Jussi V. K. Kukkonen

Binding of organic pollutants to humic and fulvic acids: Influence of pH and the structure of humic material

Abstract In order to compare their binding capacities, humic acids (HA) and fulvic acids (FA) were isolated from water and extracted from sediments, and used to measure partition coefficients (k oc ) for the model compounds benzo(a)pyrene (BaP) and pentachlorophenol (PCP). To study the effect of pH on the binding capacity of humic substances, k oc values were measured at pH 5.0, 6.5 and 8.0. An equilibrium dialysis method was used to determine the k oc and elemental analysis, 13 C-NMR and FT-IR spectra were carried out on HA and FA to examine the relationship between the structure of humic material and the partition coefficients. The results show that HA have a greater affinity for binding hydrophobic compounds than FA. Change in pH only weakly affects k oc values for the neutral chemical BaP while k oc values for PCP (about 10 2 times lower than values of BaP) decrease radically with an increasing pH from 5.0 to 8.0. This suggest that only the unionized form of a weak organic acid like PCP can interact with the humic material. Moreover, elemental analysis and spectra indicate that high k oc values can be related to a large aromatic content and to a rather low content of functional groups in the humic structures. This, at least partly, explains why the more hydropholic HA bind the model chemicals more than FA, and why the sedimentary humic substances show a higher binding capacity in comparison with the largely functionalised soluble humic compounds from the water phase.

Bioavailability of organic pollutants in boreal waters with varying levels of dissolved organic material

Abstract Dissolved organic matter (DOM) in 20 surface waters in Eastern Finland were characterized to examine relationships between structural and compositional properties of DOM and partition coefficients ( K p ) describing sorption of four model contaminants to DOM and the bioavailability of contaminants by Daphnia magna . The hydrophobic acids (HbA), hydrophobic neutrals (HbN) and hydrophilic (HI) fractions of DOM were separated by XAD-8 resin. The K P s were measured by equilibrium dialysis. Model contaminants were benzo(a)pyrene (BaP), naphthalene (NAPH), 3.3′,4.4′-tetrachlorobiphenyl (TCB) and dehydroabietic acid (DHAA). DOM concentrations varied from 2.0 to 38.3 mg org. C/l in the water series. The percentage of HbA and the aromaticity of DOM, as indicated by the absorptivity at 270 nm (A 270 ) and hydrogen/carbon ratio (H/C ratio), increased with increasing DOM concentration. Significant correlations were observed between K P of BAP, A 270 and HbA content of the DOM from different sources. For the other contaminants similar kinds of relationships between K p s and quality parameters of DOM could not be found. The bioavailability of model compounds was decreased by increasing DOM concentration in the water series. For all four model contaminants, measured bioconcentration factors (BCF) correlated well with the A 270 of a water and HbA content of the DOM. These results show that the total DOM concentration is an important factor controlling the bioavailability of xenobiotics in natural waters. Besides the quantity also the quality of DOM, like proportion of HbA, can contribute in bioavailability.

Effects of XAD-8 fractions of dissolved organic carbon on the sorption and bioavailability of organic micropollutants

The dissolved organic carbon (DOC) from a stream water near a peat deposit was fractionated into hydrophobic-acid (HbA), hydrophobic-neutral (HbN), and hydrophilic (Hl) subcomponents by XAD-8 chromatography. The capacity of these fractions and the total (unfractionated) water to bind hydrophobic organic contaminants was measured by equilibrium dialysis, and the effect of binding on contaminant bioavailability was measured inDaphnia magna. Model contaminants were the poly cyclic aromatic hydrocarbons, naphthalene (NPH) and benzo(a)pyrene (BaP), and the polychlorinated biphenyl, 2,2′,5,5′-tetrachlorobiphenyl (TCB).Both BaP and TCB exhibited high partition coefficients (Kps) for binding to both the total DOC and the hydrophobic components of the DOC. BaP had a higher affinity for binding to the HbA fraction, while TCB (and 3 other PCBs had a higher affinity for the HbN fraction. The Kps for binding to the Hl fraction were twofold to tenfold lower than for binding to the hydrophobic fractions. The less hydrophobic compound, NPH, had a much lower Kp, and little difference was seen between the fractions. The total water and the different DOC fractions reduced the uptake and accumulation of BaP and TCB byD. magna in proportion to the capacity of the DOC for binding the contaminants. Data were consistent with the hypothesis that a contaminant bound to DOC (total water or any of the fractions) is unavailable for uptake by biota. Uptake of NPH was not substantially affected by the DOC, consistent with its lower Kp.

