Abstract
This paper explores the temporal variation of a broad suite of micro organic (MO) compounds within hydrologically linked compartments of a lowland Chalk catchment, the most important drinking water aquifer in the UK. It presents an assessment of results from relatively high frequency monitoring at a well-characterised site, including the type and concentrations of compounds detected and how they change under different hydrological conditions including exceptionally high groundwater levels and river flow conditions during 2014 and subsequent recovery. This study shows for the first time that within the Chalk groundwater there can be a greater diversity of the MOs compared to surface waters. Within the Chalk 26 different compounds were detected over the duration of the study compared to 17 in the surface water. Plasticisers (0.06–39μg/L) were found to dominate in the Chalk groundwater on 5 visits (38.4%) accounting for 14.5% of detections but contributing highest concentrations whilst other compounds dominated in the surface water. Trichloroethene and atrazine were among the most frequently detected compounds. The limit for the total pesticide concentration detected did not exceed EU/UK prescribed concentration values for drinking water. Emerging organic compounds such as caffeine, which currently do not have water quality limits, were also detected. The low numbers of compounds found within the hyporheic zone highlight the role of this transient interface in the attenuation and breakdown of the MOs, and provision of an important ecosystem service.
Highlights
In the last few decades there has been a growing interest in the occurrence of micro-organic (MO) contaminants in the terrestrial and aquatic environment, and in their environmental fate and potential toxicity (Halling-Sørensen et al, 1998; Kolpin et al, 2002; Kümmerer, 2009)
This study has captured the behaviour of MOs during the on-set of and subsequent recovery following the extreme high groundwater levels in the winter of 2013/2014 with high frequency monthly sampling
Trace MOs were detected in all hydrological compartments in a chalk lowland catchment including the hyporheic zone, groundwater and surface water;
Summary
In the last few decades there has been a growing interest in the occurrence of micro-organic (MO) contaminants in the terrestrial and aquatic environment, and in their environmental fate and potential toxicity (Halling-Sørensen et al, 1998; Kolpin et al, 2002; Kümmerer, 2009). A number of recent studies looking at MOs in vulnerable Chalk karstic systems have been published (Hillebrand et al, 2014; Reh et al, 2013), as well as studies focussed on the attenuation of selected MOs by Hillebrand et al (2015). Research in these karstic settings has highlighted the transient nature of MO contamination and shows the need for greater temporal resolution if effective monitoring is to be undertaken in comparable hydrologic settings. With the development of broad screening techniques (e.g. Lapworth et al, 2015; Wode et al, 2015) it is no longer necessary to be restricted to small numbers of target compounds as has often been the case in previous studies to date
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