Elevated Concentrations of Methyl Mercury in Streams after Forest Clear-cut: A Consequence of Mobilization from Soil or New Methylation?
Ulf Skyllberg, Mattias Björkman Westin, Markus Meili, and Erick Björn
This article, published in the journal Environmental Science and Technology investigates the relationship between neurotoxin Methyl Mercury (MeHg) and forestry practices. Hg is formed from the process of combustion of fossil fuels. Long range transport by the atmosphere moves the Me to other locations where it is deposited. The inorganic Hg transforms into MeHg in areas characterized by wetlands and forested regions. MeHg can bioaccumulation in organisms meaning the toxic MeHg is absorbed faster than the organism can remove it. Increased Hg in the environment has also been linked to forest logging actives. The article’s topic is the impacts of inorganic compounds resulting from forestry practices on environments and organisms.
The question this article seeks to answer is to confirm the causal relationship between clear-cutting forest and increasing MeHg concentrations as well as determining if the elevated concentrations of MeHg were a result of the mobilization of Hg is the soils or from new production of Hg. The authors used acts, behaviors or events and detached observations to measure data in regards to the contents of streams. The data was collected at 47 unique forest stands that were subjected to clear-cutting from 1998-2007 and 10 mature forest stands with trees >70 years old. A criterion for the sites was each had to have a consistent stream with a width of .5-1m at the sampling site. No data about the area draining into the stream was collected.
The sites were sampled once during a two-week period in August of 2007. No major precipitation event took place during the two-week sampling period. The data was analyzed quantitatively using statistical analysis to compare data from the clear-cut areas by age and to the reference site. An ANOVA, Analysis of Variation, was used to determine if the data would be a part of one population. This means it was testing to see if there were any significant differences in the data. It was concluded that there was a significant difference meaning clear-cutting was tied to increases in MeHg.
This research was executed well with detailed descriptions of how data was collected and the procedures that the researchers used. I felt that more data could have been collected during a separate two-week period in order decrease the margin for error. The graphs showed multiple data tables in a succinct manner that made them easy to interpret. Overall I felt the article was clear and concise. The aspect that I would highlight would be that there are many implications for removing forests. Not only does it decrease CO2 sequestration, increase erosion and increase desertification it adds harmful neurotoxins to the environment which damage organisms in areas downstream from the clear-cutting.
Ulf Skyllberg, Mattias Björkman Westin, Markus Meili, and Erick Björn. Elevated Concentrations of Methyl Mercury in Streams after Forest Clear-cut: A Consequence of Mobilization from Soil or New Methylation? Environ. Sci. Technol. 2009, 43, 8537-8541.