Seasonal influences on PCB retention and biotransformation in fish

There is extensive evidence that fish from waters with polychlorinated biphenyls (PCB)-contaminated sediments accumulate PCBs and related chemicals and that people who eat fish from contaminated waters have higher body burdens of PCBs and PCB metabolites than those who do not. PCBs and their metabolites are potentially toxic; thus, it is important to human health to understand the uptake, biotransformation, and elimination of PCBs in fish since these processes determine the extent of accumulation. The intestinal uptake of PCBs present in the diet of fish into fish tissues is a process that is influenced by the lipid composition of the diet. Biotransformation of PCBs in fish, as in mammals, facilitates elimination, although many PCB congeners are recalcitrant to biotransformation in fish and mammals. Sequential biotransformation of PCBs by cytochrome P450 and conjugation pathways is even less efficient in fish than in mammalian species, thus contributing to the retention of PCBs in fish tissues. A very important factor influencing overall PCB disposition in fish is water temperature. Seasonal changes in water temperature produce adaptive physiological and biochemical changes in fish. While uptake of PCBs from the diet is similar in fish acclimated to winter or summer temperatures, there is evidence that elimination of PCBs occurs much more slowly when the fish is acclimated at low temperatures than at warmer temperatures. Research to date suggests that the processes of elimination of PCBs are modulated by several factors in fish including seasonal changes in water temperature. Thus, the body burden of PCBs in fish from a contaminated location is likely to vary with season.     

Changes in the pore network structure of Hanford sediment after reaction with caustic tank wastes

At the former nuclear weapon production site in Hanford, WA, caustic radioactive tank waste leaks into subsurface sediments and causes dissolution of quartz and aluminosilicate minerals, and precipitation of sodalite and cancrinite. This work examines changes in pore structure due to these reactions in a previously-conducted column experiment. The column was sectioned and 2D images of the pore space were generated using backscattered electron microscopy and energy dispersive X-ray spectroscopy. A pre-precipitation scenario was created by digitally removing mineral matter identified as secondary precipitates. Porosity, determined by segmenting the images to distinguish pore space from mineral matter, was up to 0.11 less after reaction. Erosion-dilation analysis was used to compute pore and throat size distributions. Images with precipitation had more small and fewer large pores. Precipitation decreased throat sizes and the abundance of large throats. These findings agree with previous findings based on 3D X-ray CMT imaging, observing decreased porosity, clogging of small throats, and little change in large throats. However, 2D imaging found an increase in small pores, mainly in intragranular regions or below the resolution of the 3D images. Also, an increase in large pores observed via 3D imaging was not observed in the 2D analysis. Changes in flow conducting throats that are the key permeability-controlling features were observed in both methods.     

Comparison of Stream Invertebrate Response Models for Bioassessment Metrics1

Waite, Ian R., Jonathan G. Kennen, Jason T. May, Larry R. Brown, Thomas F. Cuffney, Kimberly A. Jones, and James L. Orlando, 2012. Comparison of Stream Invertebrate Response Models for Bioassessment Metrics. Journal of the American Water Resources Association (JAWRA) 48(3): 570-583. DOI: 10.1111/j.1752-1688.2011.00632.x Abstract: We aggregated invertebrate data from various sources to assemble data for modeling in two ecoregions in Oregon and one in California. Our goal was to compare the performance of models developed using multiple linear regression (MLR) techniques with models developed using three relatively new techniques: classification and regression trees (CART), random forest (RF), and boosted regression trees (BRT). We used tolerance of taxa based on richness (RICHTOL) and ratio of observed to expected taxa (O/E) as response variables and land use/land cover as explanatory variables. Responses were generally linear; therefore, there was little improvement to the MLR models when compared to models using CART and RF. In general, the four modeling techniques (MLR, CART, RF, and BRT) consistently selected the same primary explanatory variables for each region. However, results from the BRT models showed significant improvement over the MLR models for each region; increases in R² from 0.09 to 0.20. The O/E metric that was derived from models specifically calibrated for Oregon consistently had lower R² values than RICHTOL for the two regions tested. Modeled O/E R² values were between 0.06 and 0.10 lower for each of the four modeling methods applied in the Willamette Valley and were between 0.19 and 0.36 points lower for the Blue Mountains. As a result, BRT models may indeed represent a good alternative to MLR for modeling species distribution relative to environmental variables.     

