'Appreciating' Drainage Assets in New Zealand Cities: Rain Garden Treatment and Hydraulic Performance

Despite recognising rain gardens as a best management practice (BMP) to mitigate urban stormwater runoff, there is a dearth of knowledge about their treatment and infiltration performance. It is believed that organic substrates may enhance some contaminant removal but hinder hydraulic throughput although data showing this is sparse. In order to evaluate the influence of substrate composition on bioinfiltrative system effectiveness, mesocosm-scale (180 L, 0.17 m2) laboratory rain gardens were established. Saturated (constant head) hydraulic conductivity was determined before and after the experimental treatment tests that employed stormwater collected from a neighbouring catchment to investigate contaminant removal efficiencies. The principal contaminant (Zn, Cu, Pb and nutrients) removal efficiencies were investigated for three substrates comprising various proportions of organic topsoil. All total metal concentrations in the effluent were <50% of influent concentrations, with the exception of copper in the topsoil-only system that had negligible reduction due to a high dissolved fraction. The system comprising topsoil only had the lowest saturated hydraulic conductivity of 162 mm/hr and demonstrated the poorest metal (Cu, Zn) removal efficiencies. Interestingly, the system with a combination of sand and topsoil demonstrated most promising metal removal of Cu (53%), Zn (81.2%) and Pb (89.1%) with adequate hydraulic performance (296 mm/hr) required for a stormwater infiltrative system. Overall, metal removal was greater at an effluent pH of 7.38 compared to the 6.24 pH provided in the raw stormwater. Some pH buffering was provided by the calcareous sand in two of the systems, whereas the topsoil-only system lacked such buffering potential to facilitate adequate metal removal. These data highlight the influence of organic topsoil on pH that clearly governs metal speciation and hence removal efficacy in bioinfiltrative systems. Nitrate was net exported from all the systems, especially topsoil contrary to what is believed to be easily removed

Experimental investigation of high strain-rate, large-scale crack bridging behaviour of z-pin reinforced tapered laminates

Significant research exists on small-scale, quasi-static failure behaviour of Z-pinned composite laminates. However, little work has been conducted on large-scale, high strain-rate behaviour of Z-pinned composites at structural level. Small-scale testing is often at an insufficient scale to invoke the full crack bridging effects of the Z-pins. Full-scale testing on real components involves large length scales, complex geometries and resulting failure mechanisms that make it difficult to identify the specific effect of Z-pins on the component failure behaviour. A novel cantilever soft body impact test has been developed which is of sufficient scale to invoke large-scale delamination, such that behaviour in Z-pin arrays at high strain-rates can be studied. Laminates containing Z-pin arrays were subjected to soft-body gelatine impact in high-speed light gas-gun tests. Detailed fractographic investigation was carried out to investigate the dynamic failure behaviour of Z-pins at the microscopic scale

Experimental investigation of large-scale high-velocity soft-body impact on composite laminates

High-performance aerospace laminated composite structures manufactured from carbon-fibre prepreg are very susceptible to delamination failure under in-flight impact conditions. Much testing has been conducted at small length scales and quasi-static strain-rates to characterise the delamination performance of different material systems and loading scenarios. Testing at this scale and strain-rate is not representative of the failure conditions experienced by a laminate in a real impact event. Full-scale testing has also been conducted, but much of this is not in the open literature due to intellectual property constraints. Testing at this scale is also prohibitively expensive and involves complex failure mechanisms that cause difficulty in the analysis of associated failure behaviour. A novel test is presented which provides a simple, affordable alternative to full-scale testing but which invokes failure at sufficient scale and velocity to be representative of real component failure. This test design is experimentally validated through a series of soft-body gelatine impact tests using a light gas-gun facility. A fractographic analysis using scanning-electron microscopy was undertaken to examine microscopic failure behaviour, showing a possible reduction in crack mode-ratio during propagation

Can forest management based on natural disturbances maintain ecological resilience?

Given the increasingly global stresses on forests, many ecologists argue that managers must maintain ecological resilience: the capacity of ecosystems to absorb disturbances without undergoing fundamental change. In this review we ask: Can the emerging paradigm of natural-disturbance-based management (NDBM) maintain ecological resilience in managed forests? Applying resilience theory requires careful articulation of the ecosystem state under consideration, the disturbances and stresses that affect the persistence of possible alternative states, and the spatial and temporal scales of management relevance. Implementing NDBM while maintaining resilience means recognizing that (i) biodiversity is important for long-term ecosystem persistence, (ii) natural disturbances play a critical role as a generator of structural and compositional heterogeneity at multiple scales, and (iii) traditional management tends to produce forests more homogeneous than those disturbed naturally and increases the likelihood of unexpected catastrophic change by constraining variation of key environmental processes. NDBM may maintain resilience if silvicultural strategies retain the structures and processes that perpetuate desired states while reducing those that enhance resilience of undesirable states. Such strategies require an understanding of harvesting impacts on slow ecosystem processes, such as seed-bank or nutrient dynamics, which in the long term can lead to ecological surprises by altering the forest's capacity to reorganize after disturbance

