Ioana G. Petrisor

Sequestering Agents for Active Caps—Remediation of Metals and Organics

This research evaluated organoclays, zeolites, phosphates, and a biopolymer as sequestering agents for inorganic and organic contaminants. Batch experiments were conducted to identify amendments and mixtures of amendments for metal and organic contaminant removal and retention. Contaminant removal was evaluated by calculating partitioning coefficients. Metal retention was evaluated by desorption studies in which residue from the removal studies was extracted with 1 M MgCl2 solution. The results indicated that phosphate amendments, some organoclays, and the biopolymer, chitosan, were very effective sequestering agents for metals in fresh and salt water. Organoclays were very effective sorbents for phenanthrene, pyrene, and benzo(a)pyrene. Partitioning coefficients for the organoclays were 3000–3500 L g−1 for benzo(a)pyrene, 400–450 L g−1 for pyrene, and 50–70 L g−1 for phenanthrene. Remediation of sites with a mixture of contaminants is more difficult than sites with a single contaminant because metals and organic contaminants have different fate and transport mechanisms in sediment and water. Mixtures of amendments (e.g., organoclay and rock phosphate) have high potential for remediating both organic and inorganic contaminants under a broad range of environmental conditions, and have promise as components in active caps for sediment remediation.

Biopolymer plugging effect: laboratory-pressurized pumping flow studies

The use of biopolymers and their producing microorganisms to form a wide range of impervious barriers, as well as for enhancement of oil recovery (EOR) is already well documented. Both of these important applications of biopolymers are based on their plugging characteristics. Flow systems are essential to examine the plugging effect of biopolymers under different conditions, in order to select suitable biopolymers for a particular application. In the present study, the plugging effect of a number of biopolymers, namely xanthan, polyhydroxybutyrate (PHB), guar gum, polyglutamic acid (PGA) and chitosan, has been investigated in a laboratory-pressurized pumping flow system. The present work is also targeted to study the correlation, if any, between biopolymer structure and plugging effect. The experimental system included a horizontally mounted sand-pack column and provided a constant flow, using a transducer and recording the pressure difference. Thus, the permeability ratio could be evaluated for each biopolymer as models in the field. All of the biopolymers studied have shown positive plugging effects by reducing the permeability of sand over the 11-day experimental period. The best plugging effect was obtained for PHB, which can reach more than a billion-fold permeability reduction, followed by chitosan and PGA, with a million-fold reduction of permeability. These biopolymers can be successfully used alone or in combination in field applications for stabilizing underground contamination to stop the plumes of subsurface pollutants, as well as for improving oil recovery from the field. Our results show that the plugging effect is influenced by the structure of biopolymers. This study will lead to a new method for characterizing the biopolymers used for plugging.

Applied Dendroecology and Environmental Forensics. Characterizing and Age Dating Environmental Releases: Fundamentals and Case Studies

Dendroecology, or the use of ring patterns to assess the age of trees and environmental factors controlling their growth, is a well-developed method in climatologic studies. This method holds great potential as a forensic tool for age dating, contamination assessment, and characterization of releases. Moreover, the method is independent of the physical presence of contamination at the time of sampling because it is focused on the effect rather than the cause. This review is one of the very few articles published to date exploring the forensic applicability of dendroecology. This article is organized in two parts: Part I describes the method principles and proposes a practical procedure for forensic applications; Part II exemplifies and validates the method through six case studies of successful forensic application (related to petroleum products and chlorinated solvent spills).

Stabilization of Metals in Subsurface by Biopolymers: Laboratory Drainage Flow Studies

