Hydrocarbon Measurements During the 1992 Southern Oxidants Study Atlanta Intensive: Protocol and Quality Assurance

Abstract

A major component of the Southern Oxidants Study (SOS) 1992 Atlanta Intensive was the measurement of atmospheric nonmethane hydrocarbons. Ambient air samples were collected and analyzed by a network of strategically located automated gas chromatography (GC) systems (field systems). In addition, an extensive canister sampling network was deployed. Combined, more than 3000 chromatograms were recorded. The SOS science team targeted for quantitative analysis 56 compounds which may be substantial contributors to ozone formation or used as air mass tracers. A quality assurance program was instituted to ensure that good measurements were being made throughout the network for each target compound. Common, high-quality standards were used throughout the network. The performance of individual field systems was evaluated during the intensive through the analysis of challenge mixtures. This methodology helped to identify and correct analytical problems as they arose.     

A free-enzyme catalyst for the bioremediation of environmental atrazine contamination

Herbicide contamination from agriculture is a major issue worldwide, and has been identified as a threat to freshwater and marine environments in the Great Barrier Reef World Heritage Area in Australia. The triazine herbicides are of particular concern because of potential adverse effects, both on photosynthetic organisms and upon vertebrate development. To date a number of bioremediation strategies have been proposed for triazine herbicides, but are unlikely to be implemented due to their reliance upon the release of genetically modified organisms. We propose an alternative strategy using a free-enzyme bioremediant, which is unconstrained by the issues surrounding the use of live organisms. Here we report an initial field trial with an enzyme-based product, demonstrating that the technology is technically capable of remediating water bodies contaminated with the most common triazine herbicide, atrazine.     

A convective wind resource model for Solar Vortex power generation

ABSTRACT

Climate change has increased the need for clean, nonpolluting energy sources to decrease dependence on fossil fuels. Alternative energy sources, mainly solar and horizontal wind, have been the primary focus for producing clean energy. New technologies are being developed, such as the Solar Vortex (SoV), which was developed at the Georgia Institute of Technology, and relies on a vertical wind resource to generate power. The National Renewable Energy Lab (NREL) has resource models representing solar and horizontal wind resources across the 48 United States. This research developed a vertical wind resource model that is comparable in resolution to NREL’s solar and horizontal wind resource models and uses the model for estimating power output for the SoV. This model complements NREL’s existing resource models and supports the deployment of an additional clean energy generation technology. The model was applied to Mesa, Arizona to find feasible sites for a small-scale vertical wind farm.     

Reconstruction of radioactive plume characteristics along Chernobyl's Western Trace

Using data obtained from 435 radiation sampling stations in the Red Forest, 1.5 km W if the Chernobyl Nuclear Complex, we reconstructed the deposition pathway of the first plume released by the accident, Chernobyl's Western Trace. The dimensions and deposition rates of the plume remain sharply defined 15 years after the accident. Assuming a uniform particle distribution within the original cloud, we derived estimates of plume dimensions by applying geometric transformations to the coordinates at each sample point. Our derived estimates for the radioactive cloud accounted for 87% of the variation of radioactivity in this region. Results show a highly integrated bell-shaped cross-section of the cloud of radiation, approximately 660 m wide and 290 m high, traveling at a bearing of 264 degrees from reactor IV. Particle sizes within Chernobyl's Western Trace were within the most dangerous range for inhaled aerosols (2-5 microm). Therefore, reconstruction of the dispersion of such particles is critical for understanding the aftermath of nuclear and biological aerosol releases.     

