Watermains leakage and outdoor water use are responsible for significant phosphorus fluxes to the environment across the United States

Human activity has led to excess phosphorus (P) concentrations and the continued eutrophication of coastal and freshwaters across the United States (US). Developing more effective P management policy requires a comprehensive understanding of P sources in the environment. Public water systems across the United States widely dose water with phosphate (PO4) in order to control the corrosion of lead and copper within their distribution networks. Using public water system PO4 dosing facility data and target PO4-P dosing concentrations, we estimate that PO4 dosing added 4–14.9 kt PO4-P yr−1 into the US water distribution network in 2015. Using estimates of public water supply inputs and domestic water deliveries, we estimate that 0.7–2.6, and 0.8–3.1 kt PO4-P yr−1 were then lost from the network due to watermains leakage and outdoor water use, respectively. After accounting for these fluxes, we estimate that 9.3 kt PO4-P yr−1 was then returned to wastewater treatment plants (WWTPs) and accounted for up to 2.7% of the national WWTP influent P load. As sources of P to the environment, lower and upper estimates of combined watermains leakage and outdoor water use PO4-P fluxes exceeded P loads to surface waterbodies from documented point sources across 461–541 counties. The exceedance of these fluxes above other major components of the US P-budget emphasizes the need to include them in P source apportionment studies, both across the US and in other countries where public water supplies are dosed with PO4

A Spectroscopic Survey of WNL Stars in the LMC: General Properties and Binary Status

We report the results of an intense, spectroscopic survey of all 41 late-type, nitrogen-rich Wolf-Rayet (WR) stars in the Large Magellanic Cloud (LMC) observable with ground-based telescopes. This survey concludes the decade-long effort of the Montr\'eal Massive Star Group to monitor every known WR star in the Magellanic Clouds except for the 6 crowded WNL stars in R136, which will be discussed elsewhere. The focus of our survey was to monitor the so-called WNL stars for radial-velocity (RV) variability in order to identify the short- to intermediate-period (P \la 200 days) binaries among them. Our results are in line with results of previous studies of other WR subtypes, and show that the binary frequency among LMC WNL stars is statistically consistent with that of WNL stars in the Milky Way. We have identified four previously unknown binaries, bringing the total number of known WNL binaries in the LMC to nine. Since it is very likely that none but one of the binaries are classical, helium-burning WNL stars, but rather superluminous, hence extremely massive, hydrogen-burning objects, our study has dramatically increased the number of known binaries harbouring such objects, and thus paved the way to determine their masses through model-independent, Keplerian orbits. It is expected that some of the stars in our binaries will be among the most massive known. With the binary status of each WR star now known, we also studied the photometric and X-ray properties of our program stars using archival MACHO photometry as well as Chandra and ROSAT data. We find that one of our presumably single WNL stars is among the X-ray brightest WR sources known. We also identify a binary candidate from its RV variability and X-ray luminosity which harbours the most luminous WR star known in the Local Group.Comment: 25 pages, 11 figures; accepted for MNRA

Groundwater origami: folding paper models to visualize groundwater flow

The training of geological scientists, more so than any other natural science, is dependent on how students learn to visualize and interpret complex three-dimensional problems at scales from micrometers to kilometers over time scales that span from seconds to centuries. Traditionally, our classrooms are at a disadvantage due to our standard two-dimensional use of whiteboards or slide decks. We are at an even bigger disadvantage when courses go to online education. While computer simulations and three-dimensional visualizations are used, they can lack the flexibility for students to perform free-form exploration. The novelty of this research is in the use of paper aquifer models and their implementation across seven academic institutions to provide three-dimensional physical examples for students to visualize subsurface geologic structure and quantify fluid flow through porous media. Students can cut, fold, and build three-dimensional hydrologic problems at home or in the classroom. Our methodology allows students to physically rotate their aquifer models to visualize cross-sectional areas, layer thicknesses, heterogeneity, and confining units. These foldable paper models provide a low barrier of entry for students to understand and quantify the relationships between water levels and geologic structure. Our experience using these models in both in-person and online classrooms highlights the advantages and disadvantages of these models. Results, although mostly anecdotal, suggest the paper models improve students’ learning and enhance their engagement with the material. The formal evaluations of pre- and post-model implementation show that low-scoring students had the most significant gains after being introduced to the paper aquifer models. At the same time, there was no change in the number of students in the highest scoring group. Our experience in the classroom points to new opportunities to engage with remote learners and tools for supporting flipped classroom activities. Our vision for the paper aquifer models is to provide the hydrologic community with an additional tool to help bridge the virtual classroom gap, engage students, and help them develop mastery of three-dimensional problem-solving

Bostonia: The Boston University Alumni Magazine. Volume 9

Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs

Is there a compact companion orbiting the late O-type binary star HD 164816?

