Future Developments in Organic Pollutant Identification and Characterization

Most of the development work on organic pollutants has resulted from the use of GC-MS and synthesis of authentic standards or surrogate standards. However, with advances in other techniques it is clear that this field will benefit by making greater use of alternative identification and characterization methods. The following is a summary of some advances and instrument combinations - Fourier transform infrared spectroscopy (FTIR) can now be combined with GC to provide IR spectra on peaks...

Alicyclic Hydrocarbons

Alicyclic hydrocarbons are saturated carbon chains that form ring structures. Naturally occurring alicyclic hydrocarbons are common (Chap. 1). For example, alicyclic hydrocarbons are a major component of crude oil, comprising 20-67 vol. . Other examples of complex, naturally occurring alicyclic hydrocarbons include camphor (a plant terpene) and cyclohexyl fatty acids (components of microbial lipids).Anthropogenic sources of alicyclic hydrocarbons to the environment include fossil-fuel...

Factors Affecting Biodegradation

It is often difficult to predict the fate of a pollutant in an interfacial microenvironment because the interactions between the microbial, chemical, and physical components of the environment are still not well understood. The total microbial activity at aqueous-solid phase interfaces depends on a variety of factors, such as numbers of microbes, available nutrients, environmental conditions, and pollutant chemical structure. The impact of some of the most important factors affecting microbial...

PCB Compositions

Monsanto Chemical Company was the sole producer of PCBs in the United States, marketing them under the trade name Aroclor.A four-digit number identified the mixture of biphenyls found in a particular product. The first two digits (usually 12) indicated that the mixture contained polychlorinated biphenyls. The second two numbers indicated the percentage of chlorine in the mixture. For example, the name Aroclor 1254 indicates a PCB mixture with 54 chlorine. The only exception to this numbering...

Tl I76

The diffusion coefficient (D) can be calculated using Eq. (76) by plotting Qt vs time and determining the value for the intercept TL. The root time method of data analysis for diffusion coefficient determination was developed by Mohamed and Yong 142 and Mohamed et al. 153 . The procedure used for computing the diffusion coefficient utilizes the analytical solution of the differential equation of solute transport in soil-solids (i.e., the diffusion-dispersion equation) Equation (77) is converted...

Aromatic Hydrocarbons

The aromatic hydrocarbons contain at least one unsaturated ring system with the general structure C6R6, where R is any functional group (see Chap. 1). The parent hydrocarbon of this class of compounds is benzene (C6H6), which exhibits the resonance, or delocalization of electrons, typical of unsaturated cyclic structures. Owing to its resonance energy, benzene is remarkably inert. Aromatic compounds, excluding polycyclic aromatic hydrocarbons (PAHs), which contain one or more benzene rings, are...

Vapor Pressure

Vapor pressure (i.e., VP) is a measure of the amount of contaminant present in the air at a particular temperature (see Sect. 2.1.2).VP is one of the main factors controlling the vaporization of PCBs from aqueous or solid phase environments into the atmosphere. Figure 7 shows the vapor pressure at 25 C for PCB isomers, indicating that VP decreases as the degree of chlorination increases. Many of the PCBs found in the aquatic environment (e. g., in lakes and in the Arctic and Antarctic) have...

Dicamba

Dicamba (3,6-dichloro-2-methoxybenzoic acid) is primarily used as a post-emergence broadleaf herbicide, which interferes with normal plant auxin function, subsequently causing uncontrolled growth and the inhibition of the phototropic and geotropic function. Cumulative response results in plant death. The success of auxinic analogues such as Dicamba and 2,4-dichloropheno-xyacetic acid in weed control has led to widespread manufacturing and use. Estimated U.S. production for Dicamba was 5 million...

Ideal Adsorbed Solution Model

The most common model for describing adsorption equilibrium in multi-component systems is the Ideal Adsorbed Solution (IAS) model, which was originally developed by Radke and Prausnitz 94 . This model relies on the assumption that the adsorbed phase forms an ideal solution and hence the name IAS model has been adopted. The following is a summary of the main equations and assumptions of this model (Eqs. 22-29). The IAS model relates the concentration of solute i in a complex mixture (C1) to a...

