165 research outputs found
The biogeochemical control of arsenic in certain estuaries
No full textSemi-continuous hydride generation atomic absorption spectrometry for the analysis of dissolved arsenic speciation in water, was optimised and used to detect sub-nonagram quantities of inorganic arsenic(III) and arsenic(V), monomethylarsenic and dimethylarsenic species in saline waters. High performance liquid chromatography-hydride generation AAS was also developed for the analysis of organoarsenicals in marine macro-algae. The biogeochemical control of arsenic was then studied in two estuarine ecosystems. The temporal speciation of arsenic in Southampton Water (Hampshire U.K.) was monitored and related to planktonic and bacterial activity. The spring and summer depletion of arsenic(V) was associated with the production of methylated and reduced arsenic(III) by marine diatoms and flagellates, but not bacteria. At times up to 50% of the total dissolved arsenic was present in these forms. A UV photodecomposition technique was developed that broke down organoarsenicals that do not form hydrides, such as arsenobetaine, arsenocholine and arsenosugars, to hydride reducible derivatives. This allowed their detection in algal extracts and sea water. Photodecomposition of arsenicals present in Solent water revealed increases of up to 30% in total dissolved arsenic, above that measured by conventional hydride generation; mainly as dimethyl- and inorganic arsenic. The `extra' arsenic showed seasonality and was associated with an abundance of phytoplankton. The other system studied was that of the Tamar, an estuary dominated by non-riverine inputs of arsenic from past mining activity. Surveys revealed two maxima in inorganic arsenic. One derived from mine leachates in the upper reaches, and a second from the release of arsenic-rich porewaters by tidal scouring, in the mudflat dominated mid-estuary. Estuarine particulate material was shown to partially regulate the dissolved level of inorganic arsenic. Methylated arsenic showed no affinity for the suspended sediments.</p
Geographic profiling in Nazi Berlin: fact and fiction
No full textGeographic profiling uses the locations of connected crime sites to make inferences about the probable location of the offender’s ‘anchor point’ (usually a home, but sometimes a workplace). We show how the basic ideas of the method were used in a Gestapo investigation that formed the basis of a classic German novel about domestic resistance to the Nazis during the Second World War. We use modern techniques to re-analyse this case, and show that these successfully locate the Berlin home address of Otto and Elise Hampel, who had distributed hundreds of anti-Nazi postcards, after analysing just 34 of the 214 incidents that took place before their arrest. Our study provides the first empirical evidence to support the suggestion that analysis of minor terrorism-related acts such as graffiti and theft could be used to help locate terrorist bases before more serious incidents occur
Spatial and temporal (annual and decadal) trends of metal(loid) concentrations and loads in an acid mine drainage-affected river
No full textAcid mine drainage (AMD) is a worldwide problem that degrades river systems and is difficult and expensive to remediate. To protect affected catchments, it is vital to understand the behaviour of AMD-related metal(loid) contaminants as a function of space and time. To address this, the sources, loads and transport mechanisms of arsenic (As), copper (Cu), zinc (Zn), iron (Fe) and sulfur (S) in a representative AMD-affected catchment (the Carnon River in Cornwall, UK) were determined over a 12-month sampling period and with 22 years of monitoring data collected by the Environment Agency (England) (EA). The main source of metal(loid)s to the Carnon River was the County Adit which drains AMD from approximately 60 km of underground historical mine workings. Maximum aqueous concentrations of Fe, Cu and Zn occurred immediately downstream of the County Adit confluence with the Carnon River, whereas maximum As and S concentrations occurred further downstream, suggesting the presence of diffuse sources. Discharge and concentration relationships suggested that discharge drove Cu and Zn release, whereas pH and Eh influenced Fe, S, and As mobility. Total loads (represented by unfiltered sample contaminant concentrations) to the coastal zone were high, ranging from 183 to 354 kg/month As, 307–742 kg/month Cu, 189–1960 kg/month Fe, 53,400–125,000 kg/month S and 1280–3320 kg/month Zn. The longevity and increasing amounts of contaminant discharge were confirmed with 22 years of EA monitoring data. This study highlights the complex and multifaceted behaviour of contaminant metal(loid)s within AMD-affected riverine systems and the fact that point and diffuse sources can constitute significant long-term liabilities for such environments
Survey of expectations
No full textThis article presents the results from the February 1993 Reserve Bank of New Zealand Survey of Expectations.
Survey of Expectations
No full textThis article presents the results from the September 1992 Reserve Bank of New Zealand Survey of Expectations
Survey of Expectations
No full textThis article presents the results from the December 1992 quarter Reserve Bank of New Zealand Survey of Expectations.
