Monika Takács

Total luminescence spectral characteristics of natural organic matter (NOM) size fractions as defined by ultrafiltration and high performance size exclusion chromatography (HPSEC)

Abstract Natural organic matter (NOM) was isolated by reverse osmosis from two surface waters of differing climatic regimes and organic source material, in Norway and Georgia, USA. The NOM was separated into methodologically defined size fractions by ultrafiltration and high performance size exclusion chromatographic (HPSEC) techniques and the fractions were analyzed with UV-visible and total luminescence spectral techniques. While some systematic variation was observed, NOM from both systems had similar UV specific absorbance values and both had higher 254 nm specific absorbances in the larger molecular size fractions. Similarly, NOM from both systems had fluorescence spectral peaks in the regions of approximately λ ex / λ em =225/425 nm and λ ex / λ em =335/445 nm, consistent with spectra of humic substances in freshwater environments. Agreement of these measurements in two significantly different environments and with previously published literature indicates that freshwater NOM is very consistent relative to its absorbance and fluorescence chromophores, despite differences in the origin of the material and the early diagenetic processes to which plant material may be exposed.

NATURE OF NATURAL ORGANIC MATTER (NOM) IN ACIDIFIED AND LIMED SURFACE WATERS

Natural organic matter (NOM) was isolated by reverse osmosis (RO) from the two inlet brooks and the outlet of Lake Terjevann with estimated recoveries of 85-90%. The lake has been receiving liming treatments since 1980 due to the acidic drainage from the catchments. High- performance size exclusion chromatography (HPSEC) analyses of the RO samples and of ultrafiltered fractions indicate that there are five main size fractions of carbon with molecular weights between 410- 1170 Da in all three samples. However, the molecular weight distributions diAer significantly in that the outlet sample have lower proportions of larger molecular weight NOM than do the inlets. Studies of spectral absorption coeAcients at 254 nm support this molecular size distribution. Absorption coeAcients of the samples at both 254 and 410 nm decrease with decreasing molecular weight so that the ratio E2/E4 increases with decreasing molecular weight. This trend appears independent of pH changes and especially eAects the absorption coeAcients of the higher molecular weight NOM. Studies of C:N ratios of the RO samples and of ultrafiltered fractions indicate that the outlet RO sample and that the lower molecular weight NOM are enriched in nitrogen. Supported by studies of spectral absorption coeAcients and C:N ratios of the total RO samples and ultrafiltered fractions and eAects of pH changes on the ultrafiltered fractions, it is hypothesized that in-lake processes are removing larger molecular weight NOM. This is possibly an eAect of the liming which increase pH and calcium(II) concentrations in the lake water coinciding with hydrolysis and precipitation of aluminium(III) and iron(III). # 1999 Elsevier Science Ltd. All rights reserved

Characterization of natural organic matter from eight Norwegian surface waters: Proton and copper binding

Abstract As a part of the International NOM-Typing Project, proton and copper binding studies were conducted on ultrafiltered (>1000 dal.) and dialysed (>100 dal.) natural organic matter (NOM) samples from eight Norwegian Lakes. The NOM samples were similar with respect to proton and copper binding, although minor differences were observed among the samples of different origin. Slight variations occurred for seasonal changes and lime additions. The proton binding pK a values grouped in three distinct classes: pK a 1 = 4.20–4.28; pK a 2 = 6.61–6.87; and pK a 3 = 9.27–9.8. The average total proton binding site concentration of the NOM samples was: 12.7 meq/g total organic carbon (TOC). Two binding sites were established for copper with average log K1 = 4.84 and log K2 = 7.17. The average site concentration for samples isolated by reverse osmosis (RO) was 0.56 μmol/mg C. Copper binding characteristics appear to be influenced by the method of sample isolation. For NOM isolated by low pressure evaporation (evap), binding site concentrations are smaller, conditional stability constants are higher, variability of the copper complexation capacity is smaller, and correlation with elemental composition (C, N, H) is better than in the case of NOM isolated by RO.

Characterization of natural organic matter from eight Norwegian surface waters: The effect of ash on molecular size distributions and CHN content

Abstract Natural organic matter (NOM) was isolated by reverse osmosis (RO) from eight surface waters in southern Norway. The freeze-dried samples were reconstituted in deionized water and part of the sample was dialysed against HCl. Samples of both the dialysed and non-dialysed materials were then ultrafiltered to give fractions: >50 000 dal., 10 000 dal. and

Ultraviolet-Visible and Fluorescence Spectral Evidence of Natural Organic Matter (NOM) Changes along an Estuarine Salinity Gradient

A transect of the St Marys River estuary from above the point of maximum salt wedge penetration to coastal salinities was conducted in July 1999. None of the parameters examined—dissolved organic carbon (DOC) content, UV light absorbance at 254 nm, and Total Luminescence spectra—follow the rule of conservative mixing. The characteristics of the different molecular size fractions of the St Marys River natural organic matter (NOM), as well as the results of a laboratory mixing experiment, provided evidence that loss of larger molecular size compounds from riverine NOM may occur by coagulation at salinities up to 10. An apparent gain of carbon in the lower estuary was attributed to exports from abundant coastal marshes in this area.The Total Luminescence spectra of the riverine NOM can be described by two peaks, centered respectively around 340/445 nm, and 230/430 nm Excitation/Emission Wavelength Pair (EEWP), which are characteristic of humic materials of aquatic origin. The samples from the high salinity stations exhibit peaks at lower emission wavelength EEWP 320/424 nm, which can be considered as marine humic-like material. The presence of amino acid-tryptophan like peaks were observed, with EEWP 300/350 nm in some of the high salinity samples. This peak was of high relative fluorescence intensity. It is hypothesized that the intense biological activity of the salt marsh and near coastal area is responsible for the carbon addition as well as the appearance of the highly fluorescence amino acid-protein like material.

