{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,12]],"date-time":"2026-02-12T08:35:10Z","timestamp":1770885310561,"version":"3.50.1"},"reference-count":51,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2025,6,18]],"date-time":"2025-06-18T00:00:00Z","timestamp":1750204800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"FCT (Funda\u00e7\u00e3o para a Ci\u00eancia e Tecnologia)","award":["LA\/P\/0056\/2020 (IMS)"],"award-info":[{"award-number":["LA\/P\/0056\/2020 (IMS)"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Pollutants"],"abstract":"<jats:p>Active and abandoned mining sites are significant sources of heavy metals and metalloid pollution, leading to serious environmental issues. This study assessed the environmental risks posed by potentially toxic elements (PTEs), specifically arsenic (As) and antimony (Sb), in the Technosols (mining residues) of the former Pej\u00e3o coal mine complex in Northern Portugal, a site impacted by forest wildfires in October 2017 that triggered underground combustion within the waste heaps. Our methodology involved determining the \u201cpseudo-total\u201d concentrations of As and Sb in the collected heap samples using microwave digestion with aqua regia (ISO 12914), followed by analysis using hydride generation-atomic absorption spectroscopy (HG-AAS). The concentrations of As an Sb ranging from 31.0 to 68.6 mg kg\u22121 and 4.8 to 8.3 mg kg\u22121, respectively, were found to be above the European background values reported in project FOREGS (11.6 mg kg\u22121 for As and 1.04 mg kg\u22121 for Sb) and Portuguese Environment Agency (APA) reference values for agricultural soils (11 mg kg\u22121 for As and 7.5 mg kg\u22121 for Sb), indicating significant enrichment of these PTEs. Based on average Igeo values, As contamination overall was classified as \u201cunpolluted to moderately polluted\u201d while Sb contamination was classified as \u201cmoderately polluted\u201d in the waste pile samples and \u201cunpolluted to moderately polluted\u201d in the downhill soil samples. However, total PTE content alone is insufficient for a comprehensive environmental risk assessment. Therefore, further studies on As and Sb fractionation and speciation were conducted using the Shiowatana sequential extraction procedure (SEP). The results showed that As and Sb levels in the more mobile fractions were not significant. This suggests that the enrichment in the burned (BCW) and unburned (UCW) coal waste areas of the mine is likely due to the stockpiling of lithic fragments, primarily coals hosting arsenian pyrites and stibnite which largely traps these elements within its crystalline structure. The observed enrichment in downhill soils (DS) is attributed to mechanical weathering, rock fragment erosion, and transport processes. Given the strong association of these elements with solid phases, the risk of leaching into surface waters and aquifers is considered low. This work underscores the importance of a holistic approach to environmental risk assessment at former mining sites, contributing to the development of sustainable remediation strategies for long-term environmental protection.<\/jats:p>","DOI":"10.3390\/pollutants5020015","type":"journal-article","created":{"date-parts":[[2025,6,18]],"date-time":"2025-06-18T04:08:06Z","timestamp":1750219686000},"page":"15","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Assessment of Potential Environmental Risks Posed by Soils of a Deactivated Coal Mining Area in Northern Portugal\u2014Impact of Arsenic and Antimony"],"prefix":"10.3390","volume":"5","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-5928-5598","authenticated-orcid":false,"given":"Marcus","family":"Monteiro","sequence":"first","affiliation":[{"name":"CIQUP\/IMS, Department of Chemistry and Biochemistry, Faculty of Sciences, University of Porto, Rua do Campo Alegre s\/n, 4169-007 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6114-1427","authenticated-orcid":false,"given":"Patr\u00edcia","family":"Santos","sequence":"additional","affiliation":[{"name":"ICT, Department of Geosciences, Environment and Spatial Plannings, Faculty of Sciences, University of Porto, Rua do Campo Alegre s\/n, 4169-007 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4704-2174","authenticated-orcid":false,"given":"Jorge","family":"Espinha