Evaluation of a sustainable remediation option: Beneficial reuse of petroleum-contaminated sediment as an energy source

The characteristics of petroleum-contaminated sediment (PCS) have been evaluated to assess whether the practice of its beneficial reuse as a sole or supplemental energy source is sustainable relative to other sediment remediation options such as monitored natural recovery (MNR), capping, or off-site disposal. Some of these remediation options for PCS are energy-intensive and/or require land utilization. The energy and compositional analysis results indicate a low carbon content (15–17%(wt)) and corresponding low energy values of 5,200 kJ/kg (2,200 Btu/lb) to 5,600 kJ/kg (2,400 Btu/lb). However, given other decision-making criteria, the sediment may contain enough value to be added as a supplemental fuel given that it is normally considered a waste product and is readily available.

The thermogravimetric profiles obtained under both combustion and pyrolytic conditions showed that the sulfur contents were comparable to typical low sulfur bituminous or lignite coals found in the United States, and most of the volatiles could be vaporized below 750°C. The heavy metal concentrations determined before and after combustion of the PCS indicated that further engineering controls may be required for mercury, arsenic, and lead. Due to the potential for reduction of public health and environmental threats, potential economic savings, and conservation of natural resources (petroleum and land), removal of PCS by dredging and beneficial reuse as a supplemental fuel clearly has merit to be considered as a sustainable remediation option.

Implications: This study will provide a logical evaluation process to determine whether petroleum-contaminated sediment can be reused as an energy source. The energy and emissions values were determined and evaluated whether the sediment could be combusted for viable and sustainable use, considering several factors pertinent to evaluate in the remediation decision process. Various analysis methods were employed to determine elemental compositions, heating values, thermal and emission characteristics. This evaluation process may be used as a general methodology for the determination of petroleum-contaminated sediment as a supplemental fuel that may have merit to be considered as a sustainable remediation option.     

A new approach to characterize emission contributions from area sources during optical remote sensing technique testing

In the method termed “Other Test Method-10,” the U.S. Environmental Protection Agency has proposed a method to quantify emissions from nonpoint sources by the use of vertical radial plume mapping (VRPM) technique. The surface area of the emitting source and the degree to which the different zones of the emitting source are contributing to the VRPM computed emissions are often unknown. The objective of this study was to investigate and present an approach to quantify the unknown emitting surface area that is contributing to VRPM measured emissions. Currently a preexisting model known as the “multiple linear regression model,” which is described in Thoma et al. (2009 Thoma, E.R., Green, R., Hater, G., Goldsmith, C., Swan, N., Chase, M. and Hashmonay, R. 2010. Development of EPA OTM-10 for landfill applications. J. Environ. Eng., 136: 769–776. [Crossref], [Web of Science ®] , [Google Scholar]), is used for quantifying the unknown surface area.

The method investigated and presented in this paper utilized tracer tests to collect data and develop a model much like that described in Thoma et al. (2009 Thoma, E.R., Green, R., Hater, G., Goldsmith, C., Swan, N., Chase, M. and Hashmonay, R. 2010. Development of EPA OTM-10 for landfill applications. J. Environ. Eng., 136: 769–776. [Crossref], [Web of Science ®] , [Google Scholar]). However, unlike the study used for development of the multiple linear regression model, this study is considered a very limited study due to the low number of pollutant releases performed (seven total releases). It was found through this limited study that the location of an emitting source impacts VRPM computed emissions exponentially, rather than linearly (i.e., the impact that an emitting source has on VRPM measurements decreases exponentially with increasing distances between the emitting source and the VRPM plane). The data from the field tracer tests were used to suggest a multiple exponential regression model. The findings of this study, however, are based on a very small number of tracer tests. More tracer tests performed during all types of climatic conditions, terrain conditions, and different emissions geometries are still needed to better understand the variation of capture efficiency with emitting source location. This study provides a step toward such an objective.

Implications The findings of this study will aid in the advancement of the VRPM technique. In particular, the contribution of this study is to propose a slight improvement in how the area contributing to flux is determined during VRPM campaigns. This will reduce some of the technique's inherent uncertainties when it is employed to estimate emissions from an area source under nonideal conditions.     