We present a multi-wavelength (X-ray, $\gamma$-ray, optical and radio) study of HD 194816, a late O-type X-ray detected spectroscopic binary. X-ray spectra are analyzed and the X-ray photon arrival times are checked for pulsation. In addition, newly obtained optical spectroscopic monitoring data on HD 164816 are presented. They are complemented by available radio data from several large scale surveys as well as the \emph{FERMI} $\gamma$-ray data from its \emph{Large Area Telescope}. We report the detection of a low energy excess in the X-ray spectrum that can be described by a simple absorbed blackbody model with a temperature of $\sim$ 50 eV as well as a 9.78 s pulsation of the X-ray source. The soft X-ray excess, the X-ray pulsation, and the kinematical age would all be consistent with a compact object like a neutron star as companion to HD 164816. The size of the soft X-ray excess emitting area is consistent with a circular region with a radius of about 7 km, typical for neutron stars, while the emission measure of the remaining harder emission is typical for late O-type single or binary stars. If HD 164816 includes a neutron star born in a supernova, this supernova should have been very recent and should have given the system a kick, which is consistent with the observation that the star HD 164816 has a significantly different radial velocity than the cluster mean. In addition we confirm the binarity of HD 164816 itself by obtaining an orbital period of 3.82 d, projected masses $m_1 {\rm sin}^{3} i$ = 2.355(69) M$_\odot$, $m_2 {\rm sin}^{3} i$ = 2.103(62) M$_\odot$ apparently seen at low inclination angle, determined from high-resolution optical spectra.Comment: Accepted for publication by MNRAS, 11 pages, 6 figures, 4 table

Retardation of arsenic transport through a Pleistocene aquifer

Groundwater drawn daily from shallow alluvial sands by millions of wells over large areas of south and southeast Asia exposes an estimated population of over a hundred million people to toxic levels of arsenic. Holocene aquifers are the source of widespread arsenic poisoning across the region. In contrast, Pleistocene sands deposited in this region more than 12,000 years ago mostly do not host groundwater with high levels of arsenic. Pleistocene aquifers are increasingly used as a safe source of drinking water and it is therefore important to understand under what conditions low levels of arsenic can be maintained. Here we reconstruct the initial phase of contamination of a Pleistocene aquifer near Hanoi, Vietnam. We demonstrate that changes in groundwater flow conditions and the redox state of the aquifer sands induced by groundwater pumping caused the lateral intrusion of arsenic contamination more than 120 metres from a Holocene aquifer into a previously uncontaminated Pleistocene aquifer. We also find that arsenic adsorbs onto the aquifer sands and that there is a 16–20-fold retardation in the extent of the contamination relative to the reconstructed lateral movement of groundwater over the same period. Our findings suggest that arsenic contamination of Pleistocene aquifers in south and southeast Asia as a consequence of increasing levels of groundwater pumping may have been delayed by the retardation of arsenic transport

Constraints on the χ_(c1) versus χ_(c2) polarizations in proton-proton collisions at √s = 8 TeV

The polarizations of promptly produced χ_(c1) and χ_(c2) mesons are studied using data collected by the CMS experiment at the LHC, in proton-proton collisions at √s=8  TeV. The χ_c states are reconstructed via their radiative decays χ_c → J/ψγ, with the photons being measured through conversions to e⁺e⁻, which allows the two states to be well resolved. The polarizations are measured in the helicity frame, through the analysis of the χ_(c2) to χ_(c1) yield ratio as a function of the polar or azimuthal angle of the positive muon emitted in the J/ψ → μ⁺μ⁻ decay, in three bins of J/ψ transverse momentum. While no differences are seen between the two states in terms of azimuthal decay angle distributions, they are observed to have significantly different polar anisotropies. The measurement favors a scenario where at least one of the two states is strongly polarized along the helicity quantization axis, in agreement with nonrelativistic quantum chromodynamics predictions. This is the first measurement of significantly polarized quarkonia produced at high transverse momentum