Water+Quality+Tests+Background+Information+and+Questions

=pH=

pH is a measure of how acidic or how basic something is. When we measure pH we are measuring the level of hydrogen ions (H+) or hydroxide ions (OH-) that are present in our water sample.

pH is measured on a scale of 0 to 14. A neutral solution has a pH of 7. In a neutral solution the activity of H+ ions equals that of the OH- ions. An acidic solution will have a pH less than 7 and will have more H+ activity. A basic solution will have a pH greater than 7 and will have more OH- activity.
 * **Acidic** || Neutral || Basic ||
 * pH = less than 7 || pH = 7 || pH = greater than ||

1. If something has a pH lower than 7 we call it “acidic.” Please name at least three things you can think of that you know are acidic. 2. When we measure pH what are we actually measuring? 3. If a sample has a pH of 7 is it acidic, neutral, or basic?

How does the urban ecosystem affect pH?
There are a number of ways in which the urban ecosystem can, and often does, affect the pH of water. First, let’s consider the water from the Quabbin and Wachusetts Reservoirs, our tap water sources. Although this water may have started its journey to Boston as a slightly acidic raindrop, its pH will be dramatically increased (i.e. it will become more basic) when it flows through the water treatment plants.(1) But why? Why does the water treatment plant staff want to increase the pH of the water?

They want to do this because acidic water (water with a low pH) can sometimes corrode pipes. Pipe corrosion is a problem for maintenance reasons (you don’t want you pipes to corrode and leak!) and for health reasons (corrosive water can dissolve lead in fixtures and pipes, thus leading to lead in the water). By increasing the pH of the tap water, the people who treat our water are helping reduce the negative impact of lead in drinking water.(2)

Another way that the pH of water can change in the urban ecosystem is through contact with lime-rich bedrock or pavement. Both lime-rich bedrock and pavement (just concrete, not asphalt!) easily give up positive ions (such as calcium ions, Ca+). Calcium?! Yes, calcium is found in more than just milk; it can also be found in rocks and pavement and trees and soil. Like water and other material you may have learned about, calcium is also cycling through ecosystems. The calcium that exists today in rocks was once part of a shell of an animal in an ocean millions of years ago. When that animal died, its shell settled into the sediment and eventually solidified into rock (a process called lithification). The calcium that can be found in some types of pavement comes from rock (rock that was made of old seashells) that has been ground up and then used to make concrete. When the calcium from the concrete or the rocks dissolves in the water, it continues the cycle, eventually flowing with the water into the ocean. In the ocean the calcium may someday be used by an aquatic plant and someday that an animal might eat the plant. When an animal eats the plant the calcium may become part of the animal’s shell or exoskeleton or bones… And so the cycle continues! When hydrogen ions (H+) are very active in water, they can react with other molecules and interfere with biochemical reactions that are important for aquatic organisms. The same is true for high levels of hydroxide (OH-) ions. Most aquatic organisms grow and reproduce best within an ideal range of pH. If the pH gets a little higher or lower than this ideal range, the organism might be stressed or experience limited reproduction. If the pH goes much beyond the ideal range, then some organisms will begin to die. If the pH becomes very acidic or very basic, __all__ organisms may die. But what do these numbers really mean in terms of how strongly acidic or basic a solution is? The pH scale is actually logarithmic. This means that water with a pH of 4 is actually __ten times__ more acidic than water with a pH of 5! Likewise, that water with a pH of 5 is actually __one hundred times__ more acidic than water with a pH of 6!
 * Why does the pH of the water matter?**

