Project Amazonia: Monitoring - Land
Although the state of the Amazon cannot be completely or directly predicted by the soil, monitoring the soil by analysis of pH and ion content can provide us with information and data that will help us to better monitor and analyze the overall state of the Amazon. Since the soil characteristics are critical to the ability of many species in the Amazon to proliferate, soil quality must be monitored. Before beginning analysis, the soil must be prepared correctly in order to obtain accurate information. Below is a step-by-step list of how to prepare the soil.
Soil Preparation:
1. Drying
- expose as much of the surface of the soil to circulating air as possible and by evaluating the drying temperature (not to exceed 38°C to preserve the physiochemical properties of the sample)
- soils should be dried as rapidly as possible to minimize microbial activity
2. Crushing
- crush by hand or by a stainless steel mechanical crusher
- Filter through a 2mm screen to remove rocks and create a uniform sample
3. Divide samples by volume into equal portions
The soil sample is now ready for testing and analysis. Soil testing can test for three types of information: the pH of the soil, the ion content, and the presence of contaminants.
The pH has significant importance in Amazonian soil in relation to ion solubility and toxicity. For example Al3+ ions are more soluble in acidic pH and are therefore more toxic to plants in lower pH soils. However, Amazonian soil is naturally acidic, as most basic compounds have been washed away by leaching, and indications seem to suggest that these levels are currently not significantly affected by industrial output. The average pH of the Amazon rainforest is in the range of 4.17-4.94.2
To test for the pH of soil1:
Using a pH meter with two separate electrodes, measure the pH of a “soil slurry” of 0.01M CaCl2 2H20* in a 1:2 ratio (soil:CaCl2H20).
*Recommended for sandy soils or soils with low cation exchange. Usually causes the pH to appear 0.3 to 0.5 lower; one should take this into account.
Ions are critical to the biological processes of plants and animals and could possibly be used as indicators to the health of the rainforest.
To test for the presence of Na+, Mg2+, and K+ ions1:
Add 0.01M CaCl2 to soil sample and shake it for two hours (mechanically). Next, centrifuge and collect the supernatant and analyze for elemental composition. Then, use plasma emission spectrometry (with emission lines, etc.) to determine the percent of Na+, Mg2+, and K+ ions
Contaminants in the soil, such as mercury, pesticides, and cyanide, adversely affect the biological systems of the flora and fauna of the Amazon Rainforest. For example, contaminants are known to weaken the stems of contaminated vegetation, cause deformation in leaves, and cause reproductive failures. Animals that digest these plants or come into contact with the ground (i.e. burrowers) will then suffer complications such as problems to the respiratory system and brain damage. Contaminants can be introduced in many ways, especially mining. At the refinery rocks being mind are sprayed with cyanide or mercury to separate the gold particles from the rock. However, careless containment procedures lead to the release of these chemicals into the natural surroundings. Once in nature, these contaminants inhibit plant growth and animal immunity, killing the flora and fauna.
To test for mercury contaminants in soil3:
Use an active flux chamber, consisting of “a stainless steel cylinder covered with a Plexiglas dome. Air is delivered from the breathing zone into the flux chamber with a low-flow pump so that a circulating flow pattern is obtained in the dome. The air inflow is set so that the inside temperature approximates the ambient soil temperature. A pressure relief port prevents the interior pressure from exceeding ambient conditions while the atmosphere in the flux chamber equilibrates. Upon equilibration, air temperature and mercury vapor concentration are measured in the center of the dome. The mercury flux is then calculated from the pump flow rate, the net concentration in the flux chamber, and the surface area enclosed by the chamber.”3
1: Benton Jones, J., (2001). Laboratory Guide for Conducting Soil Tests and Plant Analysis, CRC Press
2: Negreiros, G. H. de; Nepstad, D. C. 1994, Mapping deeply rooting forests of Brazilian Amazonia with GIS, Proceedings of ISPRS Commission VII Symposium - Resource and Environmental Monitoring, Rio de Janeiro. 7(a):334-338.
3: Energy and Environmental Research Center, 2000, University of North Dakota, http://www.eerc.und.nodak.edu/summaries/MMF.htm
