Differences in p,p'-DDE bioaccumulation from compost and soil by the plants Cucurbita pepo and Cucurbita maxima and the earthworms Eisenia fetida and Lumbricus terrestris

Two plant species, Cucurbita pepo and Cucurbita maxima, and two earthworm species, Eisenia fetida and Lumbricus terrestris, were exposed to soil and compost with equivalent p,p'-DDE contamination. Pollutant bioconcentration was equal in plant roots in both media, but translocation was higher in C. pepo. Bioaccumulation by E. fetida was approximately 6- and 3-fold higher than that by L. terrestris in the soil and compost, respectively. For all species, p,p'-DDE uptake was significantly greater from soil than from compost; 7- to 8-fold higher for plant roots and 3- to 7-fold higher for worms. Abiotic desorption from soil was approximately twice that from the compost. When all the data are normalized for organic-carbon content of the media, the contaminant is more tightly bound by soil than compost. Although the risk associated with p,p'-DDE is higher in soil than compost, important mechanistic differences exist in contaminant binding to organic carbon in the two media.     

Runoff transport of pyrethroids from a residential lawn in central California

An irrigation runoff study on a residential lawn was conducted in California, northeast of Sacramento, during the summer and fall of 2008 to investigate the contribution of turf uses of pyrethroids to residues in Californian urban creek sediments. This study examined how over irrigation (i.e., irrigation that produces runoff) in the summer season may transport recently applied pyrethroids. The study included liquid and granular applications of both bifenthrin [(2-methyl-3-phenyl-phenyl) methyl 3-(2-chloro-3,3,3-trifluoro-prop-1-enyl)-2,2-dimethyl-cyclopropane-1-carboxylate] and beta-cyfluthrin [Cyano(4-fluoro-3-phenoxyphenyl)methyl 3-(2,2-dichloroethenyl)-2,2-dimethyl-cyclopropanecarboxylate]. Generally, runoff did not occur at irrigation rates of 2.03 cm/h (0.8 in/h) but did occur when the irrigation rates were increased to about 3.81 cm/h (1.5 in/h), generating chemical losses in the first runoff event of up to 0.58 and 0.08% of applied for beta-cyfluthrin and bifenthrin, respectively. Chemical runoff losses dropped significantly between over-irrigation events with the third over-irrigation event chemical runoff losses representing 0.026 and 0.015% of applied for beta-cyfluthrin and bifenthrin, respectively. Runoff losses were generally less for liquid formulations than granular formulations but within a factor of three. Additionally, the study included a simulated winter rainstorm 8 wk after application. The low runoff losses from turf seen in this study suggest that other sources could be contributing to observed residues in urban streams. Other sources could include pyrethroids ending up on impervious surfaces, such as concrete driveways from off-target applications to turf, spills, and other poor handling practices, or pyrechroids applied directly to impervious surfaces for insect control.     

On the use of log-transformation vs. nonlinear regression for analyzing biological power laws

Power-law relationships are among the most well-studied functional relationships in biology. Recently the common practice of fitting power laws using linear regression (LR) on log-transformed data has been criticized, calling into question the conclusions of hundreds of studies. It has been suggested that nonlinear regression (NLR) is preferable, but no rigorous comparison of these two methods has been conducted. Using Monte Carlo simulations, we demonstrate that the error distribution determines which method performs better, with NLR better characterizing data with additive, homoscedastic, normal error and LR better characterizing data with multiplicative, heteroscedastic, lognormal error. Analysis of 471 biological power laws shows that both forms of error occur in nature. While previous analyses based on log-transformation appear to be generally valid, future analyses should choose methods based on a combination of biological plausibility and analysis of the error distribution. We provide detailed guidelines and associated computer code for doing so, including a model averaging approach for cases where the error structure is uncertain.     

Water management decision makers' evaluations of uncertainty in a decision support system: the case of WaterSim in the Decision Theater

Model-based decision support systems are increasingly used to link knowledge to action for environmental decision making. How stakeholders perceive uncertainty in models and visualisations affects their perceptions of credibility, relevance and usability of these tools. This paper presents a case study of water decision makers’ evaluations of WaterSim, a dynamic water simulation model presented in an immersive decision theatre environment. Results reveal that decision makers’ understandings of uncertainty in their evaluations of decision support systems reflect both scientific and political discourse. We conclude with recommendations for design and evaluation of decision support systems that incorporate decision makers' views.     

Are watershed and lacustrine controls on planktonic N2 fixation hierarchically structured?

