Mercury Deposition Network

National Atmospheric Deposition Program Mercury Deposition Network... 

FIGURE 2.4 Location of Mercury Deposition Network (MDN) sites in 2006. 

FIGURE 2.5 a) Wet THg deposition at the Mercury Deposition Network (MDN) sites for 2004 and b) temporal patterns in the concentration of THg in precipitation at a MDN site, based on weekly observations. 

The NADP analyzes the constituents important in precipitation chemistry, including those affecting rainfall acidity and those that may have ecological effects. The Netwoik measures sulfate, nitrate, hydrogen ion (measure of acidity), ammonia, chloride, and base cations (calcium, magnesium. potassium). To ensure comparability of results, laboratory analyses for all samples are conducted by the NADP s Central Analytical Lab at the Illinois State Water Survey, A new subnetwork of the NADP, the Mercury Deposition Network (MDN) measures mercury in precipitation. 

It was quickly realized that the mercury species to be found in greatest abundance in precipitation was ionic mercury (e.g., Fogg and Fitzgerald, 1979). Some typical values of total mercury in precipitation are shown in Table 10. Extensive databases of precipitation mercury concentrations are available from monitoring networks in the US, Canada, and Nordic countries (e.g., US Mercury Deposition Network http //nadp.sws.uiuc.edu/ mdn). The discrepancy between the dominant gas and precipitation phase species implied a process of oxidation of elemental mercury in the atmosphere and its subsequent scavenging as being a major component of the mercury cycle. Since the initial work, and partially in response to... 

Bones are actually living protein networks to which minerals attach themselves. Not aU of the minerals deposited on bones are essential to bone building. There are at least two dozen elements in bones that have no known function in the human body, as well as a handful of nonessential elements, such as boron, strontium, silicon, barium, bismuth, and arsenic (yes, arsenic), that are believed to do some good. Five toxic elements—lead, cadmium, mercury, polonium, and radium—are often found in human bones. As long as they are stabilized in the bones, they do no apparent harm. 

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