Environmental contamination with heavy metals and radionuclides remains a major problem worldwide. The current clean-up methodologies are based on energy-intensive engineering processes, which are disruptive and costly. A new universal technology targeted for the permanent enclosure and fixation of nuclear and other extreme hazardous metallic wastes in subsurface sites is needed. Such technology will be useful in treating contamination at many sites in the U.S., with specific applications to Department of Energy (DOE) sites. Biopolymers are potential tools for such an innovative technology. Biopolymers have repeated sequences, and therefore provide ample opportunity for chemical reactions with metals, soil particles, and other biopolymers. They also have the additional ability of creating cross-linking interpenetrating networks that can encapsulate the contaminants. Based on this concept, in the present work five biopolymers (xanthan, chitosan, polyhydroxy butyrate, guar gum, polyglutamic acid) were investigated for potential use in the stabilization of metals in the subsurface. The effects of these biopolymers (used alone and in combinations) on soil characteristics (permeability, shear strength) and their metal uptake ability have been studied using laboratory drainage flow systems. Biopolymer solutions were run through the experimental sandpack columns, followed by copper solution and leaching agents (distilled water and hydrochloric acid). The permeability and shear strength of sand were evaluated. Copper uptake capacity of each biopolymer and combination of biopolymers was also studied along with subsequent leaching. All biopolymers tested improved sand characteristics (by decreasing permeability and increasing shear strength) and had good metal uptake ability (60–90%) with relatively low leachability (10–22%). While biopolymers used alone were more efficient in metal uptake, the combination of two biopolymers (xanthan and chitosan) had an increasing plugging effect. These results show the potential of using biopolymers in subsurface metal stabilization.

Evaluation of biopolymer-modified concrete systems for disposal of cathode ray tube glass.

Abstract Cathode ray tubes (CRTs) from computer monitors and television sets, which contain significantly high percentage of lead (Pb) by weight, represent an enormous and growing hazardous waste problem in the United States and worldwide. As a result, new technologies are needed to cope with current CRT waste stream and increased hazard and build new markets for its recycled components, developing commercially viable concrete composites, as well as minimizing CRT disposal problems. In this study, commercially available biopolymers, such as xan-than gum, guar gum, and chitosan, were used to encapsulate CRT glass waste, reducing the Pb leachability. The biopolymers utilized contain a number of useful functional groups, such as carboxyl (xanthan), hydroxyl (guar), and amino groups (chitosan), which play important roles in binding and stabilizing Pb onto concrete structures. The use of biopolymers in concrete systems can create a stable interpenetrating cross-linking composite that will last for many years. Results from these new composites show 30% higher compressive strength than standard concrete and a sharp decrease in lead leachability from several thousand milligrams per liter initially to an amount of three-tenths milligrams per liter or lower values (much lower than the U.S. Environment Protection Agency standard for hazardous waste of 5 mg/L by the toxicity characteristic leaching procedure test), and for some of the composites leachability is below even the standard for drinking water. This efficient and cost-effective CRT–biopolymer-concrete composite is a new class of biopolymer-modified material that can potentially perform a significant role in relieving the current CRT issue.

Focus on Perchlorate

Perchlorate is rapidly gaining dominance as a global contaminant of the 2000s. Although manufactured and used for a long time (since the 1940s in the United States), perchlorate has only recently emerged as contaminant of concern, in close connection with the advances in knowledge and analysis methods. The increasing number of perchlorate detections in water wells, vegetal (crops), and animal products (cow’s milk) nationwide, its alleged health impacts at low concentrations potentially affecting general human metabolism (due to its inhibition of the thyroid function), along with its environmental persistence (high solubility and resistance to degradation) and travel capacity in water without retardation are all concurring, transforming the way we visualize the global impact of perchlorate in the environment.

