Mercury Hazards to Living Organisms - Chapter 2 pptx

The atmosphere plays an important role in the mobilization of mercury, with an estimated 25.0 to 30.0% of the total atmospheric burden of anthropogenic origin USNAS, 1978.. The global an

Mercury Uses and Sources

Mercury is a metallic element easily distinguished from all others by its liquidity at even the lowest temperatures occurring in moderate climates (Anon., 1948a) Mercury was unknown to the ancient Hebrews and early Greeks; and the first mention of mercury was by Theophrastus, writing around

300 BCE, stating that mercury was extracted from cinnabar by treatment with copper and vinegar (Anon., 1948a)

The most important ore of mercury, cinnabar (mercuric sulfide), has been mined continuously since 415 BCE (Clarkson and Marsh, 1982) Historically, the five primary mining areas for mercury were the Almeden district in Spain, the Idrija district in Slovenia, the Monte Amiata district in Italy, and various locales in Peru, the United States (Ferrara, 1999), especially California and Texas,

as well as sites in Russia, Hungary, Mexico, and Austria (Anon., 1948a) The Almeden mines over the past 2500 years were the most important, having produced about 280,000 metric tons of mercury,

or about 35.0% of the estimated total global production of about 800,000 tons (Ferrara, 1999) Major producers of mercury now include the former Soviet Union, Spain, Yugoslavia, and Italy (USPHS, 1994) In the United States, mercury consumption rose from 1305 metric tons in 1959

to 2359 tons in 1969 (Montague and Montague, 1971) Mining of mercury in the United States has decreased in recent years owing to decreasing demand and falling prices; the last operating mine in the United States that produced mercury as its main product closed in 1990 (Jasinski, 1995) In the late 1970s, world use of mercury was estimated at 10,000 to 15,000 metric tons annually (Boudou and Ribeyre, 1983), of which the United States used about 18.0% (Clarkson and Marsh, 1982) Accurate data on recent mercury consumption in the United States was difficult to obtain In 1987, the United States imported 636 metric tons; this fell to 329 tons in 1988 and

131 tons in 1989 (USPHS, 1994) Domestic production of mercury produced as a by-product was

207 metric tons in 1990, 180 tons in 1991, and 160 tons in 1992; during this same period, the United States imported 15 tons in 1990, 56 tons in 1991, and 100 tons in 1992 (USPHS, 1994) Atmospheric input of mercury has tripled over the past 150 years (Morel et al., 1998) The atmosphere plays an important role in the mobilization of mercury with 25.0 to 30.0% of the total atmospheric mercury burden of anthropogenic origin (USNAS, 1978), although more recent esti-mates of 67.0% are significantly higher (Morel et al., 1998) As a direct result of human activities, mercury levels in river sediments have increased fourfold since precultural times, and two- to fivefold in sediment cores from lakes and estuaries (Das et al., 1982) Analyses of sediment cores

of North American mid-continental lakes show that mercury deposition rates increased by a factor

of 3.7 since 1850, at a rate of about 2.0% annually (Rolfhus and Fitzgerald, 1995) During the past

100 years, more than 500,000 metric tons of mercury has entered the atmosphere, hydrosphere, and surface soils, with eventual deposition in subsurface soils and sediments (Das et al., 1982)

2.1 USES

Cinnabar (HgS), the main mercury ore, was used as a red pigment long before refining processes for elemental mercury were implemented (Wiener et al., 2003) In the 16th century, elemental mercury in combination with other compounds was considered a powerful medicinal agent (Anon., 1948a) Mercuro zinc cyanide [Zn3Hg(CN)8], also known as Lister’s antiseptic, was used in the early days of antiseptics, circa 1880s, in the form of “cyanide gavage” or “cyanide wool” in general surgery The stronger mercurial ointments were used to kill cutaneous parasites and to control itching Until the advent of antibiotics, mercury salts were a key treatment for syphilis and other venereal diseases Mercuric salts, especially the chloride and iodide, are powerful antiseptics and until the 1940s were routinely used in surgery to kill bacteria; however, their use was contraindicated

in patients with actual or potential renal inflammation, patients with scarlet fever (risk to throat), and eclampsia (uterus sensitivity) Mercurochrome, di-sodium hydroxy-mercuro dibromo fluores-cein, has been widely used in the United States and the United Kingdom as an antiseptic (Anon., 1948a), and is still sold in drugstores The volatility of mercury and many of its compounds causes their absorption by the lungs and is an unintended consequence of external application; this could account for the occurrence of chronic mercurial poisoning in certain trades Mercury is largely used in affectations of the alimentary canal and allegedly has value in many cases of heart disease and arterial degeneration In cases of intestinal obstruction, elemental mercury has been adminis-tered — up to 454.0 grams — without ill effects, the weight of the mercury being sufficient to remove the obstruction (Anon., 1948a)

