Natural organic matter fractions and their removal in full-scale drinking water treatment under cold climate conditions in Nordic capitals.

Drinking water treatment plants (DWTPs) designed to remove natural organic matter (NOM) are challenged as concentrations of NOM in raw waters are increasing. Here, we assess seasonal differences in NOM quality and quantity, from raw waters to the distribution network, at three large DWTPs in Oslo, Stockholm and Helsinki. Samples, collected during stable stratification in both winter and summer and during the autumnal turnover, were analysed for NOM concentrations and composition. The NOM was characterized by common routine parameters, size and content (TFF, LC-OCD, fluorescence) and biodegradability. The NOM concentration decreased to 2.5 mg/L (55%), 4.0 mg/L (48%) and 5.7 mg/L (76%) at the respective DWTPs in Oslo, Stockholm and Helsinki. The NOM in raw waters were predominantly in the largest size fraction (>50 kDa), in particular from Oslo. High MW fractions >50 kDa and humics remained the largest fractions with minimum 30% and maximum 80% of the total NOM. The BDOC in treated water <0.3 mg/L and the conditions in the distribution network imply low probability for bacteria regrowth. The multi-step treatment consisting of coagulation/flocculation, sedimentation, rapid sand filtration, ozonation and biological activated carbon filtration (BAC) was most effective in removing NOM. Coagulation/flocculation followed by sedimentation and sand filtration were critical, especially for the removal of biopolymers and humics, and somewhat for building blocks. The sand filtration provided up to 25% additional removal of biopolymers and below 7% removal of other fractions. The ozonation and BAC was more effective and removed 11% of biopolymers, and about 35% of building blocks and LMW neutrals.

Tracking changes in the optical properties and molecular composition of dissolved organic matter during drinking water production.

Absorbance, 3D fluorescence and ultrahigh resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FT-ICR-MS) were used to explain patterns in the removal of chromophoric and fluorescent dissolved organic matter (CDOM and FDOM) at the molecular level during drinking water production at four large drinking water treatment plants in Sweden. When dissolved organic carbon (DOC) removal was low, shifts in the dissolved organic matter (DOM) composition could not be detected with commonly used DOC-normalized parameters (e.g. specific UV254 absorbance - SUVA), but was clearly observed by using differential absorbance and fluorescence or ESI-FT-ICR-MS. In addition, we took a novel approach by identifying how optical parameters were correlated to the elemental composition of DOM by using rank correlation to connect optical properties to chemical formulas assigned to mass peaks from FT-ICR-MS analyses. Coagulation treatment selectively removed FDOM at longer emission wavelengths (450-600 nm), which significantly correlated with chemical formulas containing oxidized carbon (average carbon oxidation state ≥ 0), low hydrogen to carbon ratios (H/C: average ± SD = 0.83 ± 0.13), and abundant oxygen-containing functional groups (O/C = 0.62 ± 0.10). Slow sand filtration was less efficient in removing DOM, yet selectively targeted FDOM at shorter emission wavelengths (between 300 and 450 nm), which commonly represents algal rather than terrestrial sources. This shorter wavelength FDOM correlated with chemical formulas containing reduced carbon (average carbon oxidation state ≤ 0), with relatively few carbon-carbon double bonds (H/C = 1.32 ± 0.16) and less oxygen per carbon (O/C = 0.43 ± 0.10) than those removed during coagulation. By coupling optical approaches with FT-ICR-MS to characterize DOM, we were for the first time able to confirm the molecular composition of absorbing and fluorescing DOM selectively targeted during drinking water treatment.

Assessment of uncertainty in long-term mass balances for acidification assessments: a MAGIC model exercise.

Long-term (1860-2010) catchment mass balance calculations rely on models and assumptions which are sources of uncertainty in acidification assessments. In this article, we report on an application of MAGIC to model acidification at the four Swedish IM forested catchments that have been subject to differing degrees of acidification stress. Uncertainties in the modeled mass balances were mainly associated with the deposition scenario and assumptions about sulfate adsorption and soil mass. Estimated base cation (BC) release rates (weathering) varied in a relatively narrow range of 47-62 or 42-47 meq m(-2) year(-1), depending on assumptions made about soil cation exchange capacity and base saturation. By varying aluminum solubility or introducing a dynamic weathering feedback that allowed BC release to increase at more acidic pHs, a systematic effect on predicted changes in acid neutralizing capacity (ΔANC ca. 10-41 µeq l(-1)) and pH (ca. ΔpH = 0.1-0.6) at all sites was observed. More robust projections of future changes in pH and ANC are dependent on reducing uncertainties in BC release rates, the timing, and extent of natural acidification through BC uptake by plants, temporal changes in soil element pools, and fluxes of Al between compartments.