Invited review: Sustainability of the US dairy industry

The US dairy industry has realized tremendous improvements in efficiencies and milk production since the 1940s. During this time, farm and total cow numbers have decreased and average herd size has increased. This intensification, combined with the shift to a largely urban public, has resulted in increased scrutiny of the dairy industry by social and environmental movements and increased concern regarding the dairy industry's sustainability. In response to these concerns, a group of scientists specializing in animal welfare, nutrient management, greenhouse gas emissions, animal science, agronomy, agricultural engineering, microbiology, and economics undertook a critical review of the US dairy industry. Although the US dairy system was identified as having significant strengths, the consensus was that the current structure of the industry lacks the resilience to adapt to changing social and environmental landscapes. We identified several factors affecting the sustainability of the US dairy industry, including climate change, rapid scientific and technological innovation, globalization, integration of societal values, and multidisciplinary research initiatives. Specific challenges include the westward migration of milk production in the United States (which is at odds with projected reductions in precipitation and associated limitations in water availability for cattle and crops), and the growing divide between industry practices and public perceptions, resulting in less public trust. Addressing these issues will require improved alignment between industry practices and societal values, based upon leadership from within the industry and sustained engagement with other interested participants, including researchers, consumers, and the general public

Preparing Better Engineers: Compulsory Undergraduate Research Projects that Benefit Universities and the Profession

Engineers are responsible for creative, innovative and adaptive designs that solve challenging technical problems and provide sustainable solutions. Professional skills (i.e. management, social/cultural appreciation, budgeting, communication and personal development) are recognised by the profession as an integral part of an engineer’s formal education. However, most engineering programmes do not specifically teach these skill sets. We recognised the need to better prepare students for real-world engineering practice that demands innovation and professional skills as well as technical competence. We therefore developed a successful model in which engineering students integrated technical information and professional skills through a real-world research project established in partnership with industry. Material taught throughout a four-year curriculum culminated in the compulsory (equivalent to ~8 credit hours) assessed research project that acts as a pathway towards real-world and sustainable engineering practice. A uniqueness of our model included indigenous people’s cultural engagement, where students were taught the importance of understanding and working with indigenous peoples for successful engineering outcomes. The final year student research project benefited the university, students, industry, and the engineering profession at different levels through financial and other gains. The University and its students acquired industry funding, sponsorship, scholarships, graduate employment and research partnerships. Industry and the profession profited from better prepared engineering students, early recruitment opportunities, company marketing and cost-effective taxdeductible research partnerships. To successfully implement compulsory undergraduate research projects, support from colleagues and the profession is necessary. While financial and personnel resources are limited in times of economic uncertainty, we have mitigated these limitations by partnering with external mentors

Temporal and spatial build-up of heavy metal contaminants in car parks

An innovative experimental system was developed to quantify contaminant loads, determine their temporal and spatial variability, and obtain large data sets required for developing contaminant build-up and wash-off stormwater modeling functions for car parks

Geospatially web-interfaced telemetric monitoring system to track contaminant transport

Analyzing contaminant loading from individual storm runoff events is expensive and often insufficient for realistic catchment-modelling predictions. We developed a near real-time telemetric monitoring system that measures base and storm flow and contaminant transport on a campus waterway. The monitoring system was implemented using a mesh network of radio transmitters linked to environmental sensors. This costeffective system is equipped with in-stream sensors for monitoring discharge, turbidity, temperature, dissolved oxygen, pH and conductivity. A coupled weather station provides complementary data including rainfall intensity, duration, droplet size, temperature, and other climatic parameters. Data are relayed through the wireless network and logged onto an online computer, which is interfaced to Google maps on a dedicated web portal. An automatic sampler can also be added to the system to provide programmed sampling to track event driven contamination. Continuous water quality and discharge monitoring is helping to refine our modelling predictions of contaminant loading to urban waterways and is being extended to trigger an alert system when significant contaminant transport occurs. Supplementary metal analysis of baseflow water and in-stream sediments is revealing insight into contaminant transport and fate in a unique hydro-ecosystem that is actually dependent on contaminated water for flow

An Innovative Method for Spatial Quantification of Contaminant Buildup and Wash-off from Impermeable Urban Surfaces

A method was developed that employs thin boards (0.56 m2) comprising different paving materials (2 asphalt types and concrete) typically used in urban environments. Boards can be placed at various locations of interest within an urban catchment to investigate accumulation of contaminants over specified periods of time. Boards are then placed under a rainfall simulator in order to generate runoff under controlled conditions. We successfully applied this method to investigate contaminant build-up at a University carpark, showing accumulation mainly occurred within the first 6 days. Resulting wash-off curves were used to determine coefficients for build-up and wash-off functions (maximum build-up, half-saturation time and wash-off coefficient) that can be applied to model the fate of contaminants in stormwater models (e.g. SWMM). Results also showed that concentrations of total suspended solids (TSS) are linearly correlated with total metal concentrations

The limits of local politics Local socialism and the local economy in the 1980s; a case study of Sheffield's economic policies

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