In the period prior to the industrial revolution, mercury was used extensively in gold extraction and the manufacture of felt hats and mirrors; in the 1800s, it was used in the chloralkali industry, the manufacture of electrical instruments, and as a medical antiseptic; and since 1900, it has been used in pharmaceuticals, agricultural fungicides, the pulp and paper industry as a slimicide, and the production of plastics (Clarkson and Marsh, 1982) In 1892, the process of producing chlorine and caustic soda from brine (sodium chloride) was developed (Paine, 1994) Electrolysis of brine using a liquid mercury cathode to produce chlorine at the anode and a sodium–mercury amalgam

at the cathode is still used worldwide, with significant mercury contamination of the biosphere; however, the process is increasingly under replacement using mercury-free components (Paine, 1994) Until the late 1940s, mercury was used in the manufacture of fur felt hats from furs of rabbit, hare, muskrat, nutria, and beaver (Anon., 1948) Mercuric nitrate was used to remove fur from the hides The fur fiber is harvested and the hide, now denuded of fur and useless for hat manufacturing purposes, discarded A “mad hatter” syndrome was sometimes reported among workers in the manufacture of fur felt hats, with symptoms consistent with that of inorganic mercury poisoning, namely, tremors, excessive salivation, irritability, and excitement (Anon., 1948; Norton, 1986)

Mercury catalysts were used in the production of acetaldehyde, acetic acid, and vinyl chloride (Silver et al., 1994) The major use of mercury in the decade between 1959 and 1969 was as a cathode in the electrolytic preparation of chlorine and caustic (Nriagu, 1979; Paine, 1994; Table 2.1)

In 1968, this use accounted for about 33.0% of the total U.S demand for mercury (USEPA, 1980) During that same period, electrical apparatus accounted for about 27.0% of U.S mercury con-sumption; industrial and control instruments, such as switches, thermometers, barometers, and general laboratory appliances, 14.0%; antifouling and mildew-proofing paints, 12.0%; mercury formulations to control fungal diseases of seeds, bulbs, and vegetables, 5.0%; and dental amalgams, pulp and paper manufacturers, pharmaceuticals, metallurgy and mining, and catalysts, 9.0% (Table 2.1; USEPA, 1980) Mercury, however, is no longer registered for use in antifouling paints,

or for the control of fungal diseases of bulbs (USEPA, 1980) In India and other developing countries, however, HgCl2 is commonly used for the preservation of seeds and by farmers in fruit preservatives after harvest and to inhibit growth of microorganisms (Ghosh et al., 2004) In Kenya, certain soaps containing skin-lightening agents also contained high concentrations of inorganic

mercury (Ohno et al., 2004) And in Mexico and developing countries, merthiolate (an ethylmercury thiosalicylate compound) is currently used as a preservative in medical vaccines and as a skin antiseptic (Ohno et al., 2004)

Mercury in its various forms is still widely available in thermometers, fungicides, hearing aid and watch batteries, paints, mercurial drugs, antiquated cathartics, and ointments (Rumack and Lovejoy, 1986) The most recent uses of mercury and its compounds are in the manufacture of lighting fixtures such as fluorescent, metal halide, and mercury vapor lamps; dental amalgams; mining and reprocessing of gold; batteries; and paint manufacture (USNAS, 1978; Gonzalez, 1991; Sundolf

et al., 1994; Barbossa et al., 1995; Gustafson, 1995; Lacerda et al., 2004; Liang et al., 2004)