N2 fixation can be an important source of N to limnetic ecosystems and can influence the structure of phytoplankton communities. However, watershed-scale conditions that favor N2 fixation in lakes and reservoirs have not been well studied. We measured N2 fixation and lacustrine variables monthly over a 19-month period in Waco Reservoir, Texas, USA, and linked these data with nutrient-loading estimates from a physically based watershed model. Readily available topographic, soil, land cover, effluent discharge, and climate data were used in the Soil and Water Assessment Tool (SWAT) to derive watershed nutrient-loading estimates. Categorical and regression tree (CART) analysis revealed that lacustrine and watershed correlates of N2 fixation were hierarchically structured. Lacustrine conditions showed greater predictive capability temporally. For instance, low NO3(-) concentration (<25 microg N/L) and high water temperatures (>27 degrees C) in the reservoir were correlated with the initiation of N2 fixation seasonally. When lacustrine conditions were favorable for N2 fixation, watershed conditions appeared to influence spatial patterns of N2 fixation within the reservoir. For example, spatially explicit patterns of N2 fixation were correlated with the ratio of N:P in nutrient loadings and the N loading rate, which were driven by anthropogenic activity in the watershed and periods of low stream flow, respectively. Although N2 fixation contributed <5% of the annual N load to the reservoir, 37% of the N load was derived from atmospheric N2 fixation during summertime when stream flow in the watershed was low. This study provides evidence that watershed anthropogenic activity can exert control on planktonic N2 fixation, but that temporality is controlled by lacustrine conditions. Furthermore, this study also supports suggestions that reduced inflows may increase the propensity of N2-fixing cyanobacterial blooms in receiving waters of anthropogenically modified landscapes.     

Relationship between reproductive biology and age composition and growth in Urolophus lobatus (Batoidea: Urolophidae)

The aim of the present study was to use samples, collected by trawling throughout the year along the lower west coast of Australia, to determine the reproductive biology, size and age compositions, and growth rate of Urolophus lobatus, a member of a speciose elasmobranch family (Urolophidae) for which there was previously only a small amount of such data. U. lobatus copulates about 3 months prior to the time when females ovulate, which implies that sperm is stored in the oviducal gland of the female in the intervening period. Gestation lasts for 10 months, which is relatively long for a species that does not grow to a large size. This feature is reflected in the fact that the mean disc width at parturition (105 mm) is equivalent to as much as 44% and 52% of the asymptotic disc widths of the females and males of this species, respectively. The trends exhibited by the marginal increments on vertebral centra demonstrated that each of the translucent zones in these centra is laid down annually and that their numbers can thus be used to age this species. Maturity was attained by about 70% of females and 50% of males at the end of the 4th and 3rd years after conception, respectively, or at just over 3 and 2 years after birth, respectively. Females and males typically first reach maturity at ˜200 and ∼160 mm, respectively, and attained maximal disc widths of 277 and 237 mm, respectively. Females reached maximum ages of 15 years from conception and 14 years from birth, with the corresponding values for males being 13 and 12 years, respectively. Since such a large amount of growth occurs during gestation, von Bertalanffy growth curves were constructed using the date of conception, that is, the fertilisation date, as age 0, as is usually the case with teleosts, as well as employing the birth date as age 0, as is typically the case with elasmobranchs. The growth curves drawn through the points for the disc width-at-age of the older female and male fish gave a slightly better fit when using, as age 0, the parturition date rather than the conception date. However, the asymptotic disc widths derived for females and males using the conception date, that is, 241.3 and 202.9 mm, were each still only 7.6 mm less than those derived using the birth date. Moreover, the fit of the line drawn through the points for the disc width-at-age of fish during gestation was better using the conception date as age 0 than would be achieved by a backwards extrapolation of the growth curve using the birth date as age 0. Received: 6 January 2000 / Accepted: 17 June 2000     

Advanced geophysical underground coal gasification monitoring

Underground Coal Gasification (UCG) produces less surface impact, atmospheric pollutants and greenhouse gas than traditional surface mining and combustion. Therefore, it may be useful in mitigating global change caused by anthropogenic activities. Careful monitoring of the UCG process is essential in minimizing environmental impact. Here we first summarize monitoring methods that have been used in previous UCG field trials. We then discuss in more detail a number of promising advanced geophysical techniques. These methods – seismic, electromagnetic, and remote sensing techniques – may provide improved and cost-effective ways to image both the subsurface cavity growth and surface subsidence effects. Active and passive seismic data have the promise to monitor the burn front, cavity growth, and observe cavity collapse events. Electrical resistance tomography (ERT) produces near real time tomographic images autonomously, monitors the burn front and images the cavity using low-cost sensors, typically running within boreholes. Interferometric synthetic aperture radar (InSAR) is a remote sensing technique that has the capability to monitor surface subsidence over the wide area of a commercial-scale UCG operation at a low cost. It may be possible to infer cavity geometry from InSAR (or other surface topography) data using geomechanical modeling. The expected signals from these monitoring methods are described along with interpretive modeling for typical UCG cavities. They are illustrated using field results from UCG trials and other relevant subsurface operations.     

Air revitalization compounds: A literature survey

Chemical processes for air revitalization are attractive alternatives for some closed life support systems in the applications of space and marine explorations. A review of the literature is given for the purpose of evaluating potential candidates as air revitalizing chemicals based upon a set of criteria including toxicity in use, removal of airborne contaminants and bacteria, theoretical oxygen yields, chemical reactivity to breathing atmospheres, and commercial availability. The preliminary evaluation shows potassium and sodium Superoxides as prime candidates for further evaluation against the practical considerations of actual use. Upon closer scrutiny, potassium Superoxide is the desired chemical for air revitalization in closed life support systems according to the present technology. Kinetic reaction rates for the simple hydration of KO₂ were reported to increase for increasing pressures to 12 atm making it a promising air revitalization chemical at the hyperbaric conditions encountered in deep diving.