Jarkko Akkanen

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.

Key site variables governing the functional characteristics of Dissolved Natural Organic Matter (DNOM) in Nordic forested catchments

Abstract.The objective of this study was to extract and evaluate key catchment characteristics explaining the main variation in properties of dissolved natural organic matter (DNOM) in surface waters draining each catchment. A number of classical and sophisticated DNOM characterisation methodologies were used for this purpose. The explanatory capability of site characteristics on the variation in descriptors of DNOM, including elemental analysis (EA), DOC fractionation, SEC, CZE, CGE, UV/Vis- and FTIR spectra, FES, TLS, ESR, ESI/MS, 13C-CPMAS-NMR, potentiometric pH titration as well as functional characteristics such as biodegradability, and the response of macrophyte and PAH partitioning coefficients were evaluated. The sampling sites were all natural, coniferous, heathery-forested catchments with bogs, forming a climatic, anthropogenic deposition and proportional biotope cover gradient.Correlations to the main principal components, as well as a correlation matrix, singled out total S-deposition as the key explanatory site parameter, accounting for most of the variation in DNOM descriptors. Other significant factors were H+ concentration, length of growing season, biotope coverage (i.e., peatland/ or lake/watershed ratio), site elevation and TOC concentration. Total sulphur (S) deposition was strongly negatively correlated to the molecular weight, aromaticity, carboxylic acidity and sorption capacity of PAH. A greater proportion of lake and Histosol biotopes of the sampling sites were reflected in a greater aliphatic character of the DNOM. PCA clustering of samples from the same site in spring and fall showed a basic site-specific DNOM quality and a weak season effect. The Hasse diagram technique (a method of partial order theory) was used to show, for instance, how the relative Histosol coverage may determine NOM quality and, in turn, how this coincides with high macrophyte response.

Essential characteristics of natural dissolved organic matter affecting the sorption of hydrophobic organic contaminants

Abstract.Association of benzo[a]pyrene (BaP), pyrene, 3,3′,4,4′-tetrachlorobiphenyl (TCB) and 2,2′,4,4′-tetrabromo diphenyl ether (TBDE) with natural dissolved organic matter (DOM) was studied. The DOM samples were previously collected from natural waters at five Nordic sites during fall 1999 and spring 2000, isolated by the reverse osmosis method, and thoroughly characterized. The purpose was to determine the essential characteristics that predict the sorption capacity of DOM for hydrophobic contaminants. DOM isolates were dissolved in artificial freshwater to give a dissolved organic carbon concentration of 15 mg L–1. Partition coefficients (KDOC) of the model compounds between water and DOM were measured by the equilibrium dialysis method. Further, the bioavailability of BaP and pyrene to Daphnia magna was tested in the presence of DOM with various qualities. A strong negative correlation was found for the KDOC values of BaP (R = –0.922) and pyrene (R = –0.929) with spectral absorbency ratio (A254/A400), while the correlation (R = –0.760) was weaker for the KDOC values of TCB. The KDOC values for TCB correlated (R = 0.849) strongly with specific visible absorbency (A600/TOC), while the KDOC values for TBDE correlated (R = –0.739) with relative fluorescence emission. Generally, bioavailability of BaP and pyrene to D. magna reflected the measured association of the compounds with DOM. The data emphasize the importance of aromaticity of DOM, estimated by simple spectroscopic methods, in predicting sorption capacity for polycyclic aromatic hydrocarbons. The situation with halogenated compounds still remains unclear.