Assessment of drought impacts on water quantity and quality: Implications for water resources and the Severn Thames Transfer
No full textWater resource management planners are increasingly aware of the effects that climate change and population growth will have on current, conventional water resources management plans. This requires an understanding of the vulnerability and sustainability of the current water supply options and the development of new water resource options to cope with more intense, longer, and more frequent droughts. Water stress in South East England is projected to increase over the next planning horizon, and water planners are continuously looking to develop drought management options with neighbouring water companies to transfer water cross basins to alleviate some of the water stress. The Severn-Thames Transfer is actively discussed as the preferred investment scheme to secure water supply in the Thames basin in the United Kingdom. In terms of inter-basin water transfers, understanding surplus water availability from the donor catchment is a vital factor. Thus thorough exploration of the wide range of extreme events in both donor and receiving catchments must be incorporated into the feasibility assessments. Together with consideration of water quantity resilience in the system, water quality risks associated with mixing two waters must be addressed prior to implementation.
The overarching aim of this research is to provide a comprehensive water quality and quantity modelling representation of the hypothetical inter-basin water transfer scheme under extreme and spatially extensive drought events. The aim is to explore the possible occurrence of trade-offs between water quality and quantity within the proposed transfer scheme. This research utilised state of the art hydro-climatic data alongside hydrological modelling and water quality modelling to achieve this research aim. A new proposed inter-basin transfer scheme, the Severn-Thames Transfer, has been chosen to demonstrate the new modelling framework.
The findings herein suggest the value of the new modelling framework, because of the potential to explore multiple aspects of risks on the new proposed water resources. The methodology used has contributed to an enhanced understanding of catchment specific water quality responses to extreme drought, and enabled the identification of critical water quality variables, which might impose risks during inter-basin water transfers. The use of this case study demonstrated that more spatially extensive and severe droughts are projected under a changing climate, and it will threaten the water supply in London and degrade the water quality in the Thames and Severn Rivers. The results also suggest that inter-basin transfers can degrade water quality although water stress in the Thames basin can be alleviated by increasing supply. Regarding water quality impacts by the suggested transfers, total phosphorus and dissolved organic carbon will be a concern and introduce an additional burden on water supply systems and ecological conditions in the Thames. Reduced nitrate and suspended sediments concentrations are expected in the Thames while transfers as the water quality in lower Severn is better. Therefore, the timing of transfers will become the most critical factor for the new proposed transfer scheme
Elucidating the structural properties that influence the persistence of PCBs in humans using the National Health and Nutrition Examination Survey (NHANES) dataset
No full textIn human exposure studies involving Polychlorinated Biphenyls (PCBs), it is useful to establish when an individual was potentially exposed. Age dating PCB exposure is complex but assessments can be made because different PCB congeners have different residence times in the human body. The less chlorinated congeners generally tend to have shorter residence times because they are biotransformed and eliminated faster than more chlorinated congeners. Therefore, the presence of high proportions of less chlorinated congeners is often indicative of recent exposure. The 2003-04 National Health and Nutrition Examination Survey (NHANES) dataset contains results for the concentration of 37 PCBs in a sub-sample of the US population. Multivariate statistical analysis of the NHANES data showed that less chlorinated congeners are not always biotransformed faster than higher chlorinated compounds. For example, PCB 28 (a tri-chlorobiphenyl) appears to be more resistant to biotransformation than PCB 101 and 110 (penta-chlorobiphenyls). Using statistical analysis of the NHANES data in conjunction with previously published studies on PCB persistence in humans, it was possible to identify the structural relationships that determine if a PCB is likely to be from a recent exposure (termed 'episodic') or from steady state exposure. Congeners with chlorine atoms in the 2,5- and 2,3,6-positions appear to be more susceptible to biotransformation whereas congeners with chlorine bonds in the 2,3,4- 2,4,5- 3,4,5- and 2,3,4,5-positions appear to be more persistent. This work shows that future investigations to date PCB exposure would benefit from the analysis of a wide range of congeners, including the selection of key congeners based not only on the degree of chlorination but also on the positions of the chlorine atoms on the biphenyl.</p
Fingerprinting polychlorinated biphenyls in environmental samples using comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry
No full textA GC × GC-TOFMS installed with a Rtx-PCB (60 m × 0.18 mm × 0.18 μm) in the first dimension and Rxi- 17 (1.5 m × 0.1 mm × 0.1 μm) column in the second dimension was used to separate 188 out of 209 congeners. A further 12 congeners were identified through additional data processing resulting in the identification of a total of 200 congeners. However, caution is advised if these 12 congeners were to be used in quantitative assessments. The remaining 9 co-eluting congeners were three doublets (CB65 + CB62, CB160 + CB163 and CB201 + CB204) and one triplet (CB20 + CB21 + CB33). This method was tested on five Aroclors and resulted in the separation of all congeners present in the heavier Aroclor mixtures A1254 and A1260. The suitability of this method for applications in biological matrices was demonstrated on extracted whiting and guillemot liver samples which resulted in the identification of 137 individual PCBs in the whiting liver sample and 120 in the guillemot sample. Fingerprinting was able to show clear differences in the PCB signature of the two animals. This highlights the potential of this method for PCB fingerprinting in environmental forensics studies and other assessments that require congener specific analysis
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