Heterologous expression of <Emphasis Type="Italic">LamA</Emphasis> gene encoded endo-β-1,3-glucanase and CO<Subscript>2</Subscript> fixation by bioengineered <Emphasis Type="Italic">Synechococcus</Emphasis> sp. PCC 7002

The gene for the catalytic domain of thermostable endo-β-1,3-glucanase (laminarinase) LamA was cloned from Thermotoga maritima MSB8 and heterologously expressed in a bioengineered Synechococcus sp. PCC 7002. The mutant strain was cultured in a photobioreactor to assess biomass yield, recombinant laminarinase activity, and CO₂ uptake. The maximum enzyme activity was observed at a pH of 8.0 and a temperature of 70°C. At a CO₂ concentration of 5%, we obtained a maximum specific growth rate of 0.083 h^–1, a biomass productivity of 0.42 g?L^–1?d^–1, a biomass concentration of 3.697 g?L^–1, and a specific enzyme activity of the mutant strain of 4.325 U?mg^–1 dry mass. All parameters decreased as CO₂ concentration increased from 5% to 10% and further to 15% CO₂, except enzyme activity, which increased from 5% to 10% CO₂. However, the mutant culture still grew at 15% CO₂ concentration, as reflected by the biomass productivity (0.26 g?L^–1?d^–1), biomass concentration (2.416 g?L^–1), and specific enzyme activity (3.247 U?mg^–1 dry mass).

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Plants as bio-monitors for Cs-137, Pu-238, Pu-239,240 and K-40 at the Savannah River Site

The Savannah River Site was constructed in South Carolina to produce plutonium (Pu) in the 1950s. Discharges associated with these now-ceased operations have contaminated large areas within the site, particularly streams associated with reactor cooling basins. Evaluating the exposure risk of contamination to an ecosystem requires methodologies that can assess the bioavailability of contaminants. Plants, as primary producers, represent an important mode of transfer of contaminants from soils and sediments into the food chain. The objective of this study was to identify local area plants for their ability to act as bio-monitors of radionuclides. The concentrations of cesium-137 ((137)Cs), potassium-40 ((40)K), (238)Pu and (239,240)Pu in plants and their associated soils were determined using γ and α spectrometry. The ratio of contamination concentration found in the plant relative to the soil was calculated to assess a concentration ratio (CR). The highest CR for (137)Cs was found in Pinus palustris needles (CR of 2.18). The correlation of soil and plant (137)Cs concentration was strong (0.76) and the R(2) (0.58) from the regression was significant (p = 0.006). This suggests the ability to predict the degree of (137)Cs contamination of a soil through analysis of the pine needles. The (238)Pu and (239,240)Pu concentrations were most elevated within the plant roots. Extremely high CR values were found in Sparganium americanum (bur-reed) roots with a value of 5.86 for (238)Pu and 5.66 for (239,240)Pu. The concentration of (40)K was measured as a known congener of (137)C. Comparing (40)K and (137)C concentrations in each plant revealed an inverse relationship for these radioisotopes. Correlating (40)K and (137)Cs was most effective in identifying plants that have a high affinity for (137)Cs uptake. The P. palustris and S. americanum proved to be particularly strong accumulators of all K congeners from the soil. Some species that were measured, warrant further investigation, are the carnivorous plant Utricularia inflata (bladderwort) and the emergent macrophyte Juncus effusus. For U. inflata, the levels of (137)Cs, (238)Pu, and (239,240)Pu (which were 3922, 8399, and 803 Bq kg(-1), respectively) in the leaves were extremely high. The highest (137)Cs concentration from the study was measured in the J. effusus root (5721 Bq kg(-1)).     

Spatial Patterns of Macrobenthic Communities in Shallow-Water Tidal Embayments and Their Association with Environmental Factors

This study examines the distribution, composition, and structure of benthic communities in nine shallow-water semienclosed embayments on Cape Cod, southeastern Massachusetts. The spatial patterns were used to associate benthic characteristics with local environmental factors. Field data from multiple years were collected to measure macrofaunal abundance, community composition, and environmental characteristics. Multivariate statistics were used to analyze the spatial variations of species composition and the abundance of benthic macrofauna. Canonical ordination, specifically redundancy analysis, was used to determine the relative importance of the environmental factors (nutrients and habitat factors) being studied. The analyses demonstrate that the benthic communities in the shallow tidal embayments are clearly clustered in association with the local environments. Species composition and community structure of the benthic macrofauna are significantly correlated with water column parameters, especially with phytoplankton biomass, total nitrogen, and dissolved oxygen.     

