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Aquifers harbor unique and highly adapted species, contributing to critical ecological processes and services. Understanding the key factors driving invertebrate assemblages in aquifers is a challenging task that, traditionally, has primarily been achieved in karst aquifers. This study aimed to uncover the factors influencing the composition and functionality of groundwater crustaceans in a volcanic aquifer of central Italy. We adopted a multidisciplinary approach, combining hydrogeology, geology, microbiology, and ecology, and found that the aquifer consisted of three adjacent groundwater bodies (GWBs) with different geochemistry (i.e., sulfate-depleted, K-rich and earth-alkaline) and microbial characteristics that remained consistent over the study period. We also unveiled significant differences in both the taxonomic and functional composition of groundwater crustaceans across the three GWBs and these patterns were consistent over time. Notably, the sulfate-depleted GWB lacked groundwater-obligate species, burrowers, stenothermal and moderately stenothermal species, while the K-rich and earth-alkaline GWBs had different species with similar functions related to locomotion, diet, and feeding habits. Stenothermal and moderately stenothermal crustacean species were only found in the K-rich GWB, which lacked epigean species. Major ions (SO4, Ca, NO3, and K), trace elements (B, Al, V, Se, and Ba), and microbial factors related to microbial cells with low nucleic acid (LNA cells) and carbohydrate catabolic profiles were the main descriptors of groundwater-obligate species abundances. Our findings revealed a significant correlation between the abundances of groundwater-obligate crustaceans and LNA cells, thus suggesting a selective feeding of groundwater invertebrate species on the aquatic microbial community. Our research emphasizes the need to consider diverse hydrogeological contexts within individual aquifers. Potential avenues for future research should further consider food web dynamics in groundwater communities and their impact on carbon and nutrient cycling. [ABSTRACT FROM AUTHOR]

Inorganic compounds in groundwater may derive from both natural processes and anthropogenic activities. The assessment of natural background levels (NBLs) is often useful to distinguish these sources. The approaches for the NBLs assessment can be classified as geochemical (e.g., the well-known pre-selection method) or statistical, the latter involving the application of statistical procedures to separate natural and anthropogenic populations. National Guidelines for the NBLs assessment in groundwater have been published in Italy (ISPRA 155/2017), based mainly on the pre-selection method. The Guidelines propose different assessment paths according to the sample size in spatial/temporal dimension and the type of the distribution of the pre-selected dataset, taking also into account the redox conditions of the groundwater body. The obtained NBLs are labelled with a different confidence level in function of number of total observations/monitoring sites, extension of groundwater body and aquifer type (confined or unconfined). To support the implementation of the Guidelines, the on-line tool evaluation of natural background levels (eNaBLe), written in PHP and using MySQL as DBMS (DataBase Management System), has been developed. The main goal of this paper is to describe the functioning of eNaBLe and test the tool on a case study in central Italy. We calculated the NBLs of As, F, Fe and Mn in the southern portion of the Mounts Vulsini groundwater body, within the volcanic province of Latium (Central Italy), also separating the reducing and oxidizing facies. Specific results aside, this study allowed to verify the functioning and possible improvements of the online tool and to identify some criticalities in the procedure NBLs assessment at the groundwater body scale [ABSTRACT FROM AUTHOR]

Groundwater represents the largest reservoir of all the freshwaters available on earth (excluding glaciers and ice caps). In Europe, groundwater supplies about the 75% of inhabitants for drinking use and it is also largely used for industry and agriculture. Since groundwater moves slowly through the subsurface, the impacts of anthropogenic activities can last for a long time, threatening the good quality of groundwater. The described context highlights the importance to preserve or improve the groundwater quality. To this aim, the EU policy (Water Framework Directive 2000/60/EC, Groundwater Directive 2006/118/EC) requires that "any significant and sustained upward trend in the concentration of any pollutant should be identified and reversed", because they would lead to the failure of one or more of the WFD's environmental objectives. Hence, appropriate measures should be applied to revert these trends and the reversal should be statistically demonstrated. A guideline for trend and trend reversal assessment has been recently published in Italy, based on the EU and Italian policy requirements. The suggested procedure examines annual concentration values at the available monitoring sites. The trend analysis is carried out through the Mann-Kendall test. In order to compute the statistical significance (set at 90%) the effective sample size has been taken into account. The trend slope, calculated with the Sen's method, is used to forecast the concentration scenarios at 2021 and 2027 (WFD 2nd and 3rd cycle end). The Pettitt test, largely used for the changing point assessment in climatology, was suggested for the demonstration of the trend reversal. In this communication, we present Trendy, a web-based platform facilitating the implementation of the Italian guideline at the groundwater body (GWB) scale. Trendy identifies the presence of an upward trend, calculates its statistical significance and value (as mg/L/year) and the expected concentration values (as mg/L) at 2021 and 2027 at each monitoring site. Further, it calculates the chemical status of the GWB at the two WFD cycle ends to assess the environmental significance of the trend. In addition, both a Pettitt test and a Mann-Kendall test have been implemented in order to examine the trend reversal. Finally, Trendy provides a map with the localization of the monitoring sites, differently colored as for the trend results. In order to test the efficiency of the tool with real data, a case study from an Italian groundwater body is presented. Its user-friendliness makes Trendy a useful tool for the reporting to the European Commission about the existence of upward trend in the groundwater bodies defined at risk, according to the Water Framework Directive. [ABSTRACT FROM AUTHOR]

