Chemical Surrogate Research Articles

Evaluation of the measurement of Cu(II) bioavailability in complex aqueous media using a hollow-fiber supported liquid membrane device (HFSLM) and two microalgae species (Pseudokirchneriella subcapitata and Scenedesmus acutus)

The environmental bioavailability of copper was determined using a hollow-fiber supported liquid membrane (HFSLM) device as a chemical surrogate and two microalgae species (Scenedesmus acutus and Pseudokirchneriella subcapitata). Several experimental conditions were studied: pH, the presence of organic matter, inorganic anions, and concomitant cations. The results indicated a strong relationship between the response given by the HFSLM and the microalgae species with free copper concentrations measured by an ion selective electrode (ISE), in accordance with the free-ion activity model (FIAM). A significant positive correlation was evident when comparing the bioavailability results measured by the HFSLM and the S. acutus microalga species, showing that the synthetic device may emulate biological uptake and, consequently, be used as a chemical test for bioavailability measurements using this alga as a biological reference.

A combustion model for multi-component fuels using a physical surrogate group chemistry representation (PSGCR)

A combustion model to simulate the oxidation of multi-component fuels has been developed and applied to model autoignition combustion processes. The model is called the Physical Surrogate Group Chemistry Representation (PSGCR) method, which combines a multi-component fuel model to describe the physical properties of the fuel with reduced reaction mechanisms to represent the chemistry of the fuel components. A group of physical surrogate (PS) components are used to describe the fuel’s physical properties, such as the distillation profile, specific gravity, lower heating value and hydrogen-to-carbon (H/C) ratio. The oxidation processes of the fuel are modeled using skeletal reaction mechanisms for a group of chemical surrogate (CS) components that employ generic reactions as well as detailed reaction kinetics. The generic reactions were built to model unavailable reaction pathways from physical surrogates to the base CS components or their intermediate species. The model includes the 6 major chemical classes of typical hydrocarbon fuels, i.e., n-paraffins, iso-paraffins, olefins, naphthenes, aromatics and oxygenates, and 65 representative hydrocarbon components are included in a data base for the physical surrogate components and 43 chemical surrogate components are considered for the group chemistry representation. Six types of generic reaction sets are proposed to model the oxidation of 15 physical surrogate components that are called extended-CS (chemical surrogate) components. The present generic reactions are modeled such that the major characteristics of the oxidation process of the fuel components are included in a consistent manner.The final version of the PSGCR reaction mechanism consists of 264 species and 1292 reactions. Validation of the reaction mechanisms was performed by comparing predicted ignition delay times with experimental measurements and/or predictions from comprehensive mechanisms available in the literature. The model was also validated against HCCI experimental data of the FACE fuels. Then the model was applied to simulate practical diesel fuel (F76) spray combustion in a constant volume chamber, and the predicted ignition delay times of the surrogate model fuel were compared with measured values. The results show that the present PSGCR method captures the combustion characteristics of complex multi-component fuels, giving reliable performance for combustion predictions, as well as computational efficiency improvements for multi-dimensional CFD simulations through the use of reduced mechanisms.

Competitive incorporation of perrhenate and nitrate into sodalite.

Nuclear waste storage tanks at the Hanford site in southeastern Washington have released highly alkaline solutions, containing radioactive and other contaminants, into subsurface sediments. When this waste reacts with subsurface sediments, feldspathoid minerals (sodalite, cancrinite) can form, sequestering pertechnetate (99TcO4-) and other ions. This study investigates the potential for incorporation of perrhenate (ReO4-), a chemical surrogate for 99TcO4-, into mixed perrhenate/nitrate (ReO4-/NO3-) sodalite. Mixed-anion sodalites were hydrothermally synthesized in the laboratory from zeolite A in sodium hydroxide, nitrate, and perrhenate solutions at 90 °C for 24 h. The resulting solids were characterized by bulk chemical analysis, X-ray diffraction, scanning electron microscopy, and X-ray absorption near edge structure spectroscopy (XANES) to determine the products' chemical composition, structure, morphology, and Re oxidation state. The XANES data indicated that nearly all rhenium (Re) was incorporated as Re(VII)O4-. The nonlinear increase of the unit cell parameter with ReO4-/NO3- ratios suggests formation of two separate sodalite phases in lieu of a mixed-anion sodalite. The results reveal that the sodalite cage is highly selective toward NO3- over ReO4-. Calculated enthalpy and Gibbs free energy of formation at 298 K for NO3- and ReO4-sodalite suggest that NO3- incorporation into the cage is favored over the incorporation of the larger ReO4-, due to the smaller ionic radius of NO3-. Based on these results, it is expected that NO3-, which is present at significantly higher concentrations in alkaline waste solutions than 99TcO4-, will be strongly preferred for incorporation into the sodalite cage.

