18
S. P. Kayastha and K. Pradhanang
withdrawal of groundwater has been done with the use of dug wells and tube wells
[14].
Arsenic (As) in groundwater is considered as one of the most toxic elements.
Arsenic (As) contamination is a severe issue not just in Nepal but throughout the
world. Excessive concentration of arsenic in drinking water has been observed from
different parts of the world [1, 2]. Distribution of arsenic in shallow groundwater has
been observed highly irregular both vertically and horizontally on local or regional
scales [10]. The natural source of As in the natural environment is the release from
As-enriched minerals. Weathering processes, particularly the rocks and minerals, are
the major sources of arsenic in soils [28].
The sources of As comprise natural arsenic and anthropogenic. Natural arsenic
contamination occurs through dissolution of compounds (pyrite ores) in water. With
the increase in population, there has been corresponding increase in agricultural
waste, rich in phosphate fertilizers, insecticides, herbicides, end products of mining
processes, coal combustion and timber preservatives [6]. These are the anthropogenic
sources which can affect the purity of surface water [19]. Similarly, mining wastes
disposal has caused As contamination of groundwater in several places [9].
As occurs naturally in groundwater in concentrations which can pose serious
health effects after continuous consumption [23]. Long-term human and excessive intake of inorganic arsenic with food and water cause arsenicosis, skin cancer
gastrointestinal, neurological pulmonary, respiratory problems and reproductive
system [3, 28, 30]. Many studies have been carried out to determine the toxicity
of As and its impacts on human health in various As-contaminated areas [19]. In
soils and groundwater, As is a significant contaminant and pollutant across the many
regions of the globe.
The concentration of As in groundwater is a function of solubility, which is
governed predominantly by pH, redox conditions, temperature, salinity, presence
of complex ions and others metals ions, not merely related to the abundance of
minerals in aquifers [12, 26]. In poorly ventilated place where As-rich coal or cow
dung is used as a fuel, inhaled amounts of As may be high [18].
In Nepal, As contamination is mainly observed in the Tarai region. Out of 24
districts that have been reported with arsenic contamination, 20 districts are from the
Tarai region and four are from the hilly region [7]. Highest arsenic-affected districts
are Nawalparasi, Rautahat, Bara and Parsa [24]. In drinking water, the concentration
of arsenic permissible has been set at 0.01 mg/L by the World Health Organization
(WHO) guidelines [30]. In Nepal, the maximum permissible limit of As in water
used for drinking purposes is 0.05 mg/L [8]. Groundwater is the major drinking water
source in the Tarai. Drinking water quality in Nepal has been an issue of prevalent
concern. The aim of this study was toexaminethe distribution of groundwater As and
also to identify the relationship between arsenic concentration and tube well/dug
well depths.
S. P. Kayastha and K. Pradhanang
withdrawal of groundwater has been done with the use of dug wells and tube wells
[14].
Arsenic (As) in groundwater is considered as one of the most toxic elements.
Arsenic (As) contamination is a severe issue not just in Nepal but throughout the
world. Excessive concentration of arsenic in drinking water has been observed from
different parts of the world [1, 2]. Distribution of arsenic in shallow groundwater has
been observed highly irregular both vertically and horizontally on local or regional
scales [10]. The natural source of As in the natural environment is the release from
As-enriched minerals. Weathering processes, particularly the rocks and minerals, are
the major sources of arsenic in soils [28].
The sources of As comprise natural arsenic and anthropogenic. Natural arsenic
contamination occurs through dissolution of compounds (pyrite ores) in water. With
the increase in population, there has been corresponding increase in agricultural
waste, rich in phosphate fertilizers, insecticides, herbicides, end products of mining
processes, coal combustion and timber preservatives [6]. These are the anthropogenic
sources which can affect the purity of surface water [19]. Similarly, mining wastes
disposal has caused As contamination of groundwater in several places [9].
As occurs naturally in groundwater in concentrations which can pose serious
health effects after continuous consumption [23]. Long-term human and excessive intake of inorganic arsenic with food and water cause arsenicosis, skin cancer
gastrointestinal, neurological pulmonary, respiratory problems and reproductive
system [3, 28, 30]. Many studies have been carried out to determine the toxicity
of As and its impacts on human health in various As-contaminated areas [19]. In
soils and groundwater, As is a significant contaminant and pollutant across the many
regions of the globe.
The concentration of As in groundwater is a function of solubility, which is
governed predominantly by pH, redox conditions, temperature, salinity, presence
of complex ions and others metals ions, not merely related to the abundance of
minerals in aquifers [12, 26]. In poorly ventilated place where As-rich coal or cow
dung is used as a fuel, inhaled amounts of As may be high [18].
In Nepal, As contamination is mainly observed in the Tarai region. Out of 24
districts that have been reported with arsenic contamination, 20 districts are from the
Tarai region and four are from the hilly region [7]. Highest arsenic-affected districts
are Nawalparasi, Rautahat, Bara and Parsa [24]. In drinking water, the concentration
of arsenic permissible has been set at 0.01 mg/L by the World Health Organization
(WHO) guidelines [30]. In Nepal, the maximum permissible limit of As in water
used for drinking purposes is 0.05 mg/L [8]. Groundwater is the major drinking water
source in the Tarai. Drinking water quality in Nepal has been an issue of prevalent
concern. The aim of this study was toexaminethe distribution of groundwater As and
also to identify the relationship between arsenic concentration and tube well/dug
well depths.