Dissolved organic carbon during a spring diatom bloom in Lake Mossø, Denmark

The concentration and molecular weight composition of dissolved organic carbon (DOC) was measured during a spring diatom bloom in eutrophic Lake Mossø, Denmark. The concentration fluctuated between 5.2 and 7.2 mg Cl⁻¹. No relationship between DOC concentrations and phytoplankton biomass or primary production was observed. Diurnal variations of a magnitude similar to variations on a weekly basis were found. A decomposition experiment showed the labile fraction to be of a magnitude similar to the diurnal variation, i.e. 0.7 mg Cl⁻¹. By gel filtration (Sephadex G-50 and G-15) it was shown that 70–90% of the DOC pool was <700 daltons and probably <300 daltons. The labile fraction consisted of low molecular weight compounds.     

Concentration, fractionation and characterisation of soluble organic phosphorus in river water entering lough neagh

The mean concentration of soluble organic phosphorus in the 6 major rivers entering Lough Neagh from 1975 to 1979 was 38 μg P 1⁻¹. Soluble organic phosphorus constituted 16% of the total phosphorus input during this period. The chemical nature and availability for algal growth of soluble organic phosphorus is largely unknown. An adsorption-precipitation technique for concentrating soluble organic phosphorus from 1001. volumes of river water was developed using lanthanum. From the lanthanum-phosphorus precipitate acid-soluble and alkali-soluble concentrated solutions of organic phosphorus were obtained. 25% of the soluble organic phosphorus from 6 river samples was acid-soluble and 40% was subsequently alkali-soluble. These concentrated solutions were subjected to gel filtration chromatography on a preparative scale using Sephadex G-50 and G-75 when soluble organic phosphorus compounds were fractionated by molecular weight. Of the acid-soluble organic phosphorus 40% was of mol. wt > 10,000, 20% was of mol. wt between 10,000 and 1500 and 40% was of mol. wt < 1500. When the alkali-soluble organic phosphorus was fractionated 70% was of mol, wt > 50,000. Although the acid-soluble concentrates were yellow in colour and may have contained fulvic acids, further gel filtration chromatography of the acid-soluble organic phosphorus with mol. wt > 10,000 indicated that the organic phosphorus was itself coloourless. Alkali-soluble concentrates were red-brown in colour and may have contained humic acids. Sufficient of the alkali-soluble organic phosphorus with mol. wt > 50,000 was isolated by precipitation on acidification for elemental analyses and infrared spectroscopy. Elemental analyses (45.9%, C, 6.6% H, 5.7% N, 0.6% P) showed that the composition of the precipitated material was not identical to the composition of soil humic acids being lower in carbon and higher in hydrogen, nitrogen and phosphorus. Infrared absorption spectra were, however, characteristic of humic substances. Phosphorus may be an integral part of the humic acid structure or an organic phosphorus-metal-organic matter complex may exist. Iron was present in the structure but the phosphorus to iron ratio was not constant between river samples. Algal bioassays on the acid-soluble organic phosphorus with mol. wt > 10,000 and the alkali-soluble organic phosphorus with mol. wt > 50,000 showed that 10 and 32% respectively were available for growth under the conditions of the test.     

Dissolved organic matter and the dissipation of chlorine in estuarine water and seawater

Dissolved organic matter in estuarine water and seawater collected in the summers of 1980 and 1981 in the James River, Virginia and the mouth of Chesapeake Bay were separated into fractions according to their nominal molecular weights (NMW) by ultrafiltration. Estuarine waters contained higher concentrations of dissolved organic carbon (DOC). Among the fractions, between 66–89% of the DOC was found in the fraction with NMW below 10,000. Estuarine waters also had higher chlorine demands. At a dose of 5 mg l⁻¹, in 23 h, about 90% of the added chlorine disappeared in estuarine waters, whereas, in seawater, only 60–75% of the chlorine had dissipated. At least two-thirds of the chlorine demand occurred in the first 5 h. About 10–30% of the chlorine demand may be attributed to the fraction with NMW above 10,000. The remaining chlorine demand was distributed almost equally between the fractions with ranges of NMW of 1000–10,000 and below 1000. If reactivity is measured in terms of organic chlorine demand (ΔClo) per unit weight of DOC, the fractions with lower NMW (< 1000 and 1000–10,000) always had a higher reactivity towards chlorine. Between these two fractions, the one with NMW between 1000 and 10,000 exhibited higher reactivity more frequently. The highest reactivity found was 1.4 mg ΔClo mg⁻¹ DOC.     

