This document provides information on arsenic, including its atomic properties, forms, sources in the environment, and effects on soils and plants. Arsenic is commonly found in soils in concentrations ranging from 1 to 40 mg/kg, and can be taken up by plants through their roots. In plants, arsenic toxicity causes damage to cellular components and metabolic processes, leading to stunted growth, chlorosis, and reduced yields. The mobility and toxicity of arsenic in soils depends on factors like the soil type, chemistry, and amount of arsenic present.

1. AHMAD
HASSAN
•SOIL SCIENCE
15-ARID-
4877
•TRACE ELEMENT
ARSENIC

3.  Atomic No: 33
 Atomic Weight: 74.92
 Chemical Symbol: As
 Arsenic Forms: Allotropic Forms
 Melting Point: 816.8 °C
 Boiling Point: 613 °C
 Discovered: A German Chemist
Albert Magnus in 1250 AD.

4. Arsenic Minerals:
Mostly conjugated with sulfide mineral
 NATIVE ARSENIC (Arsenic-As)
 ARSENO PYRITE (FeAsS)
 COBALTITE (CoAsS)
 ENARGITE (Cu3AsS4)
 PROUSTITE (Ag3AsS3)
 REALGAR (AsS)

5. Types of Arsenic
 Inorganic Arsenic:
 Refers to arsenic atoms that occur in their
pure,metallic form or in compounds where they
are bonded to other non carbon elements such
as in arsenic tri chloride AsCl3.
 Inorganic forms of As,arsenate and arsenite
are found to be more toxic.

6.  Organic Arsenic:
 Mainly found in marine organisms can still
be used on agriculture.
 Organic arsenic refers to organic (i.e.carbon
based) compounds that contain covalently
bonded arsenic atoms.
 When heated arsenic rises up smoke stack
as a fine dust cannot be used in agriculture.

7. One example of this is 4-Hydroxy 3-nitro
Benzene arsonic acid / Ruxarsone that is use in
Poultry farms for Additive or Early maturity of
Chicken.
Anthropogenic Sources:
Significant anthropogenic sources of As are
related to industrial activities
(metal processing,chemical works based on S
and P minerals,coal combustion,and geothermal
power plants) and to the use of arsenical
sprays,particularly in orchards.

8. Arsenic In Soils
 Arsenic can be found in soil concentrations
range from 1 to 40 mg/kg.
 Usually averaging around 5 mg/kg.
 Volcanoes release about 3000 tonnes/year.
 Microorganisms release volatile methylarsines
to the extent of 20,000 tonnes per year.
The reactions of As in soils are highly governed
by its oxidized state.

9.  Arsenic is distributed rather uniformly in major
types of rocks and its common concentrations in
most rocks range from 0.5 to 2.5 ppm.
 Only in argillaceous sediments is As,on the
average concentrated as high as 13 ppm.
 As is a ubiquitous element in the upper
lithosphere.

10.  The lowest As levels are found in sandy
soils and particular in those derived from
granites.
 Higher As concentrations are related most
often to alluvial soils and soils rich in organic
matter.
 Concentrations of arsenic in the soil
decreased as depth increased.

11. Mobility of As In Soil
 The mobility of As in soil was shown to be
proportional to the As added and inversely
proportional to time and to Fe and Al contents.
 The distance arsenic will move in a soil
depends on the amount of arsenic applied,the
soil type,chemical and physical properties of the
soil, and the amount of water moving through the
soil.

12. Toxicity
The toxicity of As depends on the concentration
of soluble As therefore sodium arsenate and
arsenic trioxide formerly used as herbicides, are
the most toxic.
Ways To Overcome Toxicity
The toxicity of As in soils may be overcome in
several ways but main is phytoremediation
technique in which hyperaccumulator fern specie
Pteris vita is used.
.
.

13. Arsenic In Plants
 As is a constituent of most plants,but there are
no well authenticated beneficial effects of arsenic
on plants.
 Arsenic concentration in plants is 1-50 mg As/kg.
 Plants take up As passively with the water flow.
 Some plants particularly Douglas fir show a
remarkable ability to take up As for more than
many of the associated plants.

14.  It could therefore well be that arsenic is an
essential element for plant growth but it has not
been proved.
 Arsenic is chemically similar to phosphorus,it
may work an essential plant nutrient.That it can
substitute for phosphorus in plant nutrition however
is the doubtful in some soils,the application of
phosphate fertilizer increases arsenic toxicity
(through the release of fixed arsenic).

15. Effect of Arsenic on Plants
Arsenic taken by plant tissues causes severe damage to
metabolic process in mitochondria and important cellular
components,such as lipids,protein,DNA and RNA.
In Canola:
Arsenic causes stunted growth,chlorosis and wilting.
In Rice:
Reduces seed germination,decrease in seedling
height,reduces leaf area and dry matter production.
In Tomato:
Arsenic reduces fruit yield,decreases the leaf fresh weight.

16. Symptoms of Arsenic toxicity in Plants
In plants arsenic toxicity symptoms include leaf
wilting,purpling and root discoloration.
It should be noted that the symptoms of arsenic
poisoning are similar to those of phosphorus
deficiency.

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