Sorption Desorption of Organic Pollutants from Complex Mixtures Modeling Kinetics Experimental Techniques and Transport

T. Simoneit2 1 Department of Civil, Construction and Environmental Engineering, College of Engineering, Oregon State University, 202 Apperson Hall, Corvallis, OR 97331, USA 2 Environmental and Petroleum Geochemistry Group, College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA, Sorption desorption is one of the most important processes influencing movemement of organic pollutants in natural systems. Sorption with...

Detoxification

The most important role of microorganisms in the transformation of pollutants at aqueous-solid phase interfaces is their ability to bring about detoxification (i. e., the change in a molecule that renders it less harmful to one or more susceptible species). Detoxification results in inactivation, with the toxicologically active substance being converted to an inactive product. Because toxicological activity is associated with many chemical entities, substituents, and modes of action,...

Alkylphenol Polyethoxylates

Alkylphenol polyethoxylates (APEO) are a major class of nonionic surfactants over 230 million kg were sold in the United States in 1990 434,435 . They are most important in industrial applications but are also used in institutional and household cleaners and personal care products 436 . In recent years,APEs have received widespread attention in the United States and abroad because of their incomplete elimination during sewage treatment and the detection of their biodegradation intermediates in...

Methyl Bromide

Methyl bromide is presently the most important preplanting soil fumigant commercially available 402 . This compound is used extensively in the United States in the production of many economically important crops for the management of plant-pathogenic nematodes, soil-borne fungi and bacteria, and weeds 403 . This compound is also used as a space fumigant for commodities, for structural pest control, and for quarantine and regulatory purposes. For preplanting soil fumigation, methyl bromide is...

The Carboxyl Group

The carboxyl group (-COOH) of organic acids interacts either directly with the interlayer cation or by forming a hydrogen bond with the water molecules coordinated to the exchangeable cation on the soil-solid and sediment-solid clay particles 17,160 .Adsorption of organic acids depends on the cation polarizing power. Some organic acids can be physically adsorbed onto the clay particles of any solid phase and water bridging is an important mechanism in the adsorption process. In addition to...

Liquid Liquid Extraction

Liquid-liquid extraction (LLE) is based on the partition of organic compounds between the aqueous sample and an immiscible organic solvent. The efficiency of an extracting solvent depends on the affinity of the compound for this solvent, as measured by the partition coefficient (i. e., on the ratio of volumes of each phase and on the number of extraction steps). Solvent selection for the extraction of environmental samples is described and reported in many reviews and recent articles...

Sample Preparation and Handling

As for all trace-level analyses, sample preparation and handling are of crucial importance. In addition to all the usual problems of GC-MS, measurements of isotope ratios must ensure that none of these steps introduce any isotope discrimination. Any chemical reactions, including conversion of the organic sample molecules to the simple gases which are those actually analyzed, must be quantitative (100 conversion) to avoid kinetic isotope effects 627 . Until relatively recently, all gas IRMS...

Chlorinated Hydrocarbons

1,1,2,2-Tetrachloroethane (TeCA) was the first chlorinated hydrocarbon solvent produced in large quantities before World War I 371 . It was used as a solvent for cellulose acetate, fat, waxes, greases, rubber, and sulfur. In a few cases, TeCA is used as a carrier or reaction solvent in manufacturing processes for other chemicals and as an analytical reagent for polymers 371 . TeCA was largely replaced by less toxic solvents after 1945. TeCA release in the United States varied from 44,000 pounds...

Dehalogenation

Many pesticides contain chlorine or other halogens, and removal of the halogen often converts the toxicant to an innocuous product. The enzymes are designated dehalogenases. These dehalogenations may involve replacement of the halogen by H (i.e., reductive dehalogenation, reaction 11), by OH (i.e., hydro-lytic dehalogenation, reaction 12) or it may result in removal of the halogen and an adjacent H (i. e., dehydrodehalogenation, reaction 13) Fig. 6. Detoxification of DDT, Lindane, and Dalapon...

Henrys Law Constant

Generally, the higher the pressure, the higher is the solubility of a gas in a liquid. This relationship is expressed quantitatively by Henry's Law which states that the mass of gas (m) dissolved by a given volume of solvent at a constant temperature is proportional to the gas pressure (p) with which it is in equilibrium If the mass of gas dissolved by the given volume is converted to a concentration term, the pressure to vapor density, the Henry's Law relation may be expressed as where C V and...