Analysis of fullerene-C60 and kinetic measurements for its accumulation and depuration in Daphnia magna

A simple method for analyzing masses of water suspended fullerenes (nC60) in Daphnia magna by extracting to toluene and measuring by ultraviolet-vis spectrophotometry was developed. This method was used to assess bioaccumulation and depuration rates by daphnia after nC60 exposure in artificial freshwater. Accumulation was rapid during the first few hours, and based on accumulation modeling, 90% of the steady-state concentration was reached in 21 h. After exposure for 24 h to a 2 mg/L fullerene solution, the daphnia accumulated 4.5+/-0.7 g/kg wet weight, or 0.45% of the organism wet mass. Daphnids exposed to 2 mg/L fullerenes for 24 h eliminated 46 and 74% of the accumulated fullerenes after depuration in clean water for 24 and 48 h, respectively. Transmission electron microscopy revealed that the majority of the fullerenes present in the gut of daphnids were large agglomerates. The significant fullerene uptake and relatively slow depuration suggest that D. magna may play a role as a carrier of fullerene from one trophic level to another. Additionally, D. magna may impact the fate of suspended fullerene particles in aquatic ecosystems by their ability to pack fullerene agglomerates into larger particles than were found in the exposure water, and then excrete agglomerates that are not stable in water, causing them to settle out of solution. This process decreases fullerene exposure to other aquatic organisms in the water column but may increase exposure to benthic organisms in the sediment.

Distribution of organic carbon and organic xenobiotics among different particle-size fractions in sediments

The distributions of benzo[a]pyrene, hexachlorobiphenyl, and total organic carbon in a Lake Michigan sediment and a Florissant soil sample were determined and related to the known bioavailability of the compounds. The distribution of organic compounds among small particles (<63 μm diameter) was different from the distribution of the total organic carbon. However, the organic matter remained the major sorbent for these compounds. Changing the fractionation conditions, by performing the fractionation in distilled water instead of natural lake water, altered the distributions for both organic carbon and xenobiotics among the particles. Further, the contaminant distribution relative to organic carbon content differed between particle-size fractions and between contaminants of different compound classes, e.g., PAHs and PCBs. The differential distribution of the contaminants in the particle-size fractions likely contributed to the observed differences in bioavailability of organic contaminants for benthic organisms and may be exacerbated by selective feeding.

Biomarker responses along a pollution gradient: Effects of pulp and paper mill effluents on caged whitefish

Abstract Lake Saimaa (SE Finland) is a large oligotrophic lake receiving biologically treated effluent from a bleached kraft pulp and paper mill. Hatchery-reared juvenile whitefish ( Coregonus lavaretus L. s.l.), a species known to feed on plankton and other particulates, were caged using a technique developed and optimized for this species and were exposed for one month in five downstream stations (3.3–16 km). Two reference stations (4.5–8.5 km) upstream from the effluent outlet were used. An exposure gradient of chlorinated organics was assessed by determining concentrations of conjugated chlorophenolics (CPs) in bile and CPs as well as extractable organic halogens (EOX) in gut lipids. Activities of liver cytochrome P4501A (CYP1A) monooxygenase and two conjugation enzymes, uridinediphospho glucuronosyltransferase (UDP-GT) and glutathione S -transferase (GST), were measured as indicators of exposure. Humoral antibody (IgM) level in plasma was used to estimate immune capacity. Other blood parameters were also analyzed. Fish caged nearest the mill (3.3 km) had concentrations of CPs in bile 50-fold that of upstream reference fish. A gradual, distance-related, decrease of CPs in bile was seen. A similar trend was seen in EOX and concentrations of CPs in gut lipid. Induction of CYP1A, measured as activity of 7-ethoxyresorufin O -deethylase (EROD), was seen in fish at all downstream sites. At the site nearest the mill, EROD activity was 13-fold higher compared to the reference area. No significant changes were seen in liver UDP-GT or GST. Levels of plasma IgM were 58–97% of reference values in fish caged at downstream from the outfall. We conclude that biomarkers in this study implicated the effluent as a causal factor and that relative severity of exposure was inversely related to distance from the effluent source.