The impact of combined sewer overflows on the dissolved oxygen concentration of a river

As described in the preceding paper by Harremoës (Harremoës, Water Res.16, 1093–1098, 1982) it is important to distinguish between removal and degradation of organic matter for non-steady-state discharges to rivers. These effects were investigated to determine the impact of combined sewer overflows on the dissolved oxygen concentration of a small river. Two different effects on the DO-concentration in the receiving river were observed during and after the passage of the bulk of combined sewage discharged at an existing outlet:

1. 1. An immediate effect caused mainly by degradation of the soluble BOD-fraction in the water body and by direct absorption and degradation of organic matter at the bottom.

2. 2. A delayed effect caused by degradation of adsorbed soluble, colloidal and fine particulate organic matter. After the passage of the bulk discharge a delayed effect on the DO-concentration in the river would be observed. This delayed effect lasted 12–24 hours after the discharge event.

Only 4% of the discharged organic matter was degraded during passage of the investigated stretch of the river, approx. 4 km. On the other hand about 35% of the discharged organic matter was removed by transfer to the bottom sediments. The rest was carried past the stretch of river investigated. This results in a rate of adsorption from the water phase of k = 9 m day⁻¹. The deposited organic matter was degraded with a first order reaction rate of K₄ = 0.75 day⁻¹.     

The chemistry of heavy metals in digested sewage sludge—II. Heavy metal complexation with soluble organic matter

Characterisitcs of copper-binding, in the soluble fraction of a digested sewage sludge, were determined using ion-selective electrodes. Results showed that ion exchange with protons is a principal component in copper binding and that the soluble organic matter has a cation exchange capacity of 8.86 m-equiv g⁻¹ at pH 6.5. A pH-dependent exchange constant, defined in terms of mole fractions of exchange components, describes the data in the pH range 2–8 and is independent of both pH and the extent of exchange in the range 5.5–8. Supplementary data include acid/base titration curves and simple kinetic measurements. Anion uptake is insignificant in the pH range 2.5–7. A model of the aqueous phase of a sewage sludge, containing soluble organic matter with only copper and protons as competing ions, predicts that at pH 7 over 99% of the copper present will be bound to the soluble organic matter.     

A comparison of the characteristics of soluble organic nitrogen in untreated and activated sludge treated wastewaters

Soluble organic materials containing nitrogen (SON) are present in effluents from activated sludge treatment of domestic wastewater, but little is known about the sources and characteristics of these materials. The objective of this research was to evaluate the characteristics of SON in untreated wastewaters and activated sludge effluents. Characterization techniques used included low microbial seed biodegradability, molecular weight distribution using gel filtration chromatography, removal by activated carbon and ion exchange, and analysis for free and combined amino acids. Activated sludge effluent SON was more refractory (40–50%; first-order decay rates for the remainder were about 0.014 day⁻¹ than SON in untreated wastewater (18–38%; decay rates for the remainder were 0.08–0.16 day⁻¹). SON produced biologically during treatment had decay rates (about 0.028 day⁻¹) similar to SON in municipal activated sludge effluents, and was from 20 to 100% refractory. Less than 10% of the SON in municipal activated sludge effluent consisted of free or combined amino acids. Approximately 15–30% appeared to nucleic acid degradation products. Fifty to 60% of the SON and SCOD had apparent molecular weights of less than 1800. Apparent molecular weight distributions of treated and untreated wastewaters were similar; however, the excess SON produced during activated sludge start-up contained considerably more SON with molecular weights greater than 1800. The 165–340 molecular weight fraction had a significantly higher SON to SCOD ratio than any other fraction for all wastewaters examined. Activated carbon adsorption efficiently removed SON (72 ± 9%) and SCOD (78 ± 6%) from treated and untreated wastewaters, and from biologically produced organics. Significantly more SON was removed by cationic exchange at pH 2.0 (33–56%) than by anionic exchange at pH 9.5 (10–24%) for all wastewaters tested. Cationic exchange at pH 2.0 selectively removed more biologically produced SON relative to SCOD.     