Dairy washwater treatment using a horizontal flow biofilm system

In Ireland, dairy farmyard washwater commonly comprises farmyard run-off and dairy parlour washings. Land-spreading is the most widely used method for treating this wastewater. However, this method can be labour intensive and can cause, in some cases, the degradation of surface and ground waters, mainly due to nitrogen contamination. In this study, a horizontal flow biofilm reactor (HFBR) with step-feed was constructed and tested in the laboratory, to remove organic carbon and nitrogen from a agricultural strength synthetic washwater (SWW). The HFBR had an average top plan surface area (TPSA) of 0.1002 m(2) and consisted of a stack of 45 polystyrene horizontal sheets--15 sheets embedded with 25 mm deep frustums above 30 sheets with 10 mm deep frustums. The frustums acted as miniature reservoirs. The sheets were alternately offset to allow the wastewater to flow horizontally along each sheet and vertically from sheet to sheet down through the reactor. Biofilms developed on the sheets and treated the wastewater. During the 212-d study, the total hydraulic loading rate based on the TPSA of the sheets was 35 l m(-2) d(-1). SWW was pumped for 10 min each hour, in a step feed arrangement at a rate of 23.33 l m(-2) d(-1) on to the top sheet during Phases 1 and 2, and 11.67 l m(-2) d(-1) onto Sheet 16 during Phase 1 (days 1-92) and onto Sheet 30 during Phase 2 (days 93-212). The substrate loading rate during Phases 1 and 2 was 94.8 g total chemical oxygen demand (COD) m(-2) d(-1) and 10.5 g total nitrogen (TN) m(-2) d(-1), based on the TPSA. At steady state in Phase 2, the unit achieved excellent carbon removal of 99.7% 5-day biochemical oxygen demand (BOD(5)) and 96.7% total COD, equivalent to TPSA removal rates of 67.5 g BOD(5)m(-2)d(-1) and 91.7 g COD m(-2) d(-1). The nitrogen removal percentages were 98.3% total ammonium-nitrogen (NH(4)-N(t)) and 72.8% TN, which equated to TPSA removal rates of 4.8 g NH(4)-N(t) m(-2) d(-1) and 7.6g TN m(-2) d(-1). No sloughing of solids or clogging of media occurred during the study. The unit was simple to construct and operate, with little maintenance.     

Constructed wetlands for mitigation of atrazine-associated agricultural runoff

Atrazine was amended into constructed wetlands (59-73x14x0.3 m) for the purpose of monitoring transport and fate of the pesticide to obtain information necessary to provide future design parameters for constructed wetlands mitigation of agricultural runoff. Following pesticide amendment, a simulated storm and runoff event equal to three volume additions was imposed on each wetland. Targeted atrazine concentrations were 0 microg/l (unamended control), 73 microg/l, and 147 microg/l. Water, sediment, and plant samples were collected weekly for 35 days from transects longitudinally distributed throughout each wetland and were analyzed for atrazine using gas chromatography. Between 17 and 42% of measured atrazine mass was within the first 30-36 m of wetlands. Atrazine was below detection limits (0.05 microg/kg) in all sediment and plant samples collected throughout the duration of this study. Aqueous half lives ranged from 16 to 48 days. According to these data, conservative buffer travel distances of 100-280 m would be necessary for effective runoff mitigation.     

A comparative analysis of sperm storage and mating strategies in five species of brachyuran crabs

Variation in female sperm storage is explained, in part, by the amount of sperm transferred at mating. Laboratory mating experiments were conducted on Eurypanopeus depressus and Rhithropanopeus harrisii from the Chesapeake Bay and Pachygrapsus transversus from Florida, while mated pairs of Uca beebei and U. terpsichores were collected from mudflats in Panama. All experiments and collections were conducted during the summer of 2006 and 2007. More sperm was transferred to larger than smaller females, and by species with long copulation durations (R. harrisii and E. depressus). These two species live in cryptic habitats, have high sperm/egg ratios, and likely store sperm across multiple broods. In contrast, P. transversus and U. beebei mate conspicuously, have short copulations, transfer fewer sperm, and have low sperm/egg ratios. Comparisons of sperm transfer across different mating strategies and habitats provide a better understanding of female sperm storage in the Brachyura.     

Projected declines in global DHA availability for human consumption as a result of global warming

Ambio - Docosahexaenoic acid (DHA) is an essential, omega-3, long-chain polyunsaturated fatty acid that is a key component of cell membranes and plays a vital role in vertebrate brain function. The...     

Herbicide effects on typha latifolia (Linneaus) germination and root and shoot development

Aqueous 7-d germination and growth experiments were performed to compare responses of T. latifolia to exposures of atrazine (2-chloro-4-ethylamino-6-isopropylamine-s-atrazine) and paraquat dichloride (1,1′-dimethyl-4,4′-bipyridinium dichloride). T. latifolia seed germination was < 50 % in concentrations ≥ 1.0 mg/L of paraquat dichloride. No observed effect concentration (NOEC) and lowest observed effect concentration (LOEC) for paraquat and root growth were 0.001 and 0.01 mg/L, respectively, while NOEC and LOEC for paraquat and shoot growth were 0.01 and 0.1 mg/L, respectively following 7-d exposures. Greater than 72 % of seeds germinated in each concentration up to 30 mg/L atrazine. After 7-d exposure, NOEC and LOEC for atrazine and root growth were 0.1 and 1.0 mg/L, while atrazine and shoot growth NOEC and LOEC values were 15 and 30 mg/L, respectively. This research provides data concerning relative sensitivity of T. latifolia seedlings to the herbicides atrazine and paraquat, as well as the potential use of T. latifolia as a representative plant test species.