Lab 4 water quality - New Mexico State Universityweb.nmsu.edu/~aulery/docs/Lab_04.pdf · Prepare a...
3
Course: ES 110L Introduction to Environmental Science Lab Unit: Environment problems and solutions Content: Water quality Environmental Science Laboratory 110L New Mexico State University, Department of Agronomy and Horticulture 1 Water Quality Lab #4: Water Quality Surface Water; Sampling the Rio Grande Goals The purpose of this lab is to familiarize students with common surface water contaminants and testing/sampling techniques. Introduction Life, as we know it here on earth, is dependent on liquid water for survival. Perhaps at first glance this is no surprise as about 70% of Earth’s surface is covered by water. Indeed countless creatures are at home in the salty seawater of our oceans. However, many life forms - including humans - are intolerant of such brackish water. For this reason, freshwater supply has played a major role in the development of human civilizations throughout the centuries. Typically, communities are limited regarding their source of freshwater. A potable water source must be convenient, cheap, and free of contaminants. Freshwater contamination is common, and can involve heavy metals like arsenic, lead, or cadmium. However, pathogenic microbes, toxic organic substances, and even radioactive material can find their way into freshwater supplies as well. Clearly it is important for us to be able to distinguish between clean water sources and contaminated water sources. Before we begin evaluating water samples, it is important that we first clarify what a “contaminated” water source really is. All natural sources of freshwater contain impurities. The nature and amount of impurities depends heavily on the type of water source and its geographic location. Fluoride for example is a common impurity in freshwater. It is believed that small amounts of fluoride in drinking water promote good dental health. For this reason, some municipal water authorities actually add fluorine to drinking water. However, high levels of fluorine are reported to be toxic. How could this be? Could a toxic chemical actually improve your dental health? To most it seems unreasonable; however, life is in fact in a delicate balance and the difference between healthy and toxic is often minute. The case of fluorine is a controversial one that will likely be debated for some time without resolution. Fortunately, most contaminants are more clear-cut. Thus, to protect public health and promote safe drinking water supplies, Congress passed the Safe Drinking Water Act in 1974. This law requires the Environmental Protection Agency (EPA) to set and maintain standards for contaminants that threaten human health. These standards are called maximum contaminant levels (MCL), and they are continually being evaluated and updated. These standards define the level of contamination that is safe for us to drink. Figure 1: Rio Grande River Courtesy of USGS: http://nc.water.usgs.gov/
Transcript of Lab 4 water quality - New Mexico State Universityweb.nmsu.edu/~aulery/docs/Lab_04.pdf · Prepare a...
Course: ES 110L Introduction to Environmental Science Lab Unit: Environment problems and solutions Content: Water quality
Environmental Science Laboratory 110L New Mexico State University, Department of Agronomy and Horticulture 1
Water Quality
Lab #4: Water Quality Surface Water; Sampling the Rio Grande Goals The purpose of this lab is to familiarize students with common surface water contaminants and testing/sampling techniques. Introduction Life, as we know it here on earth, is dependent on liquid water for survival. Perhaps at first glance this is no surprise as about 70% of Earth’s surface is covered by water. Indeed countless creatures are at home in the salty seawater of our oceans. However, many life forms - including humans - are intolerant of such brackish water. For this reason, freshwater supply has played a major role in the development of human civilizations throughout the centuries. Typically, communities are limited regarding their source of freshwater. A potable water source must be convenient, cheap, and free of contaminants. Freshwater contamination is common, and can involve heavy metals like arsenic, lead, or cadmium. However, pathogenic microbes, toxic organic substances, and even radioactive material can find their way into freshwater supplies as well. Clearly it is important for us to be able to distinguish between clean water sources and contaminated water sources. Before we begin evaluating water samples, it is important that we first clarify what a “contaminated” water source really is. All natural sources of freshwater contain impurities. The nature and amount of impurities depends heavily on the type of water source and its geographic location. Fluoride for example is a common impurity in freshwater. It is believed that small amounts of fluoride in drinking water promote good dental health. For this reason, some municipal water authorities actually add fluorine to drinking water. However, high levels of fluorine are reported to be toxic. How could this be? Could a toxic chemical actually improve your dental health? To most it seems unreasonable; however, life is in fact in a delicate balance and the difference between healthy and toxic is often minute. The case of fluorine is a controversial one that will likely be debated for some time without resolution. Fortunately, most contaminants are more clear-cut. Thus, to protect public health and promote safe drinking water supplies, Congress passed the Safe Drinking Water Act in 1974. This law requires the Environmental Protection Agency (EPA) to set and maintain standards for contaminants that threaten human health. These standards are called maximum contaminant levels (MCL), and they are continually being evaluated and updated. These standards define the level of contamination that is safe for us to drink.