Carrageenan analysis. Part 3: Quantification in swine plasma

Development and validation of this method was conducted to support a 28-day piglet feeding study of swine-adapted infant formulations stabilised with carrageenan. The validation was performed in accordance with USFDA Good Laboratory Practice (GLP) Regulations and associated current bioanalytical guidelines. Separation of carrageenan from plasma protein was unsuccessful using saturated sodium chloride due to the extremely strong cross-linking interactions between carrageenan and protein. Poligeenan is the deliberately acid-hydrolysed low molecular weight polygalactan non-food product produced from carrageenan. Poligeenan molecules are nearly identical to carrageenan molecules with respect to molecular structure, the primary difference being molecular weight. These poligeenan molecules have similar molecular weight when compared with the lowest molecular weight fraction of carrageenan called the low molecular-weight tail (LMT). Poligeenan was separated from plasma protein using the salting procedure, this being due to the significantly weaker interaction with protein caused by its shorter molecular chain length. Thus, poligeenan was applied as a chemical analyte surrogate for the LMT of carrageenan solely for the development and validation of the method. This method was used to try to detect the LMT of the carrageenan test material during the 28-day piglet feeding study, and if such was absorbed into the bloodstream. Successful development and validation of the method was achieved using LC-MS/MS coupled with ESI in negative-ion mode. A standard curve of instrument response versus poligeenan concentration was developed using swine plasma spiked with a range of poligeenan concentrations. The lower level of quantification (LLOQ) of poligeenan was 10.0 µg ml–1, and the quantification range was 10.0–100.0 µg ml–1. No animals were fed poligeenan.

Experimental determination of the speciation, partitioning, and release of perrhenate as a chemical surrogate for pertechnetate from a sodalite-bearing multiphase ceramic waste form

A key component to closing the nuclear fuel cycle is the storage and disposition of nuclear waste in geologic systems. Multiphase ceramic waste forms have been studied extensively as a potential host matrix for nuclear waste. Understanding the speciation, partitioning, and release behavior of radionuclides immobilized in multiphase ceramic waste forms is a critical aspect of developing the scientific and technical basis for nuclear waste management. In this study, we evaluated a sodalite-bearing multiphase ceramic waste form (i.e., fluidized-bed steam reform sodium aluminosilicate [FBSR NAS] product) as a potential host matrix for long-lived radionuclides, such as technetium (99Tc). The FBSR NAS material consists primarily of nepheline (ideally NaAlSiO4), anion-bearing sodalites (ideally M8[Al6Si6O24]X2, where M refers to alkali and alkaline earth cations and X refers to monovalent anions), and nosean (ideally Na8[AlSiO4]6SO4). Bulk X-ray absorption fine structure analysis of the multiphase ceramic waste form, suggest rhenium (Re) is in the Re(VII) oxidation state and has partitioned to a Re-bearing sodalite phase (most likely a perrhenate sodalite Na8[Al6Si6O24](ReO4)2). Rhenium was added as a chemical surrogate for 99Tc during the FBSR NAS synthesis process. The weathering behavior of the FBSR NAS material was evaluated under hydraulically unsaturated conditions with deionized water at 90°C. The steady-state Al, Na, and Si concentrations suggests the weathering mechanisms are consistent with what has been observed for other aluminosilicate minerals and include a combination of ion exchange, network hydrolysis, and the formation of an enriched-silica surface layer or phase. The steady-state S and Re concentrations are within an order of magnitude of the nosean and perrhenate sodalite solubility, respectively. The order of magnitude difference between the observed and predicted concentration for Re and S may be associated with the fact that the anion-bearing sodalites contained in the multiphase ceramic matrix are present as mixed-anion sodalite phases. These results suggest the multiphase FBSR NAS material may be a viable host matrix for long-lived, highly mobilie radionuclides which is a critical aspect in the management of nuclear waste.

