Thèses sur le sujet « Chemistry of waters »

14 MeV neutron activation analysis, based on the 82Se(n,2n) Se81m nuclear reaction, has been investigated for the measurement of selenium in environmental waters. The levels of the selenium present in environmental waters and the relatively high limit of detection achievable with fast neutron activation analysis resulted in the need to develop a concentration procedure for the extraction of selenium from large volumes of environmental water before neutron activation.

Phosphorus (P) has long been acknowledged as a vital nutrient for living organisms and is a key factor responsible for the fresh water eutrophication. Our understanding of the phosphorus cycle has been limited by: (1) the common assumption that all P in the environment occurs primarily as phosphates and (2) by the limited analytical methods available to identify P speciation. In an attempt to understand the distribution and chemistry of phosphorus within a freshwater system we must be able to identify individual P species. To this end, we used a coupled High Performance Liquid Chromatograph (HPLC) - Inductively Coupled Plasma Mass Spectrometer (ICPMS) to determine concentrations of orthophosphate (+5), phosphite (+3) and hypophosphite (+1) in aqueous samples using methods modified from IC techniques developed by Ivey & Foster (2005) and Pech, et al. (2009) and Atlas et al. (in prep). The identification of different P species provides insight pertaining to contamination, bioavailability and sustainability within a freshwater system. Thirty-two individual water samples were collected from six different bodies of freshwater in the Tampa Bay area between the months of November 2012 to March 2013. The freshwater samples collected were from river and pond/swamp water locations. Two sampling sites were chosen at each location. At each site, one sample was collected from the water's surface and a second sample was collected from the sediment pore water. When depth was sufficient a third sample was obtained from the midpoint between the surface and sediment. Analytical results show that redox reactions of P occur in all freshwater samples collected as identified by HPLC-ICP-MS analysis. Our data show that the distribution and concentration of reduced P is controlled primarily by pH, and secondarily by water circulation, ORP and sediment type. Our results also imply biologic influence as a potential primary control of reduced P flux. Additional samples must be collected in order to quantify and differentiate the processes controlling P speciation. The ability to identify P speciation raises many questions concerning the validity of current methods used to measure P; other forms of reduced P may be present. Additional sample analysis will be necessary to determine how and if reduced forms of P affect the P cycle.

An automated voltammetric dissolved trace metal monitor was developed and validated for in situ analysis of estuarine waters. The system was successfully applied to the determination of Ni concentrations during two studies in the Tamar Estuary. The automated system used Adsorptive Cathodic Stripping Voltammetry (AdCSV) for trace metal analysis with a continuous flow sampling procedure and an on line LTV digestion system to ensure complete breakdown of interfering and metal complexing organic ligands. Its application to the measurement of total dissolved Ni in the Tamar Estuary showed a high measuring frequency of up to 6 fully calibrated samples per hour and trace metal concentrations ranged between Ni --10 nM to -50 nM with a salinity gradient of between -0 to -25. A procedure was developed to evaluate suspended particulate material (SPM) trace metal extraction efficiencies of using EDTA extraction solutions followed by analysis of metals using Inductively Coupled Plasma Mass Spectrometry. The use of EDTA allowed the determination of the easily exchangeable particulate metal fraction using well defined constraints with respect to the competition between EDTA and the particles. Optimum particle extraction time was 72 hours, using 0.05 M EDTA concentration and extractant : particle ratio of 200:1, The extraction procedure was applied to the study of particulate Zn, Ni, Cu, Mn and Mg composition of SPM collected from the Scheldt Estuary. In addition, seasonal investigation of dissolved chemical speciation of Cu, Co, Ni and Zn in the Tamar estuary using AdCSV was undertaken. The results showed contrasting behaviour for these metals with a high seasonal variability of Zn and Co and a low seasonal variability for Cu and Ni. The low concentration of Zn and Co during summer months suggested that low river flow rates, low rainfall caused minimal sediment disturbance thereby reducing the contribution of Co and Zn enrich pore waters to the estuary. Furthermore, it was suggested that uptake of Zn and Cu by phytoplankton could have contributed to the lower concentrations of these elements during the summer survey. The electrochemically non labile fraction of dissolved Cu, Zn, Ni and Co exhibited highest values at high salinities and indicates the importance of organic complexation of these metals in the lower estuary. Furthermore, during the spring surveys elevated fractions of organically complexed Cu, Zn, and Ni were observed and it was suggested that seasonally enhanced levels of primary productivity could have lead to the complexation of these elements by algal exudates and break down products. 0.05 M EDTA extraction protocol was applied to the study of dissolved and particulate Zn, Cu, Co and Ni in the Scheldt estuary. Dissolved Co and Ni exhibited elevated concentrations in the upper estuary, which were related to anthropogenic discharges into the estuary. Its was possible to identify a relationship between particulate organic carbon and particulate Zn, Cu and Ni, which suggested that complexation of these elements by organic particulate material was an important factor in their dissolved/particulate partitioning. Results of dissolved Cu natural complexing ligand titration experiments showed similar behaviour for CUL and K^^^ for the Tamar and Scheldt estuaries with high values at low salinity decreasing to low values at high salinity. The Scheldt generally exhibited higher values for K^^,^ and CUL concentrations ( / ^CU^ -15.7; CUL -200 Cu neq 1"*; S = 1) than the Tamar estuary (/C^^^ 14.0; CUL -170 Cu neq 1"'; S = 0). It was suggested that anthropogenic inputs of nutrients in the Scheldt lead to enhanced levels of phytoplankton activity and complexation of Cu by algal exudates and break down products compared with the Tamar. Total dissolved Ni and Co was undertaken on samples collected from the Atlantic Ocean using detection by AdCSV. The results indicated that Ni and Co exhibited contrasting behaviour in the oceanic waters compared with estuarine waters. The distribution of Co showed low concentrations (mean Co -40 pM) in the Atlantic Ocean and elevated concentration associated with aeolian particulate inputs off the Northwest coast of Africa. In contrast, Ni was relatively homogeneously distributed over large parts of the Atlantic (2.4 ± 0.7 nM). However, both Ni and Co exhibited conservative behaviour during mixing between the Brazilian Current with the Ni and Co enriched Falklands Current indicating the importance of physical water transport on trace metal distribution in oceanic systems.

Tributyltin (TBT) is a pollutant, mainly introduced to the environment as a marine anti-fouling agent. The aim of this work was to assess and develop sustainable and cost-effective remediation technologies for TBT-contaminated dredged materials. For this purpose, analytical methods were developed for sediments and sediment leachates. For the sediments, a triple extraction followed by derivatisation and measurement by gas chromatography with pulsed flame photometric detection was employed, avoiding the lengthy concentration step of the organic layer. The TBT detection limit of ca 0.04 mg Sn/kg in sediment was below the suggested limit of 0.1 mg/kg for sea disposal of TBT-contaminated dredgings (OSPAR Commission). For the leachates, derivatisation and extraction into hexane was used. Also, a new procedure, with the potential for automation, was developed for the simultaneous analysis of multiple water samples, based on in situ extraction and derivatisation on C18 solid phase extraction cartridges. No legislative limits existed for TBT in leachates, therefore the detection limits of ca 6-10 ng Sn/L achieved were regarded satisfactory, as they were below or similar to the EQS for coastal and estuarine waters or freshwaters (2-20 ng/L TBT). A pilot investigation was carried out on a dockyard to evaluate the use of X-Ray fluorescence as a screening method for the presence of TBT in sediments. Due to tin contamination such a technique was not suitable for the site examined. Incineration was found to remove TBT but it would incur very high costs. Ultrasonic destruction was not effective enough, even on TBT-spiked water solutions. Carbon products, pure clays, organically modified clays, zero valent iron, fly ash and cements were screened for their abilities to prevent TBT leaching, using a leaching test. The best performer was a powdered activated carbon product which, even mixed with cement that increases the leaching of TBT, delivered a TBT-free (< 5 ng Sn/L) leaching test result 33 days after the mixing. The result showed that this technique could provide a solution for the immobilisation of TBT in contaminated dredgings by mixing this relatively low-cost, multi-purpose and inert additive, with or without cement according to the site specific requirements.

