The impact on receiving waters of pharmaceutical residues and antibiotic resistant faecal bacteria found in urban waste water effluents

Pharmaceuticals intended for human use are frequently detected in the aquatic environment. This is predominantly from their excretion following ingestion and subsequent discharge in domestic sewage. Wastewater treatment provides an opportunity to control their release to surface waters however, their removal is often incomplete. This thesis addresses this pharmaceutical pathway and the potential impact on the aquatic environment. The progress of bezafibrate, carbamazepine, ciprofloxacin and clarithromycin were monitored through the treatment stages (screened sewage, settled sewage and final effluent) of a large urban wastewater treatment plant (WWTP) and in surface waters up-stream and down-stream of the effluent discharge point. All except clarithromycin were detected in the screened sewage (369 – 2696 ng/L). Reductions in the pharmaceutical concentrations throughout the WWTP (22.5 – 94.3 %) indicate the removal of these compounds is variable. Bezafibrate and carbamazepine were observed at higher concentrations (67.5 - 305.5 ng/L) in surface water down-stream of the effluent discharge point compared to up-stream (31.0 – 116.7 ng/L). The presence of antibiotics in the environment may contribute to the dissemination of antibiotic resistance. The second part of this thesis monitors the prevalence of resistant faecal bacteria through WWTPs and in surface waters. Determination of antibiotic minimum inhibitory concentration (MIC) values for E.coli and E.faecium indicated that the WWTP did not influence the proportions of the resistant bacterial species. Elevated levels of E.coli with acquired ciprofloxacin resistance increased from not detectable in surface waters up-stream to 9.3% down-stream of the WWTP discharge point. The need for standardisation of the interpretation of MIC data is addressed. The potential of ciprofloxacin within surface water to select for ciprofloxacin resistant E.coli were investigated through microcosm studies in the third part of this study. A significant increase (p < 0.05) in the level of resistant E.coli was observed in microcosms exposed to ≥ 5 μg/L ciprofloxacin. At the ciprofloxacin levels typically detected in surface waters receiving treated effluent (<300 ng/L), the levels of resistance amongst E.coli were maintained

Crossover between Levy and Gaussian regimes in first passage processes

We propose a new approach to the problem of the first passage time. Our method is applicable not only to the Wiener process but also to the non--Gaussian L$\acute{\rm e}$vy flights or to more complicated stochastic processes whose distributions are stable. To show the usefulness of the method, we particularly focus on the first passage time problems in the truncated L$\acute{\rm e}$vy flights (the so-called KoBoL processes), in which the arbitrarily large tail of the L$\acute{\rm e}$vy distribution is cut off. We find that the asymptotic scaling law of the first passage time $t$ distribution changes from $t^{-(\alpha +1)/\alpha}$-law (non-Gaussian L$\acute{\rm e}$vy regime) to $t^{-3/2}$-law (Gaussian regime) at the crossover point. This result means that an ultra-slow convergence from the non-Gaussian L$\acute{\rm e}$vy regime to the Gaussian regime is observed not only in the distribution of the real time step for the truncated L$\acute{\rm e}$vy flight but also in the first passage time distribution of the flight. The nature of the crossover in the scaling laws and the scaling relation on the crossover point with respect to the effective cut-off length of the L$\acute{\rm e}$vy distribution are discussed.Comment: 18pages, 7figures, using revtex4, to appear in Phys.Rev.

Desynchronization in diluted neural networks

The dynamical behaviour of a weakly diluted fully-inhibitory network of pulse-coupled spiking neurons is investigated. Upon increasing the coupling strength, a transition from regular to stochastic-like regime is observed. In the weak-coupling phase, a periodic dynamics is rapidly approached, with all neurons firing with the same rate and mutually phase-locked. The strong-coupling phase is characterized by an irregular pattern, even though the maximum Lyapunov exponent is negative. The paradox is solved by drawing an analogy with the phenomenon of ``stable chaos'', i.e. by observing that the stochastic-like behaviour is "limited" to a an exponentially long (with the system size) transient. Remarkably, the transient dynamics turns out to be stationary.Comment: 11 pages, 13 figures, submitted to Phys. Rev.

