{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,1]],"date-time":"2026-05-01T15:03:49Z","timestamp":1777647829999,"version":"3.51.4"},"reference-count":32,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2026,1,27]],"date-time":"2026-01-27T00:00:00Z","timestamp":1769472000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001871","name":"National Funds","doi-asserted-by":"publisher","award":["SFRH\/BD\/121892\/2016"],"award-info":[{"award-number":["SFRH\/BD\/121892\/2016"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sci"],"abstract":"<jats:p>Arsenic (As) accumulation in rice (Oryza sativa L.) is considered a major environmental and food safety concern, particularly in flooded agroecosystems where reducing conditions mobilize As from soils. Portugal is one of Europe\u2019s rice producers, especially in the Tejo, Almansor, and Sorraia valleys. As such, this study evaluates As pathways across 5000 ha of rice fields in the Tagus, Sorraia, and Almansor alluvial plains by combining soil, water, and plant analyses with a geostatistical approach. The soils exhibited consistently elevated As concentrations (mean of 18.9 mg\/kg), exceeding national reference values for agricultural soils (11 mg\/kg) and forming a marked east\u2013west gradient with the highest levels in the Tagus alluvium. Geochemical analysis showed that As is strongly correlated with Fe (r = 0.686), indicating an influence of Fe-oxyhydroxides under oxidizing conditions. The irrigation waters showed low As (mean of 2.84 \u03bcg\/L for surface water and 3.51 \u03bcg\/L for groundwater) and predominantly low sodicity facies, suggesting that irrigation water is not the main contamination vector. In rice plants, As accumulation follows the characteristic organ hierarchy roots &gt; stems\/leaves &gt; grains, with root concentrations reaching up to 518 mg\/kg and accumulating progressively in the maturity phase. Arsenic content in harvested rice grains was 266 \u03bcg\/kg (with a maximum of 413.9 \u03bcg\/kg), being close to EU maximum limits when considering typical inorganic As proportions, assuming 60 to 90% inorganic fraction. Together, the findings highlight that a combined approach is essential, and identify soil geochemistry (and not irrigation water) as the primary source of As transfer in those agroecosystems, due to the flooded conditions that trigger the reductive dissolution of Fe oxides, releasing As. Additionally, the results also identified the need for targeted monitoring in areas of elevated As content in soils and support future mitigation through As speciation analysis, cultivar selection, improved fertilization strategies, and water-management practices such as Alternate Wetting and Drying (AWD), to ensure the long-term food safety.<\/jats:p>","DOI":"10.3390\/sci8020026","type":"journal-article","created":{"date-parts":[[2026,1,27]],"date-time":"2026-01-27T15:41:56Z","timestamp":1769528516000},"page":"26","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Regional Assessment of Arsenic Accumulation in Rice (Oryza sativa L.) Agroecosystems of the Tejo, Almansor and Sorraia Valleys, Portugal"],"prefix":"10.3390","volume":"8","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-7079-9389","authenticated-orcid":false,"given":"Manuela","family":"Sim\u00f5es","sequence":"first","affiliation":[{"name":"Earth Sciences Department, NOVA School of Sciences and Technology, Campus de Caparica, 2829-516 Caparica, Portugal"},{"name":"GeoBioTec Research Center, NOVA University of Lisbon, 2829-516 Caparica, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3770-9892","authenticated-orcid":false,"given":"David","family":"Ferreira","sequence":"additional","affiliation":[{"name":"GeoBioTec Research Center, NOVA University of Lisbon, 2829-516 Caparica, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4210-8867","authenticated-orcid":false,"given":"Ana Coelho","family":"Marques","sequence":"additional","affiliation":[{"name":"Earth Sciences Department, NOVA School of Sciences and Technology, Campus de Caparica, 2829-516 Caparica, Portugal"},{"name":"GeoBioTec Research Center, NOVA University of Lisbon, 2829-516 Caparica, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3944-7240","authenticated-orcid":false,"given":"Ana Rita F.","family":"Coelho","sequence":"additional","affiliation":[{"name":"Earth Sciences Department, NOVA School of Sciences and Technology, Campus de Caparica, 2829-516 Caparica, Portugal"},{"name":"GeoBioTec Research Center, NOVA University of Lisbon, 2829-516 Caparica, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2026,1,27]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"361","DOI":"10.1007\/s40572-019-00249-1","article-title":"Rice Intake and Emerging Concerns on Arsenic in Rice: A Review of the Human Evidence and Methodologic Challenges","volume":"6","author":"Karagas","year":"2019","journal-title":"Curr. 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