AS arsenic

8/13/2019 AS arsenic

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*: .18,,

Arsenic , As . ""." Orpiment"

Orpiment


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Periodic Table of

the Elements

As is a Group V element (like N and P)

Replaces S in minerals and metabolic systems

replaces P in minerals and ATP energy cycle


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Sources of arsenicSoi l and Sediment

Arsenic concentrations in soils depend in part on the parent materials from

which the soils were derived, although they may be enriched by other

sources, including anthropogenic sources.

Typical natural concentration ranges are 0.1 to 40 mg/kg, with an average

concentration of 5-6 mg/kg (NAS, 1977).

The level of arsenic in soil derived from basalts tends to be higher than insoils of granitic origin, and concentrations of 20 to 30 mg/kg may be found

in soils derived from sedimentary rocks (Yan-Chu, 1994). In areas of

recent volcanism, soils average arsenic concentrations are approximately

20 mg/kg. Very high natural concentrations of arsenic (up to 8,000 mg/kg)

may occur in soils that overlay deposits of sulfuric ores (NAS, 1977).Arsenic can be found in soil in the inorganic state bound to cations, and it

can also be found bound to organic matter. Arsenic may be transferred to

surface water and ground water through

erosion and dissolution; plants may also uptake arsenic. Because arsenic

can be fixed in inorganic and organic compounds in soil, soil may also bea sink for arsenic


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Geothermal Waters

Geothermal water can be sources of arsenic insurface water and ground water. Welch et al., (1988)

identified 14 areas in the Western United States

where arsenic conditions in water exceed 50 g/L

because of known or suspected geothermalsources. In these areas, dissolved

arsenic concentrations ranged from 80 to 15,000

g/L. Welch et al.,found that mean dissolved arsenic

concentrations in geothermal ground waters arehigher than mean arsenic concentrations in non-

thermal ground waters in any of the physiographic

provinces in the United States.


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Other Sources

Natural emissions of arsenic associated with volcanic activity

and forest and grass fires are recognized to be significant.Indeed, volcanic activity appears to be the largest natural

source

of arsenic emissions to the atmosphere (ATSDR, 1998).

Estimates of natural releases (of which volcanic arsenic

emissions are the primary source).


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natural sources, arsenic is released from a variety of

anthropogenic sources (USEPA, 1998b), including:

Manufacturing of metals and alloys

Petroleum refining Pharmaceutical manufacturing

Pesticide manufacturing and application

Chemicals manufacturing

Burning of fossil fuels

Waste incineration

These anthropogenic releases of arsenic can elevate

environmental arsenic concentrations. Human exposure to

arsenic can result in a variety of chronic and acute effects. Inparticular, there is evidence that associates chronic arsenic

ingestion at low concentrations with

increased risk of skin cancer, and that arsenic may cause

cancers of the lung, liver, bladder, kidney, and colon (ATSDR,1998). Because of the human health risks associated with


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Mining and Smelt ing

Arsenic can be obtained from two of its ores, arsenopyrite and

lollingite, by smelting in the presence of air around 650700 C(Kirk-Othmer, 1992), or arsenic trioxide (As2O3) in flue dust

from the extraction of lead and copper can be captured

(Ferguson, 1990). Subsequently, arsenic trioxide can be used

to produce other arsenic compounds or purified to elemental

arsenic.

Arsenic trioxide was produced for commercial use in the United

State at the ASARCO smelter in Tacoma, Washington, until

1985, at which time the smelter ceased operations (ATSDR,

1998). The USEPA Office of Air Quality Planning and Standardsindicates that

primary and secondary6 lead smelters, primary copper

smelters


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E


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Exposure

Arsenic is continually cycled through all environmental

compartments. Arsenic can be elevated to high levels in water

and soil because of the underlying geology or geothermal

activity. In the aquatic environment arsenic concentrations canalso become elevated in some estuaries and in waters near

heavy industrial or mining and mineral-processing areas. The

highest concentrations of arsenic in soil tend to be associated

with mining waste.Mean total arsenic concentrations in air from remote and rural

areas range from 0.02 to 4 ng/m3. Mean total arsenic

concentrations in urban areas range from 3 to about 200 ng/m3;

much higher concentrations (> 1000 ng/m3) have been

measured in the vicinity of industrial sources.

