Poultry litter application to loblolly pine forests: growth and nutrient containment

Forestland application of poultry manure offers an alternative to the conventional practice of pastureland application. Before such a practice is considered viable, however, it must be demonstrated that the forest ecosystem is capable of absorbing the nutrients contained in poultry manure, especially nitrogen (N) and phosphorus (P). From the forestry perspective, it must also be demonstrated that tree growth is not diminished. We investigated these questions using loblolly pine (Pinus taeda L.) stands growing in central Mississippi in an area of high poultry production. Stockpiled broiler litter was applied to newly thinned, 8-yr-old stands at 0, 4.6, and 18.6 dry Mg ha-1, supplying 0, 200, and 800 kg N ha-1 and 0, 92, and 370 kg P ha-1, respectively. Levels of nitrate in soil water, monitored at a 50-cm depth with porous cup tension lysimeters, exceeded 10 mg N L-1 during the first two years after application in the 18.6 Mg ha-1 rate but only on two occasions in the first year for the lower rate of application. Phosphate was largely absent from lysimeter water in all treatments. Other macronutrients (K, Ca, Mg, S) were elevated in lysimeter water in proportion to litter application rates. Soil extractable nitrate showed similar trends to lysimeter water, with substantial elevation during the first year following application for the 18.6 Mg ha-1 rate. Mehlich III-extractable phosphate peaked in excess of 100 microg P g-1 soil during the third year of the study for the 18.6 Mg ha-1 rate. The 4.6 Mg ha-1 rate did not affect extractable soil P. Tree growth was increased by the poultry litter. Total stem cross-sectional area, or basal area, was approximately 20% greater after 2 yr for both rates of litter application. Overall, the nutrients supplied by the 4.6 Mg ha-1 rate were contained by the pine forest and resulted in favorable increases in tree growth. The higher rate, by contrast, did pose some risk to water quality through the mobilization of nitrate. These results show that, under the conditions of this study, application of poultry litter at moderate rates of approximately 5 Mg ha-1 to young stands of loblolly pine offers an alternative disposal option with minimal impacts to water quality and potential increases in tree growth.     

Patterns of Spatial Autocorrelation in Stream Water Chemistry

Geostatistical models are typically based on symmetric straight-line distance, which fails to represent the spatial configuration, connectivity, directionality, and relative position of sites in a stream network. Freshwater ecologists have explored spatial patterns in stream networks using hydrologic distance measures and new geostatistical methodologies have recently been developed that enable directional hydrologic distance measures to be considered. The purpose of this study was to quantify patterns of spatial correlation in stream water chemistry using three distance measures: straight-line distance, symmetric hydrologic distance, and weighted asymmetric hydrologic distance. We used a dataset collected in Maryland, USA to develop both general linear models and geostatistical models (based on the three distance measures) for acid neutralizing capacity, conductivity, pH, nitrate, sulfate, temperature, dissolved oxygen, and dissolved organic carbon. The spatial AICC methodology allowed us to fit the autocorrelation and covariate parameters simultaneously and to select the model with the most support in the data. We used the universal kriging algorithm to generate geostatistical model predictions. We found that spatial correlation exists in stream chemistry data at a relatively coarse scale and that geostatistical models consistently improved the accuracy of model predictions. More than one distance measure performed well for most chemical response variables, but straight-line distance appears to be the most suitable distance measure for regional geostatistical modeling. It may be necessary to develop new survey designs that more fully capture spatial correlation at a variety of scales to improve the use of weighted asymmetric hydrologic distance measures in regional geostatistical models.     