CHEMICAL EFFECTS ON PWR SUMP STRAINER BLOCKAGE AFTER A LOSS-OF-COOLANT ACCIDENT: REVIEW ON U.S. RESEARCH EFFORTS

Industry- or regulatory-sponsored research activities on the resolution of Generic Safety Issue (GSI)-191 were reviewed, especially on the chemical effects. Potential chemical effects on the head loss across the debris-loaded sump strainer under a post-accident condition were experimentally evidenced by small-scale bench tests, integrated chemical effects test (ICET), and vertical loop head loss tests. Three main chemical precipitates were identified by WCAP-16530-NP: calcium phosphate, aluminum oxyhydroxide, and sodium aluminum silicate. The former two precipitates were also identified as major chemical precipitates by the ICETs. The assumption that all released calcium would form precipitates is reasonable. CalSil insulation needs to be minimized especially in a plant using trisodium phosphate buffer. The assumption that all released aluminum would form precipitates appears highly conservative because ICETs and other studies suggest substantial solubility of aluminum at high temperature and inhibition of aluminum corrosion by silicate or phosphate. The industry-proposed chemical surrogates are quite effective in increasing the head loss across the debris-loaded bed and more effective than the prototypical aluminum hydroxide precipitates generated by in-situ aluminum corrosion. There appears to be some unresolved potential issues related to GSI-191 chemical effects as identified in NUREG/CR-6988. The United States Nuclear Regulatory Commission, however, concluded that the implications of these issues are either not generically significant or are appropriately addressed, although several issues associated with downstream in-vessel effects remain.

A new polystyrene-latex-based and EPS-containing synthetic sludge

Since the living microorganisms in activated sludge continuously change, it is difficult to conduct controlled experiments and achieve reproducible results for evaluating sludge characteristics. Synthetic sludge, as a chemical surrogate to activated sludge, could be used to investigate the sludge physicochemical properties, and it is desirable to prepare synthetic sludge with similar structure and properties to real activated sludge to explore the flocculation and settlement processes in activated sludge systems. In this work, a high-strength synthetic sludge was prepared with functional polystyrene latex particles as the framework and extracellular polymeric substances (EPS) to modify its surface. The flocculation and settling characteristics of the microspheres and the prepared synthetic sludge were tested. Compared with other three functional polystyrene latex microspheres, the synthetic sludge prepared with EPS-modified polystyrene latex microspheres showed good settling characteristics and a significantly higher strength. They could be used for studying the physicochemical properties of activated sludge.

C-terminal Dimerization Activates the Nociceptive Transduction Channel Transient Receptor Potential Vanilloid 1

Covalent modification of the specific cysteine residue(s) by oxidative stress robustly potentiates transient receptor potential vanilloid 1 (TRPV1) and sensitizes nociception. Here we provide biochemical evidence of dimerization of TRPV1 subunits upon exposure to phenylarsine oxide and hydrogen peroxide (H(2)O(2)), two chemical surrogates of oxidative stress. A disulfide bond formed between apposing cysteines ligates two C termini, serving as the structural basis of channel sensitization by oxidative covalent C-terminal modification. Systematic cysteine scanning of the C terminus of a cysteineless TRPV1 channel revealed a critical region within which any cysteine introduced phenylarsine oxide activation to mutant TRPV1. Oxidative sensitization persisted even when this region is substituted with a random peptide linker containing a single cysteine. So did insertion of this region to TRPV3, a homolog lacking the corresponding region and resistant to oxidative challenge. These results suggest that the non-conserved linker in the TRPV1 C terminus senses environmental oxidative stress and adjusts channel activity during cumulative oxidative damage by lowering the activation threshold of gating elements shared by TRPV channels.

Biomolecular characterization of allergenic proteins in snow crab (Chionoecetes opilio) and de novo sequencing of the second allergen arginine kinase using tandem mass spectrometry

Snow crab (Chionoecetes opilio) proteins have been recognized as an important source of both food and occupational allergens. While snow crab causes a significant occupational allergy, only one novel allergen has recently been fully characterized. The muscle proteins from snow crab legs were profiled by SDS-PAGE. Several of these proteins were characterized using tandem mass spectrometry. Five proteins were identified; sarcoplasmic Ca-binding (20kDa), arginine kinase (40), troponin (23kDa) and α-actine (42kDa) and smooth endoplasmic reticulum Ca(2+)ATPase (113kDa). Immunoblotting using serum of sixteen allergic patients resulted in strong reactivity with the 40-kDa protein in seven patients (43%). This protein was purified by chromatography and subsequently de novo sequenced using matrix assisted laser desorption ionization and electrospray tandem mass spectrometry. We identified a second important allergen, arginine kinase, in snow crab, designated Chi o 3. Based on identity and homology analysis, using bioinformatics tools, a signature peptide was identified as a chemical surrogate for arginine kinase. The suitability of this signature peptide was tested for analytically representing the arginine kinase, by performing a multi-reaction monitoring tandem mass spectrometry approach on actual air filter samples collected from a simulated crab processing plant.

