Sources In Close Proximity Research Articles

Adaptive quantum state estimation for two optical point sources

In classical optics, there is a well-known resolution limit called Rayleigh's curse in the separation of two incoherent optical sources in close proximity. Recently, Tsang [] revealed that this difficulty may be circumvented in the framework of quantum theory. Following their work, various estimation methods have been proposed to overcome Rayleigh's curse, but none of them enables us to estimate the positions of two point sources simultaneously based on single-photon measurements with high accuracy. In this study, we propose a method to estimate the positions of two point sources with the highest accuracy using an adaptive quantum state estimation scheme. ©2024 American Physical Society 2024 American Physical Society

Electromagnetic near-field mutual coupling suppression with active Janus sources

Electric dipoles and magnetic dipoles are the most fundamental particles in electromagnetic theory. Huygens and Janus sources, formed by the orthogonal combination of electric and magnetic dipoles, both show good directionality in the near field. Although the Huygens source has been widely used in antennas and metasurfaces, the applications of Janus source are heretofore limited. In this paper we report the physical construction of an active Janus source. Through full-wave simulations within the parallel plate waveguide (PPW) environment, we show that our source achieves the directional electromagnetic near-field and quasi-isotropic far-field requisite of the Janus source. Using this fact, we demonstrate that two active Janus and Huygens sources in close proximity (about 0.10 to 0.25 wavelengths) achieve a near 1000-fold reduced mutual coupling compared to electric dipole sources. Particularly, the simultaneous achievement of strong mutual coupling suppression and quasi-isotropic radiation make the Janus source an ideal candidate for consideration in future compact multi-input multi-output (MIMO) communication systems.

Time-series quasi-dynamic load flow analysis with seasonal load variation to resolve energy nexus for a practical distribution network in Puducherry smart grid system incorporating harmonic analysis and mitigation

Time-series quasi-dynamic load flow analysis is an important methodology to estimate the voltage profiles across various nodes in modern distribution networks. This paper describes the necessity of time-series load flow analysis (LFA) for a real-time power distribution network in Puducherry smart grid system by considering seasonal load variations in the union territory of Puducherry, India to obtain optimal performance. In this study, this load flow analysis has been applied to test systems such as IEEE 69, IEEE 37, IEEE 34 and the Indian utility 29 node distribution network (IU29NDN) in Puducherry smart grid system with unbalanced load patterns and energy sources in close proximity. Modified Decision Making (MDM) algorithm is proposed in this paper to improve voltage profiles with in distribution networks by choosing the size and location of solar photovoltaic (SPV) systems. The variations in the node voltages, real power, and reactive power flows are estimated for distribution networks subjected to seasonal load variations by quasi-dynamic load flow simulations conducted over a period of 24 h with 15-minute step size. Furthermore, a harmonic power flow is illustrated and extended to mitigate the harmonics by optimal placement of shunt capacitors (SCs) in all the test systems by incorporating MDM algorithm.

The suitability of isotopic methods in identifying water sources of a shallow-rooted herbaceous plant in a desert steppe

Isotopic methodologies have gained prominence in investigating the composition of plant water sources; however, concerns regarding their suitability and reliability in diverse environments have emerged in recent years. This study presents a comparative analysis of root, soil, and liquid water (precipitation, dew, and groundwater) samples obtained from a desert steppe using isotope ratio infrared spectrometry (IRIS) and isotope ratio mass spectrometry (IRMS). The objective was to evaluate the applicability of these techniques in discerning the water sources of Stipa breviflora, a shallow-rooted herbaceous plant species. Additionally, we explored the root water uptake characteristics and water use strategy of S. breviflora. Our findings indicate that the IRIS method had more enriched values of D compared to the IRMS method across all samples, while no discernible pattern was observed for 18O. Notably, the differences observed among all samples exceeded the instruments' accuracies. Moreover, an unexpected occurrence was noted, whereby both D and 18O values in the root water were more enriched than in any of the considered water sources, rendering identification of the plant water sources unattainable. By conducting a re-analysis of more refined soil layer samples, we discovered that S. breviflora exhibits the ability to absorb and utilize water sources in close proximity to the soil surface. It further suggested that the shallow-rooted herbaceous plants in desert steppes can exploit small rainfalls, frequently overlooked in their ecological importance. Considering the distinctive soil and plant characteristics of desert steppes, we recommend adopting IRMS methods in conjunction with refined surface soil sampling for isotopic analysis aiming to identify water sources of shallow-rooted herbaceous plants. This study provides novel insights into assessing the suitability of isotopic techniques for analyzing plant water sources, while enhancing our understanding of water use strategies and environmental adaptation mechanisms employed by shallow-rooted herbaceous plants within xerophytic grassland ecosystems.

