James S. Bonner

MODELING COAGULATION KINETICS INCORPORATING FRACTAL THEORIES: A FRACTAL RECTILINEAR APPROACH

Abstract Conventional coagulation kinetic models are usually based on Smoluchowski’s work, which employs the coalesced sphere assumption. Much evidence, however, has recently been provided that particle aggregates from natural waters and engineered systems have fractal structures. Consequently, the traditional models should be modified to include the fractal nature of aggregates. This paper describes a modeling approach that simulates changes in particle size distribution (PSD) due to coagulation by incorporating recently proposed fractal mathematics and introducing a new conceptual framework called the coalesced fractal sphere (CFS) assumption. The developed modeling method, which includes the traditional Euclidean case as a subset, was applied to a 2-m settling column system with estuarine sediment particles, and a one-dimensional numerical model was developed. Model simulations were conducted varying the fractal dimension ( D F ) and the collision efficiency factor ( α ). For the conventional Euclidean case, the model indicated that coagulation played an important role in the vertical transport of the estuarine sediment particles. The simulations with the fractal cases indicated that both D F and α significantly affected the evolution of PSD, and that with lower values of D F and α , the model predicted a trend of PSD similar to that of the Euclidean case. This finding may be interpreted as dependence of α on the assumed collision models (or D F ), that seems to leave a new challenge to our understanding of α . The developed model may be used in various particle aggregation systems.

Comparative toxicity of oil, dispersant, and oil plus dispersant to several marine species

Dispersants are a preapproved chemical response agent for oil spills off portions of the U.S. coastline, including the Texas-Louisiana coast. However, questions persist regarding potential environmental risks of dispersant applications in nearshore regions (within three nautical miles of the shoreline) that support dense populations of marine organisms and are prone to spills resulting from human activities. To address these questions, a study was conducted to evaluate the relative toxicity of test media prepared with dispersant, weathered crude oil, and weathered crude oil plus dispersant. Two fish species, Cyprinodon variegatus and Menidia beryllina, and one shrimp species, Americamysis bahia (formerly Mysidopsis bahia), were used to evaluate the relative toxicity of the different media under declining and continuous exposure regimes. Microbial toxicity was evaluated using the luminescent bacteria Vibrio fisheri. The data suggested that oil media prepared with a chemical dispersant was equal to or less toxic than the oil-only test medium. Data also indicated that continuous exposures to the test media were generally more toxic than declining exposures. The toxicity of unweathered crude oil with and without dispersant was also evaluated using Menidia beryllina under declining exposure conditions. Unweathered oil-only media were dominated by soluble hydrocarbon fractions and found to be more toxic than weathered oil-only media in which colloidal oil fractions dominated. Total concentrations of petroleum hydrocarbons in oil-plus-dispersant media prepared with weathered and unweathered crude oil were both dominated by colloidal oil and showed no significant difference in toxicity. Analysis of the toxicity data suggests that the observed toxicity was a function of the soluble crude oil components and not the colloidal oil.

Microbial degradation of crude oil in marine environments tested in a flask experiment

Abstract Thirteen different bioremediation products were evaluated for their effectiveness in biodegrading petroleum hydrocarbons. All 13 products tested in this experiment were listed on the NCP product schedule. Of these 13 products, 12 were bioaugmentation agents and one was a biostimulation agent. All the products were tested for toxicity levels initially, using standardized protocols. The products were sampled and analyzed three times over a 28-day period for most-probable number (MPN) of hydrocarbon degraders and total petroleum hydrocarbon as separate fractions. A subsample was analyzed for MPN, and the rest of the sample was extracted and fractionated in total saturated petroleum hydrocarbons (TsPH) and total aromatic petroleum hydrocarbons (TarPH). This experiment revealed that the petroleum hydrocarbons were biodegraded to an extent significantly greater than that achieved by the naturally occurring microorganisms. After 28 days, some products reduced the TsPH fraction to 60% of its initial weight and the TarPH fraction to 65%. Three of the 13 products tested enhanced microbial degradation of the petroleum to a degree significantly better than the nutrient control treatments. Of these three products, only one showed a toxicity level below that of the control treatment.

Intrinsic bioremediation of a petroleum-impacted wetland

Following the 1994 San Jacinto River flood and oil spill in southeast Texas, a petroleum-contaminated wetland was reserved for a long-term research program to evaluate bioremediation as a viable spill response tool. The first phase of this program, presented in this paper, evaluated the intrinsic biodegradation of petroleum in the contaminated wetland. Sediment samples from six test plots were collected 11 times over an 11-month period to assess the temporal and spatial petroleum concentrations. Petroleum concentrations were evaluated using gas chromatography-mass spectrometer analyses of specific target compounds normalized to the conservative biological marker, C(30)17alpha,21beta(H)-hopane. The analyses of specific target compounds were able to characterize that significant petroleum biodegradation had occurred at the site over the one-year period. Total resolved saturate and total resolved aromatic hydrocarbon data indicated the petroleum was degraded more than 95%. In addition, first-order biodegradation rate constants were calculated for the hopane-normalized target compounds and supported expected biodegradation patterns. The rapid degradation rates of the petroleum hydrocarbons are attributed to conditions favorable to biodegradation. Elevated nutrient levels from the flood deposition and the unconsolidated nature of the freshly deposited sediment possibly provided a nutrient rich, oxic environment. Additionally, it is suggested that an active and capable microbial community was present due to prior exposure to petroleum. These factors provided an environment conducive for the rapid bioremediation of the petroleum in the contaminated wetland.

