Evaluating the potential use of a dairy industry residue to induce denitrification in polluted water bodies: a flow-through experiment

Improving the effectiveness and economics of strategies to remediate groundwater nitrate pollution is a matter of concern. In this context, the addition of whey into aquifers could provide a feasible solution to attenuate nitrate contamination by inducing heterotrophic denitrification, while recycling an industry residue. Before its application, the efficacy of the treatment must be studied at laboratory-scale to optimize the application strategy in order to avoid the generation of harmful intermediate compounds. To do this, a flow-through denitrification experiment using whey as organic C source was performed, and different C/N ratios and injection periodicities were tested. The collected samples were analyzed to determine the chemical and isotopic composition of N and C compounds. The results proved that whey could promote denitrification. Nitrate was completely removed when using either a 3.0 or 2.0 C/N ratio. However, daily injection with C/N ratios from 1.25 to 1.5 seemed advantageous, since this strategy decreased nitrate concentration to values below the threshold for water consumption while avoiding nitrite accumulation and whey release with the outflow. The isotopic results confirmed that nitrate attenuation was due to denitrification and that the production of DIC was related to bacterial whey oxidation. Furthermore, the isotopic data suggested that when denitrification was not complete, the outflow could present a mix of denitrified and nondenitrified water. The calculated isotopic fractionation values (ε15NNO3/N2 and ε18ONO3/N2) might be applied in the future to quantify the efficiency of the bioremediation treatments by whey application at field-scale

Numerical modeling of enhanced biodenitrification in a laboratory flow-through experiment

High concentration of nitrate (NO3) in water resources has become a widespread and important environmental contaminant, being anthropogenic nitrogen input the principal source of NO3− pollution (Arauzo, 2017). Underanaerobic conditions, microbial reduction of NO3 to N2(g) to oxidize dissolved organic carbon (DOC) is the principal NO3 attenuation process in groundwater aquifers (Matchett et al., 2019)

Nitrate and Nitrite Attenuation by Fe(II) Minerals: Biotic and Abiotic Reactions

Nitrate (NO3-) pollution of groundwaterhas become a relevant issue and anenvironmental priority as it is related toecological and human health problems(Rivett et al. 2008) and its concentration is still above the threshold limit of 50mg/L in many areas (Nitrate Directive, 91/676/EEC). Contamination sources of NO3 - are linked to extensive use of fertilizers, inappropriate placement of animal waste and spills from septic system effluents

Feasibility of using rural waste products to increase the denitrification efficiency in a surface flow constructed wetland

A surface flow constructed wetland (CW) was set in the Lerma gully to decrease nitrate (NO3−) pollution from agricultural runoff water. The water flow rate and NO3− concentration were monitored at the inlet and the outlet, and sampling campaigns were performed which consisted of collecting six water samples along the CW flow line. After two years of operation, the NO3− attenuation was limited at a flow rate of ~2.5 L/s and became negligible at ~5.5 L/s. The present work aimed to assess the feasibility of using rural waste products (wheat hay, corn stubble, and animal compost) to induce denitrification in the CW, to assess the effect of temperature on this process, and to trace the efficiency of the treatment by using isotopic tools. In the first stage, microcosm experiments were performed. Afterwards, the selected waste material was applied in the CW, and the treatment efficiency was evaluated by means of a chemical and isotopic characterization and using the isotopic fractionation (ε) values calculated from laboratory experiments to avoid field-scale interference. The microcosms results showed that the stubble was the most appropriate material for application in the CW, but the denitrification rate was found to decrease with temperature. In the CW, biostimulation in autumn-winter promoted NO3− attenuation between two weeks and one month (a reduction in NO3− between 1.2 and 1.5 mM was achieved). After the biostimulation in spring-summer, the attenuation was maintained for approximately three months (NO3− reduction between 0.1 and 1.5 mM). The ε15NNO3/N2 and ε18ONO3/N2 values obtained from the laboratory experiments allowed to estimate the induced denitrification percentage. At an approximate average flow rate of 16 L/s, at least 60% of NO3− attenuation was achieved in the CW. The field samples exhibited a slope of 1.0 for δ18O-NO3− versus δ15N-NO3−, similar to those of the laboratory experiments (0.9-1.2). Plant uptake seemed to play a minor role in NO3− attenuation in the CW. Hence, the application of stubble in the CW allowed the removal of large amounts of NO3− from the Lerma gully, especially when applied during the warm months, but its efficacy was limited to a short time period (up to three months)

Characterisation of the natural attenuation of chromium contamination in the presence of nitrate using isotopic methods. A case study from the Matanza-Riachuelo river basin, Argentina