Monitoring and quantifying CO2emissions of isolated power plants from space

Abstract. Top-down CO2 emission estimates based on satellite observations are of great importance for independently verifying the accuracy of reported emissions and emission inventories. Difficulties in verifying these satellite-derived emissions arise from the fact that emission inventories often provide annual mean emissions, while estimates from satellites are available only for a limited number of overpasses. Previous studies have derived CO2 emissions for power plants from the Orbiting Carbon Observatory-2 and 3 (OCO-2 and OCO-3) satellite observations of their exhaust plumes, but the accuracy and the factors affecting these emissions are uncertain. Here we advance monitoring and quantifying point source carbon emissions by focusing on how to improve the accuracy of carbon emission using different wind data estimates. We have selected only isolated power plants for this study, to avoid complications linked to multiple sources in close proximity. We first compared the Gaussian plume model and cross-sectional flux methods for estimating CO2 emission of power plants. Then we examined the sensitivity of the emission estimates to possible choices for the wind field. For verification we have used power plant emissions that are reported on an hourly basis by the Environmental Protection Agency (EPA) in the US. By using the OCO-2 and OCO-3 observations over the past 4 years we identified emission signals of isolated power plants and arrived at a total of 50 collocated cases involving 22 power plants. We correct for the time difference between the moment of the emission and the satellite observation. We found the wind field halfway the height of the planetary boundary layer (PBL) yielded the best results. We also found that the instantaneous satellite estimated emissions of these 50 cases, and reported emissions display a weak correlation (R2=0.12). The correlation improves with averaging over multiple observations of the 22 power plants (R2=0.40). The method was subsequently applied to 106 power plant cases worldwide and yielded a total emission of 1522 ± 501 Mt CO2 yr−1, estimated to be about 17 % of the power sector emissions of our selected countries. The improved correlation highlights the potential for future planned satellite missions with a greatly improved coverage to monitor a significant fraction of global power plant emissions.

Simulation-Based Considerations on the Rayleigh Criterion in Super-Resolution Techniques Based on Speckle Interferometry

This study sought to explain the physical phenomenon that eludes the constraints of the Rayleigh criterion in the microstructure observation method using speckle interferometry, for which super-resolution has been experimentally proven; the study was conducted using computer simulations. Separating the light from two light sources in close proximity, which exceeded the Rayleigh criterion under incoherent light, was believed to be impossible. The simulation results, however, showed that when coherent light is used, the separation of two close points is not necessarily impossible if the light phases between the two points are different. Furthermore, the resolution of microstructure observation techniques based on speckle interferometry was discussed. A new interpretation of the Rayleigh criterion in super-resolution techniques based on speckle interferometry was reported.

Survey of per- and polyfluoroalkyl substances (PFAS) in surface water collected in Pensacola, FL