Applicability of light absorbance and fluorescence as measures of concentration and molecular size of dissolved organic carbon in humic Lake Tjeukemeer

Ultrafiltration results of humic Lake Tjeukemeer water demonstrated that light absorbance at 250 nm (E250), fluorescence (λ_ex = 365 nm; λ_em = 470 nm) (F), and concentration of dissolved organic carbon (DOC) vary with the molecular size (5–200 nm) of the dissolved organic matter. The ratio of the ultrafiltered organic fractions increased with decreasing molecular size of the DOC. However, under field conditions this ratio failed to predict molecular size distribution.These results limit the applicability of E250 and F as measures of molecular size and concentration of DOC. However, E250 measurements can be made rapidly and easily, and so are useful in estimating (30%) concentrations of DOC in humic waters.     

Experimental simulation of biodegradation in rivers: Oxygen, organic matter and biomass concentration changes

Dissolved oxygen (DO) and biochemical oxygen demand (BOD) concentration changes after an organic matter discharge into a river have been studied in the absence of oxygen transfer. According to these laboratory experiments, biodegradation of various organic compounds (glucose, glutamic acid, starch, ovalbumin and ethanol) in Seine river samples incubated at 15 30°C follow a biphasic behaviour. During a lag-phase of 10–20 h, DO decreases linearly (0.12 ppm h⁻¹ at 20°C), whereas BOD is constant. During a subsequent aerobic exponential phase, DO and BOD uptake are proportional and increase exponentially with time (0.13 h⁻¹ at 20°C). Using cell ATP as biomass indicator, the latter phase was shown to correspond to a cell division step. A kinetic model was developed for stimulating DO and BOD concentration changes after a waste water discharge at temperatures ranging between 15 and 30°C.     

Transformation of organic matter and bank filtration from a polluted stream

A case study of the examination of the changes of organic matter in a small, highly polluted stream and the adjacent alluvial aquifer is presented. The investigated stream was actually a collector of effluents from baker's yeast and pharmaceutical industries. The stream was characterized by a COD of several thousands of mg O₂ l⁻¹, most of which was biodegradable organic matter. Biodegradation processes took place in the surface water, with consequent oxygen depletion in the stream. The organic matter content of the river sediment was more than 10% of its dry weight. Bank filtration of organic substances was investigated in a number of observation wells at distances of 5–150 m from the river (under different hydrological conditions). The infiltration of organic matter from the polluted stream into the aquifer was found to be significant only at hydrological conditions where the water level exceeds the altitude of the stream bed. The organic matter present in groundwater samples was mainly a humic/fulvic type, and was not degraded during the 64 days of the laboratory biodegradation experiment.     

Metal interactions in contaminated freshwater sediments from the fly river floodplain,Papua New Guinea

Field data for sediment pH, Eh, sulphur and organic matter were analysed to determine their relationship with measured dissolved and particulate metals from sites in the Fly River affected by mine‐derived wastes. The above‐background concentrations of dissolved metals correspond to various concentration groups as demonstrated by copper for background (< 70 mg/kg), moderate (70–500mg/kg) and severe (> 500mg/kg), respectively. Dissolved Cu (r = 0.7431, p < 0.0005) and Mo (r = 0.7133,/> < 0.0005) were significantly correlated with their sediment component. Dissolved Al, Cd, Cu and Mo were positively correlated with sediment pH. Significant negative correlation between dissolved copper and sediment (SOM) organic matter (r = ‐0.3821, p < 0.05), and positive correlation with dissolved Al (r = 0.9358, p < 0.0005) suggest that dissolved Cu is present as a complex with either organic matter, Al/Fe oxyhydroxides, or oxyhydroxide‐organic matter colloids. Significant interrelations between dissolved Al, Cu and Mo with organic matter and the ratio of Fe/SOM also suggests that sediment physico‐chemical characteristics are important in the processes occurring in the Fly River floodplain sediments. These processes appear to be responsible for the significantly increased metal concentration in the water column.     