Marques","sequence":"additional","affiliation":[{"name":"ICT, Department of Geosciences, Environment and Spatial Plannings, Faculty of Sciences, University of Porto, Rua do Campo Alegre s\/n, 4169-007 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4631-7831","authenticated-orcid":false,"given":"Deolinda","family":"Flores","sequence":"additional","affiliation":[{"name":"ICT, Department of Geosciences, Environment and Spatial Plannings, Faculty of Sciences, University of Porto, Rua do Campo Alegre s\/n, 4169-007 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3709-7478","authenticated-orcid":false,"given":"Manuel","family":"Azenha","sequence":"additional","affiliation":[{"name":"CIQUP\/IMS, Department of Chemistry and Biochemistry, Faculty of Sciences, University of Porto, Rua do Campo Alegre s\/n, 4169-007 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6421-9763","authenticated-orcid":false,"given":"Jos\u00e9 A.","family":"Ribeiro","sequence":"additional","affiliation":[{"name":"CIQUP\/IMS, Department of Chemistry and Biochemistry, Faculty of Sciences, University of Porto, Rua do Campo Alegre s\/n, 4169-007 Porto, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2025,6,18]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"e28357","DOI":"10.1016\/j.heliyon.2024.e28357","article-title":"Sources, effects and present perspectives of heavy metals contamination: Soil, plants and human food chain","volume":"10","author":"Angon","year":"2024","journal-title":"Heliyon"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"126039","DOI":"10.1016\/j.jhazmat.2021.126039","article-title":"Global soil pollution by toxic elements: Current status and future perspectives on the risk assessment and remediation strategies\u2014A review","volume":"417","author":"Khan","year":"2021","journal-title":"J. Hazard. Mater."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"100018","DOI":"10.1016\/j.scenv.2023.100018","article-title":"Toxic heavy metals: A bibliographic review of risk assessment, toxicity, and phytoremediation technology","volume":"2","author":"Naveed","year":"2023","journal-title":"Sustain. Chem. Environ."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"2068","DOI":"10.1007\/s11368-024-03786-x","article-title":"Assessment of mobile mercury concentration in soils of an abandoned coalfield waste pile in Douro region: The Fojo waste pile (Portugal) study case","volume":"24","author":"Monteiro","year":"2024","journal-title":"J. Soils Sediments"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"60","DOI":"10.2478\/intox-2014-0009","article-title":"Toxicity, mechanism and health effects of some heavy metals","volume":"7","author":"Jaishankar","year":"2014","journal-title":"Interdiscip. Toxicol."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"569","DOI":"10.1007\/s00128-016-1907-3","article-title":"Environmental Contamination by Heavy Metals in Region with Previous Mining Activity","volume":"97","author":"Musilova","year":"2016","journal-title":"Bull. Environ. Contam. Toxicol."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"25","DOI":"10.1039\/B711896A","article-title":"Is there a future for sequential chemical extraction?","volume":"133","author":"Bacon","year":"2008","journal-title":"Analyst"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"291","DOI":"10.1007\/s11270-007-9564-0","article-title":"A Review of the Different Methods Applied in Environmental Geochemistry For Single and Sequential Extraction of Trace Elements in Soils and Related Materials","volume":"189","author":"Rao","year":"2008","journal-title":"Water Air Soil Pollut."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"823","DOI":"10.1039\/b207574c","article-title":"Chemical sequential extraction for metal partitioning in environmental solid samples","volume":"4","author":"Filgueiras","year":"2002","journal-title":"J. Environ. Monit."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"365","DOI":"10.1080\/10643380802377992","article-title":"Sequential Selective Extraction Procedures for the Study of Heavy Metals in Soils, Sediments, and Waste Materials\u2014A Critical Review","volume":"40","author":"Hass","year":"2010","journal-title":"Crit. Rev. Environ. Sci. Technol."