INNOVATIVE IN-SITU REMEDIATION OF CONTAMINATED SEDIMENTS FOR SIMULTANEOUS CONTROL OF CONTAMINATION AND EROSION

New technologies are needed that neutralize contaminant toxicity and control physical transport mechanisms that mobilize sediment contaminants. The last 12 months of this comprehensive project investigated the use of combinations of sequestering agents to develop in situ active sediment caps that stabilize mixtures of contaminants and act as a barrier to mechanical disturbance under a broad range of environmental conditions. Efforts focused on the selection of effective sequestering agents for use in active caps, the composition of active caps, and the effects of active cap components on contaminant bioavailability and retention. Results from this project showed that phosphate amendments, some organoclays, and the biopolymer, chitosan, were very effective at removing metals from both fresh and salt water. These amendments also exhibited high retention (80% or more) of most metals indicating reduced potential for remobilization to the water column. Experiments on metal speciation and retention in contaminated sediment showed that apatite and organoclay can immobilize a broad range of metals under both reduced and oxidized conditions. These studies were followed by sequential extractions to evaluate the bioavailability and retention of metals in treated sediments. Metal fractions recovered in early extraction steps are more likely to be bioavailable and were termed the Potentially Mobile Fraction (PMF). Less bioavailable fractions collected in later extraction steps were termed the Recalcitrant Factor (RF). Apatite and organoclay reduced the PMF and increased the RF for several elements, especially Pb, Zn, Ni, Cr, and Cd. Empirically determined partitioning coefficients and modeling studies were used to assess the retention of organic contaminants on selected sequestering agents. Organoclays exhibited exceptionally high sorption of polycyclic aromatic hydrocarbons as indicated by a comparison of K{sub d} values among 12 amendments. These results suggested that organoclays have high potential for controlling organic contaminants. Measured partitioning coefficients were used to model the time required for a contaminant to penetrate sediment caps composed of organoclay. The results showed that a thin layer of highly sorptive organoclay can lead to very long migration times, perhaps longer than the expected lifetime of the contaminant in the sediment environment. A one-dimensional numerical model was used to examine the diffusion of metals through several cap material based on measured and assumed material and transport properties. These studies showed that active caps composed of apatite or organoclay have the potential to delay contaminant breakthrough due to diffusion by hundreds of years or more compared with passive caps composed of sand. Advectively dominated column experiments are currently underway to define effective sorption related retardation factors in promising amendments for various hydrophobic organic compounds. Upon completion of these experiments, advection transient models will be used to estimate the time required for the breakthrough of various contaminants in caps composed of different experimental materials. Biopolymer products for inclusion in active caps were evaluated on the basis of resistance to biodegradation, sorption capacity for organic and inorganic contaminants, and potential for erosion control. More than 20 biopolymer products were evaluated resulting in the selection of chitosan/guar gum cross-linked with borax and xanthan/chitosan cross-linked with calcium chloride for inclusion in active caps to produce a barrier that resists mechanical disturbance. A process was developed for coating sand with cross-linked biopolymers to provide a means for delivery to the sediment surface. Properties of biopolymer coated sand such as carbon fraction (indicating biopolymer coverage), porosity, bulk density, and biodegradability have been evaluated, and experiments are currently underway to assess the resistance of biopolymer coated sand to erosion. Although the ability of active cap materials to remediate contaminants has been emphasized in this study, it is also important to ensure that these materials do not have deleterious effects on the environment. Therefore, promising amendments were evaluated for toxicity using 10 day sediment toxicity tests, the standardized Toxicity Characteristic Leaching Procedure (TCLP), and measurement of metal concentrations in aqueous extracts from the amendments. Metal concentrations were below TCLP limits, EPA ambient water quality criteria, and other ecological screening values These results showed that apatite, organoclay, and biopolymer coated sand do not release metals. The sediment toxicity tests indicated that apatite and biopolymer coated sand are unlikely to adversely affect benthic organisms, even when used in high concentrations.

