Intermittent agitation of liquid manure: effects on methane,microbial activity,and temperature in a farm-scale study

Liquid manure storages are a significant source of methane (CH₄) emissions. Farmers commonly agitate (stir) liquid manure prior to field application to homogenize nutrients and solids. During agitation, manure undergoes mechanical stress and is exposed to the air, disrupting anaerobic conditions. This on-farm study aimed to better understand the effects of agitation on CH₄ emissions, and explore the potential for intentional agitation (three times) to disrupt the exponential increase of CH₄ emissions in spring and summer. Results showed that agitation substantially increased manure temperature in the study year compared to the previous year, particularly at upper- and mid-depths of the stored manure. The temporal pattern of CH₄ emissions was altered by reduced emissions over the subsequent week, followed by an increase during the second week. Microbial analysis indicated that the activity of archaea and methanogens increased after each agitation event, but there was little change in the populations of methanogens, archaea, and bacteria. Overall, CH₄ emissions were higher than any of the previous three years, likely due to warmer manure temperatures that were higher than the previous years (despite similar air temperatures). Therefore, intermittent manure agitation with the frequency, duration, and intensity used in this study is not recommended as a CH₄ emission mitigation practice.

Implications: The potential to mitigate methane emissions from liquid manure storages by strategically timed agitation was evaluated in a detailed farm-scale study. Agitation was conducted with readily-available farm equipment, and targeted at the early summer to disrupt methanogenic communities when CH₄ emissions increase exponentially. Methane emissions were reduced for about one week after agitation. However, agitation led to increased manure temperature, and was associated with increased activity of methanogens. Overall, agitation was associated with similar or higher methane emissions. Therefore, agitation is not recommended as a mitigation strategy.     

Contaminant mass flux and forensic assessment of polycyclic aromatic hydrocarbons: Tools to inform remediation decision making at a contaminated site in Canada

Polycyclic aromatic hydrocarbons (PAHs) and metal(loid) mass flux estimates and forensic assessment using PAH diagnostic ratios were used to inform remediation decision making at the Sydney Tar Ponds (STPs) and Coke Ovens cleanup project in eastern Canada. Environmental effects monitoring of surface marine sediments in Sydney Harbor indicated significantly higher PAH concentrations during the first year of remediation monitoring compared to baseline. This was equivalent to PAH loadings of ～2,000 kg over a 15‐month period. Increases in sediment PAH concentrations raised serious concerns for regulators, who requested cessation of remediation activities early in the $400 M (CAD) project. Historically, the STPs were reported as the primary source of PAH contamination in Sydney Harbor with estimated discharges of 300 to 800 kg/year between 1989 and 2001. Mass flux estimates of PAHs and metal(loid)s and PAH diagnostic ratios were used to evaluate if increases in PAH concentrations in marine sediments were the result of the STPs remediation activities. PAH mass flux estimates approximated that 17 to 97 kg/year were discharged from the STPs during three years of remediation and were corroborated by an independent PAH flux estimate of 119 kg in year 1. PAH fluxes to the Sydney Harbor were mostly surface water derived, with groundwater contributing negligible quantities (0.002–0.005 kg/year). Fluxes of metal(loid)s to harbor sediments were stable or declining across all years and were mirrored in sediment metal(loid) concentrations, which lacked temporal variation, unlike total PAH concentrations. Flux results were also corroborated using PAH diagnostic ratios, which found a common source of PAHs. Coal combustion was likely the principal source of PAHs and not migration from the STPs during remediation. Although short‐term residual sediment PAH increases during onset of remediation raised concerns for regulators, calls for premature cessation of remediation early in the project were unwarranted based on only one year of monitoring data. Mass flux estimates and forensic assessments using PAH diagnostic ratios proved useful tools to inform remediation decision making that helped environmental protection and reduced costs associated with lost cleanup time.     

A ten channel fibre-optic device for distributed sensing of underground hydrocarbon leakage

With millions of fuel storage tanks and oil pipelines installed around the world, there is inevitably frequent leakage of potentially hazardous hydrocarbons. As many of these installations are below ground, it can often be many years before the extent of the leak is discovered. We have previously reported the development of a sensor for the detection of such subterranean leaks, using infrared reflectometry to interrogate a hydrocarbon sensitive membrane. However, a single sensor cannot provide any information about the flow rate or direction of the leak. This paper describes the extension of the technology to a multi-channel distributed sensing system, using optical fibres capable of distributing the sensors over large subterranean areas. Results are reported from the evaluation of the device, which consisted of monitoring the movement of different hydrocarbons (gasoline, diesel and insulating oil) through a vertical sand-filled vessel.     

A novel sensor for monitoring leakage of petroleum and other liquid hydrocarbons into soil environments

This paper describes the use of a potentially implantable infrared reflectometer for the qualitative detection of petroleum and a number of other hydrocarbon solvents. A rugged, low-power, re-useable sensor was evaluated in the laboratory for its ability to detect petrol in soil. A hydrophobic fluoropolymer was used as the sensing surface due to its high selectivity for petroleum hydrocarbons. The photocurrent reflected by this surface from a near IR source was measured to test for petroleum saturation within the membrane, which in turn was an indicator of petroleum in the surrounding soil. The simplicity in the sensor design enabled a stable, low cost detection method for petroleum and other hydrocarbons, ideal for use in sub-surface applications.     