Characterization of methane emissions from five cold heavy oil production with sands (CHOPS) facilities

Cold heavy oil production with sands (CHOPS) is a common oil extraction method in the Canadian provinces of Alberta and Saskatchewan that can result in significant methane emissions due to annular venting. Little is known about the magnitude of these emissions, nor their contributions to the regional methane budget. Here the authors present the results of field measurements of methane emissions from CHOPS wells and compare them with self-reported venting rates. The tracer ratio method was used not only to analyze total site emissions but at one site it was also used to locate primary emission sources and quantify their contributions to the facility-wide emission rate, revealing the annular vent to be a dominant source. Emissions measured from five different CHOPS sites in Alberta showed large discrepancies between the measured and reported rates, with emissions being mainly underreported. These methane emission rates are placed in the context of current reporting procedures and the role that gas-oil ratio (GOR) measurements play in vented volume estimates. In addition to methane, emissions of higher hydrocarbons were also measured; a chemical “fingerprint” associated with CHOPS wells in this region reveals very low emission ratios of ethane, propane, and aromatics versus methane. The results of this study may inform future studies of CHOPS sites and aid in developing policy to mitigate regional methane emissions.

Implications: Methane measurements from cold heavy oil production with sand (CHOPS) sites identify annular venting to be a potentially major source of emissions at these facilities. The measured emission rates are generally larger than reported by operators, with uncertainty in the gas-oil ratio (GOR) possibly playing a large role in this discrepancy. These results have potential policy implications for reducing methane emissions in Alberta in order to achieve the Canadian government’s goal of reducing methane emissions by 40–45% below 2012 levels within 8 yr.     

Evaluation of the Design Features of Interactive Sea-Level Rise Viewers for Risk Communication

Interactive sea-level rise viewers (ISLRVs) are digital tools used to communicate about impacts of sea-level rise (SLR) and support decision-making. This study characterizes how ISLRVs communicate about SLR-related risks and provide decision-making support. It identifies key themes about fostering accurate mental models of SLR processes, informing about inundation likelihood, communicating about related social and ecological risks, and providing features users can apply to specific tasks. We present a framework for understanding this type of communication tool that designers can use to develop robust ISLRVs that can support audiences’ understanding and decision-making needs, and contribute to enhancement of coastal resiliency.     

Effect of Interfacial Modifiers on Mechanical and Physical Properties of the PHB Composite with High Wood Flour Content

To explore the commercial viability of Polyhydroxybutyrate (PHB)/wood flour (WF) composites, systems were produced at industry-standard levels of fiber loading. Further, four interfacial modifiers were selected to improve the mechanical properties of PHB/WF composites, including maleated PHB (PHB-g-MA), a low molecular weight epoxy, a low molecular weight polyester, and polymethylene-diphenyl-diisocyante (pMDI). Results showed that all modifiers resulted in improvements in tensile strength and modulus, however, pMDI showed the highest improvements. The pMDI modifier also improved water uptake of the composites. Study of the fracture surfaces showed signs of improved fiber bonding, as did morphological studies by dynamic mechanical analysis (DMA), and differential scanning calorimetry (DSC). Interpretation of the DSC and DMA results indicate possible reactions with lubricant, and interactions between PHB and wood fibers with the addition of pMDI.     

Exploring the origins of ‘social license to operate’ in the mining sector: Perspectives from governance and sustainability theories

In the mining sector, local communities have emerged as particularly important governance actors. Conventional approaches to mineral development no longer suffice for these communities, which have demanded a greater share of benefits and increased involvement in decision making. These trends have been spurred by the growth of the sustainable development paradigm and governance shifts that have increasingly transferred governing authority towards non-state actors. Accordingly, there is now widespread recognition that mineral developers need to gain a ‘social license to operate’ (SLO) from local communities in order to avoid potentially costly conflict and exposure to social risks. A social license can be considered to exist when a mining project is seen as having the ongoing approval and broad acceptance of society to conduct its activities. Due to the concept's relatively recent emergence, however, only a limited body of scholarship has developed around SLO. Drawing on examples from northern Canada, this paper uses governance and sustainability theories to conceptualize the origins of SLO in the mining sector and describe some of the associated implications. Further research is needed to determine governance arrangements which help facilitate establishment of SLO in different mineral development contexts.     

