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The formation of 4-nitroso-sulfamethoxazole and 4-nitro-SMX, two transformation products (TPs) of sulfamethoxazole (SMX) was investigated under batch soil slurry experiments and in a field study. Due to their low occurrence levels (ng/L) in environmental waters, a suitable analytical method based on liquid chromatography – high resolution – mass spectrometry was developed. Consequently, field observations revealed, for the first time, the occurrence of 4-nitroso-SMX in groundwater at concentrations as high as 18 ng/L.Nitric oxide (NO ) steady-state concentrations were determined in soil slurry experiments because this reactive specie accounted for the formation of 4-nitroso-SMX and 4-nitro-SMX. Measurements revealed that environmental SMX concentrations (0.2–2 μg/L) at neutral pH induced the accumulation of nitric oxide. Under acidic conditions (pH < 6), nitrous acid (HONO) was the major source of nitric oxide while under neutral/basic conditions nitric oxide release was related to the inhibition of denitrification processes. Under laboratory experiments, SMX nitration reaction appeared to be an irreversible transformation pathway, while 4-nitroso-SMX was slowly transformed over time. The occurrence of 4-nitroso-SMX conditions was therefore unexpected in the field study but could be due to its continuous input from soil and/or its relative persistence under anoxic conditions. A mechanism for 4-nitroso-SMX formation was proposed involving a nitrosative desamination pathway through a phenyl radical. [ABSTRACT FROM AUTHOR]

Up till now, the diclofenac (DCF) transformation into its nitrogen-derivatives, N -nitroso-DCF (NO-DCF) and 5-nitro-DCF (NO 2 -DCF), has been mainly investigated in wastewater treatment plant under nitrification or denitrification processes. This work reports, for the first time, an additional DCF microbial mediated nitrosation pathway of DCF in soil under strictly anoxic conditions probably involving codenitrification processes and fungal activities. This transformation pathway was investigated by using field observations data at a soil aquifer system (Katari watershed, Bolivia) and by carrying out soil slurry batch experiments. It was also observed for diphenylamine (DPA). Field measurements revealed the occurrence of NO-DCF, NO 2 -DCF and NO-DPA in groundwater samples at concentration levels in the 6–68 s/L range. These concentration levels are more significant than those previously reported in wastewater treatment plant effluents taking into account dilution processes in soil. Interestingly, the p -benzoquinone imine of 5-OH-DCF was also found to be rather stable in surface water. In laboratory batch experiments under strictly anoxic conditions, the transformation of DCF and DPA into their corresponding N -nitroso derivatives was well correlated to denitrification processes. It was also observed that NO-DCF evolved into NO 2 -DCF while NO-DPA was stable. In vitro experiments showed that the Fisher-Hepp rearrangement could not account for NO 2 -DCF formation. One possible mechanism might be that NO-DCF underwent spontaneous NO loss to give the resulting intermediates diphenylaminyl radical or nitrenium cation which might evolve into NO 2 -DCF in presence of NO 2 radical or nitrite ion, respectively. [ABSTRACT FROM AUTHOR]

Contamination of groundwater by nitrate is a worldwide environmental issue. A better knowledge of nitrate sorption characteristics by soils contributes to efficient fertilizer use and prevents aquifer contamination. In volcanic soils, nitrate sorption is induced by variable charges due to the presence of amorphous materials and aluminum (Al) and iron (Fe) oxides. Anion transport in packed and intact columns was investigated in a Mexican Allophanic Andisol, under different permanent flow regimes in unsaturated conditions and several NO3-‐N and Br- input concentrations. In the packed columns, the NO3-‐N adsorption in the soil was nonlinear. In the intact columns, the retardation coefficient variation was directly correlated to the increase of amorphous material with depth. The presence of preferential flow in the intact columns significantly increased the mobility and velocity of nitrate moving through the columns, whereas in the packed columns, NO3-‐N fate was only affected by soil chemical composition and mineralogy. [ABSTRACT FROM AUTHOR]