Reported concentrations of arsenic in surface waters are

summarized in Fig. 6. Concentrations of arsenic in open ocean

seawater are typically 12 g/litre. Arsenic is widely distributed

in surface freshwaters, and background concentrations in rivers


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Mean arsenic concentrations of 500 g/litre and a

maximum of 25 mg/litre have been reported for geothermalwaters. Enhanced arsenic levels of < 10 mg/litre have

been reported near anthropogenic sources such as mining

and agrochemical manufacture. Mean sediment arsenic

concentrations range from 5 to 3000 mg/kg, with the

higher levels occurring in areas of contamination.Reported concentrations of arsenic in soils are

summarized in Fig. 7. Background concentrations in soil

tend to range from 1 to 40 mg/kg, with a mean value of 5

mg/kg. Naturally elevated levels of arsenic in soils may beassociated with geological substrata such as sulfide ores.

Anthropogenically contaminated soils can have

concentrations of arsenic up to several percent


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Terrestrial plants

Arsenic species can enter into edible tissues of food crops

through absorption (i.e. not just surface contamination)(Woolson, 1973; Helgesen & Larsen, 1998). Helgesen & Larsen

(1998) demonstrated that bioavailability of arsenic pentoxide to

carrots in soil from a wood preservative treatment plant (soil was

contaminated with CCA) was 0.47 0.06% of total soil arsenic

burden. This study showed that arsenite, arsenate, MMA and

DMA were present in carrot tissue, where only arsenite and

arsenate were present in soil. In soils dosed with arsenate (0

500 g/g) at the concentrations which inhibited growth of

vegetable crops (green bean, lima bean, spinach, cabbage,tomato and radish), high levels of accumulation when found in

the edible parts of radish (76 g/g) spinach (10 g/g) and green

bean (4.2 g/g). Arsenic accumulation in Lima bean, cabbage

and tomato ranged from 0.71.5 g/g. The studies of Woolson1973 and Hel esen & Larsen 1998 hi hli ht the otential of


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Environmental levels

Arsenic is a natural component of the earths crust, and found

in all environmental media. Concentrations in air in remote

locations range from < 1 to 3 ng/m3, but concentrations in

cities may range up to 100 ng/m3. Concentrations in water

are usually < 10 g/litre, although higher concentrations can

occur near natural mineral deposits or anthropogenicsources. Natural levels in soils usually range from 1 to 40

mg/kg, but pesticide application or waste disposal can

produce much higher values


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Levels of arsenic in ambient air are summarized in Examples

are given of mean total arsenic concentrations in remote and

rural areas ranging from 0.02 to 4 ng/m3. Levels of arsenic in

outdoor air near to urban and industrial sources are

summarized in . Examples are given of mean total arsenicconcentrations in urban areas ranging from 3 to 200 ng/m3;

much higher concentrations (> 1000 ng/m3) have been

measured in the vicinity of industrial sources. Arsenic in

ambient air is usually a mixture of arsenite and arsenate, withorganic species being of negligible importance except in areas

of substantial methylated arsenic pesticide application or biotic

activity. Schroeder et al. (1987) reviewed worldwide arsenic

concentrations associated with particulate matter.

1 -Air


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They identified arsenic levels ranging from 0.007 to 1.9

ng/m3for remote areas, 1 to 28 ng/m3for rural areas and 2 to

2320 ng/m3

in urban areas. The highest arsenic levelsdetected in the atmosphere were near non-ferrous-metal

smelters.

Typical background levels for arsenic are now 0.21.5 ng/m3

for rural areas, 0.53 ng/m3for urban areas and < 50 ng/m3

for industrial sites (DG Environment, 2000).


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Environmental effects of arsenic

The arsenic cycle has broadened as a consequence of human

interference and due to this, large amounts of arsenic end up inthe environment and in living organisms. Arsenic is mainly emitted

by the copper producing industries, but also during lead and zinc

production and in agriculture. It cannot be destroyed once it has

entered the environment, so that the amounts that we add can

spread and cause health effects to humans and animals on many

locations on earth.

Plants absorb arsenic fairly easily, so that high-ranking

concentrations may be present in food. The concentrations of thedangerous inorganic arsenics that are currently present in surface

waters enhance the chances of alteration of genetic materials of

fish. This is mainly caused by accumulation of arsenic in the

bodies of plant-eating freshwater organisms. Birds eat the fish thatalread contain eminent amounts of arsenic and will die as a