Simulating dissolved organic carbon dynamics at the swedish integrated monitoring sites with the integrated catchments model for carbon, INCA-C.

Surface water concentrations of dissolved organic carbon ([DOC]) are changing throughout the northern hemisphere due to changes in climate, land use and acid deposition. However, the relative importance of these drivers is unclear. Here, we use the Integrated Catchments model for Carbon (INCA-C) to simulate long-term (1996-2008) streamwater [DOC] at the four Swedish integrated monitoring (IM) sites. These are unmanaged headwater catchments with old-growth forests and no major changes in land use. Daily, seasonal and long-term variations in streamwater [DOC] driven by runoff, seasonal temperature and atmospheric sulfate (SO4(2-)) deposition were observed at all sites. Using INCA-C, it was possible to reproduce observed patterns of variability in streamwater [DOC] at the four IM sites. Runoff was found to be the main short-term control on [DOC]. Seasonal patterns in [DOC] were controlled primarily by soil temperature. Measured SO4(2-) deposition explained some of the long-term [DOC] variability at all sites.

Effects of aerobic exercise training on cognitive function and cortical vascularity in monkeys.

This study examined whether regular exercise training, at a level that would be recommended for middle-aged people interested in improving fitness could lead to improved cognitive performance and increased blood flow to the brain in another primate species. Adult female cynomolgus monkeys were trained to run on treadmills for 1 h a day, 5 days a week, for a 5 month period (n=16; 1.9+/-0.4 miles/day). A sedentary control group sat daily on immobile treadmills (n=8). Half of the runners had an additional sedentary period for 3 months at the end of the exercise period (n=8). In all groups, half of the monkeys were middle-aged (10-12 years old) and half were more mature (15-17 years old). Starting the fifth week of exercise training, monkeys underwent cognitive testing using the Wisconsin General Testing Apparatus (WGTA). Regardless of age, the exercising group learned to use the WGTA significantly faster (4.6+/-3.4 days) compared to controls (8.3+/-4.8 days; P=0.05). At the end of 5 months of running monkeys showed increased fitness, and the vascular volume fraction in the motor cortex in mature adult running monkeys was increased significantly compared to controls (P=0.029). However, increased vascular volume did not remain apparent after a 3-month sedentary period. These findings indicate that the level of exercise associated with improved fitness in middle-aged humans is sufficient to increase both the rate of learning and blood flow to the cerebral cortex, at least during the period of regular exercise.

Imaging considerations for in vivo 13C metabolic mapping using hyperpolarized 13C-pyruvate.

One of the challenges of optimizing signal-to-noise ratio (SNR) and image quality in (13)C metabolic imaging using hyperpolarized (13)C-pyruvate is associated with the different MR signal time-courses for pyruvate and its metabolic products, lactate and alanine. The impact of the acquisition time window, variation of flip angles, and order of phase encoding on SNR and image quality were evaluated in mathematical simulations and rat experiments, based on multishot fast chemical shift imaging (CSI) and three-dimensional echo-planar spectroscopic imaging (3DEPSI) sequences. The image timing was set to coincide with the peak production of lactate. The strategy of combining variable flip angles and centric phase encoding (cPE) improved image quality while retaining good SNR. In addition, two aspects of EPSI sampling strategies were explored: waveform design (flyback vs. symmetric EPSI) and spectral bandwidth (BW = 500 Hz vs. 267 Hz). Both symmetric EPSI and reduced BW trended toward increased SNR. The imaging strategies reported here can serve as guidance to other multishot spectroscopic imaging protocols for (13)C metabolic imaging applications.

In vivo 13 carbon metabolic imaging at 3T with hyperpolarized 13C-1-pyruvate.

