1. EEOB 655 Lab #4: pH, Alkalinity, Acidity, Calcium, Conductivity Joe Conroy 20/21 April 2004 pH Conductivity Calcium Alkalinity Acidity Lake Function

2. EEOB 655 Goals 1)Measure pH, alkalinity, acidity, calcium, and conductivity in three water sources 2)Determine how these parameters interact to shape lake function 3)Gain familiarity in lab analytical techniques

3. EEOB 655 pH Measure of the hydrogen ion concentration pH = -log[H] Use either color indicators or electrodes Electrode system description on pp. 126-127

4. EEOB 655 Alkalinity Buffering capacity of lake waters Due to dissolved substances that accept protons Carbonate species important Amount of carbonate present dependent on pH, watershed, partial pressure of CO 2 in atm. CO 2 (atm)  CO 2 (dis)+H 2 0  H 2 CO 3  H + +HCO 3 -  H + +CO 3 2- In practice, Alkalinity = acid added to equivalence point standardized to CaCO 3

5. EEOB 655 Acidity Opposite of Alkalinity Determines the amount of CO 2 dissolved in lake water Acidity = base added to equivalence point Selection of acid or base of the appropriate normality simplifies calculations (pp. 131-132)

6. EEOB 655 Calcium Important for determining the “hardness” of lake water Hardness determines the ability of water to precipitate soap Expressed in terms of CaCO 3 /L Determined using Sodium EDTA titration

7. EEOB 655 Specific Conductance Measure of the dissolved ions in a lake water sample Equal to the inverse of the resistance Temperature of importance (inc. of 2-3%/°C) Use a conductivity meter Standardized to 25°C and to a standard KCl solution

8. EEOB 655 Consequential Questions How do alkalinity, acidity, and pH interact to determine the total dissolved inorganic carbon in a lake? How do phytoplankton (who are taking up C for photosynthesis) affect the alkalinity? How does calcium affect carbon concentration and phytoplankter processes?