Estimating willingness to pay for a threatened species within a threatened ecosystem

This study conducts a choice experiment to determine the willingness to pay for Palouse Prairie conservation. The giant Palouse earthworm (Driloleirus americanus), a rare species endemic to the Palouse region, is included as an attribute of conservation and serves as a method for determining the willingness to pay for protecting the species. This method evaluates the value of the earthworm as an attribute of an overall willingness to pay for threatened ecosystem preservation rather than a direct willingness to pay for protecting the species. This method is expected to yield a more accurate measure of willingness to pay for rare species. The annual willingness to pay per household for the giant Palouse earthworm is $20.45 based on the conditional logit model and $19.30 based on the mixed logit model. Ranking and relative importance are included as methods for representing a non-monetary value and importance of the giant Palouse earthworm.     

Rising recreancy: flood control and community relocation in Houston,TX, from an environmental justice perspective

This article looks at issues of recreancy, environmental justice, and relocation as they relate to a flood control infrastructure project in inner city Houston. The main research questions were “What forms would recreancy take?” and “Can a project be environmentally just if recreancy is present?” Through the structural coding of 53 semi-structured interviews, recreancy was found even in a project where the sponsors used community cohesion as a guideline. This article illuminates the difficulties flood control project engineers face when working in local communities and argues that engineering issues are also social issues. Further, the relocatees within this flood control project voice some of the same concerns experienced by people relocated in other involuntary infrastructure development projects. The case outlined in this article could be used to better help those involuntarily relocated for flood control.     

Interference with xenobiotic metabolic activity by the commonly used vehicle solvents dimethylsulfoxide and methanol in zebrafish (Danio rerio) larvae but not Daphnia magna

Organic solvents, such as dimethylsulfoxide (DMSO) and methanol are widely used as vehicles to solubilise lipophilic test compounds in toxicity testing. However, the effects of such solvents upon innate detoxification processes in aquatic organisms are poorly understood. This study assessed the effect of solvent exposure upon cytochrome P450 (CYP)-mediated xenobiotic metabolism in Daphnia magna and zebrafish larvae (4 d post fertilisation). Adult D. magna were demonstrated to have a low, but detectable, metabolism of ethoxyresorufin in vivo and this activity was not modulated by pre-exposure to DMSO or methanol (24 h, up to 0.1% and 0.05% v/v, respectively). In contrast, the metabolism of ethoxyresorufin in zebrafish larvae was significantly reduced by both solvents (0.1% and 0.05% v/v, respectively) after 24 h of exposure. In zebrafish, these observed decreases in activity towards ethoxyresorufin were accompanied by decreased expression of a variety of genes coding for drug metabolising enzymes (corresponding to CYP1, CYP2, CYP3 and UDP-glucuronyl transferase [UGT] family enzymes), measured by quantitative PCR. Reduction of gene expression and CYP1 enzyme activities by methanol (0.05% v/v) in zebrafish larvae was partially reversed by co-exposure with Aroclor 1254 (100 μg L⁻¹). Overall this study suggests that relatively low concentrations of organic solvents can impact upon the biotransformation of certain xenobiotics in zebrafish larvae, and that this warrants consideration when assessing compounds for metabolism and toxicity in this species.     

Evaluating the role of environmental quality in the sustainable rural economic development of England

The issue of the sustainable development of rural economies in England has recently received considerable attention. This is because many of the poorest areas in the country are rural, often of high environmental quality, but suffering from high unemployment and a lack of services and facilities. The rapid decline in agricultural incomes and in-migration of affluent urban workers since 1990 has exacerbated economic inequality in such areas. A number of factors have the potential to drive rural development and this paper applies, and considers, the feasibility of a method from the USA for combining economic and environmental variables in a regional growth model to examine the hypothesis that environmental quality is an important determinant of sustainable rural development in England. The model output suggests that, although environmental quality does play a role in sustainable rural development in England there are other, more important, factors driving development. These include business and communications infra-structure, the degree and opportunities for commuting and underlying employment prospects. The robustness and limitations of the method for combining economic and environmental variables is discussed in relation to the spatial interrelatedness of Local Authority Districts in England, and conclusions are drawn about areas for refinement and improvement of the method.