As the persistence of per- and polyfluoroalkyl substances (PFAS) become a global concern, information about the occurrence and characteristics of PFAS in estuarine and marine ecosystems is poorly represented. In this study, the presence of 51 PFAS were monitored in the Pensacola Bay System (PBS), Florida, USA. Due to the presence of many potential PFAS sources in close proximity to the PBS (e.g., military bases, industries, airports and several firefighting stations), the distribution and concentration of PFAS in this estuarine environment provides insights into the fate of these complex compounds as well as the possible impacts on coastal systems. Surface water was collected and analyzed from 45 different sites via Strata-X-AW cartridge extractions and ultra-high pressure liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) analysis. Recoveries for many PFAS (13/51) were >60% (mean 77 %), with relative standard deviations below 20%, except for N-methylperfluoro-1-octanesulfonamidoacetic acid (N-MeFOSAA) (22%). Of the perfluoroalkyl carboxylic acids (PFCAs), which comprised the majority of PFAS detected: perfluorooctanoic acid (PFOA) and perfluorohexanoic acid (PFHxA) were present in all samples; however, perfluoropentanoic acid (PFPeA) was the individual PFAS with the highest concentration of this group (51.9 ng.L−1, at site 81). The PFAS detected at the highest concentrations were perfluoroalkyl sulfonic acids (PFSA), with perfluorooctane sulfonic acid (PFOS) having the highest detected concentration (269 ng.L−1, at site 81). At all sites, at least eight or more PFAS were quantified. Past and current use of PFAS-containing materials and their fate in areas surrounding military bases, airports, and industries, require more in-depth monitoring efforts to better determine the need for regulation, management, and/or remediation. Here, sites located close to areas suspected of PFAS use had elevated concentrations. For example, one coastal location near an airfield had a ΣPFAS of 677 ng.L−1. Expansion from these ongoing efforts will focus on assessment of PFAS-related effects in local wildlife and evaluating the distribution of PFAS at these “hotspot” sites during large episodic weather events, a critically understudied phenomenon regarding PFAS and vulnerable coastal environments.

Thermal Diffusion Films with In-Plane Anisotropy by Aligning Carbon Fibers in a Cellulose Nanofiber Matrix.

For highly efficient heat dissipation of thin electronic devices, development of film materials that exhibit high thermal conductivity in the in-plane direction is desired. In particular, it is important to develop thermally conductive films with large in-plane anisotropy to prevent thermal interference between heat sources in close proximity and to cool in other directions by diffusion. In this study, we developed flexible composite films composed of a uniaxially aligned carbon-fiber filler within a cellulose nanofiber matrix through liquid-phase three-dimensional patterning. The film exhibited a high in-plane thermal conductivity anisotropy of 433%, with combined properties of a thermal conductivity of 7.8 W/mK in the aligned direction and a thermal conductivity of 1.8 W/mK in the in-plane orthogonal direction. This remarkable thermal conductivity and in-plane anisotropy showed the ability to significantly cool powder electroluminescent devices formed on the composite film and also to cool two heat sources in close proximity without thermal interference. In addition, the carbon-fiber filler could be extracted from the composite films by heat treatment at 450 °C and reused as a thermally conductive material.

Modelling of ducted noise sources in the proximity of acoustic liners

This paper focuses on modelling and predicting the acoustic field generated by ducted point sources in close proximity to an acoustic liner. Two analytical models are presented. The first model comprises a point monopole or dipole source in an infinite lined duct based on an existing Green’s function. The predictions are compared with classic solutions for a source over an infinite lined plane and with a high frequency asymptotic duct approximation. The second model extends the Green’s function to include a liner section of finite length connected to hard-wall extensions by using mode-matching techniques. The new model features the inclusion of point sources in the vicinity of an impedance discontinuity. The accuracy of this model is demonstrated by comparison with reference FE solutions. Both models indicate a significant impact of the source proximity to the liner surface in the source power output. These models offer insight on the source modification effects beyond the conventional approach in the design of liners solely based on acoustic absorption.

Vegetation water sources in California's Sierra Nevada (USA) are young and change over time, a multi‐isotope (δ18O, δ2H, 3H) tracer approach.