Changes in elemental uptake and arbuscular mycorrhizal colonisation during the life cycle of Thlaspi praecox Wulfen

Elemental uptake and arbuscular mycorrhizal (AM) colonisation were studied during the life cycle of field collected Cd/Zn hyperaccumulating Thlaspi praecox (Brassicaceae). Plant biomass and tissue concentrations of Cd, Pb, Zn, Fe and Ni were found to vary during development, while no variation in P, K, Ca, Mn and Cu tissue concentrations were observed. The lowest Cd bioaccumulation in rosette leaves (BAF(RL)) observed during seeding was partially attributed to lower translocation from roots to rosette leaves and partially to high translocation to stalks, indicating a high Cd mobility to reproductive tissues, in line with our previous studies. The highest intensity of AM colonisation (M%) was observed in the flowering phase and was accompanied by increased root Cd, Zn, Pb and Fe contents. In addition, a positive correlation between AM colonisation and Fe contents in rosette leaves was found. The results indicate developmental dependence of AM formation, accompanied by selective changes in nutrient acquisition in T. praecox that are related to increased plant needs, and the protective role of AM colonisation on metal polluted sites during the reproductive period.     

3D-QSAR of fungal quorum-sensing inhibiting analogs of farnesol

Thirty-four analogs with variable antifungal activity were selected to develop models for establishing three-dimensional quantitative structure-activity relationships (3D-QSAR). Comparative molecular field analysis (CoMFA) and comparative similarity indices analyses (CoMSIA) were conducted on the group of analogs to determine the structural requirements for selectivity and potency in inhibiting biofilm formation and fungal growth. The best CoMFA model predicted a q(2) = 0.5 and an r(2) = 0.991, and revealed that electrostatic properties play a significant role in potency and selectivity. The best CoMSIA model combined electrostatics, hydrogen bond acceptor and donor, and hydrophobic fields with a q(2) = 0.664 r(2) = 0.952, S = 0.099, and F = 139.892. The analyses of the contour maps from both models provide significant insight into the structural necessities for a potent compound. Therefore, manipulating various chemical properties of the substituted groups on the farnesol chain can be used to enhance the fungicidal properties of the target compound.     

Development of molecular marker source profiles for emissions from on-road gasoline and diesel vehicle fleets

As part of the Gasoline/Diesel PM Split Study, relatively large fleets of gasoline vehicles and diesel vehicles were tested on a chassis dynamometer to develop chemical source profiles for source attribution of atmospheric particulate matter in California's South Coast Air Basin. Gasoline vehicles were tested in cold-start and warm-start conditions, and diesel vehicles were tested through several driving cycles. Tailpipe emissions of particulate matter were analyzed for organic tracer compounds, including hopanes, steranes, and polycyclic aromatic hydrocarbons. Large intervehicle variation was seen in emission rate and composition, and results were averaged to examine the impacts of vehicle ages, weight classes, and driving cycles on the variation. Average profiles, weighted by mass emission rate, had much lower uncertainty than that associated with intervehicle variation. Mass emission rates and elemental carbon/organic carbon (EC/OC) ratios for gasoline vehicle age classes were influenced most by use of cold-start or warm-start driving cycle (factor of 2-7). Individual smoker vehicles had a large range of mass and EC/OC (factors of 40 and 625, respectively). Gasoline vehicle age averages, data on vehicle ages and miles traveled in the area, and several assumptions about smoker contributions were used to create emissions profiles representative of on-road vehicle fleets in the Los Angeles area in 2001. In the representative gasoline fleet profiles, variation was further reduced, with cold-start or warm-start and the representation of smoker vehicles making a difference of approximately a factor of two in mass emission rate and EC/OC. Diesel vehicle profiles were created on the basis of vehicle age, weight class, and driving cycle. Mass emission rate and EC/OC for diesel averages were influenced by vehicle age (factor of 2-5), weight class (factor of 2-7), and driving cycle (factor of 10-20). Absolute and relative emissions of molecular marker compounds showed levels of variation similar to those of mass and EC/OC.     

Release of fluorocarbons from insulation foam in home appliances during shredding