Behavior of a chemically-dispersed oil and a whole oil on a near-shore environment

Abstract To investigate the use of dispersants as an oil spill chemical countermeasure in the surf-zone, a simulated oil spill was conducted at the Shoreline Environmental Research Facility (SERF), formerly known as the Coastal OilSpill Simulation System (COSS), a wave tank facility in Corpus Christi, Texas. Sand was added to each tank to establish a beach with a prescribed slope of 10 degrees. Natural seawater flowed continually through the system to emulate alongshore currents. The replicated experimental treatments included pre-mixed oil plus dispersant (three tanks), oil only (three tanks), and unoiled controls (two tanks). Known amounts of either whole oil or dispersed oil were added to the respective tanks. Both the sediment and water column were periodically sampled during the 10-day experiment, and a materials balance on the oil was determined for both oil treatments. The environmental compartments where oil accumulated were sediments, water column, and non-aqueous-phase layer. The discharge from the tanks was presumed to be the primary sink, as water was drawn from the tanks at a known and constant flow rate. Tidal cycles were simulated by varying the computer-controlled influent rate. The oil mass (measured as total petroleum hydrocarbons) for each compartment/sink was calculated using data from four time points. At the experiment’s conclusion, approximately 49% of the applied oil for the oiled treatment remained in the tanks sorbed to sediments or other surfaces. The rest of the oil was removed via the effluent. In the chemically-dispersed oil treatment, all of the oil was flushed from the tanks; no oil (≪1%) remained on the sediments. These studies indicate that a timely dispersant application to spilled oil can reduce residual oil accumulation on beach substrates.

Algal-Available Particulate Phosphorus in the Great Lakes Basin☆

For the purpose of comparing the relative availability of particulate phosphorus (P) from various sources to the Great Lakes, algal-available P was determined on suspended solids and bottom sediments from tributaries, wastewater suspended solids, lake bottom sediments, and eroding bluff solids from the region. Physicochemical and bioassay methods were used to estimate the rate and extent of available P release from particulates. Considering all types of particulates examined, ultimately available P ranged from nil to approximately 70 percent of total phosphorus (Total-P) content. During algal bioassays, changes in levels of base-extractable inorganic P (R-NaOH-P) in tributary suspended solids were nearly equivalent to the amounts of P used by algae during bioassays. For the tributary solids, ultimately available P averaged approximately 90 percent of R-NAOH-P. Consistent differences were found in amounts of available P among particles from different sources. Sources of particle-bound P ranked in order of decreasing availability were: wastewater solids, lake bottom sediments, tributary solids, and eroding bluff solids. Differences in available P release rates also existed among the different types of particles. Wastewater solids displayed the largest first-order release rates, eroding bluff samples and tributary-suspended solid samples that were high in apatite showed essentially no available P release, while other tributary suspended solids displayed intermediate release rates.

Modeling coagulation kinetics incorporating fractal theories: comparison with observed data

There are currently four possible approaches in modeling coagulation kinetics: the traditional Euclidean rectilinear; the Euclidean curvilinear; the fractal rectilinear; and the fractal curvilinear. The fractal model includes the Euclidean case as a subset. The primary purpose of this research is to investigate which of the rectilinear models among these best predicts the evolution of experimental observed particle size distribution (PSD). Using a fractal rectilinear model previously developed by the authors, model predictions were compared with a series of observed PSD data obtained from estuarine sediment particles in a 2m settling column, where the average velocity gradient (G) was 20 or 40s(-1). Nonlinear parameter estimation was performed to estimate two free parameters for the fractal model (the fractal dimension, DF, and the collision efficiency factor, a), and one free parameter (the collision efficiency factor, alpha) for the Euclidean model. Compared with the observed PSD, the simulation showed that the fractal rectilinear model was best, and that this model fit better for the larger size particles. The estimated DF was between 2.6 and 3.0. The research demonstrated that the alphas have multiple values for the same observed data, depending on the coagulation model used. This finding is significant because a is currently used as a single value based on the conventional Euclidean rectilinear model.