The fate of bezafibrate, carbamazepine, ciprofloxacin and clarithromycin in the wastewater treatment process

The progress of four pharmaceuticals (bezafibrate, carbamazepine, clarithromycin and ciprofloxacin) is followed through the treatment stages (screened sewage, settled sewage and final effluent) of a large urban wastewater treatment plant (WWTP) employing activated sludge treatment. Concentrations at the inlet to the WWTP are generally higher than those predicted from consideration of local pharmaceutical consumption and typical excretion data. Percentage removal efficiencies are variable (22.5 – 94.3%) with carbamazepine being the most resistant to elimination

Sources and pathways for pharmaceuticals in the urban water environment

The progress of five pharmaceutical compounds (bezafibrate, carbamazepine, diclofenac, ibuprofen and sulfasalazine) and one antibacterial agent (triclosan) were monitored through the treatment stages of a large sewage treatment works (STW) using activated sludge as well as in the receiving water both upstream and downstream of the effluent discharge. All except sulfasalazine were detected in the influent at concentrations ranging from 1.44-3.75 µg/L. The analysis of prescription data has been used as a tool to predict the amount of pharmaceuticals potentially released into the catchment of the investigated sewage treatment works and the results compared with the measured influent concentrations. A reduction in concentration between influent and final effluent samples (51-97%) indicates the variable removal of these compounds and therefore their potential to be discharged into receiving surface waters. The analysis of primary and final effluents highlight the important processes involved in the removal of pharmaceuticals and indicate that sorption processes are important for bezafibrate, carbamazepine and diclofenac. These three PPCPs were observed at higher concentrations (0.07-0.35 µg/L) downstream of the discharged effluent compared to upstream (0.02-0.04 µg/L) although the risks that these compounds pose in the environment are not yet fully understood

Twentieth century increase in snowfall in coastal West Antarctica

The Amundsen Sea sector of the West Antarctic ice sheet has been losing mass in recent decades; however, long records of snow accumulation are needed to place the recent changes in context. Here we present 300 year records of snow accumulation from two ice cores drilled in Ellsworth Land, West Antarctica. The records show a dramatic increase in snow accumulation during the twentieth century, linked to a deepening of the Amundsen Sea Low (ASL), tropical sea surface temperatures, and large-scale atmospheric circulation. The observed increase in snow accumulation and interannual variability during the late twentieth century is unprecedented in the context of the past 300 years and evidence that the recent deepening of the ASL is part of a longer trend

Developing Well Adapted Early to Midseason Cultivars of Trifoiloum subterraneum ssp. Brachycalycinum

Development and selection of early to midseason cultivars of subterranean clover (Trifolium subterraneum L.) ssp. brachycalycinum has mostly involved the use of early generation selection nursery swards (F2-progeny method). Four sites were sown in the mid-North region of South Australia. At the end of 1995, the top 20 lines from each site had burrs (seed pods) sampled at random. The burr will proceed into the final early generation selection phase (1 - 2 years). Dependent on the site, many lines have out-performed the standard checkplot cultivar, Clare. High hardseed levels have also been incorporated into 1989 crossbreds

Ice drilling on Skytrain Ice Rise and Sherman Island, Antarctica

AbstractTo understand the long-term climate and glaciological evolution of the ice sheet in the region bordering the Weddell Sea, the British Antarctic Survey has undertaken a series of successful ice core projects drilling to bedrock on Berkner Island, James Ross Island and the Fletcher Promontory. A new project, WACSWAIN, seeks to increase this knowledge by further drilling to bedrock on two further ice rises in this region. In a single-season project, an ice core was recovered to bedrock at 651 m on Skytrain Ice Rise using an ice core drill in a fluid-filled borehole. In a second season, a rapid access drill was used to recover ice chips to 323 m on Sherman Island in a dry borehole, though failing to reach the bedrock which was at an estimated depth of 428 m.Royal Society ER

Continuous flow analysis methods for sodium, magnesium and calcium detection in the Skytrain ice core

AbstractDissolved and particulate sodium, magnesium and calcium are analyzed in ice cores to determine past changes in sea ice extent, terrestrial dust variability and atmospheric aerosol transport efficiency. They are also used to date ice cores if annual layers are visible. Multiple methods have been developed to analyze these important compounds in ice cores. Continuous flow analysis (CFA) is implemented with instruments that sample the meltstream continuously. In this study, CFA with ICP-MS (inductively coupled-plasma mass spectrometry) and fast ion chromatography (FIC) methods are compared for analysis of sodium and magnesium. ICP-MS, FIC and fluorescence methods are compared for analysis of calcium. Respective analysis of a 10 m section of the Antarctic WACSWAIN Skytrain Ice Rise ice core shows that all of the methods result in similar levels of the compounds. The ICP-MS method is the most suitable for analysis of the Skytrain ice core due to its superior precision (relative standard deviation: 1.6% for Na, 1.3% for Mg and 1.2% for Ca) and sampling frequency compared to the FIC method. The fluorescence detection method may be preferred for calcium analysis due to its higher depth resolution (1.4 cm) relative to the ICP-MS and FIC methods (~4 cm).European Research Counci