| Title | Arsenic-fluoride co-contamination in groundwater: Background and anomalies in a volcanic-sedimentary aquifer in central Italy |
| Abstract | In a volcanic-sedimentary aquifer in central Italy, we investigate the co-existence of arsenic and fluoride in groundwater, aiming at identifying the most probable processes deductible at regional/groundwater body scale leading to the observed co-contamination in groundwater. Further, the areas at risk for human health where high concentrations can produce a significant risk to human health have been investigated. The study area is located in Latium (Central Italy) where silica-undersaturated alkali-potassic formations of Plio-Pleistocene age largely outcrop above marine and continental sand and clay deposits (Neogene) and continental alluvial deposits (Lower Pleistocene-Middle Pleistocene). Geochemical data from groundwater at 322 wells and 76 springs have been analyzed through statistical methods including clustering/PCA and geostatistical analysis. The results show exceedances of the drinking water standards for F (1.5 mg/L) and As (10.0 ?g/L) in 29% and 55% of the sampled groundwater, respectively. Multivariate statistics suggest a widespread process of water-rock interaction with the K-alkaline volcanic formations releasing As, F, K, Si, V, Rb and PO to the groundwater. As and F show a good correlation (Pearson's r = 0.61, Spearman's r = 0.59) and define a separate PCA component, confirming that their background in groundwater might be governed by a common process. Kriging interpolations have been used to study the spatial distribution of the two parameters, identifying areas with the highest concentrations and highest probability of exceeding the standards for human consumption. Moreover, by resampling the As-F data with the jackknife technique it was possible to identify the variations of their correlation index in the study area, due to specific As or F anomalies. While in the peripheral areas of the volcanic districts, dominated by sedimentary deposits, the As-F correlation index does not present important fluctuations, Indicator Kriging shows specific As or F correlation anomalies within the volcanic groundwater bodies and along the Tyrrhenian coastline. These anomalies seem to correspond to the zones with the highest thermal flux and/or are located near important structural lineaments. Fluoride correlation anomalies close to mining sites (fluorite) have also been observed. We hypothesize that, unlike the regional co-contamination, these local anomalies are related to the upwelling of geothermal fluids along fracture/fault systems that mix with cold groundwater, or to the interaction with mineral deposits particularly enriched of these elements. |
| Source | Journal of geochemical exploration 217, pp. 1–14 |
| Keywords | Water resources management Contamination Q-Q plot Cluster analysis Kriging |
| Journal | Journal of geochemical exploration |
| Editor | Elsevier, Amsterdam, Paesi Bassi |
| Year | 2020 |
| Type | Articolo in rivista |
| DOI | 10.1016/j.gexplo.2020.106590 |
| Authors | Parrone D.; Ghergo S.; Frollini E.; Rossi D.; Preziosi E. |
| Text | 427547 2020 10.1016/j.gexplo.2020.106590 Scopus 2 s2.0 85087492846 Water resources management Contamination Q Q plot Cluster analysis Kriging Arsenic fluoride co contamination in groundwater Background and anomalies in a volcanic sedimentary aquifer in central Italy Parrone D.; Ghergo S.; Frollini E.; Rossi D.; Preziosi E. IRSA CNR, Water Research Institute National Research Council, Via Salaria km 29.300, PB 10, Monterotondo, Rome, 00015, IRSA CNR, Water Research Institute National Research Council, Via Salaria km 29.300, PB 10, 00015 Monterotondo Rome , Italy, , Italy In a volcanic sedimentary aquifer in central Italy, we investigate the co existence of arsenic and fluoride in groundwater, aiming at identifying the most probable processes deductible at regional/groundwater body scale leading to the observed co contamination in groundwater. Further, the areas at risk for human health where high concentrations can produce a significant risk to human health have been investigated. The study area is located in Latium Central Italy where silica undersaturated alkali potassic formations of Plio Pleistocene age largely outcrop above marine and continental sand and clay deposits Neogene and continental alluvial deposits Lower Pleistocene Middle Pleistocene . Geochemical data from groundwater at 322 wells and 76 springs have been analyzed through statistical methods including clustering/PCA and geostatistical analysis. The results show exceedances of the drinking water standards for F 1.5 mg/L and As 10.0 g/L in 29% and 55% of the sampled groundwater, respectively. Multivariate statistics suggest a widespread process of water rock interaction with the K alkaline volcanic formations releasing As, F, K, Si, V, Rb and PO to the groundwater. As and F show a good correlation Pearson s r = 0.61, Spearman s r = 0.59 and define a separate PCA component, confirming that their background in groundwater might be governed by a common process. Kriging interpolations have been used to study the spatial distribution of the two parameters, identifying areas with the highest concentrations and highest probability of exceeding the standards for human consumption. Moreover, by resampling the As F data with the jackknife technique it was possible to identify the variations of their correlation index in the study area, due to specific As or F anomalies. While in the peripheral areas of the volcanic districts, dominated by sedimentary deposits, the As F correlation index does not present important fluctuations, Indicator Kriging shows specific As or F correlation anomalies within the volcanic groundwater bodies and along the Tyrrhenian coastline. These anomalies seem to correspond to the zones with the highest thermal flux and/or are located near important structural lineaments. Fluoride correlation anomalies close to mining sites fluorite have also been observed. We hypothesize that, unlike the regional co contamination, these local anomalies are related to the upwelling of geothermal fluids along fracture/fault systems that mix with cold groundwater, or to the interaction with mineral deposits particularly enriched of these elements. 217 Published version http //www.scopus.com/record/display.url eid=2 s2.0 85087492846 origin=inward 06/06/2020 Articolo in rivista Elsevier 0375 6742 Journal of geochemical exploration Journal of geochemical exploration J. geochem. explor. danieleparrone PARRONE DANIELE eleonorafrollini FROLLINI ELEONORA stefano.ghergo GHERGO STEFANO elisabetta.preziosi PREZIOSI ELISABETTA david rossi ROSSI DAVID |
