Hydrogeochemical Evolution and Circulation Mechanisms of Deep Groundwater in a Complex Coal-Bearing Basin: A Case Study of the Soma–Eynez Basin, Western Türkiye

Hydrogeochemical Evolution and Circulation Mechanisms of Deep Groundwater in a Complex Coal-Bearing Basin: A Case Study of the Soma–Eynez Basin, Western Türkiye | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Hydrogeochemical Evolution and Circulation Mechanisms of Deep Groundwater in a Complex Coal-Bearing Basin: A Case Study of the Soma–Eynez Basin, Western Türkiye Celalettin Simsek, Serafettin SAİM, Ali TURKOGLU This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9311189/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 4 You are reading this latest preprint version Abstract This study investigates the hydrogeochemical characteristics, evolution processes, and circulation mechanisms of groundwater in the Soma–Eynez Coal Basin (western Türkiye), where deep underground coal mining is actively conducted. The basin hosts a multi-layered hydrogeological system composed of a shallow volcanic aquifer and a deep confined karstic limestone aquifer, separated by thick, low-permeability Neogene sediments. Isotopic results indicate that all groundwater is of meteoric origin; however, lower tritium values measured in the deep aquifer (1.76–1.8 TU), compared to the shallow aquifer (2.4 TU), suggest longer residence times and possible mixing processes. According to hydrogeochemical facies classification, shallow groundwater is predominantly of the Ca–HCO₃ type, whereas deep groundwater evolves toward Na–Ca–Mg–SO₄ and Na–HCO₃ types. Elevated electrical conductivity values (1000–3000 µS/cm) and high concentrations of Na, SO₄, and B in the deep aquifer reflect intensified water–rock interaction, ion exchange processes, and the dissolution of evaporitic minerals such as gypsum and anhydrite. Strong correlations among Na, HCO₃, and B indicate that mineralization is primarily controlled by prolonged water–rock interaction within the thick Neogene sequence. Saturation index calculations confirm carbonate supersaturation and sulfate undersaturation, indicating the simultaneous occurrence of carbonate precipitation and evaporite dissolution. Seasonal hydrochemical variations further demonstrate that the system exhibits dynamic behavior governed by dilution and re-equilibration processes. The hydrogeological conceptual model suggests that the deep aquifer is predominantly recharged through vertical fault and fracture systems, while lateral recharge remains limited due to thick impermeable units. Long-term groundwater drainage associated with mining activities has caused significant declines in groundwater levels (− 400 to − 500 m), altering the natural flow regime and accelerating hydrogeochemical evolution. Water quality assessments indicate that groundwater from the deep aquifer is unsuitable for drinking purposes due to high salinity and elevated major ion and boron concentrations. Its use for irrigation is also restricted due to salinity and boron hazards. Multi-layered aquifer system Deep coal mining Water–rock interaction Hydrogeochemical evolution Groundwater circulation Full Text Additional Declarations Tables are available in the Supplementary Files section. Supplementary Files TableCaption.docx Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 30 Apr, 2026 Reviewers invited by journal 30 Apr, 2026 Editor assigned by journal 14 Apr, 2026 First submitted to journal 07 Apr, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9311189","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":632516601,"identity":"0548ec89-22a4-459a-b60f-1e0fe6b9fe91","order_by":0,"name":"Celalettin Simsek","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA7ElEQVRIiWNgGAWjYFAC5gaGB0CKjYH5gARY4ABBLYwNDAkMBhJsDGwJMC1AIWK0MDDwGBCnhb+9sfFDQsWfOj7pno83PrYxyPHdSGB/XIFHi8SZg80SCWeADpM5u9lyZhuDseSNBMbGM3i0GEgkNkgktgG1SORuk+ZtY0jcANKCz2UG8g+bfyT+A2nJeSb9t42hnrAWCcY2oEVgLWzSjG0MCQaEtEicSWyzSDhmLNkmkWZs2XNOwnDmmYeNM/Fp4W8/fPjGhxo5fvkZyQ9v/Cizkec7nnzgIz4tGLYyMBCMyVEwCkbBKBgFBAEANjtN2BqSZTUAAAAASUVORK5CYII=","orcid":"","institution":"Dokuz Eylül University Torbali Vocational School: Dokuz Eylul Universitesi Torbali Meslek Yuksekokulu","correspondingAuthor":true,"prefix":"","firstName":"Celalettin","middleName":"","lastName":"Simsek","suffix":""},{"id":632516602,"identity":"9257d9cc-2b8e-4788-8402-92f98949f0c7","order_by":1,"name":"Serafettin SAİM","email":"","orcid":"","institution":"Imbat Mining Co, Soma","correspondingAuthor":false,"prefix":"","firstName":"Serafettin","middleName":"","lastName":"SAİM","suffix":""},{"id":632516603,"identity":"61bd2abf-7127-4ea5-86bd-4e1933c97815","order_by":2,"name":"Ali TURKOGLU","email":"","orcid":"","institution":"Polyak Mining Co.","correspondingAuthor":false,"prefix":"","firstName":"Ali","middleName":"","lastName":"TURKOGLU","suffix":""}],"badges":[],"createdAt":"2026-04-03 09:18:53","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9311189/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9311189/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":108846980,"identity":"9d882298-bbe8-4bcc-8f8d-d6aec53a886a","added_by":"auto","created_at":"2026-05-09 03:44:10","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1253704,"visible":true,"origin":"","legend":"","description":"","filename":"somamakalev4.