Chapter three of the book Acid in the Environment: Lessons Learned and Future Prospects was written by Kathy Fallon Lambert, Charles T. Driscoll, and Limin Chen (2007) and it is titled “Acidic Deposition: Sources and Ecological Effects”. This chapter together with the article “Acid rain and its ecological consequences” written by Madhoolika Agrawal and Anita Singh and which appeared in the 29th volume of the Journal of Environmental Biology describe the formation of acid rain and its consequences on the environment. These two sources of literature are very relevant to my research question: How does acid rain affect soil PH?
The three authors of chapter 3 in the book described above are professionals with impeccable records in Environmental Engineering. Kathy Fallon Lambert has done a lot of work relating to ecosystem science, both as the founder of Ecologic: Analysis & Communications and during her tenure as the executive director of Hubbard Brook Research Foundation. As a result of her good work, she received the US EPA Environmental Merit Award. Besides, she is a Leopold scholar and a Switzer fellow.
On his part, Charles T. Driscoll, an Environmental Systems Engineering Professor, teaches at the Syracuse University where he doubles up as the Director of the Centre for Environmental Systems Engineering. Limin Chen is employed at Systech Engineering, Inc., as a Water Resources and Environmental engineer and she has done a lot of work on forest ecosystems. All the three authors are PhD holders in their respective fields and they have done a lot of research studies on environmental engineering projects.
Madhoolika Agrawal and Anita Singh, the authors of the journal article, are distinguished researchers and scholars working at the Ecology Research Laboratory in the Department of Botany, Bañaras Hindu University, India. The two scholars have done a lot of research on Environmental Engineering projects and they are widely published.
The third chapter in the book Acid in the Environment: Lessons Learned and Future Prospects selected for this study is divided into four major sub-topics, namely: 1) Acidic deposition, 2) Effects of acidic deposition on ecosystems, 3) Ecosystem recovery, and 4) Recovery of acid-sensitive ecosystems with future decreases in emissions. On the other hand, the journal article has several subtopics running in an essay format on ten pages.
I will endeavor to read through the two literatures with the aim of gathering information on the effects of acid rain on soil pH. Specific emphasis will be given to subtopic 2: Effects of acidic deposition on ecosystems in the book and another one titled Effects of acid rain on soil in the journal article.
Driscoll et al. (2007, pp. 34) acknowledge that acidification of soil has a negative impact on the soil’s ability to neutralize any further deposition of acids. Acidified soils are incapable of supporting the growth of plants because this process deprives the soil of the nutrient cations, such as, potassium, calcium, and magnesium.
Furthermore, the soil is invaded with sulfur and nitrogen, not forgetting the accumulation of dissolved inorganic aluminum. Driscoll et al. (2007, pp 37) noted that the soil acquires nutrient cations by weathering of the rocks and minerals, and to some extent, atmospheric deposition.
In circumstance of low weathering rates, the forest ecosystems are normally vulnerable to acidic deposition because of low content of base cations. Since acidification of soil accelerates dissociation of nutrient cations from their compounds and thereafter subjects them to leaching, the quality of the soil can be maintained only if there is equal replenishing of these cations by weathering of rocks and mineral (Driscoll et al. 2007, pp. 38).
On their part, Singh and Agrawal (2008, pp. 16) state that rain is considered acidic if its pH value is below 5.6 and the level of concentration of hydrogen ions (H) is above 2.5. Furthermore, the authors agree that Sulphur dioxide (SO), ozone (O), and oxides of nitrogen are some of the major components that are involved in the formation of acid rain.
With the help of sunlight and vapors, SO and NO interact and react to form sulphuric acid and nitric acid mists, which when condensed become aerosol droplets. Singh and Agrawal (2008, pp. 18) concede that the increased exchange between nutrient cations and hydrogen ion is as a result of the presence of acids in the soil.
This exchange is responsible for the liberation of the (magnesium, potassium, and calcium) cations in the soil, which become vulnerable to leaching. The freed cations and the acid-generated sulphates are easily leached out in soil solutions. Nutrient cycling and poor decomposition are also as a result of soil acidification.
Various research studies have indicated that the decomposition of litter generated from cellulose-rich plants, such as, birch, spruce, and spine, is adversely slowed by generous acidification. It has also been demonstrated that the structural diversity of Boreal forest ecosystems is highly dependant on the quality of soil and therefore acidification can destroy these forest ecosystems (Singh & Agrawal 2008, pp. 18)
References
Driscoll, C. T., Lambert, F. K. & Chen, L. 2007, “Acidic Deposition: Sources and
Ecological Effects”, in G R Visgilio & D M Whitelaw (eds), Acid in the Environment: Lessons Learned and Future Prospects, Springer, New York, pp. 27–58.
Singh, A. & Agrawal, M. 2008, “Acid rain and its ecological consequences”, Journal of Environmental Biology, vol. 29 no. 1, pp. 15–24.