Contamination from agricultural sources and, in particular, nitrate pollution, is one of the main concerns in groundwater management. However, this type of pollution entails the entrance of other substances into the aquifer, as well as it may promote other processes. In this study, we deal with hydrochemical and isotopic analysis of groundwater samples from four distinct zones in Catalonia (NE Spain), which include 5 different aquifer types, to investigate the influence of fertilization on the overall hydrochemical composition of groundwater. Results indicate that intense fertilizer application, causing high nitrate pollution in aquifers, also homogenize the contents of the major dissolved ions (i.e.; Cl(-), SO4(2-), Ca(2+), Na(+), K(+), and Mg(2+)). Thus, when groundwater in igneous and sedimentary aquifers is compared, significant differences are observed under natural conditions for Cl(-), Na(+) and Ca(2+) (with p-values ranging from <0.001 to 0.038), and when high nitrate concentrations occur, these differences are reduced (most p-values ranged between 0.054 and 0.978). Moreover, positive linear relationships between nitrate and some ions are found indicating the magnitude of the fertilization impact on groundwater hydrochemistry (with R(2) values of 0.490, 0.609 and 0.470, for SO4(2-), Ca(2+) and Cl(-), respectively). Nevertheless, the increasing concentration of specific ions is not only attributed to agricultural pollution, but to their enhancing effect upon the biogeochemical processes that control water-rock interactions. Such results raise awareness that these processes should be evaluated in advance in order to assess an adequate groundwater resources management.Peer ReviewedPostprint (author's final draft

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Intensive pumping in urban coastal areas is a common threat to water resource quality due to seawater intrusion. In those areas where subsurface water resources are not usually used for human consumption or irrigation, intensive pumping is associated with other activities like the lowering of the water table necessary to support underground structures and building foundations. This activity also increases the likelihood of soil settlement that affects building stability and the corrosion of concrete structures due to groundwater salinity. Under these circumstances, the awareness of a certain municipality (Calonge, NE Spain) of the potential effects of groundwater withdrawal upon foundations has led to an integrated approach to anticipate seawater intrusion related to urban development. Geological mapping and correlation of borehole logs, electrical resistivity tomography, and hydrochemical data provide comprehensive knowledge of the geology and hydrogeology of the area and act as screening tools necessary to discern the influence of hydrological processes in coastal areas. Developing Strack's analytical solution, new comprehensive, dimensionless expressions are herein derived to determine the critical pumping rate necessary to prevent seawater intrusion, as well as to reproduce the evolution of the wedge toe and the water table stagnation point under different withdrawal rates. Furthermore, the Dupuit-Forchheimer well discharge formula allows the estimation of the effects of the water table lowering due to such critical pumping in the surrounding building foundations. Field data from the Calonge coastal plain illustrate this approach and provide assessment criteria for future urban development and planning. Temperature (T) is given in C; electrical conductivity (EC) is in mS/cm; and alkalinity (as HCO 3 ), dissolved oxygen (DO) and other major elements/ compounds are in mg/l. Errors based on % ionic balance. *Seawater composition according to a Mediterranean Sea sample from the Costa Brava region (Kruse and Mas-Pla, 2009).

Trace elements appear in natural waters as a result of rock weathering and human activities. Their occurrence is governed by a complex set of geochemical conditions which finally may induce trace element concentrations above health standards. In regional, large-scale aquifers, their presence is representative of the hydrogeological setting of the overall flow path from the recharge zone to the sampling well. In this study, we analyze hydrochemical, including major components and trace elements (Al, As, B, Ba, Cd, Co, Cr, Cu, Hg, Mn, Ni, Sb, Sn, Sr, Pb, Zn), and stable isotopic data from exploitation wells in the Empordà basin (NE Spain). Our goal is to explore the hydrogeological meaning of trace elements as a means to contribute to the understanding of the regional flow dynamics as an initial step to face trace element pollution events. Groundwater data is hence described in the context of each aquifer relating the major hydrochemical facies with their accompanying trace elements. Results point out some expected geochemical relationships as well as some trace element associations that cannot be envisaged from the usual incomplete lithological information of the aquifer. Multivariate statistical analysis, as PCA, provides complementary information about geochemical processes (loadings) and regional occurrence (scores). Such statistical information can be taken as indicative of potential health hazard associated to trace element in groundwater. From a management perspective, such analysis points out which elements should a priori be considered for analysis according to the geological formation that holds the water supply wellThis study has been developed under the Spanish Government Project CGL2011-29975-c04-04 and continued under Project CGL2014-57215-C4-2-R and the University of Girona fund MPCUdG2016/06

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