Estimating net benefits of recreation under conditions of excess demand

The public provision of outdoor recreation necessitates the development of nonmarket measures of the value of resources in recreational use. Such values can be used as surrogates for market values in the decision-making process. Another aspect of recreation as a publicly provided good is the absence of a mechanism to eliminate automatically excess demand. The absence of such a mechanism has resulted in conditions of excess demand at many recreation sites.This paper deduces the implications of excess demand for the travel cost method of benefit estimation. We show that when excess demand results in rationing at a particular site, the travel cost method will underestimate the true benefits of the site. The results are important because they help identify the direction of bias of one measure of the benefits from the use of a natural resource.     

Plutonium uptake and behavior in vegetation of the desert southwest: a preliminary assessment

Eight species of desert vegetation and associated soils were collected from the Nevada National Security Site (N2S2) and analyzed for 238Pu and 239 + 240Pu concentrations. Amongst the plant species sampled were: atmospheric elemental accumulators (moss and lichen), the very slow growing, long-lived creosote bush and the rapidly growing, short-lived cheatgrass brome. The diversity of growth strategies provided insight into the geochemical behavior and bio-availability of Pu at the N2S2. The highest concentrations of Pu were measured in the onion moss (24.27 Bq kg-1 238Pu and 52.78 Bq kg-1 239 + 240Pu) followed by the rimmed navel lichen (8.18 Bq kg-1 and 18.4 Bq kg-1 respectively), pointing to the importance of eolian transport of Pu. Brome and desert globemallow accumulated between 3 and 9 times higher concentrations of Pu than creosote and sage brush species. These results support the importance of species specific elemental accumulation strategies rather than exposure duration as the dominant variable influencing Pu concentrations in these plants. Total vegetation elemental concentrations of Ce, Fe, Al, Sm and others were also analyzed. Strong correlations were observed between Fe and Pu. This supports the conclusion that Pu was accumulated as a consequence of the active accumulation of Fe and other plant required nutrients. Cerium and Pu are considered to be chemical analogs. Strong correlations observed in plants support the conclusion that these elements displayed similar geochemical behavior in the environment as it related to the biochemical uptake process of vegetation. Soils were also sampled in association with vegetation samples. This allowed for the calculation of a concentration ratio (CR). The CR values for Pu in plants were highly influenced by the heterogeneity of Pu distribution among sites. Results from the naturally occurring elements of concern were more evenly distributed between sample sites. This allowed for the development of a pattern of plant species that accumulated Ce, Sm, Fe and Al. The highest accumulators of these elements were onion moss, lichen flowed by brome. The lowest accumulators were creosote bush and fourwing saltbush. This ranked order corresponds to plant accumulations of Pu.     

The consequences of land use change on nutrient exports: a regional scale assessment in south-west Victoria, Australia

Estimation of nutrient load production based on multi-temporal remotely sensed land use data for the Glenelg-Hopkins region in south-west Victoria, Australia, is discussed. Changes in land use were mapped using archived Landsat data and computerised classification techniques. Land use change has been rapid in recent history with 16% of the region transformed in the last 22 years. Total nitrogen and phosphorus loads were estimated using an export coefficient model. The analysis demonstrates an increase in modelled nitrogen and phosphorus loadings from 1980 to 2002. Whilst such increases were suspected from past anecdotal and ad-hoc evidence, our modelling estimated the magnitude of such increases and thus demonstrated the enormous potential of using remote sensing and GIS for monitoring regional scale environmental processes.     

