Analyses of Arsenic Contamination of Groundwater in Pakistan
Abstract
Arsenic contamination in the groundwater of Pakistan has severely affected public health and the environment. In Pakistan groundwater is one of the major water resources, however, the concentration of Arsenic in groundwater exceeds the standard limit set by WHO (10 μg/L). According to recent studies Punjab and Sindh province’s groundwater sources are most contaminated with Arsenic, in Nagarparkar thar the concentration was recorded 1965ug/L in 2013 which exceeds the national environmental quality standards of Pakistan and the standard limit set by EPA. In 2018, 18 major cities of Punjab and Sindh were reported to have arsenic concentrations greater than the safe limits. Nagarparkar Thar and Hyderabad (in Sindh province) along with Lahore and Kasur (in Punjab province) are hotspots sites of high Arsenic contamination in groundwater. In ChacharoThar the concentration of Arsenic was recorded 1935ug/L in 2013. Long-term exposure to high concentrations of Arsenic can cause devastating health effects including fatal diseases like cancer. The purpose of this article is to discuss and display the concentration of Arsenic in groundwater in Pakistan.
Introduction
Arsenic (As), a known carcinogen, occurs as a natural element in the Earth’s crust. It is the 20th most abundant element in the upper crust with concentrations ranging between 1 and 2 mg/kg (Pontius et al. 1994).
Approximately 2.5% of the Earth’s water resources are freshwater; 30% of the freshwater is present as groundwater (USGS, 2016). Unfortunately, this small percentage of fresh water, especially groundwater, is jeopardized due to the rapid growth of population, increasing urbanization, and unsustainable consumption of water in domestic, industrial, and agricultural sectors. The water-related problems are further intensified in developing countries due to the lack of resources, improper management of available resources, and financial restrictions.
The contamination of groundwater in Pakistan and its impacts on human health and the surrounding environment need to be investigated. There is a need to collect groundwater quality data in different parts of the country to explore management practices to overcome water-related problems. Different studies are available on topics related to water pollution, sources, health impacts, and remedies.
World Health Organization (WHO) declared “As’’ in drinking water, a “major public health issue” which needed to be deal with on an emergency basis (WHO 1999).
The current recommended limit of arsenic in underground water (drinking water) is 10 μg/L, although this guideline value is designated as provisional because of practical difficulties in removing arsenic from drinking water.
We aimed to present a brief overview of the current status of As contamination in groundwater in different provinces and districts of Pakistan, mainly focused on province of Punjab and Sindh. Some earlier studies have investigated, albeit partially, arsenic contamination of groundwater in different areas of Pakistan and predicted possible sources of arsenic release in groundwater.
Factors Affecting Arsenic Concentration of Ground Water
- Geogenic Source of Arsenic Contamination in Groundwater, Pakistan
Arsenic contamination of groundwater is a form of groundwater pollution that is often due to naturally occurring high concentrations of arsenic in deeper levels of groundwater. Some groundwater samples in Pakistan showed a strong correlation of ‘As’ with ferric iron (Fe(III)) in solution suggesting that oxidative dissolution of Fe(III)- and As-containing minerals, due to high pH and salinity, may contribute to mobilization of As. The high concentration of bicarbonate in most of the groundwater samples in the study area of Pakistan can trigger Arsenic release in groundwater. Bicarbonate ions can mobilize ‘As’ from sediments in both oxic and anoxic conditions. The combined role of pH and bicarbonate ions may exert a significant effect on As leaching from the sediments.
Significantly, more As-contaminated groundwater wells and the occurrence of skin lesions of local inhabitants were observed along the Indus River than those located away from the river, suggesting a strong link between As contamination of groundwater and proximity to the river. Thus, more efforts should be focused on geogenically derived As and examining natural factors controlling As release, rather than speculations about anthropogenic origins of As.
2. Anthropogenic Source of Arsenic
The intensive agricultural system also causes arsenic pollution through runoff containing organic and inorganic arsenic fertilizers. Similarly, industrial activities contribute a lot to arsenic pollution. There are a total of 6,634 registered industries in Pakistan, out of which, 1,228 are considered highly polluting. The waste effluents of these industries contain high organic loads and toxic metals including arsenic. In Pakistan, industrial waste and wastewater are directly discharged into water bodies (nearby rivers, drains, ponds, streams, ditches, and agricultural or open land) without any treatment.
Another source from agriculture is the use of arsenic fertilizers such as di-ammonium-phosphate (DAP) which contains water-soluble arsenic. Another main route of water pollution is from air deposition of arsenic mainly from coal burning and brick kilns. The ore mining and processing, dye manufacturing, tanneries, thermal power plants, pesticides, herbicides, and insecticides are the major arsenic pollution sources in the country. Domestic and municipal wastes also contain high arsenic levels which are directly discharged into drains or thrown openly in fields in many areas of the country.
Arsenic Health Impacts
Arsenic is a metalloid, ubiquitously available in the earth’s environment, and considered a global health risk factor. Essentially, arsenic concentrates in the earth’s crust, bedrock leaches gradually into the drinking water. Exposure to inorganic arsenic through consumption of contaminated food, water, and air leads to serious effects on human health. The distribution of arsenic in the body is fairly constant but widely distributed in organs such as skin, lungs, liver, and kidneys. Arsenic is a well-known human carcinogen. The presence of arsenic in drinking water may be responsible for the occurrence of bladder cancer.
Conclusion
The groundwater of Pakistan is highly contaminated with Arsenic. The contamination of groundwater is a consequence of anthropogenic activities. In most of the cities of Pakistan, the concentration of arsenic is far above the safe limit set by the World Health Organization (WHO) and National Environmental Quality Standards (NEQS) Pakistan.