Water Organic Carbon Research Articles

Field testing of equilibrium passive samplers to determine freely dissolved native polycyclic aromatic hydrocarbon concentrations

Equilibrium passive samplers are promising tools to determine freely dissolved aqueous concentrations (C(W,free)) of hydrophobic organic compounds. Their use in the field, however, remains a challenge. In the present study on native polycyclic aromatic hydrocarbons (PAHs) in Oslo Harbor, Norway, two different passive sampler materials, polyoxymethylene (POM; thickness, 55 microm [POM-55] and 500 microm [POM-500]) and polydimethylsiloxane (PDMS; thickness, 200 microm), were used to determine in the laboratory C(W,free) in sediment pore water (C(PW,free)), and the suitability of five passive samplers for determination of C(W,free) in overlying surface water was tested under field conditions. For laboratory determinations of C(PW,free), both POM-55 and PDMS turned out to be suitable. In the field, the shortest equilibrium times (approximately one month) were observed for POM-55 and PDMS (thickness, 28 microm) coatings on solid-phase microextraction fibers, with PDMS tubing as a good alternative. Low-density polyethylene (thickness, 100 microm) and POM-500 did not reach equilibrium within 119 d in the field. Realistic values were obtained for dissolved organic carbon-water partition coefficients in the field (approximately one log unit under log K(OW)), which strengthened the conclusion that equilibrium was established in field-exposed passive samplers. At all four stations, chemical activity ratios between pore water and overlying water were greater than one for all PAHs, indicating that the sediment was a PAH diffusion source and that sediment remediation may be an appropriate treatment for PAH contamination in Oslo Harbor.

Measured partition coefficients for parent and alkyl polycyclic aromatic hydrocarbons in 114 historically contaminated sediments: Part 2. Testing the KOCKBC two carbon–type model

Polycyclic aromatic hydrocarbon (PAH) desorption partition coefficients between black carbon and water (K(BC)) were determined using 114 historically contaminated and background sediments from eight different rural and urban waterways. Black carbon was measured after oxidation at 375 degrees C for 24 h. Organic carbon-water partition coefficients (K(OC)) required for the calculation of K(BC) values were determined for two- to six-ring parent and C1- to C4-alkyl PAHs based on the lower range of measured K(OC) values from the same sediments and comparisons to literature K(OC) values. Approximately 2,050 log K(BC) values were determined on sediments having a range of total organic carbon from 0.3 to 42% by weight, black carbon from 0.1 to 40% by weight, and total PAH concentrations (U.S. Environmental Protection Agency 16 parent PAHs) from 0.2 to 8,600 microg/g. Contrary to expectations, PAH partitioning was not better explained using the combined K(OC) and K(BC) models rather than the simple K(OC) model (i.e., K(BC) values for each individual PAH ranged nearly three orders of magnitude). No effect of PAH concentration on measured K(BC) values was apparent. Values of K(BC) also showed no trends with total organic carbon, black carbon, or the presence or absence of a non- aqueous phase liquid. Multiple linear regression analysis with K(OC) and K(BC) as fitted values also failed to explain the variance of the experimental data (r(2) values typically less than 0.20, and standard errors greater than two orders of magnitude). These results demonstrate that models of PAH partitioning that account for different carbon types, although useful for understanding partitioning mechanisms, cannot yet be used to accurately predict PAH partitioning from historically contaminated sediments.