Biotransformation and bioconcentration of pyrene in Daphnia magna

Water fleas (Daphnia magna) were exposed to [14C]pyrene in the presence and absence of piperonyl butoxide (PBO), a general cytochrome P450 (CYP) inhibitor, in organic carbon-free artificial freshwater (AFW, DOC<0.2 mg l(-1)) and in natural lake water (DOC=19.9 mg l(-1)) for 24 h. The bioconcentration of total radioactivity after 24 h exposure was 50% lower in the natural lake water, indicating decreased bioavailability of pyrene by the dissolved organic matter. However, the proportions of parent compound were only ca. 12 and 19% of the total body burden in daphnids exposed in AFW and natural lake water, respectively. Therefore, the tissue concentration of the parent pyrene was not significantly different in the daphnids exposed in the two different waters. Due to extensive biotransformation the bioconcentration factor (BCF) of parent pyrene was only 16 and 23% of the BCF calculated on the basis of total radioactivity in the daphnids in AFW and natural lake water, respectively. The proportion of parent pyrene was significantly higher (over 60%) in the daphnids exposed simultaneously to PBO, which indicates the involvement of CYP monooxygenases in the biotransformation. Furthermore, increasing PBO concentration decreased the accumulation of total radioactivity in AFW but not in the natural lake water. The data demonstrate capability and importance of CYP monooxygenases in biotransformation of polycyclic aromatic hydrocarbons in D. magna.

A screening study on the fate of fullerenes (nC60) and their toxic implications in natural freshwaters

Increasing usage of fullerenes (C60 ) increases their opportunities to be released into the environment. For risk assessment, it is important to understand the environmental fate and ecotoxicological effects of C60 . In the present study, fullerene settling was measured during a 1-yr period with 4 different lake waters and an artificial freshwater, and Daphnia magna immobilization and fullerene accumulation was also measured in each of the lake waters. Depending on the characteristics of the lake waters, fullerenes either exhibited extended water stability or settled rapidly; in all waters, there was a fraction that remained stable after 1 yr. Water stability was affected by the quality and molecular size distribution of dissolved natural organic matter (DNOM). Increasing DNOM molecular sizes with high aromatic content enhanced water stability. Immobilization of D. magna was generally quite low (under 20%) and highly variable after 24 h and 48 h at initial fullerene concentrations up to 10 mg/L. Substantial settling occurred during the time period for acute toxicity assays (i.e., 48 h), which should be anticipated when conducting toxicity assays. There were no significant differences in the quantity of accumulated fullerenes among the different lake waters at fullerene concentrations of 0.5 mg/L, but there were differences at 2 mg/L.

Bioaccumulation and biotransformation of polycyclic aromatic hydrocarbons during sediment tests with oligochaetes (Lumbriculus variegatus)

In some kinetic studies with aquatic invertebrates, the bioaccumulation of polyaromatic hydrocarbons (PAHs) has been observed to peak at the beginning of the test. This has been explained by the depletion of PAHs from pore water due to limited desorption during the bioaccumulation test or, alternatively, by the activation of biotransformation mechanisms in the organisms. In the present study, we exposed the aquatic oligochaetes, Lumbriculus variegatus, to creosote oil-contaminated sediments to examine the bioaccumulation of PAHs and to clarify the importance of contaminant depletion and biotransformation for it. The contaminant depletion was studied by replanting test organisms into fresh, nondepleted test sediments at 3-d intervals over 12 d and by comparing the resulting body burdens to those of the organisms that were not replanted. The biotransformation capability of L. variegatus was assessed by following the concentration of 1-hydroxypyrene (1-HP), a phase I metabolite of pyrene, in oligochaete tissue during a 15-d test. We observed that the bioaccumulation of most PAHs indeed peaked at the beginning of the test. The concentrations in the replanted organisms were only 1.5 to 2 times higher than in nonreplanted organisms during the first 9 d of the test and, by day 12, no differences were detected. 1-Hydroxypyrene was detected in oligochaete tissue throughout the exposures, and concentrations decreased over time. However, the proportion of 1-HP to pyrene increased linearly during the test. These results indicated that the depletion of contaminants has only a minor effect on their bioaccumulation in oligochaetes and that the cause for the observed bioaccumulation curve shape is rapid elimination of the contaminants and, possibly to some degree, their metabolites.

On the borderline of dissolved and particulate organic matter: partitioning and bioavailability of polycyclic aromatic hydrocarbons.