The groundwater contamination by hexavalent chromium (Cr(VI)) in a site of the Matanza-Riachuelo River basin (MRB), Argentina, has been evaluated by determining the processes that control the natural mobility and attenuation of Cr(VI) in the presence of high nitrate (NO3−) contents. The groundwater Cr(VI) concentrations ranged between 1.9E-5 mM and 0.04 mM, while the NO3− concentrations ranged between 0.5 mM and 3.9 mM

The role of siderite on abiotic nitrite reduction by dissolved Fe(II)

Iron redox reactions affect the fate and transformation of groundwater NO3-. Fe(II) present in groundwater as dissolved Fe(II) or Fe(II) sorbed onto mineral surfaces is oxidised into Fe(III) (oxyhydr)oxides using NO3- as an electron acceptor in anoxic conditions by biotic or abiotic means (Bryce et al., 2018). N2O is produced as an end product during abiotic nitrate-reducing Fe(II) oxidation (NRFO) (Wang et al., 2019). NO2-, an intermediate product during NO3- reduction by biotic or abiotic means, is chemically very reactive and readily reduced to N2O by abiotic means (Wankel et al., 2017). Studies have shown that Fe(II) minerals such as iron-rich smectites, green rust and siderite are reactive and can enhance abiotic NO2- reduction (Grabb et al., 2017). The occurrence of abiotic NO2- reduction leads to the relative segregation of the lighter and heavy isotopes of N and O (kinetic isotope fractionation, ε) (Chen & MacQuarrie, 2005) providing an effective tool to quantify abiotic NO2- reduction processes. In the light of this, batch experiments were performed to assess the potential of micro-sized siderite to enhance abiotic NO2- reduction in laboratory batch experiments

Use of nitrogen and oxygen isotopes of dissolved nitrate to trace field-scale induced denitrification efficiency throughout an in-situ groundwater remediation strategy

In the framework of the Life+ InSiTrate project, a pilot-plant was established to demonstrate the viability of inducing in-situ heterotrophic denitrification to remediate nitrate (NO3−)-polluted groundwater. Two injection wells supplied acetic acid by pulses to an alluvial aquifer for 22 months. The monitoring was performed by regular sampling at three piezometers and two wells located downstream. In the present work, the pilot-plant monitoring samples were used to test the usefulness of the isotopic tools to evaluate the efficiency of the treatment. The laboratory microcosm experiments determined an isotopic fractionation (ε) for N-NO3− of −12.6 and for O-NO3− of −13.3 . These ε15NNO3/N2 and ε18ONO3/N2 values were modelled by using a Rayleigh distillation equation to estimate the percentage of the induced denitrification at the pilot-plant while avoiding a possible interference from dilution due to non-polluted water inputs. In some of the field samples, the induced NO3− reduction was higher than 50% with respect to the background concentration. The field samples showed a reduced slope between δ18O-NO3− and δ15N-NO3− (0.7) compared to the laboratory experiments (1.1). This finding was attributed to the reoxidation of NO2− to NO3− during the treatment. The NO3− isotopic characterization also permitted the recognition of a mixture between the denitrified and partially or non-denitrified groundwater in one of the sampling points. Therefore, the isotopic tools demonstrated usefulness in assessing the implementation of the field-scale induced denitrification strategy

Basement and cover architecture in the Central Pyrenees constrained by gravity data

A new gravity survey (1164 gravity stations and 180 samples for density analysis) combined with two new geological cross sections has been carried out in a sector of the Central Pyrenees in order to improve the characterization of basement and cover architecture. From North to South, the study area comprises the southern half of the Axial Zone and the northernmost part of the South-Pyrenean Zone. New gravity data were combined with previous existing databases to obtain the Bouguer and residual anomaly maps of the study area. The two cross sections, oriented NNE–SSW, were built from field data and previous surficial and subsurface data and cross the La Maladeta plutonic complex. The residual anomaly map shows values ranging from −18 to 16 mGal and anomalies mainly oriented N120E. The two 2.5D modelled cross sections show similar observed gravity curves coinciding with similar interpreted structural architecture. Data show a gravity high oriented N120E coinciding with the Orri basement thrust sheet and an important gravity depression, with the same orientation, coinciding with the leading edge at depth of the Rialp basement thrust sheet and interpreted as linked to a large subsurface accumulation of Triassic evaporites. The volume at depth of the La Maladeta and Arties granites has been constrained through gravity modelling. This work highlights that the combination of structural geology and gravity modelling can help to determine the structural architecture of an orogen and localize accumulations of evaporites at depth.This work is part of the project CGL2017-84901-C2-2-P funded by MCIN/AEI/10.13039/501100011033 and “ERDF A way of making Europe” and project PID2020-114273GB-C22 funded by MCIN/AEI/10.13039/501100011033 from Spanish Ministry of Science, Innovation and Universities. Seequent has provided us the GM-SYS module of the Oasis Montaj. The authors acknowledge the contribution of José María Llorente and Agustin González for the acquisition of the gravity data. We thank to Aigüestortes National park and Alt Pirineu Natural park their logistic support. We thank anonymous reviewer for improving the content in the manuscript. This study represents a contribution to GeoAp Research Group (E01-20R) (Aragón Government).Peer reviewe

