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Groundwater is a potentially significant source of dissolved organic matter (DOM) to coastal oceans where it is subject to photochemical transformation and thus possibly influences major marine biogeochemical processes. Furthermore, groundwater DOM usually receives little prior light exposure, making it suitable for probing the photoreactivity of source organic materials. In this study we collected two DOM pools in beach and inland groundwater of the Iles-de-la-Madeleine in the Gulf of St. Lawrence, characterized them with absorbance and fluorescence spectroscopy , and compared their photoreactivities. Beach groundwater (BGW) primarily comprised old, highly colored terrestrial DOM having high molecular weight (MW), strong humification , and low protein contents, whereas inland groundwater (IGW) largely contained fresh, less colored microbial-derived DOM with low molecular weight (MW), weaker humification, and higher protein contents. For both BGW and IGW, exposure to solar-simulated radiation led to increases in the E 2/E3 quotient, biological index (BIX), and ammonium (NH4+ ) and decreases in absorbance, specific absorption coefficient at 254 nm (SUVα 254 ), fluorescence index (FI), humification index (HIX), MW, and dissolved organic carbon (DOC). The irradiation also reduced the intensities of humic-like fluorescence peaks and PARAFAC-modeled humic components. On a fractional-absorption-loss basis, the photochemically induced fractional changes in BGW were comparable to those in IGB for SUVα 254 and E2/E3, considerably larger for MW, BIX, and DOC, and substantially smaller for FI and HIX. On an absorbed-photon basis, the efficiencies of absorbance photobleaching and DOC photomineralization for DOM in BGW were 8.3 times and 2.0 times those of the respective photoprocesses for DOM in IGW, while the efficiency of photoammonification for DOM in BGW was 41% of that for DOM in IGW. Results from this study, in combination with those reported previously for surface waters, lead to a tentative paradigm: terrigenous DOM is more prone to absorbance photobleaching but less prone to photoammonification than microbial-derived DOM while the two DOM pools are comparably reactive with respect to DOC photomineralization.

Silver nanoparticles (AgNPs) are incorporated in many consumer products and have a high-releasing potential in aquatic environments. In these environments, AgNPs could interact with colloidal natural organic matter (NOM) affecting their behavior and fate. Aggregation kinetics of AgNPs were conducted at 10 NaCl concentrations during 2 h with 2.5 or 25 mgNOM L−1. Four (4) colloidal NOM fractions were extracted from 50 m3 of St.-Lawrence estuarine waters: fulvic acids (SLFA), humic acids (SLHA), hydrophilic (SL4ILE), and hydrophobic (SL4OBE) fractions. The addition of NOM to AgNP dispersion in nanopure water induced a small increase in AgNP size depending on NOM concentration and fraction used. The presence of both salt and NOM significantly altered the size of silver aggregates. With added 2.5 mgNOM L−1, more than 90% of particles have a size smaller than 200 nm, independently of the NOM fraction used. At 25 mgNOM L−1, the particle size distribution was strongly affected by the nature of NOM fractions. Our results show that NOM with highly aromatic carbon content such as SLFA and SLHA promoted the formation of larger aggregates with a hydrodynamic diameter larger than 200 nm. A high content in non-polar aliphatic carbon as observed in SL4ILE and SL4OBE stabilized aggregates at a size below 200 nm. This study highlights the importance of the chemical composition of NOM fractions and their content in non-polar aliphatic and aromatic carbons as they are involved in hydrophobic effects and strongly influence the aggregate size distribution. Sulfur, also present at low concentration NOM fractions, appears to be involved in the aggregation of AgNPs, but its action mechanism was not determined.

Spillages at sea of diluted bitumen (dilbit) from oil sands have received little attention until now. To our best knowledge, there are no reports on the impact of a severe exposure to dilbit on the Blue mussel (Mytilus edulis). In this study, adult Blue mussels were exposed to one conventional crude oil (Heidrun) and two dilbits (Cold Lake Blend and Access Western Blend) for a period of 7 days in an ice-covered environment and then maintained for three months until the spawning season. The exposed mussels were monitored for aromatic hydrocarbon bioaccumulation, physiological energetic budget, cellular stress, byssus production and gametogenesis. In spring, spawning was induced to characterize breeding success. Bioaccumulation of polycyclic aromatic hydrocarbons (PAHs) was detected after three days of exposure, with higher concentrations of PAHs associated to the conventional oil (5.49 ± 0.12 μg·g−1 d.w.) compared to both dilbits (0.91 ± 0.02 μg·g−1; 0.51 ± 0.03 μg·g−1 d.w.). Despite a fast depuration rate and a good resilience of the exposed mussels, significant negative effects were observed at the cellular, physiological and fitness levels, especially in offspring. Our results suggest a higher toxicity of the diluted bitumen compared to the conventional crude despite the lower bioaccumulation of total PAHs. Dilbit treatments caused evident negative transgenerational effects on unexposed F1 generation.

