Abstract
Nationwide sampling campaign of treated drinking water of groundwater origin was designed and implemented in Denmark in 2013. The main purpose of the sampling was to obtain data on the spatial variation of iodine concentration and speciation in treated drinking water, which was supplied to the majority of the Danish population. This data was to be used in future exposure and epidemiologic studies. The water supply sector (83 companies, owning 144 waterworks throughout Denmark) was involved actively in the planning and implementation process, which reduced significantly the cost and duration of data collection. The dataset resulting from this collaboration covers not only iodine species (I−, IO3−, TI), but also major elements and parameters (pH, electrical conductivity, DOC, TC, TN, F−, Cl−, NO3−, SO42−, Ca2+, Mg2+, K+, Na+) and a long list of trace elements (n = 66). The water samples represent 144 waterworks abstracting about 45% of the annual Danish groundwater abstraction for drinking water purposes, which supply about 2.5 million Danes (45% of all Danish residents). This technical note presents the design, implementation, and limitations of such a sampling design in detail in order (1) to facilitate the future use of this dataset, (2) to inform future replication studies, or (3) to provide an example for other researchers.
Highlights
The aim of this technical note is to provide a thorough account on the design of a nationwide drinking water sampling campaign implemented in Denmark in 2013
The main purpose of the sampling campaign was to inform about the spatial variation of iodine concentrations and speciation in Danish drinking water
The highly cited studies on iodine in Danish drinking water preceding our sampling campaign lack this thoroughness: Pedersen et al [8] took tap water samples from laboratories spread through Denmark (n = 55, locations only shown on low resolution map); Andersen, Petersen, and Laurberg [9] collected samples from Danish waterworks (n = 22), choosing them to verify low and high drinking water iodine contents when compared with their previous study [8]; Rasmussen, Larsen, and Ovesen [10] collected tap water from what they denoted as “41 evenly distributed localities in the country” which were neither listed nor mapped
Summary
The aim of this technical note is to provide a thorough account on the design of a nationwide drinking water sampling campaign implemented in Denmark in 2013. The highly cited studies on iodine in Danish drinking water preceding our sampling campaign lack this thoroughness: Pedersen et al [8] took tap water samples from laboratories spread through Denmark (n = 55, locations only shown on low resolution map); Andersen, Petersen, and Laurberg [9] collected samples from Danish waterworks (n = 22), choosing them to verify low and high drinking water iodine contents when compared with their previous study [8]; Rasmussen, Larsen, and Ovesen [10] collected tap water from what they denoted as “41 evenly distributed localities in the country” which were neither listed nor mapped Another major drawback of these iodine-drinking water sampling campaigns was that they did not account for the specifics of Danish drinking-water supply system, which we have addressed in our work. We foresee that the details provided in this technical note will facilitate the future use of this “historical” dataset and will inform potential replication studies in Denmark
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