The importance of efficiently controlling and monitoring potential toxins in water systems is extremely important. The potential contaminant known as Cadmium (Cd) is a naturally occurring trace metal that is regularly found in various types of ores. Its most common commercial uses are in the metal plating and coating of transportation vessels, household-cooking utensils, machinery and nickel-cadmium batteries (Advanced Purification Engineering Corporation, 2010). As a result of its multitude of uses, there are an equally large number of ways in which Cd can find its way into water systems. The most common of these are leaching, pipeline corrosion, corrosion from transportation vessels, runoff from metal and ore refineries among others. Cd is also capable of resulting in various negative health effects to humans unfortunate enough to consume it. Failure to adequately monitor Cadmium levels can result in numerous unsolicited health outcomes such as: "nausea, vomiting, diarrhea, muscle cramps, salivation, sensory disturbances, liver injury, convulsions, shock and renal failure," and these are only the effects of short-term exposure (Advanced Purification Engineering Corporation, 2010, p. 1). Prolonged exposure to cadmium-infected water can result in life-threatening "kidney, liver, bone and blood damage" (Advanced Purification Engineering Corporation, 2010, p. 1). Additionally, The International Agency for Research on Cancer has recently included Cadmium on its list of carcinogenic substances that are potentially harmful to humans in the category 2A, (NWQMS 2004). As a result of this new classification, the WHO has set the protocol value for Cd in drinking water at 0.003 mg/L (WHO 2004). And the Australian Drinking Water Guideline (ADWG) is even stricter, mandating a value of 0.002 mg/L (NWQMS 2004).
The forthcoming report will proceed to specifically elucidate the most effective means of ensuring water systems' extended protection from the numerous aforementioned unwanted outcomes. This paper will give precise recommendations and guidelines for efficiently collecting and handling water samples through methods like grab sampling and sampling a depth (Green, 2004). By also highlighting some of the most valuable sample extraction techniques, this report will attempt to help in guaranteeing the accuracy of the eventual results. Furthermore, the techniques for intricately analyzing the collected samples will be examined. Also, this report will explain the essentiality of accurate measurement approaches and quality control mechanisms in the laboratory environment (NWQMS 2000). And in keeping with the assurance of accuracy and reliability in sample analysis, this report will conclude by distinctively highlighting the relevant analytical detection limits present in water-based Cadmium deposits. With the comprehensive nature of the forthcoming findings and recommendations, the intricacies and potentialities of Cd levels should be better understood and more easily monitored.
The acquisition of reliable water samples is the foundation of the critical analysis and decision-making process. The ultimate findings and results of any subsequent testing procedures will only be as good and accurate as the samples from whence they came. Water samples potentially containing Cd are most commonly found in drinking water sources, though this report will also attempt to highlight some possible techniques for collection at wastewater sites. As a result, the primary drinking water sampling points that will be utilized are drinking water distribution lines and wells/bores. These locations comprise the majority of spaces where water is directly used for human consumption and are the most common sites suspected to be contaminated by Cd. Also, wastewater sample will conducted in locations directly outside of metal/ore refineries and battery plants. Strategically selecting sampling locations in these areas are highly essential. Such points will include the direct distribution systems such as pipelines outside of consumers' property, the water taps inside of homes, and runoff sources in the case of wastewater (NWQMS 2004). The goal of the two former samplings source locations will be to extensively investigate the contamination from the processes of leaching and corrosion occurring at the main pipelines and the plumbing structures in the household. In the case of samples taken from wells/bores, the objective will be to identify contamination sources in drinking water from land runoff and leaching of soil that may contain Cadmium. All sampling of drinking water sources must follow the guidelines in ADWG, which is quarterly in frequency and conducted at the pre-determined sampling points in the distribution network (NWQMS 2004). Though it is also important to note that more frequent samplings should be conducted immediately following any potentially contaminative or hazardous event.
Additionally, wastewater sampling will be conducted in locations directly outside of metal/ore refineries and battery plants. Though this is a much less common location for Cadmium deposits, ensuring that this potentially harmful element is not present in wastewater sources remains highly essential. The sampling process in these locations will primarily occur in order to examine direct pollution.
This is the most common and basic technique used in sample collection. Accordingly, it is frequently recommended for the accurate location of Cadmium contaminants. Grab samples targeting Cadmium are typically (and most effectively) retrieved from the drinking water treatment and distribution systems (NWQMS 2004). If accomplished properly, sample collection with the grab method can assure the sample quality is representative of the bulk quality. An example of this type of successful sampling completion would be the reliable acquisition of a sampling from a determined sampling location in the distribution pipeline or the outlet of a bore well pump. By strategically researching and selecting specific target sampling points, it is expected that the ultimate sample will be well-mixed, thus having many of the same and/or similar properties as the source water.
According to the mandated guidelines, the minimum sample size for the determination of Cd concentration is 500 mL (NWQMS 2004). All samples collected should be stored in plastic or glass bottles that have been prewashed with 50% HNO3 (NWQMS 2004). This acid washing process is performed for the purpose of dissolving any and all metals that may have been previously attached to the walls of the bottle (such remnants cause analytical biases that can possibly interfere with eventual analyte measurements). The protocol below should be followed in the acid washing process (NWQMS 2000):
1. Wash the bottle and cap with non-ionic, metal-free detergent and tap water.
2. Rinse thoroughly with tap water.
3. Rinse with 50% HNO3, followed by 6.7% of HNO3.
4. Cap and keep until required, but a week as a maximum.
5. Before use, empty the bottle and rinse the inside with metal-free water such as distilled water.
Sampling at Depth
This type of sample extraction is typically utilized in lake and reservoir locations for the purpose of examining freshwater and drinking water sources. Though these source origins are far less common homes of Cadmium deposits, historical data has shown that Cadmium has been found in these locations (Burnsa, Rutherford, & Clayton, 1999). Being that shallow or surface sample cross-sections would not sufficiently represent the total contamination content in these locations, it is necessary to acquire samples from greater depths in order to achieve a more accurate representation of the chemical and elemental composition of these water sources. A very commonly used tool for this process is known as the LaMotte Water Sampling Bottle (Green, 2004). This unique device allows for the extraction of water samples at specific depths (Green, 2004). This instrument is basically comprised of a sample receptacle at the end of a long line with a two-pound weight at the bottom and a stopper above (Green, 2004). There is also a trip line, which opens the receptacle for filling when the desired depth is reached. Many of these devices are also equipped with the LaMotte Model 545 Armored Thermometer for more accurate sample data and temperature readings (Green, 2004). By setting this apparatus to a specific water depth, scientists can monitor different contaminant levels throughout the various degrees of collection sites. And being that different contaminants normally occur in greater or lesser quantities depending on water depth, this can be an extremely effectual tool.
Though wastewater locations are much less frequent locations of Cd contamination, historical research has shown that Cadmium has certainly been found in these locations (Singha, Rastogi, & Hasan, 2005). The most common wastewater sources for Cadmium are metal and ore refineries. Though since most wastewater sampling points are typically overrun with a cornucopia of elements and contaminants. The presence of such a wider range calls for a procedural protocol a bit different from that previously discussed. However, the actual sample collection process is quite similar to the grab sampling process. Although in the case of waste, it is even more important to make certain considerations when collecting samples. For instance, the elemental and molecular composition may change drastically or become biased if collected in a highly turbulent area (Singha, Rastogi, & Hasan, 2005). Additionally, due to the potentially high levels of numerous contaminants, it is recommended that samples be stored in a refrigerated location (after being rinsed and flushed like in the grab process) before the transportation to the laboratory takes place.