The functionality of dissolved organic matter (DOM) was studied by assessing the availability of polycyclic aromatic hydrocarbons (PAHs) spiked in pore water samples separated from sediments by water extraction and centrifugation with or without subsequent filtration. The purpose was to compare the effects of traditionally defined DOM (0.45-μm cut off) and larger colloidal material present in the separated pore water samples on the partitioning and bioavailability of PAHs. The tested PAHs included phenanthrene (Phe), fluoranthene (Flu), pyrene (Pyr) and benzo[a]pyrene (BaP). Bioavailability of the selected PAHs was tested with two ecologically different organisms: pelagic filter feeder Daphnia magna and sediment-dwelling deposit feeder Lumbriculus variegatus. Sorption to DOM (i.e. in filtered samples) was clearly higher for BaP than for the other PAH. This was also reflected in significantly reduced bioavailability for both model organisms in the filtered samples compared to DOM-free conditions. For the other PAHs the sorption was significant only in the unfiltered samples indicating the importance of larger colloidal material. Thus, the bioavailability of PAHs was also more effectively reduced by the colloidal material. This holds true for both the model organisms, indicating that the ecological differences i.e. filter feeder vs. deposit feeder do not affect in this respect. It appears that considering only traditionally defined DOM, material that may be present in environmental samples and is important for the speciation and bioavailability of contaminants is ignored.

Toxicity of fullerene (C60) to sediment‐dwelling invertebrate Chironomus riparius larvae

An environmentally realistic method to test fullerene (C(60) ) toxicity to the benthic organism Chironomus riparius was created by allowing suspended fullerenes to settle down, making a layer on top of the sediment. To test the hypothesis that higher food concentrations will reduce toxic responses, two food concentrations were tested (0.5 and 0.8% Urtica sp.) in sediment containing fullerene masses of 0.36 to 0.55 mg/cm(2) using a 10-d chronic test. In the 0.5% food level treatments, there were significant differences in all growth-related endpoints compared with controls. Fewer effects were observed for the higher food treatment. Fullerene agglomerates were observed by electron microscopy in the gut, but no absorption into the gut epithelial cells was detected. In the organisms exposed to fullerenes, microvilli were damaged and were significantly shorter. The potential toxicity of fullerene to C. riparius appears to be caused by morphological changes, inhibiting larval growth.

Bioaccumulation of atrazine and chlorpyrifos to Lumbriculus variegatus from lake sediments

The bioaccumulation of the pesticides chlorpyrifos and atrazine to the benthic oligochaeta Lumbriculus variegatus from four diverse artificially contaminated lake sediments (OC 0.13-21.5%) was studied in the laboratory. The steady state of bioaccumulation was not reached within 10d. Chlorpyrifos showed stronger bioaccumulation than the less lipophilic atrazine, the biota-sediment accumulation factors (BSAFs) being 6.2-99 for the former and 1.9-5.3 for the latter. While bioaccumulation factors (BAFs) dropped with increasing organic content of the sediments, the high level and considerable range of the obtained BSAFs indicate other sediment qualities, such as the age and characteristics of the organic material, having a strong effect on the bioavailability of these compounds. The slow and incomplete desorption of chlorpyrifos from the most inorganic sediment indicates also that this compound may be strongly bound to some type of inorganic material. Any specific influential sediment fraction or characteristic could not be identified.

Responses of Lumbriculus variegatus to Activated Carbon Amendments in Uncontaminated Sediments

Activated carbon (AC) amendment is a recently developed sediment remediation method. The strong hydrophobic organic contaminant sorption efficiency of AC has been shown in several studies, but effects on benthic organisms require more investigation. The AC induced effects on egestion rate, growth and reproduction of Lumbriculus variegatus were studied by applying bituminous coal based AC in three different particle size fractions, namely <63 μm (90%, AC(p)), 63-200 μm (AC(m)) and 1000 μm (AC(g)), to natural uncontaminated (HS) and artificial sediment (AS). Egestion rate, growth and reproduction decreased with increasing AC concentration and finer AC particle fractions, effects being stronger on HS than on AS sediment. Lipid content in AS was reduced already at the lowest AC doses applied (AC(p) and AC(m) 0.05%, AC(g) 0.25%). In addition, hormesis-like response was observed in growth (AS) and reproduction (AS, HS) indicating that AC may disturb organisms even at very low doses. Potential ecological effects need to be further evaluated in an amendment- and site-specific manner.