Biodegradation of drilling fluid used in South McMurdo Sound, Antarctica

Advisors: Melissa E. Lenczewski.Committee members: Justin Dodd; Mike Konen.The Antarctic Geological Drilling (ANDRILL) researchers obtained a rock core from below the sea-floor in South McMurdo Sound (SMS), Antarctica. During the core retrieval, approximately 5.6 x105 liters of drilling fluid was lost in the subsurface. The loss of this fluid, which contained biodegradable components, may significantly alter the in situ microbial ecology as well as the geochemistry of the subsurface. The introduction of drilling fluid into the subsurface can be viewed as a source of contamination. However, it also provides the opportunity to indirectly study the microbial communities of the subsurface through analyses of the return drilling fluids. This study focused on the differences between new (uncirculated) fluids and the return drilling fluids circulated at depth, along with the chemical and microbial changes that took place during the biodegradation of drilling fluid. Drilling fluid samples were incubated for forty days at 4, 20 and 50°C representing the in situ temperatures, under aerobic and anaerobic conditions. Geochemical analyses were completed and microbial community fingerprints were constructed and compared. The return fluids show significant differences in the geochemistry compared to the new fluids specifically in regards to the ions Barium, Thallium, Lead, Manganese, Iron, and Boron. The return drilling fluids have higher DNA concentrations than the new fluids counterparts within the first four days of the biodegradation experiment. The use of Biolog Ecoplates(TM) revealed that microbes in the return fluids utilized significantly less carbon substrates than those in the new fluids. RAPD-PCR results showed the return fluids exhibited significantly less diversity and species evenness than the microbes in the new fluids. DNA concentrations fluctuated over time, with a direct relationship among fluid type. There are shifts in the community structure and function as biodegradation occurs that varies between the different incubation environments. In situ temperatures ≤4°C were recorded for the top ~21 meters of the borehole. In anaerobic environments and temperatures ≤4°C, slower microbial metabolism may increase the residence time of the biodegradable drilling fluid components, allowing these components the opportunity to penetrate further into the surrounding formation through conduits. The 20°C temperatures recorded at ~360-~384 mbsf may be the most favorable conditions for the biodegradation of the drilling fluids allowing the least amount of migration of the biodegradable components into the surrounding formation. At a depth of ~1026 mbsf, 50°C in situ borehole temperatures were recorded. From this depth through to the final depth of ~1139 mbsf and 57°C, the higher temperatures may result in smaller microbial populations that are able to metabolize the drilling fluid, leading to further drilling fluid migration into the surrounding formation.M.S. (Master of Science

Small-Scale Trials Suggest Increasing Applications of Natular™ XRT and Natular™ T30 Larvicide Tablets May Not Improve Mosquito Reduction in Some Catch Basins

Stormwater catch basins are commonly treated with larvicides by mosquito control agencies to reduce local populations of mosquito species capable of transmitting West Nile virus. Recent evidence suggests that extended-release larvicides formulated to last up to 180 days in catch basins may not be effective in some basins due to chronic flushing, rapid dissolution, or burying of treatment in sump debris. To investigate if increasing the number of applications could improve effectiveness, a small study was performed over 13 weeks in 2015 to evaluate two extended-release larvicides (Natular ™ XRT 180-day tablets and Natular ™ T30 30-day tablets) and a larvicide oil (CocoBear ™ ). Over the course of 13 weeks, three groups of eight basins were monitored for mosquitoes, each group receiving Natular ™ XRT, Natular ™ T30, or CocoBear ™ larvicides. All basins received a single application at the beginning of the study period. Once mosquitoes in a basin surpassed the treatment threshold during weekly monitoring, an additional application of the associated larvicide was given to that basin. The number of applications during the study period ranged from 1 to 10 for CocoBear ™ basins, 1 to 7 for T30 basins, and 2 to 8 for XRT basins. Overall, the average number of applications and the cost of larvicide per basin were 4.4 applications at $0.66 per CocoBear ™ basin, 4.4 applications at$6.26 per T30 basin, and 4 applications at $16.56 per XRT basin. Basins treated with XRT and T30 needed reapplications more often than expected, yet were no more effective than CocoBear ™ , suggesting that increasing the frequency of application of these larvicide formulations may not provide increased mosquito reduction in some basins

Continuation of high-dose vancomycin despite nephrotoxicity

10.1128/AAC.00240-12Antimicrobial Agents and Chemotherapy5663470-3471AMAC

Identification of Larvicide-Resistant Catch Basins from Three Years of Larvicide Trials in a Suburb of Chicago, IL

The tens of thousands of catch basins found in many urban areas are a primary target of local vector control agencies for seasonal application of extended-release larvicides. A concern with using larvicides in these structures is that active ingredients can be hampered by high flows, debris, and sediment, all of which are common to these structures. As such a certain proportion of basins may be “resistant” to larvicide treatments due to site specific characteristics that may promote these and other factors that hinder larvicide action and/or promote mosquito infestation. Analyses from three years of larvicide efficacy trials suggest that over a quarter of basins in the study area may not be receiving adequate protection from a single dose of larvicide that is routinely applied. Implications of increasing the dose and/or toxicity of larvicide treatments are discussed further

Observed Loss and Ineffectiveness of Mosquito Larvicides Applied to Catch Basins in the Northern Suburbs of Chicago IL, 2014

In the northeastern part of the greater Chicago metropolitan area, the North Shore Mosquito Abatement District (NSMAD) treats approximately 50,000 catch basins each season with larvicide tablets as part of its effort to reduce local populations of the West Nile virus (WNV) vector Culex pipiens . During the 2014 season, an NSMAD technician monitored a subset of 60–195 basins weekly for 18 weeks among the communities of the District for the presence of mosquitoes. Monitoring found no clear evidence in the reduction of mosquitoes with the use of larvicides, and visual inspections of 211 larvicide-treated basins found that the majority (162, 76.8%) were missing tablets 1–17 weeks after applications. This loss of treatment may be due to the rapid dissolution or flushing of larvicides and would help explain why the larvicide appeared to be ineffective

Variable Efficacy of Extended-release Mosquito Larvicides Observed in Catch Basins in the Northeast Chicago Metropolitan Area

Since the mid-1990s, the North Shore Mosquito Abatement District (NSMAD) has applied extended-release formulations of mosquito larvicides to approximately 50,000 catch basins in the suburbs north of Chicago, IL, USA. This is performed as part of NSMAD's efforts to reduce local populations of the West Nile virus vector, Culex pipiens. Analyses from NSMAD's monitoring of larvicide-treated basins throughout the District over the 2014 and 2015 seasons suggest that larvicides intended to provide extended durations of control (30-180 days) failed to provide control for the maximum duration specified on the product label in approximately 25% of the District's basins. For larvicides designed to last up to 180 days (or about 26 weeks), failures were found at 1-15 weeks after treatment with most found at five weeks posttreatment. For larvicides formulated to last up to 30 days, failures were found at one to four weeks after applications with most found at three weeks posttreatment. The highest percentages of failing basins (ie, containing late-stage mosquito larvae or pupae during the specified product effectiveness period) were found in communities on the eastern side of the District, bordering Lake Michigan. As the larvicides appeared to function properly in the majority of monitored basins, it appears that the failures likely resulted from basin-specific physical factors (ie, basin volume, sediment content, and hydrology) that cause either product removal or a reduction in the concentration of the larvicide's active ingredient below the effective levels in these basins