Sampling and Analyses—Key Steps of a Forensics Investigation

Environmental forensics is a scientific field propelled by the complexity of today’s contamination events and the need to recover investigative and remedial costs, often in the range of millions of dollars. This environmental “detective work” is unique in the fact that it relies upon many divergent skills and knowledge from other scientific fields, combining multiple methods and approaches, and operating at the interface junction points of several main sciences including chemistry and biochemistry, biology, geology and hydrogeology, physics, statistics, and modeling. Legal considerations are similarly a component of most forensic investigations, thereby providing an interesting and “real world” aspect between the environmental law and basic and applied sciences. While there are no established patterns, environmental forensic investigations involve and are based on two main sources of information: the documentary record, including statements by witnesses and other knowledgeable individuals, and the measurement and interpretation of sampling data. Without actual field measurements, there is no forensic case and no assumptions to be made. The analytical data provides the skeleton on which forensic studies and interpretations are built. Forensic investigations commence from apparently straightforward sampling data. But what if this data is inaccurate, nonrepresentative, or an error? The mere existence of data and the ability to acquire it does not necessarily imply data accuracy or suitability to represent and/or reconstruct a contamination event. If the informational skeleton is not accurate, then subsequent interpretations of the data simply perpetuate this inaccuracy or bias, or both. Most environments are complex systems and introduce a variety of potential biases in the sampling and analysis of samples. Transformations and interferences are simple examples of the problems associated with environmental samples. Current advances in sampling and analyzing procedures and equipment can overcome many limitations, provided they are properly used and understood and, most importantly, their existence is known to the forensic community. Only a thorough knowledge of what is available and scientifically acceptable for sampling and analyses, associated with their limitations and proven performances, will insure that appropriate analytical data is generated for interpretation. Until knowledge of the proper sampling and analytical techniques and associates bias are thoroughly known, the development of a forensic hypothesis is of limited value. The importance of sampling and analysis in forensic studies is unquestionable. This issue is dedicated to sampling techniques with the central topic being the representativeness of environmental samples. Defining the investigative goals and using the proper sampling tools and methods to obtain reliable data is achieved through a clear understanding of the meaning of “representativeness.” What, therefore, is “representativeness” and what is it representative of? And how are representative samples acquired? The answers to these questions provide the key for obtaining reliable forensic data. In this issue, several papers (by Warren, by Ramsey, and by Mattuck et al.) discuss the concept of representative data in different environmental contexts, while others (by Gilbert and Pulsipher and by Nocerino et al.) propose practical approaches and sampling designs to assess and attain representativeness. Two other papers (by Jenkins et al. and by Feenstra) dealing with representative sampling for two main classes of specific contaminants, namely energetic compounds at military training ranges and NAPLs (non-aqueous phase liquids), propose practical procedures for sampling collection according to investigation goals. An innovative technique for estimation arsenic contamination in groundwater is also proposed and presented by Clark et al. This method provides direct in situ cumulative measures of water and contaminant fluxes in groundwater, with the ability for continuous sampling and monitoring arsenic in the environment. Several basic forensics methods for assessing the poultry litter as potential source for arsenic in household dusts, with subsequent health implications are further presented in the paper of O’Connor et al. And, last but not least, a review of the state-of-the-art forensics techniques for fingerprinting and age-dating of gasoline releases, followed by their application in a particular case study, is presented in the paper of Oudijk. The goal of these papers is to provide you with information that emphasizes the importance of sampling and analysis techniques as key factors of environmental forensics investigations. It is our hope that this information will assist you in designing and conducting your own reliable forensic investigations and will challenge you to consider new techniques to achieve these same goals. Ioana G. Petrisor Managing Editor

Use of Oxygenates to Date a Gasoline Release

Oxygenates include a number of chemical compounds (containing functions with oxygen) that have been used as gasoline additives to improve gasoline characteristics and combustion in the United States (U.S.) and worldwide over the years. Apart from ethanol that was mixed with gasoline in the Midwest U.S. prior to World War II, the other oxygenates were more recently added to gasoline. Thus, from about 1980, with the phase-out of lead additives, a peak in the use of oxygenates as alternatives to organic lead in gasoline occurred. Apart from ethanol, the most common oxygenate compounds used include: methyl tertiary butyl ether (MTBE), tertiary amyl methyl ether (TAME), tertiary butyl alcohol (TBA), ethyl tertiary butyl ether (ETBE), di-isopropyl ether (DIPE), and tertiary amyl ethyl ether (TAEE). The relatively recent introduction of most oxygenates as gasoline additives, as well as variation in the types or combination of oxygenates used and the different chronological changes in the total amount of added oxygenates following legislative changes (in order to meet a certain amount of total oxygen needed for burning gasoline), are the basis for the forensic use of oxygenates to determine the age and possibly the source of gasoline spills. This editorial points out some major changes in the total amount and composition of oxygenates in the past several decades that can be used as starting point to age-date relatively recent (post1980s) gasoline releases in environment. Along with such general information, for an accurate age dating process one should account for the (bio)degradation rates of different oxygenates as well as specific environmental conditions that determine the time required for the release of oxygenates from an initial nonaqueous phase liquid (NAPL) spill and thus the starting point of most degradation processes. Several hints in this respect are also given in addition to few useful references. This editorial is intended to be useful by providing general guidance on how to interpret oxygenate data and estimate gasoline age.