We present for the first time dynamic spectra and spectroscopic images acquired in normal rats at 3T following the injection of (13)C-1-pyruvate that was hyperpolarized by the dynamic nuclear polarization (DNP) method. Spectroscopic sampling was optimized for signal-to-noise ratio (SNR) and for spectral resolution of (13)C-1-pyruvate and its metabolic products (13)C-1-alanine, (13)C-1-lactate, and (13)C-bicarbonate. Dynamic spectra in rats were collected with a temporal resolution of 3 s from a 90-mm axial slab using a dual (1)H-(13)C quadrature birdcage coil to observe the combined effects of metabolism, flow, and T(1) relaxation. In separate experiments, spectroscopic imaging data were obtained during a 17-s acquisition of a 20-mm axial slice centered on the rat kidney region to provide information on the spatial distribution of the metabolites. Conversion of pyruvate to lactate, alanine, and bicarbonate occurred within a minute of injection. Alanine was observed primarily in skeletal muscle and liver, while pyruvate, lactate, and bicarbonate concentrations were relatively high in the vasculature and kidneys. In contrast to earlier work at 1.5 T, bicarbonate was routinely observed in skeletal muscle as well as the kidney and vasculature.

NMR study of the metabolic 15N isotopic enrichment of cyanophycin synthesized by the cyanobacterium Synechocystis sp. strain PCC 6308.

1H, 13C and 15N nuclear magnetic resonance (NMR) spectroscopy has been used to characterize cyanophycin, a multi-l-arginyl-poly-[l-aspartic acid] polypeptide from the cyanobacterium Synechocystis sp. strain PCC 6308. 1H, 13C and 15N chemical shifts and 1JHN and 1JCN coupling constants were measured in isolated 15N-labeled cyanophycin, and showed chemical shift values and J-couplings consistent with the reported polypeptide structure. 15N enrichment levels were determined from the extent of 1H-15N J-coupling in 1H NMR spectra of cyanophycin. Similar experiments using 13C-15N coupling in 13C NMR spectra were not useful in determining enrichment levels.

Evaluation of the clinical performance of automated proton magnetic resonance spectroscopy in children.

RATIONALE AND OBJECTIVES: Because expeditious neuroimaging is imperative in pediatric patients, we evaluated automated procedures for proton magnetic resonance spectroscopy (1H MRS) of the brain of children. METHODS: 1H MRS was performed on a 1.5-T GE Signa. The protocol included stimulated echo-acquisition mode and spin-echo point resolved spectroscopy. The automated routine included adjustment of first-order gradient shims (x, y, z1) to optimize magnetic field homogeneity, transmit power, center frequency, receiver gain, and water suppression. All spectra were processed with the use of spectroscopy analysis software from General Electric on a Sun workstation. RESULTS: The use of the automated procedures reduced the length of our 1H MRS protocol by 50%. Magnetic field homogeneity was within our accepted standards (7 +/- 2 Hz). Water suppression was within range of our accepted factors (1000-10,000). However, on certain occasions, baseline distortions affected resonances in the 3.22-4.04 ppm range. CONCLUSIONS: Shortening of the time required for clinical 1H MRS will increase its application in evaluating children.

Automated single-voxel proton MRS: technical development and multisite verification.

To improve clinical utility, an integrated method has been developed to automatically acquire and process single-voxel in vivo proton spectra on a 1.5 T clinical scanner. This method includes automated adjustment of linear shims using a very rapid modified simplex method, automated water suppression, and applies a water referencing scheme to correct for phase and residual eddy current effects. No operator intervention is required for the acquisition and processing of these pure-absorption spectra. This method was tested in a preliminary multisite trial to determine intersite and intrasite variability of metabolite ratio measurements. In a sample of over 100 examinations, the standard deviation of the ratios NAA:Cr, Cho:Cr, and ml:Cr were found to be under 15% when using this method, a substantially narrower range than has been found in studies relying on manual adjustment of the instrument and/or manual processing. This result indicates that automated setting of acquisition and processing parameters is of critical importance in the clinical application of in vivo spectroscopy.

A feasibility study of 23Na magnetic resonance imaging of human and rabbit vitreal disorders.

