Volatilization rates of intermediate and low volatility chemicals from water

This paper reports laboratory methods for measuring the gas and liquid phase mass transfer coefficients and volatilization rate constants of intermediate and low volatility compounds and proposes a method for calculating the volatilization rate constants of these types of compounds in the environment.     

Bioaccumulation Factors (BAFs) and Biota to Sediment Accumulation Factors (BSAFs) for PCBs in pike and eels

“Freely-dissolved” aqueous concentrations of 9 trichlorothrough heptachlorobiphenyls are reported, alongside those in sediments and fish from the R. Severn. For most congeners, BSAFs and lipid-normalised BAFs for pike exceed those for eels. Whilst R. Severn BSAFs are comparable with those for L. Ontario trout and New Bedford Harbour flounder, R. Severn BAFs are 1–2 orders of magnitude lower. This discrepancy may be due to inter-species variability, as well as inter-laboratory differences between operational definitions of “freely-dissolved” aqueous PCB, underlining that the same operational definition must be employed if R. Severn BAFs are extrapolated elsewhere. For eels, correlation of Log K^ow with Log BAF is better (R² = 0.66) than with BSAF (R² = 0.13), whilst similar correlation coefficients (R² = 0.81 and 0.82) were observed for pike. When Log K^ow is plotted against BSAF and Log BAF for both species combined, better correlation is observed for Log BAF (R² = 0.65), than BSAF (R² = 0.36). For both species combined, the observed relationship between Log BAF and Log K^ow for trichloro-through heptachlorobiphenyls is: Log BAF = 0.96 * Log K^ow −0.24.     

Perspectives of a large scale environmental survey for chlorinated dioxins: overview and soil data

On November 5, 1984, The Dow Chemical Company issued a report entitled: “Point Sources and Environmental Levels of 2378-TCDD on the Midland Plant Site of The Dow Chemical Company and in the City of Midland, Michigan.” This report is based upon the efforts of a 22-person task force who dedicated approx. 21 months of effort to the generation and analysis of over 6000 analytical data points regarding specific CDD/CDF concentrations in the four basic environmental elements of air, earth, fire (incineration), and water. A summarization of this study will be presented which includes methodology, analytical QA-QC criteria, and representative soil analyses, as they pertain to the survey conclusions.     

The effect of thallium on the growth of Lemna minor and plant tissue concentrations in relation to both exposure and toxicity

The effect of thallium on frond production and the rates of increase in surface area and fresh weight in Lemna minor were examined in terms of concentrations of the element in the growth medium and in the plant. The toxicity indices, EC(50) and threshold concentration, indicate that curtailment of frond expansion occurs at a lower thallium exposure than inhibition of frond multiplication. Production of smaller fronds, rather than chlorosis, was the most notable initial response to thallium stress and, below the threshold of toxicity, enhanced multiplication rates were recorded. Subsequent recovery in thallium-free medium was significant in the region of EC(50) exposures and below, but very little recovery occurred at higher exposures. Lemna minor has a remarkable capacity to accumulate thallium, and accumulation factors of 88 x 10(3) at low exposures, and 6 x 10(3) at high exposures, were recorded, which would suggest some form of active uptake.     

Albatross species demonstrate regional differences in North Pacific marine contamination.

Recent concern about negative effects on human health from elevated organochlorine and mercury concentrations in marine foods has highlighted the need to understand temporal and spatial patterns of marine pollution. Seabirds, long-lived pelagic predators with wide foraging ranges, can be used as indicators of regional contaminant patterns across large temporal and spatial scales. Here we evaluate contaminant levels, carbon and nitrogen stable isotope ratios, and satellite telemetry data from two sympatrically breeding North Pacific albatross species to demonstrate that (1) organochlorine and mercury contaminant levels are significantly higher in the California Current compared to levels in the high-latitude North Pacific and (2) levels of organochlorine contaminants in the North Pacific are increasing over time. Black-footed Albatrosses (Phoebastria nigripes) had 370-460% higher organochlorine (polychlorinated biphenyls [PCBs], dichlorodiphenyltrichloroethanes [DDTs]) and mercury body burdens than a closely related species, the Laysan Albatross (P. immutabilis), primarily due to regional segregation of their North Pacific foraging areas. PCBs (the sum of the individual PCB congeners analyzed) and DDE concentrations in both albatross species were 130-360% higher than concentrations measured a decade ago. Our results demonstrate dramatically high and increasing contaminant concentrations in the eastern North Pacific Ocean, a finding relevant to other marine predators, including humans.     

Mate competition in the velvet swimming crab Necora puber: effects of perceived resource value on male agonistic behaviour

Male velvet swimming crabs [Necora puber (L.)] were observed to engage in long and vigorous agonistic interactions to gain possession of a sexually receptive female. The role of agonistic behaviour in male mate competition in this species was examined by investigating the effect of the perceived presence of sexually receptive females on interactions between males. Exposing male crabs to water conditioned by sexually receptive females resulted in prolonged interactions, with a greater incidence of potentially injurious behaviour than interactions between control crabs, exposed only to sea water. Maleconditioned water also resulted in more offensive behaviour, but these interactions were of shorter duration and not significantly different from sea water controls. Agonistic superiority was strongly correlated with contestant relative size when males were exposed to male-conditioned water or sea water, but not when exposed to female-conditioned water. Overall, the results conformed with the general predictions of game theoretic models in relation to the influence of resource value on agonistic behaviour. Crabs were more persistent and probably incurred greater fitness costs in the perceived presence of a sexually receptive female, when interactions may have been resolved on the basis of factors more closely related to actual fighting ability than the relative body sizes of contestants.     