The components of natural water can be divided into three categories: dissolved, colloidal and particulate phases. The colloids are small particles with at least one dimension between 1.0 nm and 1.0 m (IUPAC); they do not sediment when suspended in “solution”. The small size of colloidal particles causes this fraction to have a large surface area with potential to bind significant amounts of trace metals and organic pollutants and also allows colloids to migrate over long distances potentially increasing the spread of the contaminants. To better understand the behaviour of colloidal matter in natural waters, engineered spherical silica colloids of known size were made and chemically labelled so that the colloids can be sensitively tracked through the fractionation process of analytical filtration. The labels used to date have included the toxic metalloid arsenic and the fluorescent compound Rhodamine B, which had also been used to improve sensitivity. The behaviour of engineered labelled colloidal sols has been investigated during the preliminary filtration study in the laboratory. Artificial colloidal sols of the silicas in water were investigated to see how their filtration, employing a sequential filtration of a water sample through 1.6 (or 8 m) and 0.1 m cut-off filters, influenced a measurement of arsenic. The content of the filters after filtration were investigated by scanning electron microscopy and analysed for arsenic using atomic absorption spectroscopy. Ca. 50% and 65% of the silica particles were found on the large pore filters (1.6 um and 8.0 um filter), providing evidence of the aggregation and clogging effects on the fibre filter. The analysis of the Tamar estuary water samples revealed substantial amounts of arsenic, attributed to drainage from mining activities. Colloidal arsenic was found along with dissolved and particulate arsenic in freshwater. However, the saline water samples showed the arsenic content to be distributed mainly in the particulate and dissolved fractions. A suggested explanation of this phenomenon is that aggregation of colloids took place in the presence of saline water and therefore most of the colloidal arsenic was collected with the particulate fraction. Finally, a study of Southampton Water and Dart waters was performed by adding engineered colloidal particles to explore the aggregation of colloids in water of different salinity. Unfortunately, experimental problems prevented a definite verification of the influence of salinity in this case

Oceanic barium has many potential proxy applications, from the quantification of export productivity using sedimentary barite, to the tracing of freshwater inputs or the circulation of deep water masses. Using these proxies to reconstruct past oceanic conditions is of particular importance in the Southern Ocean, where the ventilation of deep water masses and the biological drawdown of CO2 are thought to play a significant role in climate regulation. However, the distribution of particulate and dissolved barium in this region is not solely controlled large scale water mass circulation and predictable biological associations, but by an additional combination of spatially and temporally variable local and coastal processes. In this thesis I have found that stronger near-surface gradients are observed in Antarctic waters than in other ocean basins, with a significant association between Bad and silicic acid in surface waters at the WAP. As no direct link was observed between Bad and biological productivity, these observations can be explained by an association between Bad and siliceous detrital material, either by adsorption mechanisms or through barite precipitation in surface waters. Greater levels of Bad release and inferred barite precipitation production are observed from the decay of diatom-dominated detrital material. The accumulation of particulate barium phases in WAP shelf sediments appears to produce a benthic Bad flux that acts as a significant source of Bad to coastal waters. Sea ice is found to be a further, little studied, control on Antarctic coastal Bad distributions, with non-conservative distributions of Bad observed in sea ice cores that may be due to abiotic barite precipitation, and large fluxes of sea ice melt associated with unusually low surface Bad concentrations.

The aim of this thesis was to improve our understanding of the natural iron fertilisation processes that can alleviate the High Nutrient Low Chlorophyll conditions normally associated with the Southern Ocean. The annual phytoplankton bloom occurring north of the Crozet Plateau (46°26’S - 52°18’E) provided a good opportunity to study these phenomena during CROZEX, a multidisciplinary study performed in austral summers 2004/2005 and 2005/2006. Particular emphasis has been placed on the sources of Fe to the upper water column, and on the different processes that drive the distribution of iron, such as mixing with deeper waters, advection of Fe rich waters from the islands, or particles and atmospheric inputs. A flow-injection analyser with DPD catalytic spectrophotometric detection (FIA-DPD) was first set up for the determination of total dissolved Fe (DFe, ≤ 0.2 µm) and careful assessment of data demonstrated the high quality of the information obtained in this study. Analytical measurements of DFe were performed in twenty vertical profiles from the North to the South of the islands that show evidence of a range of processes influencing the iron distributions. Most significantly, an enrichment of DFe (>1 nM) has been identified at close proximity to the islands, which suggests that the plateau and the associated sediments are a source of iron. Waters further north also appear to be affected by this input of both coastal and shelf origin, although dissolved iron concentrations decrease as a function of distance to the north of the plateau with a gradient of 0.07 nM.km-1 as a result of dispersion and mixing. This gradient was then combined with short-lived Radium isotopes profiles, allowing the determination of a horizontal advective flux of Fe. Estimates of atmosphere and vertical fluxes of Fe to surface waters were also calculated. It was then possible to estimate a pre-bloom concentration of ~ 0.44 nM, which is sufficient to drive the inferred level of the new production in the bloom area. Labile iron has been distinguished from the refractory fraction of iron in the suspended particulate matter exported from the mixed layer by developing a two-stage leaching technique. The resulting solutions were analyzed using ICP-MS. By using associated 234Th fluxes, vertical fluxes of particulate iron in both phases were determined as well as their residence times. Data clearly show that carbon export was linked to the iron residence time and enhanced in the northern region where iron inputs occur. This thesis therefore provides a comprehensive data set of DFe and particulate iron in waters surrounding the Crozet Islands. It also presents the first attempt to establish an iron budget that can be developed into a model and provides a good reference point for subsequent studies of natural iron fertilization processes that occur around these islands.

