water quality anlysis

Temperature

Measures changes in the ambient water temperature and affects dissolved oxygen, metabolic rates, photosynthesis, disease sensitivity, reproduction, and decomposition rates.

Temperature

Measurement Measured with a thermometer or temperature probe.

Temperature and Dissolved Oxygen

Cold water holds more oxygen than warm water; temperature directly affects DO levels.

Temperature Effects on Metabolism

Increases metabolic rates of aquatic organisms as water warms.

Temperature Effects on Photosynthesis

Affects the rate of photosynthesis by aquatic plants and algae.

Temperature and Disease

Sensitivity of organisms to disease, parasites, and pollution increases with higher temperatures.

Temperature and Reproduction

Small chronic temperature changes can adversely affect reproductive systems of aquatic organisms.

Temperature and Decomposition

Raising water temperature increases decomposition of organic matter, depleting dissolved oxygen.

Types of Temperature Changes

Natural seasonal changes, industrial thermal pollution, stormwater runoff from heated surfaces, soil erosion increasing turbidity, and removal of shade trees along shores.

pH

Measures hydrogen ion concentration on a scale from 0 to 14, indicating acidity or alkalinity of water.

pH Measurement

Measured with pH paper, pH meter, or pH probe.

pH Scale

Logarithmic scale: each 1

Acidic Water

pH 0–7; water can release heavy metals and harm aquatic organisms.

Basic Water

pH 7–14; ammonia converts to toxic forms in high pH water.

Neutral pH

pH of 7; equal hydrogen and hydroxyl ions.

Normal River pH

US rivers usually between 6.5–8.5.

Safe pH Range for Aquatic Life

6.0–9.0 supports freshwater fish and bottom

Lethal pH Levels

Below 4.5 or above 11 is fatal for most aquatic organisms.

pH Effects on Organisms

Crustaceans, insects, plankton start disappearing at 6.0; major plankton changes at 5.0; water largely devoid of fish below 5.0.

Acid Rain

pH <5, lowers pH of water bodies and harms ecosystems.

Geologic Buffering

Limestone and geology can neutralize acidic effects.

Natural Acid Sources

Volcanoes, geysers, hot springs.

Turbidity

Measures water clarity; clear water = low turbidity, cloudy water = high turbidity.

Turbidity Units

Measured in Nephelometric Turbidity Units (NTU) based on light scattering.

Causes of Turbidity

Suspended sediment, algal blooms, dead organic matter.

Turbidity Effects

Reduces light penetration, limits photosynthesis, affects fish gill oxygen absorption.

Secchi Disk

Black and white disk lowered into water until invisible to measure clarity.

Secchi Disk Rule of Thumb

Light penetrates ~2–3 times the Secchi disk depth.

Seasonal Turbidity

Changes Fall lake turnover, algal blooms, and runoff can affect turbidity.

Human

Induced Turbidity

Dissolved Oxygen (DO)

Measures gaseous oxygen dissolved in water essential for aquatic life.

DO Sources

Diffusion from air, photosynthesis, water movement/aeration.

DO Units

Measured in parts per million (ppm).

Healthy DO Levels

5–15 ppm in surface water.

Low DO

Stress Below 5 ppm stresses aquatic life.

Lethal DO Levels

1–2 ppm for a few hours can kill large fish.

Factors Affecting DO

Temperature, suspended solids, plant life, respiration, decomposition, daily fluctuations, algal blooms.

Human Impacts on DO

Organic waste, urban runoff, dams, and removal of shade vegetation reduce DO.

Diel DO Fluctuation

DO changes from day to night due to photosynthesis and respiration cycles.

Algal Bloom Effects on DO

Algae increase oxygen during day, deplete it at night causing large fluctuations.

Biochemical Oxygen Demand (BOD)

Measures how fast organisms use oxygen to decompose organic matter.

BOD Testing

Uses DO testing materials over time to measure oxygen consumption rate.

Natural BOD Sources

Plant decay, leaf fall.

Human

Induced BOD

BOD and DO Relationship

Higher BOD = lower dissolved oxygen; can kill low

Phosphates

Measures phosphorus compounds essential for plant and animal growth.

Phosphate Sources

Natural: rocks, normal animal/plant waste. Human: fertilizers, pesticides, industrial/cleaning compounds, sewage, septic tanks.

Phosphate Effects

Stimulates aquatic plant and plankton growth; excess causes algal blooms and oxygen depletion.

Nitrates

Measures nitrogen forms (ammonia NH3, nitrates NO3, nitrites NO2) needed for plant growth.

Nitrate Sources

Fertilizers, failing septic tanks, wastewater, manure, runoff from crop fields, lawns, feedlots, and car exhaust.

Nitrate Effects

Stimulates plant/algae growth; excess causes accelerated eutrophication, reduces oxygen.

Ammonia Oxidation

Bacteria convert ammonia to nitrates, consuming dissolved oxygen.

Total Solids

Measures suspended and dissolved solids in water.

Suspended Solids

Silt, clay, plankton, organic/inorganic particles; settle at bottom.

Dissolved Solids

Calcium, nitrogen, phosphorus, sulfur, and other ions; pass through filters.

Effects of High Total Solids

Increases turbidity, reduces photosynthesis, increases temperature, binds toxic chemicals.

Fecal Coliform

Measures bacteria from intestines of warm

Fecal Coliform Units

Reported as colonies per 100 mL of water.

Unsafe Fecal Coliform Levels

Above 200 colonies/100 mL indicates potential pathogens.

Fecal Coliform Sources

Failing septic systems, animal waste, sewage discharge, urban runoff.

Salinity

Measures salt concentration in water.

Salinity Sources

Seawater intrusion, human/animal waste, industrial waste, fertilizers, winter road salts.

Salinity Measurement

Using a hydrometer or salinometer; higher density = more salt.

High Salinity

Effects Reduces plant growth, stresses freshwater organisms, degrades water quality.

Key Water Quality Relationships

High nutrients → algal blooms → increased BOD → lower DO → possible fish kills.