<p>
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<p>
	<a href="http://participatoryscience.org/mercury-watersheds/essential-activity-why-do-we-care-about-mercury">Why Do We Care About Mercury?</a></p>
<p>
	<a href="http://participatoryscience.org/mercury-watersheds/optional-activity-concentrations">Mercury Concentrations</a></p>
<p>
	<a href="http://participatoryscience.org/mercury-watersheds/optional-activity-mapping-us-mercury-emissions">Mapping U.S. Mercury Emissions</a></p>
<p>
	<a href="http://participatoryscience.org/mercury-watersheds/optional-activity-road-toxicity">The Road to Toxicity</a></p>
<p>
	T<font size="2">he objective for the activities in this first unit is to provide students with the key information about mercury and about how mercury moves around in forests, ponds, and other areas.<span>&nbsp; </span>Our goal is to give the students the background they need to investigate the amounts of mercury in plants, invertebrates, fish, and people.<span>&nbsp; </span>Later on, we will expect them to consider questions such as &ldquo;Would caterpillars have a higher mercury burden than beetles?&rdquo;<span>&nbsp; </span>or &ldquo;What is the relationship between fish diet and fish mercury burden?&rdquo; </font></p>
<p>
	<font size="2">In order for the students to be able to work with questions such as these in some way other than blind guessing, they need to develop a basic understanding of how mercury gets into their pond, field, forest, stream, or other area that they are studying.<span>&nbsp; </span>They also need to have a general feel for the factors that need to be present in order for the mercury to change into a form in which it can be absorbed by living things.<span>&nbsp; </span>In short, the students need a basic understanding of mercury chemistry.</font></p>
<p>
	<font size="2">The students need to understand more than the chemistry, of course.<span>&nbsp; </span>They also need to understand how bioaccumulation works, which means understanding the operation of food chains and food webs.<span>&nbsp; </span>We will focus on food chains and food webs in Unit 2.<span>&nbsp;&nbsp; </span>Here, in this first unit, our objective is just to introduce the following basic ideas:</font></p>
<ul>
	<li>
		<font size="2">Mercury is toxic in very small quantities.</font></li>
	<li>
		<font size="2">Mercury occurs in a number of forms in nature.<span>&nbsp; </span>One of these, forms, methylmercury, can be absorbed by living things and is very toxic.</font></li>
	<li>
		<font size="2">In the Northeast, most mercury arrives through the air.</font></li>
	<li>
		<font size="2">Methylmercury is the byproduct of metabolism by anaerobic bacteria, typically living in an acidic envi-ronment with access to carbon and sulfur.</font></li>
</ul>
<p>
	<font size="2">The Essential Activity, <a href="http://participatoryscience.org/mercury-watersheds/essential-activity-why-do-we-care-about-mercury">&ldquo;Why Do We Care About Mercury?,</a><span style="font-family: arial,sans-serif;"><a href="http://participatoryscience.org/mercury-watersheds/essential-activity-why-do-we-care-about-mercury">&rdquo;</a> focuses</span> on the first of these ideas and introduces the second one.<span>&nbsp; The Optional Activity</span>, <a href="http://participatoryscience.org/mercury-watersheds/optional-activity-concentrations">&ldquo;Mercury Concentrations,&rdquo;</a> reinforces the second idea and develops the third and fourth ones.</font> Optional Activity <a href="http://participatoryscience.org/mercury-watersheds/optional-activity-mapping-us-mercury-emissions">&quot;Mapping U.S. Mercury Emissions&quot;</a> helps develop the second idea, and <a href="http://participatoryscience.org/mercury-watersheds/optional-activity-road-toxicity">&quot;The Road to Toxicity&quot;</a> develops the last of these ideas.</p>