Design and laboratory testing of a chamber device to measure total flux of volatile organic compounds from the unsaturated zone under natural conditions

To determine if an aquifer contaminated with volatile organic compounds (VOCs) has potential for natural remediation, all natural processes affecting the fate and transport of VOCs in the subsurface must be identified and quantified. This research addresses the quantification of air-phase volatile organic compounds (VOCs) leaving the unsaturated zone soil gas and entering the atmosphere-including the additional flux provided by advective soil-gas movement induced by barometric pumping. A simple and easy-to-use device for measuring VOC flux under natural conditions is presented. The vertical flux chamber (VFC) was designed using numerical simulations and evaluated in the laboratory. Mass-balance numerical simulations based on continuously stirred tank reactor equations (CSTR) provided information on flux measurement performance of several sampling configurations with the final chamber configuration measuring greater than 96% of model-simulated fluxes. A laboratory device was constructed to evaluate the flux chamber under both diffusion-only and advection-plus-diffusion transport conditions. The flux chamber measured an average of 82% of 15 diffusion-only fluxes and an average of 95% of 15 additional advection-plus-diffusion flux experiments. The vertical flux chamber has the capability of providing reliable measurement of VOC flux from the unsaturated zone under both diffusion and advection transport conditions.     

Formation of involatile methylantimony species by Clostridium spp

Trimethylantimony was detected by gas chromatography-mass spectrometry (GC-MS) in the headspace of a soil enrichment culture designed to promote growth of clostridia. Clostridial isolates from the soil enrichment culture were shown to biomethylate inorganic antimony in monseptic culture, using hydride generation-gas chromatographyatomic absorption spectrometry (HG-GC-AAS). GC-MS profiles of headspace gases from soil enrichment cultures shown to generate trimethylantimony, were used to select characterised Clostridium spp for assessment of antimony biomethylation capability. Involatile methylantimony species (up to 21 microg Sb dm(-3)) were detected by HG-GC-AAS in the medium of monoseptic cultures of C. acetobutylicum, C. butyricum and C. cochlearium. The relative quantities of involatile mono-, di- and trimethylantimony species produced over the course of a 28-day cultivation period is consistent with trimethylantimony oxide being a final product of antimony biomethylation by these bacteria, with mono- and dimethylantimony species appearing transiently in the cultures as intermediates of an antimony biomethylation pathway. Clostridia may be the principal agents of antimony biomethylation in methanogenic environments and could give rise to methylated forms of antimony in both the aqueous and gaseous phases.     

The effect of surface-active solutes on water flow and contaminant transport in variably saturated porous media with capillary fringe effects

Organic contaminants that decrease the surface tension of water (surfactants) can have an effect on unsaturated flow through porous media due to the dependence of capillary pressure on surface tension. We used an intermediate-scale 2D flow cell (2.44 x 1.53 x 0.108 m) packed with a fine silica sand to investigate surfactant-induced flow perturbations. Surfactant solution (7% 1-butanol and dye tracer) was applied at a constant rate at a point source located on the soil surface above an unconfined synthetic aquifer with ambient groundwater flow and a capillary fringe of approximately 55 cm. A glass plate allowed for visual flow and transport observations. Thirty instrumentation stations consist of time domain reflectometry probes and tensiometers measured in-situ moisture content and pressure head, respectively. As surfactant solution was applied at the point source, a transient flow perturbation associated with the advance of the surfactant solution was observed. Above the top of the capillary fringe the advance of the surfactant solution caused a visible drainage front that radiated from the point source. Upon reaching the capillary fringe, the drainage front caused a localized depression of the capillary fringe below the point source because the air-entry pressure decreased in proportion to the decrease in surface tension caused by the surfactant. Eventually, a new capillary fringe height was established. The height of the depressed capillary fringe was proportional to height of the initial capillary fringe multiplied by the relative surface tension of the surfactant solution. The horizontal transport of surfactant in the depressed capillary fringe, driven primarily by the ambient groundwater flow, caused the propagation of a wedge-shaped drying front in the downgradient direction. Comparison of dye transport during the surfactant experiment to dye transport in an experiment without surfactant indicated that because surfactant-induced drainage decreased the storage capacity of the vadose zone, the dye breakthrough time to the water table was more than twice as fast when the contaminant solution contained surfactant. The extensive propagation of the drying front and the effect of vadose zone drainage on contaminant breakthrough time suggest the importance of considering surface tension effects on unsaturated flow and transport in systems containing surface-active organic contaminants or systems, where surfactants are used for remediation of the vadose zone or unconfined aquifers.