LEHR superfund stormwater runoff and putah creek mercury issues

Stormwater runoff from the University of California, Davis/U.S. Department of Energy Laboratory for Energy‐Related Health Research (UCD/US DOE LEHR) Superfund site located on the University of California campus in Davis, California, has been found to contain over 500 ng/L of total recoverable mercury, which is about ten times the California Toxics Rule criterion. This stormwater runoff is discharged to Putah Creek, which is Clean Water Act Section 303(d) listed as impaired for excessive mercury bioaccumulation in edible fish. A discussion is presented on the potential impact of the mercury in stormwater runoff from LEHR leading to excessive bioaccumulation of mercury in Putah Creek fish. The mercury in the stormwater runoff is derived from former flooding of the soils near the creek, which contains mercury derived from abandoned upstream mercury mines located in the Coast Range Vaca Hills to the west of LEHR. The implications of this situation for implementing a Total Maximum Daily Load (TMDL) to control mercury in stormwater runoff to Putah Creek are presented. © 2009 Wiley Periodicals, Inc.     

Compositional changes of crude oil SARA fractions due to biodegradation and adsorption on colloidal support such as clays using Iatroscan

The compositional changes of saturates, aromatics, resins and asphaltenes (SARA) fractions in aqueous clay/oil microcosm experiments with a hydrocarbon-degrading microorganism community were analysed using Iatroscan. The clay mineral samples used in this study were organomontmorillonite, acid-activated montmorillonite and K, Ca, Zn and Cr montmorillonites produced by modifying the original montmorillonite sample. The evaluation and quantification of biodegradation and adsorption were carried out using a combination of the Iatroscan and gravimetric analysis. The SARA compositions in the presence of organomontmorillonite and acid-activated montmorillonite after incubation follow the same pattern in which the aromatic fraction is higher than the other fractions unlike in the presence of unmodified, K, Ca and Zn montmorillonites, where the saturates fraction is higher than the other fractions. Changes in SARA fractions due to biodegradation seemed to occur most in the presence of unmodified and calcium montmorillonites; hence, the removal of SARA fractions due to biodegradation was significant and enhanced in the presence of these two clay samples. However, biodegradation in the presence of organomontmorillonite and acid-activated and Cr montmorillonites was hindered. The study indicated that Cr montmorillonite adsorbed resins most, whereas Zn and K montmorillonites adsorbed aromatics most after incubation.     

Methane biofiltration in the presence of ethanol vapor under steady and transient state conditions: an experimental study

Methane (CH₄) removal in the presence of ethanol vapors was performed by a stone-based bed and a hybrid packing biofilter in parallel. In the absence of ethanol, a methane removal efficiency of 55 ± 1% was obtained for both biofilters under similar CH₄ inlet load (IL) of 13 ± 0.5 g_CH4 m^?3 h^?1 and an empty bed residence time (EBRT) of 6 min. The results proved the key role of the bottom section in both biofilters for simultaneous removal of CH₄ and ethanol. Ethanol vapor was completely eliminated in the bottom sections for an ethanol IL variation between 1 and 11 g_ethanol m^?3 h^?1. Ethanol absorption and accumulation in the biofilm phase as well as ethanol conversion to CO₂ contributed to ethanol removal efficiency of 100%. In the presence of ethanol vapor, CO₂ productions in the bottom section increased almost fourfold in both biofilters. The ethanol concentration in the leachate of the biofilter exceeding 2200 g_ethanol m^?3 _leachate in both biofilters demonstrated the excess accumulation of ethanol in the biofilm phase. The biofilters responded quickly to an ethanol shock load followed by a starvation with 20% decrease of their performance. The return to normal operations in both biofilters after the transient conditions took less than 5 days. Unlike the hybrid packing biofilter, excess pressure drop (up to 1.9 cmH₂O m^?1) was an important concern for the stone bed biofilter. The biomass accumulation in the bottom section of the stone bed biofilter contributed to 80% of the total pressure drop. However, the 14-day starvation reduced the pressure drop to 0.25 cmH₂O m^?1.