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Emerging contaminants in Danish groundwater

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Geological Survey of Denmark and Greenland Report 2005/49

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Danish groundwater is the source for almost all drinking water production in Denmark. Groundwater monitoring is thus important in order to ensure the custumer with clean drinking water. During the last decades the numbers of analysis has keept increasing ­ reflecting an increased knowledge and concern over important contaminants. However some analysis has also been removed from the analysis program often reflecting that the contaminant only very infrequently has been detected. Finally, the expences connected with the total number of contaminants being analysed should be constantly minimised.

The present report can be seen as an attemt to review scientific litterature and other relevant sources to get a list of likely contaminants of Danish groundwater ­not presently beeing monitored. Danish autorities has working groups concluding which contaminants to include on the list of analysed contaminants. Such "emerging contaminants" can be broadly defined as any synthetic or naturally occurring chemical or any microorganism that is not commonly monitored in the environment but has the potential to enter the environment and cause known or suspected adverse ecological and (or) human health effects. In some cases, release of emerging chemical or microbial contaminants to the environment has likely occurred for a long time, but may not have been recognized until new detection methods were developed. In other cases, synthesis of new chemicals or changes in use and disposal of existing chemicals can create new sources of emerging contaminants.

The report points out that some pesticides and degradation products could be considered to be included in the Danish monitoring system. Four degradation products from triazine herbicides that have not been analysed in the Danish monitoring system have been found in US groundwater. Further metabolites from the herbicides bromoxynil and ioxynil have been found to be persistant in Danish soils, and might be mobile in soil.

Estrogens originating from livestock manure has been shown to leach trough Danish fractured soil at concentration many times the effect level of estrogen on fish. This estrogen source relating to specialised livestock production is not ­ like its human ancestor ­ passed through a sevage plant with efficient estrogen degrading microbial communities.

A Danish study on presence of fecale indicator bacteria in private wells shows that 25% of all wells has high concenrations of these fecale indicator bacteria. Patogenic microorganisms has not been monitored for in Danish groundwater, but field trials in Ireland have demonstrated significant leaching of patogenic bacteria following deposition of live stock manure om farmland. Other animal breeded patogens, like cryptosporium or giardia, are frequently found outside Denmark in drinkingwater based on surface water. This group of patogens is frequently present in livestock manure but has not been monitored for in Den- mark with the exception of pinpoint analysis to validate methods.

Pharmaceuticals are present in large amounts in most livestock manure but their degradation and movement in soils is not well described. 8 different pharmaceuticals have been identified as the most likely contaminants originating from manure. Among different human related pharmaceuticals 3 compounds are identified.

Emerging groundwater contaminants
Finally several other industrial compounds like antibacterial compounds and synthetic musk products have been detected in surface water, but no measurements have been attempted in groundwater samples.

In the future the use of genetically modified plants that produce compounds like pharmaceuticals or Bt toxin should be considered in relation to groundwater contamination. Presently no such production has been started and the compounds are thus not risk assessed.
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