Emerging Contaminants—The Growing Problem

Finding solutions to the complex environmental problems of today’s society involves a thorough understanding of the processes and our perception of the specific contaminants causing these problems. The role of environmental forensics should be critical not only in allocating responsibilities for coverage of remedial costs, but also in evaluating and selecting the best rehabilitation strategy in each case. Environmental forensics techniques should be the keys for identifying specific factors causing contamination and finding the best remedial technology and preventing future pollution events. Emerging contaminants is a generic term used to identify environmental concerns related to the release of new contaminants with unknown effects but with the potential for severe harm. The term can also refer to the discovery of new facts triggering our awareness of the risks posed by previously well-understood contaminants. Today, the term emerging contaminants is often used in scientific articles, journals, and news articles to refer to a wide range of chemicals with apparently unrelated characteristics and uses. So, what is emerging? What are the criteria that might qualify a chemical as emergent? The answer to these questions enables us to discern an emerging contaminant before it is released in the environment and thus prevent future contamination events. It may be helpful to explore the use of several specific criteria to identify emerging contaminants with the hope of increasing our awareness and understanding of this growing problem and to provide insight for future identification in order to prevent contamination events. When identifying priority pollutants, persistence, bioaccumulation, and toxicity are the primary factors to consider when estimating a chemical’s risk to humans and the environment. The reassessment of these well-established traits provides new criteria for identifying emergent contaminants. Thus, apart from the chemical structural stability, there are others factors that can make a contaminant persistent. One is if the chemical is being continually released. In the case of sewage sludge wastes, these are released continuously into receiving water streams. Therefore, each contaminant should be integrated into the specific associated environmental conditions in order to establish its potential to result in emergent contamination. Another aspect is bioaccumulation or the ease by which a chemical penetrates and accumulates in living organisms. In this context, the ability to bind to lipids and fats is one factor that can facilitate the chemical accumulation in organisms. Another factor is the size or dimension of the contaminant particle, as in the case of nanoparticles. Their small, subcellular scale facilitates their entrance and transport within cells. Such traits should be considered when assessing the bioaccumulation potential of a certain contaminant and its subsequent possible classification as emergent. Another criterion for determining emerging pollutants is their potential to cause cancer. For many contaminants, there is recent data suggesting possible cancer effects on humans. These contaminants are classified as reasonably anticipated human carcinogens based on sufficient evidence in experimental animals by the International Agency for Research on Cancer (IARC), the National Toxicology Program (NTP), or the USEPA. A few examples of so-called emerging contaminants that have been classified this way include 1,4-dioxane, N-nitrosodimethylamine (NDMA), 1,2,3-tricholoropropane (TCP), or 1,2-dichloroethane (1,2-DCA). The potential for interference and disruption of physiological functions is also a criterion for classifying emerging contaminants. Recent data show that many chemicals can act as endocrine disruptors by interfering with the hormonal systems of living organisms. These chemicals can be active at very low levels and may interfere with hormone balance by mimicking, enhancing, or inhibiting the effects of hormones.Various substances are suspected to be endocrine disruptors, including nonylphenols and their ethoxylates (common detergents used worldwide), organotins, phthalates, PCBs, DDT and other organochlorine pesticides, dioxins, etc. Currently, the EPA’s endocrine disruptor screening program is looking for such chemicals in order to identify and regulate them as “emerging.” The potential effects at low levels on a long-term exposure scenario is another aspect to consider when looking for potential emerging contaminants. Humans are constantly exposed to a variety of contaminants at very low levels. Arsenic and radionuclides are examples of “old” contaminants that may be considered “emergent” on a long-term exposure scenario basis. Thus, the toxicological significance of ultralow dose exposure needs to be better understood, while the concern is heightened for those organisms that suffer continual, multigenerational exposure to complex mixtures of low-level toxicants.