Chronic administration of membrane sealant prevents severe cardiac injury and ventricular dilatation in dystrophic dogs

Duchenne muscular dystrophy (DMD) is a fatal disease of striated muscle deterioration caused by lack of the cytoskeletal protein dystrophin. Dystrophin deficiency causes muscle membrane instability, skeletal muscle wasting, cardiomyopathy, and heart failure. Advances in palliative respiratory care have increased the incidence of heart disease in DMD patients, for which there is no cure or effective therapy. Here we have shown that chronic infusion of membrane-sealing poloxamer to severely affected dystrophic dogs reduced myocardial fibrosis, blocked increased serum cardiac troponin I (cTnI) and brain type natriuretic peptide (BNP), and fully prevented left-ventricular remodeling. Mechanistically, we observed a markedly greater primary defect of reduced cell compliance in dystrophic canine myocytes than in the mildly affected mdx mouse myocytes, and this was associated with a lack of utrophin upregulation in the dystrophic canine cardiac myocytes. Interestingly, after chronic poloxamer treatment, the poor compliance of isolated canine myocytes remained evident, but this could be restored to normal upon direct application of poloxamer. Collectively, these findings indicate that dystrophin and utrophin are critical to membrane stability-dependent cardiac myocyte mechanical compliance and that poloxamer confers a highly effective membrane-stabilizing chemical surrogate in dystrophin/utrophin deficiency. We propose that membrane sealant therapy is a potential treatment modality for DMD heart disease and possibly other disorders with membrane defect etiologies.

Development of an Analytical Protocol for Forensic Identification of Chemical Warfare Agent Surrogates

An analytical protocol for forensic identification of chemical warfare agent surrogates in various sample media is developed. This protocol can be implemented on site or in a mobile laboratory, based on a quick sample extraction procedure and a subsequent gas chromatography/mass spectrometry (GC/MS) analysis. The surrogates in this work include 2-chloroethyl ethyl sulfide (CEES), dimethyl methyl phosphonate (DMMP), 2-(butylamino) ethanethiol (BAET), pinacolyl methyl phosphonate (PMP), and diethyl phosphoramidate (DEPA) that are simulants of mustard gas, sarin, VX (O-Ethyl S-2-diisopropylaminoethyl methylphosphonothiolate), soman, and tabun, respectively. The target analytes in headspace or air sample are sampled by the solid phase microextraction (SPME) fibers and all surrogates are easily detected by GC/MS analysis. The neat vapor is also directly analyzed by a portable MS through a membrane inlet but only the more volatile CEES and DMMP are detectable and correctly identified. The stability of surrogates in acetone is monitored in the preparation of standard solution. All surrogates are relatively stable in acetone with the exception of BAET, which is found to degrade quickly in water and other organic solvents (e.g., acetone, methanol, ethanol, hexane). Extraction of water and soil samples is also investigated in this study. In analyzing water sample spiked with the surrogates, it is found that SPME does not offer any advantage over direct aqueous injection into the GC/MS. CEES readily hydrolyzes in water to form 2-(ethylthio)-ethanol. Soil samples are extracted by acetone and the raw extracts are analyzed without any concentration, and all surrogates are detectable at 5–10 ppm level for CEES, DMMP, and DEPA. An actual case study is carried out using SPME to detect the presence of surrogate vapor inside a laboratory refrigerator in which they are stored.

Application of Combustion Synthesis to the Production of Actinide Bearing Nitride Ceramic Nuclear Fuels

Self-propagating high temperature (combustion) synthesis (SHS) is being used to develop several synthesis and processing routes for the next generation of ceramic nuclear fuels. These fuels are based on an actinide nitride within an inert matrix. The application of SHS is particularly important in the synthesis of americium (Am) based ceramics; since the rapid heating and cooling cycles used in this process will help to minimize vaporization loss of Am, which is a major problem in synthesizing Am-based ceramics. Manganese, praseodymium, and dysprosium are being used as physical and chemical surrogates for various actinides. Actinide nitride powders produced using auto-ignition combustion synthesis (AICS) are subsequently reacted with zirconium powder using SHS to produce a final fuel pellet. This paper will discuss the research to date on the synthesis of Am-N powders as well as the production of dense Zr-Am-N pellets as a model ceramic fuel system.