2.2 SOURCES

Major inputs of mercury to the environment are mainly from natural sources, with significant and increasing amounts contributed from human activities The atmosphere plays an important role in the mobilization of mercury, with an estimated 25.0 to 30.0% of the total atmospheric burden of anthropogenic origin (USNAS, 1978) The global anthropogenic atmospheric emission of mercury

is estimated at 900 to 6200 tons annually, of which the United States contributed 300 metric tons

in 1990 with 31.0% of the total from combustion of fossil fuels by power plants (Chu and Porcella, 1995) Atmospheric deposition is generally acknowledged as the major source of mercury to watersheds In northern Minnesota watersheds, for example, atmospheric deposition was the pri-mary source of mercury Geologic and point source contributions were not significant Transport from soils and organic materials may also be important, but the mercury from these sources probably originate from precipitation and direct atmospheric sorption by watershed components (Swain and Helwig, 1989; Sorensen et al., 1990) In Sweden, increased mercury concentrations in lakes are attributed to increased atmospheric emissions and deposition of mercury, and to acid rain (Hakanson

et al., 1990) Airborne particulates may contribute to the high mercury levels found in some marine dolphins and whales (Rawson et al., 1995) A total of 60 to 80 metric tons of mercury is deposited from the atmosphere into the Arctic each year; the main sources of mercury to the Arctic are Eurasia and North America from combustion of fossil fuels to produce electricity and heat (Pacyna and Keeler, 1995) However, elevated mercury concentrations in fish muscle (0.5 to 2.5 mg/kg fresh weight [FW]) from remote Arctic lakes over extended periods (1975 to 1993) are sometimes due

to natural sources of mercury (Stephens, 1995) Atmospheric deposition of mercury into the Great

Table 2.1 Industrial and Other Uses of Mercury in the United

States in 1959 and 1969

Use

Tons Percent Tons Percent

Electrical apparatus 308 23.6 644 27.3 Antifouling and mildew paints 121 9.3 336 14.2

a Sierra Club, New York 158 pp.

Source: Modified from Montague K and P Montague 1971 Mercury.

Lakes from sources up to 2500 km distant are documented at annual deposition rates of 15.0 µg

Hg/m2 (Glass et al., 1991) In South Florida, 80.0 to 90.0% of the annual mercury deposition occurs during the summertime wet season (Guentzel et al., 1995) Dry deposition processes are important for the flux of inorganic mercury and methylmercury to Swedish forested ecosystems; for methyl-mercury, the most important deposition route is from the air to a relatively stable form in litter (Munthe et al., 1995)

2.2.1 Natural Sources

The total amount of mercury in various global reservoirs is estimated at 334.17 billion metric tons; almost all of this amount is in oceanic sediments (98.75%) and oceanic waters (1.24%), and most

of the rest is in soils (Table 2.2) Living aquatic organisms are estimated to contain only 7.0 metric tons of mercury (Clarkson et al., 1984; Table 2.2)

The largest pool of methylmercury in freshwater biota is found in fish tissues (Porcella, 1994; Watras et al., 1994), and fly larvae are alleged to play an important role in mercury cycling from

feeding on beached fish carcasses, as judged by observations on blowfly (Calliphora sp.) adult egg layers, eggs, larvae, pupae, and emerging adults feeding on carcasses of brook trout, Salvelinus

fontinalis (Sarica et al., 2005) Specifically, methylmercury that accumulated in blowfly larvae is

retained in pupae but eliminated by adults following emergence (Sarica et al., 2005)

Mercury from natural sources enters the biosphere directly as a gas, in lava (from terrestrial and oceanic volcanic activity), in solution, or in particulate form; cinnabar (HgS), for example, is

a common mineral in hot spring deposits and a major natural source of mercury (Das et al., 1982) The global cycle of mercury involves degassing of the element from the Earth’s crust and evapo-ration from natural bodies of water, atmospheric transport — mainly in the form of mercury vapor — and deposition of mercury back onto land and water Oceanic effluxes of mercury are tied to equatorial upwelling and phytoplankton activity and may significantly affect the global cycling of this metal If volatilization of mercury is proportional to primary production in the world’s oceans, oceanic phytoplankton activity represents about 36.0% of the yearly mercury flow to the atmo-sphere, or about 2400 tons per year (Kim and Fitzgerald, 1986) Riverine input — with sediments containing up to 0.5 mg Hg/kg DW — of mercury influences mercury content of outer shelf areas

in southeastern Brazil where most of the offshore oil fields are located (Lacerda et al., 2004) Mercury finds its way into sediments, particularly oceanic sediments, where the retention time can

be lengthy (Table 2.2), and where it may continue to contaminate aquatic organisms (Lindsay and Dimmick, 1983) Estimates of the quantities of mercury entering the atmosphere from degassing

of the surface of the planet vary widely, but a commonly quoted figure is 30,000 tons annually (Clarkson et al., 1984)

