A method for quantifying bias in modeled concentrations and source impacts for secondary particulate matter

A method for quantifying source impacts for secondary PM_2.5 species is derived. The method provides estimates of bias in modeled concentrations. Adjusted concentrations match corresponding observations at monitored locations. Sources impacts on secondary species are estimated over the US for 20 sources. Community Multi-Scale Air Quality (CMAQ) estimates of sulfates, nitrates, ammonium, and organic carbon are highly influenced by uncertainties in modeled secondary formation processes, such as chemical mechanisms, volatilization, and condensation rates. These compounds constitute the majority of PM_2.5 mass, and reducing bias in estimated concentrations has benefits for policy measures and epidemiological studies. In this work, a method for adjusting source impacts on secondary species is developed that provides estimates of source contributions and reduces bias in modeled concentrations compared to observations. The bias correction adjusts concentrations and source impacts based on the difference between modeled concentrations and observations while taking into account uncertainties at the location of interest; and it is applied both spatially and temporally. We apply the method over the US for 2006. The mean bias for initial CMAQ concentrations compared to observations is −0.28 (OC), 0.11 (NO₃), 0.05 (NH₄), and −0.08 (SO₄). The normalized mean bias in modeled concentrations compared to observations was effectively zero for OC, NO₃, NH₄, and SO₄ after applying the secondary bias correction. 10-fold cross-validation was conducted to determine the performance of the spatial application of the bias correction. Cross-validation performance was favorable; correlation coefficients were greater than 0.69 for all species when comparing observations and concentrations based on kriged correction factors. The methods presented here address model uncertainties by improving simulated concentrations and source impacts of secondary particulate matter through data assimilation. Secondary-adjusted concentrations and source impacts from 20 emissions sources are generated for 2006 over continental US.     

SNOTEL,the Soil Climate Analysis Network,and water supply forecasting at the Natural Resources Conservation Service: Past,present, and future

The Snow Survey and Water Supply Forecasting (SSWSF) Program and the Soil Climate Analysis Network (SCAN) of the United States Department of Agriculture's Natural Resources Conservation Service (NRCS) generate key observational and predictive information for water managers. Examples include mountain climate and snow monitoring through manual snow surveys and the SNOw TELemetry (SNOTEL) and SNOtel LITE networks, in situ soil moisture data acquisition through the SCAN and SNOTEL networks, and water supply forecasting using river runoff prediction models. The SSWSF Program has advanced continuously over the decades and is a major source of valuable water management information across the western United States, and the SCAN network supports agricultural and other water users nationwide. Product users and their management goals are diverse, and use-cases range from guiding crop selection to seasonal flood risk assessment, drought monitoring and prediction, avalanche and fire prediction, hydropower optimization, tracking climate variability and change, environmental management, satisfying international treaty and domestic legal requirements, and more. Priorities going forward are to continue innovating to enhance the accuracy and completeness of the observational and model-generated data products these programs deliver, including expanded synergies with the remote sensing community and uptake of artificial intelligence while maintaining long-term operational reliability and consistency at scale.     

Ambient levels of PFOS and PFOA in multiple environmental media

Making remediation and risk management decisions for widely‐distributed chemicals is a challenging aspect of contaminated site management. The objective of this study is to present an initial evaluation of the ubiquitous, ambient environmental distribution of poly‐ and perfluoroalkyl substances (PFAS) within the context of environmental decision‐making at contaminated sites. PFAS are anthropogenic contaminants of emerging concern with a wide variety of consumer and industrial sources and uses that result in multiple exposure routes for humans. The combination of widespread prevalence and low screening levels introduces considerable uncertainty and potential costs in the environmental management of PFAS. PFAS are not naturally‐occurring, but are frequently detected in environmental media independent of site‐specific (i.e., point source) contamination. Information was collected on background and ambient levels of two predominant PFAS, perfluorooctane sulfonate and perfluorooctanoate, in North America in both abiotic media (soil, sediment, surface water, and public drinking water supplies) and selected biotic media (human tissues, fish, and shellfish). The background or ambient information was compiled from multiple published sources, organized by medium and concentration ranges, and evaluated for geographical trends and, when available, also compared to health‐based screening levels. Data coverage and quality varied from wide‐ranging and well‐documented for soil, surface water, and serum data to more localized and less well‐documented for sediment and fish and shellfish tissues and some uncertainties in the data were noted. Widespread ambient soil and sediment concentrations were noted but were well below human health‐protective thresholds for direct contact exposures. Surface water, drinking water supply waters (representing a combination of groundwater and surface water), fish and shellfish tissue, and human serum levels ranged from less than to greater than available health‐based threshold values. This evaluation highlights the need for incorporating literature‐based or site‐specific background into PFAS site evaluation and decision‐making, so that source identification, risk management, and remediation goals are properly focused and to also inform general policy development for PFAS management.     

Paradigms,paradoxes and a propitious niche: conservation and Indigenous social justice policy in Australia

In Australia, redressing past injustices and recognising Indigenous peoples' spiritual and cultural connections to land have resulted in the return of significant amounts of land to Indigenous people. Parallel to this, in attempts to address declining biodiversity, innovative and neo-liberal approaches to conservation under a new paradigm have been promoted. The role and influence of the non-state sector are increasing, and Indigenous peoples’ involvement in conservation is also growing. This paper reviews the history of conservation and Indigenous social justice policy in Australia. It describes how the social justice agenda has been the primary motivator of returning land to Indigenous Australians, and historically has been the driver and catalyst for Indigenous peoples' involvement in conservation, whilst the conservation agenda has increased conservation on private lands and the role and influence of the non-state conservation sector. The paper reveals how the trajectories of conservation and Indigenous social justice have become intrinsically linked with the emergence of new paradigms, providing opportunities for a propitious niche. Yet it also shows how the two trajectories have manifested themselves with a paradox of disparity; achievements secured under an Indigenous social justice agenda are being enjoyed by conservation under the new paradigm, whilst Indigenous social justice is increasingly becoming dependent on a conservation agenda.     

Investigation of the time evolved spatial distribution of urban PM2.5 concentrations and aerosol composition during episodic high PM events in Yuma,AZ

An interdisciplinary field study designed to investigate the spatial and temporal variability of atmospheric aerosols during high particulate matter (PM) events along the US–Mexico border near Yuma, AZ was run during the week of March 18, 2007. The experiments were designed to quantify chemical composition and physical phenomena governing the transport of aerosols generated from episodic high PM events. The field study included two micrometeorological monitoring sites; one rural and one urban, equipped with sonic anemometers, continuous particulate concentration monitors and ambient aerosol collection equipment. In addition to the two main monitoring sites, five additional locations were equipped with optical particle counters to allow for the investigation of the spatial and temporal distribution of PM_2.5 in the urban environment. In this paper, the meteorological and turbulence parameters governing the distribution and concentration of PM_2.5 in the urban environment for two high-wind erosion events and one burning event are compared. The interaction between local atmospheric conditions and the particulate distribution is investigated. Results indicate that a single point measurement in the urban area of Yuma may not be sufficient for determining the ambient PM concentrations that the local population experiences; all three high PM events indicated PM_2.5 varied considerably with maximum urban concentrations 5–10 times greater than the measured minima. A comparison of inorganic and carbonaceous content of the aerosols for the three high PM events is presented. The comparison shows an increase in silicon during crustal dust events and an increase in elemental and organic carbon during the burn event. Additional surface chemistry analysis, using time-of-flight secondary ion mass spectrometry (ToF-SIMS), for aerosols collected at the urban and rural sites during the burn event are discussed. The surface chemistry analysis provides positive ion mass spectra of organic and inorganic species in the ambient aerosol, and can be used to determine the type of combustion process that contributed to an increase in PM concentration during the burn event.     

Recovery of sulfate saturated soils in the Plynlimon catchments, mid-Wales following reductions in atmospheric S inputs from the 1980s to 2011

Sulfate adsorption capacity of B-horizons of base-poor, predominantly stagnopodzol, soils from the Plynlimon catchments, mid-Wales was determined by combination of laboratory adsorption and desorption isotherms. Results show that sulfate adsorption capacity of a range of stagnopodzol (Histic-stagno-podzol (Leptic), WRB), brown podzolic soil (Histic-umbrisol (Leptic), WRB) and stagnohumic gley (Histic-stagno-gleysol, WRB) B-horizons was positively related to the amounts of extractable (pyrophosphate and oxalate) Fe + Al, with the stagnopodzol and brown podzolic soil Bs horizon having the largest adsorption capacity and stagnohumic gley Bg horizon the smallest adsorption capacity. Results show that dissolved organic carbon (DOC) has a negative but limited effect on sulfate adsorption in these soils. Results obtained from a set of historical soil samples revealed that the grassland brown podzolic soil Bs horizon and afforested stagnopodzol Bs horizon were highly saturated with sulfate in the 1980s, at 63% and 89% respectively, whereas data from some recently sampled soil from two sites revisited in 2010-11 indicates that percentage sulfate adsorption saturation has since fallen substantially, to 41% and 50% respectively. Between 1984 and 2009 the annual rainfall-weighted mean excess SO(4)-S concentration in bulk precipitation declined linearly from 0.37 mg S l(-1) to 0.17 mg S l(-1). Over the same period, flow weighted annual mean stream water SO(4)-S concentrations decreased approximately linearly from 1.47 mg S l(-1) to 0.97 mg S l(-1) in the plantation afforested Hafren catchment compared to a drop from 1.25 to 0.69 mg S l(-1) in the adjacent moorland catchment of the Afon Gwy. In flux terms, the mean decrease in annual stream water SO(4)-S flux has been approximately 0.4 kg S ha(-1) yr(-1), whilst the recovery in stream water quality in the Afon Cyff grassland catchment has been partly offset by loss of SO(4)-S by desorption from the soil sulfur pool of approximately 0.2 kg S ha(-1) yr(-1).     

Usefulness and uses of climate forecasts for agricultural extension in South Carolina,USA

Farmers and extensionists can use forecasts about agro-climatic conditions to reduce risks of agricultural production. Eighteen extension agents, researchers, consultants, and farmers provided feedback about decision support tools that utilize such forecasts during focus groups that were conducted in Florence, South Carolina on January 14, 2011. Climate Risk and County Yield Database were the tools most selected as potentially useful for agricultural extension in South Carolina. An irrigation scheduler was the most frequently mentioned tool to be developed. Also, a survey of Clemson University’s extension personnel was conducted in January and February 2011 to assess interest of South Carolina’s growers and producers in using climate forecasts, eleven potential uses of climate forecasts by extension’s clientele, and potential usefulness to extensionists of twelve specific forecasts. Clemson’s extensionists represent approximately 97 % of the state’s agricultural extensionists. They are more likely than not to agree that growers and producers are interested in using climate forecasts. Most of the state’s extension personnel also think that farmers could use a climate forecast to improve irrigation management and planting schedules. A majority of the state’s extensionists thinks that a freeze alert could be useful to them and the proportion that thinks the forecast could be useful exceeds the proportion that thinks any other forecast could be useful. Most extensionists also think that a forecast of plant moisture stress could be useful to help farmers schedule irrigation. The key survey results are remarkably similar to those from surveys of extension personnel at North Carolina State University in early 2009 and University of Florida in late 2004.     

Regeneration of spent TiO2 nanoparticles for Pb (II), Cu (II), and Zn (II) removal

Spent sorbents in water treatment processes have potential risks to the environment if released without proper treatment. The aim of this work was to investigate the potential regeneration of commercially prepared nano-TiO₂ (anatase) for the removal of Pb (II), Cu (II), and Zn (II) by pH 2 and ethylenediaminetetraacetic acid (EDTA) solutions. The percent of metal adsorption/desorption decreased with the increasing number of regeneration cycles, and the extent of decrease varied for each metal. Competitive effects were observed for the adsorption/desorption of different metals when the nano-TiO₂ was regenerated by EDTA solutions. Nano-TiO₂ was able to treat simulated metal polluted water with greater than 94 % adsorption and greater than 92 % desorption after four cycles of regeneration using pH 2 solution. These results demonstrated that nano-TiO₂ can be regenerated and reused using pH 2 solution compared to an EDTA solution for aquatic metal removal, which makes nanosorbents promising and economically and environmentally more attractive in the application of water purification.     

A sorption kinetics model for arsenic adsorption to magnetite nanoparticles

Introduction  

Arsenic is a well known water contaminant that causes toxicological and carcinogenic effects. In this work magnetite nanoparticles were examined as possible arsenic sorbents. The objective of this work was to develop a sorption kinetics model, which could be used to predict the amount of arsenic adsorbed by magnetite nanoparticles in the presence of naturally occurring species using a first-order rate equation, modified to include adsorption, described by a Langmuir isotherm.     

Adsorption of Pb,Cd, Cu,Zn, and Ni to titanium dioxide nanoparticles: effect of particle size,solid concentration,and exhaustion

Purpose  

Adsorption of metals (Pb, Cd, Cu, Ni, Zn) to TiO₂ nanoparticles and bulk particles was examined for use as a contaminant removal substrate as a function of particle size, sorbent concentration, and exhaustion.