AbstractSierra Nevada forests transpire a significant amount of California's water resources, sparking interest in applying forest management to improve California's water supply. Determining the source water of evapotranspiration enables forest managers to make informed decisions. To this end, a significant interest in critical zone science is to develop new methods to work across time scales to predict subsurface water storage and use. In this study, forest vegetation accessed young water and switched sources depending on availability, suggesting that forest drought vulnerability may depend on the range of water sources available (rain, snowmelt and deeply stored water). This finding also suggests that changes in transpiration rates may have immediate effects on water sources in close proximity to vegetation, and delayed effects on storage and runoff. New δ18O, δ2H and 3H data were used to track precipitation, runoff, evapotranspiration and storage through the critical zone seasonally, including seasons where evapotranspiration and snowmelt were in phase (winter snowmelt) and out of phase (seasonally dry summer). The main source of this headwater catchment's runoff is derived from its meadow saturated zone water, which was dominated by snowmelt. Water that originated as snowmelt contributed to transpiration, unless other sources, such as recent rain, became available. In cases where xylem δ18O and δ2H signatures matched those of deeper saturated zone water, 3H data showed that xylem water was distinctly younger than the deep saturated zone water. During 2016, which experienced relatively normal snowpack in winter and seasonally dry summer conditions, mean summer saturated zone water and vegetation water were similar in δ18O, −12.4 ± 0.04 ‰ and − 12.5 ± 0.3 ‰, respectively, but were distinctly different in 3H, 5.5 ± 0.2 pCi/L and 13.7 ± 1.1 pCi/L, respectively. While δ18O shows that vegetation and meadow saturated zone water have similar origins, 3H shows they have dissimilar ages.

Ambient air quality data reported at Sasol Secunda monitoring stations during COVID-19 lockdown – Mpumalanga, South Africa

Various local and international research has been published on the effects of COVID-19 lockdown on ambient air quality. In most cases, a reduction in ambient NOx and PM concentrations have been observed with varying changes in ambient SO2 levels. Secunda, located in the Highveld Priority Area in Mpumalanga, South Africa is known for its large industrial facilities utilising coal as primary feedstock. The towns of Secunda and eMbalenhle provide the majority of the workforce to Sasol and has therefore been the focus of this study. The ambient air quality in the Secunda region was assessed due to the changes in human behaviour during lockdown, familiarity with the Sasol facility and the strategic locations of ambient air quality stations.Results show a clear decrease in ambient CO, NO2 and PM concentrations, especially during the first two weeks of lockdown. Only subtle changes were observed for ambient H2S and SO2 pollutant concentrations at the ambient monitoring stations. An increasing trend in all ambient species was observed towards the end and post lockdown, in contrast to declining ambient temperatures with the onset of winter. This is also contrary to the reduction in emissions from the factory that conducted annual maintenance in the month following lockdown (phase shutdown). This article concludes that human behaviour has a material local ambient impact on CO, NO2 and PM pollutant species, while H2S concentration profiles are more directly related to the industrial complex’s levels of activity. Ambient SO2 trends did not show a similar correlation with the facility’s activities (as H2S), but a stronger correlation was observed with the diverse local and regional sources in close proximity to Secunda and eMbalenhle. The influence of better dispersion especially on a local scale, brought about by more effective emission heights, is considered material. Moreover, meteorological factors, on local air quality, has been shown to be a material contributor to observed ambient air quality levels in the study domain

Sparsity-promoting least-squares interferometric migration for high-resolution passive source location

Seismic source localization plays an important role in estimating the hypocenter of earthquakes and in monitoring hydraulic fracturing. Interferometric crosscorrelation migration (ICCM) is one of the most important waveform-based source location methods that produces a source image from interstation crosscorrelations without manual picking. However, the ICCM method suffers from blurring of the source image, especially for cases in which the acquisition aperture is limited, receivers are sparsely distributed, and the data signal-to-noise ratio is too low. As a result, it typically cannot resolve sources in close proximity to each other, whereas distinguishing them might be a desired feature when we want to follow the fracture evolution in space and time. One possible solution is by fitting a source distribution function to the observed interstation crosscorrelations by least-squares minimization, where the source distribution function is a source power-spectral density (PSD) defined as a function of frequency and spatial location. However, this least-squares interferometric crosscorrelation migration (LS-ICCM) approach provides limited resolution improvement compared to the ICCM method. To further improve the image resolution, we have adopted a sparsity-promoting interferometric crosscorrelation migration (SP-ICCM) method that negates the effects of unfocused sources during the inversion. This sparsity constraint is imposed on the source PSD in space to mitigate the loss of resolution that arises as a consequence of incomplete information, including limited aperture and discretization. The inverse problem involving this sparsity constraint can be solved relatively quickly with an iteratively reweighted least-squares algorithm. Using synthetic and field data tests, we demonstrate that our method is robust to noise and effective for closely spaced sources in complex geologic settings.