Mixture Toxicity Index

The third scheme proposed by Konemann 348 uses a mixture toxicity index (MTI) defined as In this scheme, MTI 1 implies simply additive, MTI 0 implies independent action, MTI < 0 implies antagonism, MTI > 1 implies supra-addition, and 1> MTI > 0 implies partial addition. Broderius and Kahl 349 used this scheme to analyze joint effects of several equitoxic 7-, 14-, and 21-component mixtures, and concluded simple additivity with MTI values ranging from 0.93 to 1.06. Hermens et al. 350...

Free Energy Models

Among the first models proposed using QSAR methods is the one by Hansch and co-workers 60-62,80,102-110,152,195,296 -298 . They proposed that the early observations of the importance of relative lipophilicity to biological potency into the useful formalism of Linear Free Energy Relationships (LFER) to provide a general QSAR model in biological contexts.As a suitable measure of lipophilicity,the partition coefficient (log KOW) between Z-octanol and water was proposed, and it was further...

Conclusions

Understanding environmental partitioning mechanisms of organic pollutants at aqueous-solid phase interfaces (i.e., water-soil, water-sediment, water-suspended solids, water-biosolids) requires the complete knowledge and analysis of most of the important physical and chemical properties of such pollutants. These properties, in some degrees of precision and accuracy, can initially determine the chemodynamics of the pollutants once they are released to the environment. Even through the predicted...

Assimilation of Carbon

Many measurements have been made of the carbon in the organic substrate which is converted into the cells that are carrying out the biodegradation. Such measurements are simple and straightforward in liquid media with water-soluble substrates since the biomass is particulate and thus can be readily distinguished from carbon in solution 47,56,84 - 86 . In contrast, the measurements in soils, wastewater, sewage, or sediments are complicated because (1) other organic particulate matter is present...

Acclimation

Prior to the degradation of many organic compounds, a period is noted in which no destruction of the compound is evident. This time interval is designated as an acclimation period or, sometimes, an adaptation or lag period 93-98 . It may be defined as the length of time between the addition or entry of the compound into an environment and evidence of its detectable loss. During this interval, no change in concentration is noted, but then the disappearance becomes evident and the rate of...

Equilibrium Vapor Pressure

The equilibrium vapor pressure of organic compounds is comparable to solubility in that it is a measure of the volatilization tendency from liquid or solid phases. The equilibrium vapor pressure of a gas can be conceived as its solubility in air. The vapor pressure of a liquid or solid is the pressure of the gas in equilibrium with the liquid or solid at a given temperature. The thermodynamic Clausius-Clapeyron expression (Eq. 1, 31 ) describing this equilibrium is where AH is the heat of...

Pp

- PV the number of pore volumes, - Vp the volume of pores for a given column, - V the cumulative flow volume, and The results of total contaminant concentrations appearing in the effluent from the column are plotted vs pore volume (Fig. 10b). Pore volumes for the SWM column experiments are given in Table 3. Time may be normalized to pore volumes for additional analysis, leading to interferences regarding the trade-off between the mass leaching rate increasing with faster flow rates, but...

Nonionic Compounds

Pesticides of this category (Fig. 10, Table 3) do not ionize significantly in aqueous systems and vary widely in their chemical composition and properties (i.e., water solubility, polarity, molecular volume, and tendency to volatilization). Chlorinated hydrocarbon insecticides are among the most widely known and studied group of nonionic pesticides 151 . DDT, in particular, has been studied more than any other pesticide (Fig. 10, Table 3). It has been implicated as detrimental to numerous...

Clay Fraction

Much of the early work in characterizing the environmental behavior of chemicals was accomplished in the area of agricultural chemistry. Work surrounding the behavior of plant nutrients in the soil has provided a large base of information about the processes of environmental chemistry. Workers investigating the effectiveness of soil-applied herbicides determined that the herbicidal activity of organic chemicals varied with soil properties. It was determined that clay and OM contents of the soil...