Implications of cation exchange on clay release and colloid-facilitated transport in porous media

Column experiments were conducted to study chemical factors that influence the release of clay (kaolinite and quartz minerals) from saturated Ottawa sand of different sizes (710,360, and 240 microm). A relatively minor enhancement of clay release occurred when the pH was increased (5.8 to 10) or the ionic strength (IS) was decreased to deionized (DI) water. In contrast, clay release was dramatically enhanced when monovalent Na+ was exchanged for multivalent cations (e.g., Ca2+ and Mg2+) on the clay and sand and then the solution IS was reduced to DI water. This solution chemistry sequence decreased the adhesive force acting on the clay as a result of an increase in the magnitude of the clay and sand zeta potential with cation exchange, and expansion of the double layer thickness with a decrease in IS to DI water. The amount of clay release was directly dependent on the Na+ concentration of the exchanging solution and on the initial clay content of the sand (0.026-0.054% of the total mass). These results clearly demonstrated the importance of the order and magnitude of the solution chemistry sequence on clay release. Column results and scanning electron microscope (SEM) images also indicated that the clay was reversibly retained on the sand, despite predictions of irreversible interaction in the primary minimum. One plausible explanation is that adsorbed cations increased the separation distance between the clay-solid interfaces as a result of repulsive hydration forces. A cleaning procedure was subsequently developed to remove clay via cation exchange and IS reduction; SEM images demonstrated the effectiveness of this approach. The transport of Cu2+ was then shown to be dramatically enhanced by an order of magnitude in peak concentration by adsorption on clays that were released following cation exchange and IS reduction.     

Understanding vulnerability in southern Africa: comparative findings using a multiple-stressor approach in South Africa and Malawi

Within southern Africa, many households are facing increasing pressures as they deal with multiple challenges such as low employment, high levels of disease, environmental resources under pressure and changing political landscapes. To respond to the needs of different individuals and households, it is important to define the nature of their vulnerability. An increasing amount of theoretical and empirical work on the concept of ‘vulnerability’ has led to a range of definitions, indicators and measurement tools, which have come to characterise this field of study. As a result, there is no one general consensus. This paper presents the results from the latest in a series of applied studies conducted since 2004 by a network of scientists working in southern Africa, aimed at refining the definition and application of the concept of vulnerability. The study employed a recently developed multiple-stressor model to guide the collection and analysis of data from three sites in South Africa and Malawi. In this paper, we identify and explore five key ‘symptoms’ of vulnerability emerging from our multi-country data and reflect on the usefulness of the model employed.     

Response of Nitrogen Loading to the Chesapeake Bay to Source Reduction and Land Use Change Scenarios: A SPARROW‐Informed Analysis

In response to concerns regarding the health of streams and receiving waters, the United States Environmental Protection Agency established a total maximum daily load for nitrogen in the Chesapeake Bay watershed for which practices must be in place by 2025 resulting in an expected 25% reduction in load from 2009 levels. The response of total nitrogen (TN) loads delivered to the Bay to nine source reduction and land use change scenarios was estimated using a Spatially Referenced Regression on Watershed Attributes model. The largest predicted reduction in TN load delivered to the Bay was associated with a scenario in which the mass of TN as fertilizer applied to agricultural lands was decreased. A 25% decrease in the mass of TN applied as fertilizer resulted in a predicted reduction in TN loading to the Bay of 11.3%, which was 2.5–5 times greater than the reductions predicted by other scenarios. Eliminating fertilizer application to all agricultural land in the watershed resulted in a predicted reduction in TN load to the Bay of 45%. It was estimated that an approximate 25% reduction in TN loading to the Bay could be achieved by eliminating fertilizer applied to the 7% of subwatersheds contributing the greatest fertilizer‐sourced TN loads to the Bay. These results indicate that management strategies aimed at decreasing loading from a small number of subwatersheds may be effective for reducing TN loads to the Bay, and similar analyses are possible in other watersheds.