Over recent decades, Gampaha district, Sri Lanka, has experienced significant urbanisation and industrial growth, increasing groundwater demand due to limited and polluted surface water resources. In 2013, a community uprising in Rathupaswala, a village in Gampaha district, accused a latex glove manufacturing factory of causing groundwater acidity (pH < 4). This study evaluates the spatial and temporal changes in geochemical parameters across three transects in the southern part of Gampaha district to 1) assess the impact of geological formations on groundwater; 2) compare temporal variations in groundwater; and 3) explain acidification via a geochemical model. Seventy-two sample locations were tested for pH, electrical conductivity (EC), and anion concentrations (sulphate, nitrate, chloride and fluoride). Depth to the water table and distance from the sea were measured to study variations across sandy, peaty, lateritic, and crystalline aquifers. Results showed pH readings around 7 for sandy and crystalline aquifers, below 7 for peaty aquifers, and below 5 for lateritic aquifers, with significant water table fluctuations near Rathupaswala area. Principal component analysis revealed three principal components (PCs) explaining 86.0% of the variance. PC1 (40.6%) correlated with pH, EC, and sulphate (saltwater intrusion), while PC2 (32.0%) correlated with nitrates and depth to the water table (anthropogenic nutrient pollution). A geochemical transport model indicated a cone of depression recharged by acidic groundwater from peat-soil aquifers, leading to acidic groundwater in Rathupaswala area. Previous attributions of acidic pH to the over-exploitation of groundwater by the latex factory have been reevaluated; the results suggest natural acidification from prolonged water-rock interactions with iron-rich lateritic aquifers. Groundwater pH is influenced by local climate, geology, topography, and drainage systems. It is recommended that similar water-rock interaction conditions may be present throughout the wet zone of Sri Lanka, warranting detailed studies to confirm this hypothesis.
References
[1]
Adimalla, N., Li, P. and Qian, H. (2018) Evaluation of Groundwater Contamination for Fluoride and Nitrate in Semi-Arid Region of Nirmal Province, South India: A Special Emphasis on Human Health Risk Assessment (HHRA). HumanandEcologicalRiskAssessment: AnInternationalJournal, 25, 1107-1124. https://doi.org/10.1080/10807039.2018.1460579
[2]
Samarasinghe, K. and Samarakoon, M. (2018) Variation of Drinking Water Quality in Rural Areas of Kurunegala District, Sri Lanka. InternationalJournalofEnvironment, AgricultureandBiotechnology, 3, 1104-1113. https://doi.org/10.22161/ijeab/3.3.51
[3]
WHO (2011) Guidelines for Drinking-Water Quality. World Health Organization, 104-108.
[4]
Appleyard, S., Wong, S., Willis-Jones, B., Angeloni, J. and Watkins, R. (2004) Groundwater Acidification Caused by Urban Development in Perth, Western Australia: Source, Distribution, and Implications for Management. Soil Research, 42, 579-585. https://doi.org/10.1071/sr03074
[5]
Maxe, L. (1995) Effects of Acidification on Groundwater in Sweden. Hydrological and Hydrochemical Processes.
[6]
Larsen, F. and Postma, D. (1997) Nickel Mobilization in a Groundwater Well Field: Release by Pyrite Oxidation and Desorption from Manganese Oxides. EnvironmentalScience&Technology, 31, 2589-2595. https://doi.org/10.1021/es9610794
[7]
Clohessy, S., Appleyard, S. and Vogwill, R. (2013) Groundwater Acidification Near the Water Table of the Superficial Aquifer, Gnangara Mound, Swan Coastal Plain, Western Australia. AppliedGeochemistry, 36, 140-152. https://doi.org/10.1016/j.apgeochem.2013.06.003
[8]
Narayanaswami, M.S. (1992) Geochemistry and Genesis of Laterite in Parts of Can-nanore District North Kerala. Ph.D. Thesis, Cochin University of Science and Technology.