1. Are raindrops naturally acidic, basic, or neutral?

2. Why is a change in pH potentially dangerous for an aquatic ecosystem?

=Dissolved Oxygen=

Like other animals, we need oxygen in order to stay alive and, like all animals that live on land, we get that oxygen from the air we breathe. But what about aquatic organisms, creatures that live in water… do they need oxygen? And, if so, how do they get it? Many aquatic organisms, such as fish, insects, and some bacteria, //do// need oxygen in order to survive. Even plants need oxygen in order to respire (breathe) in the dark. But how do they get oxygen underwater? Is there any oxygen in water? Yes, there //is// oxygen in water! You may already know that each water molecule is made up of one oxygen atom and two hydrogen atoms. However, even aquatic animals, plants and bacteria cannot breath the oxygen atoms that are part of water molecules. Fortunately for the fish (as well as the insects, plants, and bacteria) there is other oxygen in water, oxygen that __is__ available for breathing! This oxygen (in the form of oxygen gas, O2) is called “dissolved oxygen” because it has that has dissolved in the water. In other words, this oxygen can be found in the spaces between the water molecules (1). (These spaces are very tiny to us but they are big enough to fit O2 molecules!)

How does Dissolved Oxygen get into the water?
Dissolved Oxygen gets into the water through wave action and photosynthesis. Wave action involves moving water and making waves. Think of a breaking wave or a waterfall and picture all the air that gets mixed in with the water. When that air gets mixed into the water (making the water look bubbly or white) some of the oxygen from the air dissolves into the water and you get…dissolved oxygen! Photosynthesis takes place when plants use sunlight, water, and carbon dioxide to make carbohydrates (sugars). The byproduct (the left over material, or waste) of this process is… Oxygen! When plants that live in water photosynthesize, the oxygen that they give off (as waste) ca where it can be used by aquatic organisms that need it (2).

Why do we bother to measure the amount of Dissolved Oxygen in water?
When we measure the amount of dissolved oxygen in a sample, we are measuring the amount of oxygen that is “trapped” between water molecules. This amount is important because without dissolved oxygen, fish and other aquatic organisms could not survive. Since many aquatic organisms like to live in water with high levels of dissolved oxygen, a measurement of dissolved oxygen can let us know if an aquatic ecosystem could be good habitat. Certain species of fish such as salmon ot trout, for example, can __only__ live in ecosystems with high levels of dissolved oxygen. If you like to eat salmon or trout then dissolved oxygen is important to you too!

1. What are aquatic organisms? 2. Do any aquatic organisms need oxygen in order to survive? 3. Please explain what dissolved oxygen is. 4. How do aquatic plants contribute dissolved oxygen to the water?

As you have already read, Dissolved Oxygen (O2) is essential for many aquatic organisms. Unfortunately, however, there is not always enough dissolved oxygen to go around. Temperature, impurity, and demand for oxygen all affect how much is available to those who need it. These variables (temperature, impurity, and demand for oxygen) can change in all different types of ecosystems, including the urban ecosystem. Changes in these variables can result in lower dissolved oxygen levels in the following ways: 1. How do you think water could get heated as it passes through the urban ecosystem?
 * __An increase in water temperature__**: Warmer water can hold less dissolved oxygen than colder water. This is because warmer water has more energy so its molecules are bouncing around more and its hydrogen bonds (which hold the dissolved oxygen in the water) break more often.

2. What do you think could dissolve in water as it passes through the urban ecosystem?
 * __An increase in impurity__**__:__ Pure water can hold more dissolved oxygen than impure water (at equal temperatures). That means that when substances such as salt are dissolved in water, that water loses the ability to hold as much dissolved oxygen as it could when it was pure.


 * __An increase in demand for oxygen__**__:__ When humans add fertilizer and other nutrients to the urban ecosystem these nutrients can get into the water where they can cause plants to grow. Normally, more plant growth means more oxygen produced as a byproduct. But, more plant growth also means more plant death. When plants die, they will be consumed by bacteria. Since many of the bacteria need oxygen there is an increase in demand for oxygen (also called **biological oxygen demand**). (For more information about this process please ask your teacher about the handout “What is Eutrophication?”)