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"9955","DOI":"10.1007\/s11356-019-04433-6","article-title":"Comparison of different sequential extraction procedures for mercury fractionation in polluted soils","volume":"26","author":"Dong","year":"2019","journal-title":"Environ. Sci. Pollut. Res."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"330","DOI":"10.1016\/j.envpol.2007.06.020","article-title":"Use of the modified BCR three-step sequential extraction procedure for the study of trace element dynamics in contaminated soils","volume":"152","author":"Pueyo","year":"2008","journal-title":"Environ. Pollut."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"57","DOI":"10.1039\/a807854h","article-title":"Improvement of the BCR three step sequential extraction procedure prior to the certification of new sediment and soil reference materials","volume":"1","author":"Rauret","year":"1999","journal-title":"J. Environ. Monit."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"915","DOI":"10.1016\/j.talanta.2007.07.028","article-title":"Simultaneous determination of arsenic, antimony, bismuth and mercury in geological materials by vapor generation-four-channel non-dispersive atomic fluorescence spectrometry","volume":"74","author":"Li","year":"2008","journal-title":"Talanta"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"685","DOI":"10.1016\/j.sab.2008.04.006","article-title":"On-line pre-reduction of pentavalent arsenicals by thioglycolic acid for speciation analysis by selective hydride generation\u2013cryotrapping\u2013atomic absorption spectrometry","volume":"63","author":"Musil","year":"2008","journal-title":"Spectrochim. Acta Part B At. Spectrosc."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"545","DOI":"10.1016\/j.microc.2013.06.009","article-title":"New method for mercury determination in microwave digested soil samples based on cold vapor capacitively coupled plasma microtorch optical emission spectrometry: Comparison with atomic fluorescence spectrometry","volume":"110","author":"Frentiu","year":"2013","journal-title":"Microchem. J."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"77","DOI":"10.1016\/j.microc.2012.03.014","article-title":"Determination of mercury in size fractionated road dust samples by flow injection-cold vapor-atomic absorption spectrometry","volume":"105","author":"Londonio","year":"2012","journal-title":"Microchem. J."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"116677","DOI":"10.1016\/j.trac.2022.116677","article-title":"Current advances of chemical vapor generation in non-tetrahydroborate media for analytical atomic spectrometry","volume":"155","author":"Hu","year":"2022","journal-title":"TrAC Trends Anal. Chem."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"335","DOI":"10.1016\/j.trac.2018.11.017","article-title":"Speciation analysis of antimony in environmental samples employing atomic fluorescence spectrometry\u2014Review","volume":"110","author":"Palacio","year":"2019","journal-title":"TrAC Trends Anal. Chem."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"502","DOI":"10.1016\/j.talanta.2016.12.022","article-title":"On line automated system for the determination of Sb(V), Sb(III), thrimethyl antimony(v) and total antimony in soil employing multisyringe flow injection analysis coupled to HG-AFS","volume":"165","author":"Portugal","year":"2017","journal-title":"Talanta"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"112850","DOI":"10.1016\/j.microc.2025.112850","article-title":"Development of a plasmonic sensor based on imprinted nanogels for quantification of bovine serum albumin in bovine milk","volume":"209","author":"Monteiro","year":"2025","journal-title":"Microchem. J."},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Espinha Marques, J., Narayan, A., Santos, P., Ribeiro, J., Antunes, S.C., Melo, A., Rocha, F., Flores, D., and Mansilha, C. (2024). Hydropedological Characterization of a Coal Mining Waste Deposition Area Affected by Self-Burning. Hydrology, 11.","DOI":"10.3390\/hydrology11050062"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"102026","DOI":"10.1016\/j.eti.2021.102026","article-title":"A review of the environmental chemical behavior, detection and treatment of antimony","volume":"24","author":"Zhang","year":"2021","journal-title":"Environ. Technol. Innov."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"545","DOI":"10.1016\/j.envpol.2017.01.057","article-title":"Antimony as a global dilemma: Geochemistry, mobility, fate and transport","volume":"223","author":"Herath","year":"2017","journal-title":"Environ. Pollut."