[9]
McMahon, P.B. and Chapelle, F.H. (2007) Redox Processes and Water Quality of Selected Principal Aquifer Systems. Groundwater, 46, 259-271. https://doi.org/10.1111/j.1745-6584.2007.00385.x
[10]
Akoachere, R.A.I., Eyong, T.A., Egbe, S.E., Wotany, R.E., Nwude, M.O. and Yaya, O.O. (2019) Geogenic Imprint on Groundwater and Its Quality in Parts of the Mamfe Basin, Manyu Division, Cameroon. JournalofGeoscienceandEnvironmentProtection, 7, 184-211. https://doi.org/10.4236/gep.2019.75016
[11]
Douagui, A.G., Kouamé, I.K., Mangoua, J.M.O., Kouassi, A.K. and Savané, I. (2019) Using Water Quality Index for Assessing of Physicochemical Quality of Quaternary Groundwater in the Southern Part of Abidjan District (Côte d’Ivoire). JournalofWaterResourceandProtection, 11, 1278-1291. https://doi.org/10.4236/jwarp.2019.1110074
[12]
Bulathsinhala, A.U.V.B. and Thoradeniya, B. (2018) Post ‘Rathupaswala Issue’: Neighbouring Community Perceptions of Groundwater. Engineer: JournaloftheInstitutionofEngineers, SriLanka, 51, 85-94. https://doi.org/10.4038/engineer.v51i4.7316
[13]
Premaratne, W.A.P.J. and Tissera, W.S.L. (2015) Hydrochemical Analysis and Eval-uation of Groundwater Quality in Rathupaswala Area in Sri Lanka. Proceedings of the International Postgraduate Research Conference 2015 University of Kelaniya, Kelaniya, 10-11 December 2015, 197.
[14]
Cooray, P.G. (1984) Geology, with Special Reference to the Precambrian. In: Fernando, C.H., Ed., Ecology and Biogeography in Sri Lanka, Springer, 1-34. https://doi.org/10.1007/978-94-009-6545-4_1
[15]
Dahanayake, K. (1982) Laterites of Sri Lanka—A Reconnaissance Study. MineraliumDeposita, 17, 245-256. https://doi.org/10.1007/bf00206474
[16]
Classen, A. and Hesse, A. (1987) Measurement of Urinary Oxalate: An Enzymatic and an Ion Chromatographic Method Compared. ClinicalChemistryandLaboratoryMedicine, 25, 95-100. https://doi.org/10.1515/cclm.1987.25.2.95
[17]
Bandara, S.P.S. (2015) Assessment of Groundwater Quality in Gampaha District with Special Reference to Rathupaswala Area. MSc Thesis, University of Peradeniya.
[18]
Chowdary, V.M., Rao, N.H. and Sarma, P.B.S. (2003) GIS-Based Decision Support System for Groundwater Assessment in Large Irrigation Project Areas. AgriculturalWaterManagement, 62, 229-252. https://doi.org/10.1016/s0378-3774(03)00144-6
[19]
Subba Rao, N. (2007) Iron Content in Groundwaters of Visakhapatnam Environs, Andhra Pradesh, India. EnvironmentalMonitoringandAssessment, 136, 437-447. https://doi.org/10.1007/s10661-007-9698-y
[20]
Wu, J. and Bai, M. (2018) Retraction Notice: Fast Principal Component Analysis for Stacking Seismic Data. JournalofGeophysicsandEngineering, 17, 789. https://doi.org/10.1093/jge/gxz111
[21]
Kusi, K.A., Wiafe, S. and Nsonini, P.A. (2020) Groundwater Quality Assessment of Three Zonal Regions in the Sunyani Municipality. AmericanJournalofEngineeringandAppliedSciences, 13, 21-26. https://doi.org/10.3844/ajeassp.2020.21.26
[22]
Fisher, N.A. (1993) Volunteer Estuary Monitoring: A Methods Manual. US Environ-mental Protection Agency, Office of Water, Office of Wetlands, Oceans, and Watersheds, Oceans and Coastal Protection Division.
[23]
Panabokke, C.R. (1996) Soils and Agro-Ecological Environments of Sri Lanka. 35-101.
[24]
Panabokke, C.R. (2007) Groundwater Conditions in Sri Lanka: A Geomorphic Perspective. National Science Foundation of Sri Lanka.
[25]
Bodrud-Doza, M., Islam, S.M.D., Rume, T., Quraishi, S.B., Rahman, M.S. and Bhuiyan, M.A.H. (2020) Groundwater Quality and Human Health Risk Assessment for Safe and Sustainable Water Supply of Dhaka City Dwellers in Bangladesh. GroundwaterforSustainableDevelopment, 10, Article 100374. https://doi.org/10.1016/j.gsd.2020.100374