Biological tools for the assessment of contaminated land: applied soil ecotoxicology

Abstract. Chemical analysis alone is inadequate for comprehensively assessing the impact of soil pollution on biota. The term bioavailability can only be applied in a context specific to a target biological receptor or a proven chemical surrogate. Integration of biological and chemical data can often yield significant advances in hazard assessment and act as a suitable baseline for making site‐specific risk assessments. Here, the value of biological techniques is discussed and their application described. The relative merit of test selection is considered and the new direction being developed in sublethal assessments. Currently, however, one of the major limitations is the seeming lack of flexibility of many assays in that they are either applicable to agricultural systems or industrial scenarios, but rarely to both. As a consequence, few assays have internationally adopted protocols. The introduction of new methods and the continued improvement and refinement of assays make this area of soil science dynamic and responsive.

Quantifying small molecules in secondary organic aerosol formed during the photo-oxidation of toluene with hydroxyl radicals

The composition of secondary organic aerosol (SOA) formed during the photo-oxidation of toluene in a large-volume smog chamber was determined using direct thermal desorption coupled to comprehensive gas chromatography–time of flight mass spectrometry (TD–GC×GC–TOF/MS). TD–GC×GC eliminated offline sample preparation and resulted in a single shot inventory of GC-amenable organic species within the aerosol. Seventy-four species were identified and quantified from chromatographic retention behaviour and mass spectral fragmentation. Functional groups resolved included organic acids, aromatics, dicarbonyls, furans, furanones, furandiones and pyranones. Concentrations of individual species were derived either directly from standards or from chemical surrogates. The major small organic molecule components by mass were formed via the peroxy-bicyclic reaction mechanism (e.g., 5-methyl-2(3H)-furanone=2972 ng m −3 or 0.861% of aerosol mass), although only around 10% of the total aerosol mass could be quantified. In addition, a large number of lower concentration species were observed with ambiguous chemical characteristics. Interpretation of their mass spectra suggests these species may be fragments of larger molecules broken down during the thermal desorption and separation stages.

Effectiveness of polypropylene film as a barrier to migration from recycled paperboard packaging to fatty and high-moisture food

The capability of a polypropylene (PP) film barrier to prevent migration of residual contaminants from recycled paperboard into food simulants was studied. Anthracene, benzophenone, methyl stearate and pentachlorophenol were chosen as chemical surrogates to represent classes of contaminants likely to be found in recycled paper/paperboard. Each surrogate was spiked into a test specimen made of seven thin virgin paper layers at concentrations of 1–50 mg kg−1. Test specimen were dried, stacked and sandwiched with PP films, laminated with PP film and then subjected to migration experiments using a compression cell maintained at 100°C for 2 h. The concentration of the surrogates in the test specimen and in 95% ethanol, isopropanol and 10% ethanol food-simulating solvents was determined by gas chromatography with flame ionization and electron capture detection. The results show that although the concentrations of the surrogates in the food simulants decreased with an increase in PP film thickness, they were still high and generally resulted in dietary concentrations >0.5 µg kg−l, the level that US Food and Drug Administration would equate with negligible risk for a contaminant migrating from food packaging. Only at the lowest spiking level (1 mg kg−1 benzophenone) did migration from the paperboard through a 0.127-mm PP film result in a dietary concentration of ≤ 0.5 µg kg−1. Therefore, it can be concluded that for an extended time at 100°C, PP would not be an acceptable barrier to migration of contaminants that are expected to be in post-consumer paper/paperboard.

Development of an improved synthetic sludge: a possible surrogate for studying activated sludge dewatering characteristics

Activated sludge is a complex mixture of inert suspended solids, various microorganisms, and extracellular material. Research on the physical characteristics of activated sludge is complicated because the living microorganisms continuously change sludge characteristics, making it almost impossible to carry out controlled experiments or reproduce test results. Therefore, in dewatering, settling and conditioning studies of activated sludge, there is a clear need for an activated sludge surrogate that is chemically well defined, stable, and successfully represents activated sludge properties. One such chemical surrogate, named “synthetic sludge”, suggested by Sanin and Vesilind [Sanin, F. D. and Vesilind, P. A. (1996) Synthetic sludge: a physical/chemical model in understanding bioflocculation. Water Environ. Res. 68 (2), 927–933] is composed of polystyrene latex particles, alginate, and calcium ions. In this sludge the polystyrene latex particles simulate individual bacteria, and alginate simulates extracellular material tied into a matrix with the calcium. However, one important component, something to simulate the filamentous microorganisms, is missing. The lack of filaments in the synthetic sludge causes the flocs to be weaker and smaller than activated sludge flocs. In this study synthetic sludge is improved by adding cellulose fibers to simulate the filamentous microorganisms found in activated sludge. The addition of cellulose results in the formation of strong flocs, improving the dewaterability and settleability of synthetic sludge.