Agricultural sources as major supplies of atmospheric phosphorus to Lake Kinneret

Phosphorus (P) deposition through the atmosphere to fresh water bodies is a major supply pathway and, in some cases, can accelerate eutrophication processes. However, the quantification of atmospheric P fluxes to lakes is often not well established and the major P sources are generally poorly recognized. Here we present measurements of the atmospheric P deposition flux of two consecutive years in two sampling stations around Lake Kinneret, a large fresh water body in Northern Israel and quantified the dust daily P load emitted from 14 potential source sites upwind to the lake that include agricultural soils, pasture lands, livestock feeding zone sites and uncultivated lands. In addition, we analyzed phosphate oxygen isotopes (δ18OP) in the deposited dust and in surface material from potential P sources around the lake such as cultivated and uncultivated soils, cow manure and compost. The mean daily dust P deposition to the lake ranged from 150 to 770 μg P m−2 day−1, which accounts for ca. 5%–35% of the P concentrations in the lake water during summer. Dust deposition showed strong daily and monthly variations that were not associated with wind speed alone, indicating that local anthropogenic disturbances have a major control over the daily dust P flux. Simultaneous measurements of atmospheric P in different locations upwind to Lake Kinneret shows that the bulk of the P originated from sources in close proximity to the lake, with negligible P transported from distal sources. Quantification of the atmospheric P load emitted from potential sources upwind to the lake indicate that the highest daily loads of P are emitted from livestock feeding zone sites, probably because of a continuous accumulation of P in these soils. δ18OP values (ranging from 19.1‰ to 24.8‰) in deposited dust samples were significantly different than the values reported for natural soils, coal combustion and airborne tree pollen but in the in the same range as the values found for surface samples taken from agricultural lands fertilized with phosphate fertilizer, compost or cow manure or from uncultivated soils nearby, probably contaminated by agricultural P from nearby sites. Overall, our results show that deposition of dust originating from agricultural sources in close proximity to the lake supply substantial quantities of P to Lake Kinneret. Based on our results we suggest that when considering atmospheric P inputs to fresh water bodies more attention should be paid to land use in sites which are located upwind to the lake basin.

Drift-Alfvén fluctuations and transport in multiple interacting magnetized electron temperature filaments

The results of a basic electron heat transport experiment using multiple localized heat sources in close proximity and embedded in a large magnetized plasma are presented. The set-up consists of three biased probe-mounted crystal cathodes, arranged in a triangular spatial pattern, that inject low energy electrons along a strong magnetic field into a pre-existing, cold afterglow plasma, forming electron temperature filaments. When the three sources are activated and placed within a few collisionless electron skin depths of each other, a non-azimuthally symmetric wave pattern emerges due to interference of the drift-Alfvén modes that form on each filament’s temperature gradient. Enhanced cross-field transport from chaotic ( $\boldsymbol{E}\times \boldsymbol{B}$ , where $\boldsymbol{E}$ is the electric field and $\boldsymbol{B}$ the magnetic field) mixing rapidly relaxes the gradients in the inner triangular region of the filaments and leads to growth of a global nonlinear drift-Alfvén mode that is driven by the thermal gradient in the outer region of the triangle. Azimuthal flow shear arising from the emissive cathode sources modifies the linear eigenmode stability and convective pattern. A steady-current model with emissive sheath boundary predicts the plasma potential and shear flow contribution from the sources.

Temporal and source assessments of organic and elemental carbon at sites in the northern South African interior

