Investigating Landfill-impacted Groundwater Seepage into Headwater Streams Using Stable Carbon Isotopes


The impact of landfill contaminated groundwater along a reach of a small stream adjacent to a municipal landfill was investigated using stable carbon isotopes as a tracer. Groundwater below the stream channel, groundwater seeping into the stream, groundwater from the stream banks and stream water were sampled and analysed for dissolved inorganic carbon (DIC) and the isotope ratio of DIC (13CDIC). Representative samples of groundwater seeping into the stream were collected using a device (a seepage well) specifically designed for collecting samples of groundwater seeping into shallow streams with soft sediments. The DIC and 13CDIC of water samples ranged from 52 to 205 mg C/L and -16·9 to +5·7 relative to VPDB standard, respectively. Groundwater from the stream bank adjacent to the landfill and some samples of groundwater below the stream channel and seepage into the stream showed evidence of 13C enriched DIC (13CDIC = -2·3 to +5·7), which we attribute to landfill impact. Stream water and groundwater from the stream bank opposite the landfill did not show evidence of landfill carbon (13CDIC = -10·0 to -16·9). A simple mixing model using DIC and 13CDIC showed that groundwater below the stream and groundwater seeping into the stream could be described as a mixture of groundwater with a landfill carbon signature and uncontaminated groundwater. This study suggests that the hyporheic zone at the stream-groundwater interface probably was impacted by landfill contaminated groundwater and may have significant ecological implications for this ecotone.


Geosciences and Geological and Petroleum Engineering

Keywords and Phrases

Dissolved Inorganic Carbon; Landfill; Streams; Tracers; Carbon -- Isotopes; Groundwater; Rivers; Seepage

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Article - Journal

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© 2004 John Wiley & Sons, All rights reserved.

Publication Date

12 May 2004