Table 2.2 Amount of Mercury in Some Global Reservoirs

and Residence Time

Reservoir

Mercury Content a

(metric tons) Residence Time b

Ocean water 4,150,000,000 2000 years

Ocean sediments 330,000,000,000 > 1 million years

a From USNAS, 1978.

b Modified from Clarkson, T.W., R Hamada, and L Amin-Zaki 1984.

Mercury In J.O Nriagu (Ed.), Changing Metal Cycles and Human Health, p 285–309 Springer-Verlag, Berlin.

Mercury is emitted from volcanoes into the atmosphere, along with large quantities of lead, cadmium, and bismuth (Hinkley et al., 1999) About 6000 tons of mercury are discharged into the atmosphere every year from all sources (Fitzgerald, 1986); and from all volcanoes, about 60 tons

or about 1.0% of the total (Varekamp and Buseck, 1986)

Virtually all mercury in the Florida Everglades from natural sources (39.0% of the total mercury deposited) is attributed to release from the soil through natural processes, including microbial transformations of inorganic and organic mercury to methylmercury (Sundolf et al., 1994) Major sources of mercury in humans — other than residing in mercury-contaminated environments — include consumption of large predatory fish, such as tuna and swordfish, caught hundreds of kilometers offshore in clean ocean waters (Fitzgerald, 1986; WHO, 1990, 1991) The naturally elevated concentrations of mercury in these species is discussed in greater detail later

Terrestrial vegetation functions as a conduit for the transport of elemental mercury from the geosphere to the atmosphere (Leonard et al., 1998a) Estimated mercury emissions from plants in the Carson River Drainage Basin of Nevada — an area heavily contaminated with mercury from historical gold mining activities — over the growing season (0.5 mg Hg/m2) add to the soil mercury emissions (8.5 mg Hg/m2) for a total landscape emission in that area of 9.0 mg Hg/m2 In one

species (tall whitetop, Lepidium latifolium), as much as 70.0% of the mercury taken up by the

roots during the growing season was emitted to the atmosphere (Leonard et al., 1998a) Factors known to increase the flux of elemental mercury from terrestrial plants growing in soils with high (34.0 to 54.0 mg Hg/kg soil DW) levels of mercury include increasing air temperature in the range 20.0 to 40.0°C, increasing irradiance, increasing soil mercury concentrations, and increasing leaf area (Leonard et al., 1998b)

2.2.2 Anthropogenic Sources

In 1995, approximately 1900 metric tons of anthropogenic mercury entered the atmosphere, mostly (75.0%) from the combustion of fossil fuels (Pacyna and Pacyna, 2002) About 56.0% of global mercury atmospheric emissions came from Asian countries, with Europe and North America combined contributing less than 25.0%; gaseous elemental mercury (Hgo) comprised 53.0% of total atmospheric emissions, gaseous Hg+ 37.0%, and particle-associated mercury the remainder (Semkin et al., 2005)

Large-scale mining of mercury in North America ceased around 1990 because of low prices and stringent environmental regulations (Rytuba, 2003) In the United States, mercury is now produced only as a by-product from presently operating gold mines where environmental regulations require its recovery, and from the reprocessing of precious metal mine tailings and gold-placer sediments Many of the mercury mines in the California Coast Ranges contain waste rock that contributes mercury-rich sediments to nearby watersheds At some mines, the release of mercury

in acidic drainage is a significant source of mercury to watersheds, where it is taken up by fish and other organisms (Rytuba, 2003)