There is a demand for portable in-situ measurement systems for measuring ions in environmental water samples. Commercially available flow injection analysis systems are not easy to install, have high power requirements, and use large volumes of reagents. Miniaturising the measurements is promising, and quite successful microfluidic automated systems have been developed. These systems, however, tend to only measure one species at a time, and what is really required is a portable system that simultaneously measures several anions and cations. The aim of this thesis was, therefore, to develop a novel analytical device that has the ability to measure several nutrient levels in water samples in-situ, at high-frequency measurements, by miniaturising the sample preparation and measurement. The system involved: ion extraction, ion separation, and detection with a C4D contactless conductivity detector. This analytical system to be developed needs to be able to replace the current, typical system being used in the field. To avoid the effects of the sample matrix on the separation process, the extraction of ions from the sample before separation, was investigated. Different ion extraction approaches were explored, including ion extraction through a potassium silicate monolith and electrodialysis. The potassium silicate monolith was used to extract ions from water samples; this worked as a barrier to prevent unwanted materials present in the river water from entering the measurement system. The presence of these materials would influence the separation process. Extraction techniques using the potassium silicate monolith were investigated, using both glass chips and glass capillaries. To prevent the electroosmotic flow (EOF) caused by the negative charge on the surface of the glass and the monolith, the surface was silanised. Three different silanisation methods were investigated: trichloro perfluorooctyl silane (FDTS), a commercial coating, and an end-capping procedure. The extraction of the ions was achieved with all three of the silanisation methods but greater reproducibility was needed. Electrodialysis (ED) was examined to see if it could provide a more reproducible sample introduction method. The advantage of this method was that it could be effectively combined with electrophoresis (CE) for rapid pre-concentration and the subsequent determination of inorganic ions in the river water. Different ED techniques were investigated for extracting the inorganic ions. This involved exploring different membranes including polytetrafluoroethylene (PTFE), Parafilm, cellulose acetate, and ion-exchange membranes. Different ED systems were evaluated, including a commercial flow design and microfluidic chips manufactured from cyclic olefin copolymers (COC), with both single and multiple membranes. The cellulose acetate membrane provided good results for cation extraction from a real river water sample. Sodium, calcium, potassium and magnesium were extracted at 85%, 45%, 23%, and 10%, respectively. The anion-exchange (AEX) membrane in the ED system was successful and demonstrated good results. Cation extraction with a single cation-exchange (CEX) membrane also provided good results. Several ED microfluidic chips were designed to improve the extraction, using the ion-exchange membranes. In this system, a gold electrode was used and positive results were obtained for both anions and cations, and the anion extraction was demonstrated using a real river water sample. Five anions were extracted: respectively comprised sulphate 65%, phosphate with 31%, 82% for chloride, nitrite with 10% and nitrate with 6%. Initial work on the separation of the inorganic ions concentrated on a monolithic column, as reported in the literature. For the separation of anions, two different anion exchangers were investigated, lysine and DDAB. The monoliths were prepared in-house and were then coated with the anion exchanger. A commercial C18 monolith was used to compare the results obtained from the homemade monolithic column. Problems were encountered with the coated monoliths, especially in terms of high back pressures, and it was decided that capillary electrophoresis (CE) would provide a better separation solution and would more easily integrate with the ED ion extraction. A proposed design of an integrated system was presented including the pumps that are required, the reagents, and the energy use. The proposed integrated system only required one buffer for all processes in the system, which reduces the environmental impact of the chemical reagents. The suitability of the buffer (MES/His) was extensively investigated, and the amount needed for a month was also calculated to be less than 3 L, which is ideal for the system portability. It was also calculated that the required power could be provided by a battery, although the inclusion of solar panels would be advantageous. The proposed integrated system meets most of the requirements of the project, and promising results were obtained. Further optimisation of the design will focus on increasing the robustness of field applications.

Two sampling stations in the Florida Everglades were selected based on the results from US Environmental Protection Agency and Florida International University Mercury Project. In both sites, most of the methylmercury is associated with the truly dissolved organic matter fraction (

Dissolution rates of hornblende and tremolite were studied in constant pH batch experiments over the pH range 4-6, in order to understand the acid neutralizing role of hornblende in watersheds with low alkalinity. Hornblende and tremolite exhibit linear dissolution kinetics within one or two days after the onset of weathering. During the first 80-100 hours of weathering, base cations are released preferentially to silica in both minerals. During this period a leached surface layer similar in structure to the original material, but altered in composition is believed to be formed. Release rates of Si, Ca, Na, and Mg from hornblende exhibit weak fractional dependence on pH: d[Mg] /dt = k₁[H⁺] 0.13, d[Ca] /dt = k₁[H⁺] 0.065, d[Na] /dt = k₁[H⁺] 0.17, and d[Si] /dt = k₁[H⁺] 0.045. As a result, it is believed that, for large and transient influxes of acidified water, hornblende is not an important pH buffer. Because of rapid dissolution rates, however, hornblende could be an important source of acid neutralizing capacity.

The speciation of trace metals plays a very important role in conditioning their biogeochemical cycles in the marine system. Their species are found to be strongly related to organic matters such as humic acids (HA) and fulvic acids (FA). This thesis aims to develop appropriate techniques to improve our understanding of the speciation of some trace metals, mainly in marine waters. Lead (Pb), cadmium (Cd) and chromium (Cr) which are widely used in industry were analytzed. The concentration of lead in uncontaminated seawater is between 10 and 100 pM, whilst in coastal waters it is higher at up to low nanomolar levels. Little is known about the chemical speciation of lead since it is difficult to be determined at picomolar levels. The work in this dissertation was to develop a suitable electrode and procedure to determine lead in seawater, with the objective that the electrode could be applied for in-situ measurement (without reagents) and for speciation. Several electrodes and materials were tested, including a solid bismuth rod and different microwire materials. Vibration was used to enhance mass transport, instead of solution stirring, to decrease detection limits and facilitate in-situ monitoring. The bismuth electrode was found to be suitable for monitoring lead in coastal waters: it is mercury-free and therefore environmentally friendly, but insufficiently sensitive for oceanic lead concentrations. Comparison of microwires of carbon, gold and silver showed that all of these bare electrodes give a signal for lead, but they suffer variable interference from cadmium, although this is minor if the cadmium concentration is lower than lead. A large improvement was obtained by coating the electrodes with mercury, which gave good peak resolution between cadmium and lead, and good sensitivity. The carbon and gold electrodes had good reproducibility and sensitivity when the mercury was renewed for each measurement. Once coated with mercury, the silver electrode formed amalgam with the silver which could not be completely removed. This electrode was thus not suitable to be used as a renewable mercury film electrode. However, as a permanently amalgamated silver electrode, it was found to have good sensitivity for lead, good separation from cadmium, and was stable for long time usage. This electrode, the silver amalgam microwire (SAM) electrode, was selected for further speciation study of Pb in oceanic waters. Optimum conditions for using the SAM electrode for trace lead detection in seawater involve the use of conditioning potentials. The limit of detection for lead was 4 pM lead in acidified seawater and 12 pM lead in seawater of pH 8. The higher limit of detection at pH 8 is due to the inorganic speciation at that pH. The SAM electrode was successfully used for pseudopolarography of lead to determine its organic complexation. This method was calibrated using model compounds and applied for the first time to estuarine, coastal and oceanic samples at natural concentrations of Pb. It was found that lead occurs mostly as a labile (reactive, organic) species, with a smaller fraction as a strongly organically bound species. The SAM electrode was also tested for chromium analysis using cathodic stripping voltammetry (CSV) in natural waters. Its detection limit is as good as the mercury drop electrode but reduces consumption of mercury.

Thesis (doctoral)--Swedish University of Agricultural Sciences, 2005.
Thesis documentation sheet inserted. Appendix reproduces four papers and manuscripts co-authored with R.K. Johnson. Issued also electronically via World Wide Web in PDF format; online version lacks appendix.