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"8803","DOI":"10.1039\/D3RA00789H","article-title":"A review on arsenic in the environment: Contamination, mobility, sources, and exposure","volume":"13","author":"Patel","year":"2023","journal-title":"RSC Adv."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"308","DOI":"10.1016\/j.ecoenv.2014.09.009","article-title":"Bioaccessibility of antimony and arsenic in highly polluted soils of the mine area and health risk assessment associated with oral ingestion exposure","volume":"110","author":"Li","year":"2014","journal-title":"Ecotoxicol. Environ. Saf."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"681","DOI":"10.1016\/S1002-0160(19)60843-X","article-title":"Bioavailability of Arsenic and Antimony in Terrestrial Ecosystems: A Review","volume":"29","author":"Bagherifam","year":"2019","journal-title":"Pedosphere"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"743","DOI":"10.1016\/j.envint.2009.01.005","article-title":"Aquatic arsenic: Toxicity, speciation, transformations, and remediation","volume":"35","author":"Sharma","year":"2009","journal-title":"Environ. Int."},{"key":"ref_29","unstructured":"(2012). Soil Quality\u2014Microwave-Assisted Extraction of the Aqua Regia Soluble Fraction for the Determination of Elements (Standard No. ISO 12914:2012)."},{"key":"ref_30","first-page":"362","article-title":"Method 3051A microwave assisted acid digestion of sediments, sludges, soils, and oils","volume":"111","author":"Element","year":"2007","journal-title":"Z. F\u00fcr Anal. Chem."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"107058","DOI":"10.1016\/j.sab.2024.107058","article-title":"Radical theory of hydride atomization and its significance for trace element analysis","volume":"221","year":"2024","journal-title":"Spectrochim. Acta Part B At. Spectrosc."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"3656","DOI":"10.1007\/s11368-020-02694-0","article-title":"Comparison of different sequential extraction procedures to identify and estimate bioavailability of arsenic fractions in soil","volume":"20","author":"Du","year":"2020","journal-title":"J. Soils Sediments"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"402","DOI":"10.1016\/j.chemosphere.2017.03.078","article-title":"Comparison of three sequential extraction procedures for arsenic fractionation in highly polluted sites","volume":"178","author":"Wan","year":"2017","journal-title":"Chemosphere"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"1940","DOI":"10.2134\/jeq2001.1940","article-title":"Fractionation of Arsenic in Soil by a Continuous-Flow Sequential Extraction Method","volume":"30","author":"Shiowatana","year":"2001","journal-title":"J. Environ. Qual."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"7270","DOI":"10.1021\/es060694x","article-title":"Comparison of Antimony Behavior with that of Arsenic under Various Soil Redox Conditions","volume":"40","author":"Mitsunobu","year":"2006","journal-title":"Environ. Sci. Technol."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"3155","DOI":"10.1021\/es2022472","article-title":"Antimony (Sb) and Arsenic (As) in Sb Mining Impacted Paddy Soil from Xikuangshan, China: Differences in Mechanisms Controlling Soil Sequestration and Uptake in Rice","volume":"46","author":"Okkenhaug","year":"2012","journal-title":"Environ. Sci. Technol."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"21","DOI":"10.4103\/2229-5186.79345","article-title":"Methods for the determination of limit of detection and limit of quantitation of the analytical methods","volume":"2","author":"Shrivastava","year":"2011","journal-title":"Chron. Young Sci."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"117","DOI":"10.1016\/j.aca.2005.04.055","article-title":"Determination of trace elements in agricultural soil samples by inductively coupled plasma-mass spectrometry: Microwave acid digestion versus aqua regia extraction","volume":"543","author":"Melaku","year":"2005","journal-title":"Anal. Chim. Acta"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"34","DOI":"10.1016\/j.trac.2017.01.010","article-title":"Comparison of total and aqua regia extractability of heavy metals in sewage sludge: The case study of a certified reference material","volume":"89","author":"Santoro","year":"2017","journal-title":"TrAC Trends Anal. Chem."