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9311189/v1_covered_9b43a7d9-3f0f-41e7-814d-1d3f1fffb243.pdf"},{"id":108846979,"identity":"0f054854-1bef-4d4d-8b58-3f632e9326e7","added_by":"auto","created_at":"2026-05-09 03:44:04","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":36046,"visible":true,"origin":"","legend":"","description":"","filename":"TableCaption.docx","url":"https://assets-eu.researchsquare.com/files/rs-9311189/v1/1ee99ad01f2763294001e60e.docx"}],"financialInterests":"\u003cp\u003eTables are available in the Supplementary Files section.\u003c/p\u003e","formattedTitle":"Hydrogeochemical Evolution and Circulation Mechanisms of Deep Groundwater in a Complex Coal-Bearing Basin: A Case Study of the Soma–Eynez Basin, Western Türkiye","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"mine-water-and-the-environment","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"mwen","sideBox":"Learn more about [Mine Water and the Environment](http://link.springer.com/journal/10230)","snPcode":"10230","submissionUrl":"https://www.editorialmanager.com/mwen/default2.aspx","title":"Mine Water and the Environment","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Multi-layered aquifer system, Deep coal mining, Water–rock interaction, Hydrogeochemical evolution, Groundwater circulation","lastPublishedDoi":"10.21203/rs.3.rs-9311189/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9311189/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study investigates the hydrogeochemical characteristics, evolution processes, and circulation mechanisms of groundwater in the Soma\u0026ndash;Eynez Coal Basin (western T\u0026uuml;rkiye), where deep underground coal mining is actively conducted. The basin hosts a multi-layered hydrogeological system composed of a shallow volcanic aquifer and a deep confined karstic limestone aquifer, separated by thick, low-permeability Neogene sediments.\u003c/p\u003e \u003cp\u003eIsotopic results indicate that all groundwater is of meteoric origin; however, lower tritium values measured in the deep aquifer (1.76\u0026ndash;1.8 TU), compared to the shallow aquifer (2.4 TU), suggest longer residence times and possible mixing processes. According to hydrogeochemical facies classification, shallow groundwater is predominantly of the Ca\u0026ndash;HCO₃ type, whereas deep groundwater evolves toward Na\u0026ndash;Ca\u0026ndash;Mg\u0026ndash;SO₄ and Na\u0026ndash;HCO₃ types. Elevated electrical conductivity values (1000\u0026ndash;3000 \u0026micro;S/cm) and high concentrations of Na, SO₄, and B in the deep aquifer reflect intensified water\u0026ndash;rock interaction, ion exchange processes, and the dissolution of evaporitic minerals such as gypsum and anhydrite. Strong correlations among Na, HCO₃, and B indicate that mineralization is primarily controlled by prolonged water\u0026ndash;rock interaction within the thick Neogene sequence.\u003c/p\u003e \u003cp\u003eSaturation index calculations confirm carbonate supersaturation and sulfate undersaturation, indicating the simultaneous occurrence of carbonate precipitation and evaporite dissolution. Seasonal hydrochemical variations further demonstrate that the system exhibits dynamic behavior governed by dilution and re-equilibration processes.\u003c/p\u003e \u003cp\u003eThe hydrogeological conceptual model suggests that the deep aquifer is predominantly recharged through vertical fault and fracture systems, while lateral recharge remains limited due to thick impermeable units. Long-term groundwater drainage associated with mining activities has caused significant declines in groundwater levels (\u0026minus;\u0026thinsp;400 to \u0026minus;\u0026thinsp;500 m), altering the natural flow regime and accelerating hydrogeochemical evolution. Water quality assessments indicate that groundwater from the deep aquifer is unsuitable for drinking purposes due to high salinity and elevated major ion and boron concentrations. Its use for irrigation is also restricted due to salinity and boron hazards.\u003c/p\u003e","manuscriptTitle":"Hydrogeochemical Evolution and Circulation Mechanisms of Deep Groundwater in a Complex Coal-Bearing Basin: A Case Study of the Soma–Eynez Basin, Western Türkiye","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-05-09 03:43:47","doi":"10.21203/rs.3.rs-9311189/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2026-04-30T17:22:17+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-04-30T14:15:54+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-04-14T14:09:33+00:00","index":"","fulltext":""},{"type":"submitted","content":"Mine Water and the Environment","date":"2026-04-08T03:51:11+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"mine-water-and-the-environment","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"mwen","sideBox":"Learn more about [Mine Water and the Environment](http://link.springer.com/journal/10230)","snPcode":"10230","submissionUrl":"https://www.editorialmanager.com/mwen/default2.aspx","title":"Mine Water and the Environment","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"0e19bbdb-26b0-47ed-95a7-0cba24b1e871","owner":[],"postedDate":"May 9th, 2026","published":true,"recentEditorialEvents":[{"type":"reviewerAgreed","content":"","date":"2026-04-30T17:22:17+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-04-30T14:15:54+00:00","index":"","fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-05-09T03:43:47+00:00","versionOfRecord":[],"versionCreatedAt":"2026-05-09 03:43:47","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9311189","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9311189","identity":"rs-9311189","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}