Whole-genome sequencing reveals host factors underlying critical COVID-19

Critical COVID-19 is caused by immune-mediated inflammatory lung injury. Host genetic variation influences the development of illness requiring critical care1 or hospitalization2,3,4 after infection with SARS-CoV-2. The GenOMICC (Genetics of Mortality in Critical Care) study enables the comparison of genomes from individuals who are critically ill with those of population controls to find underlying disease mechanisms. Here we use whole-genome sequencing in 7,491 critically ill individuals compared with 48,400 controls to discover and replicate 23 independent variants that significantly predispose to critical COVID-19. We identify 16 new independent associations, including variants within genes that are involved in interferon signalling (IL10RB and PLSCR1), leucocyte differentiation (BCL11A) and blood-type antigen secretor status (FUT2). Using transcriptome-wide association and colocalization to infer the effect of gene expression on disease severity, we find evidence that implicates multiple genes—including reduced expression of a membrane flippase (ATP11A), and increased expression of a mucin (MUC1)—in critical disease. Mendelian randomization provides evidence in support of causal roles for myeloid cell adhesion molecules (SELE, ICAM5 and CD209) and the coagulation factor F8, all of which are potentially druggable targets. Our results are broadly consistent with a multi-component model of COVID-19 pathophysiology, in which at least two distinct mechanisms can predispose to life-threatening disease: failure to control viral replication; or an enhanced tendency towards pulmonary inflammation and intravascular coagulation. We show that comparison between cases of critical illness and population controls is highly efficient for the detection of therapeutically relevant mechanisms of disease

Characterisation of the natural attenuation of chromium contamination in the presence of nitrate using isotopic methods. A case study from the Matanza-Riachuelo River basin, Argentina

The groundwater contamination by hexavalent chromium (Cr(VI)) in a site of the Matanza-Riachuelo River basin (MRB), Argentina, has been evaluated by determining the processes that control the natural mobility and attenuation of Cr(VI) in the presence of high nitrate (NO ) contents. The groundwater Cr(VI) concentrations ranged between 1.9E-5 mM and 0.04 mM, while the NO concentrations ranged between 0.5 mM and 3.9 mM. In order to evaluate the natural attenuation of Cr(VI) and NO in the MRB groundwater, Cr and N isotopes were measured in these contaminants. In addition, laboratory batch experiments were performed to determine the isotope fractionation (ε) during the reduction of Cr(VI) under denitrifying conditions. While the Cr(VI) reduction rate is not affected by the presence of NO , the NO attenuation is slower in the presence of Cr(VI). Nevertheless, no significant differences on ε values were observed when testing the absence or presence of each contaminant. The εCr determined in the batch experiments describe a two- stage trend, in which Stage I is characterized by εCr ~−1.8‰ and Stage II by εCr ~−0.9‰. The respective εN obtained is −23.9‰ whereas εO amount to −25.7‰. Using these ε values and a Rayleigh fractionation model we estimate that an average of 60% of the original Cr(VI) is removed from the groundwater of the contaminated site. Moreover, the average degree of NO attenuation by denitrification is found to be about 20%. This study provides valuable information about the dynamics of a complex system that can serve as a basis for efficient management of contaminated groundwater in the most populated and industrialized basin of Argentina.This research was supported by the Instituto de Hidrología de Llanura “Dr. Eduardo J. Usunoff” (IHLLA) and by IDAEA-CSIC as part of the programme EMHE “Enhancing Mobility between Latin-American and Caribbean countries and Europe”. We thank the IHLLA technic staff for their assistance in water sampling and Ms. M. F. Altolaguirre, B.S., and Ms. O. Floriani, B.S., for assisting in the logistics of manipulation and conservation of samples. This research is also supported by the project PACE-ISOTEC (CGL2017-87216-C4-1-R), financed by the Spanish Government and AEI/FEDER from the UE, and the project MAG (2017 SGR 1733) from the Catalan Government. We also thank the Centres Científics i Tecnològics of the Universitat de Barcelona for its analytical support