Foodelphi.com Science of Food Engineering 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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