水化学 Analysis of Water Chemistry.ppt

Analysis of Water Chemistry,Urban Stream Restoration Project,By: Bob Smith & Shelly Alicia,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 cant 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),Picture Source: http:/www.ci.gresham.or.us/ departments/des/stormwater/water_quality.htm,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 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 Droug