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Sediment-al Journey: Measuring Metal Concentrations in Soil Beside Urban Waterways

This article is from Issue Freshwater - Vol. 18 No. 1.

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Chemicals from auto emissions, industrial processes, and urban development are found in most urban areas. Two of the chemicals found most abundantly in urban areas are calcium and lead.  The calcium comes from all the concrete and the lead comes from oil-based fuels. These chemicals bind to the soil and can be carried by waterways.  Often after flooding events, these chemicals are deposited in riparian areas along the waterways.  Scientists in this study wanted to find out the chemical content in these riparian sediments and what that content can tell us about how urban land is being used.

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Reflection Section Answer Guide

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"Thinking About Science Themes" covered in this article:
In 1980, the National Science Foundation created a network of research locations to study how ecosystems change over a long period of time. This network is called the Long Term Ecological Research (LTER) Network. The United States has 26 of these areas, which includes one in Puerto Rico and two in Antarctica. The research being done at these locations is unusual because it focuses on changes that are happening over a long period of time. From a scientific perspective, long-term research provides information that is impossible to discover in any other way. One of these research locations is the Baltimore Ecosystem Study. Scientists working with the Baltimore Ecosystem Study seek to understand metropolitan Baltimore as an ecological system. The Baltimore Ecosystem Study involves scientists from the biological, physical, and social sciences. The LTER network enables a variety of scientists to work together. By working as a team, these different scientists can provide a much more complete picture of what is happening over time and why it is happening. One goal of the Baltimore Ecosystem Study is to understand how urban and suburban ecosystems change over a long period of time. In this study, you will learn what scientists are discovering about changes in the riparian areas that drain into Baltimoreís Middle Branch of the Patapsco River. This body of water is also known as Baltimore Harbor (figures 1 and 2).
Specific "Thinking About Science" Themes:
  • Scientific Topics
  • Uses and Benefits of Science

"Thinking About Environmental Themes" covered in this article:
Riparian areas are transition areas between waterways and land (figures 3 and 4). Riparian areas are ecologically important. They provide habitat for wildlife species and for plant species that grow in wet areas. When streams flow into rivers, the streams carry sediment into the rivers. Sediment is created by soil erosion. Soil erosion is caused by heavy rainfall from both the lands through which streams and rivers flow and the riverbanks of the waterways themselves. Riparian areas protect waterways from too much soil erosion and sedimentation, and they protect upland areas from flooding. Urban areas have a large amount of impervious (im pər vē əs) surface area. Concrete and asphalt are examples of impervious surfaces. Water cannot drain through impervious surfaces. Following rainfall or snowfall in urban areas, impervious surfaces cause rainfall or melted snow to enter waterways more quickly than it does in nonurban areas. Managers often take action to slow the rate of runoff into waterways and to protect streambanks from erosion (figure 5). In this study, the scientists wanted to learn about changes in urban riparian areas in metropolitan Baltimore. The scientists studied the sediment that is deposited onto riparian areas during high streamflows. They wondered about the sedimentís chemical content, including trace chemicals like lead and plant nutrients like calcium. The scientists wanted to discover what the sedimentís chemical content indicates about urban land use.
Specific "Thinking About the Environment" Themes:
  • Ecosystems
  • Riparian Forests

NSE Standards covered in this article:
  • Abilities necessary to do scientific inquiry (A)
  • Diversity and adaptations of organisms (C)
  • Nature of science (G)
  • Populations and ecosystems (C)
  • Populations, resources and environments (F)
  • Properties and changes of properties in matter (B)
  • Regulation and behavior (C)
  • Risks and benefits (F)
  • Science as a human endeavor (G)
  • Structure and function in living systems (C)
  • Understandings about scientific inquiry (A)