Temporal changes in the distribution and relative composition of 15 priority polycyclic aromatic hydrocarbons (PAHs) in water, sediment, and absorbed to polyvinylchloride (PVC) strips were assessed following direct application of liquid creosote to aquatic microcosms. Fourteen microcosms were treated with nominal creosote concentrations ranging from 0.06 to 109 mg/L and two microcosms served as controls. Quantitative analysis of PAHs was performed using high-performance liquid chromatography equipped with a fluorescence detector. Post-treatment concentration of PAHs in water decreased exponentially with time. At 2 d posttreatment, total PAHs (⌺ PAH) ranged from 7.3 g/L (lowest treatment) to 5,803.2 g/L (highest treatment); by 84 d, ⌺ PAH in the same microcosms was reduced to between 0.8 g/L and 13.9 g/L, respectively. The relative composition of PAHs in the water also changed with time; at 2 d posttreatment, ⌺ PAH in the lowest treatment (7.3 g/L) reflected contribution from nine PAHs, whereas only two PAHs contributed to this concentration (0.8 g/L) at 84 d. Low and high molecular weight (mol. wt.) PAHs were lost first from the water column, followed by PAHs of intermediate mol wt. In sediments, a dose-dependent increase in ⌺ PAH was observed above 0.59 mg/L creosote up to 28 d, followed by a decline thereafter in all but the highest treatment. Total PAHs in sediment ranged from 0.91 g/g (lowest treatment) to 63.9 g/g (highest treatment) at 28 d. A dose-dependent relationship was also observed in PVC strips, with ⌺ PAH on PVC ranging from 0.05 to 88 g/cm 2 at 31 d and 0.04 to 18.4 g/ cm 2 at 58 d posttreatment. A mass balance evaluation showed that 88.3% of PAHs was lost from the system after 1 month, indicating that liquid creosote is attenuated relatively quickly in aquatic environments.

Abstract-Temporal changes in the distribution and relative composition of 15 priority polycyclic aromatic hydrocarbons (PAHs) in water, sediment, and absorbed to polyvinylchloride (PVC) strips were assessed following direct application of liquid creosote to aquatic microcosms. Fourteen microcosms were treated with nominal creosote concentrations ranging from 0.06 to 109 mg/L and two microcosms served as controls. Quantitative analysis of PAHs was performed using high-performance liquid chromatography equipped with a fluorescence detector. Post-treatment concentration of PAHs in water decreased exponentially with time. At 2 d posttreatment, total PAHs (⌺ PAH) ranged from 7.3 g/L (lowest treatment) to 5,803.2 g/L (highest treatment); by 84 d, ⌺ PAH in the same microcosms was reduced to between 0.8 g/L and 13.9 g/L, respectively. The relative composition of PAHs in the water also changed with time; at 2 d posttreatment, ⌺ PAH in the lowest treatment (7.3 g/L) reflected contribution from nine PAHs, whereas only two PAHs contributed to this concentration (0.8 g/L) at 84 d. Low and high molecular weight (mol. wt.) PAHs were lost first from the water column, followed by PAHs of intermediate mol wt. In sediments, a dose-dependent increase in ⌺ PAH was observed above 0.59 mg/L creosote up to 28 d, followed by a decline thereafter in all but the highest treatment. Total PAHs in sediment ranged from 0.91 g/g (lowest treatment) to 63.9 g/g (highest treatment) at 28 d. A dose-dependent relationship was also observed in PVC strips, with ⌺ PAH on PVC ranging from 0.05 to 88 g/cm 2 at 31 d and 0.04 to 18.4 g/ cm 2 at 58 d posttreatment. A mass balance evaluation showed that 88.3% of PAHs was lost from the system after 1 month, indicating that liquid creosote is attenuated relatively quickly in aquatic environments.

Statin pharmaceuticals, heavily prescribed in the treatment of hypercholesterolemia, are competitive inhibitors of 3-hydroxy-3-methylglutaryl coenzyme-A reductase (HMGR). In plants, these compounds also inhibit HMGR, which regulates cytosolic isoprenoid biosynthesis in the mevalonic acid (MVA) pathway. Phytotoxicity was evaluated in the higher aquatic plant Lemna gibba exposed to atorvastatin and lovastatin for 7-days by measuring the concentrations of sterols and ubiquinone; products downstream in the MVA pathway. The efficiency of the parallel and unaffected methylerythritol phosphate pathway (MEP) was also evaluated by measuring the end product, plastoquinone. Statin treatment caused an accumulation of plastoquinone, and unexpectedly, ubiquinone, an artifact likely due to metabolite sharing from the plastidial MEP pathway. Statins were, however, highly phytotoxic to L. gibba and HPLC-UV analysis of plant extracts showed significantly decreased concentrations of both stigmasterol and beta-sitosterol, which are critical components of plant membranes and regulate morphogenesis and development. EC10 values for atorvastatin and lovastatin were as small as 26.1 and 32.8 microg/L, respectively. However, hazard quotients indicated that statins present little risk to the model higher aquatic plant Lemna gibba at environmentally relevant concentrations, even though pathway-specific endpoints were 2-3 times more sensitive than traditional gross morphological endpoints typically used in risk assessment.

