htm

due to humic acid

Limestone, marble, CO3 richPure rain, snow

Sea water

Factors that affect pHFactors that affect pH• Algal blooms • Bacterial activity • Water turbulence • Chemicals flowing into the water body • Sewage overflows • Pollution

How pH affects aquatic lifeHow pH affects aquatic life

Decreasing pH (e.g.: via acid rain)

▼Liberation of Al, metals

▼Toxic conditions

▼Chronic stress

▼Smaller, weaker fish

AlkalinityAlkalinityAlkalinity refers to the capability of water to neutralize acid.

Buffering capacity – resistance to pH changes.

Common natural buffer: CO3 (carbonates – like limestone).

Protects aquatic life.

Commonly linked to water hardness.

In natural systems: 50 – 150 mg/L as CaCO3.Limestone outcrop

HardnessHardnessReflects dissolved carbonate minerals.

Mostly of concern for drinking water standards.

Metals precipitate out of solution.

Create scale/hard water deposits

High alkalinity Hard water

From USGShttp://water.usgs.gov/owq/news.html

andandNitrate (NO3

-) naturally-occurring form of nitrogen found in soil.

Forms by microbial decomposition of fertilizers, plants, manures or other organic residues

Plants uptake nitrates (Spinach a good source).

Phosphate (PO4-3)

naturally occurs in rocks and minerals.

Plants uptake weathered-outelements and compounds.

Animals ingest plants.

Water soluble.

Redfield Ratio: 106:16:1

NitratesNitrates

The U.S. EPA has set a maximum contaminant level for NO3

- in drinking water of 10 parts per million (ppm)

Artificial sources:• Livestock manure/urine• Failing septic systems• Synthetic fertilizers

Can lead to:eutrophication of natural water systems (overproduction of vegetation)

Blue baby syndromne

Artificial sources:• Sewage• Laundry, cleaning fluids• Synthetic fertilizers

Can also lead to eutrophication of natural water systems (overproduction of vegetation)

PhosphatesPhosphates

Blue green algae

1990 and 1999 comparison 1990 and 1999 comparison of Nitrates in Great Lakesof Nitrates in Great Lakes

From US EPAhttp://www.epa.gov/glnpo/monitoring/limnology/SprNOx.html

Hypoxia in the Gulf of MexicoHypoxia in the Gulf of Mexico

Gulf of Mexico

Mississippi River drainage basin – 41% of US landmass.

Hypoxia in the Gulf of MexicoHypoxia in the Gulf of Mexico

Hypoxic waters

Image from Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC, January 2003

Hypoxia in the Gulf of MexicoHypoxia in the Gulf of Mexico

From NCAT (Nat’l Center for Appropriate Technology)http://www.ncat.org/nutrients/hypoxia/hypoxia.html

Global distribution of oxygen-depleted coastal zones. Annual = yearly events (summer or autumnal stratification)Episodic = occurring at irregular intervals > one yearPeriodic = occurring at regular intervals < one yearPersistent = all-year-round hypoxia

Sources: Boesch 2002, Caddy 2000, Diaz and others (in press), Green and Short 2003, Rabalais 2002

Source: Patrick Heffer, Short Term Prospects for World Agriculture and Fertilizer Demand 2002/03 - 2003/04 (Paris: International Fertilizer Industry Association (IFA), December 2003); IFA Secretariat and IFA Fertilizer Demand Working Group, Fertilizer Consumption Report (Brussels: December 2001); historical data from Worldwatch Institute, Signposts 2002, CD-ROM, compiled from IFA and the U.N. Food and Agriculture Organization, Fertilizer Yearbook (Rome: various years).

Solutions??Solutions??

Wetland restoration Reduce fertilizers

Reduce emissions – WWTP/industryReduce soil erosion

TurbidityTurbidity

Measures how “murky” the water is

Estimates:

Mineral fractionOrganicsInorganicsSoluble organic compoundsPlanktonMicroscopic organisms

MODIS Image from NASAhttp://rapidfire.sci.gsfc.nasa.gov/

Causes of highly waters

• In open waters, phytoplankton• Closer to shore, particulates Resuspended bottom sediments (wind) • Organic detritus from stream and/or wastewater discharges. • Dredging operations• Channelization• Increased flow rates• Floods• Too many bottom-feeding fish (such as carp)• Hippos

Effects of highly waters

• Modify light penetration• Increase sedimentation rate• Smother benthic habitats • Settling clay particles can suffocate newly hatched larvae • Fine particulate material also can damage sensitive gill structures • Decrease organism resistance to disease• Prevent proper egg and larval development• Macrophyte growth may be decreased• Reduced photosynthesis can lead to lower daytime release of oxygen

From waterontheweb.orghttp://waterontheweb.org/under/waterquality/turbidity.html

ConductivityConductivity

Ability of a substance to conduct an electrical current.

In water, conductivity determined by types and quantities of dissolvedsolids. (Commonly called Total Dissolved Solids = TDS)

Current carried by ions (negatively or positively charged particles).

Eg: NaCl(aq) = Na + + Cl –

Cl-Na+Na+

Na+

Na+

Na+ Cl-

Cl-

Cl-

Cl-

Na+Cl- Cl- Cl- Cl-

Na+Na+ Na+Na+ Na+Na+ Na+Na+

Cl- Cl- Cl- Cl-Na+ Na+ Na+Na+

Cl- Cl- Cl- Cl-Na+ Na+ Na+Na+

Cl- Cl- Cl- Cl-Na+ Na+ Na+ Na+Na+

Na+Na+

Na+ Na+

Na+ Na+

ConductivityConductivity

Conductivity of natural waters depends upon:

Ion characteristics (mobility, valence, concentration)Water temperatureGeologySize of watershedEvaporation

Some artificial factors that can affect conductivity:WastewaterUrban runoff (especially road salt)Agricultural runoff

EC TDS(μS/cm) (mg/L)

Divide Lake 10 4.6Lake Superior 97 63Lake Tahoe 92 64Grindstone Lake 95 65Ice Lake 110 79Lake

Independence 316 213Lake Mead 850 640Atlantic Ocean 43,000 35,000Great Salt Lake 158,000 230,000Dead Sea ? ~330,000

Electrical Conductivity

and

TDS

From wateronthweb.orghttp://www.waterontheweb.org/under/waterquality/conductivity.htmlSalt present in 1L water