Photosynthetic responses to temperature, light flux-density, CO2 concentration and vapour pressure deficit in Eucalyptus tetrodonta grown under CO2 enrichment

Seeds of Eucalyptus tetrodonta were sown under ambient or CO(2) enriched (700 microl litre(-1)) conditions in tropical Australia. Four sets of measurements were made, the first two after 12 months, on trees growing either in pots or planted in the ground. The third and fourth set were made after 18 and 30 months exposure to CO(2) enrichment, on trees growing in the ground. After 12 months exposure to CO(2) enrichment, the rate of light-saturated assimilation (Amax) of plants growing in the ground was determined. Responses of CO(2) assimilation to variations in leaf temperature, leaf-to-air vapour pressure deficit (LAVPD), light flux density and CO(2) concentration were also measured in the laboratory using plants growing in large pots. There was no significant difference in Amax between pot and ground located plants. Assimilation of E. tetrodonta was relatively insensitive to changes in LAVPD for both ambient and CO(2) enriched plants but the temperature optimum of assimilation was increased in plants grown and measured under CO(2) enrichment. Plants grown with CO(2) enrichment had an increased rate of light-saturated assimilation and apparent quantum yield was significantly increased by CO(2) enrichment. In contrast, carboxylation efficiency was decreased significantly by CO(2) enrichment. After 18 months growth with CO(2) enrichment, there was no sign of a decline in assimilation rate compared to measurements undertaken after 12 months. At low LAVPD values, assimilation rate was not influenced by CO(2) treatment but at moderate to high LAVPD, plants grown under CO(2) enrichment exhibited a larger assimilation rate than control plants. Specific leaf area and chlorophyll contents decreased in response to CO(2) enrichment, whilst foliar soluble protein contents and chlorophyll a/b ratios were unaffected by CO(2) treatment. Changes in soluble protein and chlorophyll contents in response to CO(2) enrichment did not account for changes in assimilation between treatments. After 30 months exposure to CO(2) enrichment, the rate of light-saturated assimilation was approximately 50% larger than controls and this enhancement was larger than that observed after 18 months exposure to CO(2) enrichment.     

Comparison of two micro-analytical methods for detecting the spatial distribution of sorbed Pu on geologic materials

Subsurface transport of groundwater contaminants is greatly influenced by chemical speciation, precipitation and sorption processes at the mineral-water interface. The retardation of contaminants is often greatest at boundaries between minerals and in fractures and pore spaces. The investigation of the spatial distribution of sorbed contaminants along these boundaries requires micro-analytical techniques. The sorption of dissolved Pu(V) on a natural zeolitic tuff from Yucca Mountain (NV, USA) was examined using microautoradiography (MAR), X-ray diffraction (XRD), electron microprobe (EM) techniques, and synchrotron-based micro-X-ray fluorescence (micro-SXRF). The tuff contained a heterogeneous distribution of zeolites and trace quantities of smectites, Fe oxides (hematite), and Mn oxides (rancieite), which are present as fracture fill and pore space materials. Micro-SXRF studies showed that Pu is mostly associated with bodies of smectite plus Mn oxides, which were typically elevated in Ce, Ga, Nb, Pb, Y, Ca, Ti, and Zn. Sorbed Pu was not associated with Fe-rich bodies, which were enriched in Cl and Rb. Results of the MAR studies were complementary to that of the micro-SXRF studies in that Pu was associated with similar elements in the tuff. Indirect detection of Pu by EM or micro-SXRF (by analyzing Ag developed on the MAR photoemulsion) was a more sensitive method for detecting lower levels of sorbed Pu than the direct detection of sorbed Pu via micro-SXRF in the absence of the photoemulsion.     

Dioxins and polychlorinated biphenyls (PCDD/Fs and PCBs) in food from farms close to foot and mouth disease animal pyres

To control the outbreak of foot and mouth disease, which occurred in the UK in early 2001, a large number of farm animals were slaughtered. Where it was not possible to render or landfill the carcasses, they were destroyed by burning on open pyres, with wood, coal and other materials. Uncontrolled combustion such as this is known to produce small quantities of dioxins and an investigation was made into whether, as a result of the burning, there was an elevation in the concentrations of these compounds in food produced in the areas close to the pyres. With few exceptions, concentrations of PCDD/Fs and PCBs were within the expected ranges as predicted by reference data. No accumulation over time was evident from a repeat milk sampling exercise. Where elevated concentrations of PCDD/Fs and PCBs were found in chickens and eggs, they were in samples not destined for the food chain. Elevated levels in some samples of milk from Dumfries and Galloway were not found in earlier or later samples and may have been found as a result of a temporary feeding regime. Elevated concentrations in lamb from Carmarthenshire were from very young animals which would not have entered the food chain. There was no evidence of any significant increase in dietary exposure to PCDD/Fs and PCBs as a result of the FMD pyres.