Accurately predicting the fate and mobility of trace metals in natural aqueous systems requires a comprehensive, molecular understanding of metal binding to both the organic and mineral components present in terrestrial and oceanic sediments. This information can then be used to help inform and constrain thermodynamic models for trace metal fate and mobility, and provide an insight into important geochemical processes like trace metal stable isotope fractionation, which may reveal information about past climate. Cu is both a micro-nutrient and common contaminant of freshwater and marine systems, where its reactivity and cycling is dependent on sorption processes to the mineral and organic phases present. Iron (hydr)oxides precipitated in the presence of bacteria are increasingly recognised as a significant proportion of the reactive iron mineral phase in natural systems. Molecular-level EXAFS spectroscopy and macroscopic thermodynamic surface complexation modelling were combined to investigate Cu(II) adsorption to ferrihydrite and Bacillus subtilis (a common freshwater and soil bacterium). At environmentally relevant pH and Cu loading, Cu was found to form an inner-sphere, bidentate, edge-sharing surface complex on ferrihydrite. A stability constant of log K(=FeOH2Cu+ = 8.61 was determined. Cu adsorption to B. subtilis was found to occur via inner-sphere, monodentate surface complexation to carboxyl functional groups present on the bacterial cell walls from pH ~2 to 7. A stability constant of log K=RCOOCu+ = 7.13 was derived. These findings were combined to characterise Cu adsorption to ferrihydrite-B. subtilis composites. Adsorption of Cu to the composites is intermediate to adsorption on ferrihydrite and B. subtilis, and total Cu adsorption appears to be independent of composite mass ratio. EXAFS spectroscopy revealed that Cu adsorbs to both fractions in the composites, forming the same surface complexes as for the isolated end members, and that the distribution of the total adsorbed Cu between the two fractions is dependent on both pH and composite mass ratio. Thermodynamic surface complexation modelling showed that for composites dominated by ferrihydrite, Cu adsorption is approximately additive, unlike composites where B. subtilis dominates, for which surface potential effects were considered the likely cause of non-additivity. This work will ultimately help improve our understanding of metal-mineral-microbe interactions and our ability to predict trace metal fate and mobility. Marine ferromanganese precipitates are found throughout the worlds oceans as hydrogenetic precipitates, diagenetic nodules and hydrothermal deposits, each with Mn mineralogy reflecting its Mn content and growth environment. Being largely composed of Mn and Fe (hydr)oxides, these precipitates are potent adsorbents of oceanic trace metals, including TI, whose stable isotope time-series data in hydrogenetic deposits shows great promise as a tracer of past marine and climatic conditions. Using XAS, the mechanism of TI sorption to Mn and Fe (hydr)oxides was deduced. TI(I) is oxidised to TI(III) during sorption to hexagonal birnessite, but not during sorption to todorokite, triclinic birnessite or ferrihydrite. TI(III) forms an inner-sphere complex at the hexagonal birnessite surface, located at vacant octahedral sites in the phyllomanganate sheets. 205TI enrichment has been observed in hydrogenetic deposits (hexagonal birnessite rich) and furthermore, recent theoretical calculations predict a large equilibrium stable isotope fractionation between TI(I) and TI(III), leading to TI(III) species that are enriched in the heavy 205TI isotope. In light of this work, a molecular sorption-oxidation-fractionation mechanism was proposed to provide the first unifying explanation for the observed geochemical behaviour of TI in marine ferromanganese-rich sediments. This novel mechanism will ultimately help interpret TI signatures in marine sedimentary archives to provide new constraints on past oceanic and climatic change.

Trace metals in natural colloidal material (l-400nm) were investigated in the River Beaulieu, the Trent- Humber system and the Celtic Sea. Colloidal and truly dissolved (<10,000molecular weight) fractions were separated by cross-flow filtration (CFF). Filtration artefacts (conventional and CFF) involving filter blockage and colloid aggregation/disaggregation transformations were minimised through appropriate protocols. 65Zn equilibration experiments were carried out with Beaulieu River colloids (<0A^m). The initial uptake of 65Zn onto colloidal material (10 to 15 %) was very rapid (seconds to minutes) but a large fraction of the tracer remained in the truly dissolved phase. Preliminary modelling to estimate the fraction of colloidal zinc under variable SPM concentrations and Kc sensitivities was completed using different partition coefficients (Kc and Kf) derived during the equilibration experiments. Initial 65Zn-colloid partitioning was related to the mass concentrations (and theoretical surface area) of colloids and colloidal aggregates. The 65Zn radiotracer/colloid association was exchangeable but overall equilibrium partitioning of colloidal/truly dissolved 65Zn did not change with increased total zinc concentration. Loose hydrophobic colloidal aggregates (filaments) with Mn hydroxide coatings formed during sample storage and were capable of removing ~60% of the 65Zn. Field flow fractionation (FFF) of colloidal Beaulieu River water highlighted the significance of the smaller colloidal fractions (<0.08^m and 0.08 to 0.134m) which contained the highest concentration of Fe, Mn and Zn when normalised to an assumed geometric surface area. A spatial and seasonal investigation of colloidal trace metals in the Trent/Humber system identified groups of metals with varying colloidal associations in the order (high to low); Fe> Pb, Mn > Cu, Zn, Ni > Cd. Colloidal Fe, Pb and Mn all illustrated removal in the low salinity region of the estuary. Ni (mainly truly dissolved) showed somewhat conservative behaviour. Total dissolved Cd (and Zn) consistently showed a mid-estuarine maximum (truly dissolved), which was attributed to chloro-complex formation or ionic exchange with major seawater ions. For most metals, the positioning and intensity of the turbidity maximum zone (TMZ) appeared to have greatest control on their removal. Cu is controlled seasonally by input of organic ligands (truly dissolved/microcolloidal). The existence of separate organic and inorganic colloidal pools was proposed, which may have seasonally variable signatures. The presence of lower molecular weight (<10,000Da) colloids is significant for Pb and Cu. Investigations of colloidal Al in the Celtic Sea highlighted problems with colloid disruption within the cross-flow system, and detection of Al colloids using a surface active fluorometric technique. Water column profiles of reactive and dissolved (<0.4/u.m) Al gave insights into processes controlling Al distribution and concentration. Resuspension of Celtic Sea sediment led to an instantaneous release of truly dissolved Al derived from authigenic mineral dissolution. FFF analysis of samples from the resuspension experiments showed that colloidal Al was not a significant fraction (<20% of total dissolved Al). On the basis of these experiments it was possible to estimate that, in the absence of scavenging, the input of truly dissolved Al from typical resuspension events could be sufficient to account for the 5-8nM increase in dissolved Al concentrations observed close to the bed. This research has contributed towards a new approach to interpretation of trace metal speciation and processes in a variety of natural waters. Assessment of the role of colloidal and truly dissolved phases within the 'dissolved' fraction has enabled better understanding of particle/water/metal interactions. The description of trace metal/colloid partitioning and associations within these multicomponent systems has the potential to enhance their modelling in the future.

The aim of this study was to investigate two potential beneficial management practices that will reduce the impact of fecal and fertilizers contamination on the environment. The study was conducted in Eastern Ontario on typical small scale agricultural practices. The first part evaluates the impact of a conventional pasture system and an excluding pasture system on surface water quality. The three year study compared water quality endpoints such as: indicator bacteria, pathogens, parasites and nutrients between treatments. Microbial source tracking indicated that livestock was the main source of fecal contamination in the stream. Greater bacteria and nutrient loads were observed in the unrestricted pasture system than the excluding pasture. Moreover, parasite and indicator bacteria concentrations increased after cattle introduction in both systems. The second part compares nitrogen mass balance between managed and conventional subsurface tile drainage. Over two years, nitrogen loads in groundwater, in tile flow, in plants, in soil and denitrification were compared between treatments. Nitrogen was mostly removed from managed tile drainage fields through plant uptake. Compared to nitrogen plant uptake, denitrification, the second greatest nitrogen removing process was 10 times smaller. The denitrification was greater in the unmanaged tile drainage fields. Generally, managed subsurface tile drainage reduces nitrogen mass loads to surface waters and increases nitrogen uptake by plant, which resulted in greater yields.

The aim with this project was to evaluate Waters AccQTag method which was ananalytical method that Waters Corporation provides for determination of aminoacids. The amino acid analysis was carried out by reversed-phase AQUITY UPLCH-Class, using a BEH C18-column and a PDA detector.Both primary and secondary amino acids were analyzed after precolumnderivatization with the AccQTag reagent kit by a manual procedure and, detected at260 nm. Fresenius Kabis existing products, Aminoven 10 % and Vamin 18EF wereused as samples. The evaluation was based on external calibration curves withprepared standard solutions from Fresenius Kabi, with the addition of the internalstandard L-Norvaline. Waters amino acid standard was used for the system suitabilitytest. A validation according to the ICH guidelines were performed with the followingparameters: specificity, linearity, precision, LOQ, LOD and robustness.Complementary parameters for system suitability test (SST) and stability of standardand reagent were also evaluated. The validation showed that the % RSD values forspecificity, system suitability test and robustness were within the acceptance criteriaof equal or less than 3 % for amino acids. Although the precision were between1.3-7.5 % which was higher than the acceptance criteria of equal or less than 3 %, thiswas likely due to sensitive sample preparation. The linearity was bad which made itimpossible to quantify the method since the calibration curves were below 0.999. Itwas concluded that the system was robust and can be used to analyze amino acids inAminoven 10 % and Vamin 18EF but the preparation step should if possible beautomatized to achieve better precision in the analytical work. Two amino acids,cysteine and histidine, needs to be studied further; cysteine gave three peaks insteadof one and histidine gave a peak split at higher injection volume than 0.5 uL.

