Principles and application of an in vivo swine assay for the determination of arsenic bioavailability in contaminated matrices

The assessment of arsenic (As) bioavailability from contaminated matrices is a crucial parameter for reducing the uncertainty when estimating exposure for human health risk assessment. In vivo assessment of As utilising swine is considered an appropriate model for human health risk assessment applications as swine are remarkably similar to humans in terms of physiology and As metabolism. While limited in vivo As bioavailability data is available in the literature, few details have been provided regarding technical considerations for performing in vivo assays. This paper describes, with examples, surgical, experimental design and analytical issues associated with performing chronic and acute in vivo swine assays to determine As bioavailability in contaminated soil and food.     

Distinguishing stressors acting on land bird communities in an urbanizing environment

Urbanization has profound influences on ecological communities, but our understanding of causal mechanisms is limited by a lack of attention to its component stressors. Published research suggests that at landscape scales, habitat loss and fragmentation are the major drivers of community change, whereas at local scales, human activity and vegetation management are the primary stressors. Little research has focused on whether urbanization stressors may supplant natural factors as dominant forces structuring communities. We used model selection to determine the relative importance of urban development, human activity, local and landscape vegetation, topography, and geographical location in explaining land bird species richness, abundance, and dominance. We analyzed the entire community and groups of species based on ecological characteristics, using data collected in remnant forests along a gradient of urban development in the Lake Tahoe basin, California and Nevada, USA. Urbanization stressors were consistently among the principal forces structuring the land bird community. Strikingly, disturbance from human activity was the most important factor for richness in many cases, surpassing even habitat loss from development. Landscape-scale factors were consistently more important than local-scale factors for abundance. In demonstrating considerable changes in land bird community structure, our results suggest that ecosystem function in urban areas may be severely compromised. Such changes compel local- and landscape-scale management, focused research, and long-term monitoring to retain biodiversity in urban areas to the extent possible.     

Vole response to unintentional changes in the chemistry of GM poplars

Summary.  There is an increased interest for the use of GM trees in forestry and several commercially promising lines are now available. However, the ecological implications of the use of GM trees, e.g. effects on non-target natural enemies, have rarely been explored. The aim of this study was to determine if modification of non-defensive traits in GM poplars unintentionally can influence plant chemistry in a way that has consequences for palatability to voles. In a greenhouse experiment, we used two lines, SPS33A and SPS26, of GM hybrid poplars (Populus tremula x tremuloides) with 1.5 and 4 times, respectively, over-expression sucrose-phosphate synthase (SPS). This enzyme plays a central role in sucrose synthesis, affecting cold acclimation, mesophyll sucrose content and biomass production. As a control we used the isogenic unmodified wild type. Stems of these poplars were presented to bank voles and field voles in cafeteria experiments. The concentration of condensed tannins was higher in leaves of lines SPS33A and SPS26 than in the isogenic wild-type and the concentration of nitrogen was higher in line SPS33A than in both the wild-type and line SPS26. Although the bank voles consumed slightly less bark from SPS33A, there were no significant differences in the preference of bank vole or field vole for the different poplar lines. This indicates that the changes in plant chemistry were insufficient to produce any strong herbivore response or that alteration in tannins and nitrogen counteracted each other. Still, changes in the interactions between mammalian herbivores and GM trees are important to consider in future cost-benefits analyses of GM trees.     

Non-native vascular flora of the Arctic: Taxonomic richness,distribution and pathways

We present a comprehensive list of non-native vascular plants known from the Arctic, explore their geographic distribution, analyze the extent of naturalization and invasion among 23 subregions of the Arctic, and examine pathways of introductions. The presence of 341 non-native taxa in the Arctic was confirmed, of which 188 are naturalized in at least one of the 23 regions. A small number of taxa (11) are considered invasive; these plants are known from just three regions. In several Arctic regions there are no naturalized non-native taxa recorded and the majority of Arctic regions have a low number of naturalized taxa. Analyses of the non-native vascular plant flora identified two main biogeographic clusters within the Arctic: American and Asiatic. Among all pathways, seed contamination and transport by vehicles have contributed the most to non-native plant introduction in the Arctic.     

Nuclear magnetic resonance logging: Example applications of an emerging tool for environmental investigations

Nuclear magnetic resonance (NMR) geophysical tools have been widely used in the petroleum exploration industry since the 1960s and have improved significantly in the last two decades. These tools can provide estimates of bulk porosity and fluid content, quantification of bound versus mobile fluids, and estimates of hydraulic conductivity (K). Although the size and cost of oil‐field tools historically limited their use for near‐surface applications, smaller and more economical downhole NMR logging tools are now available for detecting and characterizing the formation water content and K to support environmental and groundwater resource investigations. These tools can be deployed using direct‐push drilling techniques or they can be lowered into existing open borings or wells with nonconductive polyvinyl chloride casings and screens. In many cases, using the tool in existing wells offers a safer and more cost‐effective alternative compared to drilling new boreholes. For environmental investigations, NMR can provide useful high‐resolution quantitative hydrostratigraphic information that can provide additional valuable data to further inform and refine the conceptual site model. This paper highlights several NMR field investigations that demonstrate the viability of this technology as a site characterization tool for near‐surface investigations. NMR measurements were compared to data from lithologic logs, cone penetrometer testing data, and prior field hydraulic tests. Use of NMR to detect vadose zone water, including previously unidentified perched groundwater zones, provided hydrostratigraphic details that could not be gleaned from historical well drilling logs and were used to evaluate drainable pore water versus pore water bound in small pores by capillary forces or electrochemically clay‐bond water. NMR also produced K estimates similar to those from conventional hydraulic tests, but the improved vertical resolution from NMR provided additional information regarding the vertical heterogeneity of the formation along the entire length of the well or borehole. Additionally, bench‐scale tests are presented that confirm the capability for NMR to reliably detect and quantify light nonaqueous phase liquid saturation (specifically diesel fuel and weathered gasoline) in situ. The field tests combined with bench‐scale testing results affirm the applicability and potential for NMR as a practical characterization tool that should increasingly be utilized in environmental investigations.     