Figure 1: Rio Grande River Courtesy of USGS: http://nc.water.usgs.gov/
Course: ES 110L Introduction to Environmental Science Lab Unit: Environment problems and solutions Content: Water quality
Environmental Science Laboratory 110L New Mexico State University, Department of Agronomy and Horticulture 2
Water Quality
Pre-lab Questions and Resources 1. Visit the EPA website and find the MCLs for as many compounds as you can. For your quiz
next week, pay special attention to arsenic, lead, and cadmium.). http://www.epa.gov
2. The EPA maintains a list of approved analytical techniques for determining the level of contaminants in drinking water. Find this list on the EPA website and choose three contaminants to focus on. Could these techniques be used in the field? Why or why not?
3. There are many pros and cons to having fluoride in drinking water – the web is literally
overflowing with websites devoted to one side or the other. Using an internet search engine, find a few of these websites and browse the information. Do these sites seem credible? Why or why not? What sites, if any, do you trust?
4. While the EPA maintains standards for our drinking water, the USDA does not regulate
contaminant levels in bottled water. Keeping this in mind, what does water purity mean to you? Do the best drinking water supplies contain 100% H2O? Should the USDA consider regulating bottled water?
Key Words Maximum Contaminant Level (MCL), potable Objectives 1. Know the definition of key words shown in bold. 2. Learn to identify common surface water contaminants. 3. Learn to safely and effectively operate analytical equipment in the field. 4. Identify possible sources of inaccuracy in collected data. 5. Prepare a lab report on your findings. Procedure This lab will be a field trip to some local surface water sources. We will be taking water samples and analyzing for several contaminants including nitrates and phosphates. We will also look at other water quality factors such as dissolved oxygen, temperature, turbidity, pH, electrical conductivity (EC), and coliform bacteria. We will be doing a number of quantitative and qualitative techniques to determine these parameters. Detailed instructions on how to perform these techniques will be provided during the lab. The table below is intended to help you keep track of your results.
Course: ES 110L Introduction to Environmental Science Lab Unit: Environment problems and solutions Content: Water quality
Environmental Science Laboratory 110L New Mexico State University, Department of Agronomy and Horticulture 3
Water Quality
Technique
Variable Quantitative Qualitative
Temperature
Nitrate
DO
pH
Phosphate
EC
Turbidity
BOD
Coliform
Lab 4 Data
Table 1 Calculations and Data Presentation Prepare a spreadsheet that displays the data you collected in tabular form (similar to Table 1). Include the MCL’s for each contaminant and specify whether or not your measurement exceeds the MCL. Include this table in either the body or an appendix of your lab report. Prepare an Abbreviated lab report according to the directions outlined in the course website at http://web.nmsu.edu/~aulery/. Questions
1. Write 4-6 sentences discussing possible sources of any contaminants you found in your samples (i.e. where might any phosphates or nitrates in your samples have originated?).
2. Using the data you collected, discuss why you would or would not drink
unfiltered/unprocessed water from the sources you sampled? Write no more than 4 sentences.
3. Do the quantitative and qualitative results obtained in this lab seem to agree with each
other? What factors might contribute to any differences you may notice?