Allophanic top‐ and subsoils from the Mexican and Newzealand Central Volcanic Plateau, as well as a nonallophanic sandy loam soil, were sampled to study the impact of organic matter and allophane content on 2,4‐D fate. High sorption rates were found, especially in the two topsoils from Mexico and New Zealand, with distribution coefficient (Kd) obtained from displacement experiments in packed columns equal to 7.61 and 8.43 L kg-1 respectively. 2,4‐Dichlorophenoxyacetic acid transfer through the soil columns was found to be in chemical nonequilibrium and was well predicted using a two‐site sorption model. For the two allophanic top soils, Kd obtained from batch was very different to the Kd obtained from column experiments. Either the equilibrium could not be reached in batch or the two‐site model was not able to describe the wide range of sorption sites present in the highly reactive organic matter and allophane components. [ABSTRACT FROM AUTHOR]

Predictions of natural attenuation of volatile organic compounds (VOCs) in the unsaturated zone rely critically on information about microbial biodegradation kinetics. This study aims at determining kinetic rate laws for the aerobic biodegradation of a mixture of 12 volatile petroleum hydrocarbons and methyl tert-butyl ether (MTBE) in unsaturated alluvial sand. Laboratory column and batch experiments were performed at room temperature under aerobic conditions, and a reactive transport model for VOC vapors in soil gas coupled to Monod-type degradation kinetics was used for data interpretation. In the column experiment, an acclimatization of 23 days took place before steady-state diffusive vapor transport through the horizontal column was achieved. Monod kinetic parameters Ks and vmax could be derived from the concentration profiles of toluene, m-xylene, n-octane, and n-hexane, because substrate saturation was approached with these compounds under the experimental conditions. The removal of cyclic alkanes, isooctane, and 1,2,4-trimethylbenzene followed first-order kinetics over the whole concentration range applied. MTBE, n-pentane, and chlorofluorocarbons (CFCs) were not visibly degraded. Batch experiments suggested first-order disappearance rate laws for all VOCs except n-octane, which decreased following zero-order kinetics in live batch experiments. For many compounds including MTBE, disappearance rates in abiotic batch experiments were as high as in live batches indicating sorption. It was concluded that the column approach is preferable for determining biodegradation rate parameters to be used in risk assessment models. [Copyright &y& Elsevier]

Watercress (Lepidium sativum) is consumed as a vegetable, especially by the indigenous community in New Zealand. An investigation was carried out on the accumulation of arsenic by watercress, following earlier reports of inordinate arsenic concentrations in some aquatic macrophytes collected from the Waikato River, North Island, New Zealand. The Waikato River and some other aquatic systems in Taupo Volcanic Zone, New Zealand have elevated arsenic concentrations due to geothermal activity. Watercress, river water and sediment samples were collected from 27 sites along the Waikato river and analysed for arsenic. Greenhouse trials with watercress grown in beakers containing added arsenic were conducted to confirm the ability of this species to accumulate arsenic. At a number of sites, the concentration of arsenic in both the water and the watercress samples exceeded the World Health Organisation (WHO) limit for drinking water (0.01 mg l−1) and foodstuffs (2 mg kg−1 on a fresh weight basis). The average leaf and stem arsenic concentrations were, respectively, 29.0 and 15.9 mg kg−1 on a fresh weight basis. Plants grown in solutions of >0.4 mg l−1 arsenic concentration had fresh weight arsenic concentrations above the WHO limit. Despite these higher concentrations, arsenic levels in plants grown under greenhouse conditions were approximately fivefold lower than in plants growing in the Waikato River, possibly because under natural conditions, the watercress is rooted in sediment containing on average approximately 35 mg kg−1 arsenic. It is recommended that watercress from the Waikato River, or other areas with elevated water arsenic concentrations, should not be consumed. [Copyright &y& Elsevier]