PURPOSE: To assess the clinical feasibility of sodium magnetic resonance imaging for the visualization and characterization of intraocular tissues. METHODS: 23Na magnetic resonance images were obtained of enucleated human eyes and of rabbit eyes in vivo. The magnetic resonance imaging technique used in this study provided slices of < 2 mm thickness and in-plane resolution of < 2 x 2 mm. From each of these slices local values of spin-spin relaxation time (T2*) were calculated from pixel intensities in each of the eight echoes. RESULTS: The images clearly display normal anatomic details of the lens and vitreous humor, and important pathologic details such as intravitreal and subretinal hemorrhages, ocular melanoma, and retinal detachments. Intraocular tissue identifications based on relative spin-spin relaxation time values and pixel intensities correlate with those made by standard diagnostic techniques. CONCLUSIONS: 23Na magnetic resonance imaging may be used for the visualization and characterization of intraocular tissues. Differentiation among vitreous humor, lens, aqueous humor, subretinal fluid, or hemorrhage and tumor may be based on image intensity and/or spin-spin relaxation times.

In vivo sodium chemical shift imaging.

The shift reagents thulium(III) 1,4,7,10-tetraazacyclododecane N,N',N",N"'tetramethylenephosphonate (TmDOTP5-), and dysprosium(III)triethylenetetramine-hexaacetate (DyTTHA3-) are compared in this work for their uses in sodium chemical shift imaging (NaCSI). In a series of experiments using phantoms we evaluated the relative contributions of bulk magnetic susceptibility (BMS) effects and hyperfine shifts to the induced 23Na chemical shift for these two shift reagents. The ratios of BMS effects to hyperfine shifts suggest that TmDOTP5- should be a more effective shift reagent than DyTTHA3- for 23Na NMR spectroscopy as well as NaCSI. The dependence on pH and free Ca2+ concentration of the 23Na NMR frequency shift induced by TmDOTP5- was evaluated. It was found that TmDOTP5- produces good spectral resolution under physiologic conditions. Examples presented from in vivo NaCSI experiments using TmDOTP5- to study diffusion in the posterior chamber of the rabbit eye and to monitor the rate of clearance of aqueous fluid from the anterior chamber demonstrate the effectiveness of this new shift reagent and of the NaCSI technique for in vivo studies.

Dynamic sodium chemical shift imaging for the study of aqueous humor flow.

Ocular images were obtained using sodium chemical shift imaging (CSI) and 1,4,7,10-tetraazacyclododecane-N,N'N",N"'-tetramethylenephospho nate thulium (III) [Tm(DOTP)5-], a paramagnetic chemical shift reagent. After injecting the shift reagent into the anterior chamber of rabbits, serial imaging was done, monitoring the change in chemical shift with time. Sodium CSI produced images of the eye in three dimensions, quantitatively depicting the spatial and temporal changes in the concentration of a paramagnetic tracer substance. The Tm(DOTP)5- is eliminated from the anterior chamber by first-order kinetics with a half-life of 49 min. These data suggest that this substance is eliminated from the anterior chamber at the same rate as aqueous humor is replaced. Sodium CSI shows promise as a valuable technique for monitoring fluid dynamics in the living eye.

Analysis of 23Na NMR spectra from isolated perfused hearts.

The 23Na NMR spectra obtained from isolated hearts perfused with buffer containing the paramagnetic shift reagent dysprosium triethylenetetraminehexaacetic acid, Dy(TTHA)3-, are complex and contain a number of overlapping peaks of different intensities. Spectra from rat, rabbit, guinea pig, and ferret hearts obtained during periods of control perfusion are similar and undergo similar changes when the hearts are subjected to periods of ischemia and reflow. The contributions from the intracellular, interstitial, vascular, and bath compartments to the multiple peaks in the spectra of rats hearts have been assigned. The significant contributions to these spectra of bulk magnetic susceptibility effects and incomplete mixing have been demonstrated through a series of modeling experiments. Since the spectra from hearts of different species are so similar, the peak assignments made for the rat are applicable to spectra from rabbit, guinea pig, and ferret hearts as well. This work provides a framework for quantitative analysis of the spectral changes which occur during conditions such as ischemia and reflow.

31P nuclear magnetic resonance spectroscopy study of the anaerobic threshold in humans.