Impact on water distribution system biofilm densities from reverse osmosis membrane treatment of supply water

The quality of potable water is such that the concentration of nutrients available for growth of microorganisms within distribution systems is limited. In such systems carbon is often the growth limiting nutrient. Research conducted in the Netherlands has indicated that low levels (<10 μg/L) of available organic carbon in water is sufficient to maintain an actively growing population of heterotrophic, or organic carbon utilizing, bacteria in aquatic systems. However, the ability of commercially available and cost effective technologies to achieve such low concentrations of assimilable organic carbon in full-scale water systems is doubtful. Reverse osmosis (RO) systems have been used for many years to effectively remove contaminants from source waters. We challenged a water distribution system simulator (DSS) with water from a municipal system and water that was treated using an RO system under two concentrations of residual free chlorine to evaluate the effect of this disinfectant on biofilms in contact with low nutrient water. Our results showed that biofilm densities in the DSS carrying low nutrient RO treated water were lower than biofilm densities taken from the DSS when it carried water directly obtained from a municipal system.Key words: water distribution systems, reverse osmosis, biofilms, heterotrophic plate count, HPC, chlorine, assimilable organic carbon.

A globally applicable location-specific screening model for assessing the relative risk of pesticide leaching

A screening model of pesticide leaching loss is described which forms part of a multi-criteria risk-based indicator system called PRoMPT (Pesticide Risk Management and Profiling Tool). The leaching model evaluates pesticide fate in soil for any application rate and time of application (including multiple applications), for any land-based location in the world. It considers a generic evaluative environment with fixed dimensions and soil properties. The soil profile is conceptualised as a number of discrete layers. Equilibrium partitioning between adsorbed and dissolved chemical (based on the organic carbon-water partition coefficient [K(OC)]) is assumed in each time step, in each layer. Non-leaching losses are described using first order kinetics. Drainage is assumed to be uniform throughout the soil profile but varies temporally. The drainage rate, which can be augmented by evapotranspiration-adjusted irrigation, is derived from long-term mean monthly water balance model calculations performed for 30 arc-minute grid cells across the entire ice-free land surface of the earth. Although, such predictions are approximate, they do capture the seasonality and relative magnitude of drainage and allow the model to be applied anywhere, without the need for extensive data compilation. PRoMPT predictions are shown to be consistent with those made by more sophisticated models (PRZM, PELMO and PEARL) for the FOCUS groundwater scenarios.

WATER COLUMN CONCENTRATIONS AND PARTITIONING OF POLYBROMINATED DIPHENYL ETHERS IN THE NEW YORK/NEW JERSEY HARBOR, USA

Despite the emerging concern regarding polybrominated diphenyl ethers (BDEs), very few measurements of BDE concentrations in ambient water have been published. In the present study, BDEs were measured in water samples from the New York/New Jersey Harbor (USA). Samples were taken in Raritan Bay west of Sandy Hook during four intensive sampling campaigns in 2000 and 2001. Congeners 17, 47, 99, 100, 153, 154, 183, and 209 were detected. Total BDE (SigmaBDE) concentrations (average +/- standard deviation) were 175 +/- 75 ng/g in the particle phase and 110 +/- 72 pg/L in the apparent dissolved phase. The deca-congener, BDE 209, constituted 85 and 9% of SigmaBDEs in the particle and apparent dissolved phases, respectively. The SigmaBDE levels are significantly higher than those measured in Lake Ontario, USA, and in The Netherlands, but they are similar to concentrations measured in Lake Michigan and San Francisco Bay (both USA). Calculated values of the organic carbon-water partition coefficient (K(OC)) were strongly correlated with literature values of the octanol-water partition coefficient (K(OW)). The data suggest that sorption of BDEs to colloids is important in this system, although quantifying the extent of colloid sorption is difficult.

Flow-injection analysis for the determination of total inorganic carbon and total organic carbon in water using the H2O2–luminol–uranine chemiluminescent reaction

