Page 205 - Soil Degradation, Conservation and Remediation

194 6 Soil Pollution

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contamination of soils worldwide. Contamination in excess of 1,000 mg As kg has
been recorded at many sites throughout Australia. Similar contaminated sites also
exist in the USA, Africa, and other parts of the world (Smith et al. 1998a , b ). The
main sources of As in soils is the parent materials from which the soil is derived
(Yan-Chu 1994 ). The distribution of As in soils may vary with soil type, depending
on the nature of the parent material. Background concentrations do not generally
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exceed 15 mg As kg (NRCC 1978 ), although concentrations ranging from 0.2 to
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40 mg As kg soil have been reported (Walsh et al. 1977 ). Dudas and Pawluk ( 1980 )
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reported background As concentrations that averaged 5 mg As kg in 78 soil samples
in Alberta. Much higher As concentrations have been reported in acid sulfate soils
developed on pyritic parent material. For instance, Dudas ( 1987 ) attributed elevated
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As concentrations that ranged from 8 to 40 mg As kg in Canadian acid sulfate soils
to the weathering of pyrites in the parent material. Many different As compounds

have been identified in the soil environment, and they may be classified into two

major groups: inorganic As compounds and organic As compounds. As (V) and
As (III) are the most important inorganic As species in the soil, because their
compounds are highly soluble in water (Masscheleyn et al. 1991 ).

Arsenic Contamination to Groundwater and Arsenicosis in Asia
Arsenic contamination in groundwater has invaded in several regions of the
Southeast Asian countries like Bangladesh, China, India, and Nepal. Water
drawn from shallow aquifers through shallow tube wells exceeds the national
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standards (0.050 mg L ) and USEPA and WHO standards (0.01 mg L ) of As
level for drinking water. The cause of this contamination to groundwater is geo-
chemical; the sedimentary rocks there contain high As. People use shallow tube
well water for domestic uses including drinking. Large-scale occurrences of
arsenicosis have been reported from the contaminated areas. Health problems
associated with elevated levels of arsenic include thickening and discoloration of
the skin, stomach pain, nausea, vomiting, diarrhea, numbness in hands and feet,
partial paralysis, and blindness. Arsenic has been linked to cancer of the blad-
der, lungs, skin, kidney, nasal passages, liver, and prostate. Thirty million peo-
ple in Bangladesh use arsenic contaminated water for drinking. About
10,000–30,000 people have been diagnosed with arsenicosis (Alam et al. 2002 ).
In China, endemic arsenicosis was found successively in many areas in the
mainland during 1980s, and more than 10,000 arsenicosis patients were diag-
nosed by 2001. The main As-contaminated provinces are Xinjiang, Inner
Mongolia, Shanxi, Ningxia, Jilin, and Qinghai. In India, arsenic- contaminated
groundwater occurs mainly in the states of West Bengal, Bihar, Uttar Pradesh,
Assam, Jharkhand, Chhattisgarh, and Madhya Pradesh. According to UNICEF,
over 13.8 million people are at risk of arsenicosis in West Bengal (Chakraborti
et al. 2002 ). The problems are mainly related with As-contaminated drinking
water, but there is also the risk of contaminating the food chain. Shallow aquifer
water is the major source of irrigation in rice growing areas of Asia.