Re-use of remediated soils for the bioremediation of waste oil sludge

We investigated the possibility of re-using remediated soils for new bioremediation projects by spiking these soils with waste oil sludge in laboratory based microcosms. The level of Total Petroleum Hydrocarbon (TPH) reduction was high (>80%) in naturally attenuated microcosms and was not significantly improved by biostimulation, bioaugmentation and the combined treatment of bioaugmentation and biostimulation by week 12. This indicated that the observed TPH reduction might have been related to the soil's inherent hydrocarbon-degrading potential. Microbial community analysis (16S rDNA and ITS-based Denaturing Gradient Gel Electrophoresis fingerprints) confirmed the dominance of hydrocarbon degrading genera such as Alcanivorax and Scedosporium. Cluster and Shannon diversity analysis revealed similar but stable bacterial and fungal communities in naturally attenuated and amended microcosms indicating that rapid reduction in TPH may not always be accompanied by changes in soil microbial communities. This study has therefore shown that soils previously used for bioremediation can have an improved hydrocarbon degrading potential which was successfully re-harnessed for new projects. This ability to re-harness this potential is attractive because it substantially reduces operational costs as no additional bioremediation treatments are needed. It can also extend a landfill's lifespan as soils can be re-used again before landfill disposal.     

Confronting socially generated uncertainty in adaptive management

As more and more organizations with responsibility for natural resource management adopt adaptive management as the rubric in which they wish to operate, it becomes increasingly important to consider the sources of uncertainty inherent in their endeavors. Without recognizing that uncertainty originates both in the natural world and in human undertakings, efforts to manage adaptively at the least will prove frustrating and at the worst will prove damaging to the very natural resources that are the management targets. There will be more surprises and those surprises potentially may prove at the very least unwanted and at the worst devastating. We illustrate how acknowledging uncertainty associated with the natural world is necessary but not sufficient to avoid surprise using case studies of efforts to manage three wildlife species; Hector's Dolphins, American Alligators and Pallid Sturgeon. Three characteristics of indeterminism are salient to all of them; non-stationarity, irreducibility and an inability to define objective probabilities. As an antidote, we recommend employing a holistic treatment of indeterminism, that includes recognizing that uncertainty originates in ecological systems and in how people perceive, interact and decide about the natural world of which they are integral players.     

Modeling sediment and nitrogen export from a rural watershed in eastern Canada using the soil and water assessment tool

Watershed simulation models can be used to assess agricultural nonpoint-source pollution and for environmental planning and improvement projects. However, before application of any process-based watershed model, the model performance and reliability must be tested with measured data. The Soil and Water Assessment Tool version 2005 (SWAT2005) was used to model sediment and nitrogen loads from the Thomas Brook Watershed, which drains a 7.84 km rural landscape in the Annapolis Valley of Nova Scotia, Canada. The Thomas Brook SWAT model was comprised of 28 subbasins and 265 hydrologic response units, most of them containing agricultural land use, which is the main nonpoint nitrogen source in the watershed. Crop rotation schedules were incorporated into the model using field data collected within Agriculture and Agri-Food Canada's Watershed Evaluation of Beneficial Management Practices program. Model calibration (2004-2006) and validation (2007-2008) were performed on a monthly basis using continuous stream flow, sediment, and nitrogen export measurements. Model performance was evaluated using the coefficient of determination, Nash-Sutcliff efficiency (NSE), and percent bias (PBIAS) statistics. Study results show that the model performance was satisfactory (NSE > 0.4; > 0.5) for stream flow, sediment, nitrate-nitrogen, and total nitrogen simulations. Annual corn, barley, and wheat yields were also simulated well, with PBIAS values ranging from 0.3 to 7.2%. This evaluation of SWAT demonstrated that the model has the potential to be used as a decision support tool for agricultural watershed management in Nova Scotia.     

Hydrologic and Phosphorus Export Behavior of Small Streams in Commercial Poultry‐Pasture Watersheds1

Romeis, J. Joshua, C. Rhett Jackson, L. Mark Risse, Andrew N. Sharpley, and David E. Radcliffe, 2011. Hydrologic and Phosphorus Export Behavior of Small Streams in Commercial Poultry‐Pasture Watersheds. Journal of the American Water Resources Association (JAWRA) 1‐19. DOI: 10.1111/j.1752‐1688.2011.00521.x Abstract: Few watershed‐scale studies have evaluated phosphorus export in streamflow from commercial poultry‐pasture operations. Continuous streamflow and mixed‐frequency water quality datasets were collected from nine commercial poultry‐pasture (AG) and three forested (FORS) headwater streams (2.4‐44 ha) in the upper Etowah River basin of Georgia to estimate total P (TP) loads and examine variability of hydrologic response and water quality of storm and nonstorm‐flow regimes. Data collection duration ranged from 18 to 22 months, and approximately 1,600 water quality samples were collected. Significant (p < 0.1) inverse relationships were detected between peak flow response variables and both drainage area and fraction of forest cover. Order‐of‐magnitude differences in TP and dissolved reactive P (DRP) concentration were observed between AG and FORS sites and among AG sites. TP yields of FORS sites ranged from 0.01 to 0.1 kg P/ha. Yields of AG sites ranged from 0.031 to 3.17 kg P/ha (median = 0.354 kg P/ha). With 95% confidence intervals, AG yields ranged from 0.025 to 13.1 kg P/ha. These small‐watershed‐scale yields were similar to field‐scale yields measured in other studies in other regions. TP yields were significantly related to area‐weighted Mehlich‐1 soil test P concentrations (p = 0.0073) and base‐flow water sample P concentrations (p ≤ 0.0005). Water quality sampling during base‐flow conditions may be a useful screening tool for P risk‐based management programs.