Binding capacity of wastewater discharge to seawater

The copper binding capacity was used to follow physico-chemical changes in the mixing of sewage effluent and seawater. In laboratory experiments dilute aliquots of filtered and unfiltered effluents were mixed with artificial seawater to give saline concentrations of between 0 and 40‰. The copper binding capacity of the filtered sample decreased rapidly from 22.8 to 0 μg l⁻¹ in the salinity range 5–10‰. The difference between the unfiltered and filtered binding capacity, defined as the adsorption capacity, varied from 28.5 to 0 μg l⁻¹ in the salinity range 15–22‰. These results were interpreted in terms of destabilisation of copper associations with humates, colloids and particulate matter with increasing salinity. The behaviour of unfiltered binding capacity in the effluent plume was measured and the results showed reasonable agreement with results from the laboratory experiments.     

Weak and strong acids in the surface waters of the tovdal region in S. Norway

The concentrations of weak and strong acids in surface waters of the Tovdal region of southern Norway were measured during a spring snow-melt period. The determinations were made by the pH titration method due to Gran. The strong acid concentrations in Tovdal river water varied between 3 and 11 μeq 1⁻¹, while the weak acid concentrations were between 62 and 106 μeq 1⁻¹ and the contribution of the weak acids to the hydrogen ion concentration ranged between 10 and 60%. The pH of the river water varied from 4.9 to 5.0 and in the absence of excess strong acid, the weak acids would have produced a pH of 5.2–5.3. The concentration of weak acids and their contribution to the hydrogen ion concentration were least during the period of most rapid thaw.No direct evidence of the nature of the weak acids was obtained, but routine chemical analysis data suggested that inorganic species derived from aluminium and silicon accounted for 40–60 μeq 1⁻¹, while 20–50 μeq 1⁻¹ were attributable to humic and fulvic acids. The titration characteristics of the weak acids could be approximated closely by a polybasic acid with a first ionization constant in the range 10⁻⁶ to 5 × 10⁻⁷ and less well defined weaker ionizations.Measurements on old snow containing coniferous tree litter and on melt water from a rocky barren contained weak acid concentrations comparable to the riverwater, indicating that only slight contact with vegetable matter or the ground is required to obtain significant concentrations of weak acids.     

Molecular weight distributions in activated sludge effluents

Bench scale activated sludge reactors with a solids retention time of 9 days were operated at all combinations of two levels of pH, dissolved oxygen (DO) concentration and feed type (pH 6 and 8; DO 1 and 7 mgl⁻¹; simple and complex feed). Long-term composite samples were collected and adjusted to neutral pH and equal concentrations of alkalinity and ammonia nitrogen. The molecular weight distributions of the soluble organic carbon (SOC) in the samples were determined by ultrafiltration through membranes with nominal rejection values of 1000, 10,000, 25,000 and 100,000. The distributions were generally bimodal with the bulk of the SOC in the largest and smallest fractions. Following ozonation to a residual of 0.30–0.35 mg 1⁻¹ after 5 min contact, the distributions were shifted so that more of the SOC appeared in the lowest molecular weight fraction although significant amounts remained in the other fractions. When samples were breakpoint chlorinated to a residual of 5–10 mg l⁻¹ free available chlorine after 2 h contact, very little high molecular weight material remained and almost all of the SOC appeared in the low molecular weight fraction. By using ³⁶Cl during breakpoint chlorination it was also possible to evaluate the distribution of organically bound chlorine among the molecular weight fractions and this revealed that the bulk of it was associated with organics having molecular weight less than 1000.     