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Risk evaluation

Conventional, generic risk assessment would apply uncertainty factors to

the lowest reported chronic effects concentration. For arsenic in freshwaters,

this would be 5 g/litre for growth in algae. This concentration is similar to

the upper limit of the natural range of arsenic concentrations in most surface

freshwaters. It is almost four orders of magnitude lower than the highest

natural concentrations of arsenic in geothermal regions. Since communities

of organisms occur in surface waters across the whole natural range (0.05

25 000 g/litre), a single protective concentration target for arsenic isinappropriate. Although there is no direct evidence that populations of

organisms living at the higher end of the range for most surface waters

(around 2 g/litre) are less sensitive to arsenic than those at the bottom end

of the range (0.05 g/litre), this might be inferred from laboratory and field

evidence. There is clear laboratory and field evidence that populations livingat much higher concentrations have adapted to high inorganic arsenic

levels. may mitigate arsenic toxicity in the environment. Realistically, risk

assessment for inorganic arsenic can only be done on a site-by-site basis

taking into account background arsenic concentrations, local population

tolerance and other local mitigating factors


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For populations of organisms living in low inorganic arsenic

environments with little possible mitigation (e.g. low

phosphate levels), a concentration of around 5 g/litre would

be protective of all but the most sensitive algae. Adapted

populations at high natural inorganic arsenic concentrations

will be specialized communities, possibly of lower biodiversity

but probably of high conservation interest. Areas polluted by

anthropogenic activity, therefore, present the risk managerwith different options based on both practicability and

desirability of remediation; if adapted communities have

developed over time, these might be destroyed by

remediation. Clearly the contamination of pristine areas witharsenic to levels which cause adaptation and decreased

biodiversity is unacceptable.

What are the Potential Health Effects?


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What are the Potential Health Effects?

The primary health concern with

exposure to arsenic is cancer. Exposure

to arsenic over many years can increaseyour chances of getting certain types of

cancer, or other health effects, such as

diarrhea, poor blood production, and

abnormal heart beat. The healthoutcomes depend on the length of time

that you are exposed to arsenic from

any source, the amount of arsenic in

your water, the amount of water that youdrink, and your current level of health.

The risk of developing health effects are

the same for everyone, including

children re nant women and other


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Effects on human health

Cancer Melanosis

Hyperkeratosis


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Summary of Method

The ICPMS methods have been described previously in Faires

(1993) and Garbarino and Taylor (1994). The following sections

only provide additional information specific to the elements thatare

being added to the method.

Former methods and ICPMS method detection limits and

calibration limits for new elements determined in filtered,acidified natural water

[All concentrations are in micrograms per liter; MRL, minimum

reporting level; MDL, method detection limit; CC, catalyzed

colorimetry; DCPAES, direct current plasmaatomic emissionspectrometry; FAAS, flameatomic absorption

spectrophotometry; GFAAS, stabilized temperature graphite

furnaceatomic absorption

spectrophotometry; HGAAS, hydride generationatomic

absorption spectrophotometry; ICPAES, inductively coupled


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Accuracy of inductively coupled plasmamass

spectrometric arsenic determinations in the presenceof bromide using different correction equations. The

error bars correspond to one standard deviation based

on three instrumental measurements.


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Sample Preparation

Filtered, acidified natural-water samples analyzed by ICP

MS for dissolve arsenic, boron, lithium, selenium,

strontium, thallium, and zinc and other elements do not

require additionalprocessing.

.

Analytical Procedure

Refer to Perkin-Elmer (1997a, 1997b) and NWQL

Standard Operating Procedure IM0011.1 (T.M. Struzeski,

U.S. Geological

Survey, written commun., 1998) for details of

the analytical procedure. In addition, the accuracy of


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Statistical analysis of long-term ICPMS

results for U.S. Geological Survey Standard

Reference Water Sample T145 [ICPMS,inductively coupled plasmamass

spectrometry; elemental results are in

micrograms per liter; MPV, the most probablevalue; , the plus or minus symbol precedes

the F-pseudosigma in the MPV

column and the standard deviation in the

experimental mean column; n, number ofreplicates used to calculate the experimental

mean; p-value, level of significance;


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Short-term analytical variability as a function of elemental

concentration for ICPMS [ICPMS, inductively coupled

plasmamass spectrometry, the percent relative standarddeviations are based on three sequential determinations in

a 0.4-percent solution of concentrated nitric acid in

deionized water; g/L, micrograms per liter;


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Average percent spike recoveries in reagent-

water, surface-water and ground-water matrices

by inductively coupled plasmamassspectrometry [mg/L, micrograms per liter; number

following the plus or minus symbol () is the

standard deviation on the basis of sevendeterminations accrued on separate days; high

spike, 75 mg/L for all elements; na, not applicable

because the difference between the spike

concentration and ambient concentration wasgreater than a factor of 10;


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AS arsenic

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