This guide has been developed to provide sufficient information to plan and carry out field groundwater sampling of a high standard, ensuring that only representative, high integrity samples are collected and submitted for laboratory analysis. The main aims of the guide are to provide a comprehensive practical overview covering the basic elements of effective groundwater sampling, provide simple and efficient methods for monitoring groundwater systems, and outline procedures for sampling from the bore site to delivery to the laboratory.
Groundwater contains a variety of chemical constituents at different concentrations. The majority of soluble constituents in groundwater come from soluble minerals in soils and sedimentary rocks, with a smaller portion originating from the atmosphere and surface water bodies (Waterwatch, 2005). Understanding the composition of groundwater is essential for various purposes such as environmental monitoring, resource management, and public health assessment. In order to accurately assess the quality and characteristics of groundwater, it is crucial to conduct proper sampling techniques. This guide will provide a comprehensive overview of the key factors to consider when sampling bore water.
Chemical Composition of Groundwater
Groundwater is made up of various chemical constituents, with the majority of ionic species accounting for its salinity or total dissolved solids (TDS). The major ionic species include positively charged cations such as sodium (Na+), potassium (K+), calcium (Ca2+), and magnesium (Mg2+), as well as negatively charged anions like chloride (Cl-), sulfate (SO4^2-), bicarbonate (HCO3^-), and nitrate (NO3^-). These ionic species form the basis for understanding the salinity and mineralization levels of groundwater. By measuring and analyzing these constituents, it is possible to assess the overall quality and suitability of groundwater for various purposes.
Chemical signatures of groundwater, including concentrations and isotopic ratios, can provide valuable insights into groundwater processes. Isotopic methods have gained significant attention as tracers in hydrogeology, although it is crucial to validate any interpretation with other chemical, hydraulic, geophysical, or geological approaches. Due to the complexity of most hydrogeological situations, a multi-parameter approach is often necessary. The hydrogeochemistry of groundwater can be used to derive parameters such as recharge, discharge, and mixing rates. For example, changes in groundwater chemistry can indicate the movement of water, providing information on water residence time in the saturated zone, identifying recharge processes, and determining the source of recharge water. Additionally, the composition of major ions, particularly chloride concentrations, plays a significant role in recharge studies in the unsaturated zone, offering quantitative estimates that are difficult or costly to measure using other methods.
Microbial Contamination in Groundwater
Apart from chemical constituents, groundwater also contains a wide range of microbial organisms, similar to those found in surface soils and waters. These microbes comprise bacteria, fungi, and protozoa, representing various physiological types. While most of these microorganisms are harmless, there is a risk of pathogenic viruses, bacteria, and protozoans infiltrating groundwater from domestic, agricultural, and other anthropogenic activities (Plazinska, 2000). This highlights the importance of monitoring and assessing microbial contamination in bore water samples. Proper sampling techniques and laboratory analysis can help identify and quantify the presence of pathogens, ensuring the safety and quality of groundwater for human consumption and other uses.
Sampling bore water for groundwater analysis requires careful planning and execution to ensure accurate and representative results. This guide has provided an overview of the key factors to consider when sampling groundwater, including the chemical composition of groundwater, the use of chemical and isotopic methods for understanding groundwater processes, and the importance of assessing microbial contamination. By following the guidelines outlined in this guide, researchers, environmental professionals, and water resource managers can obtain reliable and meaningful data from bore water samples. Proper sampling techniques contribute to effective groundwater monitoring, resource management, and the protection of public health.