This study explores the co-existence of arsenic and fluoride in a volcanic-sedimentary aquifer in central Italy, aiming at identifying the risk areas for human health and the most likely processes deductible at regional/groundwater body scale leading to the observed co-contamination in groundwater.The study area is located in Latium (Central Italy) where undersaturated alkali-potassic formations largely outcrop, belonging to three different volcanic apparatus of Plio-Pleistocene age.Geochemical data from groundwater at 398 wells or springs are analyzed through statistical methods including clustering/PCA and geostatistical analysis. 29% of the sampled groundwaters exceeds the drinking water standard for F (1.5 mg/L), while 55% exceeds that for As (10.0 µg/L). Multivariate statistics suggest a widespread process of water-rock interaction with the K-alkaline volcanic formations releasing As, F, K, Si, V, Rb and PO4 to the groundwater. As and F show a good correlation (Pearson's r = 0.61) and define a separate component, suggesting that their background in groundwater might be governed by a common process.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 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 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. [ABSTRACT FROM AUTHOR]

The EU Water Framework Directive (WFD) and the Groundwater Directive (GWD) establish the necessity for EU Member States to assess the chemical status of their groundwater bodies (GWB) by setting Threshold Values (TVs) taking into account natural background levels (NBLs) when they occur due to natural hydro-geological reasons. Background Level has been defined in the GWD as "the concentration of a substance or the value of an indicator in a groundwater body corresponding to no, or very minor, anthropogenic alterations to undisturbed conditions".The EU FP6 BRIDGE project provides methodological approaches for assessing the threshold values (TV) and the NBL in groundwater bodies. Mainly, the BRIDGE methods are established either on a purely statistical approach, suggesting that the NBL can be determined by population separation techniques or on a simplified pre-selection method. The latter method is based on markers of human activities such as nitrates or other anthropogenic contaminants; the samples exceeding a fixed threshold value of the marker are in advance excluded. On the "pristine" unaffected water samples dataset, a value is chosen as NBL (e.g. 90th, 95th or 97.7th percentile). In 2017, a National Guideline for the NBL assessment in groundwater bodies was published in Italy. The procedure is based mainly on the preselection method but different assessment paths are proposed according to the redox conditions of the groundwater body, the sample size in both the spatial and temporal dimension and the type of the distribution, normal or not, of the pre-selected dataset. The complexity of the schema was essential because of the great heterogeneity of the different GWB monitoring data. For this reason, moreover, the obtained NBLs are labelled with a different confidence level in function of: number of total observations or number of total monitoring sites, extension of groundwater body and aquifer type (confined or unconfined). For GWBs characterized by NBLs with low confidence levels, further monitoring activities are requested.To provide support to operators involved in the use of the Guidelines and to achieve a harmonization of procedures between the different structures involved, eNaBLe, an on-line tool, was developed at IRSA. The complete procedure, written in PHP and using MySQL as DBMS, is arranged into three different blocks: i) Selection of the calculation parameters (redox facies separation parameter and relative threshold, marker threshold, time series analysis method, confidence level assignment method); ii) NBL calculation for all the chemical parameters that show concentration values exceeding the relative TV using the calculation parameters previously selected. The different basic procedures (data validation, preselection, outliers management, time series analysis, normality test, etc) are written as separate modules to match the different assessment paths provided by the Guidelines; iii) Graphical output of the results The tool is still under testing for a thorough verification of all the possible variants in dataset structures and GWB conceptual models, also taking into account the suggestions of the stakeholders. [ABSTRACT FROM AUTHOR]