Mercury is an element of the earth and can also come naturally from humans. Mercury continually rises to the surface of the Earth's crust, due to the high temperature of the Earth's mantle, and this can make mercury a very mobile source. Surface rocks may contain high levels of concentrated mercury, which can raise levels of mercury emission standards. Natural sources can come from the earth's crust, volcanoes and erosion. Others come from weather, floods and forest fires. This type of contamination is beyond human control and must be considered part of the mercury levels in the atmosphere. Scientists to date have struggled to separate the two factors, from human involvement to natural mercury production. Other emissions of mercury into our atmosphere are anthropogenic, meaning the influence of nature by humans. Some of these included mines, coal plants, cement manufacturing plants, caustic soda manufacturing plants, mineral processing, medical waste, chemical manufacturing plants, and forest fires. Volcanoes can vary in how much mercury they release into the atmosphere, and it can depend on whether they are erupting or degassing. Researchers measure mercury emissions based on the ratio of Hg/SO2 (mercury/sulfur dioxide), and this is found in the columns of volcano eruptions. Some researchers say this approach is inaccurate, due to a lack of data and the instability of volcanoes. Some researchers say this area needs further research, in order to get a better read on the actual amount of mercury being put into our atmosphere. Bidirectional flows or simply flow means that gaseous mercury can escape into the air or go down. Small amounts of degassing can put mercury gas lower in the atmosphere, which can have a long-lasting effect...... middle of paper...... 1 pg(s) 45-61Woodruff, L. , Cannon, W. (2010). Immediate and long-term effects of fire on total mercury in forest soils of northeastern Minnesota. Environ Science Technolgy.44(14):5371–5376. Lee, Yonggoo and Rahman, Md Moklesur and Kim, Guebuem and Han, Seunghee. (2011). Mass balance of total mercury and monomethylmercury in coastal settlements of a volcanic island: significance of underwater groundwater discharge. Environmental sciences and technologies. www.biomedsearch.com/nih/Mass-balance-total-mercury-monomethylmercury/21973173.html(5)Pirrone, N., Cinnirella, S., Feng, X., Finkelman, R.B., Friedli, H.R., Leaner, J ., & Telmer, K. (2010). Global emissions of mercury into the atmosphere from anthropogenic and natural sources. Atmospheric Chemistry and Physics, 10(13), 5951-5964. World Coal Organization. http://www.worldcoal.org/coal/uses-of-coal/coal-combustion-products/