Abstract
The localization of groundwater contaminant sources is the first and most fundamental step when dealing with site contamination problems. This paper presents a novel approach for groundwater pollution source identification in a site with low-velocity groundwater in which a strategy of an artificially enhanced catchment is adopted. The distance from a pumping well (artificial sink) to the source zone (unknown source) is calculated by integrating the concentration time series and well flow. Then, the orientation of the source well is delineated by applying the method of distance intersection. This method is suitable for an approximately homogeneous aquifer with average hydraulic conductivity ranging from 1 × 10−6 to 1 × 10−5 m/s and a contaminant whose transport process can be generalized to convective migration. The developed method was applied to an industrial contaminated site using three pumping wells and two observation wells. The results demonstrated that four potential source positions were identified. Among these, two positions situated near the production workshop were excluded by observation well responses. The remaining two positions located near the drain were identified as preferred treatment sources. Electrical prospecting showed source orientation consistent with the artificially enhanced catchment results. This proved that the method is effective and provides an alternative tool to help solve the problem of source identification in the first stage of remediation in sites with low-velocity groundwater.
Highlights
Groundwater contaminated sites constitute serious threats to water quality
Isotropic, and low-permeability aquifers, the hydraulic gradient formed by a pumping well is higher than in the natural state, so the natural groundwater flow can be ignored during the pumping process
The fitting of concentration time (C-t) series in the three pumping wells demonstrated each well was recharged by a potential source with a higher concentration than the initial value
Summary
Groundwater contaminated sites constitute serious threats to water quality. The pollution source is a key element of conceptual site models. By combining plume information with contaminant migration rules, the source can be located as an inverse problem. When the media is heterogeneous, identification of the contamination source relying on inadequate samples yields imprecise results [15] This is especially true in porous media with low permeability (hydraulic conductivity from 1 × 10−6 to 1 × 10−5 m/s), such as silt or silty sand. Based on inversion assumptions and positions of the wells, the IPT method is suitable for studying plumes when the aquifer has high hydraulic conductivity. In view of the weak hydrodynamic conditions and irregular contamination distribution in low velocity flow fields, here we develop a source identification method based on an artificially enhanced catchment. This article shows the theory, steps, limitations, and field test results of the new method
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