Toxicity assessment of sediments from three European river basins using a sediment contact test battery

The toxicity of four polluted sediments and their corresponding reference sediments from three European river basins were investigated using a battery of six sediment contact tests representing three different trophic levels. The tests included were chronic tests with the oligochaete Lumbriculus variegatus, the nematode Caenorhabditis elegans and the mudsnail Potamopyrgus antipodarum, a sub-chronic test with the midge Chironomus riparius, an early life stage test with the zebra fish Danio rerio, and an acute test with the luminescent bacterium Vibrio fischeri. The endpoints, namely survival, growth, reproduction, embryo development and light inhibition, differed between tests. The measured effects were compared to sediment contamination translated into toxic units (TU) on the basis of acute toxicity to Daphnia magna and Pimephales promelas, and multi-substance Potentially Affected Fractions of species (msPAF) as an estimate for expected community effects. The test battery could clearly detect toxicity of the polluted sediments with test-specific responses to the different sediments. The msPAF and TU-based toxicity estimations confirmed the results of the biotests by predicting a higher toxic risk for the polluted sediments compared to the corresponding reference sediments, but partly having a different emphasis from the biotests. The results demonstrate differences in the sensitivities of species and emphasize the need for data on multiple species, when estimating the effects of sediment pollution on the benthic community.

Measuring assimilation efficiencies for sediment-bound PAH and PCB congeners by benthic organisms

Abstract Assimilation efficiencies (AEs) of sediment-sorbed 3H-benzo(a)pyrene (BaP) and 14C-2, 2′,4,4′,5,5′-hexachlorobiphenyl (HCBP) were measured in Diporeia spp (Amphipoda) and the AE for BaP was determined in Lumbriculus variegatus (Oligochaeta). For Diporeia, three methods of determining AEs were compared and for L. variegatus AEs were measured by two methods. The first method used organic carbon as a tracer based on a feeding selectivity index (SI) and the relative concentrations in the sediment and fecal material. After 10-day exposure, the AEs in Diporeia for BaP and HCBP were 45% to 57% and 46% to 58%, respectively. The AEs in L. variegatus for BaP were 0% to 26% throughout the 5-day exposure. The second method estimated assimilation from ingestion based on the feeding rate and the SI for organic carbon. The AEs in Diporeia for BaP and HCBP were 11 to 15% and 36% to 52%, respectively. For the third approach, a dual-label technique was used with 14C-polydimethylsiloxane as a non-assimilated tracer for estimating AE based on the relative ratio of the assimilated and non-assimilated tracers in the food and fecal material. This technique gave a BaP-AE of 56% for Diporeia after 10 days. The BaP-AE in L. variegatus ranged from 23% to 26% for the first day of exposure, then decreased to 10% by the end of the 5-day exposure period. Differences in the AEs for Diporeia exposed to BaP determined from these techniques result, in part, from the differential distribution of the xenobiotics among the sediment particles and the selective feeding by Diporeia.

Acute toxicity of chemicals to Daphnia magna in humic waters

Abstract The acute lethality of 13 organic compounds and five heavy metals towards Daphnia magna has been studied in the presence of several natural humic waters. Humic lake water, as compared to humus-free control water, markedly altered the LC 50 values of most of the organic compounds and heavy metals. Most distinctly, the toxicity of fenvalerate, lindane and cadmium to D. magna increased. None of the organic compounds studied, including both weak acids (phenolics) and a base (paraquat), showed decreased toxicity in humic water. The toxicity of copper and mercury, on the other hand, was lower in humic water relative to the control. The toxicity of fenvalerate increased significantly in several natural waters sampled from Finland, and only very small additions (∼0.3 mg dissolved organic carbon (DOC)/l) of humics to control water were effective in this respect. The toxicity of fenvalerate to D. magna in Lake Baikal (Russia) water was, in contrast to all other natural waters studied, similar to that measured in humus-free control water.

Bioavailability of atrazine, pyrene and benzo[a]pyrene in European river waters

Thirteen river waters and one humic lake water were characterized. The effects of dissolved organic matter (DOM) on the bioavailability of atrazine, pyrene and benzo[a]pyrene (B[a]P) was evaluated. Binding of the chemicals by DOM was analyzed with the equilibrium dialysis technique. For each of the water samples, 24 h bioconcentration factors (BCFs) of the chemicals were measured in Daphnia magna. The relationship between DOM and other water characteristics (including conductivity, water hardness and pH), and bioavailability of the chemicals was studied by performing several statistical analyses, including multiple regression analyses, to determine how much of the variation of BCF values could be explained by the quantity and quality of DOM. The bioavailability of atrazine was not affected by DOM or any other water characteristics. Although equilibrium dialysis showed binding of pyrene to DOM, the bioavailability of pyrene was not significantly affected by DOM. The bioavailability of B[a]P was significantly affected by both the quality and quantity of DOM. Multiple regression analyses, using the quality (ABS270 and HbA%) and quantity of DOM as variables, explained up to 70% of the variation in BCF of B[a]P in the waters studied.