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Organic geochemistry

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Organic geochemistry is the scientific study of how living organisms impact and change the Earth. This field focuses on the composition and origins of organic matter found in rocks and bodies of water. By analyzing these materials, scientists can understand the complex relationship between life and the physical world.

Carbon cycle-cute diagram
Carbon cycle-cute diagram

It provides a way to track how biological processes move through the Earth's systems over vast periods of time. This includes studying the movement of elements within the carbon cycle.

To understand these processes, geochemists use several sophisticated analytical methods. They often use mass spectrometry or Raman spectroscopy to examine the structure of samples. These tools allow researchers to look at tiny details in a highly sensitive way. They may also use gas chromatography-mass spectrometry, or GC-MS, to analyze complex mixtures. This method is particularly useful for studying coal or identifying pollutants.

Carbon-13
Carbon-13

Other techniques include fluorescence spectroscopy, which is used to examine organic matter in water. Because dissolved organic matter is typically fluorescent, this method helps scientists see it clearly.

One major area of study involves petroleum and its geological origins. Geochemists examine petroleum-inclusions, which are tiny droplets of fluid trapped inside geological samples. By comparing these to dated samples, they can determine the age of the petroleum and the surrounding rock. They also look at the ratio of oil to gas and the viscosity of the fluid. These differences are usually attributed to the specific rock source of the sample. Scientists also use carbon isotope analysis to study petroleum. By examining the ratio of carbon isotopes, they can compare findings to known carbon-based structures to identify the deposit's composition.

Coal provides another important subject for organic geochemists. The formation of coal, known as coalification, results from the selective degradation of plant materials. While some material breaks down, other parts are preserved to form coal macromolecules. These macromolecules are usually derived from biopolymers found in wood, spores, and algae. To find the age of these sediments, scientists use isochron dating. This involves examining the ratio of parent to daughter isotopes of uranium within the coalified samples.

Isochron
Isochron

This method has allowed researchers to date certain samples back to the Late Cretaceous Period.

The history of this field is closely tied to the work of Alfred E. Treibs. He is often called the "father of organic geochemistry." In 1936, Treibs isolated metalloporphyrins from petroleum. Metalloporphyrins are highly stable organic compounds that are derivatives of substances like hemes. His discovery showed that these structures originated from chlorophyll. This was a major breakthrough because it established the biological origin of petroleum. Before this, the exact source of petroleum was not well understood.

Organic geochemistry also plays a vital role in environmental science and microbiology. Scientists use biomarkers, which are fossil organic molecules, to find signs of past or present life. These biosignatures have helped discover new microbial life in oceans, lakes, and hydrothermal systems. The field also studies the impact of human activity on the environment. For example, geochemists analyzed samples following the Exxon Valdez oil spill to understand oil-spill chemistry.

They also study how agricultural waste, such as animal manure and sewage, changes the physical properties of soil.

Beyond the ground and water, this science extends to the atmosphere and even space. Geochemists study organic aerosols, which are tiny particles of insoluble material in the lower atmosphere. These aerosols can lead to smog, rain acidification, and climate forcing. They also play a role in the natural carbon cycle. In space, researchers have used these techniques to search for signs of life in the first samples of Lunar dust. By studying life in extreme environments on Earth, such as hydrothermal vents, scientists can better understand the possibilities for life on other planets.

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File:Carbon cycle-cute diagram.jpeg
Carbon cycle-cute diagram.jpeg
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Carbon-13.svg
File:Isochron.jpg
Isochron.jpg
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