Atmospheric transport of anthropogenic mercury may contaminate remote ecosystems (Watras

et al., 1994; Lin et al., 2001) In one case, a remote lake in northern Wisconsin with no surface inflow and negligible groundwater inflow received about 100.0 mg Hg/ha during 1988 to 1990, an input that could account for the elevated mercury burdens found in water, sediments, and fish (Wiener et al., 1990, 2003; Watras et al., 1994)

Several human activities that contribute significantly to the global input of mercury include the combustion of fossil fuels; mining and reprocessing of gold, copper, and lead; operation of chlor-alkali plants; runoff from abandoned cinnabar mines; wastes from nuclear reactors, pharmaceutical plants, oil refining plants, and military ordnance facilities; incineration of municipal solid wastes and medical wastes; offshore oil exploration and production; disposal of batteries and fluorescent lamps; and the mining, smelting, use, and disposal of mercury (USNAS, 1978; Das et al., 1982; Gonzalez, 1991; Lodenius, 1991; Facemire et al., 1995; Gustafson, 1995; Atkeson et al., 2003;

Lacerda et al., 2004; Liang et al., 2004) In one case, more than 5.5 million kg of elemental mercury were released into the Carson River Drainage Basin in Nevada during historic mining operations — now closed — in which mercury was used to amalgamate gold and silver ore (Gustin et al., 1995) Mercury concentrations in sample tailings were as high as 1570.0 mg/kg The air directly over the site contained 1.0 to 7.1 ng Hg/m3, and was as high as 240.0 ng/m3 in October 1993 The estimated range of mercury flux to the atmosphere from the site was 37.0 to 500.0 ng/m2 hourly (Gustin

et al., 1995)

Mercury emissions from electric utilities constitute the largest uncontrolled source of mercury

to the atmosphere (USEPA, 1997), and globally it accounts for up to 59.0% of the total annual atmospheric loading of mercury from both natural and anthropogenic sources (Fitzgerald, 1986; Fitzgerald and Clarkson, 1991; WHO, 1976, 1991; Mason et al., 1994; USEPA, 2000; Lamborg

et al., 2002) Coal-fired power plants are now considered the greatest source of environmental mercury in the United States, and the only significant source that remains unregulated (Maas et al., 2004) In 1994, about 50 metric tons of mercury were emitted into the biosphere from coal-burning power plants in the United States, with lesser amounts from oil- and gas-combustion units (Finkel-man, 2003) Available technologies now installed in waste combustion and medical incinerators are recommended for installation in coal-fired plants and may reduce mercury emissions by as much as 90.0% (Maas et al., 2004) In fact, the U.S Environmental Protection Agency made steady progress throughout the 1990s in reducing mercury emissions from power plants, although this effort abated in recent years owing to the high costs of pollution abatement (Trasande et al., 2005) The economic costs of methylmercury neurotoxicity from these plants was estimated using a hypothetical model In that scenario, Trasande et al (2005) aver that methylmercury-induced loss

of intelligence would affect between 316,000 and 637,000 children each year in the United States,

as judged by umbilical cord blood concentrations greater than 5.8 µg methylmercury/L, a level

associated with IQ loss This intelligence loss is translated into diminished economic activity equivalent to at least U.S $8.7 billion annually (range $2.2 to $43.8 billion) The model proposed

by Trasande et al (2005) requires verification

Logging and forest fires can contribute to the bioavailability of mercury (Garcia and Carignan, 2005) Watersheds impacted by clear-cut logging, or burnt forest ecosystems, release mercury into the biosphere with significant increases in the flesh of predatory fish from impacted drainage lakes when compared to reference watersheds (Garcia and Carignan, 2005)

Most of the daily intake of mercury compounds is in the form of methylmercury derived from dietary sources, primarily fish, and to a lesser extent elemental mercury from mercury vapor in dental amalgams, and ethylmercury added as an antiseptic to vaccines (Mottet et al., 1985; USNAS, 2000; Clarkson et al., 2003; Dye et al., 2005) Dental amalgams, which may contain up to 50.0%

by weight of metallic mercury, may also constitute a significant source of mercury in some cases (Summers et al., 1993) Amalgam mercury is imperfectly stable, slowly leaching from the mercury-silver or mercury-gold amalgam through the action of oral bacteria and exacerbated by chewing Following placement or removal of fillings, up to 200.0 mg mercury is eliminated in the feces, with subsequent selection of mercury-resistant bacteria for degradation Normal mastication may result in body accumulations of 10.0 µg daily through either intestinal uptake or respiratory intake

of mercury vapor released during chewing (Summers et al., 1993)