=Nitrates=

Nitrates are a form of Nitrogen and they are very important to us. Did you know that we (humans) need nitrogen in order to survive? Why? Because plants need nitrogen in order to live and we need plants in order to live! Although Nitrogen gas, N2, composes about 78% of the volume of the troposphere (the first 17 miles of air above the earth’s surface) plants have a problem: they are not able to get their nitrogen directly from the air. They just can’t. This is where nitrate comes in. Nitrate (NO3-) is composed of Nitrogen and Oxygen and plants and plants __are__ able to consume it. By consuming nitrate plants can get the nitrogen the need to go on living and growing. The process of taking nitrogen gas and turning it into nitrate is called nitrogen fixation. Before the invention of fertilizer factories, beneficial soil bacteria were responsible for almost all of the nitrogen that was “fixed.” These soil bacteria are still hard at work today but now humans are making nitrate too, a lot of it! Humans are making nitrate and adding it to soil because, as you already know, plants need nitrate in order to grow. Nitrate is a wonderful fertilizer! However, too much of it can be a problem. When excess nitrates wash off of the land and into the water, aquatic plants can grow out-of-control and water quality can be negatively affected. Although most city dwellers (people who live in the urban ecosystem) do not grow their own vegetables and grains, somewhere, a farmer __is__ growing food to feed the city dwellers. On some of the farms nitrates may be added to the fields and wash off into rivers, lakes and streams. In this way, humans in the urban ecosystem are connected to nitrates on the farms (sometimes thousands of miles away!) that grow their food. Do you know if nitrate is added to the fields where your food is grown? Other ways that the urban ecosystem affects nitrate levels in water are through the addition of fertilizer to lawns (think of the lush green of Boston Commons!) and through sewage. That’s right, sewage is rich in nitrates and, when it gets into the water system, can also lead to excessive growth of aquatic plants. When the nitrates from sewage reach the oceans they can cause harmful algal blooms. Harmful algal blooms happen when harmful algae grow very quickly and release toxins. Sometimes these “blooms” can kill birds, reduce tourism, and even poison seafood! Until recently, the rivers and harbor of Boston had a lot of sewage dumped into them, some treated (partially cleaned) and some untreated. Now, the city is trying to make sure that no untreated sewage flows directly into the rivers and harbor. Also, sewage that goes to the treatment plant gets treated more thoroughly and the nitrates and other fertilizing wastes that are removed from the sewage are turned into “Bay State Fertilizer.” Now, instead of causing harmful algal blooms, the nitrates from Boston’s sewage can be used to help plants grow in lawns and gardens!
 * How do plants get the nitrogen they need?**
 * Why are humans making and using extra nitrate?**
 * How does the urban ecosystem affect nitrate levels in the water?**

1. What is the process of turning nitrogen gas into nitrate called? And who was responsible for this (before the invention of fertilizer factories)?

2. Please explain two ways in which the urban ecosystem affects nitrate levels.

3. Please explain why the Urban Ecosystem could not survive without nitrogen.

=Phosphates=

When we measure the concentration of “phosphates” in the water we are essentially measuring how much phosphorous is in the water. But what is phosphorous and why should we even care how much of it is in the water? Phosphorous is an element that, like nitrogen and oxygen (among others), is essential to life. There is phosphorous in your body and in the bodies of all animals.(1) Without phosphorous, plants would not grow and neither would we! Without phosphorous we would not be able to make a very important molecule called ATP (Adenosine Tri-__Phosphate__). ATP is helps our cells store and transfer energy and it is one of the four nucleotides in DNA and RNA. As you may have noticed, ATP has the word “phosphate” in its full name. That is because each ATP molecule contains three phosphorous atoms. Without phosphorous, ATP would not be possible and without ATP, life as we know it would cease to exist. Of course, it is possible to have too much of this normally “good” thing. Too much phosphorous can upset delicate balances and result in negative changes in an ecosystem. Because phosphorous helps plants grow, too much phosphorous can cause dramatic increases in plant growth. Although plants are usually “good” for ecosystems, dramatic increases in plant growth can actually lead to a decrease in dissolved oxygen in the water –a “bad” thing for the organisms that need oxygen! Phosphorous naturally cycles through many ecosystems and can be found in decaying plant and animal matter, soil, and animal waste. In the urban ecosystem, phosphorous can enter the water in several ways. The concentration of phosphorous in the urban water can increase when exposed soil erodes in storm water (for example, at a construction site or in an park where the grass has worn down), when fertilizer that people apply to lawns, gardens, or parks dissolves in storm water, or when sewage or animal waste gets into the water. In the past, urban ecosystems also added a lot of phosphorous/phosphate to the water in the form of laundry and dish washing detergents. However, many people were worried about the negative environmental effect of all this phosphorous/phosphate. These people took their concerns to the government and in the 1970s laws were passed that reduced the amount of phosphate allowed in most detergents!