• Wetness-adaptive StorAge Selection functions applied to Mediterranean climate. • Young water is discharged preferentially. • Young water preference is strongly increased under wet conditions. • Up to 63% of stream water is younger than one day during floods. • Elevated risk of contaminant transfer from diffuse sources under these conditions. Not just the quantities but also the transit times are of crucial importance for understanding the transfer of water through a catchment. This information is essential, for example, for determining the risk of the transfer of contaminants from diffuse, agricultural sources toward surface water bodies. We created a hydrological age-tracking reservoir model of a meso -scale Mediterranean catchment that is prone to flash floods. We implemented StorAge Selection (SAS) functions that adapt to the catchment's wetness condition in order to represent changing flow processes. The goal is to evaluate the evolution of transit time distributions (TTDs) through the catchment (1 h time step, 1 h resolution), providing an example for a rural catchment under a Mediterranean climate. The focus is on flood events, and the results are interpreted with regard to the risk of contaminant transfer from diffuse sources. The dependence of water age preferences on catchment wetness is examined. We propose and test a multi-tracer approach to parametrize SAS functions on multiple reservoirs. The model was calibrated and validated against the streamflow discharge (Q), deuterium isotope signature ( δ 2 H) and dissolved silica concentration (S i) at the outlet. While δ 2 H acted as a direct tracer of rain-water, S i was used as a tracer of the contact time with the soil and rock minerals. The model revealed high event water fractions during flood events (with up to 63 % of water younger than one day) and a dominance of water older than one year most of the remaining time. This suggests an elevated risk of the transfer of agricultural contaminants toward streams during flood events. The results also indicate an inverse storage effect (ISE), with young water preferences increasing under wet conditions. [ABSTRACT FROM AUTHOR]

A hydrogeochemical and stable isotopic ( δ 15 N NO 3 and δ 18 O NO 3 ) multitracer approach was combined with previous geological and hydrogeological knowledge in a groundwater-dominated basin, located within the semiarid region of the Bolivian Altiplano (SE of Lake Titicaca). Major natural processes and anthropogenic impacts controlling water chemistry and isotopic compositions of groundwater were identified and corresponding aquifer impacted zones determined. The main natural processes are, by following water flowlines, (1) silicate weathering in the piedmont subsystem (~4,600–3,910 m asl, Ca(Mg)-HCO3 facies), (2) Na-Ca exchange within glacial-fluvial deposits overlying paleolacustrine deposits (~3,910 to 3,860 m asl, Na-HCO3 facies), and (3) evaporite dissolution in the confined zone of the lacustrine plain (~3,860–3,810 m asl, Na-Cl-SO4 facies). The highest contributions of anthropogenic nitrate in groundwater have been observed at 3,960–3,860 m asl in the piedmont subsystem and were isotopically associated with leaching from areas influenced by manure piles, synthetic N fertilizers, and sewage collector pipes. In this subsystem, natural water–rock interactions could be deciphered with minimal anthropogenic impact, allowing nitrate sources to be clearly identified. Denitrification, occurring in the topographic lows of the piedmont subsystem, was identified as the main natural attenuation process. The multitracer approach provided a consistent understanding of the major processes that take place along the groundwater flow system and confirmed the significant role of anthropogenic nitrate. This aquifer system thus represents an ideal model of the region's hydrochemical evolution along the gravity-driven flow caused by natural water–rock interaction processes and the influence of anthropogenic contamination. [ABSTRACT FROM AUTHOR]

We presented an innovative hydrogeophysical approach that allows numerical modeling of water flow in a variably saturated media. In our model, we approximated the subsurface by horizontally stratified porous media. The model output was a time varying water content profile. Then, we compared the water content provided by the model with the water content measurements carried out using the time-lapse Magnetic Resonance Sounding (MRS) method. Each MRS sounding provided a water content profile in the unsaturated zone down to twenty meters. The time shift between the profiles corresponded to the time lapse between individual MRS soundings. We minimized the discrepancy between the observed and the modeled MRS signals by varying hydraulic parameters of soil layers in the water flow model. For measuring and processing MRS data, we used NUMIS MRS instrument and SAMOVAR software. We carried out water flow modeling with HYDRUS-1D software. This paper reports our results and summarizes the limitations of the MRS method applied to water content measurements in the unsaturated zone. • We use an innovative approach for integrating geophysical data in groundwater modeling • We show the possibility of time-lapse MRS monitoring of the water content in the unsaturated zone • MRS time-lapse measurements combined with water flow modeling provide more information than when applied separately • We use existing hardware and software that renders our method ready available [ABSTRACT FROM AUTHOR]