Partitioning of copper onto suspended particulate matter in river waters

Suspended particles and river water from the Susquehanna River, White Clay Creek and the Delaware River were collected to experimentally study the partitioning of copper. The effects of many factors that may influence the partitioning coefficient (Kd) including pH, total suspended solids (TSS), total copper concentration ([Cu]T), dissolved organic matter (DOM), particulate organic matter (POM), hardness, and ionic strength were investigated by performing batch adsorption experiments. The results implied that organic matter binding sites in both the aqueous and solid phases play the most important role in controlling copper partitioning. Other major factors governing the partitioning are pH and TSS. Kd increases with pH in the pH range 3-8. TSS increases caused decreases in Kd values, which may be attributed to the decrease in the quantity of available binding sites caused by interparticle interactions, rather than by the redistribution of organic matter between solid and solution phases with the variation of TSS. Kd decreases slightly when total Cu concentration increases; however, Kd can be considered to be independent of Cu concentration when TSS is high. The effects of calcium competition and ionic strength on partitioning are small.     

Effects of molecular weight of natural organic matter on cadmium mobility in soil environments and its carbon isotope characteristics

We investigated the role of natural organic matter in cadmium mobility in soil environments. We collected the dissolved organic matter from two different types of natural waters: pond surface water, which is oxic, and deep anoxic groundwater. The collected organic matter was fractionated into four groups with molecular weights (unit: Da (Daltons)) of <1 x 10(3), 1-10 x 10(3), 10-100 x 10(3), and >100 x 10(3). The organic matter source was land plants, based on the carbon isotope ratios (delta(13)C/(12)C). The organic matter in surface water originated from presently growing land plants, based on (14)C dating, but the organic matter in deep groundwater originated from land plants that grew approximately 4000 years ago. However, some carbon was supplied by the high-molecular-weight fraction of humic substances in soil or sediments. Cadmium interacted in a system of siliceous sand, fractionated organic matter, and water. The lowest molecular weight fraction of organic matter (<1 x 10(3)) bound more cadmium than did the higher molecular weight fractions. Organic matter in deep groundwater was more strongly bound to cadmium than was organic matter in surface water. The binding behaviours of organic matter with cadmium depended on concentration, age, molecular weight, and degradation conditions of the organic matter in natural waters. Consequently, the dissolved, low-molecular-weight fraction in organic matter strongly influences cadmium migration and mobility in the environment.     

Indigenous bacterial inocula for measuring the biodegradable dissolved organic carbon (BDOC) in waters

A collaborative study was carried out in order to compare the biodegradable dissolved organic carbon (BDOC) analysis using different indigenous mixed bacterial populations as inocula. The variables examined in the study were the laboratories, the water samples (raw, ozonated or finished water), the origin of the inoculum: suspended bacteria from river waters and attached bacteria onto sand taken from drinking water treatment plants. Variances associated with individual components of this study were isolated: the laboratories represented the highest source of variation (56.6–70.7%), while the inoculum origin contribution to the increase of variance is lower (12–26%). As a conclusion, indigenous mixed bacterial populations (suspended or attached bacteria) may be used reliably as standard inocula in BDOC determinations without introducing excessive variability.     

Chloroform production from the chlorination of aquatic humic material: The effect of molecular weight, environment and season

Humic material from various aqueous environments and from laboratory microbial cultures was segregated into humic and fulvic acid fractions and then each fraction was separated into eight molecular weight ranges by ultrafiltration. The fractionated material was then chlorinated in aqueous solution and the amount of chloroform produced was measured. Chloroform concentration per unit weight humic material passed through a maximum at molecular weight about 20,000–30,000 for the fulvic acids, whereas the CHCl₃ concentration decreased with increasing molecular weight above 20,000–30,000 for the humic acids. Only minor fluctuations in chloroform concentrations were apparent for samples from various aqueous environments (lake, river, stream, swamp, microbial) and for samples from a single environment obtained during different seasons of the year. Based on the total amount of material isolated from the original samples and the chloroform production per unit weight, the major chloroform precursors in aquatic humic material were the low molecular weight (< 30,000) fulvic acid fractions. Unfortunately, because of their low molecular weight and high surface activity, these fractions will probably prove to be the most difficult to remove by standard water treatment processes.     