No abstract

Pharmaceuticals are routinely detected at low concentrations in surface waters, but effects on non-target organisms are not well understood. Microcosms were used to assess ecological responses in freshwater ecosystems to a mixture offourtetracyclines commonly used in veterinary and human medicine. Triplicate microcosms were treated with tetracycline, oxytetracycline, doxycycline, and chlortetracycline, resulting in measured time-weighted average total mixture concentrations of 0, 0.080, 0.218, 0.662, and 2.29 microM, respectively. Responses were assessed in terms of structure and function based on measurements of zooplankton and phytoplankton communities, ecosystem productivity, and water quality. Effects were observed for some endpoints> or = the 0.218 microM treatment. The largest responses were concentration-dependent reductions in total phytoplankton abundance and species richness. Phytoplankton abundance recovered to control levels in all microcosms after treatment was terminated, and resilience (time to return to normal operating range during stress) was observed with respectto phytoplankton species richness. Zooplankton were generally unaffected by the tetracyclines. Responses also included decreased water clarity, lower oxygen concentration, and water temperature. Functional endpoints showed varying sensitivity. On the basis of dissolved oxygen concentrations, community respiration (R) increased while primary productivity (P) was unchanged with increased treatment concentration. The effects observed occurred at considerably greater concentrations than are currently measured in the environment, indicating minimal risk to aquatic organisms.

No abstract

. 6 9 , 9 4 (1991). In the presence of a catalytic quantity of alkali metal mixtures of sulphur diimides RNSNR and R'NSNR' (R, R' = Ph, 4-C6H4Me, 4-C6H40Me, SiMe,, SPh) undergo a rapid scrambling of the R and R' groups. When R and R' are significantly different (e.g., R = Ph, R' = SiMe, or SPh) the equilibrium is shifted to favour the unsymmetrical sulphur dimmide (R 4= R'); the procedure thus represents an effective method for preparing such derivatives. A mechanism involving the centrosymmetric association and rearrangement of two sulphur diimide radical anions is suggested for the observed ligand scrambling. The synthesis and X-ray structure determination of the mixed diimide (4-N02C6H4)SNSN(4-C6H40Me) is reported.The crystals are monoclinic, space gr0upP2~ln; the molecules stack as plates along the a axis in a head-to-head fashion, producing an interplanar spacing between consecutive SzNz units of 3.42 1 A.Key words: sulphur diimide radical anions, skeletal rearrangements, (4-C6H4N0,)SNSN(4-C6H40Me), X-ray structure.KETUT BESTARI, RICHARD T. OAKLEY et A . WALLACE CORDES. Can. J. Chem. 69, 94 (1991). En prksence d'une quantitC catalytique d'un mCtal alcalin, des mklanges des diimides du soufre RSNSNR at R'NSNR' (R, R' = Ph, 4-C6H4Me, 4-C6H40Me, SiMe, et SPh) subissent un brouillage rapide des groupements R et R'. Lorsque R et R' sont des groupements assez diffkrents (par exemple, R = Ph et R' = SiMe, ou SPh), I'Cquilibre est dCplack vers le diimide de soufre non-symktrique (R 4= R'); cette proc6dure reprksente donc une m6thode efficace pour prkparer de tels dkrivCs. Pour expliquer le brouillage observC des ligands, on propose un mkcanisme impliquant une association centrosymetrique et une transposition de deux anions radicaux des diimides du soufre. On rapporte la synthkse et la dktermination de structure (par diffraction des rayons-X) du dimrnide mixte (4-NOrC6H4)SNSN(4-C6H40Me). Les cristaux sont rnonocliniques, groupe d'espace P2,/n; les molCcules s'empilent le long de l'axe a sous la forme de plaquettes dans lesquelles elles sont arrangkes d'une fason t&te-g-t&te provoquant un espacement de 3,421 A entre les plans de deux unit6 successives de S2N2.

In this study, the response of zooplankton communities to single applications of liquid creosote in model aquatic ecosystems (microcosms) was evaluated. Liquid creosote was applied to 14 microcosms at concentrations ranging from 0.06 to 109 mg/L. Two microcosms served as controls. Zooplankton samples were collected from each microcosm on days 7 and 1 before treatment and on days 2, 5, 7, 14, 21, 28, 43, 55, and 83 following treatment. Temporal changes (response-recovery) in composition of the zooplankton community were assessed using principal response curves (PRC). Creosote induced a rapid, concentration-dependent reduction in zooplankton abundance and number of taxa, with maximum response (50-100% reduction in population densities) occurring between 5 and 7 d after treatment. Taxa that dominated at the time of treatment experienced the greatest impact, as indicated by large, positive species weight values (> 1) from the PRC analysis. Many of these taxa recovered to pretreatment or control levels during the posttreatment period, with the degree and duration of recovery being strongly dependent on concentration. Creosote had little effect on species composition at less than 1.1 mg/L, because changes in the types and relative proportion of species contributed from Cladocera, Rotifera, and Copepoda were comparable to those observed in control microcosms. However, a significant shift in species composition was observed at concentrations greater than 1.1 mg/L; these microcosms were generally dominated by low numbers of rotifers, some of which had not been collected before treatment. Community-level effect concentrations (EC50s) were 44.6 and 46.6 micrograms/L at 5 and 7 d, respectively, based on nominal creosote. Corresponding no-effect concentrations were 13.9 and 5.6 micrograms/L. The results of this field study indicate that creosote may pose a significant risk to zooplankton communities at environmental concentrations potentially encountered during spills and/or leaching events.