Thesis (M.S.) -- University of Maryland, College Park, 2005.
Thesis research directed by: Marine, Estuarine, Environmental Sciences Graduate Program. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

This work represents a first look at the general spatial distribution of trace metals and the inorganic carbon system in the surface waters of Tampa Bay. Tampa Bay's chemical environment bears many influences ranging from hydrological and geological to anthropogenic and meteorological. A large y-shaped estuary on the west-central side of the Florida Peninsula, Tampa Bay extends over 400 square miles and has a 2200 square mile watershed that includes extensive swamps, scrub, agricultural lands and densely urbanized areas. Reaching 37 miles from the northernmost point of Old Tampa Bay to the mouth of the estuary near the Sunshine Skyway Bridge, it is home to the largest port in Florida, and overall places 17th in the nation for tonnage. In addition to its ports, Tampa Bay supports the requirements of a broad range of industries including: ship building and repair, power generation, wastewater processing, development, and recreational and commercial fishing. The region experiences high rainfall during the summer and much reduced rainfall during the remaining portions of the year. The bay has a broad gradient of mixing intensities, with residence times ranging from 100+ days in Old Tampa Bay to less than 20 days at the mouth. Seventy-one percent of Tampa Bay's freshwater input is delivered by four primary rivers: the Hillsborough, Alafia, Manatee and Little Manatee; and the region is strongly influenced by spring outflow from the Floridan Aquifer. The largest river, the Hillsborough, spans 54 miles from the Green Swamp to its mouth in Hillsborough Bay. Samples were collected over a two-week period in January of 2013 along 13 sites on the Hillsborough River and 26 stations in Tampa Bay. Metal concentration analyses were conducted on twelve elements using inductively coupled plasma mass spectrometry (ICP-MS). These twelve elements included sodium, lithium, magnesium, calcium, strontium, barium, vanadium, molybdenum, manganese, nickel, antimony, and uranium. Within Tampa Bay, sodium, lithium, and magnesium exhibited strongly conservative behavior (showing simple two-end-member mixing). Calcium, strontium, molybdenum, and uranium show quasi-conservative behavior, with localized deviations from simple mixing of fresh water and seawater end members. The remaining elements showed variable behavior driven by solubility, redox reactions, and/or unique localized inputs based on local geology. Comparisons of baywater calcium concentrations and the concentrations of lithium, magnesium, strontium and barium revealed simple relationships that are promising for use in interpretations of otolith chemistry of teleosts and some agnatha (Campana, 1999; Carlström, 1963). Samples were collected from both the river and the bay for CO2 system analyses. Spectrophometric pH measurements were obtained using purified m-Cresol Purple (mCP) and the procedures of Liu et al. (2011). Dissolved inorganic carbon (DIC) was processed according to CDIAC's Guide to Best Practices, SOP:2 (Dickson, Sabine, & Christian, 2007). Total alkalinity samples were processed using the spectrophotometric procedures of Yao and Byrne (1998). Dissolved inorganic carbon in the bay ranged between 3500 µMol/L and 2250 µMol/L and, in the Hillsborough River, peaked at 3700 µMol/L just below the Green Swamp. A comparison of measured total alkalinity and calculated alkalinity (obtained using pH and DIC and CO2sys software) demonstrated the presence of substantial organic base concentrations within the bay.

Investigations of radon in natural water and its relation to physical and chemical parameters are outlined in this thesis. In particular, a method for measuring 222Rn in water at low concentrations (~20 mBq.l-1) is described, followed by discussions concerning the design and its application to study both radon and parameters influencing radon levels in natural waters. A topic considered is the impact of fluoride and other aquatic parameters on radon in water. Moreover, variables such as uranium series radionuclides and stable elements in water, bedrock and sediment radioactivity and geology are investigated in two case studies. This was performed by employing radiometric-, chemical-, statistical- and GIS & geostatistical- analyses. The general water chemistry and presence of some elements such as fluoride was observed to influence radon levels in water. Health aspects of radon in drinking water are discussed based on radiation dose assessments. The radiation doses are compared with and added to doses incurred from ingestion of uranium, radium and polonium isotopes in drinking water and inhalation of radon in air in order to estimate total exposures for different age categories. The results may have a potential for future epidemiological studies.

A baseline study has been undertaken to assess the environmental impact of heavy metals within the fluvial environment of the River Stour, E. Kent, U.K. The occurrence of metal enrichment in surface waters and bed sediments coincides mainly with areas of urbanisation and high density traffic in addition to point source discharges including STW and industrial effluent outlets. Non-tidal surface water samples exhibiting Pb, Co, Cu, Fe and Zn concentrations intermittently elevated above EQS List I and II values largely correspond with bed sediment samples exhibiting metal concentrations above background values and commonly partitioned to the mobile exchangeable/acid soluble and reducible fractions. In the tidal reaches surface water samples exhibiting As, Cd, Co, Cu, Cr, Ni, Pb, V and Zn concentrations above EQS List I and II values are generally associated with bed sediment samples exhibiting partitioning to the immobile oxidisable fraction, suggesting that estuarine processes effectively promote the liberation of elements from the sediment compartment to surface waters. Total catchment annual suspended sediment yield, (190 t/km2/yr), is consistent with previous research work detailing the annual yield of U.K. rivers which in conjunction with suspended sediment concentration data highlights the importance of the transport and distribution of associated elements throughout the river system. Research highlights a requirement to improve point source management measures and control non-point sources and dredging activities and provides an index in which to assess the future impact of anthropogenic sources of metals to the fluvial environment of the River Stour.

An automated on-line SPE-LC-MS/MS method was developed for the quantitation of multiple classes of antibiotics in environmental waters. High sensitivity in the low ng/L range was accomplished by using large volume injections with 10-mL of sample. Positive confirmation of analytes was achieved using two selected reaction monitoring (SRM) transitions per antibiotic and quantitation was performed using an internal standard approach. Samples were extracted using online solid phase extraction, then using column switching technique; extracted samples were immediately passed through liquid chromatography and analyzed by tandem mass spectrometry. The total run time per each sample was 20 min. The statistically calculated method detection limits for various environmental samples were between 1.2 and 63 ng/L. Furthermore, the method was validated in terms of precision, accuracy and linearity. The developed analytical methodology was used to measure the occurrence of antibiotics in reclaimed waters (n=56), surface waters (n=53), ground waters (n=8) and drinking waters (n=54) collected from different parts of South Florida. In reclaimed waters, the most frequently detected antibiotics were nalidixic acid, erythromycin, clarithromycin, azithromycin trimethoprim, sulfamethoxazole and ofloxacin (19.3-604.9 ng/L). Detection of antibiotics in reclaimed waters indicates that they can’t be completely removed by conventional wastewater treatment process. Furthermore, the average mass loads of antibiotics released into the local environment through reclaimed water were estimated as 0.248 Kg/day. Among the surface waters samples, Miami River (reaching up to 580 ng/L) and Black Creek canal (up to 124 ng/L) showed highest concentrations of antibiotics. No traces of antibiotics were found in ground waters. On the other hand, erythromycin (monitored as anhydro erythromycin) was detected in 82% of the drinking water samples (n.d-66 ng/L). The developed approach is suitable for both research and monitoring applications. Major metabolites of antibiotics in reclaimed wates were identified and quantified using high resolution benchtop Q-Exactive orbitrap mass spectrometer. A phase I metabolite of erythromycin was tentatively identified in full scan based on accurate mass measurement. Using extracted ion chromatogram (XIC), high resolution data-dependent MS/MS spectra and metabolic profiling software the metabolite was identified as desmethyl anhydro erythromycin with molecular formula C36H63NO12 and m/z 702.4423. The molar concentration of the metabolite to erythromycin was in the order of 13 %. To my knowledge, this is the first known report on this metabolite in reclaimed water. Another compound acetyl-sulfamethoxazole, a phase II metabolite of sulfamethoxazole was also identified in reclaimed water and mole fraction of the metabolite represent 36 %, of the cumulative sulfamethoxazole concentration. The results were illustrating the importance to include metabolites also in the routine analysis to obtain a mass balance for better understanding of the occurrence, fate and distribution of antibiotics in the environment. Finally, all the antibiotics detected in reclaimed and surface waters were investigated to assess the potential risk to the aquatic organisms. The surface water antibiotic concentrations that represented the real time exposure conditions revealed that the macrolide antibiotics, erythromycin, clarithromycin and tylosin along with quinolone antibiotic, ciprofloxacin were suspected to induce high toxicity to aquatic biota. Preliminary results showing that, among the antibiotic groups tested, macrolides posed the highest ecological threat, and therefore, they may need to be further evaluated with, long-term exposure studies considering bioaccumulation factors and more number of species selected. Overall, the occurrence of antibiotics in aquatic environment is posing an ecological health concern.

