Sulfur Travels By Land and Air
Certain types of bacteria perform photosynthesis using hydrogen sulfide (H2S) instead of water (H2O). These bacteria most likely existed on earth before there was an abundance of atmospheric oxygen to use. The early earth mainly consisted of volcanic lava, which contains large amounts of sulfur.
Sulfur is exchanged locally and globally. In the local exchange, sulfur is released from soil deposits by weathering and decomposition of organic and inorganic soil and rock deposits. Sulfur exists in the air as hydrogen sulfide and sulfur dioxide. Sulfur dioxide falls back to the earth in rain. However, it becomes sulfuric acid (H2SO4) when it is combined with water. This makes the rainwater acidic. Most of the sulfur in air gets there by natural means. However, the burning of fossil fuels and coal by humans adds a large amount of extra sulfur to the atmosphere. What other cycle that we have already discussed contributes to acid rain?
Phosphorus Doesn’t Have Wings
mentioned how glucose is used in the body to make energy in the Krebs
Cycle. The chemical form of
energy produced in the Krebs Cycle is
adenosine triphosphate (ATP).
This is an adenosine molecule with a chain of three phosphate (PO4)
groups attached to it. In
addition to being contained in ATP, phosphate groups make up the
backbone of DNA and RNA molecules.
In order to continually make ATP, DNA and RNA, the body needs a
large supply of phosphate. Phosphate
is supplied to the body through the phosphorus cycle.
Most of the phosphorus present on earth is located in rocks. The processes of weathering and erosion release phosphorus into the ecosystem. Once phosphorus gets released into the ecosystem, it gets taken up by plants and eventually passed through the food chain. Humans can disrupt the phosphorus cycle through the disposal of waste products and by using fertilizer. Waste products end up in the sewage system where phosphorus becomes immobilized. In fertilizer, phosphorus is stored in a compound called phosphate. Phosphate reacts with other elements in the soil such as calcium, iron and aluminum and becomes immobilized.
You should have
noticed that human actions in industry and agriculture have a major
effect on the all of the cycles we have discussed.
Here is a summary of the major problems: