Stochastic modelling of landfill leachate and biogas production incorporating waste heterogeneity. Model formulation and uncertainty analysis

A mathematical model simulating the hydrological and biochemical processes occurring in landfilled waste is presented and demonstrated. The model combines biochemical and hydrological models into an integrated representation of the landfill environment. Waste decomposition is modelled using traditional biochemical waste decomposition pathways combined with a simplified methodology for representing the rate of decomposition. Water flow through the waste is represented using a statistical velocity model capable of representing the effects of waste heterogeneity on leachate flow through the waste. Given the limitations in data capture from landfill sites, significant emphasis is placed on improving parameter identification and reducing parameter requirements. A sensitivity analysis is performed, highlighting the model's response to changes in input variables. A model test run is also presented, demonstrating the model capabilities. A parameter perturbation model sensitivity analysis was also performed. This has been able to show that although the model is sensitive to certain key parameters, its overall intuitive response provides a good basis for making reasonable predictions of the future state of the landfill system. Finally, due to the high uncertainty associated with landfill data, a tool for handling input data uncertainty is incorporated in the model's structure. It is concluded that the model can be used as a reasonable tool for modelling landfill processes and that further work should be undertaken to assess the model's performance.     

Successful application of monitored natural attenuation in a surficial aquifer

Groundwater investigations conducted since 1988 at a Tennessee Department of Environment and Conservation (TDEC) Voluntary Oversight and Assistance Program (VOAP) site located in Millington, Tennessee, have defined the lateral and vertical extent of site chemicals of concern (COCs) consisting of tetrachloroethene (PCE), trichloroethene (TCE), and associated degradation products. Results of a groundwater remedial investigation determined that aquifer conditions were favorable for anaerobic degradation of COCs through reductive dechlorination. A subsequent groundwater feasibility study determined that monitored natural attenuation (MNA) coupled with long‐term groundwater monitoring was the most effective and suitable remedial option for the site. A Record of Decision was issued by the TDEC VOAP approving MNA and long‐term groundwater monitoring as the remedial option for the site, a first for such a site in Tennessee involving chlorinated organics. A groundwater fate and transport model (the 1998 model) developed during the RI was used as the basis for the MNA remedy. Analytical data from 1998 to 2008 indicate COCs in former high‐concentration areas continue to degrade at rates consistent with or ahead of the 1998 model predictions. Evidence of reductive dechlorination is also supported by the continued presence of breakdown products—specifically, vinyl chloride and ethene (terminal endpoint of PCE breakdown through reductive dechlorination). The continued detection of breakdown products along the flow‐path wells also confirms the effectiveness of the MNA remedy at the site. Current analytical data indicate that COC plumes beneath the site are not migrating and are actually retracting. © 2010 Wiley Periodicals, Inc.     

How many color metrics do we need? Evaluating how different color-scoring procedures explain carotenoid pigment content in avian bare-part and plumage ornaments

For a variety of technical and conceptual reasons, biologists have come to use several different methods to quantify the colors of animals. However, the relative abilities of these different color-scoring procedures to capture variation in the actual color-generating mechanisms—pigment or structural composition of the integument—have never been tested systematically. Here, we examined which commonly employed color metrics predict carotenoid content of ornaments in three avian species (house finch Carpodacus mexicanus, mallard duck Anas platyrhynchos, and zebra finch Taeniopygia guttata). We used spectrophotometry to measure reflectance spectra from beak and feather tissue, calculated numerous color metrics (e.g., hue, chroma, brightness, principal components, and tetrahedral color space position) from these spectra, and determined carotenoid content at the site of color measurement with high-performance liquid chromatography. We found that several principal component, tristimulus, and avian visual model metrics significantly correlated with carotenoid content of house finch feathers and duck beaks. Carotenoid content of mallard beaks was most closely correlated with brightness and saturation metrics, whereas in house finch feathers, carotenoid concentration was best captured by hue and saturation metrics. According to tristimulus scores and visual models, we found that the ultraviolet portion of the spectrum was not an essential predictor of variation in carotenoid content. Also, visual model chromatic contrasts generally were not significant predictors of carotenoid content, although some achromatic contrasts and tetrahedral color space vector parameters were. Our results indicate that numerous methods, especially tristimulus scores, are suitable for capturing pigment-based color variation in two carotenoid-containing ornaments, and we discuss the merits and shortcomings of these different approaches. In contrast, there were no significant relationships between any color metrics and the carotenoid content of zebra finch beaks, suggesting that other color-generating mechanisms besides carotenoids may contribute to color variability in this species.     

Realising resource efficiency in the management of healthcare waste from the Cornwall National Health Service (NHS) in the UK

The quantities of waste generated by the healthcare sector in the United Kingdom (UK) have been shown to be amongst the highest in Europe. Based on a case study undertaken within the Cornwall NHS (National Health Service) in the UK, this paper reports on the results of waste minimisation trials. The schemes were able to achieve significant waste reductions in both clinical and domestic waste quantities. Indeed, a reduction in domestic bag waste in the range of 1.6-33.4%, with an average of 14.8% was realised. For clinical waste, the reduction ranged from 1.8% to 38.3%, at an average of 15.7%, with net cost benefits of nearly US$ 25,000 over the period of 1-3 years. The outcomes suggest that significant resource and financial efficiencies can be attained, but due to the many factors involved, there is a need to focus both on containment and logistics, as well as social factors for success.     

Adsorption of the quinolone antibiotic nalidixic acid onto anion-exchange and neutral polymers

Pharmaceutical products are being found in surface and ground waters around the world. While the consequences to human health are unknown, it is suspected that these contaminants adversely alter aquatic ecosystems. This study presents adsorption results for one pharmaceutical product, nalidixic acid (NA), on neutral and anion-exchange polymers at three pH values. The adsorption of NA below and above its pKa of approximately 6 on polymers with different matrices, forms, and degrees of polarity were evaluated. By comparing the Freundlich constants KF and n, the results show that the neutral form of NA adsorbs to a greater extent on neutral polymers, and that the anionic form of NA adsorbs more to anion-exchange polymers. Also, results of the adsorption experiments suggest that aromatic ring interactions between NA and the surface of both neutral and anion-exchange polymers are important in the adsorption process. These results have important implications for the treatment of pharmaceutical-contaminated water, as many pharmaceutical contaminants are ionizable and have aromatic rings in their structure. This study illustrates the importance of pH and sorbate and sorbent structure in considering polymer sorption for treatment of pharmaceutical-contaminated aqueous systems.     

Direct-push geochemical profiling for assessment of inorganic chemical heterogeneity in aquifers

Discrete-depth sampling of inorganic groundwater chemistry is essential for a variety of site characterization activities. Although the mobility and rapid sampling capabilities of direct-push techniques have led to their widespread use for evaluating the distribution of organic contaminants, complementary methods for the characterization of spatial variations in geochemical conditions have not been developed. In this study, a direct-push-based approach for high-resolution inorganic chemical profiling was developed at a site where sharp chemical contrasts and iron-reducing conditions had previously been observed. Existing multilevel samplers (MLSs) that span a fining-upward alluvial sequence were used for comparison with the direct-push profiling. Chemical profiles obtained with a conventional direct-push exposed-screen sampler differed from those obtained with an adjacent MLS because of sampler reactivity and mixing with water from previous sampling levels. The sampler was modified by replacing steel sampling components with stainless-steel and heat-treated parts, and adding an adapter that prevents mixing. Profiles obtained with the modified approach were in excellent agreement with those obtained from an adjacent MLS for all constituents and parameters monitored (Cl, NO(3), Fe, Mn, DO, ORP, specific conductance and pH). Interpretations of site redox conditions based on field-measured parameters were supported by laboratory analysis of dissolved Fe. The discrete-depth capability of this approach allows inorganic chemical variations to be described at a level of detail that has rarely been possible. When combined with the mobility afforded by direct-push rigs and on-site methods of chemical analysis, the new approach is well suited for a variety of interactive site-characterization endeavors.     

Photochemical degradation of selected nitropolycyclic aromatic hydrocarbons in solution and adsorbed to solid particles

To examine the relationship between the nitro group orientation and photochemical degradation, a series of NPAHs, including 6-nitrochrysene, 9-nitroanthracene and 6-nitrobenzo(a)pyrene were irradiated both dissolved in CH3CN and adsorbed onto a surface (alumina, silica, carbon and cellulose). In solution, not all NPAHs displayed a relationship between their relative and nitro group orientation. In the adsorbed state, the nature of the particle appeared to have more of an influence than did the structure of the NPAH. If the compound degraded, the main product was generally a quinone.     

Development and testing of a micro wind tunnel for on-site wind erosion simulations

Wind erosion processes affect soil surfaces across all land uses worldwide. Understanding the spatial and temporal scales of wind erosion is a challenging undertaking because these processes are diverse and highly variable. Wind tunnels provide a useful tool as they can be used to simulate erosion at small spatial scales. Portable wind tunnels are particularly valued because erosion can be simulated on undisturbed soil surfaces in the field. There has been a long history of use of large portable wind tunnels, with consensus that these wind erosion simulation tools can meet real world aerodynamic criteria. However, one consequence of striving to meet aerodynamic reality is that the size of the tunnels has increased, making them logistically difficult to work with in the field and resulting in a tendency to homogenise naturally complex soil surfaces. This homogenisation is at odds with an increasing awareness of the importance that small scale processes have in wind erosion. To address these logistical and surface homogenisation issues we present here the development and testing of a micro wind tunnel (MWT) designed to simulate wind erosion processes at high spatial resolution. The MWT is a duct-type design—0.05 m tall 0.1 m wide and with a 1.0 m working section. The tunnel uses a centrifugal motor to suck air through a flow‐conditioning section, over the working section and then through a sediment collection trap. Simulated wind velocities range from 5 to 18 m s^?1, with high reproducibility. Wind speeds are laterally uniform and values of u _* at the tunnel bed (calculated by measuring the pressure gradients within the MWT) are comparable with those of larger tunnels in which logarithmic profiles can be developed. Saltation sediment can be added. The tunnel can be deployed by a single person and operated on slopes ranging from 0 to 10°. Evidence is presented here that the MWT provides new and useful understanding of the erodibility of rangelands, claypans and ore stockpiles.     

Natural attenuation of a plume from an emplaced coal tar creosote source over 14 years

An emplaced source of coal tar creosote within the sandy Borden research aquifer has documented the long-term (5140 days) natural attenuation for this complex mixture. Plumes of dissolved chemicals were produced by the essentially horizontal groundwater flowing at about 9 cm/day. Eleven chemicals have been extensively sampled seven times using a monitoring network of approximately 280, 14-point multilevel samplers. A model of source dissolution using Raoult's Law adequately predicted the dissolution of 9 of 11 compounds. Mass transformation has limited the extent of the plumes as groundwater has flowed more than 500 m, yet the plumes are no longer than 50 m. Phenol and xylenes have been removed and naphthalene has attenuated from its maximum extent on day 1357. Some compound plumes have reached an apparent steady state and the plumes of other compounds (dibenzofuran and phenanthrene) are expected to continue to expand due to an increasing mass flux and limited degradation potential. Biotransformation is the major process controlling natural attenuation at the site. The greatest organic mass lost is associated with the high solubility compounds. However, the majority of the mass loss for most compounds has occurred in the source zone. Oxygen is the main electron acceptor, yet the amount of organics lost cannot be accounted for by aerobic mineralization or partial mineralization alone. The complex evolution of these plumes has been well documented but understanding the controlling biotransformation processes is still elusive. This study has shown that anticipating bioattenuation patterns should only be considered at the broadest scale. Generally, the greatest mass loss is associated with those compounds that have a high solubility and low partitioning coefficients.     

New policies to deal with climate change and other drivers impacting on resilience to flooding in urban areas: the CORFU approach

In the context of urban flood management, resilience is equal to resisting, recovering, reflecting and responding. The variety of causes of flooding and their consequences underpin the need for increased and internationally coordinated efforts to enhance technologies and policies for dealing with floods. This paper addresses this issue and presents some novel research ideas related to resilience to flooding in urban areas, which are under development within the EU FP7 project ‘Collaborative research on flood resilience in urban areas’ (CORFU). The approach adopted in this project aims to quantify the cost-effectiveness of resilience measures and integrative and adaptable flood management plans for different scenarios of relevant drivers: urban development, socio-economic trends and climate changes. It is believed that the way in which the different models are being put together, combined with the variability of conditions in case study areas in Asia and in Europe, will ultimately enable more scientifically sound policies for the management of the consequences of urban flooding.