This post serves as an extension of the previous one, providing a more detailed overview on understanding the totality of the environment.

The Earth consists of different spheres – the atmosphere, hydrosphere, lithosphere, and biosphere. How pollutants enter each of the different spheres are often not in isolation of each other, and as mentioned before exists as part of a continuum. After a pollutant gets emitted, it enters into the different spheres of earth and has the potential to be transported around. Nitrous and sulfur oxides for example are one of the more prevalent pollution sources. This blog post will use nitrous oxides and sulfur oxides as an example to further discuss its pathways.

The journey of a pollutant starts at its source. Sources are categorised into two main categories: point and non-point/ diffuse sources. Point sources are easier to identify as the origins stem from a single place. An example of a point source of nitrous oxides and sulfur oxides are smokestacks from industrial factories (National Geographic Society, 2019). Non-point or diffuse sources are the opposite, whereby it is difficult to identify a targeted locale. Rather, pollutants are released in a wide area. A city street or pasture lands are examples of such sources, where rainfall causes runoffs into sewers and subsequently nearby rivers (National Geographic Society, 2019).

From the source, pollutants are emitted into the environment. The pollutant then gets into the atmosphere or hydrosphere, where due to the chemistry of the environment, will cause different reactions to occur. Continuous process of chemical reaction also occurs as the pollutant is being transported to its sink. At the sink, depending on the environmental condition again (for example temperature, availability of other chemical compounds, the stability of chemicals, changes in environmental condition), the pollutants may again be remobilised, transformed and transferred. In the case of nitrous and sulfur oxides, once emitted into the atmosphere, oxidation reactions result in the transformation into nitrate acids. Nitrate acids in the atmosphere can then be deposited into the hydrosphere and lithosphere through acid depositions like acid rain.

Pollutants that are generated due to such processes alters natural environments like forests, hence disturbing the ecology or natural ecosystem processes. For example, deposition of acid causes alteration to soil pH which disrupts plant growth. These plants provide important microhabitats in the forest ecosystem for the survival of a diverse variety of organisms. For the past millions of years, species have evolved and adapted to live in such natural conditions, hence, a slight change in their environment threatens their survival. This is one contributing factor that leads to species extinction (Schreiber & Newman, 1988).

References:

National Geographic Society. (2019, July 15). Point Source and Nonpoint Sources of Pollution. Retrieved September 07, 2020, from https://www.nationalgeographic.org/encyclopedia/point-source-and-nonpoint-sources-pollution/

Schreiber, R., & Newman, J. (1988). Acid Precipitation Effects on Forest Habitats: Implications for Wildlife. Conservation Biology, 2(3), 249-259. Retrieved October 2, 2020, from http://www.jstor.org/stable/2386315

Shapley, P. (n.d.). Causes of Acid Rain. Retrieved September 07, 2020, from http://butane.chem.uiuc.edu/pshapley/Environmental/L24/1.html