Water Quality Labs

Lab 01: Temperature

Objective: This lab is short and will introduce you to your lab space, YSI calibrations, and lab notebook expectations.

Introduction

Measuring the temperature of an aquatic system is partly an art.

For example, imagine you are in a boat on an important regional lake and you are determining the surface temperature of lake water at several sampling stations. You are at Station 1 and have just put your alcohol thermometer into the water. It is a bright-sunshine day. Can the sunlight affect your measurement? Yes! You should place the thermometer in your shadow or the shadow of the boat, and you should wait to record until the temperature remains constant. In other words, keep your thermometer in situ to reach equilibrium before taking a reading, and record quickly.

Thermometers

Several types of thermometers exist, we will use either alcohol thermometers (containing alcohol plus a color-dye) or electronic thermometers in this class. In either case it is important to calibrate each thermometer. Calibration ensures accuracy. We will do this today using a linear regression with a line of best fit. This regression will generate an equation that we can use to correct each group’s thermometer reading. This is explained further in the Write Up. /

Organisms are affected by temperature

The temperature of aquatic systems can limit or control the aquatic biota normally found in that system. For example, the eggs of several species of Pacific salmon are temperature sensitive. These anadromous species spend most of their life cycle in marine waters but migrate to native freshwater habitats to reproduce. Fish reproduction will not occur unless the water temperature in streams where their eggs were laid is below certain specific limits.

It is known that many fish-reproducing areas in watersheds where clear-cutting of trees has occurred are no longer viable. Stream habitats that were once protected from direct sunlight by stream-side trees and vegetation are no longer viable reproduction areas because water temperatures frequently exceed critical levels.

Temperature affects other parameters

To determine the saturation level of dissolved oxygen in water, we need to know the water temperature. Warmer waters contain less dissolved oxygen, which places fish and other biota at risk. To assess the toxicity of certain pesticides or heavy metals, water temperature measurements are needed. Similarly, temperature must be known to assess or calculate parameters such as pH, salinity, and conductivity because both the parameters themselves (in the case of pH) and the instruments used to measure them are sensitive to temperature.

Supplies

1. YSI data sonde with electronic temperature probe

• There should be one specifically for the INLET, and another specifically for the OUTLET.

2. Water for calibration

• ice water bath

• warm water bath

3. NIST thermometer

4. Bulb rubber pipetter

5. 4 ml glass pipette

6. 10 ml beaker

• for water that is labelled with name, date, and contents

Methods

1. Measure the temperature of the cold water bath with both the certified thermometer and your thermometer, record once stabilized.

2. Quickly switch to the warm water bath, record once stabilized.

3. Repeat steps 1 and 2 so that you have two measurements of each bath.

4. Practice pipetting using the red rubber bulb

5. See Deliverables section for calculations.

Deliverables

Insert data into shared Google Sheet

The entire class should have access to a Google Sheet where you will write in your average temperature for your measurements. This will allow many data points to ensure accuracy of our YSI throughout the quarter. From here we will generate a linear regression and use the line of best fit. This corrected temperature equation will be used each time we take temperature measurements through the remainder of this course.

Calculations

Show step by step calculations in your notebook of the following:

SLOPE

\(\frac{\Delta y}{\Delta x}\) –> \(\frac{\Delta Corrected Temperature}{\Delta YSI Readings}\)

Y-intercept

\(Y-intercept = Corrected Temperature (°C) - Slope * YSI Readings\)

Corrected temperature equation from the Google Sheet (refer back to this each lab)

For example,

\(-1.755+1.037*YSIReading(°C)\)

Notebook

Examples

Table of Contents

1. Number each page of your notebook

2. Be sure to set the first page aside in your notebook for your TOC

Intro.

Write down the location [Lat/Long] of your sample collection, and the names of the people that collected them. Then jot down some notes about QA/QC. Mention what you did during the lab to increase quality assurance and control. It’s a good time to think about replicates and calibrations. For example,

Methods

Write out your methods, step by step. You should be able to do the lab without this document just by referencing your own steps. They should be simple and easy for you to interpret.

Data & Analysis

Write out exactly what you will measure here. For example, “In this lab we will calculate temperature averages (°C) for YSI and correct temperature. We will use those values to determine the Y-intercept and slope by running a linear regression in Google Sheets, \(y = mx+b\) for both the INLET and the OUTLET probes. We used this to find the calibration equation for our YSI probe and we will use this equation for all future labs.”

This is where you should include a list of all equipment used during the lab, including the Make-model-SN/solution info. For example,

Calculations

Write out step by step calculations here. Include all units and demonstrate dimensional analysis.

Summary

Summarize what you did (50-100 words) and sign and date the bottom of each page.

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