Weathering releases lithogenic elements to soil and stream waters that support life in catchment ecosystems. Seasonal and inter-annual variations in hydrologic conditions change subsurface flowpaths, modifying the influence of weathering on stream waters. This study, over two climatically variable years, determined seasonal and inter-annual changes in solute sources to streams using a multi-tracer approach including major cations, strontium isotopes, germanium (Ge)/silica ratios, carbon species, and trace metals. Stream water cations display constant concentrations although discharge response was highly variable, suggesting that there is a consistent subsurface water supply. However, Sr isotope ratios, and concentrations of Ge, Fe, Al, and dissolved organic carbon, which originate from shallow soil waters, increase with the hydrograph during a wet winter snowmelt. This indicates that during a year with a thick snowpack, stream waters contain components of both shallow soilwater and groundwater during snowmelt, whereas during all other times groundwater contributes predominantly to the stream.

Careful treatment of water molecules in ligand-protein interactions is required in many cases if the correct binding pose is to be identified for molecular docking. Water can form complex bridging networks and can play a critical role in dictating the binding mode of ligands. A particularly striking example of this can be found in the ionotropic glutamate receptors (iGluRs), a family of ligand gated ion channels that are responsible for a majority of the fast synaptic neurotransmission in the central nervous system that are thought to be essential in memory and learning. Thus, pharmacological intervention at these neuronal receptors is a valuable therapeutic strategy. This thesis relies on various computational studies and X-ray crystallography to investigate the role of ligand-water mediated interactions in iGluRs bound to glutamate and α-amino-3-hydroxy-5-methyl-4- isoxazole-propionic acid (AMPA). Comparative molecular dynamics (MD) simulations of each subtype of iGluRs bound to glutamate revealed that crystal water positions were reproduced and that all but one water molecule, W5, in the binding site can be rearranged or replaced with water molecules from the bulk. Further density functional theory calculations (DFT) have been used to confirm the MD results and characterize the energetics of W5 and another water molecule implicated in influencing the dynamics of a proposed switch in these receptors. Additional comparative studies on the AMPA subtypes of iGluRs show that each step of the calculation must be considered carefully if the results are to be meaningful. Crystal structures of two ligands, glutamate and AMPA revealed two distinct modes of binding when bound to an AMPA subtype of iGluRs, GluA2. The difference is related to the position of water molecules within the binding pocket. DFT calculations investigated the interaction energies and polarisation effects resulting in a prediction of the correct binding mode for glutamate. For AMPA alternative modes of binding have similar interaction energies as a result of a higher internal energy than glutamate. A combined MD and X-ray crystallographic study investigated the binding of the ligand AMPA in the AMPA receptor subtypes. Analysis of the binding pocket show that AMPA is not preserved in the crystal bound mode and can instead adopt an alternative mode of binding. This involves a displacement of a key water molecule followed by AMPA adopting the pose seen by glutamate. Thus, this thesis makes use of various studies to assess the energetics and dynamics of water molecules in iGluRs. The resulting data provides additional information on the importance of water molecules in mediating ligand interactions as well as identifying key water molecules that can be useful in the de novo design of new selective drugs against iGluRs.

