TY - JOUR
T1 - Identification of discharge zones and quantification of contaminant mass discharges into a local stream from a landfill in a heterogeneous geologic setting
AU - Milosevic, N.
AU - Thomsen, N.I.
AU - Juhler, R.K.
AU - Albrechtsen, H.-J.
AU - Bjerg, P.L.
N1 - Funding Information:
We thank our DTU Environment colleagues, Bent Henning Skov, Sinh Hy Nguyen, Susanne Kruse, Mona Refstrup, Jens Schaarup Sørensen, Morten Andreasen, Mikael Emil Olsson, and Erik Rønn Lange for assistance with field work and laboratory analysis. Brian Kronvang and Niels Bering Ovesen from National Environment Research Institute of Aarhus University measured stream level and flow and calculated their relationship. Khara Deanne Grieger provided a linguistic review. We gratefully acknowledge the support of Danish Research Council (Grant no. 2104-07-0035 ) and Seventh Framework Program (2007–2013) of European Commission within the GOODWATER Marie Curie Initial Training Network (Grant no. 212683 ).
PY - 2012/6/26
Y1 - 2012/6/26
N2 - Contaminants from Risby Landfill (Denmark) are expected to leach through the underlying geologic strata and eventually reach the local Risby Stream. Identification of the groundwater discharge zone was conducted systematically by an array of methods including studies on site geology and hydrogeology, ground- and surface water flows and landfill leachate tracing from April 2009 to December 2010. Chemical profiling by driven wells and gradients in streambed temperatures was an efficient method to identify the contaminant discharge area. A considerable variation of leachate indicators, redox parameters and xenobiotic organic compounds were revealed in this area because of a complex geological setting with clay till (interbedded sand lenses) and deposits of sand and peat. Concentrations of leachate indicators decreased from the landfill to the stream, implying attenuation processes. Xenobiotic organic compounds were mainly phenoxy acid herbicides, while petroleum hydrocarbons and chlorinated solvents were found at very few boreholes. Findings of putative metabolites of phenoxy acid herbicides suggest degradation under the anaerobic conditions, which dominated inside and beneath the landfill. The groundwater discharge was quantified by two methods: direct collection of discharged groundwater by seepage meters and calculations from measurement of streambed temperature gradients. The landfill impacted the stream seasonally during dry periods when concentrations in the stream reached groundwater concentration levels. A comparison between mass balance for selected stream stretches and upscaled measurements of the contaminant discharge from groundwater into the stream indicated that only a small part of the actual contaminant discharge of the stream could be explained by the inflowing contaminant discharge from groundwater. Surface runoff and seepage from ponds along the stream impacted by landfill interflow may be important pathways as well. The placement of Risby Landfill near a stream and the complex source and geology causing a large spatial variability of leachate compounds are typical for landfill sites so the approaches and findings from Risby Landfill can be applied to other landfill sites. The study highlights that landfills may pose a risk to surface waters and future studies should be directed towards evaluation of both chemical and ecological risk.
AB - Contaminants from Risby Landfill (Denmark) are expected to leach through the underlying geologic strata and eventually reach the local Risby Stream. Identification of the groundwater discharge zone was conducted systematically by an array of methods including studies on site geology and hydrogeology, ground- and surface water flows and landfill leachate tracing from April 2009 to December 2010. Chemical profiling by driven wells and gradients in streambed temperatures was an efficient method to identify the contaminant discharge area. A considerable variation of leachate indicators, redox parameters and xenobiotic organic compounds were revealed in this area because of a complex geological setting with clay till (interbedded sand lenses) and deposits of sand and peat. Concentrations of leachate indicators decreased from the landfill to the stream, implying attenuation processes. Xenobiotic organic compounds were mainly phenoxy acid herbicides, while petroleum hydrocarbons and chlorinated solvents were found at very few boreholes. Findings of putative metabolites of phenoxy acid herbicides suggest degradation under the anaerobic conditions, which dominated inside and beneath the landfill. The groundwater discharge was quantified by two methods: direct collection of discharged groundwater by seepage meters and calculations from measurement of streambed temperature gradients. The landfill impacted the stream seasonally during dry periods when concentrations in the stream reached groundwater concentration levels. A comparison between mass balance for selected stream stretches and upscaled measurements of the contaminant discharge from groundwater into the stream indicated that only a small part of the actual contaminant discharge of the stream could be explained by the inflowing contaminant discharge from groundwater. Surface runoff and seepage from ponds along the stream impacted by landfill interflow may be important pathways as well. The placement of Risby Landfill near a stream and the complex source and geology causing a large spatial variability of leachate compounds are typical for landfill sites so the approaches and findings from Risby Landfill can be applied to other landfill sites. The study highlights that landfills may pose a risk to surface waters and future studies should be directed towards evaluation of both chemical and ecological risk.
KW - Clay till
KW - Groundwater/surface water interaction
KW - Landfill leachate
KW - Mass discharge
KW - Phenoxy acid herbicides
KW - Stream
UR - http://www.scopus.com/inward/record.url?scp=84861572393&partnerID=8YFLogxK
U2 - 10.1016/j.jhydrol.2012.04.012
DO - 10.1016/j.jhydrol.2012.04.012
M3 - Article
SN - 0022-1694
VL - 446-447
SP - 13
EP - 23
JO - Journal of Hydrology
JF - Journal of Hydrology
ER -