This study describes aggregation kinetics of silver nanoparticles (AgNPs) and particle size distribution (PSD) of silver aggregates at concentrations ranging from 10 mgAg.L−1 to 10 μgAg.L−1. Aggregation kinetics were conducted at different NaCl concentrations for 2 h and at three environmentally NaCl concentrations (9, 86 and 428 mM) for 12 h to determine the critical coagulation concentration (CCC) and PSD. At mgAg.L−1 level, CCC was near 70 mM, and near 150 mM at μgAg.L−1 level. Furthermore, PSD was strongly affected by AgNPs concentration. At 10 and 1 mgAg.L−1, more than 80 % of aggregates had a hydrodynamic diameter (Dh) higher than 200 nm after 2 h, and more than 95 % after 12 h. At 100 and 10 μgAg.L−1, the main aggregate population had a Dh smaller than 200 nm. At mgAg.L−1 level, particle concentration remained high enough to promote interactions between AgNPs and aggregates, favoring the formation of large aggregates, although it was not the case at μgAg.L−1 level. Moreover, at 106 particles. mL−1, AgNPs aggregation was strongly reduced and could cause the presence of a plateau in aggregation kinetics. Evolution of silver aggregates PSD may increase their residence time in the water column and promotes their exportation to the ocean.

Sorption is a key process in the distribution of substances between environmental compartments in marine ecosystems. Two persistent organic pesticides, also known as toxaphene congeners, namely B8-1413 (P26) and B9-1679 (P50), are of special interest because they are not detected in sediments while relatively concentrated in marine mammals. Sorption–desorption, entrapment and competition behaviors of these pesticides onto marine sediments were studied to explain their environmental distribution. Data obtained under marine experimental conditions were fitted to sorption models to evaluate sorption coefficients and to assess the degree of B8-1413/B9-1679 entrapment of the two toxaphene congeners in sediments. Carbon normalized sorption coefficients ( K oc ) of both congeners were similar under in cold (2 °C) marine (30 psu) conditions with high values ranging from 1.53 × 10 5 to 3.28 × 10 5 mL g −1 indicative of a strong affinity to marine sediments However, the sorption–desorption investigations indicate that B8-1413/B9-1679 were on average 2.5 times less entrapped in sediments compared to B7-1450, a toxaphene congener known to accumulate predominantly in sediments. These results suggest that the low entrapment of B8-1413 and B9-1679 favor their availability and transfer to biological matrices.

Background We conducted a retrospective cohort study to compare the outcomes of laparoscopic colon resection (LCR) with open colon resection (OCR) for complicated diverticular disease (CDD) during emergent hospital admission. Methods Charts from all patients undergoing colon resection for CDD during emergent hospital admission at a single academic institution were reviewed. The primary outcomes were overall 30-day postoperative morbidity and mortality. Results From 2000 to 2010, 125 cases were retrieved (49 LCR and 86 OCR). Conversion rate was 5.1%. Overall morbidity significantly decreased with laparoscopic surgery compared with OCR. No mortality occurred with LCR. Prolonged ileus was less frequent (12.8% vs 32.6%; P = .02), time to oral intake shorter (3 vs 6 days; P P = .05) for LCR. Conclusions In our series, in the patients selected, LCR for CDD during emergent hospital admission appears to be a safe procedure associated with decreased morbidity, time to oral intake, and LOS compared with OCR.

