Summary of supply, trade and demand information on mercury
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3.1.4.4 All non-ferrous ores combined 142. Based on data on mercury content of non-ferrous ores provided in the UNEP “Toolkit for identification and quantification of mercury releases” (UNEP, 2005), it has been roughly estimated that 1,000-1,500 metric tonnes of mercury every year are released from these ores by refining processes (Maxson, 2006). Most of that mercury goes to the atmosphere (Wu (2006) reported as much as 200 metric tonnes from zinc refining in China alone), but much is captured and recovered, as described above, or disposed of. Simply adding the various non-ferrous sources, and recalling that there are some ferrous sources as well, gives an estimated 300-400 metric tonnes of mercury recovered globally from zinc, gold, copper, lead and silver refining in 2005, as summarised in Table 10 below. 143. It should be mentioned that the preceding by-product mercury summary does not include the approximately 4,000 metric tonnes of accumulated Russian mining wastes (possibly mostly from the Chelyabinsk zinc smelter) transported to Kyrgyzstan for refining, starting in 2004. This contract concerned a specific quantity of waste accumulated in the Russian Federation over several years, but suggests that significant (and likely increasing) quantities of mercury continue to be removed from Russian ores (many of them having high trace mercury content) in compliance with regulatory requirements and responding to customer needs. It has been estimated that approximately 2,000 metric tonnes of mercury are being extracted from these wastes at the Khaidarkan facility, after which the mercury is reportedly owned and marketed by Kyrgyzstan (Noruzbaev, 2004).
3.1.5 By-product mercury from natural gas cleaning 144. Another source of by-product mercury, although not related to mining per se, is natural gas. Most natural gas contains some mercury in trace quantities. In many regions of the world, depending on geology, such as the Netherlands, North Sea, Algeria, Croatia, etc., the mercury concentrations are high enough to cause serious equipment problems during processing.7/ Pirrone et al. (2001) reported that “a reduction of mercury to below 10 μg/m3 has to be obtained before the gas can be used, although mercury is sometimes removed from gas even at far lower concentrations”. It is estimated that 20-30 metric tonnes of mercury are recovered yearly from natural gas wastes in the European Union (Maxson, 2006). 145. The data in the following table suggest that mercury is removed from natural gas in such diverse regions as South Africa, the Far East and Sumatra. However, there is no information as to how many of these wastes are treated to separate the mercury. It has been estimated that other countries recover about half of the amount of mercury recovered from gas cleaning wastes in the European Union in a typical year. If so, then about 10 metric tonnes of mercury are presently produced from gas wastes outside the European Union.
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Specifically, mercury condenses as liquid mercury on the inside of piping and equipment, or it amalgamates with aluminium (most problematic) and other metals (except iron), gradually corroding and weakening the metals, which has resulted in serious industrial accidents.