The relationships among the lactate threshold (LT), ventilatory threshold (VT), and intracellular biochemical events in exercising muscle have not been well defined. Therefore 14 normal subjects performed incremental plantar flexion to exhaustion on 2 study days, the first for determination of LT and VT and the second for continuous 31P nuclear magnetic resonance spectroscopy of calf muscle. Exercising calf muscle pH fell precipitously at 66.4 +/- 3.4% (SE) of the maximum O2 uptake (VO2max) and was termed the intramuscular pH threshold. This did not occur at a significantly different metabolic rate from that at the LT (78.6 +/- 5.9% VO2max) or at the VT (75.0 +/- 4.1% VO2max, P = 0.15 by analysis of variance). Four subjects showed an intramuscular pH threshold and VT without a perceptible rise in forearm venous blood lactate. It is concluded that traditional markers of the "anaerobic threshold," the LT and VT, occur as intramuscular pH becomes acid for a group of normal subjects undergoing incremental exercise to exhaustion. It is speculated that neuronal pathways linking intramuscular biochemical events to the ventilatory control center may explain the intact VT in those subjects without an "intermediary" LT.

Proton and sodium 23 magnetic resonance imaging of human ocular tissues. A model study.

Clinical evaluation of uveal melanomas by magnetic resonance imaging (MRI) techniques depends on developing an understanding of the appearance of these tumors in magnetic resonance (MR) images. We have determined MR characteristics of uveal melanomas by proton (1H) and sodium 23 MRI of freshly enucleated human eyes at 1.5 tesla. The MR images were obtained using two-turn proton and 23Na surface coils, designed to both transmit and receive the radiofrequency signal. Proton MRI techniques included saturation recovery and spin echo; the gradient-recalled echo technique was used for 23Na MRI. Proton and 23Na MR images provide complementary information; contrast between intraocular tumors and vitreous, lens, or subretinal hemorrhage may be varied by using MR pulse sequences that emphasize tissues based on T1, T2, proton, or sodium density values. A combination of proton and 23Na MRI provides differentiation between normal ocular structures and intraocular tumors, as well as associated complications, such as retinal detachments and subretinal hemorrhages.

Phosphorus-31 nuclear magnetic resonance spectra characteristic of hexagonal and isotropic phospholipid phases generated from phosphatidylethanolamine in the bilayer phase.

31P nuclear magnetic resonance (NMR) spectroscopy is recognized as a technique which yields information concerning both the dynamics and organization of phospholipid molecules in biological membranes and phospholipid dispersions. In this theoretical paper, we examine the relationship between the conformation of the phospholipid molecule and the shape of the predicted 31P NMR spectrum. Using a simple model of rotation of the phospholipid molecule about its long axis, we show that it is possible to generate spectra previously considered typical of the bilayer (sigma parallel to less than sigma perpendicular), isotropic (sigma parallel to congruent to sigma perpendicular), and hexagonal II (sigma parallel to greater than sigma perpendicular) packing arrangements by simply changing the phospholipid head-group conformation while retaining the molecules in the bilayer phase.

Orientation and dynamics of phospholipid head groups in bilayers and membranes determined from 31P nuclear magnetic resonance chemical shielding tensors.

31P nuclear magnetic resonance (NMR) powder spectra have been used to determine the principal values of the chemical shielding tensors of phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, and phosphatidic acid. The shielding tensors in all cases were clearly nonaxial. The principal values for the monoester phosphatidic acid shielding tensor are -40, -4, and 48 ppm relative to 85% H3PO4. By contrast the diesters have values of -87, -25, and 119 ppm for phosphatidylcholine, -81, -20, and 105 ppm for phosphatidylethanolamine, and -80, -20, and 112 ppm for phosphatidylserine. This difference reflects the sensitivity of the 31P shielding tensor to chemical environment. Anisotropic motion of the molecules in lamellar dispersions of phospholipids caused an incomplete averaging of the shielding tensors resulting in partially narrowed spectra. Spectra of various phospholipid dispersions were recorded as a function of temperature and transitions observed at the gel-liquid crystalline phase transition temperatures. Using a reasonable set of initial conditions, it was shown that a simple model of molecular motion could successfully predict the observed spectra and their temperature dependences. The model includes rotations about the P-O(glycerol) bond and the molecular z axis and a wobble of the molecule about the bilayer normal. As the temperature increases, the wobble amplitude increases and the spectra narrow. A preliminary 31 P NMR spectrum of chick embryo fibroblasts is included. The similarities between this spectrum and those of the lamellar dispersions indicate that some of the predominant features are due to the phospholipid resonances.