In the presence of carbonate and uranine, the chemiluminescent intensity from the reaction of luminol with hydrogen peroxide was dramatically enhanced in a basic medium. Based on this fact and coupled with the technique of flow-injection analysis, a highly sensitive method was developed for the determination of carbonate with a wide linear range. The method provided the determination of carbonate with a wide linear range of 1.0 x 10(-10)-5.0 x 10(-6) mol L(-1) and a low detection limit (S/N = 3) of carbonate of 1.2 x 10(-11) mol L(-1). The average relative standard deviation for 1.0 x 10(-9)-9.0 x 10(-7) mol L(-1) of carbonate was 3.7% (n = 11). Combined with the wet oxidation of potassium persulfate, the method was applied to the simultaneous determination of total inorganic carbon (TIC) and total organic carbon (TOC) in water. The linear ranges for TIC and TOC were 1.2 x 10(-6)-6.0 x 10(-2) mg L(-1) and 0.08-30 mg L(-1) carbon, respectively. Recoveries of 97.4-106.4% for TIC and 96.0-98.5% for TOC were obtained by adding 5 or 50 mg L(-1) of carbon to the water samples. The relative standard deviations (RSDs) were 2.6-4.8% for TIC and 4.6-6.6% for TOC (n = 5). The mechanism of the chemiluminescent reaction was also explored and a reasonable explanation about chemical energy transfer from luminol to uranine was proposed.

Satellite estimation of marine particulate organic carbon in waters dominated by different phytoplankton taxa

The relationship between in situ remote sensing reflectance (Rrs) and particulate organic carbon (POC) was assessed for the continental shelf waters of the southwestern Ross Sea, Antarctica. This sector of the Southern Ocean supports two distinct phytoplankton communities, one dominated by diatoms and the other dominated by the haptophyte Phaeocystis antarctica. In both communities, Rrs exhibited a statistically significant (p < 0.05) positive linear correlation with POC concentration, although the slope of the regression was over twofold higher in waters dominated by P. antarctica. These distinct relationships between POC and Rrs are likely due to differences in the cell size and composition, as well as detrital degradation products, of the dominant taxa within each of these phytoplankton communities. Taxon‐specific POC‐Rrs relationships were translated into a bio‐optical algorithm for estimation of surface POC concentration from remotely sensed estimates of Rrs. Applying this algorithm to satellite‐derived Rrs from the Ross Sea, where distributions of P. antarctica and diatoms are reasonably well known, yields distributions of POC and POC:chlorophyll ratios that are in good agreement with field measurements. Performance of the algorithm can be improved by in situ characterization of the detrital contribution to total particle backscatter.

Partition of Volatile Organic Compounds in Activated Sludge and Wastewater

The Henry’s law constant is important in the gas-liquid mass transfer process. Apparent dimensionless Henry’s law constant, or the gas-liquid partition coefficient (K’ H), for both hydrophilic (methanol, isopropyl alcohol, and acetone) and hydrophobic (toluene and p-xylene) organic compounds in deionized (DI) water, a wastewater with a maximum total dissolved organic carbon (DOC) content of 700 mg/L, and DI water mixed with a maximum activated sludge suspended solid (SS) concentration of 40,000 mg/L were measured using the single equilibrium technique at 293 K. Experimental results demonstrate that the K’ H of any of the test volatile organic compounds varied among three situations. First, the K’H of the hydrophilic compounds in mixed liquor with the maximum SS concentration was 9–21% higher than those in DI water. Second, those for toluene and p-xylene were 77% and 93% lower, respectively, in the mixed liquor with the maximum SS concentration. Third, the K’H values of all of the test compounds in the wastewater were only 10% lower than those in DI water. A model was developed to relate K’ H with wastewater DOC and the SS concentration in the activated sludge using an organic carbon-water partition coefficient and activated sludge-water partition coefficient as model parameters. The model was verified and model parameters for test compounds estimated.

Use of Low-Frequency Sonication for the Production of Biodegradable Dissolved Organic Carbon in Water

Low-frequency sonication (20 kHz) was used to increase biodegradable dissolved organic carbon (BDOC) in tap water, which received only chlorination, fluoridation, and pH adjustment for treatment. Effects of sonication time, power, and reactor temperature on the BDOC formation were investigated. When the water samples were sonicated, BDOC increases up to 2.38 mg/L were observed. BDOC did not necessarily increase with time of sonication, and the power and time of sonication as well as the characteristics of the samples influenced BDOC production. Results further indicated that the reactor temperature did not affect the BDOC formation. Maximum BDOC formation was obtained at the sonication time of 10 and 30 min. The power of 275 watts was optimal. Data presented in this study are preliminary and more investigations on the optimization of sonication for BDOC enhancement are recommended for future work.