Method for quantifying the fate of petroleum in the environment

Abstract Petroleum is a complex mixture of a wide range of hydrocarbon and non-hydrocarbon compounds of various physical and chemical properties. In recent years, the research on the fate of petroleum in the environment has required analytical methods that can provide more detailed information on the components of petroleum than traditional standard methods. The analytical method presented for aqueous, sediment, and soil samples provides several levels of information on petroleum in the environment.The Total Extractable Materials (TEM) analysis provides a gross measure of petroleum in the environment using methylene chloride extraction and gravimetric analysis. Gross composition analysis separates the methylene chloride extract into a saturate hydrocarbon, an aromatic hydrocarbon, and a polar fraction each measured gravimetrically. In contrast, the target compound analysis provides a detailed measure by GC-MS of 62 specific compounds. Normalization to the conservative compound, 17α,2l -(H)Hopane, is incorporated into the method to reduce the effects of sample and site heterogeneity. Quality control and quality assurance procedures are integral parts of these analyses to assure the validity of the resulting data. A sample data set from a biological augmentation product evaluation was used only to illustrate the interpretation of the petroleum chemistry. In this example, conclusions were dependent on the criteria for evaluating the fate of petroleum. As the product evaluation progressed through the petroleum chemistry method, the conclusion on the their effectiveness changed. Therefore, proper interpretation of the petroleum chemistry, which is dependent on the method, is necessary to correctly evaluate the fate of petroleum in the environment.

Solubility of petroleum hydrocarbons in oil/water systems

Abstract To elucidate mechanisms, two laboratory-scale experiments were correlated to understand and quantify how oil partitions into the aqueous phase. In the two experiments, free-phase petroleum was exposed to water in an effort to determine aqueous concentrations of various oil components. In the first investigation, an oil/water system was allowed to equilibrate for 16 days. The water column in the system was periodically sampled, and sample analysis was performed by GC-MS. After analyzing for naphthalene and various alkyl-substituted naphthalene compounds, the data was modeled and rate coefficients and the saturation concentrations were predicted. For naphthalene, the modeled saturation concentration was 1.4×10 −6 mol/l , the rate coefficient was 0.239 h −1 and the predicted time to reach equilibrium was 19.3 h. For the alkyl-substituted compounds, there was an inverse correlation between both the rate coefficients and saturation concentrations and the degree of alkyl-substitution. In the second investigation, oil/water systems were allowed to equilibrate for 36 h. Various oil loadings (mass of oil/volume of water) were investigated. The mixing energy was twice that of the first experiment. After the 36 h, the water column was sampled and analyzed by GC-MS. There was a direct correlation between the measured total petroleum hydrocarbon (TPH) concentrations in the water and the oil loading. However, there was no such correlation between the naphthalenes and oil loading. It was concluded that the first experiment was a solubility phenomenon while the second experiment also included a colloidal phenomenon.

Prevention of hereditary angioedema attacks with a subcutaneous C1 inhibitor

BACKGROUND Hereditary angioedema is a disabling, potentially fatal condition caused by deficiency (type I) or dysfunction (type II) of the C1 inhibitor protein. In a phase 2 trial, the use of CSL830, a nanofiltered C1 inhibitor preparation that is suitable for subcutaneous injection, resulted in functional levels of C1 inhibitor activity that would be expected to provide effective prophylaxis of attacks. METHODS We conducted an international, prospective, multicenter, randomized, double‐blind, placebo‐controlled, dose‐ranging, phase 3 trial to evaluate the efficacy and safety of self‐administered subcutaneous CSL830 in patients with type I or type II hereditary angioedema who had had four or more attacks in a consecutive 2‐month period within 3 months before screening. We randomly assigned the patients to one of four treatment sequences in a crossover design, each involving two 16‐week treatment periods: either 40 IU or 60 IU of CSL830 per kilogram of body weight twice weekly followed by placebo, or vice versa. The primary efficacy end point was the number of attacks of angioedema. Secondary efficacy end points were the proportion of patients who had a response (≥50% reduction in the number of attacks with CSL830 as compared with placebo) and the number of times that rescue medication was used. RESULTS Of the 90 patients who underwent randomization, 79 completed the trial. Both doses of CSL830, as compared with placebo, reduced the rate of attacks of hereditary angioedema (mean difference with 40 IU, –2.42 attacks per month; 95% confidence interval [CI], –3.38 to –1.46; and mean difference with 60 IU, –3.51 attacks per month; 95% CI, –4.21 to –2.81; P<0.001 for both comparisons). Response rates were 76% (95% CI, 62 to 87) in the 40‐IU group and 90% (95% CI, 77 to 96) in the 60‐IU group. The need for rescue medication was reduced from 5.55 uses per month in the placebo group to 1.13 uses per month in the 40‐IU group and from 3.89 uses in the placebo group to 0.32 uses per month in the 60‐IU group. Adverse events (most commonly mild and transient local site reactions) occurred in similar proportions of patients who received CSL830 and those who received placebo. CONCLUSIONS In patients with hereditary angioedema, the prophylactic use of a subcutaneous C1 inhibitor twice weekly significantly reduced the frequency of acute attacks. (Funded by CSL Behring; COMPACT EudraCT number, 2013‐000916‐10, and ClinicalTrials.gov number, NCT01912456.)