Knowledge of the structural changes that particulate organic matter (POM) undergoes in natural systems is essential for determining its reactivity and fate. In the present study, we used advanced solid-state NMR techniques to investigate the chemical structures of sinking particulate matter collected at different depths as well as humic acids (HAs) extracted from these samples and underlying sediments from the Saguenay Fjord and the St. Lawrence Lower Estuary (Canada). Compared to bulk POM, HAs contain more non-polar alkyls, aromatics, and aromatic C–O, but less carbohydrates (or carbohydrate-like structures). In the two locations studied, the C and N contents of the samples (POM and HAs) decreased with depth and after deposition onto sediments, leaving N-poor but O-enriched HAs and suggesting the involvement of partial oxidation reactions during POM microbial degradation. Advanced NMR techniques revealed that, compared to the water-column HAs, sedimentary HAs contained more protonated aromatics, non-protonated aromatics, aromatic C–O, carbohydrates (excluding anomerics), anomerics, OC q , O–C q –O, OCH, and OCH 3 groups, but less non-polar alkyls, NCH, and mobile CH 2 groups. These results are consistent with the relatively high reactivity of lipids and proteins or peptides. In contrast, carbohydrate-like structures were selectively preserved and appeared to be involved in substitution and copolymerization reactions. Some of these trends support the selective degradation (or selective preservation) theory. The results provide insights into mechanisms that likely contribute to the preservation of POM and the formation of molecules that escape characterization by traditional methods. Despite the depletion of non-polar alkyls with depth in HAs, a significant portion of their general structure survived and can be assigned to a model phospholipid. In addition, little changes in the connectivities of different functional groups were observed. Substituted and copolymerized carbohydrates and fused-ring aromatics detected in the present study likely represented an important part of molecularly uncharacterized components (MUC).

The goal of this work was to evaluate the capability of mid-infrared diffuse reflectance (DRIFT) spectroscopy, coupled with multivariate chemometric analysis, to rapidly provide valuable information on sediment composition and organic geochemistry. A large (150) and heterogeneous set of estuarine sediments was analyzed in their natural matrix by DRIFT. Principal component analysis (PCA) of DRIFT spectra clearly discriminated sediments from distinct deposition events, such as landslides or floods, based on their higher carbonate contents. PCA also distinguished mostly terrigenous sediments, enriched in organic matter, aromatics and SiO 2 , from mostly marine sediments, enriched in clays and carbonates. Partial least-squares (PLS) regression of the DRIFT spectra was used to predict various sediment properties, without the extractions or alterations required by traditional analytical methods. The relative errors in quantifying properties, as expressed by the relative root-mean-squared error (%RMSE), were ~ 6% for total humic substance and humin content, 7.6% for %C, 11.5% for atomic N:C ratio, and 13–14% for %N, %C as humic substances and %C as humin. The study revealed the importance of using a calibration sample set that is representative of the samples to be quantified. This calibration can then be used for the future and rapid analyses of unknown samples. Geochemical processes could also be inferred from band assignments of the loadings of the PLS models. These loadings indicated that nitrogen, humin (%C as humin), and aluminosilicate contents were correlated, providing independent evidence that nitrogen-rich compounds are important bonding agents between the organic and mineral fractions of the sediments. DRIFT-PCA and DRIFT-PLS represent valuable techniques for a rapid and cost-effective screening of sediment core characteristics and for an evaluation of sediment complex composition.

But Cette etude visait a comparer les caracteristiques et le suivi a long terme de patients occidentaux avec cancer gastrique operes avant et apres un stage de formation sur la gastrectomie D2 au Japon. Materiel et methodes Les donnees demographiques, cliniques et pathologiques des patients ayant subi une gastrectomie pour cancer entre 2007 et 2017 dans un hopital academique occidental ont ete analysees, avant (n = 27) et apres (n = 70) le stage de formation. La survie globale a ete evaluee par la methode de Kaplan–Meier. Resultats Apres le stage, le nombre de ganglions preleves a augmente (mediane, 32 vs. 14, p Conclusion Le stage de formation au Japon sur la gastrectomie D2 a ameliore l’etendue du prelevement ganglionnaire et la survie des patients avec cancer gastrique dans un contexte canadien.