1. Please identify one process that would be impossible without phosphorous. 2. What are some places in the city where you think erosion may be contributing to elevated (higher) levels of phosphates in storm water? 3. What do you think could be done to reduce erosion at those sites?

=Macroinvertebrates= Organisms have varying levels of tolerances to pollution. If a species pollution tolerance is know than it can be used as a bioindicator. A bioindicator or indicator species is a plant or animal that can be used to measure levels of pollution through its behavior and/or population levels in a specific ecosystem. Macroinvertebrates respond differently to the conditions within a stream and are considered good bioindicators. For example, many immature aquatic insects, such as stoneflies and water pennies, are sensitive to dissolved oxygen levels and can only survive in water with dissolved oxygen levels greater than 8 parts per million (ppm). Other insects, such as immature mayflies, have special gills that help them successfully adapt to lower levels of dissolved oxygen. Macroinvertebrates also vary in their levels of pollution tolerances. Those that are pollutant-sensitive rarely survive in an environment of poor water quality. Macroinvertebrates different in pollution sensitivity because of different adapatations.. Certain invertebrates, such as mayflies, have gills outside of their bodies and are more sensitive to pollution than those with gills inside their bodies. Snails with lungs are less sensitive to pollution than snails with gills that are dependent on water filtration for oxygen. A healthy aquatic ecosystem will have a variety of pollution-tolerant and pollutant-sensitive organisms. A river with poor water quality will have very few pollutant-sensitive invertebrates. Macroinvertebrate sampling is one technique used to determine the health of a stream. Chemical and bacterial testing, physical and habitat assessments also exist to provide more information on the health of a stream. Although chemical tests are frequently used, they have limits that can be overcome with biological sampling. For instance, chemical monitoring may miss a pollutant in the stream because the kit used may not include tests for that particular substance. Also, chemical testing is only a snapshot determination of stream health and pollution for that moment. Results may suggest a stream is clean even if it is polluted the other 364 days in the year. Meanwhile, macroinvertebrates are subjected to day-to-day and longer term changes in pollution, oxygen levels, and acidity levels. So what macroinvertebrates you find in the stream reflects how healthy that still is overall or most of the time. There are three major pollution tolerance categories of macroinvertebrates - **sensitive**, **facultative** and **tolerant**. The presence of sensitive organisms generally indicates good water quality because these macroinvertebrates cannot survive under polluted conditions. Facultative creatures are normally a sign of moderate water quality. These macroinvertebrates can exist under a wider range of water quality conditions than sensitive organisms can. Macroinvertebrates that can live in polluted waters are called tolerant. In large numbers, and in the absence of sensitive organisms, they point to poor water quality conditions. In high-quality streams, //each// macroinvertebrate group should be represented, though there will probably be more sensitive organisms than tolerant or facultative organisms. Finding a worm or midge larva (both tolerant organisms) does not mean the stream is polluted, as long as there is a variety of other types of insects (sensitive and facultative) in the sample. The worms and midge larvae are just helping to make a biodiverse stream. However, a net full of worms and midges with no sensitive organisms will give a stream survey a poor rating because biodiversity is lacking. A **Pollution Tolerance Index** is a method that is used to rate stream quality based on macroinvertebrates. Samples are taken and examined for the presence and abundance of the different types of organisms. These values are put into an equation, which gives an overall number value to the stream. Certain numbers indicate poor quality, while others indicate moderate or good quality water. Because different macroinvertebrates have different levels of tolerance to pollution, the amount of stress a stream is under can be measured by the organisms that live in that stream. Environmental degradation decreases the number of different types of organisms in a community by eliminating sensitive creatures while increasing the number of tolerant ones. This decreases the **biodiversity** (number of different forms of life) of the stream.