Organic carbon and pesticide pollution in a tropical coastal lagoon-estuarine system in Northwest Mexico

The Altata-Ensenada del Pabellon system (~360 km²) comprises three inland lagoons, a coastal lagoon, and a bay. Inland is an important irrigation district (~330,000 ha). Agricultural drains and two sugar cane mills wastewaters are discharged into the system. Particulate organic carbon in water varied from 0.5 to 6.1 mg C/l. Organic carbon mean concentration (mg C/g dw) in sediments was 22.6 in the bay, 92.6 in the coastal lagoon, and 179.6 in the inland lagoons. Organochlorine pesticides (OCs) mean total concentration (ng/g dw) was 59.13 for inland lagoons, 35.60 for coastal lagoon, and 9.08 for the bay. A significant correlation was found between organic matter and OCs.

Henry’s Law Constant Variations of Volatile Organic Compounds in Wastewater and Activated Sludge

Henry’s law constant is an important equilibrium factor in the mass transfer process of volatile organic compounds (VOCs). A single equilibration technique (SET) was adopted to measure the air-water dimensionless (KH) and the dimensionless apparent (K’H) of Henry’s law constant in an air-wastewater system and air-activated sludge for VOCs at 298 K. Hydrophilic VOCs (methanol, isopropanol and acetone) and hydrophobic VOCs (toluene and p-xylene) were used as target compounds. Deionized (DI) water, (DI-water diluted and a pasteurized wastewater (abbreviated as wastewater) with a maximum dissolved total organic carbon (TOC) content of 700 mg/L) and DI-water diluted and pasteurized activated sludge (abbreviated as mixed liquor) with a maximum suspended solid concentration of 40,000 mg/L were used as liquids. K’H of the target hydrophilic compounds in the mixed liquor with a maximum-suspended solid concentration were 8.9 to 19.9% higher than those in DI water. Those for toluene and p-xylene decreased up to 70.8 and 88.3% in the mixed liquor, respectively. K’H of all the test compounds in the wastewater was only 1 to 11% smaller than those in DI water. A model was proposed for correlating K’H with wastewater TOC and activated sludge concentration using an organic carbon-water partition coefficient (KOC) and activated sludge-water partition coefficient (KP) as model parameters.

Determination of biodegradable dissolved organic carbon in waters: comparison of batch methods

An effect of different types of bacterial inocula upon the final biodegradable dissolved organic carbon (BDOC) result was investigated in samples of both low and high BDOC concentrations. Stream water and leaf leachate samples were incubated either with free, suspended bacteria or with bacteria attached to the stream sediment particles or attached to artificial substrata. The time course of dissolved organic carbon (DOC) decomposition was observed using absorbance analysis of DOC. BDOC determination by means of commonly used suspended bacteria as the inoculum made for an underestimation of BDOC between 5% and 25%, compared with attached bacterial community (biofilm). The reason for these findings could be the higher microbial diversity, higher metabolic activity of attached bacteria and abiotic adsorption of organic molecules to inorganic support and biofilm matrix surfaces. Adsorbed DOC is easily hydrolyzed and utilized by biofilm bacteria.

Modification of the equilibrium partitioning approach for volatile organic compounds in sediment

Although weakly hydrophobic chemicals such as volatile organic compounds (VOCs) tend not to persist in sediments, they may nevertheless be present in some sediments because of recent or ongoing releases. Standard methods are not available for assessing risks to benthic invertebrates due to VOCs in sediment. More strongly hydrophobic organic chemicals are frequently assessed by using the equilibrium partitioning (EqP) approach, which predicts the bioavailable fraction of chemical (the concentration dissolved in pore water) from the sediment-sorbed fraction, assuming that partitioning is at equilibrium. As typically applied, the EqP approach is ineffective for assessing VOCs in sediment, because the standard EqP equation fails to account for the contribution of dissolved chemical to the total chemical concentration in sediment. For chemicals with low organic carbon-water partition coefficients (Kocs), this results in nonsensical sediment-quality benchmarks that are more conservative (i.e., lower) than benchmarks calculated by assuming 100% bioavailability. A modified EqP equation is presented that accounts for the dissolved fraction of total chemical concentrations in sediment. Results of the standard and modified EqP equations converge with increasing Koc and are essentially identical at log Koc values exceeding approximately 3.5.

