SEGH Articles

Flux Based Management of a Groundwater Pollution: from Mass Flux Measurements to Regulatory Decisions

01 August 2011
Goedele Verrydt won the Springer / Hemphill Prize for Student Oral Presentation at SEGH 2011 in Ormskirk, UK.

 

Goedele Verreydt, M.Sc. in Environmental Engineering (2004), commenced her PhD in the Department of Biology at the University of Antwerp in January 2008. Her PhD research concerns the determination and calculation of groundwater contaminant mass fluxes in the frame of a groundwater management, which she performs in the research group Land and Water Management at the Flemish Institute for Technological Research (VITO), Mol, Belgium.

The management of contaminated groundwater is very challenging. Most decisions regarding groundwater pollutions are driven by contaminant concentrations. Since concentration estimates may be highly uncertain and do not include the fluctuations caused by spatially and temporally varying hydrologic conditions, these strategies can be improved by additionally considering contaminant mass fluxes (mass of contaminants passing per unit time per unit area) and contaminant mass discharges (sum of all mass flux measures across an entire plume). The contaminant mass that effectively reaches a downgradient receptor, determines the actual risks for the receptor and should therefore be monitored on site. The combined monitoring of contaminant mass fluxes and groundwater fluxes along a control plane is possible with Passive Flux Meters (PFMs), recently developed passive sampling devices that are installed in monitoring wells for a certain period of time.

 

The main objectives of this study are:

  • to delineate a robust interpretation method for the measurement and calculation of groundwater contaminant fluxes, based on mass flux measurement with Passive Flux Meters (PFMs);
  • to define a clear strategy that supports regulatory decisions in a flux and risk based groundwater management.

The PFM consists of a permeable sorbent infused with soluble tracers packed in a nylon mesh tube. The measurements of the captured contaminants and the remaining resident tracer on the sorbent are used to estimate respectively contaminant and groundwater fluxes.

To calibrate and validate the PFMs, lab as well as field experiments are performed. In addition, the measured water fluxes and contaminant mass fluxes are compared to the results obtained by traditional measurement techniques. The proposed management strategy is based on a source-path-receptor approach.

The PFM has proven to be a valuable instrument for the measurement of contaminant mass flux in groundwater. The extrapolation options of the PFM flux data are defined. Mass discharge can be estimated by integrating the PFM mass flux data throughout the control plane, which converts the individual flux values to a time-stamped cumulative flux (or discharge value). Further, a theoretical framework for a flux based management strategy is set by introducing the term CMDmax (maximum accepted contaminant mass discharge) at a predefined plane of compliance, i.e. a control plane orthogonal to the main flow direction and upgradient the receptor. The proposed strategy includes remedial action if the CMDmax is exceeded.

 G. Verreydt1,2, I. Van keer1 and J. Bronders1

1VITO, Land and Water Management, Boeretang 200, 2400 Mol, Belgium

2Artesis University College of Antwerp, Paardenmarkt 92, 2000 Antwerpen

 goedele.verreydt@vito.be

 Figure shows Mrs. Verreydt retrieving a PFM during a field demonstration in Rijmenam, Belgium.

 Annable, L.D., K. Hatfield, J. Cho, H. Klammler, B.L. Parker, J.A. Cherry and P.S.C. Rao. 2005. Field-Scale Evaluation of the Passive Flux Meter for Simultaneous Measurement of Groundwater and Contaminant Fluxes. Environmental Science & Technology 39(18): 7194-7201.     

Verreydt, G., Bronders, J., Van Keer, I., Diels, L. & Vanderauwera, P. (2010) Passive samplers for monitoring VOCs in groundwater and the prospects related to mass flux measurements. Ground Water Monitoring and Remediation 30(2): 114-126.

Keep up to date

Submit Content

Members can keep in touch with their colleagues through short news and events articles of interest to the SEGH community.

Science in the News

Latest on-line papers from the SEGH journal: Environmental Geochemistry and Health

  • Editorial 2018-12-11
  • Chemical fractionation of heavy metals in fine particulate matter and their health risk assessment through inhalation exposure pathway 2018-12-11

    Abstract

    Samples of PM2.5 were collected from an urban area close to a national highway in Agra, India and sequentially extracted into four different fractions: water soluble (F1), reducible (F2), oxidizable (F3) and residual fraction (F4) for chemical fractionation of arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), nickel (Ni) and lead (Pb). The metals were analyzed by inductively coupled plasma optical emission spectroscopy in each fraction. The average mass concentration of PM2.5 was 93 ± 24 μg m−3.The total concentrations of Cr, Pb, Ni, Co, As and Cd in fine particle were 192 ± 54, 128 ± 25, 108 ± 34, 36 ± 6, 35 ± 5 and 8 ± 2 ng m−3, respectively. Results indicated that Cd and Co had the most bioavailability indexes. Risk Assessment Code and contamination factors were calculated to assess the environmental risk. The present study evaluated the potential Pb hazard to young children using the Integrated Exposure Uptake Biokinetic Model. From the model, the probability density of PbB (blood lead level) revealed that at the prevailing atmospheric concentration, 0.302 children are expected to have PbB concentrations exceeding 10 μg dL−1 and an estimated IQ (intelligence quotient) loss of 1.8 points. The predicted blood Pb levels belong to Group 3 (PbB < 5 μg dL−1). Based on the bioavailable fractions, carcinogenic and non-carcinogenic risks via inhalation exposure were assessed for infants, toddlers, children, males and females. The hazard index for potential toxic metals was 2.50, which was higher than the safe limit (1). However, the combined carcinogenic risk for infants, toddlers, children, males and females was marginally higher than the precautionary criterion (10−6).

  • Effects of steel slag and biochar amendments on CO 2 , CH 4 , and N 2 O flux, and rice productivity in a subtropical Chinese paddy field 2018-12-07

    Abstract

    Steel slag, a by-product of the steel industry, contains high amounts of active iron oxide and silica which can act as an oxidizing agent in agricultural soils. Biochar is a rich source of carbon, and the combined application of biochar and steel slag is assumed to have positive impacts on soil properties as well as plant growth, which are yet to be validated scientifically. We conducted a field experiment for two rice paddies (early and late paddy) to determine the individual and combined effects of steel slag and biochar amendments on CO2, CH4, and N2O emission, and rice productivity in a subtropical paddy field of China. The amendments did not significantly affect rice yield. It was observed that CO2 was the main greenhouse gas emitted from all treatments of both paddies. Steel slag decreased the cumulative CO2 flux in the late paddy. Biochar as well as steel slag + biochar treatment decreased the cumulative CO2 flux in the late paddy and for the complete year (early and late paddy), while steel slag + biochar treatment also decreased the cumulative CH4 flux in the early paddy. The biochar, and steel slag + biochar amendments decreased the global warming potential (GWP). Interestingly, the cumulative annual GWP was lower for the biochar (55,422 kg CO2-eq ha−1), and steel slag + biochar (53,965 kg CO2-eq ha−1) treatments than the control (68,962 kg CO2-eq ha−1). Total GWP per unit yield was lower for the combined application of steel slag + biochar (8951 kg CO2-eq Mg−1 yield) compared to the control (12,805 kg CO2-eq Mg−1 yield). This study suggested that the combined application of steel slag and biochar could be an effective long-term strategy to reduce greenhouse gases emission from paddies without any detrimental effect on the yield.