Citation: Mustafa, O.; Mahmmud, R.; Sracek, O.; Seeyan, S. Geogenic Sources of Arsenic and Fluoride in Groundwater: Examples from the Zagros Basin, the Kurdistan Region of Iraq. Water 2023, 15, 1981. https://doi.org/10.3390/w15111981 Academic Editor: Domenico Cicchella Received: 5 April 2023 Revised: 2 May 2023 Accepted: 19 May 2023 Published: 23 May 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). water Article Geogenic Sources of Arsenic and Fluoride in Groundwater: Examples from the Zagros Basin, the Kurdistan Region of Iraq Omed Mustafa 1,2, * , Rebar Mahmmud 3 , Ondra Sracek 3 and Shwan Seeyan 4 1 Research Center, University of Sulaimani, Sulaimani 46001, Kurdistan Region, Iraq 2 Department of Civil and Structural Engineering, University of Sheffield, Broad Lane, Sheffield S1 3JD, UK 3 Department of Geology, Faculty of Science, Palacky University Olomouc, 17. listopadu 12, 771 46 Olomouc, Czech Republic; rebar.mahmmud@upol.cz (R.M.); ondrej.sracek@upol.cz (O.S.) 4 Soil and Water Department, Agriculture Engineering Science College, Salahaddin University-Erbil, Erbil 44001, Kurdistan Region, Iraq; shwan.seeyan@su.edu.krd * Correspondence: omed.mustafa@univsul.edu.iq Abstract: Groundwater is one of the crucial water resources for domestic, agriculture and other purposes in the Kurdistan Region of Iraq, which is counted as a semiarid region with seasonal precipitation in winter. The geogenic source of arsenic and fluoride in groundwater has been studied in the Kurdistan Region of Iraq, which is a part of the Zagros Basin, using the hydrogeochemical method. The analysis results showed that the concentrations of arsenic and fluoride range from 0.19 to 7.8 μg/L and from 0.01 to 2.1 mg/L, respectively. The hydrogeochemical characteristics of the groundwater in the studied area were connected to the fluoride F − and arsenic As concentrations for understanding their sources and behavior. The hydrogeochemical relations between F and As indicate geogenic sources and relatively simple aquifer conditions. Some samples may indicate the presence of contamination sources in addition to geogenic sources. Considering the WHO guidelines, the concentrations of As in most of the samples do not exceed the WHO limit, but the F in some samples shows a higher concentration than the WHO limit, indicating a serious risk of fluorosis in some spots. Connecting the changes in F concentrations to depth and aquifer types, a higher F concentration is associated with an intergranular aquifer and decreases in a karst aquifer. The speciation of F − and As is controlled by pH and redox conditions. Adsorption, cation exchange, and the dissolution of carbonate minerals with the possible dissolution of fluorite are the most dominant geochemical processes that control the concentrations of As and F − in groundwater. The principal sources of F − and As in the study area seem to be geogenic. Keywords: geogenic; arsenic; fluoride; groundwater; karst; Zagros Basin 1. Introduction Geogenic arsenic (As) and fluoride (F − ) are observed worldwide in groundwater [1,2] and groundwater also represents the main source of their intake [3]. A high As concen- tration in drinking and irrigation water usually enters the food chain and causes health problems [4]. Arsenic can be derived from anthropogenic and geogenic sources, but the latter causes larger groundwater contamination. As is released from the oxidation of sul- fide minerals in sedimentary rocks (mostly shale with mean values of 28 ppm), which is higher than those of igneous and metamorphic rocks, by the reductive dissolution of ferric oxyhydroxides, and is also a component of thermal waters [5,6]. Geogenic sources of As are arsenic minerals such as arsenopyrite, orpiment, realgar, claudetite, arsenolite, pentoxide, scorodite, and arsenopalledenite. Alluvial deposits rich in organic matter driving reductive dissolution of ferric oxyhydroxides with adsorbed As are major sources of As in sedimen- tary formations in countries such as Bangladesh and West Bengal in India [5]. Besides this, industrial waste, coal combustion, oil, cement, phosphate, fertilizers, mine tailing, smelting, ore processing, metal extraction, metal purification, chemicals, glass, leather, textiles, alkalis, Water 2023, 15, 1981. https://doi.org/10.3390/w15111981 https://www.mdpi.com/journal/water