Particulate matter (PM) can affect climate, air quality, human health, acid deposition and visibility, and contain a significant fraction of organic (OC) and elemental carbon (EC). Southern Africa is an important source region for OC and EC, however, little OC and EC data have been published for this region. This paper presents a multi-year, multi-site (an urban-industrial site in the Vaal Triangle, UI-VT; an industrially influenced site at Amerfoort, iI-AF; and two regional background sites at Skukuza and Louis Trichardt, RR-SK and RR-LT) PM with an aerodynamic diameter ≤ 2.5 μm (PM2.5) OC and EC dataset for South Africa. The median OC (9.3) and EC (3.2 μg.m−3) concentrations at UI-VT were 1.3 to 2.5 and 2.7 to 4.4 times higher, if compared to the other sites. OC/EC ratios indicated that sources in close proximity to UI-VT were likely the main contributors, while sources that are more distant contributed fractionally more at the other sites. Household combustion for space heating and regional open biomass burning contributed to elevated levels during the cold and dry months at UI-VT. Regional open biomass burning also lead to higher OC and EC concentrations during the dry season at the industrially influenced site (iI-AF) and one of the regional background sites (RR-SK). From the seasonal concentration patterns, it seemed as if household combustion for space heating also contributed at these two sites during the cold months, but this could not be proven, even if only samples with limited influence of open biomass burning were considered. Such biomass burning influences were semi-quantified by considering MODIS fire pixels occurring within the air mass fetch region for each sample. For the remaining regional background site (RR-LT) the results suggesed that only regional open biomass burning contributed to elevated levels of OC and EC in the dry season and that household combustion for space heating did not contribute significantly.

Organic farming positively affects honeybee colonies in a flower‐poor period in agricultural landscapes

Abstract Conventional farming has been implicated in global biodiversity and pollinator declines and organic farming is often regarded as a more ecological alternative. However, the effects of organic farming on honeybees remain elusive, despite honeybees’ importance as pollinators of crops and wild plants. Using 6 years of data from a large‐scale study with fortnightly measurements of honeybee colony performance traits (10 apiaries per year distributed across a 435 km2‐large research site in France), we related worker brood area, number of adult bees and honey reserves to the proportions of organic farmland in the surroundings of the hives at two spatial scales (300 m and 1,500 m). We found evidence that, at the local scale, organic farming increased both worker brood production and number of adult bees in the period of flower scarcity between the blooms of oilseed rape and sunflower (hereafter ‘dearth period’). At the landscape scale, organic farming increased honey reserves during the dearth period and at the beginning of the sunflower bloom. The results suggest that worker brood development benefitted from organic farming mostly through a more diverse diet due to an increase in the availability of diverse pollen sources in close proximity of their hives. Reduced pesticide drift may have additionally improved bee survival. Honey reserves were possibly mostly affected by increased availability of melliferous flowers in foraging distance. Synthesis and applications. Organic farming increases honeybee colony performance in a period of resource scarcity, likely through a continuous supply of floral resources including weeds, cover crops and semi‐natural elements. We demonstrate how worker brood area increases in the critical dearth period (between the blooms of oilseed rape and sunflower). This has previously been linked to winter colony survival, suggesting that organic farmland may mitigate repercussions of intensive farming on colony vitality. We conclude that organic farming benefits a crucial crop pollinator with potential positive implications for agriculture in the wider landscape.

Groundwater fluoride in Sri Lanka: opportunities to mitigate the risk at maximum contaminant level

High groundwater fluoride (F) is one of the major environmental hazards in the dry zone of Sri Lanka. The prolonged exposure to F at maximum contaminant levels can give rise to lifelong debility and disability among its inhabitants. This study investigated the F contamination in groundwater resources in Sri Lanka above recommended Maximum Contaminant Levels (MCL) and possibilities to mitigate the health risk. Groundwater samples (6107) were randomly collected from different geographic areas of the country, and categorised as hazardous, if it exceeded the maximum contaminant level of 4 mg/L (the level at which bone health is compromised). The minimum distances from a hazardous to a relatively safe F groundwater source (below 1.0 mg/L and 1.5 mg/L) were determined using geospatial analysis. Results: Only 2.3% (142) of the total sample was found to be hazardous to skeletal health. Optimal F sources were identified in close proximity to highly contaminated sources (>4.0 mg/L), some even within a walking distance of 500 metres. The identification and elimination of maximally contaminated sources, possibly by dilution with widely available low F sources in close proximity, would be a more feasible and cost effective approach to ensure long term public health benefits.

