The Spatial and Temporal Variability of Airborne Pollutants in Stormwater Runoff

Atmospheric deposition is increasingly being recognised as a significant source of total suspended solids (TSS) and heavy metals in urban runoff. However, many uncertainties and challenges remain with measuring and managing these pollutants in runoff. Impermeable concrete boards were deployed in a residential, industrial, and airside land-use area in Christchurch for almost one year in 2013 to determine the spatial and temporal variability of airborne pollutant loads (principally TSS, Cu, Pb, and Zn) in runoff. Results showed that each land-use area displayed similar trends of increasing/decreasing pollutant loads throughout the monitoring period, suggesting that the pollutants originated from a similar source. Consistently higher pollutant loads were found for the industrial area, which was attributed to local topographic conditions rather than land-use activity. All pollutants had a statistically significant relationship with antecedent dry days, illustrating its importance on pollutant build-up. Pollutants dominated by their particulate-phase were influenced by peak rainfall intensity, which was explained by the energy from an intense rainfall event dislodging more particulate pollutants; however, this relationship was weak. Dissolved-phased pollutants displayed a greater relationship to rain depth showing that the quantity of rain influences the dissolution of pollutants from a surface

'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

The contribution of wet deposition and particulate matter to total copper, lead and zinc in stormwater runoff

Wet deposition is an important process in the removal of heavy metal particulates from the atmosphere. However, the contribution of wet deposition to the total heavy metal deposition flux can vary widely between different airsheds. Understanding the contribution of wet deposition to the total metal deposition flux is important for accurate knowledge of local atmospheric deposition processes, which will subsequently help in the selection of appropriate stormwater treatment and management options. This research monitored Cu, Zn and Pb loads in wet deposition samples and in bulk deposition samples from modular concrete paving slab systems. In conjunction, ambient particulate matter (PM) concentrations were monitored to determine their contribution to the wet deposition flux. All research was conducted in an industrial land-use area in Christchurch, New Zealand. Results showed that wet deposition efficiently removed PM from the atmosphere, but after 1–2.5 antecedent dry days, PM concentrations recovered. Subsequent antecedent dry days, i.e > 1–2.5 d, did not influence PM concentrations. Pb loads in wet deposition were dependent on coarse PM (size range between 2.5 μm and 10 μm) concentrations. This suggested that there was a local source emitting coarse Pb particles into the atmosphere. Wet deposition was an important contributor of dissolved Zn to bulk deposition. However, dry deposition was the greatest source of total Cu, Zn, and Pb loads in bulk deposition. This is principally due to the low annual rainfall in Christchurch, which limits pollutant removal via wet deposition unlike dry deposition, which is continually occurring

Projected WIMP sensitivity of the LUX-ZEPLIN dark matter experiment

LUX-ZEPLIN (LZ) is a next-generation dark matter direct detection experiment that will operate 4850 feet underground at the Sanford Underground Research Facility (SURF) in Lead, South Dakota, USA. Using a two-phase xenon detector with an active mass of 7 tonnes, LZ will search primarily for low-energy interactions with weakly interacting massive particles (WIMPs), which are hypothesized to make up the dark matter in our galactic halo. In this paper, the projected WIMP sensitivity of LZ is presented based on the latest background estimates and simulations of the detector. For a 1000 live day run using a 5.6-tonne fiducial mass, LZ is projected to exclude at 90% confidence level spin-independent WIMP-nucleon cross sections above 1.4 × 10-48cm2 for a 40 GeV/c2 mass WIMP. Additionally, a 5σ discovery potential is projected, reaching cross sections below the exclusion limits of recent experiments. For spin-dependent WIMP-neutron(-proton) scattering, a sensitivity of 2.3 × 10−43 cm2 (7.1 × 10−42 cm2) for a 40 GeV/c2 mass WIMP is expected. With underground installation well underway, LZ is on track for commissioning at SURF in 2020

The Galactic Faraday rotation sky 2020

Galaxie

Search for Neutrinos in Super-Kamiokande Associated with the GW170817 Neutron-star Merger

We report the results of a neutrino search in Super-Kamiokande (SK) for coincident signals with the first detected gravitational wave (GW) produced by a binary neutron-star merger, GW170817, which was followed by a short gamma-ray burst, GRB170817A, and a kilonova/macronova. We searched for coincident neutrino events in the range from 3.5 MeV to ~100 PeV, in a time window ±500 s around the gravitational wave detection time, as well as during a 14-day period after the detection. No significant neutrino signal was observed for either time window. We calculated 90% confidence level upper limits on the neutrino fluence for GW170817. From the upward-going-muon events in the energy region above 1.6 GeV, the neutrino fluence limit is ${16.0}_{-0.6}^{+0.7}$ (${21.3}_{-0.8}^{+1.1}$) cm−2 for muon neutrinos (muon antineutrinos), with an error range of ±5° around the zenith angle of NGC4993, and the energy spectrum is under the assumption of an index of −2. The fluence limit for neutrino energies less than 100 MeV, for which the emission mechanism would be different than for higher-energy neutrinos, is also calculated. It is 6.6 × 107 cm−2 for anti-electron neutrinos under the assumption of a Fermi–Dirac spectrum with average energy of 20 MeV

Scintillator ageing of the T2K near detectors from 2010 to 2021

The T2K experiment widely uses plastic scintillator as a target for neutrino interactions and an active medium for the measurement of charged particles produced in neutrino interactions at its near detector complex. Over 10 years of operation the measured light yield recorded by the scintillator based subsystems has been observed to degrade by 0.9–2.2% per year. Extrapolation of the degradation rate through to 2040 indicates the recorded light yield should remain above the lower threshold used by the current reconstruction algorithms for all subsystems. This will allow the near detectors to continue contributing to important physics measurements during the T2K-II and Hyper-Kamiokande eras. Additionally, work to disentangle the degradation of the plastic scintillator and wavelength shifting fibres shows that the reduction in light yield can be attributed to the ageing of the plastic scintillator. The long component of the attenuation length of the wavelength shifting fibres was observed to degrade by 1.3–5.4% per year, while the short component of the attenuation length did not show any conclusive degradation

The DUNE far detector vertical drift technology. Technical design report

DUNE is an international experiment dedicated to addressing some of the questions at the forefront of particle physics and astrophysics, including the mystifying preponderance of matter over antimatter in the early universe. The dual-site experiment will employ an intense neutrino beam focused on a near and a far detector as it aims to determine the neutrino mass hierarchy and to make high-precision measurements of the PMNS matrix parameters, including the CP-violating phase. It will also stand ready to observe supernova neutrino bursts, and seeks to observe nucleon decay as a signature of a grand unified theory underlying the standard model. The DUNE far detector implements liquid argon time-projection chamber (LArTPC) technology, and combines the many tens-of-kiloton fiducial mass necessary for rare event searches with the sub-centimeter spatial resolution required to image those events with high precision. The addition of a photon detection system enhances physics capabilities for all DUNE physics drivers and opens prospects for further physics explorations. Given its size, the far detector will be implemented as a set of modules, with LArTPC designs that differ from one another as newer technologies arise. In the vertical drift LArTPC design, a horizontal cathode bisects the detector, creating two stacked drift volumes in which ionization charges drift towards anodes at either the top or bottom. The anodes are composed of perforated PCB layers with conductive strips, enabling reconstruction in 3D. Light-trap-style photon detection modules are placed both on the cryostat's side walls and on the central cathode where they are optically powered. This Technical Design Report describes in detail the technical implementations of each subsystem of this LArTPC that, together with the other far detector modules and the near detector, will enable DUNE to achieve its physics goals

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