Dissolved and particulate organic matters from different stations and depths in the St. Lawrence estuarine system (Canada) were collected and extracted using humic substance (HS) fractionation protocols. The origin, composition, and fate of organic matter/HS were assessed by distribution characteristics, elemental and isotopic compositions, and infrared diffuse reflectance spectroscopy (DRIFTS). HS represented over 50% of dissolved organic matter in the Saguenay Fjord's surface waters but this proportion decreased to 9–19% in the St. Lawrence Lower Estuary (SLLE). Fulvic acids were the dominant component (68–92%) of dissolved HS, especially in high salinity waters having very low humic acid content. Dissolved organic carbon (0.8–7.0 mg L − 1 ) and dissolved HS concentrations steadily decreased with downstream distance and depth. Isotopic and elemental data indicated that dissolved HS were mostly terrigenous, even in the SLLE deep waters. HS represented 62–100% of total particulate organic matter (POM) collected by sediment traps. Humin, the POM associated with the mineral matrix, was the dominant fraction of HS followed by humic acids and fulvic acids. The POM and its HS were mostly terrigenous in the fjord but mostly marine in the SLLE. Unlike its dissolved counterpart, a large part of the POM appeared to be mineralized in the water-column, even at relatively shallow ( − 2 y − 1 was lost during sinking and shortly after deposition, corresponding to an O 2 demand of more than 360 μmolO 2 cm − 2 y − 1 assuming aerobic respiration. Distribution profiles indicated a rapid particulate HS removal during sinking (16–29%) and at the water–sediment interface (up to 70% total removal). These losses were especially important for N-containing molecules, aliphatic components, and marine non-humic POM. In contrast, humin was the most stable fraction. The interactions between POM and the mineral matrix appeared mediated by carboxylate groups. Differences in the composition of dissolved HS and particulate HS may explain their contrasting reactivities. Dissolved HS were nitrogen-poor, more oxidized, and depleted in aliphatic structures as compared to POM. The aliphatic content of dissolved and particulate HS was greater in marine samples (downstream) and decreased during diagenesis. The proportion of CH 3 groups relative to CH 2 groups was surprisingly high in dissolved fulvic acids, an important fraction of DOM. DRIFTS was particularly useful in providing information on HS structures and transformations.

A new type of injector has been developed for gas chromatographic analysis. The injector has high volume and band compression (HVBC) capabilities useful for the analysis of complex samples. The injector consists essentially of a packed liner operated at room temperature while a narrow heated zone is used to axially scan the liner selectively desorbing the compounds of interest. The scanning speed, distance and temperature of the zone are precisely controlled. The liner is connected to an interface which can vent the solvent or any undesirable compounds, and transfer the analytes to an analytical column for separation and quantification. The injector is designed to be compatible with injection volumes from 1 to more than 250microL. At a low sample volume of 1microL, the injector has competitive performances compared to those of the "on-column" and "split/splitless" injectors for the fatty acid methyl esters and toxaphene compounds tested. For higher volumes, the system produces a linear response according to the injected volume. In this explorative study, the maximum volume injected seems to be limited by the saturation of the chromatographic system instead of being defined by the design of the injector. The HVBC injector can also be used to conduct "in situ" pretreatment of the sample before its transfer to the analytical column. For instance, a toxaphene sample was successively fractionated, using the HVBC injector, in six sub-fractions characterized by simpler chromatograms than the chromatogram of the original mixture. Finally, the ability of the HVBC injector to "freeze" the separation in time allowing the analyst to complete the analysis at a later time is also discussed.

It has been shown that visual stimulation can activate cortical regions normally devoted to auditory processing in deaf individuals. This neural activity can persist even when audition is restored through the implantation of a cochlear implant, raising the possibility that cross-modal plasticity can be detrimental to auditory performance in cochlear implant users. To determine the influence of visual information on auditory performance after restoration of hearing in deaf individuals, the ability to segregate conflicting auditory and visual information was assessed in fourteen cochlear implant users with varied degree of expertise and an equal number of participants with normal-hearing matched for gender, age and hearing performance. An auditory speech recognition task was administered in the presence of three incongruent visual stimuli (color-shift, random-dot motion and lip movement). For proficient cochlear implant users, auditory performance was equal to that of controls in the three experimental conditions where visual stimuli were presented simultaneously with auditory information. For non-proficient cochlear implant users, performance did not differ from that of matched controls when the auditory stimulus was paired with a visual stimulus that was color-shifted. However, significant differences were observed between the non-proficient cochlear implant users and their matched controls when the accompanying visual stimuli consisted of a moving random-dot pattern or incongruent lip movements. These findings raise several questions with regards to the rehabilitation of cochlear implant users.

Detailed structural information on two humic acids extracted from two sinking particulate matter samples at a water depth of 20 m in the Saguenay Fjord (F-20-HA) and the St. Lawrence Estuary (E-20-HA) (Canada), was obtained by advanced solid-state NMR. Spectral-editing analyses provided numerous structural details rarely reported in geochemical studies. The NMR data account almost quantitatively for the elemental compositions. The two humic acids were found to be quite similar, consisting of four main structural components: peptides (ca. 39 ± 3% vs. 34 ± 3% of all C for E-20-HA and F-20-HA, respectively); aliphatic chains, 14–20 carbons long (ca. 25 ± 5% vs. 17 ± 5% of all C); aromatic structures (ca. 17 ± 2% vs. 26 ± 2% of all C); and sugar rings (14 ± 2% vs. 15 ± 2% of all C). Peptides were identified by 13 C{ 14 N} SPIDER NMR, which selects signals of carbons bonded to nitrogen, and by dipolar DEPT, which selects CH-group signals, in particular the NCH band of peptides. The SPIDER spectra also indicate that heterocycles constitute a significant fraction of the aromatic structures. The aliphatic (CH2)n chains, which are highly mobile, contain at least one double bond per two chains and end in methyl groups. 1 H spin diffusion NMR experiments showed that these mobile aliphatic chains are in close (