Consumption of fish contaminated with mercury was associated with elevated mercury con-centrations in the blood and hair of about 1200 Amerindians in northwestern Ontario, Canada (Phelps and Clarkson, 1980) The source was inorganic mercury catalysts from a chloralkali plant

In this case, about 9 tons of mercury were discharged into wastewaters between 1962 and 1979,

at which time mercury usage for the production of chlorine and caustic was drastically reduced (Phelps and Clarkson, 1980) In aquatic ecosystems, removal of the source of anthropogenic mercury — such as chloralkali plants — results in a slow decrease in the mercury content of sediments and biota (USNAS, 1978) The rate of loss depends, in part, on the initial degree of contamination, the chemical form of mercury, physical and chemical conditions of the system, and the hydraulic

turnover time (USNAS, 1978) Between 1986 and 1989, throughout all Canada, a total of five mercury-cell chloralkali plants were still operating (Paine, 1994) By comparison, during the period

1935 through the mid-1970s, about 15 chloralkali plants were operating; the development of alternative technologies to replace the mercury cell was largely responsible for the plant closures Total mercury losses to the environment from these five operating plants during the 4-year period from 1986 to 1989 were about 6.5 metric tons (Table 2.3)

Mercury contamination of more than 500,000 miners, adjacent Indian populations, and numer-ous populations of fish and wildlife is one consequence of the gold rush that took place in the early 1980s in the Amazon region of Brazil Metallic mercury was used to agglutinate the fine gold particles through amalgamation During this process, large amounts of mercury were lost to the river and soil; additional mercury was lost as vapor to the atmosphere during combustion of the amalgamated gold to release the gold (Barbossa et al., 1995) Elemental mercury used in seals of three trickling filters in municipal wastewater treatment plants — each seal contained several hundred kilograms of mercury — leaked repeatedly, discharging 157.0 grams of mercury and 0.4 grams of methylmercury daily; the use of mercury seals for this purpose should be discontinued (Gilmour and Bloom, 1995) Also discontinued, in 1967, by Finland is the use of phenylmercury compounds as slimicides in the pulp industry (Lodenius, 1991) In Canada and the United States, mercurial compounds were used to control fungi in pulp paper processing plants, with subsequent mercury contamination of edible fish muscle (Silver et al., 1994)

Abandoned mercury mines may contribute excess mercury loadings and other contaminants to the environment For example, mercury mines in western Turkey that were gradually abandoned owing to low demand, low prices, and increasing environmental concern over mercury adversely affected adjacent water resources (Gemici, 2004) One abandoned mine located 5 km west of Beydag, Turkey, that operated from 1958 through 1986 with a total production of 2045 metric tons

of mercury during this period released metal-rich, acidic drainage affecting groundwater and adjacent stream water quality through decreasing pH; elevated levels of silicon, aluminum, mag-nesium, calcium, and potassium; increasing precipitation of iron oxides; and increasing sulfates, manganese, iron, and arsenic Most of the mine water and groundwater samples exceeded drinking water standards for aluminum, iron, manganese, arsenic, nickel, and cadmium Mercury concen-trations in all samples were below the Turkish drinking water standard of 1.0 µg/L for human

health; however, two samples contained 0.3 and 0.5 µg Hg/L and were above the USEPA mercury

criterion for aquatic life protection of < 0.012 µg/L (Gemici, 2004)

In the Florida Everglades, 61.0% of the mercury is due to atmospheric deposition from anthro-pogenic sources, especially municipal solid waste combustion facilities (15.0%), medical waste

Table 2.3 Mercury Loss (in kg) from Five Operating

Chloralkali Plants in Canada between 1986 and 1989 via Wastewater, Air Emissions, Products, and Solid Wastes

1986 1987 1988 1989 Total

Air emissions 680 831 572 547 2630

Solid wastes 449 662 1010 1196 3317 Total 1288 1627 1715 1861 6491 a

a Individual plant losses of total mercury from the five chloralkali plants during the 4-year period 1986 to 1989 were 290, 1089, 1247, 1721, and 2144 kg, respectively.