Dealkylation

Pesticides containing methyl or other alkyl substituents may be linked to N or O (i.e., N- or O-alkyl substitution). An N- or O-dealkylation catalyzed by microorganisms frequently results in loss of the pesticide activity. Phenylurea (see Chap. 1) becomes less active when microorganisms N-demethylate the molecules (e.g., the conversion of Diuron to the normethyl derivative, Fig. 7). The subsequent removal of the second N-methyl group renders the molecule fully nontoxic 169 . On the other hand,...

Comparative Extraction Studies

Ideally, the pollutants to be determined should be removed from the matrix as completely as possible with a minimum amount of the other non-target components. This type of selectivity was certainly anticipated from supercritical fluid extraction. However, trace organic pollutants cover a wide range of polarity, volatility, and molecular size, making selective extraction very difficult to achieve. Currently the most popular extraction methods are Soxhlet 191,400, 402-404 , blending 189, 408,...

Polycyclic Aromatic Compounds

Aromatic Organic Molecules

Polycyclic aromatic hydrocarbons (PAHs, sometimes also called polynuclear aromatics, PNA) are a hazardous class of widespread pollutants. The parent structures of the common PAHs are shown in Fig. 4 and the alkylated homologs are generally minor in combustion emissions. PAHs are produced by all natural combustion processes (e. g., wild fires) and from anthropogenic activity such as fossil fuels combustion, biomass burning, chemical manufacturing, petroleum refining,metallurgical processes, coal...

Case Study

In the next few sections, a case study of the environmental impact of highway construction and repair materials as well as hazardous solid waste materials is presented and discussed from the view points of sorption desorption processes. Assessment, prediction, and management of the environmental impact of solid waste material (SWM) disposal in landfills and recycled wastes mixed with asphalt that are used as highway construction and repair (C& R) materials on surface and ground waters across...

Van der Waals Attractions

Ionic species can induce a dipole in a nonpolar molecule over a short range. London forces exist between instantaneous and induced dipoles, and are operative between all bodies when they are close together. For molecular systems they are also commonly called van der Waals attractive forces after the Dutch physicist (J.D. van der Waals) who described these forces as being active in crystals 65 . The London van der Waals force is also frequently referred to as the dispersion force and is...

Basic Compounds

The most important and extensively studied pesticides of this group (Fig. 10, Table 3) are Amitrole and several members of the family of s-triazines 89,151, 153,155,156 .Amitrole had been widely used as a herbicide, but its uses as a registered product for application on food crops were canceled starting in 1971 because it was suspected of inducing thyroid tumors in rats 157-162 . Amitrole is soluble in water, with a weak basic character (PKb 10) and behaves chemically as a typical aromatic...

Bioavailability and Reductive Dechlorination

Intrinsic reductive dechlorination of PCBs at sites, where residual petroleum products are often found, is often limited or nonexistent 34 . Both commercial PCBs and petroleum exist in the environment as complex mixtures of structurally related compounds. The compounds comprising these mixtures typically have low water solubilities and high sorption coefficients. At relatively low concentrations in the environment,the constituents of these mixtures partition into soil and sediment organic...

Role of Dissolved Humic Substances in Pollutant Solid Phase Interactions

Dissolved humic substances (DHS) are the main constituents of the dissolved organic carbon (DOC) pool in surface waters (freshwaters and marine waters), groundwaters, and soil porewaters and commonly impart a yellowish-brown color to the water system. Despite the different origins responsible for the main structural characteristics of DHS, they all constitute refractory products of chemical and biological degradation and condensation reactions from plant or animal residues and play a crucial...

Aliphatic Compounds

Diasteranes

Aliphatic hydrocarbons, a diverse suite of compounds, are an important lipid fraction which is either natural (i. e., from photosynthesis by marine biota inhabiting the surface waters or by terrestrial vascular plants) or anthropogenic (i. e., of petroleum origin from land runoff, and or industrial inputs). Aliphatic hydrocarbons have been studied and characterized from various environmental multimedia 1,53-56,99-109 . Aliphatic hydrocarbons of petroleum origin (Fig. 1) (also coal) in the...

Hb Mb b H

The Elovich model was originally developed to describe the kinetics of heterogeneous chemisorption of gases on solid surfaces 117 .It describes a number of reaction mechanisms including bulk and surface diffusion, as well as activation and deactivation of catalytic surfaces. In solid phase chemistry, the Elovich model has been used to describe the kinetics of sorption desorption of various chemicals on solid phases 23 . It can be expressed as 118 (b) ln (c)+(c) ln ( t) (54) - qt the amount of...