The concentrations of sedimentary humic substances (HS) were measured in the St. Lawrence marine system, Quebec (Canada), including the Saguenay Fjord. Concentration ranges for humin, humic acids and fulvic acids were 7–49, 1–19, and 0.5–6 mg per gram of sediment (dry weight), respectively. HS always represented the dominant component of sediment organic matter (SOM) (i.e., 52–100%) for which humin, humic acids, and fulvic acids accounted for 38–88%, 4–28%, and 2–14%, respectively. These results indicate that most HS and an important part of SOM were associated with the mineral matrix and thus defined as humin. HS concentrations varied slightly by site location and depth but major changes in concentration in the fjord were caused by episodic events such as floods and landslides. In the fjord, sedimentary HS were mostly terrigenous and molecules such as lignin likely contributed to the high proportions of HS. In the St. Lawrence Estuary, an important input of marine particulate organic matter and favorable conditions for its degradation seem to have promoted the mineralization of the labile SOM before its burial. The less labile SOM was buried in sediments where humification and stabilization appeared to occur. Such processes could explain the lower SOM concentrations but greater humin proportions with increasing distance downstream and sediment depth. Estimations based on HS profiles suggest that ∼25% of the surface SOM will be preserved in deeper layers (i.e., >1 m), principally in the form of humin. Sorption of organic matter onto mineral surfaces might have contributed to SOM preservation and humin stabilization in sediments. DRIFT spectroscopy suggests that carboxylate groups may mediate this sorption.

Acquisition of advanced technical skills requires commitment, time, patience, and discipline (eg, the 10-year rule). Dabbling is not a recipe for success. Despite the value of all other teaching methods, guided practice with feedback is essential to develop the high level of visuospatial perceptual ability (observation and performance with feedback) that is necessary for advanced MIS. The necessary ingredients to skill acquisition for advanced MIS procedures (laparoscopic colorectal surgery) for a practicing surgeon include introduction through short courses, access to skill stations, and access to preceptorship or mini-sabbatical. For residents in training, there is no better alternative than an MIS fellowship. In an ideal world where there are enough trainers, the residency environment should provide this training. Comprehensive strategies of knowledge transfer for practicing surgeons should be designed with the input of experts in knowledge transfer.

The sorption of hydrophobic phenanthrene and fluoranthene on whole estuarine particulate matter and humic acid fraction was studied in batch experiments under varying conditions of temperature, salinity, and dissolved humic substances (DHS) concentrations. The use of estuarine particles and dissolved organic matter (here DHS) instead of mineral particles or synthetic organic matter represents an important contribution of this study. A decrease in water temperature and an increase in salinity, such as encountered in estuaries during the transition from river to seawater, together increased the fraction of the contaminants sorbed to the particles by 40% to 64%, on average. The sorption observed at different temperatures indicates a slightly exothermic sorption process with calculated enthalpies between −4.5 and −13.2 kJ/mol. The impact of both temperature and salinity variations can be chiefly attributed to changes in the contaminant's water solubility. The calculated isotherm parameters, sorption enthalpies and entropies are in agreement with a sorption dominated by partitioning between water and unsaturated particles. Nevertheless, these calculations also reveal a low proportion of sorption sites having higher energy (e.g., site-specific adsorption) than those involved in partitioning. The effect of DHS upon the sorption of fluoranthene onto estuarine particles was negligible or minor, depending on the DHS concentrations. Although DHS may have a relatively high affinity for the fluoranthene fraction that remains in solution after sorption, their capacity to compete with the particles during the sorption is surprisingly low. This finding cannot be predicted by the generally high DHS partition coefficients ( K DOM ) reported. The impacts of the three parameters studied upon sorption and sediment trapping may be less important than those caused by changes in the composition or in the concentration of suspended particulate matter in estuaries. This may explain why the influence of these parameters is difficult to observe in field studies.

