Measuring Arsenic Contamination in Water – Challenges And Solutions
Arsenic is a toxic chemical element found naturally in soil and rock. It can enter groundwater supply through human activities such as industrial processes, mining, and agriculture. Arsenic contamination in groundwater poses serious health risks if populations using the contaminated water supply consume it over a prolonged period. In this article, we will explore the sources of arsenic contamination, the health impacts, and the methods for determining the concentration of arsenic in water.
Arsenic can enter the groundwater supply through natural processes such as the weathering of rock formations and the breakdown of minerals. It can also enter the groundwater through human activities such as the use of arsenic-based pesticides, mining operations, and the release of industrial waste into the environment. It is a carcinogenic substance that can cause long-term health problems. Arsenic exposure can lead to a range of health problems including skin lesions, cardiovascular disease, diabetes, cancer, kidney failure and nervous system damage.
What methods are available to measure arsenic contamination in water?
Arsenic contamination in groundwater can be identified through regular monitoring and testing of the water supply. There are several methods available to test for arsenic in water, including:
1. Colorimetry:
- Principle: Based on the reaction between arsenic and reagents that produce a coloured end product.
- Advantages: Simple, cost-effective, and suitable for field testing.
- Limitations: Less sensitive, than most methods. Results can be technique dependent, time consuming and can carry a risk of hazardous fumes.
2. Graphite Furnace Atomic Absorption Spectrometry (GFAAS):
- Principle: Measures the absorption of light by arsenic atoms in a graphite furnace.
- Advantages: High sensitivity and precision.
- Limitations: Expensive equipment, requires skilled operators, and may be affected by interferences.
3. Inductively Coupled Plasma Mass Spectrometry (ICP-MS):
- Principle: Ionizes the sample and measures the mass-to-charge ratio of arsenic ions.
- Advantages: High sensitivity, low detection limits, and can analyse multiple elements simultaneously.
- Limitations: Expensive equipment, complex operation, and requires specialized training.
4. Atomic Fluorescence Spectrometry (AFS):
- Principle: Measures the fluorescence emitted by arsenic atoms.
- Advantages: High sensitivity, relatively simple instrumentation.
- Limitations: Requires a stable light source, and may be influenced by matrix effects.
5. Hydride Generation Atomic Absorption Spectrometry (HGAAS):
- Principle: Converts arsenic into arsine gas, which is then measured using atomic absorption.
- Advantages: Good sensitivity and precision.
- Limitations: Complex sample preparation, potential interferences, and requires specialized equipment.
6. High-Performance Liquid Chromatography (HPLC):
- Principle: Separates arsenic species and detects them using various detectors (e.g., UV-Vis, ICP-MS).
- Advantages: Can differentiate between different arsenic species.
- Limitations: Requires skilled operators, complex setup, and may be expensive.
Of these, only the colorimetric methods are practical for use as a field test. Even then, the most commonly used Gutzeit method requires particular care as it is based on generating Arsine gas from the sample which is then absorbed on a chemically dosed filter that changes colour.
More information on these and other standard methods for measuring chlorine dioxide
Palintest’s Kemio Solution
Kemio is a portable instrument that uses Anodic Stripping Voltammetry (ASV). This method is sensitive and precise method and can detect low levels of arsenic. It is ideal for generating quick and accurate results in the field
ASV involves an electro-deposition step, followed by a controlled dissolution at a defined electrical potential, whilst accurately measuring the current. Kemio uses an electrode sensor shown and performs this entire process automatically when the instrument when the arm is lowered and immersed the sensor in the sample. A concentration result is then simply shown on screen in around five minutes.
The Kemio Arsenic system can detect both total arsenic and arsenic (III) over the range 2 to 250 μg/L.
The Kemio instrument is simple to use and does not require any specialist training. Tests can be performed onsite within minutes, so a user can test for arsenic across more locations in a single day. Particularly useful when trying to trace the source of contamination.
Mitigating the Risks of Arsenic Contamination in Water
If high levels of arsenic are found in drinking water, it is important to take immediate action to mitigate the risk to health. Local regulations and guidelines will need to be followed, but may include:
Stopping use of the water for drinking and cooking
High levels of arsenic in drinking water can be harmful to human health, so it’s important to stop using the water for drinking and cooking until the problem is addressed.
Installing a water treatment system
If the water tests positive for high levels of arsenic, you may need to install a water treatment system to reduce the arsenic content. Options include reverse osmosis systems, activated alumina filters, and iron precipitation filters.
Seek alternative water sources
If installing a water treatment system is not feasible, you may need to seek alternative water sources, such as bottled water or a public water supply, for drinking and cooking purposes.
Stay informed
Stay informed about the arsenic levels in your water and the actions being taken to address the problem. Regular water testing and monitoring will help ensure that the water remains safe for consumption.
Arsenic contamination in groundwater is a serious health concern that can lead to long-term health problems if not addressed promptly. Regular monitoring and testing of the water supply is essential to identify and mitigate the risks.