Spectral fluorescence signatures and partial least squares regression: model to predict dissolved organic carbon in water

Spectro-fluorescence signature (SFS) of water samples contains information that may be used to quantify dissolved organic carbon (DOC) if combined with multivariate analyses. A model was built through SFS and partial least squared (PLS) regression. The SFSs of 219 samples of natural water along the Raritan River and Millstone River watersheds located in central New Jersey, and their corresponding DOC concentrations were used to build the model. Calibration, full cross-validation, and prediction performances of various models were statistically compared before optimal model selection. The final selected model, tested on the Passaic River watershed in northern New Jersey, provided a bias of 0.028 mg/l and a root mean squared error of prediction (RMSEP) of 0.35 mg/l. Linked to PLS, SFS can be a quality and cost effective method to perform on-line rapid DOC measurements.

C-rich sandy Ap horizons of specific historical land-use contain large fractions of refractory organic matter

The study focuses on quantitatively important fractions of very stable organic matter in sandy arable soils in which clay and silt, commonly assumed to be the major factors for organic carbon (OC) stabilization, are practically missing. We characterized 23 Ap horizons plus one subsoil with respect to total OC, total N, chemical resistance of OC, microbial biomass, respiration in laboratory incubation and solubility of OC in water (WSOC). The soils varied with respect to historical land-use (heathland, plaggen-manuring, woodland) and soil genetic factors (podzolization, groundwater). Data from long-term experiments on sand and sandy loam were also considered. The soils revealed a wide range of OC content from below 10 to about 50 mgg −1. C to N ratios varied between 10 and 30 and were positively linked to total OC ( R 2=0.87). Graphitized C (‘charcoal’, as H 2O 2-resistant fraction) was of minor importance, with just about 0.5 mg C g −1 soil in most samples. Only some plaggen and heath soils had charcoal C contents around 1 and 1.5 mg g −1 but this was still less than 5% of the total OC. The HCl-resistant C fraction, on the other hand, was extremely large, amounting to 50–90% of the total OC. Its percentage was closely related to total OC ( R 2=0.84). Biomass C contents (fumigation–extraction) were not correlated with total OC. The C-rich soils had low biomass C to total OC ratios (<0.005). The activities of the enzymes catalase and dehydrogenase showed similar relationships. This strongly indicated that major proportions of the organic material do not support a microbial population and are not in a process of net-decomposition. The average respiration rates per unit of OC after 100 days of incubation at 20 °C were lowest in the C-rich samples. Water soluble organic carbon (WSOC) increased slightly with total OC. On an average, a sum of 379±80 μg C g −1 soil was obtained over seven sequential extractions. This was about the same amount as respired in 140 days (373±107 μg CO 2-C g −1) but there was no significant correlation between the respired CO 2-C and the extracted WSOC. The steady-state rate of WSOC released (steps 3–7) per unit of total OC was lowest in the C-rich soils, again indicating the high stability of OC. We concluded that old sandy Ap horizons soils may have high levels of OC with high proportions of very stable (refractory) constituents amounting to more than 50% of total OC or 10–30 mg C g −1 soil.

