Analysis of Water Chemistry

Analysis of Water Chemistry

  • Urban Stream Restoration Project

  • Outline

  • Water Chemistry Background

  • Chemistry in Urban Streams

  • Methods

  • 2003 Results

  • Comparison to 2002

  • Conclusions

  • Outline

  • Water Chemistry Background

  • Chemistry in Urban Streams

  • Methods

  • 2003 Results

  • Comparison to 2002

  • Conclusions

  • Temperature

  • Most aquatic organisms are cold-blooded and have an ideal temperature range, specific to the organism:

  • Diatoms 15-25 degrees C

  • Green algae 25-35 degrees C

  • Blue greens 30-40 degrees C

  • Salmonids – cold water fish

  • Temperature, continued

  • Affects development of invertebrates, metabolism of organisms

  • Affects dissolved oxygen (warm water holds less oxygen)

  • Warm water makes some substances more toxic (cyanide, phenol, xylene, zinc) and, if combined with low DO, they become even more toxic

  • Dissolved Oxygen

  • Oxygen that is dissolved in water

  • DO increases with cooler water and mixing of water through riffles, storms, wind

  • Nutrient loading can lead to algal blooms which result in decreased DO

  • 4-5 ppm DO is the minimum that will support large, diverse fish populations. Ideal DO is 9 ppm. Below 3 ppm, all fish die.

  • Dissolved Oxygen, continued

  • Dissolved oxygen can also be expressed as % saturation

  • 80-124% = excellent

  • 60-79% = ok

  • < 60% = poor

  • Conductivity

  • Measures the ability of water to carry an electric current

  • Measures the ions such as Na+, Cl- in the water

  • Differences in conductivity are usually due to the concentration of charged ions in solution (and ionic composition, temp.)

  • Reported as microsiemens per cm

  • pH

  • pH measures the degree of acidity or alkalinity of the water (each number is a 10-fold difference)

  • 0-6 = acid; 7 = neutral; 8-14 = base

  • Ideal for fish = 6.5 –8.2

  • Ideal for algae = 7.5 – 8.4

  • Acid waters make toxic chemicals (Al, Pb, Hg) more toxic than normal, and alter trophic structure (few plants, algae)

  • Turbidity

  • Measures the cloudiness of the water

  • Turbidity caused by plankton, chemicals, silt, etc.

  • Most common causes of excess turbidity are plankton and soil erosion (due to logging, mining, farming, construction)

  • Turbidity, continued

  • Excess Turbidity can be a problem:

  • Light can’t penetrate through the water – photosynthesis may be reduced or even stop – algae can die

  • Turbidity can clog gills of fish and shellfish –can be fatal

  • Fish cannot see to find food, but can hide better from predators

  • Phosphorus (Reactive)

  • Is necessary for plant and animal growth

  • Natural source = phosphate-containing rocks

  • Anthropogenic source = fertilizer and pesticide runoff from farming

  • Can stimulate algal growth/bloom

  • Nitrates

  • Formed by the process of nitrification (addition of O2 to NH3 by bacteria)

  • Used by plants and algae

  • Is mildly toxic, fatal at high doses

  • Large amounts (leaking sewer pipes, fertilizer runoff, etc.) can lead to algal blooms, which can alter community structure, trophic interactions and DO regimes)

  • Below 90 mg/L seems to have no effect on warm water fish, but cold water fish are sensitive

  • Alkalinity

  • A measure of the substances in water that can neutralize acid and resist changes in pH

  • Natural source = rocks

  • Ideal water for fish and aquatic organisms has a total alkalinity of 100-120 mg/L

  • Groundwater has higher alkalinity than surface water

  • Hardness

  • The amount of Calcium and Magnesium in the water (the two minerals mostly responsible)

  • Natural source = rocks

  • Limestone = hard water, granite = not hard water

  • Hardness, continued

  • Soft water can be a problem: in soft water, heavy metals are more poisonous, some chemicals are more toxic, drinking soft water over long periods can increase chance of heart attack

  • 0 – 60 = soft water

  • 61-120 = moderately hard water

  • 121-180 = hard water

  • 181+ = very hard water

  • Hardness and alkalinity are related

  • Outline

  • Water Chemistry Background

  • Chemistry in Urban Streams

  • Methods

  • 2003 Results

  • Comparison to 2002

  • Conclusions

  • Physical Effects of Urbanization Related to Water Chemistry

  • Riparian Vegetation Removal

  • Decreased Groundwater Recharge

  • Heat Island Effect

  • Increased Surface Runoff / Impervious Surfaces

  • Leaky Storm-water / Sewage Pipes

  • Point Source Pollution

  • Trends in Water Chemistry

  • Temperature increases

  • Nitrate increases

  • Phosphorus increases

  • Conductivity increases (Increased ion concentration)

  • O2 demand increases

  • Outline

  • Water Chemistry Background

  • Chemistry in Urban Streams

  • Methods

  • 2003 Results

  • Comparison to 2002

  • Conclusions

  • Field Measurements

  • Dissolved Oxygen

  • Temperature

  • Conductivity

  • pH

  • Water Collection For Laboratory Analysis

  • Grab Samples

  • Three replicates (from multiple samples)

  • Measured within 24 hours (few exceptions)

  • Laboratory Analysis

  • Nitrate

  • Reactive

Phosphorus

  • Alkalinity

  • Hardness

  • Turbidity

  • Outline

  • Chemistry in Urban Streams

  • Water Chemistry Measurements and Theory

  • Methods

  • 2003 Results

  • Comparison to 2002

  • Conclusions

  • Field Measurements 2003

  • Turbidity

  • All values for 2003 <5 jtu

  • For 2002, all but one sampling date <5 jtu

  • The one date for 2002 >5 was during a storm event

  • Reactive Phosphorus 2003

  • Nitrate 2003

  • Alkalinity 2003

  • Hardness 2003

  • Outline

  • Chemistry in Urban Streams

  • Water Chemistry Measurements and Theory

  • Methods

  • 2003 Results

  • Comparison to 2002

  • Conclusions

  • Field Measurement PB

  • Field Measurement For SAL

  • Paint Branch

  • Stewart April Lane

  • Outline

  • Chemistry in Urban Streams

  • Water Chemistry Measurements and Theory

  • Methods

  • 2003 Results

  • Comparison to 2002

  • Conclusions

Between Site Differences

  • Land use – increased runoff cause increased input of particular constituents

  • Natural site variation – Substrate type

Between Years

  • Increased snow caused more runoff increased use of road-salt

  • Drought (temperature, DO)

“. . . Rivers and the inhabitants of the watery element were made for wise men to contemplate, and fools to pass by without consideration, . . . for you may note, that the waters are Nature’s storehouse, in which she locks up her wonders.”

  Izaak Walton

  (from Ward, 1992)

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