Orphan receptors, novel neuropeptides and reverse pharmaceutical research

By the beginning of the next millennium, the search for the natural ligands of the orphan G-protein-coupled receptors will lead to the discovery of so many new neuropeptides that it may well double their present number. This bounty of new tools will direct us to new insights in brain function and to better understanding of brain disorders. It is expected that the novel neuropeptides will have a particular impact on molecular psychiatry. In view of their potential, the novel neuropeptides should also become the focus of drug discovery programs. It is hoped that these programs will be initiated at an early stage, when understanding of novel neuropeptide function has not necessarily been reached, to allow for the design of neuropeptide chemical surrogates that are crucial to the study of the novel neuropeptide system and may serendipitously develop into highly successful drugs.

The destruction of chemical warfare surrogates and subsequent phosphorus distribution during gasification

The ChemChar process enables gasification of a wide variety of liquid and sludge wastes on a readily handled macroporous granular char. The process produces combustible gas products, largely retains metals and halides on the char matrix, and effectively destroys organohalides without producing SOX, NOX, chlorinated dibenzodioxins or chlorinated dibenzoflirans (which can occur with incineration). To study chemical warfare agent wastes under gasification conditions, the destruction removal efficiencies (DRE) of the chemical warfare surrogates parathion and diethylchlorothiophosphate were determined. DREs of > 99.9996 % and > 99.99998 % were found for parathion and diethylchlorothiophosphate, respectively. Additionally, a study of the distribution of radiolabeled phosphorus (P‐32) after gasification of parathion and tributylphosphate showed essentially complete retention of the phosphorus within the gasification system. This study illustrates that the ChemChar gasification process holds significant promise as an alternative to incineration for the safe and complete destruction of chemical warfare agent wastes.

CRITICAL ELEMENTS IN DESCRIBING AND UNDERSTANDING OUR NATION'S AQUATIC RESOURCES1

ABSTRACT: Despite spending $115 billion per year on environmental actions in the United States, we have only a limited ability to describe the effectiveness of these expenditures. Moreover, after decades of such investments, we cannot accurately describe status and trends in the nation's aquatic ecosystems or even those in specific regions. Why? This situation has arisen in part because we have excluded the fundamental principles of probability designs that are widely used in other fields and we have often ignored direct measures of biota, the subjects of greatest concern. To demonstrate the results of ignoring these powerful statistical and biological tools, we present four case studies. These studies compare estimates of aquatic resource status derived from using (1) a probability‐based study design, often with biological measures of condition; and (2) a nonstatistical study design, often using chemical surrogates. In three of the four cases, the results derived from the nonstatistical perspective underestimate the degree of biological degradation.

Biological Integrity: A Long-Neglected Aspect of Water Resource Management.

Water of sufficient quality and quantity is critical to all life. Increasing human population and growth of technology require human society to devote more and more attention to protection of adequate supplies of water. Although perception of biological degradation stimulated current state and federal legislation on the quality of water resources, that biological focus was lost in the search for easily measured physical and chemical surrogates. The "fishable and swimmable" goal of the Water Pollution Control Act of 1972 (PL 92-500) and its charge to "restore and maintain" biotic integrity illustrate that law's biological underpinning. Further, the need for operational definitions of terms like "biological integrity" and "unreasonable degradation" and for ecologically sound tools to measure divergence from societal goals have increased interest in biological monitoring. Assessment of water resource quality by sampling biological communities in the field (ambient biological monitoring) is a promising approach that requires expanded use of ecological expertise. One such approach, the Index of Biotic Integrity (IBI), provides a broadly based, multiparameter tool for the assessment of biotic integrity in running waters. IBI based on fish community attributes has now been applied widely in North America. The success of IBI has stimulated the development of similar approaches using other aquatic taxa. Expanded use of ecological expertise in ambient biological monitoring is essential to the protection of water resources. Ecologists have the expertise to contribute significantly to those programs.