Influence of Microroughness of Si and Native Oxide on Adsorption of Organic Carbon in Water

The relationship between adsorption of organic carbon present in water and Si surface roughness is examined. The mean roughnesses, Ra, of Si(100) surface after etching in HF solution is the same as that of Si(111) surface. There is no difference between the roughness of the native oxide formed during rinse in ultrapure water and that of the native oxide/Si interface for Si(111). The roughness shows a constant value over all rinse times. These studied observations indicate that the microroughness of the Si surface does not serve as the dominant adsorption site for organic carbon. It is also shown that the field-enhanced oxidation at the beginning of the growth of the native oxide film is important to discuss the dominant adsorption site.

Influence de la reminéralisation sur l'évolution de la biodégradabilité de la matière organique naturelle au cours de l'ozonation

Tests were carried out in order to show the effects of recarbonation on the evolution of the biodegradability of natural organic matter during ozonation. To achieve this objective, four series of tests were conducted on the effluents of one of the sand–anthracite filters at the Ste-Rose plant (City of Laval, Canada). Table 1 presents the chemical characteristics of these effluents. In performing these four series of tests, each sample was divided into four portions. The first portion was not modified: this was the filter effluent water with an alkalinity of 25 mg/l CaCO 3. The alkalinity of the other three portions were adjusted to 100, 175 and 250 mg/l CaCO 3, respectively, by adding increasing quantities of sodium bicarbonate. Then, each portion was ozonated at the same ozone dose using the apparatus shown in Fig. 1. After ozonation, the UV absorbance, the alkalinity and the ozone, oxalate and BDOC concentrations were measured. Standard methods as described in APHA et al. (1992) [APHA, AWWA and WEF (1992) Standard Methods for the Examination of Water and Wastewater. Washington, D.C.] were used for alkalinity and ozone measurements. BDOC measurements were based on a modified version of the Joret and Levi method [Joret, J. C. and Lévi, Y. (1986) Méthode rapide d'évaluation du carbone éliminable des eaux par voie biologique. Trib. Cebedeau 39, 3–9; Joret, J. C., Lévi, Y., Dupin, T. and Gilbert, M. (1988) Rapid method for estimating bioeliminable organic carbon in water. AWWA 1988 Annual Conference, pp. 1715–1725. Orlando, Florida.] and on the Servais Billen method [Servais, P., Anzil, A., Ventresque, C., (1989) Simple method for determination of biodegrable dissolved organic carbon in water. Appl. Environ. Microbiol. 55(10), 2732–2734.]. These tests were performed four times at one-month intervals using filter effluent from the same filter each time. An ozone dose of 0.2 mg O 3/mg DOC was used for the first series of tests. The ozone doses for the other series were 0.5, 0.8 and 1.0 mg O 3/mg DOC respectively. Table 2 indicates the average ozonation conditions. These tests gave the following principal results. In one series (fixed ozone dose and an alkalinity ranging between 25 and 250 mg/l CaCO 3), the reduction in UV absorbance increased with alkalinity. For the first series of tests, this reduction measured 40% in water whose alkalinity was 25 mg/l CaCO 3 and increased to 50% in water whose alkalinity was 250 mg/l CaCO 3. In addition, it was observed that the reduction increased from series to series (Fig. 3). This is to be expected, since the ozone dose also increased from series to series. Thus, for the last series of tests, when the ozone dose was 1.0 mg O 3/mg DOC, the reduction in UV absorbance varied between 60 and 70%. Recarbonation also affects the production of oxalate and of biodegradable dissolved organic carbon (BDOC) as shown in Figs. 4 and 5. Thus, in one series of tests, oxalate production and BDOC production increased as a function of alkalinity. When the results obtained for a sample whose alkalinity was unajusted (25 mg/l CaCO 3) are compared with those obtained for a water whose alkalinity was modified to 250 mg/l CaCO 3, increases of 56 and 46% for the oxalate and the BDOC, respectively (third series of tests) were observed. It is expected that results for these two parameters would parallel one another since oxalate is easily biodegradable. Analysis of all the results has shown (Fig. 7) that there is a linear relationship between oxalate production and BDOC production. Specific UV absorbance (SUVA), which was defined by Edzwald and van Benschoten (1990) [Edzwald, J. K. and van Benschoten, J. E. (1990) Chemical Water and Wastewater Treatment. Springer-Verlag, Berlin.] as UV absorbance/DOC is correlated with BDOC/DOC on figure 6. A similar relationship was observed by Gilbert (1987) and Gilbert (1988) [Gilbert, E. (1987) Biodegradability of ozonation products as a function of COD and DOC elimination by example of substituted aromatic substances. Wat. Res. 21, 1273–1278; Gilbert, E., (1988) Biodegradability of ozonation products as a function of COD and DOC elimination by the example of humic acids. Wat. Res. 22, 123–126.] while they were working with water containing more aromatic compounds and humic acids.