The increasing demand for water and irrigation in the semi-arid Bolivian Altiplano requires a better knowledge of the available resources, particularly groundwater. The aim of this study is to provide a first insight into the hydrogeological structure (0–200 m deep) and groundwater dynamics of the Katari-Lago Menor Basin aquifer located between the Eastern Cordillera and Lake Titicaca, Bolivia. This aquifer is studied using geophysical data (a total of 187 Time Domain Electromagnetic (TDEM) soundings), piezometric data (97 groundwater level measurements) and geochemical data (52 groundwater samples), combined with geological, lithological and topographical information. The results allowed identifying stratigraphic models consistent with the Quaternary sediments being hydraulically connected and behaving as a single regional basin-aquifer. This basin-aquifer is delimited by the most ancient lake invasions towards the southern, western and northern sides and by the lower limit of rock glaciers towards the eastern side. A large portion of the aquifer presents an unconfined behaviour varying from 50 to 150 m while the confined portion varies from 100 to 150 m. Groundwater flow within the Katari and Lago Menor Basin aquifer is composed of several interconnected groundwater flow systems. The main groundwater flow system starts in the high mountain ranges of the Eastern Cordillera, follows the topographic Piedmont gradient (NE to SW) and discharges in a series of wetlands. This multidisciplinary approach proved to be an appropriate method to derive a consistent picture of the hydrogeological functioning of the Katari-Lago Menor Basin aquifer. • Performance of a groundwater basin-scale multidisciplinary study. • TDEM surveys were efficient to investigate the structure of a basin-scale aquifer. • Continuity of Quaternary layers behaving hydraulically as a single aquifer. • 3D schematic structure and dynamics of a major aquifer in the Bolivian Altiplano. • Basis for the development of a 3D numerical groundwater model. [ABSTRACT FROM AUTHOR]

Latin America, like other areas in the world, is faced with the problem of high arsenic (As) background in surface and groundwater, with impacts on human health. We studied As biogeochemical cycling by periphyton in Lake Titicaca and the mine-impacted Lake Uru Uru. As concentration was measured in water, sediment, totora plants (Schoenoplectus californicus) and periphyton growing on stems, and As speciation was determined by X-ray absorption spectroscopy in bulk and EDTA-extracted periphyton. Dissolved arsenic was between 5.0 and 15 μg L−1 in Lake Titicaca and reached 78.5 μg L−1 in Lake Uru Uru. As accumulation in periphyton was highly variable. We report the highest As bioaccumulation factors ever measured (BAFsperiphyton up to 245,000) in one zone of Lake Titicaca, with As present as As(V) and monomethyl-As (MMA(V)). Non-accumulating periphyton found in the other sites presented BAFsperiphyton between 1281 and 11,962, with As present as As(III), As(V) and arsenosugars. DNA analysis evidenced several taxa possibly related to this phenomenon. Further screening of bacterial and algal isolates would be necessary to identify the organism(s) responsible for As hyperaccumulation. Impacts on the ecosystem and human health appear limited, but such organisms or consortia would be of great interest for the treatment of As contaminated water. [ABSTRACT FROM AUTHOR]

