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Demonstrating trend reversal of groundwater quality in relation to time of recharge determined by 3H/3He

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Author: Visser, A. · Broers, H.P. · Grift, B. van der · Bierkens, M.F.P.
Type:article
Date:2007
Institution: TNO Bouw en Ondergrond
Source:Environmental Pollution, 3, 148, 797-807
Identifier: 240109
Keywords: Geosciences · 3H/3He · Groundwater age · Groundwater quality · Monitoring · Nitrate · Trends · Agricultural wastes · Helium · Nitrates · Water pollution · Water quality · Groundwater age · Groundwater quality · Quality monitoring networks · Recharging (underground waters) · ground water · helium · helium 3 · nitrate · tritium · agricultural land · European Union · groundwater · groundwater pollution · helium isotope · hydrogen isotope · legislation · nitrate · pollution monitoring · recharge · water quality · water resource · age determination · agricultural waste · aquifer · article · European Union · law · Netherlands · trend study · water analysis · water contamination · water pollutant · water quality · water sampling · Benelux · Eurasia · Europe · Netherlands · Western Europe

Abstract

Recent EU legislation is directed to reverse the upward trends in the concentrations of agricultural pollutants in groundwater. However, uncertainty of the groundwater travel time towards the screens of the groundwater quality monitoring networks complicates the demonstration of trend reversal. We investigated whether trend reversal can be demonstrated by relating concentrations of pollutants in groundwater to the time of recharge, instead of the time of sampling. To do so, we used the travel time to monitoring screens in sandy agricultural areas in the Netherlands, determined by 3H/3He groundwater dating. We observed that concentrations of conservative pollutants increased in groundwater recharged before 1985 and decreased after 1990. Thereby, we demonstrated trend reversal of groundwater quality. From this research we concluded that 3H/3He dating can be used to facilitate (re)interpretation of existing groundwater quality data. The presented approach is widely applicable in areas with unconsolidated granular aquifers and large agricultural pressures on groundwater resources. © 2007 Elsevier Ltd. All rights reserved.