Hello everyone!
In my last post, I gave a brief introduction to what Acid Mine Drainage (AMD) is, and today, I will be delving deeper into the ecological impact of this phenomenon.
AMD affects various aquatic systems by various direct and indirect pathways. Major impacted areas are rivers, lakes, estuaries, and coastal water. Due to complexity, it is often hard to accurately quantify and predict its effect but they can be categorized as acidity, metal toxicity, sedimentation, and salinization. Some major effects of AMD is better illustrated by the chart below (Gray, 1997).
Once the acid is released into the environment, dissolving more metals, they become bioavailable to organisms. In water, fish are exposed directly to the bioavailable metals resulting in the larger intake of these metals through their gills. This could lead to impaired respiration from chronic or acute toxicity. Fish are also exposed indirectly through the ingestion of contaminated sediments and food items leading to bioaccumulation (Jennings et al., 2008). In the presence of alkali rocks nearby, the acid will react and lead to the formation of precipitate iron hydroxide (Fe(OH)3), also known as yellow boy (Coil et al., 2014). They may coat the surface of stream sediments and streambeds destroying habitats, reducing the availability of clean gravels for spawning, and reducing food items such as benthic macroinvertebrates. This is depicted in the picture below (Petterson, 2016).
Due to the toxic conditions of elevated concentration of metals and low pH, water contaminated by AMD are devoid of most living creatures. AMD can also leach into the groundwater decreasing pH and bringing in dissolved metals. Not just aquatic systems, AMD can cause nearby soil to be more acidic which can result in plant health implications and soil diversity. Low pH tolerant plants may dominate and species diversity may drop.
As with all AMD sites, the rocks will remain capable of generating acid for an unknown number of years, perhaps even until the end of time. Some Roman mining sites in Great Britain are still producing problematic AMD even after 2000 years of the completion of mining. It is almost virtually impossible for an area after being contaminated by AMD to revert back to its original state. It is thus imperative for a proper and accurate assessment to be done on-site before proceeding with mining activities if not we should consider if mining really is necessary.
That brings me to the end of this post!
See you guys soon!
References
Coil, D., McKittrick, E., Mattox, A., Hoagland, N., Higman, B., & Zamzow, K. (2014, October 29). Acid Mine Drainage. Retrieved September 25, 2020, from http://www.groundtruthtrekking.org/Issues/MetalsMining/AcidMineDrainage.html
Gray, N. F. (1997). Environmental impact and remediation of acid mine drainage: A management problem. Environmental Geology, 30(1-2), 62-71. doi:10.1007/s002540050133
Jennings, S. R., Neuman, D. R., & Blicker, P. S. (2008). Acid Mine Drainage and Effects on Fish Health and Ecology: A Review. Retrieved September 28, 2020, from https://www.earthworks.org/cms/assets/uploads/2018/12/55-S.R.-Jenning-et-al.-2008.-Acid-Mine-Drainage-and-Effects-on-Fish-Health-and-Ecology-A-Review.pdf.
Petterson, D. (2016, May 19). Permanent solution to acid mine drainage in sight. Retrieved September 28, 2020, from https://infrastructurenews.co.za/2016/05/19/permanent-solution-to-acid-mine-drainage-in-sight/
