none 10.2113/JEEG13.1.27 Environmental and Engineering Geophysical Society Environmental and Engineering Geophysical Society 2613 31845190 59784 2025120912320278200 10.32389 2025-12-09T17:32:09Z 2008-03-03T14:38:57Z 7 Journal of Environmental and Engineering Geophysics 1943-2658 1083-1363 03 2008 03 01 2008 03 01 2008 13 1 Fred Kofi Boadu Department of Civil and Environmental Engineering, Duke University 1 1 Durham, NC 27708 Frederick Owusu-Nimo Department of Civil and Environmental Engineering, Duke University 1 1 Durham, NC 27708 Aboagye Menyeh Department of Physics, Kwame Nkrumah University of Science and Technology 2 2 Kumasi Ghana Abstract The role of fractures in nitrate contamination of fractured groundwater aquifers at farmlands within the Nsawam district (Ghana) is investigated using azimuthal square-array resistivity measurements. The study covers seven farming communities where azimuthal resistivity surveys (ARS) were conducted at sites with exposed rocks (outcrops) to measure real and imaginary parts of the electrical conductivity of the rocks, which are then used to provide estimates of anisotropic coefficients and fracture porosities. At each outcrop, fracture orientations, apertures and lengths were measured and used directly to obtain the porosities and specific surface areas of the fractures. Linear regression models were then developed between the specific surface area of the fractures and the electrical parameters. At selected well locations, azimuthal resistivity surveys were performed and the developed regression models were used to estimate porosities and specific surface areas of the subsurface fractures. Groundwater samples were collected from the selected wells to determine the concentration levels of nitrates. The estimated porosities and specific surface areas of the subsurface fractures correlate with concentration levels of nitrate in the groundwater. The investigations suggest that nitrate concentration levels in groundwater in the study area tend to be higher in wells where the specific surface area of the fracture system are lower. Also, wells with lower fracture porosities tend to have lower concentration levels of nitrates. The establishment of linkages between subsurface fracture parameters obtained non-invasively from surface geophysics and nitrate concentration levels is a useful result that can be utilized in environmental impact assessment in complex fractured terrain, such as that of the study area. 03 2008 03 01 2008 03 01 2008 27 37 10.2113/JEEG13.1.27 https://pubs.geoscienceworld.org/jeeg/article/13/1/27/139322/Nitrate-Contamination-in-Groundwater-at-Farmlands https://pubs.geoscienceworld.org/eegs/jeeg/article-pdf/13/1/27/3011563/27.pdf https://pubs.geoscienceworld.org/eegs/jeeg/article-pdf/13/1/27/3011563/27.pdf https://pubs.geoscienceworld.org/jeeg/article/13/1/27/139322/nitrate-contamination-in-groundwater-at-farmlands http://library.seg.org/doi/abs/10.2113/JEEG13.1.27 Journal of Applied Geophysics Boadu 44 103 2000 10.1016/S0926-9851(99)00020-8 Predicting the transport properties of fractured rocks from seismic information: Numerical experiments: Geophysics Boadu 70 B35 2005 10.1190/1.2073888 Determining subsurface fracture characteristics from azimuthal resistivity surveys: A case study at Nsawam, Ghana: Geophysical Prospecting Börner 44 583 1996 10.1111/j.1365-2478.1996.tb00167.x Evaluation of transport and storage properties in the soil and groundwater zone from induced polarization measurements: The nature and properties of soils Brady 2002 Journal of Applied Geophysics Busby 59 261 2006 10.1016/j.jappgeo.2005.10.004 The application of time-lapse azimuthal apparent resistivity measurements for the prediction of coastal cliff failure: Hydrogeology Journal Dapaah-Siakwan 8 405 2000 10.1007/PL00010976 Hydrogeologic framework and borehole yield in Ghana: Degnan 54 2001 Geophysical investigations of well fields to characterize fractured-bedrock aquifers in Southern New Hampshire: Geophysical Prospecting Habberjam 20 249 1972 10.1111/j.1365-2478.1972.tb00631.x The effects of anisotropy on square array resistivity measurements: HACH DR 2500 spectrophotometer handbook Hach Company 1995 Nitrate, mid range, Cadmium reduction method (Method 8039): Quarterly Journal of Engineering Geology Hossain 14 17 1992 Prediction of permeability of fissured tills: Balkema, Rotterdam, 610 pp Kesse 1985 The mineral and rock resources of Ghana: Ground Water Lane 33 476 1995 10.1111/j.1745-6584.1995.tb00304.x Use of a square-array direct current resistivity method to detect fractures in crystalline bedrock in New Hampshire: CRC Press Leaf 317 1996 The role of nitrates and nitrite in human cancer: Journal of Applied Geophysics Matias 49 185 2002 10.1016/S0926-9851(01)00113-6 Square array anisotropy measurements and resistivity sounding interpretation: Ground Water Ritzi 30 774 1992 10.1111/j.1745-6584.1992.tb01563.x Relation between anisotropic transmissivity and azimuthal resistivity surveys in shallow fractured carbonate flow systems: Physical properties of rocks: Fundamentals and principles of petrophysics Schön 1996 Contribution of electrical prospecting to the geophysical study of discontinuous media Sehli 1990 Ground Water Taylor 26 464 1988 10.1111/j.1745-6584.1988.tb00413.x Characterizing jointed systems by azimuthal resistivity surveys: Water Resources Research Institute (WRRI) 1994 Water Resources Research Institute (WRRI) 1996 Water Resources Research Wels 30 2547 1994 10.1029/94WR01128 Retardation of sorbing solutes in fractured media: Health criteria and other supporting information, vol. 2 WHO 1996 Guidelines for drinking water quality: