Potash mining mountain waste and its contribution to river water salinisation: the case of the Llobregat River, Catalonia, Spain

<p>It is well known that mining activities have negative effects on fluvial ecosystems. Such activities alter the water quality by introducing heavy metals and associated pollutants and alter the sediment regime by creating a point source sediment that may affect the entire basin. </p><p>In the Llobregat River, a medium Mediterranean river basin (ca. 5000 km<sup>2</sup>), potash salt mining activities have been undertaken for several decades. Salinisation of surface river water has become an environmental issue of great concern for the water administrators given that the water of this river supplies half of the population of the metropolitan area of Barcelona (ca. 2,500,000 inhabitants) and it is also used for irrigation in the lowermost part of the river and its delta.</p><p>This study aims to describe the magnitude of the dissolved solids inputs that are detected in the river surface water after rainfall events by means of continuous electrical conductivity monitoring. Electrical conductivity records (EC) were obtained from an automatic water quality monitoring station set by the Water Catalan Authorities and located 3 km downstream from the potash mountain waste.  The study also tries to predict the EC peak according to different hydrometeorological parameters selected from the episodes recorded.</p><p>Data analysed was continuously recorded at 15-minute interval between January 1st, 2018 and September 30th, 2020 and a total of 74 EC episodes were considered. Mean EC of the episodes recorded was 3,488 µS/cm, with a standard deviation of 3,638 µS/cm, and a coefficient of variation of 104.3%. The median was 2,390 µS/cm. Data obtained show that after rainfall events a peak of electrical conductivity in the river is detected. However, it exhibits a high variability in its magnitude, ranging from 939 µS/cm up to 26,900 µS/cm. Despite this, the coefficients of determination of the regression lines between the meteorological variables, such as rainfall intensity or total rainfall amount, and the peak EC exhibit poor correlations (R<sup>2</sup>=0.355 and R<sup>2</sup>=0.229, respectively), although they are significant.</p><p>Results indicate that washload processes in the salt mountain waste take place and reach the river producing extremely high EC peak values during a short period of time. Such values can have harmful effects on the river ecosystem and affect the lowerland river area, where water is diverted for potabilization and irrigation purposes. However, the low correlation between rainfall and EC peak indicates that additional variables intervene in the rainfall-runoff processes and further research is required to fully understand the connectivity and transmission of the salt moutain waste into the river. Understanding such processes and analyasing the consequences on the fluvial system, will probably be the way to tackle the restoration of this enormous impact on this river ecosystem.</p>

Geophysical Characterization of Hydraulic Properties around a Managed Aquifer Recharge System over the Llobregat River Alluvial Aquifer (Barcelona Metropolitan Area)

Managed aquifer recharge using surface or regenerated water plays an important role in the Barcelona Metropolitan Area in increasing storage volume to help operators cope with the runoff variability and unexpected changes in surface water quality that are aggravated by climate change. The specific aim of the research was to develop a non-invasive methodology to improve the planning and design of surface-type artificial recharge infrastructures. To this end, we propose an approach combining direct and indirect exploration techniques such as electrical resistivity tomography (ERT), frequency domain electromagnetics and data from double-ring infiltration tests, trial pits, research boreholes and piezometers. The ERT method has provided much more complete and representative information in a zone where the recharge project works below design infiltration rates. The geometry of the hydrogeological units and the aquifer-aquiclude contact are accurately defined through the models derived from the interpretation of ERT cross-sections in the alluvial aquifer setting. Consequently, prior to the construction of recharge basins, it is highly recommended to conduct the proposed approach in order to identify the highest permeability areas, which are, therefore, the most suitable for aquifer artificial recharge.

What controls the coarse sediment yield to a Mediterranean delta? The case of the Llobregat River (NE Iberian Peninsula)

The human pressure upon an alluvial river in the Mediterranean region has changed its riverine and deltaic landscapes. The river has been channelized in the last 70 years while the delta has been retreating for more than a century (a set of data unknown, so far). The paper concentrates on the fluvial component, trying to connect it to the delta evolution. Is the channelization responsible for the delta retreat? We develop a method to compute the actual bed load transport with real information of the past river morphology. The paper compares the computation with very limited measurements, among which are bulk volumes of trapped material at a modern, deep river mouth. The decrease in sediment availability in the last 30 km of the channelized river is deemed responsible for the decrease in the sediment yield to the delta. Moreover, power development and flood frequency should be responsible for a baseline delta retreat during the 20th century. The sediment trapping efficiency of dams is less important than the flow regulation by dams, in the annual sediment yield. Therefore, it is more effective to dismantle channelization than to pass sediment at dams, to provide sand to the beaches.

Modeling the redox potential during the infiltration in a recharge pond located in the Llobregat river basin

<div> <p>Redox potential measurements are a sink of multiple processes and factors related to the hydrochemistry of a water.  Normally, by themselves, they do not provide enough information to describe all the processes occurring in a system and they are considered only as “an indicator” that combined with a more detailed hydrochemistry can provide information of the driving processes. There are different reasons why these measurement are not quantitatively valid. First of all, sampling plays an important role. The most common method to determine Eh in groundwater is by using an Eh probe and a cell flow, which implies, by itself, mixing of waters. On the other hand, the Eh reproducibility is also conditioned by the amount of processes considered in a numerical model. Eh depends on several geochemical processes, which at the same time, they are depending on flow and heat transport. The last achievements in sensoring science has allowed to develop sensor probes that allows the Eh measurements in a non-invasive and a continuous way.</p> </div><p>Considering this, in this work we have monitored intensively an infiltration pond (in the context of Managed Aquifer Recharge) in order to develop a proper model to reproduce the Eh. The monitoring was based in the use of non-invasive Eh probes, which registered the Eh every 15 min during a year. During that year, four hydrochemical campaigns were also developed in order to quantify the hydrochemistry of the site. On the other hand, the model considered the flow of the system, the heat transport and a set of geochemical processes which were also depending on temperature. The main processes were the generation of organic matter in the own system, the oxidation of organic carbon using different TEAPs, nitrification and different secondary geochemical processes related, specially, to iron and manganese geochemistry.</p>

What controls the coarse sediment yield to a Mediterranean delta The case of the Llobregat river (NE Iberian Peninsula)

The human pressure upon an alluvial river in the Mediterranean region has changed its riverine and deltaic landscapes. The river has been channelized in the last 50 years while the delta is being retreating for more than a century. The paper concentrates on the fluvial component, trying to connect it to the delta evolution. It develops a method to compute the actual bed load transport with real data. The paper compares the computation with measurements and bulk volumes of trapped material at a deep river mouth. Sediment availability in the last 30 km of the river channel is deemed responsible for the decrease in the sediment yield to the delta. Moreover, reforestation is deemed responsible for a baseline delta retreat. The sediment trapping efficiency of dams is less important than the flow regulation by dams, in the annual sediment yield. Therefore, it is more effective a step back from channelisation than to pass sediment at dams, to provide sand to the beaches.

Viromics on Honey-Baited FTA Cards as a New Tool for the Detection of Circulating Viruses in Mosquitoes

Worldwide, emerging and re-emerging infectious diseases (EIDs) are a major burden on public and animal health. Arthropod vectors, with mosquitoes being the main contributors of global disease, transmit more than 70% of the recognized EIDs. To assess new alternatives for arthropod-borne viral diseases surveillance, and for the detection of new viruses, honey-baited Flinders Technology Associates (FTA) cards were used as sugar bait in mosquito traps during entomological surveys at the Llobregat River Delta (Catalonia, Spain). Next generation sequencing (NGS) metagenomics analysis was applied on honey-baited FTA cards, which had been exposed to field-captured mosquitoes to characterize their associated virome. Arthropod- and plant-infecting viruses governed the virome profile on FTA cards. Twelve near-complete viral genomes were successfully obtained, suggesting good quality preservation of viral RNAs. Mosquito pools linked to the FTA cards were screened for the detection of mosquito-associated viruses by specific RT-PCRs to confirm the presence of these viruses. The circulation of viruses related to Alphamesonivirus, Quaranjavirus and unclassified Bunyavirales was detected in mosquitoes, and phylogenetic analyses revealed their similarities to viruses previously reported in other continents. To the best our knowledge, our findings constitute the first distribution record of these viruses in European mosquitoes and the first hint of insect-specific viruses in mosquitoes’ saliva in field conditions, demonstrating the feasibility of this approach to monitor the transmissible fraction of the mosquitoes’ virome. In conclusion, this pilot viromics study on honey-baited FTA cards was shown to be a valid approach for the detection of viruses circulating in mosquitoes, thereby setting up an alternative tool for arbovirus surveillance and control programs.