CoMetabolism

Partial Oxidation

The transformation of an organic compound by a microorganism that is unable to use the substrate or one of its constituent elements as a source of energy is termed co-metabolism. The active microbial populations thus derive no nutritional benefit from the substrates they co-metabolize. The energy sufficient to sustain growth fully is not acquired even if the conversion is an oxidation and releases energy, and the C, N, S, or P that may be in the molecule is not used as a source of these...

Organotin Compounds

Organotin compounds (Fig. 21) are used worldwide as insecticides, fungicides, bactericides, acaricides, wood preservatives, plastic stabilizers, and antifouling agents 75, 59, 255, 256 and are therefore found in numerous environmental compartments as for example water, sediments, biological tissue, sewage sludge, etc. 257 . Due to their high toxicity for aquatic organisms, the application of tributyltin (TBT) and triphenyltin (TPT) (Fig. 21) as marine antifouling agents Fig. 21. Structures of...

Supercritical Fluid Extraction

The first use of supercritical fluid extraction (SFE) as an extraction technique was reported by Zosel 379 . Since then there have been many reports on the use of SFE to extract PCBs, phenols, PAHs, and other organic compounds from particulate matter, soils and sediments 362, 363, 380-389 . The attraction of SFE as an extraction technique is directly related to the unique properties of the supercritical fluid 390 . Supercritical fluids, which have been used, have low viscosities, high diffusion...

Multicomponent Langmuir Model

The Langmuir model for competitive adsorption can be used as a common model for predicting adsorption equilibria in multicomponent systems. This was first developed by Butler and Ockrent 77 and is based on the same assumptions as the Langmuir model for single adsorbates. It assumes, as in the case of the Langmuir model, that the rate of adsorption of a species at equilibrium is equal to its desorption rate. This is expressed by Eq. (18) where Q and b are the Langmuir constants determined from...

OnLine Coupling of IRMS

The following section provides information about on-line coupling of IRMS to both GC and MS for environmental applications. For work of the highest accuracy and precision using GC coupled to IRMS through a combustion furnace (GC-C-IRMS), on-line isotopic calibration is essential. The standard practice is to introduce pulses of an isotopically standardized gas (e.g., CO2) via an independent inlet directly into the ion source. The disadvantage of this calibration method is that it fails to...

Fragmentation Pattern and Environmental Applications

Hopanes Pattern

The combination of high-resolution capillary columns with fast scanning qua-drupole or magnetic sector mass spectrometers provides an excellent method for the identification of a large proportion of the compounds in complex organic materials (COMs). It is worth mentioning that GC-MS analysis of environmental samples has the added advantage over GC of providing structural information on many unknown components responsible for the chromatographic peaks, as well as components that appear to be...

References

Dissertation. Department of Civil, Construction and Environmental Engineering, Oregon State University, Corvallis, Oregon, USA 2. Ruthven DM 1984 Principles of adsorption and adsorption processes.Wiley, New York, p 445 3. Scheidegger AM, Sparks DL 1996 A critical assessment of sorption-desorption mechanisms at the soil mineral water interface. Soil Science 161 813 4. Schlebaum W, Schraa G, van Riemsdijk WH 1999 Environ Sci Technol 33 1413 5. Schwarzenbach...

Bioremediation Enhancement

There is tremendous interest in using in situ bioremediation for the cleanup of contaminated soil sediment sites and ground waters. However, biodegradation biotransformation rates, especially in the subsurface aqueous-solid phase environment, are often constrained by a limited oxygen supply and by factors related to bioavailability e.g., solubility, dissolution rate, sorption 150, 191, 200 . Recent research has examined the possibility of enhancing the bioavailability of low solubility and...

Verification of Intrinsic Bioremediation

Techniques traditionally used to verify the occurrence of intrinsic bioremedia-tion at contaminated field sites include monitoring indirect indicators of biological activity such as depletion of contaminant and electron acceptors and production of dissolved inorganic carbon DIC 310 or methane CH4 475 , and the enumeration of BTEX-degrading microorganisms 134 . Although determining the geochemical and microbiological characteristics at a specific contaminated location is essential to any...