[ES] El nitrógeno (N) es uno de los elementos más importantes para la vida, pero el desequilibrio provocado sobre el ciclo del N está causando daños importantes a muchos ecosistemas en todo el mundo. En aguas costeras, los procesos del N se ven alterados por fertilizantes, la urbanización o la producción de energía. El objetivo principal de esta tesis es contribuir a la evaluación de cómo la actividad antropogénica y el cambio climático modifican la dinámica del N en aguas costeras. Con este propósito se seleccionaron dos lugares de estudio: la demarcación hidrográfica del Júcar (JRBD) en el Noroeste del Mar Mediterráneo y la Región Hidrológica del Golfo Central (CGHR) al Sur del Golfo de México. La tesis se presenta como una colección de cuatro artículos. El primer artículo evalúa cómo la nitrificación en aguas costeras es alterada por las presiones antropogénicas y en asentamientos urbanos en el JRBD. Mediante la aplicación de un modelo biogeoquímico simple que simula la dinámica del nitrito en nueve áreas costeras, se evaluó el desacoplamiento de los dos pasos de la nitrificación. Las conclusiones indican que las presiones antropogénicas modifican los picos de nitrito en invierno debido a las bajas temperaturas y que el segundo paso de la nitrificación es más sensible a la temperatura, lo que implica que el cambio climático puede contribuir al desacoplamiento. El segundo artículo evalúa las tendencias del nitrógeno inorgánico disuelto (NID) por el cambio climático en el JRBD. El efecto de las variables meteorológicas en las concentraciones de NID se estudió mediante la aplicación de redes neuronales artificiales simples entrenadas con datos de campo. Se observaron tendencias decrecientes de nitrito y nitrato a lo largo del siglo XXI bajo los escenarios climático RCP 4.5 y RCP 8.5, debido al aumento de las temperaturas y a la disminución de las precipitaciones, con cambios más significativos en invierno. El amonio no mostró ninguna tendencia anual significativa, pero se observaron aumentos o disminuciones durante algunos meses. En el tercer artículo se desarrolla un nuevo método basado en teoría de sistemas grises y entropía de Shannon para obtener información útil sobre la contaminación por N en áreas donde los datos disponibles son limitados. El método se aplicó a ocho estuarios del CGHR asociados a manglares. Se desarrollaron dos índices: el índice gris de prioridad de gestión de nitrógeno (GNMP) y el índice gris de presión de uso del suelo (GLUP). Ambos fueron comparados para validar la metodología y los resultados indican que la urbanización sobre playas y manglares es la principal causa de la contaminación de N. El cuarto artículo es un análisis espaciotemporal de la contaminación de N a lo largo de dos ríos que desembocan en una zona turística del CGHR asociada a manglares. Mediante técnicas estadísticas como el análisis de cluster, la prueba de MannKendall y la prueba W de MannWhitney, se realizó una evaluación del origen de la contaminación de N y las variaciones temporales de los compuestos de N. Los resultados concluyen que las concentraciones de N orgánico están aumentando a lo largo de la costa, y la principal fuente identificada fue la descomposición de la especie invasora de jacintos de agua en aguas salinas, que ha cubierto completamente las playas y manglares circundantes potenciado por la contaminación de N. El conjunto de la investigación concluye que tanto la contaminación como el cambio climático alteran el ciclo del N en aguas costeras al modificar elementos importantes del N como la nitrificación, las variaciones interanuales de las concentraciones de N o los ecosistemas costeros. Las diferencias en las características ecológicas y socioeconómicas de las dos zonas de estudio desempeñaron un papel decisivo en las presiones e impactos de las actividades antropogénicas. Además, los métodos desarrollados pueden aplicar
[CAT] El nitrogen (N) és un dels elements més importants per a la vida, però el desequilibri provocat sobre el cicle del N està causant danys importants a molts ecosistemes. En aigües costaneres els processos del N es veuen alterats per fertilitzants, el desenvolupament urbà o la producció d'energia. L'objectiu principal d'aquesta investigació és contribuir a l'avaluació de com l'activitat antropogénica i el canvi climàtic modifiquen la dinàmica del N en aigües costaneres. Amb aquest propòsit es van seleccionar dos llocs d'estudi: la demarcació hidrogràfica del Xúquer (JRBD) al Nord-oest de la Mar Mediterrània i la Regió Hidrològica del Golf Central (CGHR) al Sud del Golf de Mèxic. La tesi es presenta com una col·lecció de quatre articles. El primer article avalua com la nitrificació en aigües costaneres es veu alterada per les pressions antropogèniques i prop dels assentaments urbans en el JRBD. Mitjançant l'aplicació d'un model biogeoquímic que simula la dinàmica del nitrit a nou àrees costaneres, es va avaluar el desacoblament dels dos passos de la nitrificació. Les conclusions indiquen que les pressions antropogèniques modifiquen els pics de nitrit observats a l'hivern a causa de les baixes temperaturas i que el segon pas de la nitrificació és més sensible a la temperatura, la qual cosa implica que el canvi climàtic pot contribuir al desacoblament d'aquests dos passos. El segon article avalua les tendències futures de nitrogen inorgànic dissolt (NID) pel canvi climàtic en el JRBD. L'efecte de les variables meteorològiques en les concentracions de NID es va estudiar mitjançant l'aplicació de xarxes neuronals artificials simples entrenades amb dades de camp. Es van observar tendències decreixents de nitrits i nitrats al llarg del segle XXI sota els escenaris climàtics RCP 4.5 i RCP 8.5, a causa de l'augment de les temperatures i a la disminució de les precipitacions, amb canvis més significatius a l'hivern. L'amoni no va mostrar cap tendència anual significativa, però es van observar augments o disminucions durant alguns mesos. En el tercer article es desenvolupa un nou mètode basat en la teoria dels sistemes grisos i l'entropia de Shannon per a obtindre informació útil sobre la contaminació per N en àrees on les dades disponibles són limitats. El mètode es va aplicar a huit estuaris del CGHR associats a manglars. Es van desenvolupar dos índexs: l'índex gris de prioritat de gestió de nitrogen (GNMP) i l'índex gris de pressió d'ús de la terra (GLUP). Els dos van ser comparats per a validar la metodologia. Els resultats indiquen que el desenvolupament urbà sobre platges i manglars és la principal causa de la contaminació de N en l'àrea d'estudi. El quart article és una anàlisi espacio-temporal de la contaminació de N al llarg de dues rius que desemboquen en una zona turística costanera del CGHR associada a manglars. Mitjançant tècniques estadístiques com l'anàlisi de clúster, les proves MannKendall i W de MannWhitney, es va realitzar una avaluació de l'origen de la contaminació de N i les variacions temporals dels compostos de N. Els resultats conclouen que les concentracions de N orgànic estan augmentant al llarg de la costa, i la principal font identificada va ser la descomposició de l'espècie invasora de jacints d'aigua en aigües salines, que ha cobert completament les platges i manglars circumdants potenciat per la contaminació de N. El conjunt de la investigació conclou que tant la contaminació com el canvi climàtic alteren el cicle del N en aigües costaneres en modificar els processos del N com la nitrificació, les variacions interanuals de les concentracions de N i la destrucció dels ecosistemes costaners. Les diferències en les característiques ecològiques i socioeconòmiques de les dues zones d'estudi van exercir un paper decisiu en les pressions i impactes de les activitats antropogèniques. A més, els mètodes desenvolupats poden
[EN] Nitrogen (N) is one of the most important elements for life on Earth, but the unbalance caused to the N cylce is causing dramatic damage to many ecosystems around the world. In coastal waters, the N processes are altered by anthropogenic activities such as the excessive use of fertilizers, urban development or energy production. The main objective of this research is to contribute to the evaluation of how anthropogenic activities and climate change modify the N dynamics in coastal waters. For this purpose, two study sites were selected: the Jucar River Basin District (JRBD) in the Northwestern Mediterranean Sea (Spain) and the Central Gulf Hydrological Region (CGHR) in the Southern Gulf of Mexico (Mexico). The thesis is presented as a collection of four research articles. The first article evaluates how nitrification in coastal waters is altered by anthropogenic pressures and close to urban settlements in the JRBD. Through the application of a simple biogeochemical model that simulates nitrite dynamics to nine coastal areas, an evaluation of the decoupling of the two steps of nitrification was carried out. The main conclusions indicate that anthropogenic pressures modify the nitrite peaks observed in winter driven by low temperatures. The research also concludes that the second step of nitrification is more sensitive to temperature, which entails that climate change may contribute to the decoupling. The second article evaluates the future trends of dissolved inorganic nitrogen (DIN) concentrations under climate change in the JRBD. The effect of meteorological variables on DIN concentrations was studied through the application of simple artificial neural networks trained with field data. Decreasing trends of nitrite and nitrate concentrations were observed throughout the 21st century under both climatic scenarios RCP 4.5 and RCP 8.5, mainly due to rising temperatures and decreasing rainfall, with major changes expected in winter. On the other hand, ammonium did not show any significant annual trend but it either increased or decreased during some months. The third article develops a new method based on grey systems theory and Shannon entropy to derive useful information regarding N pollution in areas where only limited data is available. The method was applied to eight estuaries of the CGHR associated to mangroves. Two indexes were developed: the Grey Nitrogen Management Priority (GNMP) index and the Grey Land Use Pressure (GLUP) index. The two indexes were then confronted to validate the methodology. The results indicate that the urban development over beaches and mangroves is the leading cause of N pollution in the study area. The fourth article is a spatiotemporal analysis of N pollution along two rivers discharging into a touristic coastal area of the CGHR associated to mangroves. Through statistical techniques such as clustering analysis, the Mann-Kendall test and the Mann-Whitney W-test, an evaluation of the origine of N pollution and the temporal variations of the N compounds was performed. The results conclude than organic N concentrations are increasing along the coast, and the main potential source identified was the decomposition of the invasive species of water hyacinths in saline waters, which has completely covered the surrounding beaches and mangroves, enhanced by N pollution. Overall, the main conclusions are that both pollution and climate change alter the N cycle in coastal waters by modifying N processes such as nitrification, the interannual variations of N concentrations and by destroying the coastal ecosystems. The differences in ecological and socio-economic characteristics of the two study sites played a significant role in the pressures and impacts of anthropogenic activities. Moreover, the methods developed can be applied to other coastal regions to evaluate the anthropogenic alteration of the N cycle worldwide.
This thesis was carried out with an international cotutelle between the Polytechnic University of Valencia in Spain and the Veracruzan University in Mexico. This thesis has been financed by the following scholarships: - Erasmus Mundus - MAYANET Grant Agreement Number 2014-0872/001 - 001, funded with support from the European Commission. - Cotutelle PhD scholarship granted by the Universitat Politècnica de València. - Excellence Scholarship awarded by the Mexican Government through the Mexican Agency for International Development Cooperation (AMEXCID)
Temiño Boes, R. (2020). Anthropogenic alteration of the nitrogen cycle in coastal waters: Case studies from the Mediterranean Sea and the Gulf of Mexico [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/158560
TESIS