The widespread presence of pharmaceutical products (PP) in terrestrial water reservoirs (surface water, groundwater, soil water) is at present established. The two main sources are urban discharges and agricultural inputs. While urban discharges are point sources that enter rivers mainly via waste water treatment plants (WWTP), agricultural inputs can be point sources (e.g. leaching from manure storage) but are mostly diffuse (animals kept outside, application of manure). Many studies have investigated the input of PP through WWTP. However, the diffuse input through livestock farming is much less understood. The spatial distribution of PP input, the soils reactivity with those molecules and the dominating hydrological processes are key factors to better understand the PP transfer and fate on a plot- to catchment-scale. The overall goal of the ongoing PhD thesis is the establishment of a catchment-scale conceptual model for the prediction of the fate of PP and the closure of a catchment PP mass balance.The Claduègne catchment (42 km²) is an agricultural Mediterranean catchment part of the OHMC observatory and the OZCAR research infrastructure. The basin is instrumented for hydrological monitoring on a high temporal frequency of river water and suspended sediment and a study on the dominant hydrological processes has been conducted. Interviews with livestock breeders have been conducted in the catchment to identify the PP applied by farmers, estimate the quantities and determine the surfaces where the cattle are kept. This allowed a spatially and temporally distributed quantification of the sources of some PP.The interviews revealed that the veterinary PP (VPP) primarily used in the catchment do not correspond to the molecules that are most frequently analysed in natural waterways. This highlights the need to adapt the monitoring and analysis methods in order to be able to understand the fate of PP within agricultural watersheds.Analysis methods for the primarily used VPP in that watershed will be tested and evaluated to be able to follow the outflow of these PP in the watershed during base flow and floods. A literature review of sorption studies of PP in different soil types has been conducted and will be complemented with laboratory experiments in order to identify the most important soil properties for predicting different PP retention and mobility coefficients. Soil sampling campaigns are targeted in order to obtain the spatial distribution of those soil properties. Field experiments will be conducted, to determine the dominant PP flow pathways at the hillslope scale and close the scale-gap between laboratory batch experiments and the catchment-scale. [ABSTRACT FROM AUTHOR]

Emerging contaminants have become ubiquitous in soils and surface waters. They include in particular pharmaceuticals (PPs) such as analgesics, antibiotics, antihistamines, hormones..., among a wide range of other products (personal care products, plasticizers, flame retardants, manufactured nanoparticles...). Although the fate of PPs in urban context has been quite well documented in relation with the domination of point-sources in these zones, the dissemination of PPs in rural zones remains poorly understood mostly because of the complexity and variety of PPs sources (animal breeding, application or storage of manure or waste water sludge, organic amendments...) and their temporal occurrence, in parallel with more common sources (e.g. waste water from treatment plants, WWTP...). The spatial distribution of PP input on one hand and soils reactivity to those molecules on the other hand are key factors that need to be better understood in order to improve the prediction of their transfer and fate at the catchment scale.The objective of this study, conducted in the frame of a multidisciplinary project, was to produce vulnerability risk maps of an agricultural Mediterranean basin: the Claduègne river basin of 42 km², which is part of the OHMCV observatory, the French OZCAR research infrastructure, and the Zone Atelier Bassin Rhône (ZABR). A combined approach was conducted to produce these maps: 1/ survey of veterinaries and farmers to identify and semi-quantify the main PPs used yearly in the basin and the pasture parcels surface area, 2/ field campaigns for both soil and water properties characterization and for pharmaceutical screening (passive and point measurements) in surface waters, 3/ Literature review and laboratory experiments on PPs retention and degradation to establish mobility and persistence maps of PPs. This will allow establishing a spatially and temporally distributed quantification of the sources of 9 PPs, among which Sulfamethoxazole (antibiotic) and Ivermectin (insecticide), regularly used in the catchment. Along with these results on the potential input mass of PPs per surface, we will also produce PPs mobility and persistence maps by spatializing these properties at the catchment scale using pedotransfer functions. These maps will be combined using a GIS to produce vulnerability maps, which will be compared to the results of the PPs screening in surface waters. This ongoing work already permitted to evaluate the leaching potential (vulnerability maps) for two molecules using the groundwater ubiquity score (GUS), which accounts for the retention (solid – liquid distribution coefficient, Kd) and persistence (chemical half-life, T1/2) of PPs. [ABSTRACT FROM AUTHOR]