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"103941","DOI":"10.1016\/j.coal.2022.103941","article-title":"Coal related fires in Portugal: New occurrences and new insights on the characterization of thermally affected and non-affected coal waste piles","volume":"252","author":"Ribeiro","year":"2022","journal-title":"Int. J. Coal Geol."},{"key":"ref_41","doi-asserted-by":"crossref","unstructured":"Costa, M., Moura, H., Pinto de Jesus, A., Su\u00e1rez-Ruiz, I., and Flores, D. (2022). Effects of Magmatic Fluids in Coals of S\u00e3o Pedro da Cova Coalfield, Douro Carboniferous Basin, Portugal: Insights from Inorganic Geochemistry. Minerals, 12.","DOI":"10.3390\/min12020275"},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"5","DOI":"10.1007\/s44274-024-00030-8","article-title":"Environmental pollution indices: A review on concentration of heavy metals in air, water, and soil near industrialization and urbanisation","volume":"2","author":"Swain","year":"2024","journal-title":"Discov. Environ."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"19","DOI":"10.1016\/j.coal.2003.11.002","article-title":"Potential health impacts of burning coal beds and waste banks","volume":"59","author":"Finkelman","year":"2004","journal-title":"Int. J. Coal Geol."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"331","DOI":"10.1016\/0016-2361(95)93464-O","article-title":"Trace elements in coal and their behaviour during combustion in a large power station","volume":"74","author":"Querol","year":"1995","journal-title":"Fuel"},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"6790","DOI":"10.1021\/acs.energyfuels.6b00816","article-title":"Volatilization of Arsenic During Coal Combustion Based on Isothermal Thermogravimetric Analysis at 600\u20131500 \u00b0C","volume":"30","author":"Liu","year":"2016","journal-title":"Energy Fuels"},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"123223","DOI":"10.1016\/j.fuel.2022.123223","article-title":"Volatilization characteristics and relationship of arsenic and sulfur during coal pyrolysis","volume":"315","author":"Xu","year":"2022","journal-title":"Fuel"},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"126729","DOI":"10.1016\/j.talanta.2024.126729","article-title":"Electroanalytical applications of ITIES\u2014A review","volume":"280","author":"Ribeiro","year":"2024","journal-title":"Talanta"},{"key":"ref_48","unstructured":"Joana, T., Jos\u00e9, A.R., Pedro, A.S.J., and Nuno, A.S. (2024, January 7\u201311). Probing molecular affinity with optical tweezers. Proceedings of the SPIE Photonics Europe, Strasbourg, France."},{"key":"ref_49","unstructured":"Pedro, J., Joana, T., Vicente, R., Jos\u00e9, R., and Nuno, S. (2024, January 7\u201311). Automation of optical tweezers: An enabler for single cell analysis and diagnostic. Proceedings of the SPIE Photonics Europe, Strasbourg, France."},{"key":"ref_50","doi-asserted-by":"crossref","unstructured":"Teixeira, J., Ribeiro, J., Silva, N., and Jorge, P. (2024, January 23\u201325). Automated Optical Tweezers for Enhanced Bioparticle Analysis via Combined Scattering and Raman Spectroscopy. Proceedings of the 2024 IEEE Sensors Applications Symposium (SAS), Naples, Italy.","DOI":"10.1109\/SAS60918.2024.10636639"},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"143127","DOI":"10.1016\/j.chemosphere.2024.143127","article-title":"Discarded substrates from soilless hydroponic horticulture as potential amendments for metal-contaminated soils","volume":"364","author":"Pedron","year":"2024","journal-title":"Chemosphere"}],"container-title":["Pollutants"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2673-4672\/5\/2\/15\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,9]],"date-time":"2025-10-09T17:53:58Z","timestamp":1760032438000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2673-4672\/5\/2\/15"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,6,18]]},"references-count":51,"journal-issue":{"issue":"2","published-online":{"date-parts":[[2025,6]]}},"alternative-id":["pollutants5020015"],"URL":"https:\/\/doi.org\/10.3390\/pollutants5020015","relation":{},"ISSN":["2673-4672"],"issn-type":[{"value":"2673-4672","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,6,18]]}}}