Sub-Sampling Technique for the Determination of Particulate-Phase Organic Carbon in Water

A procedure for determining particulate-phase organic carbon (POC) in water was developed and applied to the analysis of samples from the Laurentian Great Lakes of North America. Water samples were filtered through 0.7 μM pore-size glass fiber filters which were sub-sampled to introduce measurable quantities of paniculate matter into a Carlo Erba EA-1108 elemental analyzer. The sub-sampling technique allowed quick filtration of water samples, typically 1 to 4 liters for open-lake locations, using 47 mm diameter filters while meeting the small size requirement of the combustion chamber. The detection limit of the instantaneous combustion procedure was 2.9 μg of carbon per sub-sample, which translates to 28 μg/L POC for a sample volume of 1 liter. The precision of the sub-samples averaged 6.2% coefficient of variation (CV), which was comparable to the precision of replicate water samples (6.6% CV).

A novel gas-diffusion/flow-injection system coupled with a bulk acoustic wave impedance sensor for total inorganic carbonate and its application to determination of total inorganic and total organic carbon in waters

A novel flow-injection analysis (FIA) system has been developed for the rapid and selective determination of total inorganic carbonate (TIC). The method is based on the diffusion of CO 2 across a PTFE gas-permeable membrane from a stream of 0.5 mol 1 −1 H 2SO 4 (0.50 ml min −1) and H 2O (0.50 ml min −1) merging into a stream of 10 mM tris(hydroxymethylamino)methane containing 0.5 mM KCl (1.00 min min −1). The CO 2 trapped in the acceptor solution is determined on-line by a bulk acoustic wave impedance sensor and the signal is proportional to the concentration of TIC present in the original samples. The proposed system was applied to the direct determination of TIC in natural and waste waters and the indirect determination of the total organic carbon content based on wet chemical oxidation of the samples, it exhibited a linear frequency response up to 20 mM bicarbonate with a detection limit of 10 μM, and the precision was better than 1% (RSD) at a throughput of 45 samples per hour. The effects of composition of acceptor stream, cell constant of the conductivity sensor, sample volume, flow rates and potential interferents on the FIA signals were discussed in detail.

Sorption of chlorinated C 1- and C 2-hydrocarbons and monocyclic aromatic hydrocarbons on sea sediment

The sorption of chlorinated C 1- and C 2-hydrocarbons and monocyclic aromatic hydrocarbons on sea sediment was studied with a miscible displacement technique. Detection was done either by on-line UV-detection or off-line GC-analysis. Equilibrium partitioning coefficients between the salt water phase and the marine sediment were determined for 11 compounds by fitting their breakthrough curves to a local sorption equilibrium model. Based on the obtained partitioning coefficients and on the measurement of the organic carbon content of the sediment, the sorption into the organic carbon fraction was considered. Log K oc data ( K oc = organic carbon-water partitioning coefficient) were calculated. A linear relationship between the log K oc values and the log K ow data ( K ow = octanol-water partitioning coefficient) was found ( r = 0.94, n = 11). However, the sorption was lower than expected from the log K ow data. Finally, the implications of the experimental results for the sorption behaviour of the compounds in the marine environment were evaluated. It was concluded that the sea sediment does not act as an important sink for these anthropogenic compounds.