Sediment Leaching

Sediment Leaching

In any given sample of soil, many organic and inorganic substances can be found.  In order to measure the concentration or amount of these substances, scientists sometimes use a separation technique known as sediment leaching.  In this, the metals are washed from the sample, and collected in a liquid.  This liquid, or eluate, is processed via atomic absorption (AA) spectroscopy to determine the concentrations.  The liquid eluate can also give information as to how good the sample is at neutralizing acids.  This leaching process has been modified and employed by metal, biological, and food processing industries alike.  Recently, in our Environmental Chemistry class, we tested three samples of "sediment": clay from either Arizona or Georgia, soil collected from Tecolote Canyon, and limestone.  The sample collected from Tecolote was within walking distance from our school, so our results have the potential to affect us all directly.  We measured the concentrations of the following ions: potassium, cadmium, copper, zinc, and magnesium.  

Our results indicate that limestone is the best at neutralizing acid, followed by our Tecolote sediment, and clay.  Furthermore, cadmium showed up in minuscule amounts in all the samples, which is good news, because of its inherent toxicity.  Basic compounds such as magnesium and potassium were found in higher amounts in the most neutralizing sample, limestone.  These results enforced previous research

This experiment matters because of the environmental implications a soil sample with high metal concentrations has. For example, plant growth is often greatly reduced in basic soil, because water and essential nutrients are not able to penetrate the soil.  This can cause stunted growth and nutrient deficiency.  Also, nutrient concentration and basicity of soil can counteract the affects of acid rain on our planet.  For more information on this topic, feel free to check out the following websites:

http://www.iss.it/publ/anna/2008/3/443252.pdf

http://www.britannica.com/EBchecked/topic/333492/leaching

http://pesticidestewardship.org/water/Pages/Leaching.aspx