Isolation and characterization of polymeric organic materials in a polluted river water

Organic matter was isolated from water samples from a river mainly polluted by domestic sewage by using Amberlite XAD-2 resin after being acidified to pH 2. The amount of the isolated organic matter comprises about 40% of the total dissolved organic matter. Measurements of elementary composition, molecular weight distribution, u.v. and i.r. spectra and GC/MS analysis of alkaline potassium permanganate oxidation products were performed for the isolated matter. The results indicate that more than a half of the isolated organic matter have apparent molecular weights higher than 5000. The chemical oxidation of the isolated organic matter produced (a) aliphatic monocarboxylic acids (C₆---C₂₄), (b) aliphatic dicarboxylic acids (C₃-C₁₂) and (c) benzene-mono-di-, tri- and tetracarboxylic acids: the latter two groups (b and c) are most abundant. The relative amounts of those three groups seem to be explained in terms of the nature and degree of pollution.     

Cadmium in the Rhône river

The distribution of cadmium in the Rhône river was studied using differential pulse anodic stripping voltametry with a static mercury drop electrode. For 11 potentially contaminated river stations, the Cd in true solution averaged 39 ± 23 ng kg⁻¹, adsorbed on suspended matter was 19 ± 22 ng kg⁻¹ (liquid phase) and suspended matter content was 2.4 ± 1.5 mg kg⁻¹ (solid phase), equivalent to 40 ± 24, 22 ± 24 and 38 ± 31%, respectively, of the total carried under these conditions. For sediments the mean Cd content was 0.9 ± 0.6 mg kg⁻¹. The water values are low by world standards, even though sampling was biased towards sites potentially contaminated. This could be partially due to the unusual water pH of 7.8–8.5.     

Caracterisation de la matiere organique dissoute presente dans les eaux en cours d'affinage: Influence des traitements appliques et du climat

Dissolved organic matter in treated surface waters (clarified, possibly ozonized, then GAC-filtered, Fig. 1), is fractionated by ultrafiltration into five molecular classes with MW < 300, 300–1000, 1000–5000, 5000–10000 or > 10,000. Dissolved organic carbon (DOC), oxidizability by KMnO₄ in hot alkaline medium and u.v. absorbances at 240, 254, 280, 300 nm are measured. Fourteen series of samples, distributed on an annual biological cycle are analysed (Figs 2 and 3); multivariate statistical analyses are performed.By PCA (principal component analysis), variations in water supplying the activated carbon units appear to depend for 47% on ozonation and temperature; but river flow rate and quantity of flocculant added are no longer responsible for such variations (Fig. 4). Three groups of water appear (Fig. 5), according to the applied ozone level (zero, medium, high); among the medium ozonized waters, the cold ones differ from temperate ones.Ozonation diminishes molecular size of compounds (Table 1): three major classes with MW < 5000 are present in non- or medium-ozonized waters, but only two, with MW < 1000, remain in highly ozonized waters. This treatment destroys MW > 10,000 and even 1000–5000 ones and yields MW < 300 products; it also minimizes u.v. absorbances and oxidizability. Seasonal variations occur in DOC content of medium ozonized waters, with maxima values in winter or spring and minima in summer or autumn (Fig. 6): occurrence of MW < 300 compounds follows that of DOC, but the presence of 5000–10000 ones is minimal in winter.Quality of GAC-filtered waters varies by 19% with temperature (Fig. 7); ozonation effects are minimized: only previously highly ozonized waters distinguished themselves from the others (Fig. 8). Waters, non or medium ozonized before GAC-filtration, are divided into cold, temperate and warm waters. One, two or three major classes of compounds with MW < 5000, remain in GAC-filtered waters, according to the ozone level applied previously. This filtration reduces DOC by 17%, decreases u.v. absorbances and oxidizability and gives water with the same 0.30 mg O₂ mg⁻¹ C ratio (Table 2): MW 1000–5000 class is much less oxidizable after ozonation-GAC filtration but, on the other hand, MW < 300 class appears rather less oxidizable without ozonation before biological filtration. DOC content in effluent follows that in influent (Fig. 9), but variations are less marked. Total efficiency of the filtration increases with temperature, but behaviour of compounds differs from one class to another: MW 300–1000 and 5000–10000 classes are the most affected; MW 1000–5000 is not really modified. Elimination of MW < 300 or 5000–10000 compounds depends on temperature and may be due to biological phenomena, a but that of 1000–5000 and > 10,000 classes, independent of this parameter, may be related to adsorption mechanisms.