Influence of IHSS Standard and Reference Materials on Copper and Mercury Toxicity to Vibrio fischeri

The reduction in light emission of the marine bacterium Vibrio fischeri used in the standard Microtox® bioassay was measured for the metals copper and mercury. The concentration at which the light emission was reduced by 50% (EC50) was determined to be (3.43 ± 0.83) μmol/L for Cu2+ and (0.66 ± 0.01) μmol/L for Hg2+. The reduction of the toxicity of these metals by humic and fulvic acids were studied using IHSS Standard and Reference Materials. Copper toxicity was reduced 17...20% by the soil and peat fulvic acids and 9...20% by the aquatic fulvic acids. While there appeared to be little difference in the reduction of Cu toxicity by fulvic acids from soils, peats, or aquatic systems, Hg toxicity was reduced 3.6...7.3% by the soils and peats, while aquatic fulvic acids reduced Hg toxicity 14...16%. Soil fulvic acids appear to have significantly less capacity to reduce Hg toxicity than Cu toxicity. Humic acids had much higher reductions of Cu toxicity (44...124%) compared to the fulvic acids, with little difference between aquatic and soil or peat humic acids, 44...124% and 67...100%, respectively. However, humic and fulvic acids, regardless of origin, had approximately the same effect on Hg toxicity with 3.5...16% reduction by fulvic acids and 8...20% reduction by humic acids. Unlike the fulvic acids, no clear trend was observed relative to origin of the humic acids. There was no correlation between percent reduction of Cu or Hg toxicity by the organic compounds and copper binding capacity (CuBC), C/N ratio, or carboxyl content of the materials. Examination of natural organic matter (NOM) isolated by reverse osmosis techniques from three water sources had reductions of both Cu and Hg toxicity that were most similar to the Suwannee River and Nordic fulvic acids. Der Einfluss von IHSS-Standard- und Bezugssubstanzen auf die Toxizitat von Kupfer und Quecksilber gegenuber Vibrio fischeri Untersucht wurde die Hemmung der Leuchtintensitat des im Standard-Microtox®-Biotest eingesetzten marinen Bakteriums Vibrio fischeri durch die Metalle Kupfer und Quecksilber. Die Konzentration, bei der die Lichtemission um die Halfte reduziert ist (EC50), wurde fur Kupfer zu (3.43 ± 0.83) μmol/L und fur Quecksilber zu (0.66 ± 0.01) μmol/L bestimmt. Die Verminderung der Toxizitat dieser Metalle durch Huminsauren und Fulvinsauren wurde an IHSS-Standard- und Bezugssubstanzen untersucht. Die Toxizitat des Kupfers wurde durch Fulvinsauren aus Boden und Torf um 17...20% und durch aquatische Fulvinsauren um 9...20% reduziert. Fur Kupfer scheint im Hinblick auf die detoxifizierende Wirkung zwischen bodenburtigen, torfstammigen und aquatischen Fulvinsauren nur ein geringer Unterschied zu bestehen. Die Toxizitat des Quecksilbers hingegen wurde durch Boden- und Torf-Fulvinsauren um 3.6...7.3% vermindert, durch aquatische Fulvinsauren jedoch um 14...16%. Aus Boden isolierte Fulvinsauren haben offensichtlich auf Quecksilber eine signifikant geringere detoxifizierende Wirkung als auf Kupfer. Huminsauren hatten im Vergleich zu Fulvinsauren auf die Kupfertoxizitat eine viel starker vermindernde Wirkung (44...124%), wobei zwischen aquatischen Huminsauren (44...124%) und Huminsauren aus Boden und Torf (67...100%) nur ein geringer Unterschied bestand. Auf Quecksilber hatten Fulvinsauren mit 3.5...16% bzw. Huminsauren mit 8...20% ungeachtet ihrer Herkunft ungefahr die gleiche detoxifizierende Wirkung. Anders als bei den Fulvinsauren zeigt sich hier kein klarer Trend, der mit der Herkunft der Huminsauren in Verbindung gebracht werden konnte.Es wurde keine Korrelation zwischen der auf den Kohlenstoffgehalt der Probe bezogenen detoxifizierenden Wirkung und den Eigenschaften Kupferbindungskapazitat (CuBC), C/N-Verhaltnis oder Carboxlygruppengehalt der organischen Substanz gefunden. Aus drei verschiedenen Gewassern durch Umkehrosmose isolierte naturliche organische Wasserinhaltsstoffe (NOM) entsprachen in ihrer detoxifizierenden Wirkung auf Cu und Hg in etwa den Fulvinsauren Suwannee River Fulvic Acid und Nordic Fulvic Acid.