Following a catastrophic flash flood in July 1996, as much as 50 cm of post-glacial clays were deposited in less than 2 days in the upper reaches of the Saguenay Fjord (Quebec, Canada), disrupting the normal sedimentation and diagenetic regimes. We report detailed geochemical analyses of sediments (porosity, Eh, organic and inorganic carbon, Fe and Mn reactive solid phases, and acid volatile sulfide) and porewaters (salinity, dissolved organic carbon (DOC), Fe(II), Mn(II), nitrate, ammonium, and sulfate) for seven stations located in the Saguenay Fjord. Three of these (SAG-05, SAG-09, and SAG-30) were visited in 1996 and once per year thereafter to document the chemical evolution of the sediment toward a new steady state. The flood deposits contain less organic carbon and more inorganic carbon than the indigenous fjord sediments. The flood deposit modified the distribution patterns of reactive Mn and Fe as a result of the reduction of Mn and Fe oxides delivered with the deposit and those concentrated at the now buried former sediment-water interface. Most of the Mn(II) migrated to the new sediment-water interface, where a Mn-rich layer was formed. In contrast, much of the Fe(II) was precipitated as sulfides and remained trapped at or close to the old interface. A nitrate peak developed in the porewater at the old sediment-water interface, possibly because of the oxidation of ammonia by Mn oxides. The distributions of porewater DOC within the flood deposit correlate with the distributions of dissolved Mn(II) and Fe(II), suggesting that adsorbed DOC was released when metal oxides were reduced.

The speech intelligibility of syllables spoken under conditions of conversational and clear speech was compared. The stimuli were 18 monosyllables (/C-v/) and 18 bisyllables (/v-C-v/) consisting of six voiced-consonants (/b, d, g, v, z, ʒ /) presented in each of three vowel contexts (/a, i, y/). Six female adults were recorded while they produced four iterations of the stimulus set in each of the two speaking styles. The 1728 videotaped test items were edited, randomized and presented to 12 subjects with normal hearing and normal visual acuity under three conditions: visual-only, auditory-only and audiovisually. A broadband noise was mixed with the signal for the latter two conditions. The results revealed a significant three-way interaction of talker, speaking style and perceptual modality. Post-hoc analyses revealed intra and interspeaker differences in speech intelligibility for both speaking styles, in all three perceptual modalities. Overall, positive clear speech effects were observed in all three modalities. Intermodality comparisons revealed differences in the pattern of clear speech effects displayed by individual talkers. This finding indicates that there is not a direct association between the beneficial effects of clear speech in one perceptual modality and its effects on speech intelligibility in another perceptual modality.

The Gulf of St. Lawrence and Scotian Shelf provide a diversity of oceanographic conditions in a continental margin setting. Climate is markedly seasonal, and bathymetry and hydrodynamic conditions cover a broad range, significantly influencing the patterns of organic matter sedimentation and, potentially, benthic community dynamics. Samples for analysis of benthic macrofauna and sediment microorganisms were collected at six stations in the Gulf of St. Lawrence (GSL) and the Scotian Shelf during winter and summer cruises, as part of the Canadian Joint Global Ocean Flux Study. Multivariate analyses indicate significant site-related trends in trophic guilds, benthic assemblages, and microbial activity, some of which are related to geomorphological characteristics (bathymetry, topography, and substratum). Macrofaunal trophic guild data show that the stations with relatively deep settling basins (Cabot Strait and Emerald Basin), dominated by surface deposit feeders, were distinct from stations with sloping bottoms (Anticosti Gyre and Anticosti Channel), where subsurface deposit feeders dominated or surface and subsurface deposit feeders were equally abundant. Deposit feeders (surface and subsurface trophic groups) made up >60% of the benthic communities, except at the Scotian slope station where they represented 44% of the total benthic abundances. Based on the data collected in both the water column and the sediment at three deep stations in the GSL, we hypothesize that the proportion of surface and subsurface deposit feeders, and thus the nature of bioturbation activity, is related to the magnitude and pattern of organic matter supply from the euphotic zone.