Food crop accumulation and bioavailability assessment for antimony (Sb) compared with arsenic (As) in contaminated soils

Field samples and a 9-week glasshouse growth trial were used to investigate the accumulation of mining derived arsenic (As) and antimony (Sb) in vegetable crops growing on the Macleay River Floodplain in Northern New South Wales, Australia. The soils were also extracted using EDTA to assess the potential for this extractant to be used as a predictor of As and Sb uptake in vegetables, and a simplified bioaccessibility extraction test (SBET) to understand potential for uptake in the human gut with soil ingestion. Metalloids were not detected in any field vegetables sampled. Antimony was not detected in the growth trial vegetable crops over the 9-week greenhouse trial. Arsenic accumulation in edible vegetable parts was <10 % total soil-borne As with concentrations less than the current Australian maximum residue concentration for cereals. The results indicate that risk of exposure through short-term vegetable crops is low. The data also demonstrate that uptake pathways for Sb and As in the vegetables were different with uptake strongly impacted by soil properties. A fraction of soil-borne metalloid was soluble in the different soils resulting in Sb soil solution concentration (10.75?±?0.52 μg L^–1) that could present concern for contamination of water resources. EDTA proved a poor predictor of As and Sb phytoavailability. Oral bioaccessibility, as measured by SBET, was <7 % for total As and <3 % total Sb which is important to consider when estimating the real risk from soil borne As and Sb in the floodplain environment.     

Resource allocation for mitigating regional air pollution–related mortality: A summertime case study for five cities in the United States

An important issue of regional air quality management is to allocate air quality management funds to maximize environmental and human health benefits. In this study, we use an innovative approach to tackle this air quality management issue. We develop an innovative resource allocation model that allows identification of air pollutant emission control strategies that maximize mortality avoidances subject to a resource constraint. We first present the development of the resource allocation model and then a case study to show how the model can be used to identify resource allocation strategies that maximize mortality avoidances for top five Metropolitan Statistical Areas (MSAs) (i.e., New York, Los Angeles, Chicago, Dallas-Fort Worth, and Philadelphia) in the continental United States collectively. Given budget constraints in the U.S. Environmental Protection Agency’s (EPA) Clean Air Act assessment, the results of the case study suggest that controls of sulfur dioxide (SO₂) and primary carbon (PC) emissions from EPA Regions 2, 3, 5, 6, and 9 would have significant health benefits for the five selected cities collectively. Around 30,800 air pollution–related mortalities could be avoided during the selected 2-week summertime episode for the five cities collectively if the budget could be allocated based on the results of the resource allocation model. Although only five U.S. cities during a 2-week episode are considered in the case study, the resource allocation model can be used by decision-makers to plan air pollution mitigation strategies to achieve the most significant health benefits for other seasons and more cities over a region or the continental U.S.Implications: Effective allocations of air quality management resources are challenging and complicated, and it is desired to have a tool that can help decision-makers better allocate the funds to maximize health benefits of air pollution mitigation. An innovative resource allocation model developed in this study can help decision-makers identify the best resource allocation strategies for multiple cities collectively. The results of a case study suggest that controls of primary carbon and sulfur dioxides emissions would achieve the most significant health benefits for five selected cities collectively.     

Small farm ponds: overlooked features with important impacts on watershed sediment transport

Despite their size, small farm ponds are important features in many landscapes. Yet hydrographical databases often fail to capture these ponds, and their impacts on watershed processes remain unclear. For a 230‐km² portion of central Texas, United States (U.S.), we created a historical inventory of ponds and quantified the accuracy of automated detection methods under varying drought conditions. In addition, we documented pond dredging/enlargement events and identified sites that had been abandoned. We also analyzed sediment cores from downstream reservoirs to track changes in watershed sediment transport. Over 75 years, pond densities increased more than 350% — to among the highest documented in the U.S. — and the ability of automated methods to detect these ponds was highly dependent on drought severity (R² = 0.96). Approximately 5% of ponds present in the 1950s were no longer present in 2012, while 33% were dredged between 1937 and 2012. Downstream reservoir sedimentation has decreased by an average of 55% as ponds have increased in number. These findings suggest that small ponds and the maintenance of trapping efficiency have large‐scale impacts on sediment dynamics. Accurately accounting for these storage effects is vital to water resource planning efforts.     

The EU effect: does trade with the EU reduce CO2 emissions in the developing world?

The European Union (EU) is an important destination for developing country exports. Has the EU’s commitment to the Kyoto Protocol induced developing countries to reduce their carbon dioxide (CO₂) emissions? Our analyses of 136 developing countries from 1981 through 2007 suggests that: developing countries’ export dependence on the EU is associated with CO₂ emission reductions post-Kyoto in relation to the pre-Kyoto time period; this also holds for SO_2, which, while not covered under Kyoto, is linked with CO₂ emission levels; this does not hold for PM₁₀, a pollutant which is not covered under Kyoto and is not directly associated with CO₂ emissions related to industrial activities; developing countries’ export dependence on non-EU developed countries and on the rest of the world is not associated with significant reductions in emissions between pre- and post-Kyoto for these pollutants . In sum, even in the absence of binding regulatory mandates, the EU appears to exert market leverage to project its regulatory preferences abroad.