Source:Paine, P.J 1994 Compliance with chlor-alkali

mercury regulations, 1986 to 1989: status report, Report EPS 1/HA/2, 1-43 Available from Environmental

Protec-tion PublicaProtec-tions, Environment Canada, Ottawa, Ontario K1A OH3.

incinerators (14.0%), paint manufacturing and application (11.0%), electric utility industries (11.0%) and private residences (2.0%) through combustion of fossil fuels, and electrical apparatus, including fluorescent, metal halide, and mercury vapor lights (6.0%) All other anthropogenic sources combined — including sugarcane processing, the dental industry, open burning, and sewage sludge disposal — accounted for about 3.0% of the total mercury emitted to the environment (Sundolf et al., 1994) Recent and more extensive studies (Dvonch et al., 1999; Atkeson et al., 2003)

on mercury monitoring in the Florida Everglades ecosystem show that more than 95.0% of the mercury loading is from atmospheric deposition; that 92.0% of the total deposition came from local sources, such as municipal waste combustion, medical waste incinerators, electric utility boilers (coal, oil, gas), commercial and industrial boilers, and hazardous waste incinerators; and that long-distance transport of mercury wastes from certain sources are becoming increasingly important in Florida, especially mercury from waste incinerators and other atmospheric emitters, increased release of mercury from drainage and soil disturbance, and from hydrologic changes Atkeson et al (2003) believe that more data is needed on the sources of mercury deposition in the Florida Everglades, especially atmospheric mercury loadings from nonlocal sources

Reduction in mercury emissions and other contaminants from municipal waste incinerators using the best available technology is not always completely successful For example, the Angers, France, solid waste incinerator plant in operation since 1974 was upgraded in 2000 to comply with the new European standards (Glorennec et al., 2005) Mean mercury emissions were reduced about 13.0%, from 26.8 (18.6 to 69.4) kg/year to 23.3 (< 1.0 to 72.5) kg/year; and mean ambient air concentrations by about 62.0%, from 0.0004 µg/m3 (max 0.001 µg/m3) to 0.00015 µg/m3 (max 0.0028 µg/m3); however, the maximum values in both comparisons were larger in 2000 to 2001 than in 1975 to 1979 (Glorennec et al., 2005)

2.3 SUMMARY

Mercury has been mined continuously for at least 2400 years for use in gold recovery (until the present time), in the manufacture of felt hats and mirrors (1700s), in the chloralkali industry to manufacture chlorine and caustic (since the 1800s), as a fungicide in agriculture and paper pro-duction (1900s), and currently in lighting fixtures, batteries, paints, dentistry, and in medicine to kill bacteria and cutaneous parasites Major anthropogenic sources of mercury to the biosphere include combustion of fossil fuels from power plants, municipal solid waste combustion facilities, medical waste incinerators, paint manufacturing, and gold extraction Combustion of mercury-containing fossil fuels may account for up to 60.0% of the global mercury burden from human activities Use of mercury to amalgamate gold in Amazonia has resulted in mercury contamination

of at least 500,000 miners and numerous fish and wildlife populations And use of inorganic mercury catalysts in chloralkali plants has caused contamination of fish in waterways and elevated blood and mercury levels in Canadian Amerindians who consumed these fish

World production of mercury in recent years is estimated at 10,000 to 15,000 metric tons annually; major producers of mercury now include the former Soviet Union, Spain, the former Yugoslavia, and Italy The total amount of mercury in various global reservoirs is estimated at

334 billion metric tons, mostly in ocean sediments (98.75%) and ocean waters (1.24%) Only

7 metric tons of mercury are believed to be present in living aquatic organisms During the past

100 years, an estimated 500,000 tons of mercury entered the biosphere, with eventual deposition

in subsurface sediments Mercury inputs to the biosphere are mainly from natural sources, but with significant and increasing amounts contributed from human activities Soil bacteria and terrestrial plants expedite flux rates of elemental mercury from the geosphere to the atmosphere The atmo-sphere plays an important role in the mobilization of mercury, with about half the total atmospheric mercury burden of anthropogenic origin Atmospheric transport of mercury may contaminate remote ecosystems hundreds of kilometers distant

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