Elemental and molecular organic matter concentrations were analyzed in sediments from the Lower St. Lawrence Estuary and the Saguenay Fjord in order to evaluate the historic evolution of pulp and paper mills solid-waste inputs in the system in the last decades and the relative reactivities of lignin and bulk organic materials in coastal sediments. A qualitative estimation of vascular plant sources to the Saguenay Fjord shows that the sedimentary terrigenous plant material is comprised predominantly of gymnosperm woods. In the deeper sediment horizons of the upper Saguenay basin, low intensive lignin parameters ( C V and S V ) and high percentages of lignin to total sedimentary organic carbon (> 20%) all indicate elevated concentrations of woody gymnosperm tissues unprecedented in coastal sediments and directly related to the intense activity of the region's pulp and paper industries. The increased control on solid organic wastes from industrial effluents into the Saguenay river in the late 1980s to early 1990s is clearly apparent from increasing intensive parameter values and decreasing lignin fractions to the total sedimentary organic carbon (≈ 6–8%) in the upper basin surface sediments. Elemental and molecular analyses of fjord sediments, all indicate that most of the solid-phase discharge of lignified material by the pulp and paper industry is deposited rapidly close to the mouth of the river without reaching the downstream basins. In the St. Lawrence Estuary, intensive lignin parameters indicate that gymnosperm tissues are a major component of the sedimentary vascular plant material but with a significant fraction composed of angiosperm and nonwoody tissues. These latter types of organic tissues are particularly important components of terrigenous material in sediments deposited prior to the 1910–1920s. Acid/aldehyde ratios in most cores studied do not indicate clear-cut oxidative degradation of lignin material prior to its introduction in the aquatic system. The only exceptions are the two estuarine cores, where slightly elevated acid/aldehyde ratios relative to the range for fresh vascular plant tissues, might indicate mild aerobic fungal degradation of the sedimentary lignin material. Organic carbon, total nitrogen, organic phosphorus and lignin derived phenols all exhibited decreasing concentrations with core depth in the sediments of the Lower St. Lawrence Estuary. First-order degradation rate constants for all four chemical categories ranged between 0.02–0.05 yr−1. The order of apparent reactivity among the different organic compounds is TN ≥ Corg > Porg > lignin at the head of the Laurentian channel and lignin ≈ TN = Corg > Porg further downstream. The surprising diagenetic selectivity observed at the upstream station is probably due to a higher flux of fresh, labile organic matter that reaches the sediment-water interface and degrades preferentially to more refractory materials such as lignin. Further downstream, little diagenetic selectivity was observed below the sediment-water interface indicating an overall refractory nature of the sedimentary organic matter. Finally, the differences in reactivity observed between Corg and Porg at both stations contradict earlier assumptions that no fractionation occurs between organic carbon and phosphorus during anaerobic degradation.

The monitoring of the chromatographic resolution for three pairs of analytes separated in different chromatographic systems using mobile phases with varying concentrations of viscous fast atom bombardment matrices showed that it exhibits a steady decrease with increasing matrix content in the mobile phase. The decrease in resolution is observed in the partition and ion-pair chromatographic modes at both low and high matrix contents in the eluent for both conventional and capillary chromatographic systems using precolumn addition of glycerol and thioglycerol. Careful examination of the normalized efficiency, capacity factor and selectivity terms contributing to the resolution allowed the identification of the sources of the decrease in resolution in the presence of a matrix in the eluent. Ale efficiency and capacity factor terms show decreases with increasing matrix content in all systems. Subtle variations in the selectivity term observed in the presence of a viscous matrix can increase or limit the decrease in resolution. The variations observed for the efficiency term show similar trends in all systems studied and appear to be independent of the analyte or the chromatographic mode. However, the variations in capacity factor and selectivity induced by the presence of the viscous matrix are dependent on the nature of the analyte, the type of chromatography and the nature of the matrix.

A series of experiments were conducted in order to evaluate the boundaries within which precolumn addition of viscous matrices can be systematically used in capillary LC—fast atom bombardment MS systems and to evaluate the broadening caused by components of the systems such as the column, the transfer capillary tube and the probe interface. The effect of the addition of a viscous matrix on the capillary system was studied by monitoring important chromatographic parameters such as capacity factors, selectivity, number of theoretical plates, peak width and resolution. The results obtained indicate that glycerol contents in the mobile phase higher than 5% have a deleterious effect on most chromatographic indicators. The overall effect of the presence of glycerol on the chromatographic system can be rationalized in terms of the modification of the analyte distribution between the mobile and stationary phases and changes in the kinetics of the system created by an increase in the viscosity of the mobile phase. Ale main contribution to band broadening in the system can be attributed to the interface and is related to the formation of a liquid droplet at the tip of the probe. Other contributions such as broadening in the column and in the transfer capillary affect the total variance of the chromatographic system but to a smaller extent.