It is a current practice that refrigerators and freezers in many countries are shredded after the end of useful lives. The shredder residue is deposited in landfills. During the shredding process a significant fraction of blowing agent (BA) in the insulation foam may be released into the atmosphere. The objective of this study is to determine the fraction of BA released from foam during shredding, by comparing the BA content in insulation foam of refrigerator units before shredding with the BA content of shredded foam. All foam samples analyzed were manufactured with trichlorofluoromethane [CFC-11 (CCl3F)] as BA. The average content of BA in the insulation foam from eight U.S. refrigerator units manufactured before 1993 was found to be 14.9% +/- 3.3% w/w. Several refrigerator units also identified as being manufactured before 1993 were stockpiled and shredded at three shredder facilities, of which one was operated in both wet and dry modes. The selected shredder facilities represent typical American facilities for shredding automobiles, refrigerators, freezers, and other iron containing waste products. Shredded material was collected and separated on location into four particle size categories: more than 32 mm, 16-32 mm, 8-16 mm, and 0-8 mm. Adjusting for sample purity, it was found that the majority (>81%) of the foam mass was shredded into particles larger than 16 mm. The smallest size fraction of foam (0-8 mm) was found to contain significantly less BA than the larger size categories, showing that up to 68% +/- 4% of the BA is released from these fine particles during the shredding process. Because only a minor fraction of the foam is shredded into particles smaller than 8 mm, this has a minor impact on the end result when calculating the total BA release from the shredding process. Comparing BA content in shredded samples from the three shredder facilities with the measured average BA content of the eight refrigerator units, it was found that on average 24.2% +/- 7.5% of the initial BA content is released during the shredding process.     

The influence of organic acids in relation to acid deposition in controlling the acidity of soil and stream waters on a seasonal basis

Much uncertainty still exists regarding the relative importance of organic acids in relation to acid deposition in controlling the acidity of soil and surface waters. This paper contributes to this debate by presenting analysis of seasonal variations in atmospheric deposition, soil solution and stream water chemistry for two UK headwater catchments with contrasting soils. Acid neutralising capacity (ANC), dissolved organic carbon (DOC) concentrations and the Na:Cl ratio of soil and stream waters displayed strong seasonal patterns with little seasonal variation observed in soil water pH. These patterns, plus the strong relationships between ANC, Cl and DOC, suggest that cation exchange and seasonal changes in the production of DOC and seasalt deposition are driving a shift in the proportion of acidity attributable to strong acid anions, from atmospheric deposition, during winter to predominantly organic acids in summer.     

Evaluation of in situ steam‐injection processes for reduction of petroleum compounds within an abandoned canal

A conceptual approach of a novel application of in‐situ thermal processes that would either use a steam injection process or a steam/surfactant injection process was considered to remediate petroleum contaminated sediment residing in an abandoned canal. Laboratory tests were conducted in an attempt to volatilize or mobilize contaminants of concern (selected polycyclic aromatic hydrocarbons [PAHs]) from the contaminated sediment into a phase that could be physically removed. The processes were operated above ambient temperature and pressure in an attempt to increase the removal of the contaminants of concern from the sediment. The ability of both the steam injection process and the steam/surfactant process to remove PAHs from the sediment was considered ineffective; as only two of the seventeen selected PAHs (naphthalene and C1 naphthalene) were associated with a percentage mass reduction greater than 34% for both treatments (four trials). The steam/surfactant injection process generally resulted in higher reductions than the steam injection process, but had larger variances within the two trials using the treatment type. This preliminary evaluation suggests that steam‐based injection processes for removing petroleum contamination from this canal sediment, using the surfactants selected, equipment set‐up, and operating conditions studied, would be considered ineffective. © 2010 Wiley Periodicals, Inc. *

1 This article is a U.S. Government work and, as such, is in the public domain of the United States of America.

     

Selenium stable isotope investigation into selenium biogeochemical cycling in a lacustrine environment: Sweitzer Lake, Colorado

We present a comprehensive set of Se concentration and isotope ratio data collected over a 3-yr period from dissolved, sediment-hosted, and organically bound Se in a Se-contaminated lake and littoral wetland. Median isotope ratios of these various pools of Se spanned a narrow isotopic range (delta80/76Se(SRM-3149)) = 1.14-2.40 per thousand). Selenium (VI) reduction in the sediments is an important process in this system, but its isotopic impact is muted by the lack of direct contact between surface waters and reduction sites within sediments. This indicates that using Se isotope data as an indicator of microbial or abiotic Se oxyanion reduction is not effective in this or other similar systems. Isotopic data suggest that most Se(IV) in the lake originates from oxidation of organically bound Se rather than directly through Se(VI) reduction. Mobilization of Se(VI) from bedrock involves only a slight isotopic shift. Temporally constant isotopic differences observed in Se(VI) from two catchment areas suggest the potential for tracing Se(VI) from different source areas. Phytoplankton isotope ratios are close to those of the water, with a small depletion in heavy isotopes (0.56 per thousand). Fish tissues nearly match the phytoplankton, being only slightly depleted in the heavier isotopes. This suggests the potential for Se isotopes as migration indicators. Volatile, presumably methylated Se was isotopically very close to median values for phytoplankton and macrophytes, indicating a lack of isotopic fractionation during methylation.