Koffein (1,3,7-Trimethylxanthin) und Coprostanol (5beta-cholestan-3beta-ol) wurden im Berliner Oberflächenwasser nachgewiesen. Ihre Konzentrationen korrelierten mit dem Verunreinigungsgrad der Proben, was nahelegt, dass sie sich als Marker für menschliche Aktivität eignen. Bemerkenswerterweise wurde Koffein in jeder einzelnen Oberflächenwasserprobe oberhalb der Bestimmungsgrenze von 0,025 µg/L gefunden. Um Oberflächenwasserproben in größeren Serien zu untersuchen, war die Entwicklung zweier neuer Methoden erforderlich: ein Immunoassay, basierend auf einem monoklonalen Antikörper für Koffein und eine dispersive flüssig-flüssig Mikroextraktionsmethode (DLLME), gefolgt von Flüssigkeitschromatographie gekoppelt mit Tandem-Massenspektrometrie (LC-MS/MS) für Coprostanol. Der entwickelte Koffein-Immunoassay zeigt die beste je erhaltene Nachweisgrenze für Koffein (0,001 µg/L), erlaubt Hochdurchsatz-Analysen und erfordert keine Probenvorbereitung. Der Assay wurde auch erfolgreich für die Messung von Koffein in Getränken, Haarwaschmitteln, Koffeintabletten und menschlichem Speichel angewendet. Antikörper gegen Coprostanol sind nicht kommerziell erhältlich. Eine neue Strategie Anti-Coprostanol-Antikörper zu generieren wurde erarbeitet, die eine analoge Verbindung – Isolithocholsäure (ILA) – als Hapten verwendet, mit der eine Gruppe von Mäusen immunisiert wurde. Ein polyklonales Anti-ILA-Serum wurde produziert, welches Coprostanol bindet, aber die niedrige Affinität erlaubte nicht den Aufbau eines Immunoassays, der die Messung von Umweltkonzentrationen des Anayten (im Bereich ng/L) zulässt. Spezifische Anti-ILA-Immunglobuline G wurden auch in den Faeces der Mäuse gefunden. Coprostanol wurde in den Wasserproben durch die Verwendung einer neuentwickelten LC-MS/MS-Methode unter APCI-Ionisation (atmospheric pressure chemical ionisation) gemessen. Konzentrationen oberhalb von 0,1 µg/L wurden nach Voranreicherung der Probe mittels DLLME bestimmt.
Caffeine (1,3,7-trimethylxanthine) and coprostanol (5beta-cholestan-3beta-ol) were detected in samples of Berlin’s surface water. Their concentrations correlated with the contamination status of the samples, suggesting their usefulness as markers of human activity. Remarkably, caffeine concentrations were always well above the limit of quantitation of 0.025 µg/L. In order to screen surface water samples in larger series, the development of two novel methods was required: a monoclonal antibody-based immunoassay for caffeine and a dispersive liquid-liquid microextraction (DLLME) method, followed by liquid chromatography tandem mass spectrometry (LC-MS/MS) for coprostanol. The caffeine immunoassay developed shows the best analytical limit of detection (LOD) obtained so far for caffeine (0.001 µg/L), allows high-throughput analysis, and does not require sample pre-treatment. The assay was also successfully employed to measure caffeine in beverages, shampoos, caffeine tab-lets, and human saliva. Antibodies to coprostanol are not commercially available. A new strategy to generate anti-coprostanol antibodies was elaborated using an analogous com-pound as hapten – isolithocholic acid (ILA) – and immunizing a group of mice. A polyclonal anti-ILA serum was produced, which binds coprostanol but the low affinity did not permit setting up an immunoassay to measure environmental concentrations of the analyte (in the range of ng/L). Specific anti-ILA immunoglobulin G were also found in the faeces of the immunized mice. Coprostanol was quantified in the water samples using a newly developed LC-MS/MS method using atmospheric pressure chemical ionisation (APCI). Concentrations above 0.1 µg/L were determined after sample preconcentration using DLLME. This extraction method also proved to be successful for enrichment of coprostanol-related compounds such as cholesterol, cholestanol, cholestanone, ergosterol, and stigmasterol.

Dans ce travail de thèse on a examiné expérimentalement l’efficacité épuratoire d’un dispositif de filtration, constitué de sable concassé et de nappes de géotextile en fibre de lin, à l’échelle de laboratoire afin d’installer en conditions locales (Agglomération Havraise) un site expérimental en vraie grandeur. Deux types d’essais ont été utilisés : (1) Des essais batch pour quantifier le potentiel de sorption des ions plomb, cuivre et zinc par les étoupes de fibres de lin à partir d'une solution aqueuse. (2) Des essais de filtration de longue durée dans des colonnes en laboratoire remplie de sable concassé avec et sans strates de géotextile en fibres de lin pour étudier l'influence de la présence de géotextiles sur le transfert et la rétention (i) des particules en suspension non polluées (particules de kaolinite) (ii) des métaux lourds solubles dans l'eau (iii) des métaux lourds sous forme particulaire (ions métalliques adsorbés sur les particules de kaolinite en suspension) et métaux lourds et solubles dans l'eau. Les essais de sorption ont montré que l'adsorption des ions métalliques par les fibres de lin est favorable avec une capacité d'adsorption maximale de 9,9 ; 10,7 et 8,4 mg g-1 respectivement pour le cuivre, le plomb et le zinc. Les essais de filtration ont montré que la présence des géotextiles dans le sable influence le transfert des métaux lourds, sous les deux formes soluble et particulaire. La rétention des métaux dans le sable est favorisée et les profils de rétention sont modifiés. De plus, et contrairement aux géotextiles synthétiques, les géotextiles en fibres de lin contribuent eux-mêmes à la rétention d’une fraction non négligeable de polluants métalliques sous forme soluble et particulaire dans leur propre structure. L’efficacité globale de rétention des métaux par le dispositif de filtration est améliorée. Ces résultats sont de bons indicateurs pour envisager l'utilisation de matériaux à base de fibre de lin dans la conception de systèmes de traitement local des eaux de ruissellement et l'élimination de polluants métalliques
In this thesis work, the purification efficiency of a filtration device, consisting of crushed sand and flax fiber geotextile layers, was investigated experimentally at the laboratory scale in order to install in local conditions (Havre agglomeration) an experimental site in full size. Two types of tests were used: (1) Batch tests to quantify the sorption potential of lead, copper and zinc ions by flax fiber tows from an aqueous solution , (2) Long-term filtration tests in laboratory columns filled with crushed sand with and without flax fiber geotextile layers to study the influence of the presence of geotextiles on the transfer and retention of (i) particles in unpolluted suspension (kaolinite particles) (ii) water-soluble heavy metals (iii) heavy metals in particulate form (metal ions adsorbed on suspended kaolinite particles) and heavy and water-soluble metals. Sorption tests have shown that the adsorption of metal ions by flax fibers is favorable with a maximum adsorption capacity of 9.9; 10.7 and 8.4 mg g-1 respectively for copper, lead and zinc. Filtration tests have shown that the presence of geotextiles in sand influences the transfer of heavy metals, in both soluble and particulate forms. The retention of metals in the sand is favored and the retention profiles are modified. In addition, and unlike synthetic geotextiles, flax fiber geotextiles themselves contribute to the retention of a significant fraction of metal pollutants in soluble and particulate form in their own structure. The overall metal retention efficiency of the filtration device is improved. These results are good indicators for considering the use of flax fiber materials in the design of local stormwater treatment systems and the removal of metal pollutants