Sedimentary profiles of pollution marker chemicals along a large tributary of Chesapeake Bay (mid-Atlantic USA)

Molecular markers in environmental geochemistry include natural product or pollutant chemicals in sediments that are indicative of discharge sources or emission pathways. Four classes of molecular marker compounds, including fatty acids, sterols, PCBs, and PAHs, in surficial sediments (top 2 cm) collected along a downstream transect of the Potomac River within the US mid-Atlantic region were analyzed and correlated with potential pollution discharge sources in close proximity to the sampling sites. Thirty-five surficial sediment samples were collected using a petite Ponar grab sampler along a 320-km longitudinal transect of the Potomac River (mid-Atlantic USA), a major tributary of Chesapeake Bay, ranging from the upland fluvial river to its confluence with the Bay. The sediments were collected along the transect at approximately equidistant points. The marker chemicals were extracted from sediments using microwave-assisted extraction and quantified on a dry weight basis by gas chromatography or gas chromatography-mass spectrometry. Sediment moisture, texture, and organic carbon and nitrogen content were also determined. Fatty acids and sterols were well correlated with ecological factors in the Potomac River, while the sterol ratio epi+brassicasterol/stigmasterol showed moderate spatial correlation with nearby waste treatment plants (WTPs) and city locations, especially in the upland and tidal freshwater river. The fecal sterol coprostanol also showed moderate spatial correlation with some WTPs in both the upland and tidal river. PCB and PAH concentrations were primarily correlated with urban and large military installations. PCBs in sediments appeared to be predominantly derived from Aroclors while PAHs showed a strong pyrogenic origin. Retene and perylene were unique markers for PAHs in sediment and were indicative of aged organic matter in sediments. The marker chemicals had utility in identifying pollution emission sources and pathways in the Potomac River. For PCB pollutants, sediment profiles reflected localized source emissions from industrial sites. PAHs showed a downstream plume effect derived from urban Washington, DC. Fatty acids and sterols were most useful for identifying ecological shifts (i.e., terrestrial versus aquatic origin), but showed spatial correlations with wastewater treatment plants and cities.

New system for detecting, mapping, monitoring, quantifying and reporting fugitive gas emissions

Coal seam gas (CSG) is an abundant energy source that’s been portrayed as having a lower Greenhouse Gas footprint than coal, but there have been concerns that fugitive emissions may be larger than estimated. Fugitive emissions associated with CSG development are engineered release points (valves and vents etc.) and unintentional equipment leaks. Various gas detection technologies are utilised across the industry that are effective at detecting large emissions sources in close proximity, but they are difficult to scale up to the large size needed for the CSG industry. We’ll present a summary of a trial utilising a new mobile methane detection and emission quantification system: the Picarro EQ (Emissions Quantification). After driving this instrument around CSG infrastructure, Picarro’s cloud-based analytics generate a map of methane measurements and emissions with wind indicators pointing to likely sources. Since all measurements are on a secure cloud-based service, any authorised operator can log into it to run reports and analytics. This system has been used to make measurements in the Barnett Shale, United States. We present results and demonstrate its usage within an operational CSG area to quantify and identify emissions from CSG infrastructure.

Elevated Arsenic and Uranium Concentrations in Unregulated Water Sources on the Navajo Nation, USA

Regional water pollution and use of unregulated water sources can be an important mixed metals exposure pathway for rural populations located in areas with limited water infrastructure and an extensive mining history. Using censored data analysis and mapping techniques we analyzed the joint geospatial distribution of arsenic and uranium in unregulated water sources throughout the Navajo Nation, where over 500 abandoned uranium mine sites are located in the rural southwestern United States. Results indicated that arsenic and uranium concentrations exceeded national drinking water standards in 15.1 % (arsenic) and 12.8 % (uranium) of tested water sources. Unregulated sources in close proximity (i.e., within 6 km) to abandoned uranium mines yielded significantly higher concentrations of arsenic or uranium than more distant sources. The demonstrated regional trends for potential co-exposure to these chemicals have implications for public policy and future research. Specifically, to generate solutions that reduce human exposure to water pollution from unregulated sources in rural areas, the potential for co-exposure to arsenic and uranium requires expanded documentation and examination. Recommendations for prioritizing policy and research decisions related to the documentation of existing health exposures and risk reduction strategies are also provided.