A series of experiments were conducted in order to determine the effect of the precolumn addition of a viscous matrix such as thioglycerol on the chromatographic performance of liquid chromatographic-fast atom bombardment mass spectrometric (LC-FAB-MS) systems. In those experiments, the concentration of thioglycerol in a mobile phase consisting of acetonitrile-water-trifluoroacetic acid was varied and important chromatographic parameters such as retention times, capacity factors, number of theoretical plates, peak widths, resolution and impedance of separation were monitored for analytes such as met-enkephalin, leu-enkephalin and p-hydroxybenzoic acid. The results obtained indicate that for concentrations of thioglycerol in the mobile phase below 3% most chromatographic indicators are only slightly affected. However, for concentrations of the viscous matrix above that value the capacity factors are significantly decreased, indicating that thioglycerol is behaving as an efficient organic moderator, and peak broadening becomes important, having a detrimental effect on the performance of the system. Van Deemter plots obtained for the analytes at concentrations of thioglycerol in the mobile phase of 0-15% reveal that the major effect of thioglycerol is to reduce the mass transfer efficiency in the chromatographic system at high velocities and concentrations of thioglycerol above 3%. Comparison of the effects of viscous matrices such as thioglycerol and glycerol on the chromatographic performance of LC-FAB-MS systems indicates that the chromatographic efficiency is almost independent of the matrix concentration when the systems are operated near their optimum linear velocities and that high matrix contents and high linear velocities can be used with little decrease in efficiency if the systems are operated at higher temperatures.

The effect of the pre-column addition of a viscous matrix to the mobile phase in liquid chromatographic-fast atom bombardment mass spectrometric experiments was studied with respect to the chromatographic process. A series of experiments, designed to discriminate against the mass spectral components, were conducted with six compounds, ranging in mass from 100 to 1100 daltons and distributed into three chemical classes. Several chromatographic indicators such as retention times, capacity ratios, number of theoretical plates, peak widths, resolution and separation impedance were monitored as a function of the glycerol content of the mobile phase. The results obtained indicate that the retention times and the capacity ratios decrease with increasing glycerol content of the mobile phase. Increasing concentrations of glycerol also reduce the number of theoretical plates in the chromatographic system and generally have a detrimental effect on peak widths for glycerol contents above 5%. However, lower glycerol contents produce negative effects on compounds with smaller capacity ratios but not on compounds with higher capacity ratios such as peptides. Furthermore, the increase in glycerol concentrations reduces the chromatographic resolution for all classes of compounds studied and creates a significant increase in the separation impedance of the system, resulting in higher operation pressures. The overall effect of a viscous matrix in the chromatographic system can be rationalized in terms of the modification of the analyte distribution between phases and changes in the kinetics of the system created by an increase in mobile phase viscosity.

The factors affecting band broadening in liquid chromatographic-fast atom bombardment mass spectrometric (LC-FAB-MS) systems using precolumn addition of glycerol to the mobile phase were investigated and their relative importance evaluated. The integrated LC-MS system is subject to three sources of band broadening, namely the chromatographic system, the interface and the mass spectrometer. The individual variances associated with these components can be used to estimate the total variance of the system. The factors affecting broadening in the chromatographic system were identified by examination of the Van Deemter plots obtained for several types of compounds at glycerol concentrations ranging from 0 to 20%. The plots reveal that the C term is significantly affected by an increase in glycerol concentration and that the main factor affecting broadening is a change in the diffusion coefficient, D m . The increase in the variance associated with the dead volume of the chromatographic system, as measured with a non-retained species, indicates that the increase in the viscosity of the mobile phase on addition of glycerol also results, to a lesser extent, in band broadening as a consequence of the change in flow dynamics within the system. Investigation of the factors affecting band broadening in the interface show that the main source of broadening is the wetting of the probe tip, which is far more important than the dead volume introduced by the transfer capillary. The band broadening induced by the mass spectrometer in the LC-FAB-MS system is essentially related to the scanning speed used for the analysis.

A simple and inexpensive direct liquid introduction system that can be used for tandem mass spectral analysis and for interfacing liquid chromatography on quadrupole and magnetic-sector mass spectrometers is described. The interface consists of a transfer fused-silica capillary that is introduced directly into the chemical ionization source of the mass spectrometer through the conventional gas chromatography-mass spectrometry interface, replacing the capillary column. The coupling uses no desolvation chamber and the transfer capillary is heated over the whole length of the interface. Experiments on the effect of interface temperature and flow-rate demonstrate that the system is extremely stable under optimal operating conditions, which are similar on different spectrometers. The chemical ionization plasma generated by the mobile phase under typical operation consists mainly of protonated monomers, and its composition is similar on different spectrometers, as shown by the comparison of spectra obtained. The system can be used with a series of mobile phases, and the ionization features that they produce are comparable. The system is stable, reproducible and allows picogram range sensitivity to be achieved in mass spectrometric, tandem mass spectrometric or liquid chromatographic-mass spectrometric experiments.